Effects of spatial variation of skull and cerebrospinal fluid layers on optical mapping of brain activities

NASA Astrophysics Data System (ADS)

Wang, Shuping; Shibahara, Nanae; Kuramashi, Daishi; Okawa, Shinpei; Kakuta, Naoto; Okada, Eiji; Maki, Atsushi; Yamada, Yukio

2010-07-01

In order to investigate the effects of anatomical variation in human heads on the optical mapping of brain activity, we perform simulations of optical mapping by solving the photon diffusion equation for layered-models simulating human heads using the finite element method (FEM). Particularly, the effects of the spatial variations in the thicknesses of the skull and cerebrospinal fluid (CSF) layers on mapping images are investigated. Mapping images of single active regions in the gray matter layer are affected by the spatial variations in the skull and CSF layer thicknesses, although the effects are smaller than those of the positions of the active region relative to the data points. The increase in the skull thickness decreases the sensitivity of the images to active regions, while the increase in the CSF layer thickness increases the sensitivity in general. The images of multiple active regions are also influenced by their positions relative to the data points and by their depths from the skin surface.

Investigation of Electrical and Optical Properties of Highly Transparent TCO/Ag/TCO Multilayer.

PubMed

Kim, Sunbo; Lee, Jaehyeong; Dao, Vinh Ai; Ahn, Shihyun; Hussain, Shahzada Qamar; Park, Jinjoo; Jung, Junhee; Lee, Chan; Song, Bong-Shik; Choi, Byoungdeog; Lee, Youn-Jung; Iftiquar, S M; Yi, Junsin

2015-03-01

Transparent conductive oxides (TCOs) have been widely used as transparent electrodes for opto-electronic devices, such as solar cells, flat-panel displays, and light-emitting diodes, because of their unique characteristics of high optical transmittance and low electrical resistivity. Among various TCO materials, zinc oxide based films have recently received much attention because they have advantages over commonly used indium and tin-based oxide films. Most TCO films, however, exhibit valleys of transmittance in the wavelength range of 550-700 nm, lowering the average transmittance in the visible region and decreasing short-circuit current (Isc) of solar cells. A TCO/Ag/TCO multi-layer structure has emerged as an attractive alternative because it provides optical characteristics without the valley of transmittance compared with a 100-nm-thick single-layer TCO. In this article, we report the electrical, optical and surface properties of TCO/Ag/TCO. These multi-layers were deposited at room temperature with various Ag film thicknesses from 5 to 15 nm while the thickness of TCO thin film was fixed at 40 nm. The TCO/Ag/TCO multi-layer with a 10-nm-thick Ag film showed optimum transmittance in the visible (400-800 nm) wavelength region. These multi-layer structures have advantages over TCO layers of the same thickness.

Analysis of macular and nerve fiber layer thickness in multiple sclerosis patients according to severity level and optic neuritis episodes.

PubMed

Soler García, A; Padilla Parrado, F; Figueroa-Ortiz, L C; González Gómez, A; García-Ben, A; García-Ben, E; García-Campos, J M

2016-01-01

Quantitative assessment of macular and nerve fibre layer thickness in multiple sclerosis patients with regard to expanded disability status scale (EDSS) and presence or absence of previous optic neuritis episodes. We recruited 62 patients with multiple sclerosis (53 relapsing-remitting and 9 secondary progressive) and 12 disease-free controls. All patients underwent an ophthalmological examination, including quantitative analysis of the nerve fibre layer and macular thickness using optical coherence tomography. Patients were classified according to EDSS as A (lower than 1.5), B (between 1.5 and 3.5), and C (above 3.5). Mean nerve fibre layer thickness in control, A, B, and C groups was 103.35±12.62, 99.04±14.35, 93.59±15.41, and 87.36±18.75μm respectively, with statistically significant differences (P<.05). In patients with no history of optic neuritis, history of episodes in the last 3 to 6 months, or history longer than 6 months, mean nerve fibre layer thickness was 99.25±13.71, 93.92±13.30 and 80.07±15.91μm respectively; differences were significant (P<.05). Mean macular thickness in control, A, B, and C groups was 220.01±12.07, 217.78±20.02, 217.68±20.77, and 219.04±24.26μm respectively. Differences were not statistically significant. The mean retinal nerve fibre layer thickness in multiple sclerosis patients is related to the EDSS level. Patients with previous optic neuritis episodes have a thinner retinal nerve fibre layer than patients with no history of these episodes. Mean macular thickness is not correlated to EDSS level. Copyright © 2014 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.

Ta2O5/ Al2O3/ SiO2 - antireflective coating for non-planar optical surfaces by atomic layer deposition

NASA Astrophysics Data System (ADS)

Pfeiffer, K.; Schulz, U.; Tünnermann, A.; Szeghalmi, A.

2017-02-01

Antireflective coatings are essential to improve transmittance of optical elements. Most research and development of AR coatings has been reported on a wide variety of plane optical surfaces; however, antireflection is also necessary on nonplanar optical surfaces. Physical vapor deposition (PVD), a common method for optical coatings, often results in thickness gradients on strongly curved surfaces, leading to a failure of the desired optical function. In this work, optical thin films of tantalum pentoxide, aluminum oxide and silicon dioxide were prepared by atomic layer deposition (ALD), which is based on self-limiting surface reactions. The results demonstrate that ALD optical layers can be deposited on both vertical and horizontal substrate surfaces with uniform thicknesses and the same optical properties. A Ta2O5/Al2O3/ SiO2 multilayer AR coating (400-700 nm) was successfully applied to a curved aspheric glass lens with a diameter of 50 mm and a center thickness of 25 mm.

Structural and optical properties of ZnO nanorods on Mg0.2Zn0.8O seed layers grown by hydrothermal method.

PubMed

Kim, Min Su; Kim, Do Yeob; Kim, Sung-O; Leem, Jae-Young

2013-05-01

ZnO nanorods were grown on the Mg0.2Zn0.8O seed layers with different thickness by hydrothermal method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out to investigate the effects of the Mg0.2Zn0.8O seed layer thickness on the structural and the optical properties of the ZnO nanorods. The residual stress in the Mg0.2Zn0.8O seed layers was depended on the thickness while the texture coefficient of the Mg0.2Zn0.8O seed layers was not affected significantly. The smaller full width at half maximum (FWHM) of the ZnO (002) diffraction and near-band-edge emission (NBE) peak and the larger average grain size were observed from the ZnO nanorods grown on the Mg0.2Zn0.8O seed layers with 5 layers (thickness of 350 nm), which indicate the enhancement the structural and the optical properties of the ZnO nanorods.

Magneto-optical microcavity with Au plasmonic layer

NASA Astrophysics Data System (ADS)

Mikhailova, T. V.; Lyashko, S. D.; Tomilin, S. V.; Karavainikov, A. V.; Prokopov, A. R.; Shaposhnikov, A. N.; Berzhansky, V. N.

2017-11-01

Optical and Faraday rotation spectra of magneto-optical microcavity coated with Au plasmonic layer of gradient thickness were investigated theoretically and experimentally. It was shown that the Tamm plasmon-polaritons mode forms near the long-wavelength edge of photonic band gap. The presence of Au coating of thickness of 90.4 nm increase the Faraday rotation at Tamm plasmon-polaritons and cavity resonances in 1.3 and 7 times, respectively. By transfer matrix method it were found that the incorporation of SiO2 buffer layer with a thickness in the range from 155 to 180 nm between microcavity and Au coating leads to the strong coupling between cavity mode and Tamm plasmon-polaritons. In this case, one or two resonances arise in the vicinity of the cavity mode depending on the thickness of plasmonic layer. The Faraday rotation for coupled mode in twice less than the value of rotation for single cavity mode.

Alterations in Retinal Layer Thickness and Reflectance at Different Stages of Diabetic Retinopathy by En Face Optical Coherence Tomography

PubMed Central

Wanek, Justin; Blair, Norman P.; Chau, Felix Y.; Lim, Jennifer I.; Leiderman, Yannek I.; Shahidi, Mahnaz

2016-01-01

Purpose This article reports a method for en face optical coherence tomography (OCT) imaging and quantitative assessment of alterations in both thickness and reflectance of individual retinal layers at different stages of diabetic retinopathy (DR). Methods High-density OCT raster volume scans were acquired in 29 diabetic subjects divided into no DR (NDR) or non-proliferative DR (NPDR) groups and 22 control subjects (CNTL). A customized image segmentation method identified eight retinal layer interfaces and generated en face thickness maps and reflectance images for nerve fiber layer (NFL), ganglion cell and inner plexiform layers (GCLIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor outer segment layer (OSL), and retinal pigment epithelium (RPE). Mean thickness and intensity values were calculated in nine macular subfields for each retinal layer. Results En face thickness maps and reflectance images of retinal layers in CNTL subjects corresponded to normal retinal anatomy. Total retinal thickness correlated negatively with age in nasal subfields (R ≤−0.31; P ≤ 0.03, N = 51). In NDR subjects, NFL and OPL thickness were decreased (P = 0.05), and ONL thickness was increased (P = 0.04) compared to CNTL. In NPDR subjects, GCLIPL thickness was increased in perifoveal subfields (P < 0.05) and INL intensity was higher in all macular subfields (P = 0.04) compared to CNTL. Conclusions Depth and spatially resolved retinal thickness and reflectance measurements are potential biomarkers for assessment and monitoring of DR. PMID:27409491

A polarization measurement method for the quantification of retardation in optic nerve fiber layer

NASA Astrophysics Data System (ADS)

Fukuma, Yasufumi; Okazaki, Yoshio; Shioiri, Takashi; Iida, Yukio; Kikuta, Hisao; Ohnuma, Kazuhiko

2008-02-01

The thickness measurement of the optic nerve fiber layer is one of the most important evaluations for carrying out glaucoma diagnosis. Because the optic nerve fiber layer has birefringence, the thickness can be measured by illuminating eye optics with circular polarized light and analyzing the elliptical rate of the detected polarized light reflected from the optic nerve fiber layer. In this method, the scattering light from the background and the retardation caused by the cornea disturbs the precise measurement. If the Stokes vector expressing the whole state of polarization can be detected, we can eliminate numerically the influence of the background scattering and of the retardation caused by the cornea. Because the retardation process of the eye optics can be represented by a numerical equation using the retardation matrix of each component and also the nonpolarized background scattering light, it can be calculated by using the Stokes vector. We applied a polarization analysis system that can detect the Stokes vector onto the fundus camera. The polarization analysis system is constructed with a CCD area image sensor, a linear polarizing plate, a micro phase plate array, and a circularly polarized light illumination unit. With this simply constructed system, we can calculate the retardation caused only by the optic nerve fiber layer and it can predict the thickness of the optic nerve fiber layer. We report the method and the results graphically showing the retardation of the optic nerve fiber layer without the retardation of the cornea.

Monte Carlo modeling (MCML) of light propagation in skin layers for detection of fat thickness

NASA Astrophysics Data System (ADS)

Nilubol, Chonnipa; Treerattrakoon, Kiatnida; Mohammed, Waleed S.

2010-05-01

Nowadays, most activities require lesser physical actions, which could ultimately lead to accumulation of excessive body fat. The main roles of body fat are to store energy and acts as various kinds of insulators for the body. The thickness of fat layers can be measured to indicate fat-body weight ratio. Exceeding the body-mass index (BMI) could lead to many illnesses regarding obesity. Consequently, many studies have proposed various principles and techniques to measure the amount of fat within one's body. In this paper, infrared interactance in skin layers is studied for investigation of the influence of fat thickness upon photon travelling pattern in skin tissues using Monte Carlo model (MCML). Photon propagation is numerically simulated in simplified multi-layered tissues. The optical coefficients of each skin layers are accounted for different traveling paths of photons that move through random motion. The thickness of fat layer is varied, and changing in optical parameters is observed. Then the statistically obtained data are computed and analyzed for the effect of the fat layer upon reflection percentage using different wavelengths. The calculations have shown increment in the slope of change of reflection percentage versus fat thickness, when using infrared compare to visible light. This technique can be used to construct a mobile device that is capable of measuring the volume fraction of melanin and blood in the epidermis layer and dermis layer, to calculate for the necessary optical coefficients that would be necessary for measurement of fat thickness.

Robust optical properties of sandwiched lateral composition modulation GaInP structure grown by molecular beam epitaxy

DOE PAGES

Park, Kwangwook; Kang, Seokjin; Ravindran, Sooraj; ...

2016-12-26

Double-hetero structure lateral composition modulated (LCM) GaInP and sandwiched LCM GaInP having the same active layer thickness were grown and their optical properties were compared. Sandwiched LCM GaInP showed robust optical properties due to periodic potential nature of the LCM structure, and the periodicity was undistorted even for thickness far beyond the critical layer thickness. A thick LCM GaInP structure with undistorted potential that could preserve the properties of native LCM structure was possible by stacking thin LCM GaInP structures interspaced with strain compensating GaInP layers. Furthermore, the sandwiched structure could be beneficial in realizing the LCM structure embedded highmore » efficiency solar cells.« less

High efficiency organic photovoltaic cells employing hybridized mixed-planar heterojunctions

DOEpatents

Xue, Jiangeng; Uchida, Soichi; Rand, Barry P; Forrest, Stephen

2013-11-19

A device is provided, having a first electrode, a second electrode, and a photoactive region disposed between the first electrode and the second electrode. The photoactive region includes a first organic layer comprising a mixture of an organic acceptor material and an organic donor material, wherein the first organic layer has a thickness not greater than 0.8 characteristic charge transport lengths, and a second organic layer in direct contact with the first organic layer, wherein: the second organic layer comprises an unmixed layer of the organic acceptor material or the organic donor material of the first organic layer, and the second organic layer has a thickness not less than about 0.1 optical absorption lengths. Preferably, the first organic layer has a thickness not greater than 0.3 characteristic charge transport lengths. Preferably, the second organic layer has a thickness of not less than about 0.2 optical absorption lengths. Embodiments of the invention can be capable of power efficiencies of 2% or greater, and preferably 5% or greater.

The Effects of an Absorbing Smoke Layer on MODIS Marine Boundary Layer Cloud Optical Property Retrievals and Radiative Forcing

NASA Technical Reports Server (NTRS)

Meyer, Kerry; Platnick, Steven

2012-01-01

Clouds, aerosols, and their interactions are widely considered to be key uncertainty components in our current understanding of the Earth's atmosphere and radiation budget. The work presented here is focused on the quasi-permanent marine boundary layer . (MBL) clouds off the southern Atlantic coast of Africa and the effects on MODIS cloud optical property retrievals (MOD06) of an overlying absorbing smoke layer. During much of August and September, a persistent smoke layer resides over this region, produced from extensive biomass burning throughout the southern African savanna. The resulting absorption, which increases with decreasing wavelength, potentially introduces biases into the MODIS cloud optical property retrievals of the underlying MBL clouds. This effect is more pronounced in the cloud optical thickness retrievals, which over ocean are derived from the wavelength channel centered near 0.86 micron (effective particle size retrievals are derived from the longer-wavelength near-IR channels at 1.6, 2.1, and 3.7 microns). Here, the spatial distributions of the scalar statistics of both the cloud and aerosol layers are first determined from the CALIOP 5 km layer products. Next, the MOD06 look-up tables (LUTs) are adjusted by inserting an absorbing smoke layer of varying optical thickness over the cloud. Retrievals are subsequently performed for a subset of MODIS pixels collocated with the CALIOP ground track, using smoke optical thickness from the CALIOP 5km aerosol layer product to select the appropriate LUT. The resulting differences in cloud optical property retrievals due to the inclusion of the smoke layer in the LUTs will be examined. In addition, the direct radiative forcing of this smoke layer will be investigated from the perspective of the cloud optical property retrieval differences.

Gender variations in the optical properties of skin in murine animal models

NASA Astrophysics Data System (ADS)

Calabro, Katherine; Curtis, Allison; Galarneau, Jean-Rene; Krucker, Thomas; Bigio, Irving J.

2011-01-01

Gender is identified as a significant source of variation in optical reflectance measurements on mouse skin, with variation in the thickness of the dermal layer being the key explanatory variable. For three different mouse strains, the thickness values of the epidermis, dermis, and hypodermis layers, as measured by histology, are correlated to optical reflectance measurements collected with elastic scattering spectroscopy (ESS). In all three strains, males are found to have up to a 50% increase in dermal thickness, resulting in increases of up to 80% in reflectance values and higher observed scattering coefficients, as compared to females. Collagen in the dermis is identified as the primary source of these differences due to its strong scattering nature; increased dermal thickness leads to a greater photon path length through the collagen, as compared to other layers, resulting in a larger scattering signal. A related increase in the observed absorption coefficient in females is also observed. These results emphasize the importance of considering gender during experimental design in studies that involve photon interaction with mouse skin. The results also elucidate the significant impact that relatively small thickness changes can have on observed optical measurements in layered tissue.

Optical and structural characteristics of high indium content InGaN/GaN multi-quantum wells with varying GaN cap layer thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, J.; Zhao, D. G., E-mail: dgzhao@red.semi.ac.cn; Jiang, D. S.

2015-02-07

The optical and structural properties of InGaN/GaN multi-quantum wells (MQWs) with different thicknesses of low temperature grown GaN cap layers are investigated. It is found that the MQW emission energy red-shifts and the peak intensity decreases with increasing GaN cap layer thickness, which may be partly caused by increased floating indium atoms accumulated at quantum well (QW) surface. They will result in the increased interface roughness, higher defect density, and even lead to a thermal degradation of QW layers. An extra growth interruption introduced before the growth of GaN cap layer can help with evaporating the floating indium atoms, andmore » therefore is an effective method to improve the optical properties of high indium content InGaN/GaN MQWs.« less

In vivo thickness and birefringence determination of the human retinal nerve fiber layer using polarization-sensitive optical coherence tomography.

PubMed

Cense, B; Chen, T C; de Boer, J F

2006-01-01

Thinning of the retinal nerve fiber layer and changes in retinal nerve fiber layer birefringence may both precede clinically detectable glaucomatous vision loss. We present in vivo thickness and depth-resolved birefringence measurements of the human retinal nerve fiber layer (RNFL) by use of polarization-sensitive optical coherence tomography (PS-OCT). Using a fiber-based PS-OCT setup real-time images of the human retina in vivo were recorded, co-registered with retinal video images of the location of PS-OCT scans. PS-OCT scans around the optic nerve head (ONH) of two healthy young volunteers were made using 10 concentric circles of increasing radius. Both the mean retinal nerve fiber layer thickness and mean retinal nerve fiber birefringence for each of 48 sectors on a circle were determined. The retinal nerve fiber layer thickness and birefringence varied as a function of sector around the ONH. Measured double pass phase retardation per unit depth values around the ONH range between 0.10 and 0.35 degrees/microm. The retinal nerve fiber layer becomes thinner with increasing distance from the ONH. In contrast, the birefringence does not vary significantly with increasing distance from the ONH.

Cloud Thickness from Offbeam Returns (THOR) Validation Campaign on NASA's P3B Over the ARM/SGP

NASA Technical Reports Server (NTRS)

Cahalan, R. F.; Kolasinski, J.; McGill, M.; Lau, William K. M. (Technical Monitor)

2002-01-01

Physical thickness of a cloud layer, sometimes multiple cloud layers, is a crucial controller of solar heating of the Earth- atmosphere system, which drives the convective processes that produce storm systems. Yet clouds of average optical thickness are opaque to conventional lidar, so their thickness is well estimated only by combining a lidar above and another below cloud, or a radar and lidar on the same side, dual facilities not widely available. Here we report initial observations of a new airborne multiple field of view lidar, capable of determining physical thickness of cloud layers from time signatures of off-beam returns from a I kHz micropulse lidar at 540 rim. For a single layer, the time delay of light returning from the outer diffuse halo of light surrounding the beam entry point, relative to the time delay at beam center, determines the cloud physical thickness. The delay combined with the pulse stretch gives the optical thickness. This halo method requires cloud optical thickness exceeding 2, and improves with cloud thickness, thus complimenting conventional lidar, which cannot penetrate thick clouds. Results are presented from March 25, 2002, when THOR flew a butterfly pattern over the ARM site at 8.3 km, above a thin ice cloud at 5 km, and a thick boundary-layer stratus deck with top at 1.3 km, as shown by THOR channel 1, and a base at about 0.3 km as shown by the ground-based MPL. Additional information is included in the original extended abstract.

Simple approach for high-contrast optical imaging and characterization of graphene-based sheets.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, I.; Pelton, M.; Piner, R.

2007-12-01

A simple optical method is presented for identifying and measuring the effective optical properties of nanometer-thick, graphene-based materials, based on the use of substrates consisting of a thin dielectric layer on silicon. High contrast between the graphene-based materials and the substrate is obtained by choosing appropriate optical properties and thickness of the dielectric layer. The effective refractive index and optical absorption coefficient of graphene oxide, thermally reduced graphene oxide, and graphene are obtained by comparing the predicted and measured contrasts.

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes.

PubMed

El Beltagi, Tarek A; Bowd, Christopher; Boden, Catherine; Amini, Payam; Sample, Pamela A; Zangwill, Linda M; Weinreb, Robert N

2003-11-01

To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. Retrospective observational case series. Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >-8 dB were included. Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography-measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (R(2)). The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (R(2)) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (R(2) range, 0.34-0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (R(2) = 0.01). Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.

Multilayer Dielectric Transmissive Optical Phase Modulator

NASA Technical Reports Server (NTRS)

Keys, Andrew Scott; Fork, Richard Lynn

2004-01-01

A multilayer dielectric device has been fabricated as a prototype of a low-loss, low-distortion, transmissive optical phase modulator that would provide as much as a full cycle of phase change for all frequency components of a transmitted optical pulse over a frequency band as wide as 6.3 THz. Arrays of devices like this one could be an alternative to the arrays of mechanically actuated phase-control optics (adaptive optics) that have heretofore been used to correct for wave-front distortions in highly precise optical systems. Potential applications for these high-speed wave-front-control arrays of devices include agile beam steering, optical communications, optical metrology, optical tracking and targeting, directional optical ranging, and interferometric astronomy. The device concept is based on the same principle as that of band-pass interference filters made of multiple dielectric layers with fractional-wavelength thicknesses, except that here there is an additional focus on obtaining the desired spectral phase profile in addition to the device s spectral transmission profile. The device includes a GaAs substrate, on which there is deposited a stack of GaAs layers alternating with AlAs layers, amounting to a total of 91 layers. The design thicknesses of the layers range from 10 nm to greater than 1 micrometer. The number of layers and the thickness of each layer were chosen in a computational optimization process in which the wavelength dependences of the indices of refraction of GaAs and AlAs were taken into account as the design was iterated to maximize the transmission and minimize the group-velocity dispersion for a wavelength band wide enough to include all significant spectral components of the pulsed optical signal to be phase modulated.

Internal retinal layer thickness and macular migration after internal limiting membrane peeling in macular hole surgery.

PubMed

Faria, Mun Y; Ferreira, Nuno P; Mano, Sofia; Cristóvao, Diana M; Sousa, David C; Monteiro-Grillo, Manuel E

2018-05-01

To provide a spectral-domain optical coherence tomography (SD-OCT)-based analysis of retinal layers thickness and nasal displacement of closed macular hole after internal limiting membrane peeling in macular hole surgery. In this nonrandomized prospective interventional study, 36 eyes of 32 patients were subjected to pars plana vitrectomy and 3.5 mm diameter internal limiting membrane (ILM) peeling for idiopathic macular hole (IMH). Nasal and temporal internal retinal layer thickness were assessed with SD-OCT. Each scan included optic disc border so that distance between optic disc border and fovea were measured. Thirty-six eyes had a successful surgery with macular hole closure. Total nasal retinal thickening (p<0.001) and total temporal retinal thinning (p<0.0001) were observed. Outer retinal layers increased thickness after surgery (nasal p<0.05 and temporal p<0.01). Middle part of inner retinal layers (mIRL) had nasal thickening (p<0.001) and temporal thinning (p<0.05). The mIRL was obtained by deducting ganglion cell layer (GCL) and retinal nerve fiber layer (RNFL) thickness from overall thickness of the inner retinal layer. Papillofoveal distance was shorter after ILM peeling in macular hole surgery (3,651 ± 323 μm preoperatively and 3,361 ± 279 μm at 6 months; p<0.0001). Internal limiting membrane peel is associated with important alteration in inner retinal layer architecture, with thickening of mIRL and shortening of papillofoveal distance. These factors may contribute to recovery of disrupted foveal photoreceptor and vision improvement after IMH closure.

Changes in Macular Retinal Layers and Peripapillary Nerve Fiber Layer Thickness after 577-nm Pattern Scanning Laser in Patients with Diabetic Retinopathy

PubMed Central

Shin, Ji Soo

2017-01-01

Purpose The aim of this study was to evaluate the changes in thickness of each macular retinal layer, the peripapillary retinal nerve fiber layer (RNFL), and central macular thickness (CMT) after 577-nm pattern scanning laser (PASCAL) photocoagulation in patients with diabetic retinopathy. Methods This retrospective study included 33 eyes with diabetic retinopathy that underwent 577-nm PASCAL photocoagulation. Each retinal layer thickness, peripapillary RNFL thickness, and CMT were measured by spectral-domain optical coherence tomography before 577-nm PASCAL photocoagulation, as well as at 1, 6, and 12 months after 577-nm PASCAL photocoagulation. Computerized intraretinal segmentation of optical coherence tomography was performed to identify the thickness of each retinal layer. Results The average thickness of the RNFL, ganglion cell layer, inner plexiform layer, inner nuclear layer, inner retinal layer, and CMT at each follow-up increased significantly from baseline (p < 0.001), whereas that of the retinal pigment epithelium at each follow-up decreased significantly from baseline (p < 0.001). The average thickness of the peripapillary RNFL increased significantly at one month (p < 0.001). This thickness subsequently recovered to 7.48 µm, and there were no significant changes at six or 12 months compared to baseline (p > 0.05). Conclusions Each macular retinal layer and CMT had a tendency to increase for one year after 577-nm PASCAL photocoagulation, whereas the average thickness of retinal pigment epithelium decreased at one-year follow-up compared to the baseline. Although an increase in peripapillary RNFL thickness was observed one month after 577-nm PASCAL photocoagulation, there were no significant changes at the one-year follow-up compared to the baseline. PMID:29022292

Changes in Macular Retinal Layers and Peripapillary Nerve Fiber Layer Thickness after 577-nm Pattern Scanning Laser in Patients with Diabetic Retinopathy.

PubMed

Shin, Ji Soo; Lee, Young Hoon

2017-12-01

The aim of this study was to evaluate the changes in thickness of each macular retinal layer, the peripapillary retinal nerve fiber layer (RNFL), and central macular thickness (CMT) after 577-nm pattern scanning laser (PASCAL) photocoagulation in patients with diabetic retinopathy. This retrospective study included 33 eyes with diabetic retinopathy that underwent 577-nm PASCAL photocoagulation. Each retinal layer thickness, peripapillary RNFL thickness, and CMT were measured by spectral-domain optical coherence tomography before 577-nm PASCAL photocoagulation, as well as at 1, 6, and 12 months after 577-nm PASCAL photocoagulation. Computerized intraretinal segmentation of optical coherence tomography was performed to identify the thickness of each retinal layer. The average thickness of the RNFL, ganglion cell layer, inner plexiform layer, inner nuclear layer, inner retinal layer, and CMT at each follow-up increased significantly from baseline (p < 0.001), whereas that of the retinal pigment epithelium at each follow-up decreased significantly from baseline (p < 0.001). The average thickness of the peripapillary RNFL increased significantly at one month (p < 0.001). This thickness subsequently recovered to 7.48 μm, and there were no significant changes at six or 12 months compared to baseline (p > 0.05). Each macular retinal layer and CMT had a tendency to increase for one year after 577-nm PASCAL photocoagulation, whereas the average thickness of retinal pigment epithelium decreased at one-year follow-up compared to the baseline. Although an increase in peripapillary RNFL thickness was observed one month after 577-nm PASCAL photocoagulation, there were no significant changes at the one-year follow-up compared to the baseline. © 2017 The Korean Ophthalmological Society

Dependence of the Carrier Transport Characteristics on the Buried Layer Thickness in Ambipolar Double-Layer Organic Field-Effect Transistors Investigated by Electrical and Optical Measurements

NASA Astrophysics Data System (ADS)

Zhang, Le; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2013-05-01

By using current-voltage (I-V) measurements and optical modulation spectroscopy, we investigated the dependence of the carrier behaviour on the film thickness of the buried pentacene layer in C60/pentacene ambipolar double-layer organic field-effect transistors (OFETs). It was found that the buried pentacene layer not only acted as a hole transport layer, but also accounted for the properties of the C60/pentacene interface. The hole and electron behaviour exhibited different thickness dependence on the buried pentacene layer, implying the presence of the spatially separated conduction paths. It was suggested that the injected holes transported along the pentacene/gate dielectric interface, which were little affected by the buried pentacene layer thickness or the upper C60 layer; while, the injected electrons accumulated at the C60/pentacene interface, which were sensitive to the interfacial conditions or the buried pentacene layer. Furthermore, it was suggested that the enhanced surface roughness of the buried pentacene layer was responsible for the observed electron behaviour, especially when dpent>10 nm.

Thickness dependent charge transfer states and dark carriers density in vacuum deposited small molecule organic photocell

NASA Astrophysics Data System (ADS)

Shekhar, Himanshu; Tzabari, Lior; Solomeshch, Olga; Tessler, Nir

2016-10-01

We have investigated the influence of the active layer thickness on the balance of the internal mechanisms affecting the efficiency of copper phthalocyanine - fullerene (C60) based vacuum deposited bulk heterojunction organic photocell. We fabricated a range of devices for which we varied the thickness of the active layer from 40 to 120 nm and assessed their performance using optical and electrical characterization techniques. As reported previously for phthalocyanine:C60, the performance of the device is highly dependent on the active layer thickness and of all the thicknesses we tried, the 40 nm thin active layer device showed the best solar cell characteristic parameters. Using the transfer matrix based optical model, which includes interference effects, we calculated the optical power absorbed in the active layers for the entire absorption band, and we found that this cannot explain the trend with thickness. Measurement of the cell quantum efficiency as a function of light intensity showed that the relative weight of the device internal processes changes when going from 40 nm to 120 nm thick active layer. Electrical modeling of the device, which takes different internal processes into account, allowed to quantify the changes in the processes affecting the generation - recombination balance. Sub gap external quantum efficiency and morphological analysis of the surface of the films agree with the model's result. We found that as the thickness grows the density of charge transfer states and of dark carriers goes up and the uniformity in the vertical direction is reduced.

Optical interference probe of biofilm hydrology: label-free characterization of the dynamic hydration behavior of native biofilms

NASA Astrophysics Data System (ADS)

McDonough, Richard T.; Zheng, Hewen; Alila, Mercy A.; Goodisman, Jerry; Chaiken, Joseph

2017-03-01

Biofilm produced by Escherichia coli (E. coli) or Pseudomonas aeruginosa (P. aeruginosa) on quartz or polystyrene is removed from the culture medium and drained. Observed optical interference fringes indicate the presence of a layer of uniform thickness with refractive index different from air-dried biofilm. Fringe wavelengths indicate that layer optical thickness is <20 μm or 1 to 2 orders of magnitude thinner than the biofilm as measured by confocal Raman microscopy or fluorescence imaging of the bacteria. Raman shows that films have an alginate-like carbohydrate composition. Fringe amplitudes indicate that the refractive index of the interfering layer is higher than dry alginate. Drying and rehydration nondestructively thins and restores the interfering layer. The strength of the 1451-nm near infrared water absorption varies in unison with thickness. Absorption and layer thickness are proportional for films with different bacteria, substrates, and growth conditions. Formation of the interfering layer is general, possibly depending more on the chemical nature of alginate-like materials than bacterial processes. Films grown during the exponential growth phase produce no observable interference fringes, indicating requirements for layer formation are not met, possibly reflecting bacterial activities at that stage. The interfering layer might provide a protective environment for bacteria when water is scarce.

Ratiometric analysis of in vivo retinal layer thicknesses in multiple sclerosis

NASA Astrophysics Data System (ADS)

Bhaduri, Basanta; Nolan, Ryan M.; Shelton, Ryan L.; Pilutti, Lara A.; Motl, Robert W.; Boppart, Stephen A.

2016-09-01

We performed ratiometric analysis of retinal optical coherence tomography images for the first time in multiple sclerosis (MS) patients. The ratiometric analysis identified differences in several retinal layer thickness ratios in the cohort of MS subjects without a history of optic neuritis (ON) compared to healthy control (HC) subjects, and there was no difference in standard retinal nerve fiber layer thickness (RNFLT). The difference in such ratios between HC subjects and those with mild MS-disability, without a difference in RNFLT, further suggests the possibility of using layer ratiometric analysis for detecting early retinal changes in MS. Ratiometric analysis may be useful and potentially more sensitive for detecting disease changes in MS.

THICKNESS OF THE MACULA, RETINAL NERVE FIBER LAYER, AND GANGLION CELL-INNER PLEXIFORM LAYER IN THE AGE-RELATED MACULAR DEGENERATION: The Repeatability Study of Spectral Domain Optical Coherence Tomography.

PubMed

Shin, Il-Hwan; Lee, Woo-Hyuk; Lee, Jong-Joo; Jo, Young-Joon; Kim, Jung-Yeul

2018-02-01

To determine the repeatability of measuring the thickness of the central macula, retinal nerve fiber layer, and ganglion cell-inner plexiform layer (GC-IPL) using spectral domain optical coherence tomography (Cirrus HD-OCT) in eyes with age-related macular degeneration. One hundred and thirty-four eyes were included. The measurement repeatability was assessed by an experienced examiner who performed two consecutive measurements using a 512 × 128 macular cube scan and a 200 × 200 optic disk cube scan. To assess changes in macular morphology in patients with age-related macular degeneration, the patients were divided into the following three groups according to the central macular thickness (CMT): A group, CMT < 200 μm; B group, 200 μm ≤ CMT < 300 μm; and C group, CMT > 300 μm. Measurement repeatability was assessed using test-retest variability, a coefficient of variation, and an intraclass correlation coefficient. The mean measurement repeatability for the central macular, retinal nerve fiber layer, and GC-IPL thickness was high in the B group. The mean measurement repeatability for both the central macula and retinal nerve fiber layer thickness was high in the A and C groups, but was lower for the GC-IPL thickness. The measurement repeatability for GC-IPL thickness was high in the B group, but low in the A group and in the C group. The automated measurement repeatability for GC-IPL thickness was significantly lower in patients with age-related macular degeneration with out of normal CMT range. The effect of changes in macular morphology should be considered when analyzing GC-IPL thicknesses in a variety of ocular diseases.

Diagnostic power of optic disc morphology, peripapillary retinal nerve fiber layer thickness, and macular inner retinal layer thickness in glaucoma diagnosis with fourier-domain optical coherence tomography.

PubMed

Huang, Jehn-Yu; Pekmezci, Melike; Mesiwala, Nisreen; Kao, Andrew; Lin, Shan

2011-02-01

To evaluate the capability of the optic disc, peripapillary retinal nerve fiber layer (P-RNFL), macular inner retinal layer (M-IRL) parameters, and their combination obtained by Fourier-domain optical coherent tomography (OCT) in differentiating a glaucoma suspect from perimetric glaucoma. Two hundred and twenty eyes from 220 patients were enrolled in this study. The optic disc morphology, P-RNFL, and M-IRL were assessed by the Fourier-domain OCT (RTVue OCT, Model RT100, Optovue, Fremont, CA). A linear discriminant function was generated by stepwise linear discriminant analysis on the basis of OCT parameters and demographic factors. The diagnostic power of these parameters was evaluated with receiver operating characteristic (ROC) curve analysis. The diagnostic power in the clinically relevant range (specificity ≥ 80%) was presented as the partial area under the ROC curve (partial AROC). The individual OCT parameter with the largest AROC and partial AROC in the high specificity (≥ 80%) range were cup/disc vertical ratio (AROC = 0.854 and partial AROC = 0.142) for the optic disc parameters, average thickness (AROC = 0.919 and partial AROC = 0.147) for P-RNFL parameters, inferior hemisphere thickness (AROC = 0.871 and partial AROC = 0.138) for M-IRL parameters, respectively. The linear discriminant function further enhanced the ability in detecting perimetric glaucoma (AROC = 0.970 and partial AROC = 0.172). Average P-RNFL thickness is the optimal individual OCT parameter to detect perimetric glaucoma. Simultaneous evaluation on disc morphology, P-RNFL, and M-IRL thickness can improve the diagnostic accuracy in diagnosing glaucoma.

The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals

PubMed Central

Mudd, G. W.; Molas, M. R.; Chen, X.; Zólyomi, V.; Nogajewski, K.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.; Yusa, G.; Makarovsky, O.; Eaves, L.; Potemski, M.; Fal’ko, V. I.; Patanè, A.

2016-01-01

The electronic band structure of van der Waals (vdW) layered crystals has properties that depend on the composition, thickness and stacking of the component layers. Here we use density functional theory and high field magneto-optics to investigate the metal chalcogenide InSe, a recent addition to the family of vdW layered crystals, which transforms from a direct to an indirect band gap semiconductor as the number of layers is reduced. We investigate this direct-to-indirect bandgap crossover, demonstrate a highly tuneable optical response from the near infrared to the visible spectrum with decreasing layer thickness down to 2 layers, and report quantum dot-like optical emissions distributed over a wide range of energy. Our analysis also indicates that electron and exciton effective masses are weakly dependent on the layer thickness and are significantly smaller than in other vdW crystals. These properties are unprecedented within the large family of vdW crystals and demonstrate the potential of InSe for electronic and photonic technologies. PMID:28008964

The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals.

PubMed

Mudd, G W; Molas, M R; Chen, X; Zólyomi, V; Nogajewski, K; Kudrynskyi, Z R; Kovalyuk, Z D; Yusa, G; Makarovsky, O; Eaves, L; Potemski, M; Fal'ko, V I; Patanè, A

2016-12-23

The electronic band structure of van der Waals (vdW) layered crystals has properties that depend on the composition, thickness and stacking of the component layers. Here we use density functional theory and high field magneto-optics to investigate the metal chalcogenide InSe, a recent addition to the family of vdW layered crystals, which transforms from a direct to an indirect band gap semiconductor as the number of layers is reduced. We investigate this direct-to-indirect bandgap crossover, demonstrate a highly tuneable optical response from the near infrared to the visible spectrum with decreasing layer thickness down to 2 layers, and report quantum dot-like optical emissions distributed over a wide range of energy. Our analysis also indicates that electron and exciton effective masses are weakly dependent on the layer thickness and are significantly smaller than in other vdW crystals. These properties are unprecedented within the large family of vdW crystals and demonstrate the potential of InSe for electronic and photonic technologies.

Impact of non-integer planetary revolutions on the distribution of evaporated optical coatings

DOE PAGES

Oliver, J. B.

2017-02-08

Planetary substrate rotation for optical-coating deposition is evaluated based on initial and final positions for a given layer with different numbers of revolutions and various deposition-source locations. The influence of partial revolutions of the rotation system is analyzed relative to the total number of planetary revolutions in that layer to determine the relative impact on film thickness and uniformity. Furthermore, guidance is provided on the necessary planetary revolutions that should take place in each layer versus the expected error level in the layer thickness for the modeled system.

Ganglion cell-inner plexiform layer and retinal nerve fibre layer changes within the macula in retinitis pigmentosa: a spectral domain optical coherence tomography study.

PubMed

Yoon, Chang Ki; Yu, Hyeong Gon

2018-03-01

To investigate how macular ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) thicknesses within the macula change with retinitis pigmentosa (RP) severity. Spectral domain optical coherence tomography (SD-OCT) was used to examine 177 patients with RP and 177 normal controls. An optical coherence tomography (OCT) line scan was used to grade RP severity. Retinitis pigmentosa (RP) was categorized as more advanced if there was no identifiable inner segment ellipsoid (ISe) band (NISE) and as less advanced if an ISe band could be identified and peripheral loss of ISe was apparent (IISE). Ganglion cell-inner plexiform layer (GCIPL) and RNFL thicknesses were manually measured on OCT images and analysed. Pearson's correlation analyses were used to examine correlations between GCIPL thickness, RNFL thickness, visual acuity (VA) and visual field extent in patients and controls. Ganglion cell-inner plexiform layer (GCIPL) was significantly thicker in IISE than in control eyes (p < 0.001), but significantly thinner in NISE than in IISE eyes (p < 0.001) in both horizontal and vertical OCT scans. Retinal nerve fibre layer (RNFL) was significantly thicker in eyes with IISE and NISE than in control eyes in both horizontal and vertical meridians (all p < 0.001). Ganglion cell-inner plexiform layer (GCIPL) thickness showed a weak positive correlation with vision, and RNFL thickness showed a weak negative correlation with vision and visual field extent. Based on these results, the inner retina, including the GCIPL and RNFL, maintains its gross integrity longer than the photoreceptor layer in RP. Additionally, thickening of the inner retina may have some functional implications in patients with RP. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Multiple sclerosis and optic nerve: an analysis of retinal nerve fiber layer thickness and color Doppler imaging parameters

PubMed Central

Akçam, H T; Capraz, I Y; Aktas, Z; Batur Caglayan, H Z; Ozhan Oktar, S; Hasanreisoglu, M; Irkec, C

2014-01-01

Purpose To compare both retinal nerve fiber layer thickness and orbital color Doppler ultrasonography parameters in patients with multiple sclerosis (MS) versus healthy controls. Methods This is an observational case–control study. Forty eyes from MS patients and twenty eyes from healthy volunteers were examined. Eyes were classified into three groups as group 1, eyes from MS patients with previous optic neuritis (n=20); group 2, eyes from MS patients without previous optic neuritis (n=20); and group 3, eyes from healthy controls (n=20). Following complete ophthalmologic examination and retinal nerve fiber layer thickness measurement for each group, blood flow velocities of posterior ciliary arteries, central retinal artery, ophthalmic artery, and superior ophthalmic vein were measured. Pourcelot index (resistive index), an indicator of peripheral vascular resistance, was also calculated. The statistical assessment was performed with the assistance of Pearson's Chi-square test, Mann–Whitney U-test, Kruskal–Wallis test, and Spearman's correlation test. Results The studied eyes exposed similar values in terms of intraocular pressure and central corneal thickness, implying no evidence in favor of glaucoma. All nerve fiber layer thickness values, except superior nasal quadrants, in group 1 were found to be significantly thinner than groups 2 and 3. Blood flow velocity and mean resistivity index parameters were similar in all the groups. Conclusions In MS patients, especially with previous optic neuritis, diminished retinal nerve fiber layer thickness was observed. Contrary to several studies in the current literature, no evidence supporting potential vascular origin of ocular involvement in MS was found. PMID:25081285

Controlling the optical parameters of self-assembled silver films with wetting layers and annealing

NASA Astrophysics Data System (ADS)

Ciesielski, Arkadiusz; Skowronski, Lukasz; Trzcinski, Marek; Szoplik, Tomasz

2017-11-01

We investigated the influence of presence of Ni and Ge wetting layers as well as annealing on the permittivity of Ag films with thicknesses of 20, 35 and 65 nm. Most of the research on thin silver films deals with very small (<20 nm) or relatively large (≥50 nm) thicknesses. We studied the transition region (around 30 nm) from charge percolation pathways to fully continuous films and compared the values of optical parameters among silver layers with at least one fixed attribute (thickness, wetting and capping material, post-process annealing). Our study, based on atomic force microscopy, ellipsometric and X-ray photoelectron spectroscopy measurements, shows that utilizing a wetting layer is comparable to increasing the thickness of the silver film. Both operations decrease the roughness-to-thickness ratio, thus decreasing the scattering losses and both narrow the Lorentz-shaped interband transition peak. However, while increasing silver thickness increases absorption on the free carriers, the use of wetting layers influences the self-assembled internal structure of silver films in such a way, that the free carrier absorption decreases. Wetting layers also introduce additional contributions from effects like segregation or diffusion, which evolve in time and due to annealing.

Optical contrast for identifying the thickness of two-dimensional materials

NASA Astrophysics Data System (ADS)

Bing, Dan; Wang, Yingying; Bai, Jing; Du, Ruxia; Wu, Guoqing; Liu, Liyan

2018-01-01

One of the most intriguing properties of two-dimensional (2D) materials is their thickness dependent properties. A quick and precise technique to identify the layer number of 2D materials is therefore highly desirable. In this review, we will introduce the basic principle of using optical contrast to determine the thickness of 2D material and also its advantage as compared to other modern techniques. Different 2D materials, including graphene, graphene oxide, transitional metal dichalcogenides, black phosphorus, boron nitride, have been used as examples to demonstrate the capability of optical contrast methods. A simple and more efficient optical contrast image technique is also emphasized, which is suitable for quick and large-scale thickness identification. We have also discussed the factors that could affect the experimental results of optical contrast, including incident light angle, anisotropic nature of materials, and also the twisted angle between 2D layers. Finally, we give perspectives on future development of optical contrast methods for the study and application of 2D materials.

Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

PubMed Central

Ali, Rizwan; Saleem, Muhammad Rizwan; Pääkkönen, Pertti; Honkanen, Seppo

2015-01-01

We investigate the optical and thermo-optical properties of amorphous TiO2–Al2O3 thin-film bilayers fabricated by atomic layer deposition (ALD). Seven samples of TiO2–Al2O3 bilayers are fabricated by growing Al2O3 films of different thicknesses on the surface of TiO2 films of constant thickness (100 nm). Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE®. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO2 films. The effects of TiO2 surface defects on the films’ thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al2O3 diffusion barrier layers. Increasing the ALD-Al2O3 thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO2. The thermo-optic coefficients of the 100 nm-thick ALD-TiO2 film and 30 nm-thick ALD-Al2O3 film in a bilayer are (0.048 ± 0.134) × 10−4 °C−1 and (0.680 ± 0.313) × 10−4 °C−1, respectively, at a temperature T = 62 °C.

Photosensitive adhesive bonding process of magnetooptic waveguides with Si guiding layer for optical nonreciprocal devices

NASA Astrophysics Data System (ADS)

Choowitsakunlert, Salinee; Takagiwa, Kenji; Kobashigawa, Takuya; Hosoya, Nariaki; Silapunt, Rardchawadee; Yokoi, Hideki

2018-05-01

A photosensitive adhesive bonding process for a magnetooptic waveguide for an optical isolator employing a nonreciprocal guided-radiation mode conversion is investigated at 1.55 µm. The magnetooptic waveguide is a straight rib type, and it is fabricated by bonding the Si guiding layer to a magnetic garnet. In the fabrication process, an adhesive material is diluted to obtain a certain thickness before depositing on a silicon-on-insulator (SOI) substrate. The relationship between the percent dilution ratio and the thickness of the adhesive layer is considered. The smallest gap thickness is found to be 0.66 µm at a dilution ratio of 2%.

Optical reflectance of solution processed quasi-superlattice ZnO and Al-doped ZnO (AZO) channel materials

NASA Astrophysics Data System (ADS)

Buckley, Darragh; McCormack, Robert; O'Dwyer, Colm

2017-04-01

The angle-resolved reflectance of high crystalline quality, c-axis oriented ZnO and AZO single and periodic quasi-superlattice (QSL) spin-coated TFT channels materials are presented. The data is analysed using an adapted model to accurately determine the spectral region for optical thickness and corresponding reflectance. The optical thickness agrees very well with measured thickness of 1-20 layered QSL thin films determined by transmission electron microscopy if the reflectance from lowest interference order is used. Directional reflectance for single layers or homogeneous QSLs of ZnO and AZO channel materials exhibit a consistent degree of anti-reflection characteristics from 30 to 60° (~10-12% reflection) for thickness ranging from ~40 nm to 500 nm. The reflectance of AZO single layer thin films is  <10% from 30 to 75° at 514.5 nm, and  <6% at 632.8 nm from 30-60°. The data show that ZnO and AZO with granular or periodic substructure behave optically as dispersive, continuous thin films of similar thickness, and angle-resolved spectral mapping provides a design rule for transparency or refractive index determination as a function of film thickness, substructure (dispersion) and viewing angle.

Application of maximum-likelihood estimation in optical coherence tomography for nanometer-class thickness estimation

NASA Astrophysics Data System (ADS)

Huang, Jinxin; Yuan, Qun; Tankam, Patrice; Clarkson, Eric; Kupinski, Matthew; Hindman, Holly B.; Aquavella, James V.; Rolland, Jannick P.

2015-03-01

In biophotonics imaging, one important and quantitative task is layer-thickness estimation. In this study, we investigate the approach of combining optical coherence tomography and a maximum-likelihood (ML) estimator for layer thickness estimation in the context of tear film imaging. The motivation of this study is to extend our understanding of tear film dynamics, which is the prerequisite to advance the management of Dry Eye Disease, through the simultaneous estimation of the thickness of the tear film lipid and aqueous layers. The estimator takes into account the different statistical processes associated with the imaging chain. We theoretically investigated the impact of key system parameters, such as the axial point spread functions (PSF) and various sources of noise on measurement uncertainty. Simulations show that an OCT system with a 1 μm axial PSF (FWHM) allows unbiased estimates down to nanometers with nanometer precision. In implementation, we built a customized Fourier domain OCT system that operates in the 600 to 1000 nm spectral window and achieves 0.93 micron axial PSF in corneal epithelium. We then validated the theoretical framework with physical phantoms made of custom optical coatings, with layer thicknesses from tens of nanometers to microns. Results demonstrate unbiased nanometer-class thickness estimates in three different physical phantoms.

Theoretical study of ZnS/CdS bi-layer for thin-film CdTe solar cell

NASA Astrophysics Data System (ADS)

Mohamed, H. A.; Mohamed, A. S.; Ali, H. M.

2018-05-01

The performance of CdTe solar cells is strongly limited by the thickness of CdS window layer. A higher short-circuit current density might be achieved by decreasing the thickness of CdS layer as a result of reducing the absorption losses that take place in this layer. However, it is difficult to obtain uniform and pin-hole free CdS layers thinner than 50 nm. This problem can be solved through increasing the band gap of the window layer by adding a wide band gap semiconductor such as ZnS. In this work, bi-layer ZnS/CdS film was studied as an improved window layer of ITO/ZnS/CdS/CdTe solar cell. The total thickness of ZnS/CdS layer was taken about 60 nm. The effect of optical losses due to reflection at different interfaces in the cell and absorption in ITO, ZnS, CdS as well as the recombination loss have been studied. Finally, the effects of the recombination losses in the space-charge region and the reflectivity from the back contact were taken into accounts. The results revealed that the optical losses of 23% were achieved at 60 nm thickness of CdS and theses losses minimized to 18% when ZnS layer of 30 nm thickness was added to CdS layer. The minimum optical and recombination losses of about 26% were obtained at 1 ns of electron life-time and ∼0.4 μm width of the space-charge region. The maximum efficiency of 18.5% was achieved for ITO/CdS/CdTe cell and the efficiency increased up to 20% for ITO/ZnS/CdS/CdTe cell.

Peripapillary retinal nerve fiber layer thickness in a population of 6-year-old children: findings by optical coherence tomography.

PubMed

Huynh, Son C; Wang, Xiu Ying; Rochtchina, Elena; Mitchell, Paul

2006-09-01

To study the distribution of retinal nerve fiber layer (RNFL) thickness by ocular and demographic variables in a population-based study of young children. Population-based cross-sectional study. One thousand seven hundred sixty-five of 2238 (78.9%) eligible 6-year-old children participated in the Sydney Childhood Eye Study between 2003 and 2004. Mean age was 6.7 years (50.9% boys). Detailed examination included cycloplegic autorefraction and measurement of axial length. Retinal nerve fiber layer scans using an optical coherence tomographer were performed with a circular scan pattern of 3.4-mm diameter. Multivariate analyses were performed to examine the distribution of RNFL parameters with gender, ethnicity, axial length, and refraction. Peripapillary RNFL thickness and RNFL(estimated integral) (RNFL(EI)), which measures the total cross-sectional area of ganglion cell axons converging onto the optic nerve head. Peripapillary RNFL thickness and RNFL(EI) were normally distributed. The mean+/-standard deviation RNFL average thickness was 103.7+/-11.4 microm and RNFL(EI) was 1.05+/-0.12 mm2. Retinal nerve fiber layer thickness was least for the temporal quadrant (75.7+/-14.7 microm), followed by the nasal (81.7+/-19.6 microm), inferior (127.8+/-20.5 microm), and superior (129.5+/-20.6 microm) quadrants. Multivariate adjusted RNFL average thickness was marginally greater in boys than in girls (104.7 microm vs. 103.2 microm; P = 0.007) and in East Asian than in white children (107.7 microm vs. 102.7 microm; P<0.0001). The RNFL was thinner with greater axial length (P(trend)<0.0001) and less positive spherical equivalent refractions (P(trend) = 0.004). Retinal nerve fiber layer average thickness and RNFL(EI) followed a normal distribution. Retinal nerve fiber layer thickness varied marginally with gender, but differences were more marked between white and East Asian children. Retinal nerve fiber layer thinning was associated with increasing axial length and less positive refractions.

Nondestructive analysis of automotive paints with spectral domain optical coherence tomography.

PubMed

Dong, Yue; Lawman, Samuel; Zheng, Yalin; Williams, Dominic; Zhang, Jinke; Shen, Yao-Chun

2016-05-01

We have demonstrated for the first time, to our knowledge, the use of optical coherence tomography (OCT) as an analytical tool for nondestructively characterizing the individual paint layer thickness of multiple layered automotive paints. A graph-based segmentation method was used for automatic analysis of the thickness distribution for the top layers of solid color paints. The thicknesses measured with OCT were in good agreement with the optical microscope and ultrasonic techniques that are the current standard in the automobile industry. Because of its high axial resolution (5.5 μm), the OCT technique was shown to be able to resolve the thickness of individual paint layers down to 11 μm. With its high lateral resolution (12.4 μm), the OCT system was also able to measure the cross-sectional area of the aluminum flakes in a metallic automotive paint. The range of values measured was 300-1850  μm². In summary, the proposed OCT is a noncontact, high-resolution technique that has the potential for inclusion as part of the quality assurance process in automobile coating.

The low coherence Fabry-Pérot interferometer with diamond and ZnO layers

NASA Astrophysics Data System (ADS)

Majchrowicz, D.; Den, W.; Hirsch, M.

2016-09-01

The authors present a fiber-optic Fabry-Pérot interferometer built with the application of diamond and zinc oxide (ZnO) thin layers. Thin ZnO films were deposited on the tip of a standard telecommunication single-mode optical fiber (SMF- 28) while the diamond layer was grown on the plate of silicon substrate. Investigated ZnO layers were fabricated by atomic layer deposition (ALD) and the diamond films were deposited using Microwave Plasma Enhanced Chemical Vapor Deposition (μPE CVD) system. Different thickness of layers was examined. The measurements were performed for the fiber-optic Fabry-Pérot interferometer working in the reflective mode. Spectra were registered for various thicknesses of ZnO layer and various length of the air cavity. As a light source, two superluminescent diodes (SLD) with central wavelength of 1300 nm and 1550 nm were used in measurement set-up.

High efficiency organic photovoltaic cells employing hybridized mixed-planar heterojunctions

DOEpatents

Xue, Jiangeng; Uchida, Soichi; Rand, Barry P.; Forrest, Stephen

2015-08-18

A device is provided, having a first electrode, a second electrode, and a photoactive region disposed between the first electrode and the second electrode. The photoactive region includes a first photoactive organic layer that is a mixture of an organic acceptor material and an organic donor material, wherein the first photoactive organic layer has a thickness not greater than 0.8 characteristic charge transport lengths; a second photoactive organic layer in direct contact with the first organic layer, wherein the second photoactive organic layer is an unmixed layer of the organic acceptor material of the first photoactive organic layer, and the second photoactive organic layer has a thickness not less than about 0.1 optical absorption lengths; and a third photoactive organic layer disposed between the first electrode and the second electrode and in direct contact with the first photoactive organic layer. The third photoactive organic layer is an unmixed layer of the organic donor layer of the first photoactive organic layer and has a thickness not less than about 0.1 optical absorption lengths.

Refractive index sensing in the visible/NIR spectrum using silicon nanopillar arrays.

PubMed

Visser, D; Choudhury, B Dev; Krasovska, I; Anand, S

2017-05-29

Si nanopillar (NP) arrays are investigated as refractive index sensors in the visible/NIR wavelength range, suitable for Si photodetector responsivity. The NP arrays are fabricated by nanoimprint lithography and dry etching, and coated with thin dielectric layers. The reflectivity peaks obtained by finite-difference time-domain (FDTD) simulations show a linear shift with coating layer thickness. At 730 nm wavelength, sensitivities of ~0.3 and ~0.9 nm/nm of SiO 2 and Si 3 N 4 , respectively, are obtained; and the optical thicknesses of the deposited surface coatings are determined by comparing the experimental and simulated data. The results show that NP arrays can be used for sensing surface bio-layers. The proposed method could be useful to determine the optical thickness of surface coatings, conformal and non-conformal, in NP-based optical devices.

Non-destructive analysis of DU content in the NIF hohlraums

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gharibyan, Narek; Moody, Ken J.; Shaughnessy, Dawn A.

2015-12-16

The advantage of using depleted uranium (DU) hohlraums in high-yield deuterium-tritium (DT) shots at the National Ignition Facility (NIF) is addressed by Döppner, et al., in great detail [1]. This DU based hohlraum incorporates a thin layer of DU, ~7 μm thick, on the inner surface along with a thin layer of a gold coating, ~0.7 μm thick, while the outer layer is ~22 μm thick gold. A thickness measurement of the DU layer can be performed using an optical microscope where the total DU weight can be computed provided a uniform DU layer. However, the uniformity of the thicknessmore » is not constant throughout the hohlraum since CAD drawing calculations of the DU weight do not agree with the computed values from optical measurements [2]. Therefore, a non-destructive method for quantifying the DU content in hohlraums has been established by utilizing gamma-ray spectroscopy. The details of this method, along with results from several hohlraums, are presented in this report.« less

Optical models for radio-frequency-magnetron reactively sputtered AlN films

NASA Astrophysics Data System (ADS)

Easwarakhanthan, T.; Assouar, M. B.; Pigeat, P.; Alnot, P.

2005-10-01

The optical properties of aluminum nitrate (AlN) films reactively sputtered on Si substrates using radio-frequency (rf) magnetron have been studied in this work from multiwavelength spectroscopic ellipsometry (SE) measurements performed over the 290-615 nm wavelength range. The SE modeling carried out with care to adhere as much to the ellipsometric fitting qualities is also backed up with atomic force microscopy and x-ray-diffraction measurements taken on these films thus grown to nominal thicknesses from 40 to 150 nm under the same optimized experimental conditions. It follows that the model describing the optical properties of the thicker AlN films should consist at least in three layers on the Si substrate: an almost roughnessless smooth surface overlayer that is presumed essentially of Al2O3, a bulk AlN layer, and an AlN interface layer that has a refractive index dispersion falling in the range from 2.04 [312 nm] to 1.91 [615 nm] on the average and is fairly distinguishable from the slightly higher bulk layer index which drops correspondingly from 2.12 to 1.99. These index values imply that, beneath the partly or mostly oxidized surface AlN layer, the films comprise a polycrystalline-structured bulk AlN layer above a less-microstructurally-ordered interface layer that extends over 40-55 nm from the substrate among thicker films. This ellipsometric evidence indicating the existence of the interface layer is consistent with those interface layers confirmed through electron microscopy in some previous works. However, the ellipsometrically insufficient thinner AlN films may be only modeled with the surface layer and an AlN layer. The film surface oxide layer thickness varies between 5 and 15 nm among samples. The refractive index dispersions, the layer thicknesses, and the lateral thickness variation of the films are given and discussed regarding the optical constitution of these films and the ellipsometric validity of these parameters.

Correlation between retinal nerve fibre layer thickness and optic nerve head size: an optical coherence tomography study.

PubMed

Savini, G; Zanini, M; Carelli, V; Sadun, A A; Ross-Cisneros, F N; Barboni, P

2005-04-01

To investigate the correlation between retinal nerve fibre layer (RNFL) thickness and optic nerve head (ONH) size in normal white subjects by means of optical coherence tomography (OCT). 54 eyes of 54 healthy subjects aged between 15 and 54 underwent peripapillary RNFL thickness measurement by a series of three circular scans with a 3.4 mm diameter (Stratus OCT, RNFL Thickness 3.4 acquisition protocol). ONH analysis was performed by means of six radial scans centred on the optic disc (Stratus OCT, Fast Optic Disc acquisition protocol). The mean RNFL values were correlated with the data obtained by ONH analysis. The superior, nasal, and inferior quadrant RNFL thickness showed a significant correlation with the optic disc area (R = 0.3822, p = 0.0043), (R = 0.3024, p = 0.026), (R = 0.4048, p = 0.0024) and the horizontal disc diameter (R = 0.2971, p = 0.0291), (R = 0.2752, p = 0.044), (R = 0.3970, p = 0.003). The superior and inferior quadrant RNFL thickness was also positively correlated with the vertical disc diameter (R = 0.3774, p = 0.0049), (R = 0.2793, p = 0.0408). A significant correlation was observed between the 360 degrees average RNFL thickness and the optic disc area and the vertical and horizontal disc diameters of the ONH (R = 0.4985, p = 0.0001), (R = 0.4454, p = 0.0007), (R = 0.4301, p = 0.0012). RNFL thickness measurements obtained by Stratus OCT increased significantly with an increase in optic disc size. It is not clear if eyes with large ONHs show a thicker RNFL as a result of an increased amount of nerve fibres or to the shorter distance between the circular scan and the optic disc edge.

RBS, XRR and optical reflectivity measurements of Ti-TiO{sub 2} thin films deposited by magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drogowska, K.; Institute of Materials Science, Technische Universitaet Darmstadt, Petersenstrasse 23, 64287 Darmstadt; Tarnawski, Z., E-mail: tarnawsk@agh.edu.pl

2012-02-15

Highlights: Black-Right-Pointing-Pointer The single-, bi- and tri-layered films of Ti-TiO{sub 2} deposited onto Si(1 1 1) substrates. Black-Right-Pointing-Pointer Three methods RBS, XRR, optical reflectometer were used. Black-Right-Pointing-Pointer The real thickness of each layer was smaller than 50 nm. Black-Right-Pointing-Pointer Ti and TiO{sub 2} film-densities were slightly lower than the corresponding bulk values. -- Abstract: Single-, bi- and tri-layered films of Ti-TiO{sub 2} system were deposited by d.c. pulsed magnetron sputtering from metallic Ti target in an inert Ar or reactive Ar + O{sub 2} atmosphere. The nominal thickness of each layer was 50 nm. The chemical composition and its depthmore » profile were determined by Rutherford backscattering spectroscopy (RBS). Crystallographic structure was analysed by means of X-ray diffraction (XRD) at glancing incidence. X-ray reflectometry (XRR) was used as a complementary method for the film thickness and density evaluation. Modelling of the optical reflectivity spectra of Ti-TiO{sub 2} thin films deposited onto Si(1 1 1) substrates provided an independent estimate of the layer thickness. The combined analysis of RBS, XRR and reflectivity spectra indicated the real thickness of each layer less than 50 nm with TiO{sub 2} film density slightly lower than the corresponding bulk value. Scanning Electron Microscopy (SEM) cross-sectional images revealed the columnar growth of TiO{sub 2} layers. Thickness estimated directly from SEM studies was found to be in a good agreement with the results of RBS, XRR and reflectivity spectra.« less

Correlated effects of preparation parameters and thickness on morphology and optical properties of ZnO very thin films

NASA Astrophysics Data System (ADS)

Gilliot, Mickaël; Hadjadj, Aomar

2015-08-01

Nano-granular ZnO layers have been grown using a sol-gel synthesis and spin-coating deposition process. Thin films with thicknesses ranging from 15 to 150 nm have been obtained by varying the number of deposition cycles and prepared with different synthesis conditions. Morphologies and optical properties have been carefully investigated by joint spectroscopic ellipsometry and atomic force microscopy. A correlation between the evolution of optical properties and grains morphology has been observed. It is shown that both synthesis temperature and concentration similarly allow us to change the correlated growth and properties evolution rate. Thickness variation associated to choice of synthesis parameters could be a useful way to tune morphology and optical properties of the nanostructured ZnO layers.

The light transmission and distribution in an optical fiber coated with TiO2 particles.

PubMed

Wang, Wen; Ku, Young

2003-03-01

The light delivery and distribution phenomena along the optical fiber coated with the P-25 TiO(2) particles by dipping was investigated. The surface properties (coverage, roughness and thickness) of the TiO(2) layer coated on the optical fiber were characterized by SEM micrographs. For TiO(2) layer prepared from solutions containing less than 20 wt.% of TiO(2) slurry, the thickness of layer was increased linearly with the TiO(2) slurry content in solutions. The UV light intensity transmitted along a TiO(2)-coated optical fiber decreased more rapidly than that transmitted along a non-coated fiber. Based on the experimental results, the light intensity distribution around a coated optical fiber was modeled to determine the optimum configuration for the design of optical fiber reactors under various operational conditions. Copyright 2002 Elsevier Science Ltd.

The optical properties of transferred graphene and the dielectrics grown on it obtained by ellipsometry

NASA Astrophysics Data System (ADS)

Kasikov, Aarne; Kahro, Tauno; Matisen, Leonard; Kodu, Margus; Tarre, Aivar; Seemen, Helina; Alles, Harry

2018-04-01

Graphene layers grown by chemical vapour deposition (CVD) method and transferred from Cu-foils to the oxidized Si-substrates were investigated by spectroscopic ellipsometry (SE), Raman and X-Ray Photoelectron Spectroscopy (XPS) methods. The optical properties of transferred CVD graphene layers do not always correspond to the ones of the exfoliated graphene due to the contamination from the chemicals used in the transfer process. However, the real thickness and the mean properties of the transferred CVD graphene layers can be found using ellipsometry if a real thickness of the SiO2 layer is taken into account. The pulsed laser deposition (PLD) and atomic layer deposition (ALD) methods were used to grow dielectric layers on the transferred graphene and the obtained structures were characterized using optical methods. The approach demonstrated in this work could be useful for the characterization of various materials grown on graphene.

Correction of Rayleigh Scattering Effects in Cloud Optical Thickness Retrievals

NASA Technical Reports Server (NTRS)

Wang, Meng-Hua; King, Michael D.

1997-01-01

We present results that demonstrate the effects of Rayleigh scattering on the 9 retrieval of cloud optical thickness at a visible wavelength (0.66 Am). The sensor-measured radiance at a visible wavelength (0.66 Am) is usually used to infer remotely the cloud optical thickness from aircraft or satellite instruments. For example, we find that without removing Rayleigh scattering effects, errors in the retrieved cloud optical thickness for a thin water cloud layer (T = 2.0) range from 15 to 60%, depending on solar zenith angle and viewing geometry. For an optically thick cloud (T = 10), on the other hand, errors can range from 10 to 60% for large solar zenith angles (0-60 deg) because of enhanced Rayleigh scattering. It is therefore particularly important to correct for Rayleigh scattering contributions to the reflected signal from a cloud layer both (1) for the case of thin clouds and (2) for large solar zenith angles and all clouds. On the basis of the single scattering approximation, we propose an iterative method for effectively removing Rayleigh scattering contributions from the measured radiance signal in cloud optical thickness retrievals. The proposed correction algorithm works very well and can easily be incorporated into any cloud retrieval algorithm. The Rayleigh correction method is applicable to cloud at any pressure, providing that the cloud top pressure is known to within +/- 100 bPa. With the Rayleigh correction the errors in retrieved cloud optical thickness are usually reduced to within 3%. In cases of both thin cloud layers and thick ,clouds with large solar zenith angles, the errors are usually reduced by a factor of about 2 to over 10. The Rayleigh correction algorithm has been tested with simulations for realistic cloud optical and microphysical properties with different solar and viewing geometries. We apply the Rayleigh correction algorithm to the cloud optical thickness retrievals from experimental data obtained during the Atlantic Stratocumulus Transition Experiment (ASTEX) conducted near the Azores in June 1992 and compare these results to corresponding retrievals obtained using 0.88 Am. These results provide an example of the Rayleigh scattering effects on thin clouds and further test the Rayleigh correction scheme. Using a nonabsorbing near-infrared wavelength lambda (0.88 Am) in retrieving cloud optical thickness is only applicable over oceans, however, since most land surfaces are highly reflective at 0.88 Am. Hence successful global retrievals of cloud optical thickness should remove Rayleigh scattering effects when using reflectance measurements at 0.66 Am.

An Evaluation of Peripapillary Retinal Nerve Fiber Layer Thickness in Children With Epilepsy Receiving Treatment of Valproic Acid.

PubMed

Dereci, Selim; Koca, Tuğba; Akçam, Mustafa; Türkyilmaz, Kemal

2015-07-01

We investigated the peripapillary retinal nerve fiber layer thickness with optical coherence tomography in epileptic children receiving valproic acid monotherapy. The study was conducted on children aged 8-16 years who were undergoing valproic acid monotherapy for epilepsy. The study group comprised a total of 40 children who met the inclusion criteria and 40 healthy age- and sex-matched children as a control group. Children with at least a 1-year history of epilepsy and taking 10-40 mg/kg/day treatment were included in the study. Peripapillary retinal nerve fiber layer thickness measurements were performed using Cirrus HD optical coherence tomography. All children and parents were informed about the study and informed consent was obtained from the parents of all the participants. The study group included 21 girls and 19 boys with a mean age of 10.6 ± 2.3 years. According to the results of optical coherence tomography measurements, the mean peripapillary retinal nerve fiber layer thickness was 91.6 ± 9.7 in the patient group and 95.5 ± 7.4 μm in the control group (P < 0.05). The superior peripapillary retinal nerve fiber layer thickness was 112.0 ± 13.2 in the patient group and 120.0 ± 14.7 μm in the control group (P < 0.02). According to the results of both measurements, the peripapillary retinal nerve fiber layer thickness was significantly lower in the patient group. Neither color vision loss nor visual field examination abnormality could be documented. According to the optical coherence tomography measurements, the average and superior peripapillary retinal nerve fiber layer thicknesses were thinner in patients with epilepsy who were receiving valproic acid monotherapy compared with healthy children. This situation can lead to undesirable results in terms of eye health. New studies are needed to investigate whether these findings are the result of epilepsy or can be attributed to valproic acid and whether there are adverse effects of valproic acid later in life. Copyright © 2015 Elsevier Inc. All rights reserved.

Macular Choroidal Small-Vessel Layer, Sattler's Layer and Haller's Layer Thicknesses: The Beijing Eye Study.

PubMed

Zhao, Jing; Wang, Ya Xing; Zhang, Qi; Wei, Wen Bin; Xu, Liang; Jonas, Jost B

2018-03-13

To study macular choroidal layer thickness, 3187 study participants from the population-based Beijing Eye Study underwent spectral-domain optical coherence tomography with enhanced depth imaging for thickness measurements of the macular small-vessel layer, including the choriocapillaris, medium-sized choroidal vessel layer (Sattler's layer) and large choroidal vessel layer (Haller's layer). In multivariate analysis, greater thickness of all three choroidal layers was associated (all P < 0.05) with higher prevalence of age-related macular degeneration (AMD) (except for geographic atrophy), while it was not significantly (all P > 0.05) associated with the prevalence of open-angle glaucoma or diabetic retinopathy. There was a tendency (0.07 > P > 0.02) toward thinner choroidal layers in chronic angle-closure glaucoma. The ratio of small-vessel layer thickness to total choroidal thickness increased (P < 0.001; multivariate analysis) with older age and longer axial length, while the ratios of Sattler's layer and Haller's layer thickness to total choroidal thickness decreased. A higher ratio of small-vessel layer thickness to total choroidal thickness was significantly associated with a lower prevalence of AMD (early type, intermediate type, late geographic type). Axial elongation-associated and aging-associated choroidal thinning affected Haller's and Sattler's layers more markedly than the small-vessel layer. Non-exudative and exudative AMD, except for geographic atrophy, was associated with slightly increased choroidal thickness.

Axonal loss from acute optic neuropathy documented by scanning laser polarimetry

PubMed Central

Meier, F M; Bernasconi, P; Stürmer, J; Caubergh, M-J; Landau, K

2002-01-01

Background/aims: Retinal nerve fibre layer analysis by scanning laser polarimetry has been shown to facilitate diagnosis of glaucoma while its role in glaucoma follow up is still unclear. A major difficulty is the slow reduction of retinal nerve fibre layer thickness in glaucomatous optic neuropathy. Eyes of patients were studied after acute retrobulbar optic nerve lesion in order to evaluate the usefulness of scanning laser polarimetry in documenting retinal nerve fibre layer loss over time. Methods: Five patients who suffered severe retrobulbar optic neuropathy have had repeated measurements of the retinal nerve fibre layer using scanning laser polarimetry at various intervals, the first examination being within 1 week of injury. Results: All eyes showed a marked decrease in peripapillary retinal nerve fibre layer thickness, which followed an exponential curve and occurred predominantly within 8 weeks of injury. Compared to a previous study using red-free photographs, scanning laser polarimetry showed retinal nerve fibre layer loss earlier in the course of descending atrophy. Conclusion: Scanning laser polarimetry is useful for early detection and documentation of retinal nerve fibre layer loss following acute injury to the retrobulbar optic nerve. It seems to be a promising tool for follow up of individual glaucoma patients. PMID:11864884

Spectral ellipsometry as a method for characterization of nanosized films with ferromagnetic layers

NASA Astrophysics Data System (ADS)

Hashim, H.; Singkh, S. P.; Panina, L. V.; Pudonin, F. A.; Sherstnev, I. A.; Podgornaya, S. V.; Shpetnyi, I. A.; Beklemisheva, A. V.

2017-11-01

Nanosized films with ferromagnetic layers are widely used in nanoelectronics, sensor systems and telecommunications. Their properties may strongly differ from those of bulk materials that is on account of interfaces, intermediate layers and diffusion. In the present work, spectral ellipsometry and magnetooptical methods are adapted for characterization of the optical parameters and magnetization processes in two- and three-layer Cr/NiFe, Al/NiFe and Cr(Al)/Ge/NiFe films onto a sitall substrate for various thicknesses of Cr and Al layers. At a layer thickness below 20 nm, the complex refractive coefficients depend pronouncedly on the thickness. In two-layer films, remagnetization changes weakly over a thickness of the top layer, but the coercive force in three-layer films increases by more than twice upon remagnetization, while increasing the top layer thickness from 4 to 20 nm.

Multiple scattered radiation emerging from Rayleigh and continental haze layers. 1: Radiance, polarization, and neutral points.

PubMed

Kattawar, G W; Plass, G N; Hitzfelder, S J

1976-03-01

The complete radiation field including polarization is calculated by the matrix operator method for scattering layers of various optical thicknesses. Results obtained for Rayleigh scattering are compared with those for scattering from a continental haze. Radiances calculated using Stokes vectors show differences as large as 23% compared to the approximate scalar theory of radiative transfer, while the same differences are only of the order of 0.1% for a continental haze phase function. The polarization of the reflected and transmitted radiation is given for a wide range of optical thicknesses of the scattering layer, for various solar zenith angles, and various surface albedos. Two entirely different types of neutral points occur for aerosol phase functions. Rayleigh-like neutral points (RNP) arise from the zero polarization in single scattering that occurs for all phase functions at scattering angles of 0 degrees and 180 degrees . For Rayleigh phase functions, the position of the RNP varies appreciably with the optical thickness of the scattering layer. At low solar elevations there may be four RNP. For a continental haze phase function the position of the RNP in the reflected radiation shows only a small variation with the optical thickness, and the RNP exists in the transmitted radiation only for extremely small optical thicknesses. Another type of neutral point (NRNP) exists for aerosol phase functions. It is associated with the zeros of the single scattered polarization, which occur between the end points of the curve; these are called non-Rayleigh neutral points (NRNP). There may be from zero to four of these neutral points associated with each zero of the single scattering curve. They occur over a range of azimuthal angles, unlike the RNP that are in the principal plane only. The position of these neutral points is given as a function of solar angle and optical thickness.

Multiple scattered radiation emerging from continental haze layers. 1: Radiance, polarization, and neutral points

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Plass, G. N.; Hitzfelder, S. J.

1975-01-01

The complete radiation field is calculated for scattering layers of various optical thicknesses. Results obtained for Rayleigh and haze scattering are compared. Calculated radiances show differences as large as 23% compared to the approximate scalar theory of radiative transfer, while the same differences are approximately 0.1% for a continental haze phase function. The polarization of reflected and transmitted radiation is given for various optical thicknesses, solar zenith angles, and surface albedos. Two types of neutral points occur for aerosol phase functions. Rayleigh-like neutral points arise from zero polarization that occurs at scattering angles of 0 deg and 180 deg. For Rayleigh phase functions, the position of these points varies with the optical thickness of the scattering layer. Non-Rayleigh neutral points are associated with the zeros of polarization which occur between the end points of the single scattering curve, and are found over a wide range of azimuthal angles.

ELLIPSOMETRY OF ELECTROCHEMICAL SURFACE LAYERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muller, R.H.

1977-06-01

Ellipsometry is concerned with the analysis and interpretation of changes in the state of polarization caused by reflection. The technique has found increasing interest in recent years for the measurement of thin films because it is unusually sensitive, disturbs the object minimally and can be applied to surfaces contained in any optically transparent medium. Film thicknesses amenable to measurement range from fractional monoatomic coverage to microscopic thicknesses. The measurement of changes in the state of polarization of light due to reflection provides an unusually sensitive tool for observing surface layers in any optically transparent environment. A fast, self-compensating ellipsometer hasmore » been used to observe the electrochemical formation of reacted surface layers. The optical effect of mass-transport boundary layers and component imperfections have been taken into account in the interpretation of results.« less

African Descent and Glaucoma Evaluation Study (ADAGES)

PubMed Central

Girkin, Christopher A.; Sample, Pamela A.; Liebmann, Jeffrey M.; Jain, Sonia; Bowd, Christopher; Becerra, Lida M.; Medeiros, Felipe A.; Racette, Lyne; Dirkes, Keri A.; Weinreb, Robert N.; Zangwill, Linda M.

2010-01-01

Objective To define differences in optic disc, retinal nerve fiber layer, and macular structure between healthy participants of African (AD) and European descent (ED) using quantitative imaging techniques in the African Descent and Glaucoma Evaluation Study (ADAGES). Methods Reliable images were obtained using stereoscopic photography, confocal scanning laser ophthalmoscopy (Heidelberg retina tomography [HRT]), and optical coherence tomography (OCT) for 648 healthy subjects in ADAGES. Findings were compared and adjusted for age, optic disc area, and reference plane height where appropriate. Results The AD participants had significantly greater optic disc area on HRT (2.06 mm2; P<.001) and OCT (2.47 mm2; P<.001) and a deeper HRT cup depth than the ED group (P<.001). Retinal nerve fiber layer thickness was greater in the AD group except within the temporal region, where it was significantly thinner. Central macular thickness and volume were less in the AD group. Conclusions Most of the variations in optic nerve morphologic characteristics between the AD and ED groups are due to differences in disc area. However, differences remain in HRT cup depth, OCT macular thickness and volume, and OCT retinal nerve fiber layer thickness independent of these variables. These differences should be considered in the determination of disease status. PMID:20457974

Ratiometric analysis of optical coherence tomography-measured in vivo retinal layer thicknesses for the detection of early diabetic retinopathy.

PubMed

Bhaduri, Basanta; Shelton, Ryan L; Nolan, Ryan M; Hendren, Lucas; Almasov, Alexandra; Labriola, Leanne T; Boppart, Stephen A

2017-11-01

Influence of diabetes mellitus (DM) and diabetic retinopathy (DR) on parafoveal retinal thicknesses and their ratios was evaluated. Six retinal layer boundaries were segmented from spectral-domain optical coherence tomography images using open-source software. Five study groups: (1) healthy control (HC) subjects, and subjects with (2) controlled DM, (3) uncontrolled DM, (4) controlled DR and (5) uncontrolled DR, were identified. The one-way analyses of variance (ANOVA) between adjacent study groups (i. e. 1 with 2, 2 with 3, etc) indicated differences in retinal thicknesses and ratios. Overall retinal thickness, ganglion cell layer (GCL) thickness, inner plexiform layer (IPL) thickness, and their combination (GCL+ IPL), appeared to be significantly less in the uncontrolled DM group when compared to controlled DM and controlled DR groups. Although the combination of nerve fiber layer (NFL) and GCL, and IPL thicknesses were not different, their ratio, (NFL+GCL)/IPL, was found to be significantly higher in the controlled DM group compared to the HC group. Comparisons of the controlled DR group with the controlled DM group, and with the uncontrolled DR group, do not show any differences in the layer thicknesses, though several significant ratios were obtained. Ratiometric analysis may provide more sensitive parameters for detecting changes in DR. Picture: A representative segmented OCT image of the human retina is shown. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theoretical analysis of optical properties of dielectric coatings dependence on substrate subsurface defects

NASA Astrophysics Data System (ADS)

Shen, Jian; Liu, Shouhua; Shen, Zicai; Shao, Jianda; Fan, Zhengxiu

2006-03-01

A model for refractive index of stratified dielectric substrate was put forward according to theories of inhomogeneous coatings. The substrate was divided into surface layer, subsurface layer and bulk layer along the normal direction of its surface. Both the surface layer (separated into N1 sublayers of uniform thickness) and subsurface layer (separated into N2 sublayers of uniform thickness), whose refractive indices have different statistical distributions, are equivalent to inhomogeneous coatings, respectively. And theoretical deduction was carried out by employing characteristic matrix method of optical coatings. An example of mathematical calculation for optical properties of dielectric coatings had been presented. The computing results indicate that substrate subsurface defects can bring about additional bulk scattering and change propagation characteristic in thin film and substrate. Therefore, reflectance, reflective phase shift and phase difference of an assembly of coatings and substrate deviate from ideal conditions. The model will provide some beneficial theory directions for improving optical properties of dielectric coatings via substrate surface modification.

Impact of active layer thickness of nitrogen-doped In–Sn–Zn–O films on materials and thin film transistor performances

NASA Astrophysics Data System (ADS)

Li, Zhi-Yue; Yang, Hao-Zhi; Chen, Sheng-Chi; Lu, Ying-Bo; Xin, Yan-Qing; Yang, Tian-Lin; Sun, Hui

2018-05-01

Nitrogen-doped indium tin zinc oxide (ITZO:N) thin film transistors (TFTs) were deposited on SiO2 (200 nm)/p-Si〈1 0 0〉 substrates by RF magnetron sputtering at room temperature. The structural, chemical compositions, surface morphology, optical and electrical properties as a function of the active layer thickness were investigated. As the active layer thickness increases, Zn content decreases and In content increases gradually. Meanwhile, Sn content is almost unchanged. When the thickness of the active layer is more than 45 nm, the ITZO:N films become crystallized and present a crystal orientation along InN(0 0 2) plan. No matter what the thickness is, ITZO:N films always display a high transmittance above 80% in the visible region. Their optical band gaps fluctuate between 3.4 eV and 3.62 eV. Due to the dominance of low interface trap density and high carrier concentration, ITZO:N TFT shows enhanced electrical properties as the active layer thickness is 35 nm. Its field-effect mobility, on/off radio and sub-threshold swing are 17.53 cm2 V‑1 · s‑1, 106 and 0.36 V/dec, respectively. These results indicate that the suitable thickness of the active layer can enhance the quality of ITZO:N films and decrease the defects density of ITZO:N TFT. Thus, the properties of ITZO:N TFT can be optimized by adjusting the thickness of the active layer.

Long-term Effect of Panretinal Photocoagulation on Spectral Domain Optical Coherence Tomography Measurements in Diabetic Retinopathy.

PubMed

Lee, Haeng-Jin; Kang, Tae-Seen; Kwak, Baek-Soo; Jo, Young-Joon; Kim, Jung-Yeul

2017-08-01

To evaluate the effects of panretinal photocoagulation on spectral domain optical coherence tomography measurements in diabetic retinopathy by comparing the thicknesses of the central macula, retinal nerve fiber layer, and ganglion cell layer, we used a Cirrus HD OCT® (Carl Zeiss Meditec, Dublin, CA, USA) in normal and diabetic retinopathy cohorts. We analyzed patients who visited our retinal clinic between May 2013 and July 2014. The patients were classified into four groups: normal (Group A), diabetes without diabetic retinopathy (Group B), severe nonproliferative or proliferative diabetic retinopathy (Group C), and at least 3 years after panretinal photocoagulation treatment (Group D). The mean thicknesses of the macula, retinal nerve fiber layer, and ganglion cell layer in each group were compared by measuring a macular cube 512 × 128 scan and an optic disc cube 200 × 200 scan twice. In total, 154 patients were enrolled. The mean thickness of the central macula in groups A to D was 257.2, 256.8, 257.4, and 255.6 µm, respectively, and did not differ significantly. The mean thickness of the RNFL in group A to D was 96.8, 96.5, 97.2, and 92.8 µm, respectively, and was significantly lower in group D (decreased in the inferior, superior, and nasal sectors, but increased in the temporal). The mean thickness of the ganglion cell layer was also significantly lower in group D (A, 84.5 µm; B, 84.4 µm; C, 82.5 µm; D, 78.5 µm). The mean thicknesses of the retinal nerve fiber and ganglion cell layers were decreased significantly in eyes with diabetic eye disease treated with panretinal photocoagulation compared to normal or eyes with diabetic eye disease that had not been laser-treated. Laser treatment might have altered the thickness of the inner layer of the retina, and such changes should be considered in diabetic retinopathy patients after panretinal photocoagulation treatment.

Optically Immersed Bolometer IR Detectors Based on V2O5 Thin Films with Polyimide Thermal Impedance Control Layer for Space Applications

NASA Astrophysics Data System (ADS)

Sumesh, M. A.; Thomas, Beno; Vijesh, T. V.; Mohan Rao, G.; Viswanathan, M.; Karanth, S. P.

2018-01-01

Optically immersed bolometer IR detectors were fabricated using electron beam evaporated vanadium oxide as the sensing material. Spin-coated polyimide was used as medium to optically immerse the sensing element to the flat surface of a hemispherical germanium lens. This optical immersion layer also serves as the thermal impedance control layer and decides the performance of the devices in terms of responsivity and noise parameters. The devices were packaged in suitable electro-optical packages and the detector parameters were studied in detail. Thermal time constant varies from 0.57 to 6.0 ms and responsivity from 75 to 757 V W-1 corresponding to polyimide thickness in the range 2 to 70 μm for a detector bias of 9 V in the wavelength region of 14-16 μm. Highest D* obtained was 1.2×108 cmHz1/2 W-1. Noise equivalent temperature difference (NETD) of 20 mK was achieved for devices with polyimide thickness more than 32 μm. The figure of merit, NETD × τ product which describes trade-off between thermal time constant and sensitivity is also extensively studied for devices having different thickness of thermal impedance layers.

A grating coupler with a trapezoidal hole array for perfectly vertical light coupling between optical fibers and waveguides

NASA Astrophysics Data System (ADS)

Mizutani, Akio; Eto, Yohei; Kikuta, Hisao

2017-12-01

A grating coupler with a trapezoidal hole array was designed and fabricated for perfectly vertical light coupling between a single-mode optical fiber and a silicon waveguide on a silicon-on-insulator (SOI) substrate. The grating coupler with an efficiency of 53% was computationally designed at a 1.1-µm-thick buried oxide (BOX) layer. The grating coupler and silicon waveguide were fabricated on the SOI substrate with a 3.0-µm-thick BOX layer by a single full-etch process. The measured coupling efficiency was 24% for TE-polarized light at 1528 nm wavelength, which was 0.69 times of the calculated coupling efficiency for the 3.0-µm-thick BOX layer.

Optical coherence tomography measurement of the retinal nerve fiber layer in normal and juvenile glaucomatous eyes.

PubMed

Mrugacz, Malgorzata; Bakunowicz-Lazarczyk, Alina

2005-01-01

The aim of this study was to quantitatively assess and compare the thickness of the retinal nerve fiber layer (RNFL) in normal and glaucomatous eyes of children using the optical coherence tomograph. The mean RNFL thickness of normal eyes (n=26) was compared with that of glaucomatous eyes (n=26). The eyes were classified into diagnostic groups based on conventional ophthalmological physical examination, Humphrey 30-2 visual fields, stereoscopic optic nerve head photography, and optical coherence tomography. The mean RNFL was significantly thinner in glaucomatous eyes than in normal eyes: 95+/-26.3 and 132+/-24.5 microm, respectively. More specifically, the RNFL was significantly thinner in glaucomatous eyes than in normal eyes in the inferior quadrant: 87+/-23.5 and 122+/-24.2 microm, respectively. The mean and inferior quadrant RFNL thicknesses as measured by the optical coherence tomograph showed a statistically significant correlation with glaucoma. Optical coherence tomography may contribute to tracking of juvenile glaucoma progression. Copyright (c) 2005 S. Karger AG, Basel.

Retinal single-layer analysis with optical coherence tomography shows inner retinal layer thinning in Huntington's disease as a potential biomarker.

PubMed

Gulmez Sevim, Duygu; Unlu, Metin; Gultekin, Murat; Karaca, Cagatay

2018-02-12

There have been ongoing clinical trials of therapeutic agents in Huntington's disease (HD) which requires development of reliable biomarkers of disease progression. There have been studies in the literature with conflicting results on the involvement of retina in HD, and up to date there is not a study evaluating the single retinal layers in HD. We aimed to evaluate the specific retinal changes in HD and their usability as potential disease progression markers. This cross-sectional study used spectral-domain optical coherence tomography with automatic segmentation to measure peripapillary retinal nerve fiber layer (pRNFL) thickness and the thickness and volume of retinal layers in foveal scans of 15 patients with HD and 15 age- and sex-matched controls. Genetic testing results, disease duration, HD disease burden scores and Unified HD Rating Scales motor scores were acquired for the patients. Temporal pRNFL, macular RNFL (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer and outer plexiform layer thicknesses and IPL, retinal pigment epithelium and outer macular volume were found lower in HD compared to controls, while outer nuclear layer and outer retinal layer thickness were increased (p < 0.05). We found significant correlations between inner retinal layer thicknesses, most significantly with mRNFL and GCL and disease progression markers. The outcomes of this study points out that retinal layers, most significantly mRNFL and GCL, are strongly correlated with the disease progression in HD and could serve as useful biomarkers for disease progression.

Analysis of photonic band gap in novel piezoelectric photonic crystal

NASA Astrophysics Data System (ADS)

Malar Kodi, A.; Doni Pon, V.; Joseph Wilson, K. S.

2018-03-01

The transmission properties of one-dimensional novel photonic crystal having silver-doped novel piezoelectric superlattice and air as the two constituent layers have been investigated by means of transfer matrix method. By changing the appropriate thickness of the layers and filling factor of nanocomposite system, the variation in the photonic band gap can be studied. It is found that the photonic band gap increases with the filling factor of the metal nanocomposite and with the thickness of the layer. These structures possess unique characteristics enabling one to operate as optical waveguides, selective filters, optical switches, integrated piezoelectric microactuators, etc.

Study of interlayer coupling between FePt and FeCoB thin films through MgO spacer layer

NASA Astrophysics Data System (ADS)

Singh, Sadhana; Kumar, Dileep; Gupta, Mukul; Reddy, V. Raghvendra

2017-05-01

Interlayer exchange coupling between hard-FePt and soft-FeCoB magnetic layers has been studied with increasing thickness of insulator MgO spacer layer in FePt/MgO/FeCoB sandwiched structure. A series of the samples were prepared in identical condition using ion beam sputtering method and characterized for their magnetic and structural properties using magneto-optical Kerr effect (MOKE) and X-ray reflectivity measurements. The nature of coupling between FePt and FeCoB was found to be ferromagnetic which decreases exponentially with increasing thickness of MgO layer. At very low thickness of MgO layer, both layers were found strongly coupled thus exhibiting coherent magnetization reversal. At higher thickness, both layers were found decoupled and magnetization reversal occurred at different switching fields. Strong coupling at very low thickness is attributed to pin holes in MgO layer which lead to direct coupling whereas on increasing thickness, coupling may arise due to magneto-static interactions.

Examining the Impact of Overlying Aerosols on the Retrieval of Cloud Optical Properties from Passive Remote Sensing

NASA Technical Reports Server (NTRS)

Coddington, O. M.; Pilewskie, P.; Redemann, J.; Platnick, S.; Russell, P. B.; Schmidt, K. S.; Gore, W. J.; Livingston, J.; Wind, G.; Vukicevic, T.

2010-01-01

Haywood et al. (2004) show that an aerosol layer above a cloud can cause a bias in the retrieved cloud optical thickness and effective radius. Monitoring for this potential bias is difficult because space ]based passive remote sensing cannot unambiguously detect or characterize aerosol above cloud. We show that cloud retrievals from aircraft measurements above cloud and below an overlying aerosol layer are a means to test this bias. The data were collected during the Intercontinental Chemical Transport Experiment (INTEX-A) study based out of Portsmouth, New Hampshire, United States, above extensive, marine stratus cloud banks affected by industrial outflow. Solar Spectral Flux Radiometer (SSFR) irradiance measurements taken along a lower level flight leg above cloud and below aerosol were unaffected by the overlying aerosol. Along upper level flight legs, the irradiance reflected from cloud top was transmitted through an aerosol layer. We compare SSFR cloud retrievals from below ]aerosol legs to satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) in order to detect an aerosol ]induced bias. In regions of small variation in cloud properties, we find that SSFR and MODIS-retrieved cloud optical thickness compares within the uncertainty range for each instrument while SSFR effective radius tend to be smaller than MODIS values (by 1-2 microns) and at the low end of MODIS uncertainty estimates. In regions of large variation in cloud properties, differences in SSFR and MODIS ]retrieved cloud optical thickness and effective radius can reach values of 10 and 10 microns, respectively. We include aerosols in forward modeling to test the sensitivity of SSFR cloud retrievals to overlying aerosol layers. We find an overlying absorbing aerosol layer biases SSFR cloud retrievals to smaller effective radii and optical thickness while nonabsorbing aerosols had no impact.

Diagnostic value of ganglion cell-inner plexiform layer for early detection of ethambutol-induced optic neuropathy.

PubMed

Lee, Ju-Yeun; Han, Jinu; Seo, Jeong Gi; Park, Kyung-Ah; Oh, Sei Yeul

2018-04-26

To evaluate the diagnostic value of macular ganglion cell-inner plexiform layer (mGCIPL) thickness versus peripapillary retinal nerve fibre layer (pRNFL) thickness for the early detection of ethambutol-induced optic neuropathy (EON). Twenty-eight eyes of 15 patients in the EON group and 100 eyes of 53 healthy subjects in the control group were included. All patients with EON demonstrated the onset of visual symptoms within 3 weeks. Diagnostic power for pRNFL and mGCIPL thicknesses measured by Cirrus spectral-domain optical coherence tomography was assessed by area under the receiver operating characteristic (AUROC) curves and sensitivity. All of the mGCIPL thickness measurements were thinner in the EON group than in the control group in early EON (p<0.001). All of pRNFL thicknesses except inferior RNFL showed AUROC curves above 0.5, and all of the mGCIPL thicknesses showed AUROC curves above 0.5. The AUROC of the average mGCIPL (0.812) thickness was significantly greater than that of the average pRNFL (0.507) thickness (p<0.001). Of all the mGCIPL-related parameters considered, the minimum thickness showed the greatest AUROC value (0.863). The average mGCIPL thickness showed a weak correlation with visual field pattern standard deviations (r 2 =0.158, p<0.001). In challenging cases of EON, the mGCIPL thickness has better diagnostic performance in detecting early-onset EON as compared with using pRNFL thickness. Among the early detection ability of mGCIPL thickness, minimum GCIPL thickness has high diagnostic ability. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Three-dimensional retinal imaging with high-speed ultrahigh-resolution optical coherence tomography.

PubMed

Wojtkowski, Maciej; Srinivasan, Vivek; Fujimoto, James G; Ko, Tony; Schuman, Joel S; Kowalczyk, Andrzej; Duker, Jay S

2005-10-01

To demonstrate high-speed, ultrahigh-resolution, 3-dimensional optical coherence tomography (3D OCT) and new protocols for retinal imaging. Ultrahigh-resolution OCT using broadband light sources achieves axial image resolutions of approximately 2 microm compared with standard 10-microm-resolution OCT current commercial instruments. High-speed OCT using spectral/Fourier domain detection enables dramatic increases in imaging speeds. Three-dimensional OCT retinal imaging is performed in normal human subjects using high-speed ultrahigh-resolution OCT. Three-dimensional OCT data of the macula and optic disc are acquired using a dense raster scan pattern. New processing and display methods for generating virtual OCT fundus images; cross-sectional OCT images with arbitrary orientations; quantitative maps of retinal, nerve fiber layer, and other intraretinal layer thicknesses; and optic nerve head topographic parameters are demonstrated. Three-dimensional OCT imaging enables new imaging protocols that improve visualization and mapping of retinal microstructure. An OCT fundus image can be generated directly from the 3D OCT data, which enables precise and repeatable registration of cross-sectional OCT images and thickness maps with fundus features. Optical coherence tomography images with arbitrary orientations, such as circumpapillary scans, can be generated from 3D OCT data. Mapping of total retinal thickness and thicknesses of the nerve fiber layer, photoreceptor layer, and other intraretinal layers is demonstrated. Measurement of optic nerve head topography and disc parameters is also possible. Three-dimensional OCT enables measurements that are similar to those of standard instruments, including the StratusOCT, GDx, HRT, and RTA. Three-dimensional OCT imaging can be performed using high-speed ultrahigh-resolution OCT. Three-dimensional OCT provides comprehensive visualization and mapping of retinal microstructures. The high data acquisition speeds enable high-density data sets with large numbers of transverse positions on the retina, which reduces the possibility of missing focal pathologies. In addition to providing image information such as OCT cross-sectional images, OCT fundus images, and 3D rendering, quantitative measurement and mapping of intraretinal layer thickness and topographic features of the optic disc are possible. We hope that 3D OCT imaging may help to elucidate the structural changes associated with retinal disease as well as improve early diagnosis and monitoring of disease progression and response to treatment.

Retinal nerve fiber layer thickness and neuropsychiatric manifestations in systemic lupus erythematosus.

PubMed

Shulman, S; Shorer, R; Wollman, J; Dotan, G; Paran, D

2017-11-01

Background Cognitive impairment is frequent in systemic lupus erythematosus. Atrophy of the corpus callosum and hippocampus have been reported in patients with systemic lupus erythematosus, and diffusion tensor imaging studies have shown impaired white matter integrity, suggesting that white matter damage in systemic lupus erythematosus may underlie the cognitive impairment as well as other neuropsychiatric systemic lupus erythematosus manifestations. Retinal nerve fiber layer thickness, as assessed by optical coherence tomography, has been suggested as a biomarker for white matter damage in neurologic disorders such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. Retinal nerve fiber layer thinning may occur early, even in patients with mild clinical symptoms. Aim The objective of this study was to assess the association of retinal nerve fiber layer thickness, as a biomarker of white matter damage in systemic lupus erythematosus patients, with neuropsychiatric systemic lupus erythematosus manifestations, including cognitive impairment. Methods Twenty-one consecutive patients with systemic lupus erythematosus underwent neuropsychological testing using a validated computerized battery of tests as well as the Rey-Auditory verbal learning test. All 21 patients, as well as 11 healthy, age matched controls, underwent optical coherence tomography testing to assess retinal nerve fiber layer thickness. Correlations between retinal nerve fiber layer thickness and results in eight cognitive domains assessed by the computerized battery of tests as well as the Rey-Auditory verbal learning test were assessed in patients with systemic lupus erythematosus, with and without neuropsychiatric systemic lupus erythematosus, and compared to retinal nerve fiber layer thickness in healthy controls. Results No statistically significant correlation was found between retinal nerve fiber layer thickness in patients with systemic lupus erythematosus as compared to healthy controls. When evaluating by subgroups, no correlation was found between patients with or without neuropsychiatric systemic lupus erythematosus or cognitive impairment and retinal nerve fiber layer thickness. Conclusion Retinal nerve fiber layer thickness of systemic lupus erythematosus patients was not found to be statistically different compared to controls. Within systemic lupus erythematosus patients there was no correlation between retinal nerve fiber layer thickness and cognitive impairment or other neuropsychiatric systemic lupus erythematosus manifestations.

Spatial and thickness dependence of coupling interaction of surface states and influence on transport and optical properties of few-layer Bi2Se3

NASA Astrophysics Data System (ADS)

Li, Zhongjun; Chen, Shi; Sun, Jiuyu; Li, Xingxing; Qiu, Huaili; Yang, Jinlong

2018-02-01

Coupling interaction between the bottom and top surface electronic states and the influence on transport and optical properties of Bi2Se3 thin films with 1-8 quintuple layers (QLs) have been investigated by first principles calculations. Obvious spatial and thickness dependences of coupling interaction are found by analyzing hybridization of two surface states. In the thin film with a certain thickness, from the outer to inner atomic layers, the coupling interaction exhibits an increasing trend. On the other hand, as thickness increases, the coupling interaction shows a disproportionate decrease trend. Moreover, the system with 3 QLs exhibits stronger interaction than that with 2 QLs. The presence of coupling interaction would suppress destructive interference of surface states and enhance resistance in various degrees. In view of the inversely proportional relation to transport channel width, the resistance of thin films should show disproportionate thickness dependence. This prediction is qualitatively consistent with the transport measurements at low temperature. Furthermore, the optical properties also exhibit obvious thickness dependence. Especially as the thickness increases, the coupling interaction results in red and blue shifts of the multiple-peak structures in low and high energy regions of imaginary dielectric function, respectively. The red shift trend is in agreement with the recent experimental observation and the blue shift is firstly predicted by the present calculation. The present results give a concrete understanding of transport and optical properties in devices based on Bi2Se3 thin films with few QLs.

Assessment of PLIF-Based Heat Release Rate Markers using DNS of Highly Turbulent Premixed Flames

NASA Astrophysics Data System (ADS)

Zhao, Xinyu; Zhang, Peiyu; Wabel, Timothy; Steinberg, Adam; Wang, Haiou; Hawkes, Evatt

2017-11-01

Planar Laser Induced Fluorescence (PLIF) remains the most common measurement tool for describing turbulent flame topologies. However, the interpretation of the images obtained from such experiments can be obscured due to various experimental constraints, such as the finite laser thickness, the application of intensifier, etc. Synthetic-PLIF images are constructed in this study to understand the effects of various experimental reality using direct numerical simulations. Two DNS databases of highly turbulent premixed methane flames are employed, to generate the synthetic PLIF images. The thickness of the laser sheet and optical blur parameters are systematically varied to study their effects on the implied reactive layer thickness, topological correspondence with heat release rates, as well as the resolved scales of the flames. It is found that the optical blur can have a significant influence on the measured layer thickness, and significant discrepancy between the DNS and the synthetic PLIF arises when the laser thickness is approximately twice the size of the reactive layers.

Macular Ganglion Cell Imaging Study: Covariate Effects on the Spectral Domain Optical Coherence Tomography for Glaucoma Diagnosis.

PubMed

Jeong, Jae Hoon; Choi, Yun Jeong; Park, Ki Ho; Kim, Dong Myung; Jeoung, Jin Wook

2016-01-01

To evaluate the effect of multiple covariates on the diagnostic performance of the Cirrus high-definition optical coherence tomography (HD-OCT) for glaucoma detection. A prospective case-control study was performed and included 173 recently diagnosed glaucoma patients and 63 unaffected individuals from the Macular Ganglion Cell Imaging Study. Regression analysis of receiver operating characteristic were conducted to evaluate the influence of age, spherical equivalent, axial length, optic disc size, and visual field index on the macular ganglion cell-inner plexiform layer (GCIPL) and peripapillary retinal nerve fiber layer (RNFL) measurements. Disease severity, as measured by visual field index, had a significant effect on the diagnostic performance of all Cirrus HD-OCT parameters. Age, axial length and optic disc size were significantly associated with diagnostic accuracy of average peripapillary RNFL thickness, whereas axial length had a significant effect on the diagnostic accuracy of average GCIPL thickness. Diagnostic performance of the Cirrus HD-OCT may be more accurate in the advanced stages of glaucoma than at earlier stages. A smaller optic disc size was significantly associated with improved the diagnostic ability of average RNFL thickness measurements; however, GCIPL thickness may be less affected by age and optic disc size.

Accurate identification of layer number for few-layer WS2 and WSe2 via spectroscopic study.

PubMed

Li, Yuanzheng; Li, Xinshu; Yu, Tong; Yang, Guochun; Chen, Heyu; Zhang, Cen; Feng, Qiushi; Ma, Jiangang; Liu, Weizhen; Xu, Haiyang; Liu, Yichun; Liu, Xinfeng

2018-03-23

Transition metal dichalcogenides (TMDs) with a typical layered structure are highly sensitive to their layer number in optical and electronic properties. Seeking a simple and effective method for layer number identification is very important to low-dimensional TMD samples. Herein, a rapid and accurate layer number identification of few-layer WS 2 and WSe 2 is proposed via locking their photoluminescence (PL) peak-positions. As the layer number of WS 2 /WSe 2 increases, it is found that indirect transition emission is more thickness-sensitive than direct transition emission, and the PL peak-position differences between the indirect and direct transitions can be regarded as fingerprints to identify their layer number. Theoretical calculation confirms that the notable thickness-sensitivity of indirect transition derives from the variations of electron density of states of W atom d-orbitals and chalcogen atom p-orbitals. Besides, the PL peak-position differences between the indirect and direct transitions are almost independent of different insulating substrates. This work not only proposes a new method for layer number identification via PL studies, but also provides a valuable insight into the thickness-dependent optical and electronic properties of W-based TMDs.

Influence of Clinical Factors and Magnification Correction on Normal Thickness Profiles of Macular Retinal Layers Using Optical Coherence Tomography.

PubMed

Higashide, Tomomi; Ohkubo, Shinji; Hangai, Masanori; Ito, Yasuki; Shimada, Noriaki; Ohno-Matsui, Kyoko; Terasaki, Hiroko; Sugiyama, Kazuhisa; Chew, Paul; Li, Kenneth K W; Yoshimura, Nagahisa

2016-01-01

To identify the factors which significantly contribute to the thickness variabilities in macular retinal layers measured by optical coherence tomography with or without magnification correction of analytical areas in normal subjects. The thickness of retinal layers {retinal nerve fiber layer (RNFL), ganglion cell layer plus inner plexiform layer (GCLIPL), RNFL plus GCLIPL (ganglion cell complex, GCC), total retina, total retina minus GCC (outer retina)} were measured by macular scans (RS-3000, NIDEK) in 202 eyes of 202 normal Asian subjects aged 20 to 60 years. The analytical areas were defined by three concentric circles (1-, 3- and 6-mm nominal diameters) with or without magnification correction. For each layer thickness, a semipartial correlation (sr) was calculated for explanatory variables including age, gender, axial length, corneal curvature, and signal strength index. Outer retinal thickness was significantly thinner in females than in males (sr2, 0.07 to 0.13) regardless of analytical areas or magnification correction. Without magnification correction, axial length had a significant positive sr with RNFL (sr2, 0.12 to 0.33) and a negative sr with GCLIPL (sr2, 0.22 to 0.31), GCC (sr2, 0.03 to 0.17), total retina (sr2, 0.07 to 0.17) and outer retina (sr2, 0.16 to 0.29) in multiple analytical areas. The significant sr in RNFL, GCLIPL and GCC became mostly insignificant following magnification correction. The strong correlation between the thickness of inner retinal layers and axial length appeared to result from magnification effects. Outer retinal thickness may differ by gender and axial length independently of magnification correction.

Influence of Clinical Factors and Magnification Correction on Normal Thickness Profiles of Macular Retinal Layers Using Optical Coherence Tomography

PubMed Central

Higashide, Tomomi; Ohkubo, Shinji; Hangai, Masanori; Ito, Yasuki; Shimada, Noriaki; Ohno-Matsui, Kyoko; Terasaki, Hiroko; Sugiyama, Kazuhisa; Chew, Paul; Li, Kenneth K. W.; Yoshimura, Nagahisa

2016-01-01

Purpose To identify the factors which significantly contribute to the thickness variabilities in macular retinal layers measured by optical coherence tomography with or without magnification correction of analytical areas in normal subjects. Methods The thickness of retinal layers {retinal nerve fiber layer (RNFL), ganglion cell layer plus inner plexiform layer (GCLIPL), RNFL plus GCLIPL (ganglion cell complex, GCC), total retina, total retina minus GCC (outer retina)} were measured by macular scans (RS-3000, NIDEK) in 202 eyes of 202 normal Asian subjects aged 20 to 60 years. The analytical areas were defined by three concentric circles (1-, 3- and 6-mm nominal diameters) with or without magnification correction. For each layer thickness, a semipartial correlation (sr) was calculated for explanatory variables including age, gender, axial length, corneal curvature, and signal strength index. Results Outer retinal thickness was significantly thinner in females than in males (sr2, 0.07 to 0.13) regardless of analytical areas or magnification correction. Without magnification correction, axial length had a significant positive sr with RNFL (sr2, 0.12 to 0.33) and a negative sr with GCLIPL (sr2, 0.22 to 0.31), GCC (sr2, 0.03 to 0.17), total retina (sr2, 0.07 to 0.17) and outer retina (sr2, 0.16 to 0.29) in multiple analytical areas. The significant sr in RNFL, GCLIPL and GCC became mostly insignificant following magnification correction. Conclusions The strong correlation between the thickness of inner retinal layers and axial length appeared to result from magnification effects. Outer retinal thickness may differ by gender and axial length independently of magnification correction. PMID:26814541

Long-term Characterization of Retinal Degeneration in Royal College of Surgeons Rats Using Spectral-Domain Optical Coherence Tomography

PubMed Central

Ryals, Renee C.; Andrews, Michael D.; Datta, Shreya; Coyner, Aaron S.; Fischer, Cody M.; Wen, Yuquan; Pennesi, Mark E.; McGill, Trevor J.

2017-01-01

Purpose Prospective treatments for age-related macular degeneration and inherited retinal degenerations are commonly evaluated in the Royal College of Surgeons (RCS) rat before translation into clinical application. Historically, retinal thickness obtained through postmortem anatomic assessments has been a key outcome measure; however, utility of this measurement is limited because it precludes the ability to perform longitudinal studies. To overcome this limitation, the present study was designed to provide a baseline longitudinal quantification of retinal thickness in the RCS rat by using spectral-domain optical coherence tomography (SD-OCT). Methods Horizontal and vertical linear SD-OCT scans centered on the optic nerve were captured from Long-Evans control rats at P30, P60, P90 and from RCS rats between P17 and P90. Total retina (TR), outer nuclear layer+ (ONL+), inner nuclear layer (INL), and retinal pigment epithelium (RPE) thicknesses were quantified. Histologic sections of RCS retina obtained from P21 to P60 were compared to SD-OCT images. Results In RCS rats, TR and ONL+ thickness decreased significantly as compared to Long-Evans controls. Changes in INL and RPE thickness were not significantly different between control and RCS retinas. From P30 to P90 a subretinal hyperreflective layer (HRL) was observed and quantified in RCS rats. After correlation with histology, the HRL was identified as disorganized outer segments and the location of accumulated debris. Conclusions Retinal layer thickness can be quantified longitudinally throughout the course of retinal degeneration in the RCS rat by using SD-OCT. Thickness measurements obtained with SD-OCT were consistent with previous anatomic thickness assessments. This study provides baseline data for future longitudinal assessment of therapeutic agents in the RCS rat. PMID:28253400

Long-term Characterization of Retinal Degeneration in Royal College of Surgeons Rats Using Spectral-Domain Optical Coherence Tomography.

PubMed

Ryals, Renee C; Andrews, Michael D; Datta, Shreya; Coyner, Aaron S; Fischer, Cody M; Wen, Yuquan; Pennesi, Mark E; McGill, Trevor J

2017-03-01

Prospective treatments for age-related macular degeneration and inherited retinal degenerations are commonly evaluated in the Royal College of Surgeons (RCS) rat before translation into clinical application. Historically, retinal thickness obtained through postmortem anatomic assessments has been a key outcome measure; however, utility of this measurement is limited because it precludes the ability to perform longitudinal studies. To overcome this limitation, the present study was designed to provide a baseline longitudinal quantification of retinal thickness in the RCS rat by using spectral-domain optical coherence tomography (SD-OCT). Horizontal and vertical linear SD-OCT scans centered on the optic nerve were captured from Long-Evans control rats at P30, P60, P90 and from RCS rats between P17 and P90. Total retina (TR), outer nuclear layer+ (ONL+), inner nuclear layer (INL), and retinal pigment epithelium (RPE) thicknesses were quantified. Histologic sections of RCS retina obtained from P21 to P60 were compared to SD-OCT images. In RCS rats, TR and ONL+ thickness decreased significantly as compared to Long-Evans controls. Changes in INL and RPE thickness were not significantly different between control and RCS retinas. From P30 to P90 a subretinal hyperreflective layer (HRL) was observed and quantified in RCS rats. After correlation with histology, the HRL was identified as disorganized outer segments and the location of accumulated debris. Retinal layer thickness can be quantified longitudinally throughout the course of retinal degeneration in the RCS rat by using SD-OCT. Thickness measurements obtained with SD-OCT were consistent with previous anatomic thickness assessments. This study provides baseline data for future longitudinal assessment of therapeutic agents in the RCS rat.

Correlation between skin, bone, and cerebrospinal fluid layer thickness and optical coefficients measured by multidistance frequency-domain near-infrared spectroscopy in term and preterm infants.

PubMed

Demel, Anja; Feilke, Katharina; Wolf, Martin; Poets, Christian F; Franz, Axel R

2014-01-01

Near-infrared spectroscopy (NIRS) is increasingly used in neonatal intensive care. We investigated the impact of skin, bone, and cerebrospinal fluid (CSF) layer thickness in term and preterm infants on absorption-(μa) and/or reduced scattering coefficients (μs') measured by multidistance frequency-domain (FD)-NIRS. Transcranial ultrasound was performed to measure the layer thicknesses. Correlations were only statistically significant for μa at 692 nm with bone thickness and μs' at 834 nm with skin thickness. There is no evidence that skin, bone, or CSF thickness have an important effect on μa and μs'. Layer thicknesses of skin, bone, and CSF in the range studied do not seem to affect cerebral oxygenation measurements by multidistance FD-NIRS significantly.

Does Optic Nerve Head Size Variation Affect Circumpapillary Retinal Nerve Fiber Layer Thickness Measurement by Optical Coherence Tomography?

PubMed Central

Huang, David; Chopra, Vikas; Lu, Ake Tzu-Hui; Tan, Ou; Francis, Brian; Varma, Rohit

2012-01-01

Purpose. To determine the relationship between retinal nerve fiber layer (RNFL) thickness, optic disc size, and image magnification. Methods. The cohort consisted of 196 normal eyes of 101 participants in the Advanced Imaging for Glaucoma Study (AIGS), a multicenter, prospective, longitudinal study to develop advanced imaging technologies for glaucoma diagnosis. Scanning laser tomography was used to measure disc size. Optical coherence tomography (OCT) was used to perform circumpapillary RNFL thickness measurements using the standard fixed 3.46-mm nominal scan diameter. A theoretical model of magnification effects was developed to relate RNFL thickness (overall average) with axial length and magnification. Results. Multivariate regression showed no significant correlation between RNFL thickness and optic disc area (95% confidence interval [CI] = −0.9 to 4.1 μm/mm2, P = 0.21). Linear regression showed that RNFL thickness depended significantly on axial length (slope = −3.1 μm/mm, 95% CI = −4.9 to −1.3, P = 0.001) and age (slope = −0.3 μm/y, 95% CI = −0.5 to −0.2, P = 0.0002). The slope values agreed closely with the values predicted by the magnification model. Conclusions. There is no significant association between RNFL thickness and optic disc area. Previous publications that showed such an association may have been biased by the effect of axial length on fundus image magnification and, therefore, both measured RNFL thickness and apparent disc area. The true diameter of the circumpapillary OCT scan is larger for a longer eye (more myopic eye), leading to a thinner RNFL measurement. Adjustment of measured RNFL thickness by axial length, in addition to age, may lead to a tighter normative range and improve the detection of RNFL thinning due to glaucoma. PMID:22743319

Changes in optical coherence tomography measurements after orbital wall decompression in dysthyroid optic neuropathy.

PubMed

Park, Kyung-Ah; Kim, Yoon-Duck; Woo, Kyung In

2018-06-01

The purpose of our study was to assess changes in peripapillary retinal nerve fiber layer (RNFL) thickness after orbital wall decompression in eyes with dysthyroid optic neuropathy (DON). We analyzed peripapillary optical coherence tomography (OCT) images (Cirrus HD-OCT) from controls and patients with DON before and 1 and 6 months after orbital wall decompression. There was no significant difference in mean preoperative peripapillary retinal nerve fiber layer thickness between eyes with DON and controls. The superior and inferior peripapillary RNFL thickness decreased significantly 1 month after decompression surgery compared to preoperative values (p = 0.043 and p = 0.022, respectively). The global average, superior, temporal, and inferior peripapillary RNFL thickness decreased significantly 6 months after decompression surgery compared to preoperative values (p = 0.015, p = 0.028, p = 0.009, and p = 0.006, respectively). Patients with greater preoperative inferior peripapillary RNFL thickness tended to have better postoperative visual acuity at the last visit (p = 0.024, OR = 0.926). Our data revealed a significant decrease in peripapillary RNFL thickness postoperatively after orbital decompression surgery in patients with DON. We also found that greater preoperative inferior peripapillary RNFL thickness was associated with better visual outcomes. We suggest that RNFL thickness can be used as a prognostic factor for DON before decompression surgery.

Early detection of macular and peripapillary changes with spectralis optical coherence tomography in patients with prediabetes.

PubMed

Şahin, Muhammed; Şahin, Alparslan; Kılınç, Faruk; Karaalp, Ümit; Yüksel, Harun; Özkurt, Zeynep Gürsel; Türkcü, Fatih Mehmet; Çaça, İhsan

2018-02-01

To compare the retina ganglion cell complex (GCC) layer and peripapillary nerve fibre layer thickness (pRNFL) in patients with prediabetes and healthy subjects analysed by spectral domain optical coherence tomography (SD-OCT). This cross-sectional and comparative study included prediabetic patients and healthy subjects. All participants underwent SD-OCT measurement of pRNFL thickness, and GCC thickness. A total of 30 eyes of the 30 patients with prediabetes and 30 eyes of 30 controls were included. The overall calculated pRNFL thicknesses were similar between the prediabetic and control subjects. The GCC thickness was significantly lower in all quadrants of the inner macula, and outer nasal quadrant in the prediabetes group when compared to the control group. Our study demonstrated that inner macular GCC thickness was significantly thinner in prediabetic subjects. As a result neurodegeneration may play role in the thinning of GCC.

Optical properties of marine stratocumulus clouds modified by ships

NASA Technical Reports Server (NTRS)

King, Michael D.; Radke, Lawrence F.; Hobbs, Peter V.

1993-01-01

Results are presented of an application of the diffusion domain method to multispectral solar radiation measurements obtained deep within a marine stratocumulus cloud layer modified by pollution from ships. In situ airborne measurements of the relative angular distribution of scattered radiation are compared to known asymptotic expressions for the intensity field deep within an optically thick cloud layer. Analytical expressions relating the ratio of the nadir-to-zenith intensities to surface reflectance, similarity parameter, and scaled optical depth beneath the aircraft flight level are used to analyze measurements obtained with the cloud absorption radiometer mounted on the University of Washington's C-131A research aircraft. It is shown that the total optical thickness of the cloud layer increased in the ship tracks, in contrast to the similarity parameter, which decreased. The decrease in absorption was a direct consequence of the reduction in cloud droplet size that occurred within the ship tracks.

Electrically tunable coherent optical absorption in graphene with ion gel.

PubMed

Thareja, Vrinda; Kang, Ju-Hyung; Yuan, Hongtao; Milaninia, Kaveh M; Hwang, Harold Y; Cui, Yi; Kik, Pieter G; Brongersma, Mark L

2015-03-11

We demonstrate electrical control over coherent optical absorption in a graphene-based Salisbury screen consisting of a single layer of graphene placed in close proximity to a gold back reflector. The screen was designed to enhance light absorption at a target wavelength of 3.2 μm by using a 600 nm-thick, nonabsorbing silica spacer layer. An ionic gel layer placed on top of the screen was used to electrically gate the charge density in the graphene layer. Spectroscopic reflectance measurements were performed in situ as a function of gate bias. The changes in the reflectance spectra were analyzed using a Fresnel based transfer matrix model in which graphene was treated as an infinitesimally thin sheet with a conductivity given by the Kubo formula. The analysis reveals that a careful choice of the ionic gel layer thickness can lead to optical absorption enhancements of up to 5.5 times for the Salisbury screen compared to a suspended sheet of graphene. In addition to these absorption enhancements, we demonstrate very large electrically induced changes in the optical absorption of graphene of ∼3.3% per volt, the highest attained so far in a device that features an atomically thick active layer. This is attributable in part to the more effective gating achieved with the ion gel over the conventional dielectric back gates and partially by achieving a desirable coherent absorption effect linked to the presence of the thin ion gel that boosts the absorption by 40%.

Graphene-based multilayer resonance structure to enhance the optical pressure on a Mie particle

NASA Astrophysics Data System (ADS)

Hassanzadeh, Abdollah; Mohammadnezhad, Mohammadbagher

2016-04-01

We theoretically investigate the optical force exerted on a Mie dielectric particle in the evanescent field of a graphene-based resonance multilayer structure using the arbitrary beam theory and the theory of multilayer films. The resonance structure consists of several thin films including a dielectric film (MgF2), a metal film (silver or gold), and several graphene layers which are located on a prism base. The effects of the metal film thickness and the number of graphene layers on the optical force are numerically investigated. The thickness of the metal layer and the number of graphene layers are optimized to reach the highest optical force. The numerical results show that an optimized composition of graphene and gold leads to a higher optical force compared to that of the graphene and silver. The optical force was enhanced resonantly by four orders of magnitude for the resonance structure containing graphene and a gold film and by three orders of magnitude for the structure containing graphene and a silver film compared to other similar resonance structures. We hope that the results presented in this paper can provide an excellent means of improving the optical manipulation of particles and enable the provision of effective optical tweezers, micromotors, and microaccelelators.

Fabrication of precision optics using an imbedded reference surface

DOEpatents

Folta, James A.; Spiller, Eberhard

2005-02-01

The figure of a substrate is very precisely measured and a figured-correcting layer is provided on the substrate. The thickness of the figure-correcting layer is locally measured and compared to the first measurement. The local measurement of the figure-correcting layer is accomplished through a variety of methods, including interferometry and fluorescence or ultrasound measurements. Adjustments in the thickness of the figure-correcting layer are made until the top of the figure-correcting layer matches a desired figure specification.

Mutual Photoluminescence Quenching and Photovoltaic Effect in Large-Area Single-Layer MoS2-Polymer Heterojunctions.

PubMed

Shastry, Tejas A; Balla, Itamar; Bergeron, Hadallia; Amsterdam, Samuel H; Marks, Tobin J; Hersam, Mark C

2016-11-22

Two-dimensional transition metal dichalcogenides (TMDCs) have recently attracted attention due to their superlative optical and electronic properties. In particular, their extraordinary optical absorption and semiconducting band gap have enabled demonstrations of photovoltaic response from heterostructures composed of TMDCs and other organic or inorganic materials. However, these early studies were limited to devices at the micrometer scale and/or failed to exploit the unique optical absorption properties of single-layer TMDCs. Here we present an experimental realization of a large-area type-II photovoltaic heterojunction using single-layer molybdenum disulfide (MoS 2 ) as the primary absorber, by coupling it to the organic π-donor polymer PTB7. This TMDC-polymer heterojunction exhibits photoluminescence intensity that is tunable as a function of the thickness of the polymer layer, ultimately enabling complete quenching of the TMDC photoluminescence. The strong optical absorption in the TMDC-polymer heterojunction produces an internal quantum efficiency exceeding 40% for an overall cell thickness of less than 20 nm, resulting in exceptional current density per absorbing thickness in comparison to other organic and inorganic solar cells. Furthermore, this work provides insight into the recombination processes in type-II TMDC-polymer heterojunctions and thus provides quantitative guidance to ongoing efforts to realize efficient TMDC-based solar cells.

Variations in retinal nerve fiber layer measurements on optical coherence tomography after implantation of trifocal intraocular lens.

PubMed

García-Bella, Javier; Martínez de la Casa, José M; Talavero González, Paula; Fernández-Vigo, José I; Valcarce Rial, Laura; García-Feijóo, Julián

2018-01-01

To establish the changes produced after implantation of a trifocal intraocular lens (IOL) on retinal nerve fiber layer measurements performed with Fourier-domain optical coherence tomography (OCT). This prospective study included 100 eyes of 50 patients with bilateral cataract in surgical range, no other associated ocular involvement, refractive errors between +5 and -5 spherical diopters, and less than 1.5 D of corneal astigmatism. The eyes were operated by phacoemulsification with implantation of 2 different trifocal IOLs (FineVision and AT LISA tri 839MP) in randomized equal groups. Cirrus OCT and Spectralis OCT were performed before surgery and 3 months later. Both analyzed the thickness of the nerve fiber layer and thickness divided by quadrants (6 in case of Spectralis and 4 in case of Cirrus HD). The mean age of patients was 67.5 ± 5.8 years. The global nerve fiber layer thickness measured with Spectralis OCT was 96.77 μm before surgery and 99.55 μm after. With Cirrus OCT, the global thickness was 85.29 μm before surgery and 89.77 μm after. Statistically significant differences in global thickness measurements between preimplantation and postimplantation of the IOL were found with both OCT in the 2 groups. Statistically significant differences were also found in temporal and superior quadrants. The implantation of a diffractive trifocal IOL alters the results of the optic nerve fiber layer on Fourier-domain OCT in these patients, which should be taken into account in the posterior study of these patients.

Quantitative Raman spectrum and reliable thickness identification for atomic layers on insulating substrates.

PubMed

Li, Song-Lin; Miyazaki, Hisao; Song, Haisheng; Kuramochi, Hiromi; Nakaharai, Shu; Tsukagoshi, Kazuhito

2012-08-28

We demonstrate the possibility in quantifying the Raman intensities for both specimen and substrate layers in a common stacked experimental configuration and, consequently, propose a general and rapid thickness identification technique for atomic-scale layers on dielectric substrates. Unprecedentedly wide-range Raman data for atomically flat MoS(2) flakes are collected to compare with theoretical models. We reveal that all intensity features can be accurately captured when including optical interference effect. Surprisingly, we find that even freely suspended chalcogenide few-layer flakes have a stronger Raman response than that from the bulk phase. Importantly, despite the oscillating intensity of specimen spectrum versus thickness, the substrate weighted spectral intensity becomes monotonic. Combined with its sensitivity to specimen thickness, we suggest this quantity can be used to rapidly determine the accurate thickness for atomic layers.

Tuning of in-plane optical anisotropy by inserting ultra-thin InAs layer at interfaces in (001)-grown GaAs/AlGaAs quantum wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, J. L., E-mail: jlyu@semi.ac.cn; Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083; Key Laboratory of Optoelectronic Materials Chemistry and Physics, Chinese Academy of Sciences, Fuzhou 350002

2015-01-07

The in-plane optical anisotropy (IPOA) in (001)-grown GaAs/AlGaAs quantum wells (QWs) with different well widths varying from 2 nm to 8 nm has been studied by reflectance difference spectroscopy. Ultra-thin InAs layers with thickness ranging from 0.5 monolayer (ML) to 1.5 ML have been inserted at GaAs/AlGaAs interfaces to tune the asymmetry in the QWs. It is demonstrated that the IPOA can be accurately tailored by the thickness of the inserted ultra-thin InAs layer at the interfaces. Strain-induced IPOA has also been extracted by using a stress apparatus. We find that the intensity of the strain-induced IPOA decreases with the thickness ofmore » the inserted InAs layer, while that of the interface-induced IPOA increases with the thickness of the InAs layer. Theoretical calculations based on 6 band k ⋅ p theory have been carried out, and good agreements with experimental results are obtained. Our results demonstrate that, the IPOA of the QWs can be greatly and effectively tuned by inserting an ultra-thin InAs layer with different thicknesses at the interfaces of QWs, which does not significantly influence the transition energies and the transition probability of QWs.« less

Cost effective flat plate photovoltaic modules using light trapping

NASA Technical Reports Server (NTRS)

Bain, C. N.; Gordon, B. A.; Knasel, T. M.; Malinowski, R. L.

1981-01-01

Work in optical trapping in 'thick films' is described to form a design guide for photovoltaic engineers. A thick optical film can trap light by diffusive reflection and total internal reflection. Light can be propagated reasonably long distances compared with layer thicknesses by this technique. This makes it possible to conduct light from inter-cell and intra-cell areas now not used in photovoltaic modules onto active cell areas.

Quenching Mo optical losses in CIGS solar cells by a point contacted dual-layer dielectric spacer: a 3-D optical study.

PubMed

Rezaei, Nasim; Isabella, Olindo; Vroon, Zeger; Zeman, Miro

2018-01-22

A 3-D optical modelling was calibrated to calculate the light absorption and the total reflection of fabricated CIGS solar cells. Absorption losses at molybdenum (Mo) / CIGS interface were explained in terms of plasmonic waves. To quench these losses, we assumed the insertion of a lossless dielectric spacer between Mo and CIGS, whose optical properties were varied. We show that such a spacer with low refractive index and proper thickness can significantly reduce absorption in Mo in the long wavelength regime and improve the device's rear reflectance, thus leading to enhanced light absorption in the CIGS layer. Therefore, we optimized a realistic two-layer MgF 2 / Al 2 O 3 dielectric spacer to exploit (i) the passivation properties of ultra-thin Al 2 O 3 on the CIGS side for potential high open-circuit voltage and (ii) the low refractive index of MgF 2 on the Mo side to reduce its optical losses. Combining our realistic spacer with optically-optimized point contacts increases the implied photocurrent density of a 750 nm-thick CIGS layer by 10% for the wavelengths between 700 and 1150 nm with respect to the reference cell. The elimination of plasmonic resonances in the new structure leads to a higher electric field magnitude at the bottom of CIGS layer and justifies the improved optical performance.

Subsurface optical stimulation of the rat prostate nerves using continuous-wave near-infrared laser radiation

NASA Astrophysics Data System (ADS)

Tozburun, Serhat; Lagoda, Gwen A.; Burnett, Arthur L.; Fried, Nathaniel M.

2012-02-01

Successful identification and preservation of the cavernous nerves (CN), which are responsible for sexual function, during prostate cancer surgery, will require subsurface detection of the CN beneath a thin fascia layer. This study explores optical nerve stimulation (ONS) in the rat with a fascia layer placed over the CN. Two near-IR diode lasers (1455 nm and 1550 nm lasers) were used to stimulate the CN in CW mode with a 1-mm-diameter spot in 8 rats. The 1455 nm wavelength provides an optical penetration depth (OPD) of ~350 μm, while 1550 nm provides an OPD of ~1000 μm (~3 times deeper than 1455 nm and 1870 nm wavelengths previously tested). Fascia layers with thicknesses of 85 - 600 μm were placed over the CN. Successful ONS was confirmed by an intracavernous pressure (ICP) response in the rat penis at 1455 nm through fascia 110 μm thick and at 1550 nm through fascia 450 μm thick. Higher incident laser power was necessary and weaker and slower ICP responses were observed as fascia thickness was increased. Subsurface ONS of the rat CN at a depth of 450 μm using a 1550 nm laser is feasible.

Film Thickness Allowance and Waveguide Length in 3-Layer Unidirectional Magneto-Optical TE-TM Mode Converter

NASA Astrophysics Data System (ADS)

Abe, Masanori; Nakagawa, Hidenobu; Gomi, Manabu; Nomura, Shoichiro

1982-01-01

The film thickness allowance and the waveguide length in a 3-layer (substrate/film/air) magneto-optical unidirectional TE-TM mode converter which utilizes the intrinsic birefringence in an anisotropic material are calculated at λ0{=}1.55 μm. The film material should be gyrotropic in order to make the waveguide length short, and the film thickness allowance is relaxed by reducing the ratio of the dielectric constant of the film to that of the substrate. When the waveguide is made of an isotropic gyrotropic film of YIG deposited on an anisotropic substrate (which may be gyrotropic or not), the restriction on the film thickness can in practice be removed, but this requires precise control of the dielectric constant of the film and the substrate instead.

Role of Retinal Nerve Fiber Layer Thickness and Optic Disk Measurement by OCT on Early Diagnosis of Glaucoma.

PubMed

Hua, Zanmei; Fang, Qiuyun; Sha, Xiangyin; Yang, Ruiming; Hong, Zuopeng

2015-03-01

Glaucoma is an eye disease that can lead to irreversible optic nerve damage and cause blindness. Optical coherence tomography (OCT) allows an early diagnosis of glaucoma by the measurements of the retinal nerve fiber and optic disc parameters. A retrospective study was designed to analyze the effects of the measurement of the retinal nerve fiber layer (RNFL) thickness and the optic disc tomography by spectral-domain OCT on the early diagnosis of suspected glaucoma and primary open angle glaucoma (POAG). This was a clinical case-control study. The RNFL thickness around the optic disc and optic disk tomographic parameters of the control (n = 51, 98 eyes), suspected glaucoma (n = 81, 146 eyes), and POAG groups (n = 55, 106 eyes) were measured by OCT. The parameters included superior, inferior, nasal and temporal mean RNFL thickness, disc area (DA), cup area (CA), rim area (RA), disc volume (DV), cup volume (CV), rim volume (RV), cup/disc area ratio (CA/DA), rim/disc area ratio (RA/DA), cup/disc volume ratio (CV/DV) and rim/disc volume ratio (RV/DV). Superior, nasal, and mean RNFL parameters, DA, CA,RA, DV, CV, CA/DA, RA/DA, CV/DV and RV/DV significantly differed among three groups by single-factorial ANOVA. Inferior and temporal RNFL thickness significantly differed between the control and POAG groups. No significant difference was observed in RV among three groups. In the POAG group, the maximum area under the ROC curve (AROC) of mean RNFL thickness was 0.845. The maximum AROC of optic disk parameters was RA/DA (0.998), followed by CA/DA (0.997). The AROC of CA, RA, CV, and DV were all > 0.900. OCT may serve as a useful diagnostic modality in distinguishing suspected glaucoma from POAG.

Forming aspheric optics by controlled deposition

DOEpatents

Hawryluk, A.M.

1998-04-28

An aspheric optical element is disclosed formed by depositing material onto a spherical surface of an optical element by controlled deposition to form an aspheric surface of desired shape. A reflecting surface, single or multi-layer, can then be formed on the aspheric surface by evaporative or sputtering techniques. Aspheric optical elements are suitable for deep ultra-violet (UV) and x-ray wavelengths. The reflecting surface may, for example, be a thin ({approx}100 nm) layer of aluminum, or in some cases the deposited modifying layer may function as the reflecting surface. For certain applications, multi-layer reflective surfaces may be utilized, such as chromium-carbon or tungsten-carbon multi-layer, with the number of layers and thickness being determined by the intended application. 4 figs.

Forming aspheric optics by controlled deposition

DOEpatents

Hawryluk, Andrew M.

1998-01-01

An aspheric optical element formed by depositing material onto a spherical surface of an optical element by controlled deposition to form an aspheric surface of desired shape. A reflecting surface, single or multi-layer, can then be formed on the aspheric surface by evaporative or sputtering techniques. Aspheric optical elements are suitable for deep ultra-violet (UV) and x-ray wavelengths. The reflecting surface may, for example, be a thin (.about.100 nm) layer of aluminum, or in some cases the deposited modifying layer may function as the reflecting surface. For certain applications, multi-layer reflective surfaces may be utilized, such as chromium-carbon or tungsten-carbon multi-layer, with the number of layers and thickness being determined by the intended application.

In vivo sweat film layer thickness measured with Fourier-domain optical coherence tomography (FD-OCT)

NASA Astrophysics Data System (ADS)

Jonathan, Enock

2008-06-01

While human sweat secretion is accepted as a mechanism by which the body cools off, excessive sweating (hyperhidrosis) is now appreciated as a medical condition and the primary site for diagnosis is the palm of the hand. We propose sweat film layer thickness as a potential clinical diagnostic parameter when screening for excessive sweating. In this preliminary study we demonstrate the usefulness of Fourier-domain optical coherence tomography (FD-OCT) for measurement of sweat film thickness in vivo with micron-scale resolution on the hand of a human volunteer. FD-OCT has a superior image acquisition time and identification of active sweat glands, ducts and pores is also possible.

Macular Ganglion Cell Imaging Study: Covariate Effects on the Spectral Domain Optical Coherence Tomography for Glaucoma Diagnosis

PubMed Central

Jeong, Jae Hoon; Choi, Yun Jeong; Park, Ki Ho; Kim, Dong Myung

2016-01-01

Purpose To evaluate the effect of multiple covariates on the diagnostic performance of the Cirrus high-definition optical coherence tomography (HD-OCT) for glaucoma detection. Methods A prospective case-control study was performed and included 173 recently diagnosed glaucoma patients and 63 unaffected individuals from the Macular Ganglion Cell Imaging Study. Regression analysis of receiver operating characteristic were conducted to evaluate the influence of age, spherical equivalent, axial length, optic disc size, and visual field index on the macular ganglion cell-inner plexiform layer (GCIPL) and peripapillary retinal nerve fiber layer (RNFL) measurements. Results Disease severity, as measured by visual field index, had a significant effect on the diagnostic performance of all Cirrus HD-OCT parameters. Age, axial length and optic disc size were significantly associated with diagnostic accuracy of average peripapillary RNFL thickness, whereas axial length had a significant effect on the diagnostic accuracy of average GCIPL thickness. Conclusions Diagnostic performance of the Cirrus HD-OCT may be more accurate in the advanced stages of glaucoma than at earlier stages. A smaller optic disc size was significantly associated with improved the diagnostic ability of average RNFL thickness measurements; however, GCIPL thickness may be less affected by age and optic disc size. PMID:27490718

Spatial frequency domain spectroscopy of two layer media

NASA Astrophysics Data System (ADS)

Yudovsky, Dmitry; Durkin, Anthony J.

2011-10-01

Monitoring of tissue blood volume and oxygen saturation using biomedical optics techniques has the potential to inform the assessment of tissue health, healing, and dysfunction. These quantities are typically estimated from the contribution of oxyhemoglobin and deoxyhemoglobin to the absorption spectrum of the dermis. However, estimation of blood related absorption in superficial tissue such as the skin can be confounded by the strong absorption of melanin in the epidermis. Furthermore, epidermal thickness and pigmentation varies with anatomic location, race, gender, and degree of disease progression. This study describes a technique for decoupling the effect of melanin absorption in the epidermis from blood absorption in the dermis for a large range of skin types and thicknesses. An artificial neural network was used to map input optical properties to spatial frequency domain diffuse reflectance of two layer media. Then, iterative fitting was used to determine the optical properties from simulated spatial frequency domain diffuse reflectance. Additionally, an artificial neural network was trained to directly map spatial frequency domain reflectance to sets of optical properties of a two layer medium, thus bypassing the need for iteration. In both cases, the optical thickness of the epidermis and absorption and reduced scattering coefficients of the dermis were determined independently. The accuracy and efficiency of the iterative fitting approach was compared with the direct neural network inversion.

Optical coherence tomography in retinitis pigmentosa: reproducibility and capacity to detect macular and retinal nerve fiber layer thickness alterations.

PubMed

Garcia-Martin, Elena; Pinilla, Isabel; Sancho, Eva; Almarcegui, Carmen; Dolz, Isabel; Rodriguez-Mena, Diego; Fuertes, Isabel; Cuenca, Nicolas

2012-09-01

To evaluate the ability of time-domain and Fourier-domain optical coherence tomographies (OCTs) to detect macular and retinal nerve fiber layer atrophies in retinitis pigmentosa (RP). To test the intrasession reproducibility using three OCT instruments (Stratus, Cirrus, and Spectralis). Eighty eyes of 80 subjects (40 RP patients and 40 healthy subjects) underwent a visual field examination, together with 3 macular scans and 3 optic disk evaluations by the same experienced examiner using 3 OCT instruments. Differences between healthy and RP eyes were compared. The relationship between measurements with each OCT instrument was evaluated. Repeatability was studied by intraclass correlation coefficients and coefficients of variation. Macular and retinal nerve fiber layer atrophies were detected in RP patients for all OCT parameters. Macular and retinal nerve fiber layer thicknesses, as determined by the different OCTs, were correlated but significantly different (P < 0.05). Reproducibility was moderately high using Stratus, good using Cirrus and Spectralis, and excellent using the Tru-track technology of Spectralis. In RP eyes, measurements showed higher variability compared with healthy eyes. Differences in thickness measurements existed between OCT instruments, despite there being a high degree of correlation. Fourier-domain OCT can be considered a valid and repeatability technique to detect retinal nerve fiber layer atrophy in RP patients.

THOR: Cloud Thickness from Off beam Lidar Returns

NASA Technical Reports Server (NTRS)

Cahalan, Robert F.; McGill, Matthew; Kolasinski, John; Varnai, Tamas; Yetzer, Ken

2004-01-01

Conventional wisdom is that lidar pulses do not significantly penetrate clouds having optical thickness exceeding about tau = 2, and that no returns are detectable from more than a shallow skin depth. Yet optically thicker clouds of tau much greater than 2 reflect a larger fraction of visible photons, and account for much of Earth s global average albedo. As cloud layer thickness grows, an increasing fraction of reflected photons are scattered multiple times within the cloud, and return from a diffuse concentric halo that grows around the incident pulse, increasing in horizontal area with layer physical thickness. The reflected halo is largely undetected by narrow field-of-view (FoV) receivers commonly used in lidar applications. THOR - Thickness from Off-beam Returns - is an airborne wide-angle detection system with multiple FoVs, capable of observing the diffuse halo, detecting wide-angle signal from which physical thickness of optically thick clouds can be retrieved. In this paper we describe the THOR system, demonstrate that the halo signal is stronger for thicker clouds, and validate physical thickness retrievals for clouds having z > 20, from NASA P-3B flights over the Department of Energy/Atmospheric Radiation Measurement/Southern Great Plains site, using the lidar, radar and other ancillary ground-based data.

Automated pharmaceutical tablet coating layer evaluation of optical coherence tomography images

NASA Astrophysics Data System (ADS)

Markl, Daniel; Hannesschläger, Günther; Sacher, Stephan; Leitner, Michael; Khinast, Johannes G.; Buchsbaum, Andreas

2015-03-01

Film coating of pharmaceutical tablets is often applied to influence the drug release behaviour. The coating characteristics such as thickness and uniformity are critical quality parameters, which need to be precisely controlled. Optical coherence tomography (OCT) shows not only high potential for off-line quality control of film-coated tablets but also for in-line monitoring of coating processes. However, an in-line quality control tool must be able to determine coating thickness measurements automatically and in real-time. This study proposes an automatic thickness evaluation algorithm for bi-convex tables, which provides about 1000 thickness measurements within 1 s. Beside the segmentation of the coating layer, optical distortions due to refraction of the beam by the air/coating interface are corrected. Moreover, during in-line monitoring the tablets might be in oblique orientation, which needs to be considered in the algorithm design. Experiments were conducted where the tablet was rotated to specified angles. Manual and automatic thickness measurements were compared for varying coating thicknesses, angles of rotations, and beam displacements (i.e. lateral displacement between successive depth scans). The automatic thickness determination algorithm provides highly accurate results up to an angle of rotation of 30°. The computation time was reduced to 0.53 s for 700 thickness measurements by introducing feasibility constraints in the algorithm.

Effect of improper scan alignment on retinal nerve fiber layer thickness measurements using Stratus optical coherence tomograph.

PubMed

Vizzeri, Gianmarco; Bowd, Christopher; Medeiros, Felipe A; Weinreb, Robert N; Zangwill, Linda M

2008-08-01

Misalignment of the Stratus optical coherence tomograph scan circle placed by the operator around the optic nerve head (ONH) during each retinal nerve fiber layer (RNFL) examination can affect the instrument reproducibility and its theoretical ability to detect true structural changes in the RNFL thickness over time. We evaluated the effect of scan circle placement on RNFL measurements. Observational clinical study. Sixteen eyes of 8 normal participants were examined using the Stratus optical coherence tomograph Fast RNFL thickness acquisition protocol (software version 4.0.7; Carl Zeiss Meditec, Dublin, CA). Four consecutive images were taken by the same operator with the circular scan centered on the optic nerve head. Four images each with the scan displaced superiorly, inferiorly, temporally, and nasally were also acquired. Differences in average and sectoral RNFL thicknesses were determined. For the centered scans, the coefficients of variation (CV) and the intraclass correlation coefficient for the average RNFL thickness measured were calculated. When the average RNFL thickness of the centered scans was compared with the average RNFL thickness of the displaced scans individually using analysis of variance with post-hoc analysis, no difference was found between the average RNFL thickness of the nasally (105.2 microm), superiorly (106.2 microm), or inferiorly (104.1 microm) displaced scans and the centered scans (106.4 microm). However, a significant difference (analysis of variance with Dunnett's test: F=8.82, P<0.0001) was found between temporally displaced scans (115.8 microm) and centered scans. Significant differences in sectoral RNFL thickness measurements were found between centered and each displaced scan. The coefficient of variation for average RNFL thickness was 1.75% and intraclass correlation coefficient was 0.95. In normal eyes, average RNFL thickness measurements are robust and similar with significant superior, inferior, and nasal scan displacement, but average RNFL thickness is greater when scans are displaced temporally. Parapapillary scan misalignment produces significant changes in RNFL assessment characterized by an increase in measured RNFL thickness in the quadrant in which the scan is closer to the disc, and a significant decrease in RNFL thickness in the quadrant in which the scan is displaced further from the optic disc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliver, J. B.

Planetary substrate rotation for optical-coating deposition is evaluated based on initial and final positions for a given layer with different numbers of revolutions and various deposition-source locations. The influence of partial revolutions of the rotation system is analyzed relative to the total number of planetary revolutions in that layer to determine the relative impact on film thickness and uniformity. Furthermore, guidance is provided on the necessary planetary revolutions that should take place in each layer versus the expected error level in the layer thickness for the modeled system.

Polypeptide multilayer films on colloidal particles: an in situ electro-optical study.

PubMed

Radeva, Tsetska; Kamburova, Kamelia

2007-04-15

The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on beta-FeOOH colloidal particles was investigated by means of electro-optics and electrophoresis. The films were built at different (acidic) pH in the absence of salt. We found that the thickness of the film grows linearly when the fully charged PLL (at pH 5.5) is combined with almost fully charged PGA (at pH 6.5), with a thickness of about 2 nm per single layer. When the fully charged PLL is combined with weakly charged PGA (at pH 4.5), the film thickness increases exponentially with the number of deposited layers. The thickness of the exponentially growing film increases to 300 nm after deposition of 16 layers. The exponential film growth is attributed to the ability of the PLL to diffuse "in" and "out" of the film bulk at each deposition step. The variation in the electrical polarizability of the film-coated particles was also monitored as a function of the number of adsorbed layers. The result reveals that the PLL chains, which can diffuse into the film bulk, have no measurable contribution to the electro-optical effect of the films terminated with PLL. It is only due to the polarization of counterions of the PLL adsorbed on the film surface.

Reliable recovery of the optical properties of multi-layer turbid media by iteratively using a layered diffusion model at multiple source-detector separations

PubMed Central

Liao, Yu-Kai; Tseng, Sheng-Hao

2014-01-01

Accurately determining the optical properties of multi-layer turbid media using a layered diffusion model is often a difficult task and could be an ill-posed problem. In this study, an iterative algorithm was proposed for solving such problems. This algorithm employed a layered diffusion model to calculate the optical properties of a layered sample at several source-detector separations (SDSs). The optical properties determined at various SDSs were mutually referenced to complete one round of iteration and the optical properties were gradually revised in further iterations until a set of stable optical properties was obtained. We evaluated the performance of the proposed method using frequency domain Monte Carlo simulations and found that the method could robustly recover the layered sample properties with various layer thickness and optical property settings. It is expected that this algorithm can work with photon transport models in frequency and time domain for various applications, such as determination of subcutaneous fat or muscle optical properties and monitoring the hemodynamics of muscle. PMID:24688828

Research on Materials and Components for Opto-Electronic Signal Processing and Computing.

DTIC Science & Technology

1986-12-30

structure consists of alternating layers of 100 A thick In 0 .12Ga 0 .88 As quan- tum wells and 150 A thick GaAs barriers, ten layers each. Nomarski optical...because it has six times as many quantum wells. 4 Electro-refraction was measured interferometrically as it was previously in bulk materials.(12) The

Extreme IR absorption in group IV-SiGeSn core-shell nanowires

NASA Astrophysics Data System (ADS)

Attiaoui, Anis; Wirth, Stephan; Blanchard-Dionne, André-Pierre; Meunier, Michel; Hartmann, J. M.; Buca, Dan; Moutanabbir, Oussama

2018-06-01

Sn-containing Si and Ge (Ge1-y-xSixSny) alloys are an emerging family of semiconductors with the potential to impact group IV material-based devices. These semiconductors provide the ability to independently engineer both the lattice parameter and bandgap, which holds the premise to develop enhanced or novel photonic and electronic devices. With this perspective, we present detailed investigations of the influence of Ge1-y-xSixSny layers on the optical properties of Si and Ge based heterostructures and nanowires. We found that by adding a thin Ge1-y-xSixSny capping layer on Si or Ge greatly enhances light absorption especially in the near infrared range, leading to an increase in short-circuit current density. For the Ge1-y-xSixSny structure at thicknesses below 30 nm, a 14-fold increase in the short-circuit current is observed with respect to bare Si. This enhancement decreases by reducing the capping layer thickness. Conversely, decreasing the shell thickness was found to improve the short-circuit current in Si/Ge1-y-xSixSny and Ge/Ge1-y-xSixSny core/shell nanowires. The optical absorption becomes very important by increasing the Sn content. Moreover, by exploiting an optical antenna effect, these nanowires show extreme light absorption, reaching an enhancement factor, with respect to Si or Ge nanowires, on the order of 104 in Si/Ge0.84Si0.04Sn0.12 and 12 in Ge/Ge0.84Si0.04Sn0.12. Furthermore, we analyzed the optical response after the addition of a dielectric layer of Si3N4 to the Si/Ge1-y-xSixSny core-shell nanowire and found approximatively a 50% increase in the short-circuit current density for a dielectric layer of thickness equal to 45 nm and both a core radius and a shell thickness greater than 40 nm. The core-shell optical antenna benefits from a multiplication of enhancements contributed by leaky mode resonances in the semiconductor part and antireflection effects in the dielectric part.

Effect of Indium nano-sandwiching on the structural and optical performance of ZnSe films

NASA Astrophysics Data System (ADS)

Al Garni, S. E.; Qasrawi, A. F.

In the current study, we attempted to explore the effects of the Indium nanosandwiching on the mechanical and optical properties of the physically evaporated ZnSe thin films by means of X-ray diffractions and ultraviolet spectrophotometry techniques. While the thickness of each layer of ZnSe was fixed at 1.0 μm, the thickness of the nanosandwiched Indium thin films was varied in the range of 25-100 nm. It was observed that the as grown ZnSe films exhibits cubic and hexagonal nature of crystallization as those of the ZnSe powders before the film deposition. The cubic phases weighs ∼70% of the structure. The analysis of this phases revealed that there is a systematic variation process presented by the decreasing of; the lattice constant, compressing strain, stress, stacking faults and dislocation intensity and increasing grain size resulted from increasing the Indium layer thickness in the range of 50-100 nm. In addition, the nanosandwiching of Indium between two layers of ZnSe is observed to enhance the absorbability of the ZnSe. Particularly, at incident photon energy of 2.38 eV the absorbability of the ZnSe films which are sandwiched with 100 nm Indium is increased by 13.8 times. Moreover, increasing the thickness of the Indium layer shrinks the optical energy band gap. These systematic variations in mechanical and optical properties are assigned to the better recrystallization process that is associated with Indium insertion which in turn allows total internal energy redistribution in the ZnSe films through the enlargement of grains.

Optical and structural characterisation of epitaxial nanoporous GaN grown by CVD.

PubMed

Mena, Josué; Carvajal, Joan J; Martínez, Oscar; Jiménez, Juan; Zubialevich, Vitaly Z; Parbrook, Peter J; Diaz, Francesc; Aguiló, Magdalena

2017-09-15

In this paper we study the optical properties of nanoporous gallium nitride (GaN) epitaxial layers grown by chemical vapour deposition on non-porous GaN substrates, using photoluminescence, cathodoluminescence, and resonant Raman scattering, and correlate them with the structural characteristic of these films. We pay special attention to the analysis of the residual strain of the layers and the influence of the porosity in the light extraction. The nanoporous GaN epitaxial layers are under tensile strain, although the strain is progressively reduced as the deposition time and the thickness of the porous layer increases, becoming nearly strain free for a thickness of 1.7 μm. The analysis of the experimental data point to the existence of vacancy complexes as the main source of the tensile strain.

A study on the optics of copper indium gallium (di)selenide (CIGS) solar cells with ultra-thin absorber layers.

PubMed

Xu, Man; Wachters, Arthur J H; van Deelen, Joop; Mourad, Maurice C D; Buskens, Pascal J P

2014-03-10

We present a systematic study of the effect of variation of the zinc oxide (ZnO) and copper indium gallium (di)selenide (CIGS) layer thickness on the absorption characteristics of CIGS solar cells using a simulation program based on finite element method (FEM). We show that the absorption in the CIGS layer does not decrease monotonically with its layer thickness due to interference effects. Ergo, high precision is required in the CIGS production process, especially when using ultra-thin absorber layers, to accurately realize the required thickness of the ZnO, cadmium sulfide (CdS) and CIGS layer. We show that patterning the ZnO window layer can strongly suppress these interference effects allowing a higher tolerance in the production process.

EFFECT OF INTRAVITREAL RANIBIZUMAB ON GANGLION CELL COMPLEX AND PERIPAPILLARY RETINAL NERVE FIBER LAYER IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION USING SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

PubMed

Zucchiatti, Ilaria; Cicinelli, Maria V; Parodi, Maurizio Battaglia; Pierro, Luisa; Gagliardi, Marco; Accardo, Agostino; Bandello, Francesco

2017-07-01

To analyze the changes in ganglion cell complex and peripapillary retinal nerve fiber layer thickness, in central macular thickness and choroidal thickness on spectral domain optical coherence tomography in patients with neovascular age-related macular degeneration treated with intravitreal ranibizumab injections. All consecutive patients with untreated neovascular age-related macular degeneration received loading phase of three monthly intravitreal ranibizumab, followed by retreatments on a pro re nata protocol for 12 months. changes in ganglion cell complex and retinal nerve fiber layer at the end of follow-up. Secondary outcome: changes in best-corrected visual acuity, central macular thickness, and choroidal thickness at the end of follow-up. Choroidal thickness was measured at 500 μm, 1000 μm, and 1,500 μm intervals nasally, temporally, superiorly, and inferiorly to the fovea, respectively, on horizontal and vertical line scans centered on the fovea. Twenty-four eyes were included. Ganglion cell complex and peripapillary retinal nerve fiber layer thickness did not show statistically significant changes through 12 months (55.6 ± 18.5 and 81.9 ± 9.9 μm at baseline, 52.7 ± 19.3 and 84.6 ± 15.5 μm at month 12, P > 0.05). Central macular thickness showed progressive decrease from baseline to month 12, with maximum reduction at month 3 (P < 0.001). Statistically significant reduction in choroidal thickness was registered in the nasal 500, 1000, and 1,500 μm from the fovea, corresponding to the papillomacular region (from 169.6 ± 45.3 to 153.9 ± 46.9, P < 0.001). Intravitreal ranibizumab injections did not affect retinal nerve fiber layer and ganglion cell complex thickness in 1-year follow-up. Choroidal thickness in papillomacular area and central macular thickness was significantly reduced at the end of treatment. Further studies, with larger sample, longer follow-up, and greater number of injections, are warranted.

Structure and strength at the bonding interface of a titanium-segmented polyurethane composite through 3-(trimethoxysilyl) propyl methacrylate for artificial organs.

PubMed

Sakamoto, Harumi; Doi, Hisashi; Kobayashi, Equo; Yoneyama, Takayuki; Suzuki, Yoshiaki; Hanawa, Takao

2007-07-01

The objective of this study was to investigate the structure and strength at the bonding interface of a titanium (Ti)-segmented polyurethane (SPU) composite through (3-trimethoxysilyl) propyl methacrylate (gamma-MPS) for artificial organs. The effects of the thickness of the gamma-MPS layer on the shear bonding strength between Ti and SPU were investigated. Ti disks were immersed in various concentrations of gamma-MPS solutions for several immersion times. The depth profiles of elements and the thickness of the gamma-MPS layer were determined by glow discharge optical emission spectroscopy and ellipsometry, respectively. The bonding stress at the Ti/gamma-MPS/SPU interface was evaluated with a shear bonding test. Furthermore, the fractured surface of a Ti-SPU composite was observed by optical microscopy and characterized using X-ray photoelectron spectroscopy. Consequently, the thickness of the gamma-MPS layer was controlled by the concentration of the gamma-MPS solution and immersion time. The shear bonding stress at the interface increased with the increase of the thickness of the gamma-MPS layer. Therefore, the control of the thickness of the gamma-MPS layer is significant to increase the shear bonding stress at the Ti/gamma-MPS/SPU interface. These results are significant to create composites for artificial organs consisting of other metals and polymers. Copyright 2007 Wiley Periodicals, Inc.

Measuring Thicknesses of Coatings on Metals

NASA Technical Reports Server (NTRS)

Cotty, Glenn M., Jr.

1986-01-01

Digital light sensor and eddy-current sensor measure thickness without contact. Surface of Coating reflects laser beam to optical sensor. Position of reflected spot on sensor used by microcomputer to calculate coating thickness. Eddy-current sensor maintains constant distance between optical sensor and metal substrate. When capabilities of available components fully exploited, instrument measures coatings from 0.001 to 6 in. (0.0025 to 15 cm) thick with accuracy of 1 part in 4,000. Instrument readily incorporated in automatic production and inspection systems. Used to inspect thermal-insulation layers, paint, and protective coatings. Also used to control application of coatings to preset thicknesses.

Nondestructive and in situ determination of graphene layers using optical fiber Fabry-Perot interference

NASA Astrophysics Data System (ADS)

Li, Cheng; Peng, Xiaobin; Liu, Qianwen; Gan, Xin; Lv, Ruitao; Fan, Shangchun

2017-02-01

Thickness measurement plays an important role for characterizing optomechanical behaviors of graphene. From the view of graphene-based Fabry-Perot (F-P) sensors, a simple, nondestructive and in situ method of determining the thickness of nanothick graphene membranes was demonstrated by using optical fiber F-P interference. Few-layer/multilayer graphene sheets were suspendedly adhered onto the endface of a ferrule with a 125 µm inner diameter by van der Waals interactions to construct micro F-P cavities. Along with the Fresnel’s law and complex index of refraction of the membrane working as a light reflector of an F-P interferometer, the optical reflectivity of graphene was modeled to investigate the effects of light wavelength and temperature. Then the average thickness of graphene membranes were extracted by F-P interference demodulation, and yielded a very strong cross-correlation coefficient of 99.95% with the experimental results observed by Raman spectrum and atomic force microscope. The method could be further extended for determining the number of layers of other 2D materials.

Cone Photoreceptor Packing Density and the Outer Nuclear Layer Thickness in Healthy Subjects

PubMed Central

Chui, Toco Y. P.; Song, Hongxin; Clark, Christopher A.; Papay, Joel A.; Burns, Stephen A.; Elsner, Ann E.

2012-01-01

Purpose. We evaluated the relationship between cone photoreceptor packing density and outer nuclear layer (ONL) thickness within the central 15 degrees. Methods. Individual differences for healthy subjects in cone packing density and ONL thickness were examined in 8 younger and 8 older subjects, mean age 27.2 versus 56.2 years. Cone packing density was obtained using an adaptive optics scanning laser ophthalmoscope (AOSLO). The ONL thickness measurements included the ONL and the Henle fiber layer (ONL + HFL), and were obtained using spectral domain optical coherence tomography (SDOCT) and custom segmentation software. Results. There were sizeable individual differences in cone packing density and ONL + HFL thickness. Older subjects had on average lower cone packing densities, but thicker ONL + HFL measurements. Cone packing density and ONL + HFL thickness decreased with increasing retinal eccentricity. The ratio of the cone packing density-to-ONL2 was larger for the younger subjects group, and decreased with retinal eccentricity. Conclusions. The individual differences in cone packing density and ONL + HFL thickness are consistent with aging changes, indicating that normative aging data are necessary for fine comparisons in the early stages of disease or response to treatment. Our finding of ONL + HFL thickness increasing with aging is inconsistent with the hypothesis that ONL measurements with SDOCT depend only on the number of functioning cones, since in our older group cones were fewer, but thickness was greater. PMID:22570340

Evaluation of Interocular Retinal Nerve Fiber Layer Thickness Symmetry as a Diagnostic Modality for Glaucoma.

PubMed

Hong, Seung Woo; Lee, Seung Bum; Jee, Dong-Hyun; Ahn, Myung Douk

2016-09-01

The purpose of study was to measure the diagnostic utility of interocular retinal nerve fiber layer (RNFL) symmetry and interocular RNFL thickness comparison. Both eyes of 103 normal subjects and 106 glaucoma patients (31 patients with early glaucoma and 75 patients with moderate to severe glaucoma) received comprehensive ophthalmologic evaluation including visual field testing and optic disc scanning using optical coherence tomography. RNFL thickness values for 256 measurement points were rearranged according to a new reference line connecting the optic disc center and the foveola. The interocular RNFL thickness symmetry value and absolute and fractional interocular difference in RNFL thickness were calculated and compared between groups. Area under the receiver operating characteristic curves (AUROCs) were calculated and compared. Among the parameters reflecting whole RNFL status, the corrected interocular RNFL thickness symmetry exhibited the largest AUROCs at all glaucoma stages. RNFL thickness and absolute and fractional interocular difference in RNFL thickness exhibited largest AUROC in the inferotemporal area, regardless of glaucoma stage. In the early glaucoma group, absolute and fractional interocular RNFL thickness differences in the temporal and superotemporal areas exhibited equal to or larger AUROCs than RNFL thickness. The AUROCs for RNFL thickness were greater than those for absolute and fractional interocular RNFL thickness differences in the moderate to severe glaucoma group except in the nasal and temporal area. The corrected interocular RNFL thickness symmetry value is an effective diagnostic tool for glaucoma. Interocular comparison of RNFL thickness has good diagnostic performance and gives information about the RNFL beyond just the RNFL thickness itself.

Advances in thickness measurements and dynamic visualization of the tear film using non-invasive optical approaches.

PubMed

Bai, Yuqiang; Nichols, Jason J

2017-05-01

The thickness of tear film has been investigated under both invasive and non-invasive methods. While invasive methods are largely historical, more recent noninvasive methods are generally based on optical approaches that provide accurate, precise, and rapid measures. Optical microscopy, interferometry, and optical coherence tomography (OCT) have been developed to characterize the thickness of tear film or certain aspects of the tear film (e.g., the lipid layer). This review provides an in-depth overview on contemporary optical techniques used in studying the tear film, including both advantages and limitations of these approaches. It is anticipated that further developments of high-resolution OCT and other interferometric methods will enable a more accurate and precise measurement of the thickness of the tear film and its related dynamic properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of Macular Ganglion Cell Complex and Peripapillary Retinal Nerve Fiber Layer in Primary Craniopharyngioma by Fourier-Domain Optical Coherence Tomography.

PubMed

Yang, Liu; Qu, Yuanzhen; Lu, Wen; Liu, Fengjun

2016-07-03

BACKGROUND The aim of this study was to compare the differences in macular ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (pRNFL) in child and adult patients with primary craniopharyngioma by Fourier-domain optical coherence tomography (FD-OCT) and to evaluate their significance in the diagnosis of primary craniopharyngioma. MATERIAL AND METHODS Ninety-six participants were divided into 3 groups: 32 in the child craniopharyngioma group (CCG) and 32 in the adult craniopharyngioma group (ACG) who were treated in Beijing Tiantan Hospital between November 2013 and October 2014, and 32 in the normal group (NG). All subjects were scanned by FD-OCT to map GCC and pRNFL thicknesses. Spearman correlation coefficient was used to assess the correlation between GCC and pRNFL thickness, and pRNFL thickness and optic nerve head (ONH) parameters, including horizontal cup-disc ratio (HCDR), vertical cup-disc ratio (VCDR), optic disc area (ODA), and cup area (CA), respectively. RESULTS The correlation between GCC and pRNFL thickness in the CCG was slightly stronger compared with the ACG. A significant difference in GCC thickness was observed among the CCG, ACG, and NG. Although the pRNFL thickness in both the CCG and ACG was significantly higher than that in NG, no significant difference in pRNFL thickness was detected between the 2 craniopharyngioma groups. The average, superior, and inferior pRNFL thicknesses were negatively correlated with VCDR in the CCG (in double eyes) and ACG (only in left eyes). CONCLUSIONS GCC was more sensitive than pRNFL in detecting optic nerve damage in the eyes of craniopharyngioma patients. A thinner pRNFL was especially correlated with VCDR in child craniopharyngioma patients.

Evaluation of Macular Ganglion Cell Complex and Peripapillary Retinal Nerve Fiber Layer in Primary Craniopharyngioma by Fourier-Domain Optical Coherence Tomography

PubMed Central

Yang, Liu; Qu, Yuanzhen; Lu, Wen; Liu, Fengjun

2016-01-01

Background The aim of this study was to compare the differences in macular ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (pRNFL) in child and adult patients with primary craniopharyngioma by Fourier-domain optical coherence tomography (FD-OCT) and to evaluate their significance in the diagnosis of primary craniopharyngioma. Material/Methods Ninety-six participants were divided into 3 groups: 32 in the child craniopharyngioma group (CCG) and 32 in the adult craniopharyngioma group (ACG) who were treated in Beijing Tiantan Hospital between November 2013 and October 2014, and 32 in the normal group (NG). All subjects were scanned by FD-OCT to map GCC and pRNFL thicknesses. Spearman correlation coefficient was used to assess the correlation between GCC and pRNFL thickness, and pRNFL thickness and optic nerve head (ONH) parameters, including horizontal cup-disc ratio (HCDR), vertical cup-disc ratio (VCDR), optic disc area (ODA), and cup area (CA), respectively. Results The correlation between GCC and pRNFL thickness in the CCG was slightly stronger compared with the ACG. A significant difference in GCC thickness was observed among the CCG, ACG, and NG. Although the pRNFL thickness in both the CCG and ACG was significantly higher than that in NG, no significant difference in pRNFL thickness was detected between the 2 craniopharyngioma groups. The average, superior, and inferior pRNFL thicknesses were negatively correlated with VCDR in the CCG (in double eyes) and ACG (only in left eyes). Conclusions GCC was more sensitive than pRNFL in detecting optic nerve damage in the eyes of craniopharyngioma patients. A thinner pRNFL was especially correlated with VCDR in child craniopharyngioma patients. PMID:27372909

Analysis of reflectance spectra of UV-absorbing aerosol scenes measured by SCIAMACHY

NASA Astrophysics Data System (ADS)

de Graaf, M.; Stammes, P.; Aben, E. A. A.

2007-01-01

Reflectance spectra from 280-1750 nm of typical desert dust aerosol (DDA) and biomass burning aerosol (BBA) scenes over oceans are presented, measured by the space-borne spectrometer Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). DDA and BBA are both UV-absorbing aerosols, but their effect on the top-of-atmosphere (TOA) reflectance is different due to differences in the way mineral aerosols and smoke reflect and absorb radiation. Mineral aerosols are typically large, inert particles, found in warm, dry continental air. Smoke particles, on the other hand, are usually small particles, although often clustered, chemically very active and highly variable in composition. Moreover, BBA are hygroscopic and over oceans BBA were invariably found in cloudy scenes. TOA reflectance spectra of typical DDA and BBA scenes were analyzed, using radiative transfer simulations, and compared. The DDA spectrum was successfully simulated using a layer with a bimodal size distribution of mineral aerosols in a clear sky. The spectrum of the BBA scene, however, was determined by the interaction between cloud droplets and smoke particles, as is shown by simulations with a model of separate aerosol and cloud layers and models with internally and externally mixed aerosol/cloud layers. The occurrence of clouds in smoke scenes when sufficient water vapor is present usually prevents the detection of optical properties of these aerosol plumes using space-borne sensors. However, the Absorbing Aerosol Index (AAI), a UV color index, is not sensitive to scattering aerosols and clouds and can be used to detect these otherwise obscured aerosol plumes over clouds. The amount of absorption of radiation can be expressed using the absorption optical thickness. The absorption optical thickness in the DDA case was 0.42 (340 nm) and 0.14 (550 nm) for an aerosol layer of optical thickness 1.74 (550 nm). In the BBA case the absorption optical thickness was 0.18 (340 nm) and 0.10 (550 nm) for an aerosol/cloud layer of optical thickness 20.0 (550 nm). However, this reduced the cloud albedo by about 0.2 (340 nm) and 0.15 (550 nm). This method can be an important tool to estimate the global impact of absorption of shortwave radiation by smoke and industrial aerosols inside clouds.

Thermal stress prediction in mirror and multilayer coatings.

PubMed

Cheng, Xianchao; Zhang, Lin; Morawe, Christian; Sanchez Del Rio, Manuel

2015-03-01

Multilayer optics for X-rays typically consist of hundreds of periods of two types of alternating sub-layers which are coated on a silicon substrate. The thickness of the coating is well below 1 µm (tens or hundreds of nanometers). The high aspect ratio (∼10(7)) between the size of the optics and the thickness of the multilayer can lead to a huge number of elements (∼10(16)) for the numerical simulation (by finite-element analysis using ANSYS code). In this work, the finite-element model for thermal-structural analysis of multilayer optics has been implemented using the ANSYS layer-functioned elements. The number of meshed elements is considerably reduced and the number of sub-layers feasible for the present computers is increased significantly. Based on this technique, single-layer coated mirrors and multilayer monochromators cooled by water or liquid nitrogen are studied with typical parameters of heat-load, cooling and geometry. The effects of cooling-down of the optics and heating of the X-ray beam are described. It is shown that the influences from the coating on temperature and deformation are negligible. However, large stresses are induced in the layers due to the different thermal expansion coefficients between the layer and the substrate materials, which is the critical issue for the survival of the optics. This is particularly true for the liquid-nitrogen cooling condition. The material properties of thin multilayer films are applied in the simulation to predict the layer thermal stresses with more precision.

Approximate Solution Methods for Spectral Radiative Transfer in High Refractive Index Layers

NASA Technical Reports Server (NTRS)

Siegel, R.; Spuckler, C. M.

1994-01-01

Some ceramic materials for high temperature applications are partially transparent for radiative transfer. The refractive indices of these materials can be substantially greater than one which influences internal radiative emission and reflections. Heat transfer behavior of single and laminated layers has been obtained in the literature by numerical solutions of the radiative transfer equations coupled with heat conduction and heating at the boundaries by convection and radiation. Two-flux and diffusion methods are investigated here to obtain approximate solutions using a simpler formulation than required for exact numerical solutions. Isotropic scattering is included. The two-flux method for a single layer yields excellent results for gray and two band spectral calculations. The diffusion method yields a good approximation for spectral behavior in laminated multiple layers if the overall optical thickness is larger than about ten. A hybrid spectral model is developed using the two-flux method in the optically thin bands, and radiative diffusion in bands that are optically thick.

Ultrasound-guided near-infrared spectroscopy for brain functional study: feasibility analysis and preliminary work

NASA Astrophysics Data System (ADS)

Xu, Ronald; Qiang, Bo; Liu, Jun

2005-04-01

Recent advances in diffuse optical imaging and spectroscopy (DOIS) allow the noninvasive measurement of local changes in cerebral oxygenation and hemodynamics. Available DOIS devices fall into three categories: time domain (TD), frequency domain (FD) and continuous wave (CW). The TD and FD devices have potential for high spatial resolution, high temporal resolution and high accuracy measurement, but the instrument cost and the hardware size prevent their wide clinical application. Furthermore, the presence of the low scattering cerebrospinal fluid layer (CSF) and its thickness variation during motion challenges quantitative, continuous monitoring of the cortex layer oxygenation and blood content. MRI has been used to provide a priori knowledge of the head anatomy that helps the NIR image reconstruction. However, the technology is expensive and lacks portability. This paper proposes a method that combines the accuracy of a TD/FD system and the portability of a CW device. With the optical baseline measured by a TD or FD device and the layer thickness characterized by an ultrasound transducer, a conventional CW system may be able to quantify the cortex layer optical absorption with high accuracy. In this paper, the feasibility of using ultrasound guided CW spectroscopy to monitor brain activities was studied on a multi layer head model using Monte Carlo simulation and order of magnitude analysis. A forward algorithm based on diffuse approximation and 2D Fourier Transform was used to optimize the source detector separation. Both analytical and neuron network approaches were developed for inverse calculation of the cortex layer absorption in real time. An ultrasound transducer was used to monitor the thickness of different layers surrounding the cerebral cortex. The concept of ultrasound guided CW spectroscopy was demonstrated by numerical simulation on a 2 layer head model and the use of the ultrasound transducer for layer thickness characterization was verified by animal and bench top results.

Lear jet boundary layer/shear layer laser propagation experiments

NASA Technical Reports Server (NTRS)

Gilbert, K.

1980-01-01

Optical degradations of aircraft turbulent boundary layers with shear layers generated by aerodynamic fences are analyzed. A collimated 2.5 cm diameter helium-neon laser (0.63 microns) traversed the approximate 5 cm thick natural aircraft boundary layer in double pass via a reflective airfoil. In addition, several flights examined shear layer-induced optical degradation. Flight altitudes ranged from 1.5 to 12 km, while Mach numbers were varied from 0.3 to 0.8. Average line spread function (LSF) and Modulation Transfer Function (MTF) data were obtained by averaging a large number of tilt-removed curves. Fourier transforming the resulting average MTF yields an LSF, thus affording a direct comparison of the two optical measurements. Agreement was good for the aerodynamic fence arrangement, but only fair in the case of a turbulent boundary layer. Values of phase variance inferred from the LSF instrument for a single pass through the random flow and corrected for a large aperture ranged from 0.08 to 0.11 waves (lambda = .63 microns) for the boundary layer. Corresponding values for the fence vary from 0.08 to 0.16 waves. Extrapolation of these values to 10.6 microns suggests negligible degradation for a CO2 laser transmitted through a 5 cm thick, subsonic turbulent boundary layer.

Evaluation of retinal nerve fiber layer thickness profile in thyroid ophthalmopathy without optic nerve dysfunction

PubMed Central

Mugdha, Kumari; Kaur, Apjit; Sinha, Neha; Saxena, Sandeep

2016-01-01

AIM To evaluate retinal nerve fiber layer (RNFL) thickness profile in patients of thyroid ophthalmopathy with no clinical signs of optic nerve dysfunction. METHODS A prospective, case-control, observational study conducted at a tertiary care centre. Inclusion criteria consisted of patients with eyelid retraction in association with any one of: biochemical thyroid dysfunction, exophthalmos, or extraocular muscle involvement; or thyroid dysfunction in association with either exophthalmos or extra-ocular muscle involvement; or a clinical activity score (CAS)>3/7. Two measurements of RNFL thickness were done for each eye, by Cirrus HD-optical coherence tomography 6mo apart. RESULTS Mean age of the sample was 38.75y (range 13-70y) with 18 males and 22 females. Average RNFL thickness at first visit was 92.06±12.44 µm, significantly lower than control group (101.28±6.64 µm) (P=0.0001). Thickness of inferior quadrant decreased from 118.2±21.27 µm to 115.0±22.27 µm after 6mo (P=0.02). There was no correlation between the change in CAS and RNFL thickness. CONCLUSION Decreased RNFL thickness is an important feature of thyroid orbitopathy, which is an inherent outcome of compressive optic neuropathy of any etiology. Subclinical RNFL damage continues in the absence of clinical activity of the disease. RNFL evaluation is essential in Grave's disease and active intervention may be warranted in the presence of significant damage. PMID:27990368

Enhancement of carrier lifetimes in type-II quantum dot/quantum well hybrid structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Couto, O. D. D., E-mail: odilon@ifi.unicamp.br; Almeida, P. T. de; Santos, G. E. dos

We investigate optical transitions and carrier dynamics in hybrid structures containing type-I GaAs/AlGaAs quantum wells (QWs) and type-II GaSb/AlGaAs quantum dots (QDs). We show that the optical recombination of photocreated electrons confined in the QWs with holes in the QDs and wetting layer can be modified according to the QW/QD spatial separation. In particular, for low spacer thicknesses, the QW optical emission can be suppressed due to the transference of holes from the QW to the GaSb layer, favoring the optical recombination of spatially separated carriers, which can be useful for optical memory and solar cell applications. Time-resolved photoluminescence (PL)more » measurements reveal non-exponential recombination dynamics. We demonstrate that the PL transients can only be quantitatively described by considering both linear and quadratic terms of the carrier density in the bimolecular recombination approximation for type-II semiconductor nanostructures. We extract long exciton lifetimes from 700 ns to 5 μs for QDs depending on the spacer layer thickness.« less

Spatial coherence effect on layer thickness determination in narrowband full-field optical coherence tomography.

PubMed

Safrani, Avner; Abdulhalim, Ibrahim

2011-06-20

Longitudinal spatial coherence (LSC) is determined by the spatial frequency content of an optical beam. The use of lenses with a high numerical aperture (NA) in full-field optical coherence tomography and a narrowband light source makes the LSC length much shorter than the temporal coherence length, hence suggesting that high-resolution 3D images of biological and multilayered samples can be obtained based on the low LSC. A simplified model is derived, supported by experimental results, which describes the expected interference output signal of multilayered samples when high-NA lenses are used together with a narrowband light source. An expression for the correction factor for the layer thickness determination is found valid for high-NA objectives. Additionally, the method was applied to a strongly scattering layer, demonstrating the potential of this method for high-resolution imaging of scattering media.

Growth mechanism, surface and optical properties of ZnO nanostructures deposited on various Au-seeded thickness obtained by mist-atomization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afaah, A. N., E-mail: afaahabdullah@yahoo.com; Aadila, A., E-mail: aadilaazizali@gmail.com; Asib, N. A. M., E-mail: amierahasib@yahoo.com

2016-07-06

In this paper, growth mechanisms of ZnO nanostructures on non-seeded glass, 6 nm and 12 nm Au seed layer obtained by mist-atomization was proposed. ZnO films were successfully deposited on glass substrate with different thickness of Au seed layer i.e. 6 nm and 12 nm. The surface and optical properties of the prepared samples were investigated using Field emission scanning electron microscopy (FESEM) and photoluminescence (PL). FESEM micrograph show that ZnO nanostructure deposited on 6 nm Au seed layer has uniform formation and well distributed. From PL spectroscopy, the UV emission shows that ZnO deposited on 6 nm Au seedmore » layer has the more intense UV intensity which proved that high crystal quality of nanostructured ZnO deposited on 6 nm Au seed layer.« less

Comparison of spectral-domain optical coherence tomography for intra-retinal layers thickness measurements between healthy and diabetic eyes among Chinese adults

PubMed Central

Li, Shu-ting; Wang, Xiang-ning; Du, Xin-hua; Wu, Qiang

2017-01-01

Purpose To compare intra-retinal layer thickness measurements between eyes with no or mild diabetic retinopathy (DR) and age-matched controls using Spectralis spectral-domain optical coherence tomography (SD-OCT). Methods Cross-sectional observational analysis study. High-resolution macular volume scans (30° * 25°) were obtained for 133 type 2 diabetes mellitus (T2DM) patients with no DR, 42 T2DM patients with mild DR and 115 healthy controls. The mean thickness was measured in all 9 Early Treatment Diabetic Retinopathy Study (ETDRS) sectors for 8 separate layers, inner retinal layer (IRL), outer retinal layer (ORL) and total retina (TR), after automated segmentation. The ETDRS grid consisted of three concentric circles of 1-, 3-, and 6-mm diameter. The superior, inferior, temporal, and nasal sectors of the 3- and 6-mm circles were respectively designated as S3, I3, T3, and N3 and S6, I6, T6, and N6. Linear regression analyses were conducted to evaluate the associations between the intra-retinal layer thicknesses, age, diabetes duration, fasting blood glucose and HbA1c. Results The mean age and duration of T2DM were 61.1 and 13.7 years, respectively. Although no significant differences in the average TR and ORL volumes were observed among the groups, significant differences were found in the volume and sectorial thicknesses of the inner plexiform layer (IPL), outer plexiform layer (OPL) and IRL among the groups. In particular, the thicknesses of the IPL (S3, T3, S6, I6 and T6 sectors) and the IRL (S6 sector) were decreased in the no-DR group compared with the controls (P < 0.05). The thickness of the OPL (S3, N3, S6 and N6 sectors) was thinner in the no-DR group than in mild DR (P < 0.05). The average IPL thickness was significantly negatively correlated with age and the duration of diabetes. Conclusion The assessment of the intra-retinal layer thickness showed a significant decrease in the IPL and IRL thicknesses in Chinese adults with T2DM, even in the absence of visible microvascular signs of DR. PMID:28493982

Changing the thickness of two layers: i-ZnO nanorods, p-Cu2O and its influence on the carriers transport mechanism of the p-Cu2O/i-ZnO nanorods/n-IGZO heterojunction.

PubMed

Ke, Nguyen Huu; Trinh, Le Thi Tuyet; Phung, Pham Kim; Loan, Phan Thi Kieu; Tuan, Dao Anh; Truong, Nguyen Huu; Tran, Cao Vinh; Hung, Le Vu Tuan

2016-01-01

In this study, two layers: i-ZnO nanorods and p-Cu2O were fabricated by electrochemical deposition. The fabricating process was the initial formation of ZnO nanorods layer on the n-IGZO thin film which was prepared by sputtering method, then a p-Cu2O layer was deposited on top of rods to form the p-Cu2O/i-ZnO nanorods/n-ZnO heterojunction. The XRD, SEM, UV-VIS, I-V characteristics methods were used to define structure, optical and electrical properties of these heterojunction layers. The fabricating conditions and thickness of the Cu2O layers significantly affected to the formation, microstructure, electrical and optical properties of the junction. The length of i-ZnO nanorods layer in the structure of the heterojunction has strongly affected to the carriers transport mechanism and performance of this heterojunction.

Importance of molecular Rayleigh scattering in the enhancement of clear sky reflectance in the vicinity of boundary layer cumulus clouds

NASA Astrophysics Data System (ADS)

Wen, Guoyong; Marshak, Alexander; Cahalan, Robert F.

2008-12-01

Clouds increase the complexity of atmospheric radiative transfer processes, particularly for aerosol retrievals in clear regions in the vicinity of clouds. This study focuses on identifying mechanisms responsible for the enhancement of nadir reflectance in clear regions in the vicinity of cumulus clouds and quantifies the relative importance of each mechanism. Using cloud optical properties and surface albedo derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Moderate Resolution Imaging Spectroradiometer (MODIS), we performed extensive Monte Carlo simulations of radiative transfer in two cumulus scenes in a biomass burning region in Brazil. The results show that the scattering of radiation by clouds, followed by upward Rayleigh scattering by molecules above cloud top over clear gaps, is the dominant mechanism for the enhancement of visible reflectance in clear regions in boundary layer cumulus field over dark surfaces with aerosols trapped in the boundary layer. The Rayleigh scattering contributes ˜80% and ˜50% to the total enhancement for wavelengths 0.47 μm (with aerosol optical thickness 0.2) and 0.66 μm (with aerosol optical thickness 0.1), respectively. Out of the total contribution of molecular scattering, ˜90% arises from the clear atmosphere above cloud top height. The mechanism is valid for a large range of aerosol optical thicknesses (up to 1 in this study) for 0.47 μm, and for aerosol optical thickness up to 0.2 for 0.66 μm. Our results provide a basis to develop simplifications for future aerosol remote sensing from satellite.

Electrically Addressable Optical Devices Using A System Of Composite Layered Flakes Suspended In A Fluid Host To Obtain Angularly Depende

DOEpatents

Kosc, Tanya Z.; Marshall, Kenneth L.; Jacobs, Stephen D.

2004-12-07

Composite or layered flakes having a plurality of layers of different materials, which may be dielectric materials, conductive materials, or liquid crystalline materials suspended in a fluid host and subjected to an electric field, provide optical effects dependent upon the angle or orientation of the flakes in the applied electric field. The optical effects depend upon the composition and thickness of the layers, producing reflectance, interference, additive and/or subtractive color effects. The composition of layered flakes may also be selected to enhance and/or alter the dielectric properties of flakes, whereby flake motion in an electric field is also enhanced and/or altered. The devices are useful as active electro-optical displays, polarizers, filters, light modulators, and wherever controllable polarizing, reflecting and transmissive optical properties are desired.

Relationship between white matter hyperintensities and retinal nerve fiber layer, choroid, and ganglion cell layer thickness in migraine patients.

PubMed

Iyigundogdu, Ilkin; Derle, Eda; Asena, Leyla; Kural, Feride; Kibaroglu, Seda; Ocal, Ruhsen; Akkoyun, Imren; Can, Ufuk

2018-02-01

Aim To compare the relationship between white matter hyperintensities (WMH) on brain magnetic resonance imaging and retinal nerve fiber layer (RNFL), choroid, and ganglion cell layer (GCL) thicknesses in migraine patients and healthy subjects. We also assessed the role of cerebral hypoperfusion in the formation of these WMH lesions. Methods We enrolled 35 migraine patients without WMH, 37 migraine patients with WMH, and 37 healthy control subjects examined in the Neurology outpatient clinic of our tertiary center from May to December 2015. RFNL, choroid, and GCL thicknesses were measured by optic coherence tomography. Results There were no differences in the RFNL, choroid, or GCL thicknesses between migraine patients with and without WMH ( p > 0.05). Choroid layer thicknesses were significantly lower in migraine patients compared to control subjects ( p < 0.05), while there were no differences in RFNL and GCL thicknesses ( p > 0.05). Conclusions The 'only cerebral hypoperfusion' theory was insufficient to explain the pathophysiology of WMH lesions in migraine patients. In addition, the thinning of the choroid thicknesses in migraine patients suggests a potential causative role for cerebral hypoperfusion and decreased perfusion pressure of the choroid layer.

Angiographic and structural imaging using high axial resolution fiber-based visible-light OCT

PubMed Central

Pi, Shaohua; Camino, Acner; Zhang, Miao; Cepurna, William; Liu, Gangjun; Huang, David; Morrison, John; Jia, Yali

2017-01-01

Optical coherence tomography using visible-light sources can increase the axial resolution without the need for broader spectral bandwidth. Here, a high-resolution, fiber-based, visible-light optical coherence tomography system is built and used to image normal retina in rats and blood vessels in chicken embryo. In the rat retina, accurate segmentation of retinal layer boundaries and quantification of layer thicknesses are accomplished. Furthermore, three distinct capillary plexuses in the retina and the choriocapillaris are identified and the characteristic pattern of the nerve fiber layer thickness in rats is revealed. In the chicken embryo model, the microvascular network and a venous bifurcation are examined and the ability to identify and segment large vessel walls is demonstrated. PMID:29082087

Fiber Optic Couplers.

DTIC Science & Technology

1979-11-01

over a 1 x 4 inch glass plate. A further problem has been that the surface over the ion diffused region is submerged 2 pm below that of the substrate...of varying mask openings (35, 45, 55, 65, 78, 85 pm ). The ion exchange processing time was varied using 20, 25, 35 and 40 minutes. We found that the...pattern is then overcoated with a thick layer of SiO 2 (lO0 pm thick). This thick layer and the SiO 2 substrate thus com- pletely surround the dopant

Multi-layer coatings

DOEpatents

Maghsoodi, Sina; Brophy, Brenor L.; Abrams, Ze'ev R.; Gonsalves, Peter R.

2016-06-28

Disclosed herein are coating materials and methods for applying a top-layer coating that is durable, abrasion resistant, highly transparent, hydrophobic, low-friction, moisture-sealing, anti-soiling, and self-cleaning to an existing conventional high temperature anti-reflective coating. The top coat imparts superior durability performance and new properties to the under-laying conventional high temperature anti-reflective coating without reducing the anti-reflectiveness of the coating. Methods and data for optimizing the relative thickness of the under-layer high temperature anti-reflective coating and the top-layer thickness for optimizing optical performance are also disclosed.

Multispectral surface plasmon resonance approach for ultra-thin silver layer characterization: Application to top-emitting OLED cathode

NASA Astrophysics Data System (ADS)

Taverne, S.; Caron, B.; Gétin, S.; Lartigue, O.; Lopez, C.; Meunier-Della-Gatta, S.; Gorge, V.; Reymermier, M.; Racine, B.; Maindron, T.; Quesnel, E.

2018-01-01

While dielectric/metal/dielectric (DMD) multilayer thin films have raised considerable interest as transparent and conductive electrodes in various optoelectronic devices, the knowledge of optical characteristics of thin metallic layers integrated in such structures is still rather approximate. The multispectral surface plasmon resonance characterization approach described in this work precisely aims at providing a rigorous methodology able to accurately determine the optical constants of ultra-thin metallic films. As a practical example, the refractive index and extinction dispersion curves of 8 to 25 nm-thick silver layers have been investigated. As a result, their extreme dependence on the layer thickness is highlighted, in particular in a thickness range close to the critical threshold value (˜10 nm) where the silver film becomes continuous and its electrical conductance/optical transmittance ratio particularly interesting. To check the validity of the revisited Ag layers constant dispersion curves deduced from this study, they were introduced into a commercial optical model software to simulate the behavior of various optoelectronic building blocks from the simplest ones (DMD electrodes) to much more complex structures [full organic light emitting device (OLED) stacks]. As a result, a much better prediction of the emission spectrum profile as well as the angular emission pattern of top-emitting OLEDs is obtained. On this basis, it is also shown how a redesign of the top encapsulation thin film of OLEDs is necessary to better take benefit from the advanced DMD electrode. These results should particularly interest the micro-OLED display field where bright and directive single color pixel emission is required.

Microstructure-Dependent Visible-Light Driven Photoactivity of Sputtering-Assisted Synthesis of Sulfide-Based Visible-Light Sensitizer onto ZnO Nanorods

PubMed Central

Liang, Yuan-Chang; Chung, Cheng-Chia; Lo, Ya-Ju; Wang, Chein-Chung

2016-01-01

The ZnO-CdS core-shell composite nanorods with CdS shell layer thicknesses of 5 and 20 nm were synthesized by combining the hydrothermal growth of ZnO nanorods with the sputtering thin-film deposition of CdS crystallites. The microstructures and optical properties of the ZnO-CdS nanorods were associated with the CdS shell layer thickness. A thicker CdS shell layer resulted in a rougher surface morphology, more crystal defects, and a broader optical absorbance edge in the ZnO-CdS rods. The ZnO-CdS (20 nm) nanorods thus engaged in more photoactivity in this study. When they were further subjected to a postannealing procedure in ambient Ar/H2, this resulted in the layer-like CdS shell layers being converted into the serrated CdS shell layers. By contrast, the ZnO-CdS nanorods conducted with the postannealing procedure exhibited superior photoactivity and photoelectrochemical performance; the substantial changes in the microstructures and optical properties of the composite nanorods following postannealing in this study might account for the observed results. PMID:28774134

Ultrathin phase-change coatings on metals for electrothermally tunable colors

NASA Astrophysics Data System (ADS)

Bakan, Gokhan; Ayas, Sencer; Saidzoda, Tohir; Celebi, Kemal; Dana, Aykutlu

2016-08-01

Metal surfaces coated with ultrathin lossy dielectrics enable color generation through strong interferences in the visible spectrum. Using a phase-change thin film as the coating layer offers tuning the generated color by crystallization or re-amorphization. Here, we study the optical response of surfaces consisting of thin (5-40 nm) phase-changing Ge2Sb2Te5 (GST) films on metal, primarily Al, layers. A color scale ranging from yellow to red to blue that is obtained using different thicknesses of as-deposited amorphous GST layers turns dim gray upon annealing-induced crystallization of the GST. Moreover, when a relatively thick (>100 nm) and lossless dielectric film is introduced between the GST and Al layers, optical cavity modes are observed, offering a rich color gamut at the expense of the angle independent optical response. Finally, a color pixel structure is proposed for ultrahigh resolution (pixel size: 5 × 5 μm2), non-volatile displays, where the metal layer acting like a mirror is used as a heater element. The electrothermal simulations of such a pixel structure suggest that crystallization and re-amorphization of the GST layer using electrical pulses are possible for electrothermal color tuning.

Polishability of thin electrolytic and electroless NiP layers

NASA Astrophysics Data System (ADS)

Kinast, Jan; Beier, Matthias; Gebhardt, Andreas; Risse, Stefan; Tünnermann, Andreas

2015-10-01

Ultra-precise metal optics are key components of sophisticated scientific instrumentation in astronomy and space applications, covering a wide spectral range. Especially for applications in the visible or ultra-violet spectral ranges, a low roughness of the optics is required. Therefore, a polishable surface is necessary. State of the art is an amorphous nickel-phosphorus (NiP) layer, which enables several polishing techniques achieving a roughness of <1 nm RMS. Typically, these layers are approximately 30 μm to 60 μm thick. Deposited on Al6061, the bimetallic effect leads to a restricted operational temperature, caused by different coefficients of thermal expansion of Al6061 and NiP. Thinner NiP layers reduce the bimetallic effect. Hence, the possible operating temperature range. A deterministic shape correction via Magnetorheological Finishing of the substrate Al6061 leads to low shape deviations prior to the NiP deposition. This allows for depositing thin NiP-layers, which are polishable via a chemical mechanical polishing technique aiming at ultra-precise metal optics. The present article shows deposition processes and polishability of electroless and electrolytic NiP layers with thicknesses between 1 μm and 10 μm.

Work Function Variations in Twisted Graphene Layers

DOE PAGES

Robinson, Jeremy T.; Culbertson, James; Berg, Morgann; ...

2018-01-31

By combining optical imaging, Raman spectroscopy, kelvin probe force microscopy (KFPM), and photoemission electron microscopy (PEEM), we show that graphene’s layer orientation, as well as layer thickness, measurably changes the surface potential (Φ). Detailed mapping of variable-thickness, rotationally-faulted graphene films allows us to correlate Φ with specific morphological features. Using KPFM and PEEM we measure ΔΦ up to 39 mV for layers with different twist angles, while ΔΦ ranges from 36–129 mV for different layer thicknesses. The surface potential between different twist angles or layer thicknesses is measured at the KPFM instrument resolution of ≤ 200 nm. The PEEM measuredmore » work function of 4.4 eV for graphene is consistent with doping levels on the order of 10 12cm -2. Here, we find that Φ scales linearly with Raman G-peak wavenumber shift (slope = 22.2 mV/cm -1) for all layers and twist angles, which is consistent with doping-dependent changes to graphene’s Fermi energy in the ‘high’ doping limit. Our results here emphasize that layer orientation is equally important as layer thickness when designing multilayer two-dimensional systems where surface potential is considered.« less

Work Function Variations in Twisted Graphene Layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Jeremy T.; Culbertson, James; Berg, Morgann

By combining optical imaging, Raman spectroscopy, kelvin probe force microscopy (KFPM), and photoemission electron microscopy (PEEM), we show that graphene’s layer orientation, as well as layer thickness, measurably changes the surface potential (Φ). Detailed mapping of variable-thickness, rotationally-faulted graphene films allows us to correlate Φ with specific morphological features. Using KPFM and PEEM we measure ΔΦ up to 39 mV for layers with different twist angles, while ΔΦ ranges from 36–129 mV for different layer thicknesses. The surface potential between different twist angles or layer thicknesses is measured at the KPFM instrument resolution of ≤ 200 nm. The PEEM measuredmore » work function of 4.4 eV for graphene is consistent with doping levels on the order of 10 12cm -2. Here, we find that Φ scales linearly with Raman G-peak wavenumber shift (slope = 22.2 mV/cm -1) for all layers and twist angles, which is consistent with doping-dependent changes to graphene’s Fermi energy in the ‘high’ doping limit. Our results here emphasize that layer orientation is equally important as layer thickness when designing multilayer two-dimensional systems where surface potential is considered.« less

Relationship Between Optic Nerve Appearance and Retinal Nerve Fiber Layer Thickness as Explored with Spectral Domain Optical Coherence Tomography

PubMed Central

Aleman, Tomas S.; Huang, Jiayan; Garrity, Sean T.; Carter, Stuart B.; Aleman, Wendy D.; Ying, Gui-shuang; Tamhankar, Madhura A.

2014-01-01

Purpose To study the relationship between the appearance of the optic nerve and the retinal nerve fiber layer (RNFL) thickness determined by spectral domain optical coherence tomography (OCT). Methods Records from patients with spectral domain-OCT imaging in a neuro-ophthalmology practice were reviewed. Eyes with glaucoma/glaucoma suspicion, macular/optic nerve edema, pseudophakia, and with refractive errors > 6D were excluded. Optic nerve appearance by slit lamp biomicroscopy was related to the RNFL thickness by spectral domain-OCT and to visual field results. Results Ninety-one patients (176 eyes; mean age: 49 ± 15 years) were included. Eighty-three eyes (47%) showed optic nerve pallor; 89 eyes (50.6%) showed RNFL thinning (sectoral or average peripapillary). Average peripapillary RNFL thickness in eyes with pallor (mean ± SD = 76 ± 17 μm) was thinner compared to eyes without pallor (91 ± 14 μm, P < 0.001). Optic nerve pallor predicted RNFL thinning with a sensitivity of 69% and a specificity of 75%. Optic nerve appearance predicted RNFL thinning (with a sensitivity and specificity of 81%) when RNFL had thinned by ∼ 40%. Most patients with pallor had RNFL thinning with (66%) or without (25%) visual field loss; the remainder had normal RNFL and fields (5%) or with visual field abnormalities (4%). Conclusions Optic nerve pallor as a predictor of RNFL thinning showed fair sensitivity and specificity, although it is optimally sensitive/specific only when substantial RNFL loss has occurred. Translational Relevance Finding an acceptable relationship between the optic nerve appearance by ophthalmoscopy and spectral domain-OCT RNFL measures will help the clinician's interpretation of the information provided by this technology, which is gaining momentum in neuro-ophthalmic research. PMID:25374773

Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

NASA Astrophysics Data System (ADS)

Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

2018-01-01

Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

Enhancement of absorption and color contrast in ultra-thin highly absorbing optical coatings

NASA Astrophysics Data System (ADS)

Kats, Mikhail A.; Byrnes, Steven J.; Blanchard, Romain; Kolle, Mathias; Genevet, Patrice; Aizenberg, Joanna; Capasso, Federico

2013-09-01

Recently a new class of optical interference coatings was introduced which comprises ultra-thin, highly absorbing dielectric layers on metal substrates. We show that these lossy coatings can be augmented by an additional transparent subwavelength layer. We fabricated a sample comprising a gold substrate, an ultra-thin film of germanium with a thickness gradient, and several alumina films. The experimental reflectivity spectra showed that the additional alumina layer increases the color range that can be obtained, in agreement with calculations. More generally, this transparent layer can be used to enhance optical absorption, protect against erosion, or as a transparent electrode for optoelectronic devices.

Flexible IZO/Ag/IZO/Ag multilayer electrode grown on a polyethylene terephthalate substrate using roll-to-roll sputtering

PubMed Central

2012-01-01

We investigated the optical, electrical, structural, and surface properties of roll-to-roll [R2R] sputter-grown flexible IZO/Ag/IZO/Ag [IAIA] multilayer films on polyethylene terephthalate substrates as a function of the top indium zinc oxide [IZO] thickness. It was found that the optical transmittance of the IAIA multilayer was significantly influenced by the top IZO layer thickness, which was grown on identical AIA multilayers. However, the sheet resistance of the IAIA multilayer was maintained between the range 5.01 to 5.1 Ω/square regardless of the top IZO thickness because the sheet resistance of the IAIA multilayer was mainly dependent on the thickness of the Ag layers. Notably, the optimized IAIA multilayer had a constant resistance change (ΔR/R0) under repeated outer bending tests with a radius of 10 mm. The mechanical integrity of the R2R-sputtered IAIA multilayer indicated that hybridization of an IZO and Ag metal layer is a promising flexible electrode scheme for the next-generation flexible optoelectronics. PMID:22222144

Deep Retinal Layer Microvasculature Dropout Detected by the Optical Coherence Tomography Angiography in Glaucoma.

PubMed

Suh, Min Hee; Zangwill, Linda M; Manalastas, Patricia Isabel C; Belghith, Akram; Yarmohammadi, Adeleh; Medeiros, Felipe A; Diniz-Filho, Alberto; Saunders, Luke J; Weinreb, Robert N

2016-12-01

To investigate factors associated with dropout of the parapapillary deep retinal layer microvasculature assessed by optical coherence tomography angiography (OCTA) in glaucomatous eyes. Cross-sectional study. Seventy-one eyes from 71 primary open-angle glaucoma (POAG) patients with β-zone parapapillary atrophy (βPPA) enrolled in the Diagnostic Innovations in Glaucoma Study. Parapapillary deep-layer microvasculature dropout was defined as a complete loss of the microvasculature located within the deep retinal layer of the βPPA from OCTA-derived optic nerve head vessel density maps by standardized qualitative assessment. Circumpapillary vessel density (cpVD) within the retinal nerve fiber layer (RNFL) also was calculated using OCTA. Choroidal thickness and presence of focal lamina cribrosa (LC) defects were determined using swept-source optical coherence tomography. Presence of parapapillary deep-layer microvasculature dropout. Parameters including age, systolic and diastolic blood pressure, axial length, intraocular pressure, disc hemorrhage, cpVD, visual field (VF) mean deviation (MD), focal LC defects βPPA area, and choroidal thickness were analyzed. Parapapillary deep-layer microvasculature dropout was detected in 37 POAG eyes (52.1%). Eyes with microvasculature dropout had a higher prevalence of LC defects (70.3% vs. 32.4%), lower cpVD (52.7% vs. 58.8%), worse VF MD (-9.06 dB vs. -3.83 dB), thinner total choroidal thickness (126.5 μm vs. 169.1 μm), longer axial length (24.7 mm vs. 24.0 mm), larger βPPA (1.2 mm 2 vs. 0.76 mm 2 ), and lower diastolic blood pressure (74.7 mmHg vs. 81.7 mmHg) than those without dropout (P < 0.05, respectively). In the multivariate logistic regression analysis, higher prevalence of focal LC defects (odds ratio [OR], 6.27; P = 0.012), reduced cpVD (OR, 1.27; P = 0.002), worse VF MD (OR, 1.27; P = 0.001), thinner choroidal thickness (OR, 1.02; P = 0.014), and lower diastolic blood pressure (OR, 1.16; P = 0.003) were associated significantly with the dropout. Systemic and ocular factors including focal LC defects more advanced glaucoma, reduced RNFL vessel density, thinner choroidal thickness, and lower diastolic blood pressure were factors associated with the parapapillary deep-layer microvasculature dropout in glaucomatous eyes. Longitudinal studies are required to elucidate the temporal relationship between parapapillary deep-layer microvasculature dropout and systemic and ocular factors. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Masking technique for coating thickness control on large and strongly curved aspherical optics.

PubMed

Sassolas, B; Flaminio, R; Franc, J; Michel, C; Montorio, J-L; Morgado, N; Pinard, L

2009-07-01

We discuss a method to control the coating thickness deposited onto large and strongly curved optics by ion beam sputtering. The technique uses an original design of the mask used to screen part of the sputtered materials. A first multielement mask is calculated from the measured two-dimensional coating thickness distribution. Then, by means of an iterative process, the final mask is designed. By using such a technique, it has been possible to deposit layers of tantalum pentoxide having a high thickness gradient onto a curved substrate 500 mm in diameter. Residual errors in the coating thickness profile are below 0.7%.

Modification of the laser triangulation method for measuring the thickness of optical layers

NASA Astrophysics Data System (ADS)

Khramov, V. N.; Adamov, A. A.

2018-04-01

The problem of determining the thickness of thin films by the method of laser triangulation is considered. An expression is derived for the film thickness and the distance between the focused beams on the photo detector. The possibility of applying the chosen method for measuring thickness is in the range [0.1; 1] mm. We could resolve 2 individual light marks for a minimum film thickness of 0.23 mm. We resolved with the help of computer processing of photos with a resolution of 0.10 mm. The obtained results can be used in ophthalmology for express diagnostics during surgical operations on the corneal layer.

Adsorption properties of BSA and DsRed proteins deposited on thin SiO2 layers: optically non-absorbing versus absorbing proteins

NASA Astrophysics Data System (ADS)

Scarangella, A.; Soumbo, M.; Villeneuve-Faure, C.; Mlayah, A.; Bonafos, C.; Monje, M.-C.; Roques, C.; Makasheva, K.

2018-03-01

Protein adsorption on solid surfaces is of interest for many industrial and biomedical applications, where it represents the conditioning step for micro-organism adhesion and biofilm formation. To understand the driving forces of such an interaction we focus in this paper on the investigation of the adsorption of bovine serum albumin (BSA) (optically non-absorbing, model protein) and DsRed (optically absorbing, naturally fluorescent protein) on silica surfaces. Specifically, we propose synthesis of thin protein layers by means of dip coating of the dielectric surface in protein solutions with different concentrations (0.01-5.0 g l-1). We employed spectroscopic ellipsometry as the most suitable and non-destructive technique for evaluation of the protein layers’ thickness and optical properties (refractive index and extinction coefficient) after dehydration, using two different optical models, Cauchy for BSA and Lorentz for DsRed. We demonstrate that the thickness, the optical properties and the wettability of the thin protein layers can be finely controlled by proper tuning of the protein concentration in the solution. These results are correlated with the thin layer morphology, investigated by AFM, FTIR and PL analyses. It is shown that the proteins do not undergo denaturation after dehydration on the silica surface. The proteins arrange themselves in a lace-like network for BSA and in a rod-like structure for DsRed to form mono- and multi-layers, due to different mechanisms driving the organization stage.

Aerosol Size Distributions During ACE-Asia: Retrievals From Optical Thickness and Comparisons With In-situ Measurements

NASA Astrophysics Data System (ADS)

Kuzmanoski, M.; Box, M.; Box, G. P.; Schmidt, B.; Russell, P. B.; Redemann, J.; Livingston, J. M.; Wang, J.; Flagan, R. C.; Seinfeld, J. H.

2002-12-01

As part of the ACE-Asia experiment, conducted off the coast of China, Korea and Japan in spring 2001, measurements of aerosol physical, chemical and radiative characteristics were performed aboard the Twin Otter aircraft. Of particular importance for this paper were spectral measurements of aerosol optical thickness obtained at 13 discrete wavelengths, within 354-1558 nm wavelength range, using the AATS-14 sunphotometer. Spectral aerosol optical thickness can be used to obtain information about particle size distribution. In this paper, we use sunphotometer measurements to retrieve size distribution of aerosols during ACE-Asia. We focus on four cases in which layers influenced by different air masses were identified. Aerosol optical thickness of each layer was inverted using two different techniques - constrained linear inversion and multimodal. In the constrained linear inversion algorithm no assumption about the mathematical form of the distribution to be retrieved is made. Conversely, the multimodal technique assumes that aerosol size distribution is represented as a linear combination of few lognormal modes with predefined values of mode radii and geometric standard deviations. Amplitudes of modes are varied to obtain best fit of sum of optical thicknesses due to individual modes to sunphotometer measurements. In this paper we compare the results of these two retrieval methods. In addition, we present comparisons of retrieved size distributions with in situ measurements taken using an aerodynamic particle sizer and differential mobility analyzer system aboard the Twin Otter aircraft.

Automated Segmentation Errors When Using Optical Coherence Tomography to Measure Retinal Nerve Fiber Layer Thickness in Glaucoma.

PubMed

Mansberger, Steven L; Menda, Shivali A; Fortune, Brad A; Gardiner, Stuart K; Demirel, Shaban

2017-02-01

To characterize the error of optical coherence tomography (OCT) measurements of retinal nerve fiber layer (RNFL) thickness when using automated retinal layer segmentation algorithms without manual refinement. Cross-sectional study. This study was set in a glaucoma clinical practice, and the dataset included 3490 scans from 412 eyes of 213 individuals with a diagnosis of glaucoma or glaucoma suspect. We used spectral domain OCT (Spectralis) to measure RNFL thickness in a 6-degree peripapillary circle, and exported the native "automated segmentation only" results. In addition, we exported the results after "manual refinement" to correct errors in the automated segmentation of the anterior (internal limiting membrane) and the posterior boundary of the RNFL. Our outcome measures included differences in RNFL thickness and glaucoma classification (i.e., normal, borderline, or outside normal limits) between scans with automated segmentation only and scans using manual refinement. Automated segmentation only resulted in a thinner global RNFL thickness (1.6 μm thinner, P < .001) when compared to manual refinement. When adjusted by operator, a multivariate model showed increased differences with decreasing RNFL thickness (P < .001), decreasing scan quality (P < .001), and increasing age (P < .03). Manual refinement changed 298 of 3486 (8.5%) of scans to a different global glaucoma classification, wherein 146 of 617 (23.7%) of borderline classifications became normal. Superior and inferior temporal clock hours had the largest differences. Automated segmentation without manual refinement resulted in reduced global RNFL thickness and overestimated the classification of glaucoma. Differences increased in eyes with a thinner RNFL thickness, older age, and decreased scan quality. Operators should inspect and manually refine OCT retinal layer segmentation when assessing RNFL thickness in the management of patients with glaucoma. Copyright © 2016 Elsevier Inc. All rights reserved.

Noninvasive Imaging of Retinal Morphology and Microvasculature in Obese Mice Using Optical Coherence Tomography and Optical Microangiography

PubMed Central

Zhi, Zhongwei; Chao, Jennifer R.; Wietecha, Tomasz; Hudkins, Kelly L.; Alpers, Charles E.; Wang, Ruikang K.

2014-01-01

Purpose. To evaluate early diabetes-induced changes in retinal thickness and microvasculature in a type 2 diabetic mouse model by using optical coherence tomography (OCT)/optical microangiography (OMAG). Methods. Twenty-two-week-old obese (OB) BTBR mice (n = 10) and wild-type (WT) control mice (n = 10) were imaged. Three-dimensional (3D) data volumes were captured with spectral domain OCT using an ultrahigh-sensitive OMAG scanning protocol for 3D volumetric angiography of the retina and dense A-scan protocol for measurement of the total retinal blood flow (RBF) rate. The thicknesses of the nerve fiber layer (NFL) and that of the NFL to the inner plexiform layer (IPL) were measured and compared between OB and WT mice. The linear capillary densities within intermediate and deep capillary layers were determined by the number of capillaries crossing a 500-μm line. The RBF rate was evaluated using an en face Doppler approach. These quantitative measurements were compared between OB and WT mice. Results. The retinal thickness of the NFL to IPL was significantly reduced in OB mice (P < 0.01) compared to that in WT mice, whereas the NFL thickness between the two was unchanged. 3D depth-resolved OMAG angiography revealed the first in vivo 3D model of mouse retinal microcirculation. Although no obvious differences in capillary vessel densities of the intermediate and deep capillary layers were detected between normal and OB mice, the total RBF rate was significantly lower (P < 0.05) in OB mice than in WT mice. Conclusions. We conclude that OB BTBR mice have significantly reduced NFL–IPL thicknesses and total RBF rates compared with those of WT mice, as imaged by OCT/OMAG. OMAG provides an unprecedented capability for high-resolution depth-resolved imaging of mouse retinal vessels and blood flow that may play a pivotal role in providing a noninvasive method for detecting early microvascular changes in patients with diabetic retinopathy. PMID:24458155

The effect of the MgO buffer layer thickness on magnetic anisotropy in MgO/Fe/Cr/MgO buffer/MgO(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozioł-Rachwał, Anna, E-mail: a.koziolrachwal@aist.go.jp; AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków; Nozaki, Takayuki

2016-08-28

The relationship between the magnetic properties and MgO buffer layer thickness d was studied in epitaxial MgO/Fe(t)/Cr/MgO(d) layers grown on MgO(001) substrate in which the Fe thickness t ranged from 0.4 nm to 1.1 nm. For 0.4 nm ≤ t ≤ 0.7 nm, a non-monotonic coercivity dependence on the MgO buffer thickness was shown by perpendicular magneto-optic Kerr effect magnetometry. For thicker Fe films, an increase in the buffer layer thickness resulted in a spin reorientation transition from perpendicular to the in-plane magnetization direction. Possible origins of these unusual behaviors were discussed in terms of the suppression of carbon contamination at the Fe surface and changes inmore » the magnetoelastic anisotropy in the system. These results illustrate a method to control magnetic anisotropy in MgO/Fe/Cr/MgO(d) via an appropriate choice of MgO buffer layer thickness d.« less

Flexible metal-semiconductor-metal device prototype on wafer-scale thick boron nitride layers grown by MOVPE.

PubMed

Li, Xin; Jordan, Matthew B; Ayari, Taha; Sundaram, Suresh; El Gmili, Youssef; Alam, Saiful; Alam, Muhbub; Patriarche, Gilles; Voss, Paul L; Paul Salvestrini, Jean; Ougazzaden, Abdallah

2017-04-11

Practical boron nitride (BN) detector applications will require uniform materials over large surface area and thick BN layers. To report important progress toward these technological requirements, 1~2.5 µm-thick BN layers were grown on 2-inch sapphire substrates by metal-organic vapor phase epitaxy (MOVPE). The structural and optical properties were carefully characterized and discussed. The thick layers exhibited strong band-edge absorption near 215 nm. A highly oriented two-dimensional h-BN structure was formed at the film/sapphire interface, which permitted an effective exfoliation of the thick BN film onto other adhesive supports. And this structure resulted in a metal-semiconductor-metal (MSM) device prototype fabricated on BN membrane delaminating from the substrate. MSM photodiode prototype showed low dark current of 2 nA under 100 V, and 100 ± 20% photoconductivity yield for deep UV light illumination. These wafer-scale MOVPE-grown thick BN layers present great potential for the development of deep UV photodetection applications, and even for flexible (opto-) electronics in the future.

Effects of water-emission anisotropy on multispectral remote sensing at thermal wavelengths of ocean temperature and of cirrus clouds

NASA Technical Reports Server (NTRS)

Otterman, J.; Susskind, J.; Dalu, G.; Kratz, D.; Goldberg, I. L.

1992-01-01

The impact of water-emission anisotropy on remotedly sensed long-wave data has been studied. Water emission is formulated from a calm body for a facile computation of radiative transfer in the atmosphere. The error stemming from the blackbody assumption are calculated for cases of a purely absorbing or a purely scattering atmosphere taking the optical properties of the atmosphere as known. For an absorbing atmosphere, the errors in the sea-surface temperature (SST) are found to be always reduced and be the same whether measurements are made from space or at any level of the atmosphere. The inferred optical thickness tau of an absorbing layer can be in error under the blackbody assumption by a delta tau of 0.01-0.08, while the inferred optical thickness of a scattering layer can be in error by a larger amount, delta tau of 0.03-0.13. It is concluded that the error delta tau depends only weakly on the actual optical thickness and the viewing angle, but is rather sensitive to the wavelength of the measurement.

Population-based evaluation of retinal nerve fiber layer, retinal ganglion cell layer, and inner plexiform layer as a diagnostic tool for glaucoma.

PubMed

Springelkamp, Henriët; Lee, Kyungmoo; Wolfs, Roger C W; Buitendijk, Gabriëlle H S; Ramdas, Wishal D; Hofman, Albert; Vingerling, Johannes R; Klaver, Caroline C W; Abràmoff, Michael D; Jansonius, Nomdo M

2014-11-20

We determined the glaucoma screening performance of regional optical coherence tomography (OCT) layer thickness measurements in the peripapillary and macular region, in a population-based setting. Subjects (n = 1224) in the Rotterdam Study underwent visual field testing (Humphrey Field Analyzer) and OCT of the macula and optic nerve head (Topcon 3-D OCT-1000). We determined the mean thicknesses of the retinal nerve fiber layer (RNFL), retinal ganglion cell layer (RGCL), and inner plexiform layer for regions-of-interest; thus, defining a series of OCT parameters, using the Iowa Reference Algorithms. Reference standard was the presence of glaucomatous visual field loss (GVFL); controls were subjects without GVFL, an intraocular pressure (IOP) of 21 mm Hg or less, and no positive family history for glaucoma. We calculated the area under the receiver operating characteristics curve (AUCs) and the sensitivity at 97.5% specificity for each parameter. After excluding 23 subjects with an IOP > 21 mm Hg and 73 subjects with a positive family history for glaucoma, there were 1087 controls and 41 glaucoma cases. Mean RGCL thickness in the inferior half of the macular region showed the highest AUC (0.85; 95% confidence interval [CI] 0.77-0.92) and sensitivity (53.7%; 95% CI, 38.7-68.0%). The mean thickness of the peripapillary RNFL had an AUC of 0.77 (95% CI, 0.69-0.85) and a sensitivity of 24.4% (95% CI, 13.7-39.5%). Macular RGCL loss is at least as common as peripapillary RNFL abnormalities in population-based glaucoma cases. Screening for glaucoma using OCT-derived regional thickness identifies approximately half of those cases of glaucoma as diagnosed by perimetry. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Diagnostic ability of macular ganglion cell-inner plexiform layer thickness in glaucoma suspects.

PubMed

Xu, Xiaoyu; Xiao, Hui; Guo, Xinxing; Chen, Xiangxi; Hao, Linlin; Luo, Jingyi; Liu, Xing

2017-12-01

The purpose is to assess the diagnostic ability for early glaucoma of macular ganglion cell-inner plexiform layer (GCIPL) thickness in a Chinese population including glaucoma suspects.A total of 367 eyes with primary open-angle glaucoma (168 early glaucoma, 78 moderate glaucoma, and 121 advanced glaucoma), 52 eyes with ocular hypertension (OHT), 59 eyes with enlarged cup-to-disc ratio (C/D), and 225 normal eyes were included. GCIPL thickness (average, minimum, superotemporal, superior, superonasal, inferonasal, inferior, and inferotemporal), retinal nerve fiber layer (RNFL) thickness, and optic nerve head (ONH) parameters were measured using Cirrus high-definition optical coherence tomography (OCT) and compared. The diagnostic ability of OCT parameters was assessed by area under receiver operating characteristic curve (AUROC) in 3 distinguishing groups: normal eyes and eyes with early glaucoma, normal eyes and eyes with glaucoma regardless of disease stage, and nonglaucomatous eyes (normal eyes, eyes with OHT, and enlarged C/D) and early glaucomatous eyes.Glaucomatous eyes showed a significant reduction in GCIPL thickness compared with nonglaucomatous eyes. In all 3 distinguishing groups, best-performing parameters of GCIPL thickness, RNFL thickness, and ONH parameters were minimum GCIPL thickness (expressed in AUROC, 0.899, 0.952, and 0.900, respectively), average RNFL thickness (0.904, 0.953, and 0.892, respectively), and rim area (0.861, 0.925, and 0.824, respectively). There was no statistical significance of AUROC between minimum GCIPL thickness and average RNFL thickness (all P > .05).GCIPL thickness could discriminate early glaucoma from normal and glaucoma suspects with good sensitivity and specificity. The glaucoma diagnostic ability of GCIPL thickness was comparable to that of RNFL thickness. Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.

Evaluation of Retinal Changes in Progressive Supranuclear Palsy and Parkinson Disease.

PubMed

Gulmez Sevim, Duygu; Unlu, Metin; Gultekin, Murat; Karaca, Cagatay; Mirza, Meral; Mirza, Galip Ertugrul

2018-06-01

Differentiating Parkinson disease (PD) from progressive supranuclear palsy (PSP) can be challenging early in the clinical course. The aim of our study was to see if specific retinal changes could serve as a distinguishing feature. We used spectral domain optical coherence tomography (SD-OCT) with automatic segmentation to measure peripapillary nerve fiber layer thickness and the thickness and volume of retinal layers at the macula. Thicknesses of superior peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell layer, inner plexiform layer, inner nuclear layer, and macular volume were more affected in PSP compared with PD (P < 0.05). Thicker inferotemporal pRNFL and lower macular volume were detected in levodopa users compared with nonusers in patients with PD. PD and PSP are associated with distinct changes in retinal morphology, which can be assessed with SD-OCT.

Confocal absorption spectral imaging of MoS2: optical transitions depending on the atomic thickness of intrinsic and chemically doped MoS2.

PubMed

Dhakal, Krishna P; Duong, Dinh Loc; Lee, Jubok; Nam, Honggi; Kim, Minsu; Kan, Min; Lee, Young Hee; Kim, Jeongyong

2014-11-07

We performed a nanoscale confocal absorption spectral imaging to obtain the full absorption spectra (over the range 1.5-3.2 eV) within regions having different numbers of layers and studied the variation of optical transition depending on the atomic thickness of the MoS2 film. Three distinct absorption bands corresponding to A and B excitons and a high-energy background (BG) peak at 2.84 eV displayed a gradual redshift as the MoS2 film thickness increased from the monolayer, to the bilayer, to the bulk MoS2 and this shift was attributed to the reduction of the gap energy in the Brillouin zone at the K-point as the atomic thickness increased. We also performed n-type chemical doping of MoS2 films using reduced benzyl viologen (BV) and the confocal absorption spectra modified by the doping showed a strong dependence on the atomic thickness: A and B exciton peaks were greatly quenched in the monolayer MoS2 while much less effect was shown in larger thickness and the BG peak either showed very small quenching for 1 L MoS2 or remained constant for larger thicknesses. Our results indicate that confocal absorption spectral imaging can provide comprehensive information on optical transitions of microscopic size intrinsic and doped two-dimensional layered materials.

Tunable surface plasmon resonance frequency of Au-Ag bimetallic asymmetric structure thin films in the UV and IR region

NASA Astrophysics Data System (ADS)

Hong, Ruijin; Ji, Jialin; Tao, Chunxian; Zhang, Dawei

2016-10-01

Au/ZnO/Ag sandwich structure films were fabricated by DC magnetron sputter at room temperature. The tunability of the surface plasmon resonance wavelength was realized by varying the thickness of ZnO thin film. The effects of ZnO layer on the optical properties of Au/ZnO/Au thin films were investigated by optical absorption and Raman scattering measurements. It has been found that both the surface plasmon resonance frequency and SERS can be controlled by adjusting the thickness of ZnO layer due to the coupling of metal and semiconductor.

Lidar observation of transition of cirrus clouds over a tropical station Gadanki (13.45° N, 79.18° E): case studies

NASA Astrophysics Data System (ADS)

Srinivasan, M. A.; Rao, C. Dhananjaya; Krishnaiah, M.

2016-05-01

The present study describes Mie lidar observations of the cirrus cloud passage showing transition between double thin layers into single thick and single thick layer into double thin layers of cirrus over Gadanki region. During Case1: 17 January 2007, Case4: 12 June 2007, Case5: 14 July 2007 and Case6: 24 July 2007 the transition is found to from two thin cirrus layers into single geometrically thick layer. Case2: 14 May 2007 and Case3: 15 May 2007, the transition is found to from single geometrically thick layer into two thin cirrus layers. Linear Depolarization Ratio (LDR) and Back Scatter Ration (BSR) are found to show similar variation with strong peaks during transition; both LDR and Cloud Optical Depth (COD) is found to show similar variation except during transition with strong peaks in COD which is not clearly found from LDR for the all cases. There is a significant weakening of zonal and meridional winds during Case1 which might be due to the transition from multiple to single thick cirrus indicating potential capability of thick cirrus in modulating the wind fields. There exists strong upward wind dominance contributed to significant ascent in cloud-base altitude thereby causing transition of multiple thin layers into single thick cirrus.

Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. II - Marine stratocumulus observations

NASA Technical Reports Server (NTRS)

Nakajima, Teruyuki; King, Michael D.; Spinhirne, James D.; Radke, Lawrence F.

1991-01-01

A multispectral scanning radiometer has been used to obtain measurements of the reflection function of marine stratocumulus clouds at 0.75 micron and at 1.65 and 2.16 microns. These observations were obtained from the NASA ER-2 aircraft as part of the FIRE, conducted off the coast of southern California during July 1987. Multispectral images of the reflection function were used to derive the optical thickness and the effective particle radius of stratiform cloud layers on four days. In addition to the radiation measurements, in situ microphysical measurements were obtained from an aircraft. In this paper, the remote sensing results are compared with in situ observations, which show a good spatial correlation for both optical thickness and effective radius. These comparisons further show systematic differences between remote sensing and in situ values, with a tendency for remote sensing to overestimate the effective radius by about 2-3 microns, independent of particle radius. The optical thickness, in contrast, is somewhat overestimated for small optical thicknesses and underestimated for large optical thicknesses. An introduction of enhanced gaseous absorption at a wavelength of 2.16 microns successfully explains some of these observed discrepancies.

Study of ion beam sputtered Fe/Si interfaces as a function of Si layer thickness

NASA Astrophysics Data System (ADS)

Kumar, Anil; Brajpuriya, Ranjeet; Singh, Priti

2018-01-01

The exchange interaction in metal/semiconductor interfaces is far from being completely understood. Therefore, in this paper, we have investigated the nature of silicon on the Fe interface in the ion beam deposited Fe/Si/Fe trilayers keeping the thickness of the Fe layers fixed at 3 nm and varying the thickness of the silicon sandwich layer from 1.5 nm to 4 nm. Grazing incidence x-ray diffraction and atomic force microscopy techniques were used, respectively, to study the structural and morphological changes in the deposited films as a function of layer thickness. The structural studies show silicide formation at the interfaces during deposition and better crystalline structure of Fe layers at a lower spacer layer thickness. The magnetization behavior was investigated using magneto-optical Kerr effect, which clearly shows that coupling between the ferromagnetic layers is highly influenced by the semiconductor spacer layer thickness. A strong antiferromagnetic coupling was observed for a value of tSi = 2.5 nm but above this value an unexpected behavior of hysteresis loop (step like) with two coercivity values is recorded. For spacer layer thickness greater than 2.5 nm, an elemental amorphous Si layer starts to appear in the spacer layer in addition to the silicide layer at the interfaces. It is observed that in the trilayer structure, Fe layers consist of various stacks, viz., Si doped Fe layers, ferromagnetic silicide layer, and nonmagnetic silicide layer at the interfaces. The two phase hysteresis loop is explained on the basis of magnetization reversal of two ferromagnetic layers, independent of each other, with different coercivities. X-ray photo electron spectroscopy technique was also used to study interfaces characteristics as a function of tSi.

Comparison of peripapillary retinal nerve fiber layer loss and visual outcome in fellow eyes following sequential bilateral non-arteritic anterior ischemic optic neuropathy.

PubMed

Dotan, Gad; Kesler, Anat; Naftaliev, Elvira; Skarf, Barry

2015-05-01

To report on the correlation of structural damage to the axons of the optic nerve and visual outcome following bilateral non-arteritic anterior ischemic optic neuropathy. A retrospective review of the medical records of 25 patients with bilateral sequential non-arteritic anterior ischemic optic neuropathy was performed. Outcome measures were peripapillary retinal nerve fiber layer thickness measured with the Stratus optical coherence tomography scanner, visual acuity and visual field loss. Median peripapillary retinal nerve fiber layer (RNFL) thickness, mean deviation (MD) of visual field, and visual acuity of initially involved NAION eyes (54.00 µm, -17.77 decibels (dB), 0.4, respectively) were comparable to the same parameters measured following development of second NAION event in the other eye (53.70 µm, p = 0.740; -16.83 dB, p = 0.692; 0.4, p = 0.942, respectively). In patients with bilateral NAION, there was a significant correlation of peripapillary RNFL thickness (r = 0.583, p = 0.002) and MD of the visual field (r = 0.457, p = 0.042) for the pairs of affected eyes, whereas a poor correlation was found in visual acuity of these eyes (r = 0.279, p = 0.176). Peripapillary RNFL thickness following NAION was positively correlated with MD of visual field (r = 0.312, p = 0.043) and negatively correlated with logMAR visual acuity (r = -0.365, p = 0.009). In patients who experience bilateral NAION, the magnitude of RNFL loss is similar in each eye. There is a greater similarity in visual field loss than in visual acuity between the two affected eyes with NAION of the same individual.

The effect of TiO2 phase on the surface plasmon resonance of silver thin film

NASA Astrophysics Data System (ADS)

Hong, Ruijin; Jing, Ming; Tao, Chunxian; Zhang, Dawei

2016-10-01

A series of silver films with various thicknesses were deposited on TiO2 covered silica substrates by magnetron sputtering at room temperature. The effects of TiO2 phase on the structure, optical properties and surface plasmon resonance of silver thin films were investigated by x-ray diffraction, optical absorption and Raman scattering measurements, respectively. By adjusting the silver layer thickness, the resonance wavelength shows a redshift, which is due to a change in the electromagnetic field coupling strength from the localized surface plasmons excited between the silver thin film and TiO2 layer. Raman scattering measurement results showed that optical absorption plays an important role in surface plasmon enhancement, which is also related to different crystal phase.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hao; Lunt, Barry M.; Gates, Richard J.

A novel write-once-read-many (WORM) optical stack on Mylar tape is proposed as a replacement for magnetic tape for archival data storage. This optical tape contains a cosputtered bismuth–tellurium–selenium (BTS) alloy as the write layer sandwiched between thin, protective films of reactively sputtered carbon. The composition and thickness of the BTS layer were confirmed by Rutherford Backscattering (RBS) and atomic force microscopy (AFM), respectively. The C/BTS/C stack on Mylar was written to/marked by 532 nm laser pulses. Under the same conditions, control Mylar films without the optical stack were unaffected. Marks, which showed craters/movement of the write material, were characterized bymore » optical microscopy and AFM. The threshold laser powers for making marks on C/BTS/C stacks with different thicknesses were explored. Higher quality marks were made with a 60× objective compared to a 40× objective in our marking apparatus. Finally, the laser writing process was simulated with COMSOL.« less

Modes of interaction between nanostructured metal and a conducting mirror as a function of separation and incident polarization

NASA Astrophysics Data System (ADS)

Bonnie, F.; Arnold, M. D.; Smith, G. B.; Gentle, A. R.

2013-09-01

The optical resonances that occur in nanostructured metal layers are modulated in thin film stacks if the nanostructured layer is separated from a reflecting conducting layer by various thicknesses of thin dielectric. We have measured and modeled the optical response of interacting silver layers, with alumina spacer thickness ranging from a few nm to 50 nm, for s- and p-polarized incident light, and a range of incident angles. Standard thin film models, including standard effective medium models for the nanostructured layer, will break down for spacer thickness below a critical threshold. For example, with polarisation in the film plane and some nano-islands, it may occur at around 10 nm depending on spacer refractive index. Of particular interest here are novel effects observed with the onset of percolation in the nanolayer. Hot spot effects can be modified by nearby mirrors. Other modes to consider include (a) a two-particle mode involving a particle and its mirror image (b) A Fano resonance from hybridisation of localized and de-localised plasmon modes (c) a Babinet's core-(partial) shell particle with metal core-dielectric shell in metal (d) spacing dependent phase modulation (e) the impact of field gradients induced by the mirror at the nano-layer.

Quantification of Peripapillary Sparing and Macular Involvement in Stargardt Disease (STGD1)

PubMed Central

Rhee, David W.; Smith, R. Theodore; Tsang, Stephen H.; Allikmets, Rando; Chang, Stanley; Lazow, Margot A.; Hood, Donald C.; Greenstein, Vivienne C.

2011-01-01

Purpose. To quantify and compare structure and function across the macula and peripapillary area in Stargardt disease (STGD1). Methods. Twenty-seven patients (27 eyes) and 12 age-similar controls (12 eyes) were studied. Patients were classified on the basis of full-field electroretinogram (ERG) results. Fundus autofluorescence (FAF) and spectral domain-optical coherence tomography (SD-OCT) horizontal line scans were obtained through the fovea and peripapillary area. The thicknesses of the outer nuclear layer plus outer plexiform layer (ONL+), outer segment (OS), and retinal pigment epithelium (RPE) were measured through the fovea, and peripapillary areas from 1° to 4° temporal to the optic disc edge using a computer-aided, manual segmentation technique. Visual sensitivities in the central 10° were assessed using microperimetry and related to retinal layer thicknesses. Results. Compared to the central macula, the differences between controls and patients in ONL+, OS, and RPE layer thicknesses were less in the nasal and temporal macula. Relative sparing of the ONL+ and/or OS layers was detected in the nasal (i.e., peripapillary) macula in 8 of 13 patients with extramacular disease on FAF; relative functional sparing was also detected in this subgroup. All 14 patients with disease confined to the central macula, as detected on FAF, showed ONL+ and OS layer thinning in regions of normal RPE thickness. Conclusions. Relative peripapillary sparing was detected in STGD1 patients with extramacular disease on FAF. Photoreceptor thinning may precede RPE degeneration in STGD1. PMID:21873672

Ultralight Weight Optical Systems Using Nano-Layered Synthesized Materials

NASA Technical Reports Server (NTRS)

Clark, Natalie; Breckinridge, James

2014-01-01

Optical imaging is important for many NASA science missions. Even though complex optical systems have advanced, the optics, based on conventional glass and mirrors, require components that are thick, heavy and expensive. As the need for higher performance expands, glass and mirrors are fast approaching the point where they will be too large, heavy and costly for spacecraft, especially small satellite systems. NASA Langley Research Center is developing a wide range of novel nano-layered synthesized materials that enable the development and fabrication of ultralight weight optical device systems that enable many NASA missions to collect science data imagery using small satellites. In addition to significantly reducing weight, the nano-layered synthesized materials offer advantages in performance, size, and cost.

Optical properties of Ag nanoclusters formed by irradiation and annealing of SiO2/SiO2:Ag thin films

NASA Astrophysics Data System (ADS)

Güner, S.; Budak, S.; Gibson, B.; Ila, D.

2014-08-01

We have deposited five periodic SiO2/SiO2 + Ag multi-nano-layered films on fused silica substrates using physical vapor deposition technique. The co-deposited SiO2:Ag layers were 2.7-5 nm and SiO2 buffer layers were 1-15 nm thick. Total thickness was between 30 and 105 nm. Different concentrations of Ag, ranging from 1.5 to 50 molecular% with respect to SiO2 were deposited to determine relevant rates of nanocluster formation and occurrence of interaction between nanoclusters. Using interferometry as well as in situ thickness monitoring, we measured the thickness of the layers. The concentration of Ag in SiO2 was measured with Rutherford Backscattering Spectrometry (RBS). To nucleate Ag nanoclusters, 5 MeV cross plane Si ion bombardments were performed with fluence varying between 5 × 1014 and 1 × 1016 ions/cm2 values. Optical absorption spectra were recorded in the range of 200-900 nm in order to monitor the Ag nanocluster formation in the thin films. Thermal annealing treatment at different temperatures was applied as second method to form varying size of nanoclusters. The physical properties of formed super lattice were criticized for thermoelectric applications.

Influence of enamel composite thickness on value, chroma and translucency of a high and a nonhigh refractive index resin composite.

PubMed

Ferraris, Federico; Diamantopoulou, Sofia; Acunzo, Raffaele; Alcidi, Renato

2014-01-01

To evaluate the influence of thickness on the optical properties of two enamel shade composites, one with a high refractive index and one traditional. A medium value enamel shade was selected from the resin composites Enamel Plus HRi (UE2) and Enamel Plus HFO (GE2). Enamel Plus HRi is a high refractive index composite. Samples were fabricated in five different thicknesses: 0.3, 0.5, 1, 1.5 and 2 mm. Three specimens per material and thickness were fabricated. Three measurements per sample, over white, black and dentin composite background were generated with a spectrophotometer (Spectroshade Micro, MHT). Value, chroma, translucency and color differences (ΔE) of the specimens were calculated. RESULTS were analyzed by the Pearson correlation test, ANOVA and a post-hoc Tukey test. Increasing the thickness of the enamel layers decreased the translucency and the chroma of the substrate for both materials tested. For HRi the increase of the thickness resulted in an increase of the value, whereas for HFO it resulted in a reduction of the value. The two composites showed a significant difference in value for each thickness, but not in translucency and chroma. Color difference between them was perceptible in layers equal or higher than 0.5 mm. The high refractive index enamel (HRi) composite exhibits different optical behavior compared to the traditional one (HFO). HRi enamel composite behaves more like natural enamel as by increasing the thickness of the enamel layer, the value also increases.

Theoretical modeling of a coupled plasmon waveguide resonance sensor based on multimode optical fiber

NASA Astrophysics Data System (ADS)

Liu, Kun; Xue, Meng; Jiang, Junfeng; Wang, Tao; Chang, Pengxiang; Liu, Tiegen

2018-03-01

A coupled plasmon waveguide resonance (CPWR) sensor based on metal/dielectric-coated step index multimode optical fiber is proposed. Theoretical simulations using the four-layer Fresnel equations based on a bi-dimensional optical fiber model were implemented on four structures: Ag-ZnO, Au-ZnO, Ag-TiO2 and Au-TiO2. By controlling the thickness of dielectric layer, we managed to manipulate the CPWR resonance wavelengths. When a CPWR resonance dip is in the short wavelength region, it is insensitive to the change of surrounding refractive index (SRI) and can be used as a reference to improve the sensing accuracy of surface plasmon resonance (SPR) mode. With the increase of the thickness of the dielectric layer, the CPWR resonance dips shift to longer wavelength and the corresponding sensitivities increase. When the 1st CPWR resonance wavelength is near 1550 nm and SRI is around 1.333, the sensitivities of four structures reach 1360.61 nm/RIU, 1375.76 nm/RIU, 1048.48 nm/RIU and 1015.15 nm/RIU, respectively. The values are close to that of the conventional SPR optical fiber sensor while the spectral bandwidths of the optical fiber CPWR sensors are narrower.

Automated array assembly task, phase 1

NASA Technical Reports Server (NTRS)

Carbajal, B. G.

1977-01-01

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

The Vertical Distribution of Thin Features Over the Arctic Analysed from CALIPSO Observations. Part 2; Aerosols

NASA Technical Reports Server (NTRS)

Devasthale, Abhya; Tjernstrom, Michael; Omar, Ali H.

2010-01-01

Influx of aerosols from the mid-latitudes has a wide range of impacts on the Arctic atmosphere. In this study, the capability of the CALIPSO-CALIOP instrument to provide accurate observations of aerosol layers is exploited to characterize their vertical distribution, probability density functions (PDFs) of aerosol layer thickness, base and top heights, and optical depths over the Arctic for the 4-yr period from June 2006 to May 2010. It is shown that the bulk of aerosols, from about 65% in winter to 45% in summer, are confined below the lowermost kilometer of the troposphere. In the middle troposphere (3-5 km), spring and autumn seasons show slightly higher aerosol amounts compared to other two seasons. The relative vertical distribution of aerosols shows that clean continental aerosol is the largest contributor in all seasons except in summer, when layers of polluted continental aerosols are almost as large. In winter and spring, polluted continental aerosols are the second largest contributor to the total number of observed aerosol layers, whereas clean marine aerosol is the second largest contributor in summer and autumn. The PDFs of the geometrical thickness of the observed aerosol layers peak about 400-700 m. Polluted continental and smoke aerosols, which are associated with the intrusions from mid-latitudes, have much broader distributions of optical and geometrical thicknesses, suggesting that they appear more often optically thicker and higher up in the troposphere.

Bendability optimization of flexible optical nanoelectronics via neutral axis engineering

PubMed Central

2012-01-01

The enhancement of bendability of flexible nanoelectronics is critically important to realize future portable and wearable nanoelectronics for personal and military purposes. Because there is an enormous variety of materials and structures that are used for flexible nanoelectronic devices, a governing design rule for optimizing the bendability of these nanodevices is required. In this article, we suggest a design rule to optimize the bendability of flexible nanoelectronics through neutral axis (NA) engineering. In flexible optical nanoelectronics, transparent electrodes such as indium tin oxide (ITO) are usually the most fragile under an external load because of their brittleness. Therefore, we representatively focus on the bendability of ITO which has been widely used as transparent electrodes, and the NA is controlled by employing a buffer layer on the ITO layer. First, we independently investigate the effect of the thickness and elastic modulus of a buffer layer on the bendability of an ITO film. Then, we develop a design rule for the bendability optimization of flexible optical nanoelectronics. Because NA is determined by considering both the thickness and elastic modulus of a buffer layer, the design rule is conceived to be applicable regardless of the material and thickness that are used for the buffer layer. Finally, our design rule is applied to optimize the bendability of an organic solar cell, which allows the bending radius to reach about 1 mm. Our design rule is thus expected to provide a great strategy to enhance the bending performance of a variety of flexible nanoelectronics. PMID:22587757

Bendability optimization of flexible optical nanoelectronics via neutral axis engineering.

PubMed

Lee, Sangmin; Kwon, Jang-Yeon; Yoon, Daesung; Cho, Handong; You, Jinho; Kang, Yong Tae; Choi, Dukhyun; Hwang, Woonbong

2012-05-15

The enhancement of bendability of flexible nanoelectronics is critically important to realize future portable and wearable nanoelectronics for personal and military purposes. Because there is an enormous variety of materials and structures that are used for flexible nanoelectronic devices, a governing design rule for optimizing the bendability of these nanodevices is required. In this article, we suggest a design rule to optimize the bendability of flexible nanoelectronics through neutral axis (NA) engineering. In flexible optical nanoelectronics, transparent electrodes such as indium tin oxide (ITO) are usually the most fragile under an external load because of their brittleness. Therefore, we representatively focus on the bendability of ITO which has been widely used as transparent electrodes, and the NA is controlled by employing a buffer layer on the ITO layer. First, we independently investigate the effect of the thickness and elastic modulus of a buffer layer on the bendability of an ITO film. Then, we develop a design rule for the bendability optimization of flexible optical nanoelectronics. Because NA is determined by considering both the thickness and elastic modulus of a buffer layer, the design rule is conceived to be applicable regardless of the material and thickness that are used for the buffer layer. Finally, our design rule is applied to optimize the bendability of an organic solar cell, which allows the bending radius to reach about 1 mm. Our design rule is thus expected to provide a great strategy to enhance the bending performance of a variety of flexible nanoelectronics.

Stabilized Alkali-Metal Ultraviolet-Band-Pass Filters

NASA Technical Reports Server (NTRS)

Mardesich, Nick; Fraschetti, George A.; Mccann, Timothy; Mayall, Sherwood D.; Dunn, Donald E.; Trauger, John T.

1995-01-01

Layers of bismuth 5 to 10 angstrom thick incorporated into alkali-metal ultraviolet-band-pass optical filters by use of advanced fabrication techniques. In new filters layer of bismuth helps to reduce surface migration of sodium. Sodium layer made more stable and decreased tendency to form pinholes by migration.

A Liquid Optical Phase Shifter with an Embedded Electrowetting Actuator

PubMed Central

Ashtiani, Alireza Ousati; Jiang, Hongrui

2017-01-01

We demonstrate an electrowetting-based liquid optical phase shifter. The phase shifter consists of two immiscible liquid layers with different refractive indices. Sandwiched between the two liquids is a rigid membrane that moves freely along the optical axis and supported by a compliant surround. When applied with a pressure, the thicknesses of both liquid layers change, which induces a difference in optical path, resulting in a phase shift. A miniaturized electrowetting-based actuator is used to produce hydraulic pressure. A multi-layered SU8 bonded structure was fabricated. A phase shift of 171° was observed when the device was incorporated in a Mach-Zehnder interferometer and driven with 100 V. PMID:29038640

Three-Layered Atmospheric Structure in Accretion Disks Around Stellar-Mass Black Holes

NASA Technical Reports Server (NTRS)

Zhang, S. N.; Cui, Wei; Chen, Wan; Yao, Yangsen; Zhang, Xiaoling; Sun, Xuejun; Wu, Xue-Bing; Xu, Haiguang

2000-01-01

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of the inner accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to 1.5 kiloelectron volts and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 kiloelectron volts or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggests that similar physical processes may be operating in these different systems.

Three-layered atmospheric structure in accretion disks around stellar-mass black holes

PubMed

Zhang; Cui; Chen; Yao; Zhang; Sun; Wu; Xu

2000-02-18

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of their accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to 1.5 kiloelectron volts and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 kiloelectron volts or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggests that similar physical processes may be operating in these different systems.

Choroidal Haller's and Sattler's Layers Thickness in Normal Indian Eyes.

PubMed

Roy, Rupak; Saurabh, Kumar; Vyas, Chinmayi; Deshmukh, Kaustubh; Sharma, Preeti; Chandrasekharan, Dhileesh P; Bansal, Aditya

2018-01-01

This study aims to study normative choroidal thickness (CT) and Haller's and Sattler's layers thickness in normal Indian eyes. The choroidal imaging of 73 eyes of 43 healthy Indian individuals was done using enhanced depth imaging feature of spectralis optical coherence tomography. Rraster scan protocol centered at fovea was used for imaging separately by two observers. CT was defined as the length of the perpendicular line drown from the outer border of hypereflective RPE-Bruch's complex to inner margin of choroidoscleral junction. Choroidal vessel layer thickness was measured after defining a largest choroidal vessel lumen within 750 μ on either side of the subfoveal CT vector. A perpendicular line was drawn to the innermost border of this lumen, and the distance between the perpendicular line and innermost border of choroidoscleral junction gave large choroidal vessel layer thickness (LCVLT, Haller's layer). Medium choroidal vessel layer thickness (MCVLT, Sattler's layer) was measured as the distance between same perpendicular line and outer border of hypereflective RPE-Bruch's complex. The mean age of individuals was 28.23 ± 15.29 years (range 14-59 years). Overall, the mean subfoveal CT was 331.6 ± 63.9 μ. Mean LCVLT was 227.08 ± 51.24 μ and the mean MCVLT was 95.65 ± 23.62 μ. CT was maximum subfoveally with gradual reduction in the thickness as the distance from the fovea increased. This is the first study describing the choroidal sublayer thickness, i.e., Haller's and Sattler's layer thickness along with CT in healthy Indian population.

Choroidal Haller's and Sattler's Layers Thickness in Normal Indian Eyes

PubMed Central

Roy, Rupak; Saurabh, Kumar; Vyas, Chinmayi; Deshmukh, Kaustubh; Sharma, Preeti; Chandrasekharan, Dhileesh P.; Bansal, Aditya

2018-01-01

AIM: This study aims to study normative choroidal thickness (CT) and Haller's and Sattler's layers thickness in normal Indian eyes. MATERIALS AND METHODS: The choroidal imaging of 73 eyes of 43 healthy Indian individuals was done using enhanced depth imaging feature of spectralis optical coherence tomography. Rraster scan protocol centered at fovea was used for imaging separately by two observers. CT was defined as the length of the perpendicular line drown from the outer border of hypereflective RPE-Bruch's complex to inner margin of choroidoscleral junction. Choroidal vessel layer thickness was measured after defining a largest choroidal vessel lumen within 750 μ on either side of the subfoveal CT vector. A perpendicular line was drawn to the innermost border of this lumen, and the distance between the perpendicular line and innermost border of choroidoscleral junction gave large choroidal vessel layer thickness (LCVLT, Haller's layer). Medium choroidal vessel layer thickness (MCVLT, Sattler's layer) was measured as the distance between same perpendicular line and outer border of hypereflective RPE-Bruch's complex. RESULTS: The mean age of individuals was 28.23 ± 15.29 years (range 14–59 years). Overall, the mean subfoveal CT was 331.6 ± 63.9 μ. Mean LCVLT was 227.08 ± 51.24 μ and the mean MCVLT was 95.65 ± 23.62 μ. CT was maximum subfoveally with gradual reduction in the thickness as the distance from the fovea increased. CONCLUSION: This is the first study describing the choroidal sublayer thickness, i.e., Haller's and Sattler's layer thickness along with CT in healthy Indian population. PMID:29899646

Structural changes of macula and optic disk of the fellow eye in patients with nonarteritic anterior ischemic optic neuropathy.

PubMed

Duman, R; Yavas, G F; Veliyev, I; Dogan, M; Duman, R

2018-05-10

The aim was to assess the ganglion cell complex (GCC) thickness, retinal nerve fiber layer (RNFL) thickness and optic disk features in the affected eyes (AE) and unaffected fellow eyes (FE) of subjects with unilateral nonarteritic anterior ischemic optic neuropathy (NAION) and to compare with healthy control eyes (CE) using spectral domain-optical coherence tomography (SD-OCT). This study included 28 patients and age, sex and refraction-matched 28 control subjects. Mean GCC thickness and peripapillary RNFL thickness in four quadrants measured by cirrus SD-OCT were evaluated in both AE and FE of patients and CE. In addition, optic disk measurements obtained with OCT were evaluated. Mean GCC thickness was significantly lower in AE compared with both FE and CE (P < 0.001), and mean GCC thickness in FE was significantly lower than CE (P = 0.022). In addition, mean RNFL thickness in superior and nasal quadrants significantly decreased in FE compared with CE (P = 0.020 and 0.010, respectively). Furthermore, AE had significantly greater optic disk cupping compared with both FE and CE (P < 0.001). GCC and RNFL thickness decreased significantly at late stages of NAION, in both AE and FE compared with CE, suggesting that some subclinical structural changes may occur in FE despite lack of obvious visual symptoms. In addition, there was no significant difference in optic disk features between the CE and FE. And significantly greater optic disk cupping in the AE compared with both FE and CE supports the acquired enlargement of cupping after the onset of NAION.

Dependence of the optical constants and the performance in the SPREE gas measurement on the thickness of doped tin oxide over coatings

NASA Astrophysics Data System (ADS)

Fischer, D.; Hertwig, A.; Beck, U.; Negendank, D.; Lohse, V.; Kormunda, M.; Esser, N.

2017-11-01

In this study, thickness related changes of the optical properties of doped tin oxide were studied. Two different sets of samples were prepared. The first set was doped with iron or nickel on silicon substrate with thicknesses of 29-56 nm, the second was iron doped on gold/glass substrate with 1.6-6.3 nm. The optical constants were determined by using spectral ellipsometry (SE) followed by modelling of the dielectric function with an oscillator model using Gaussian peaks. The analysis of the optical constants shows a dependence of the refraction and the absorption on the thickness of the doped tin oxide coating. In addition to the tin oxide absorption in the UV, one additional absorption peak was found in the near-IR/red which is related to plasmonic effects due to the doping. This peak shifts from the near-IR to the red part of the visible spectrum and becomes stronger by reducing the thickness, probably due to the formation of metal nanoparticles in this layer. These results were found for two different sets of samples by using the same optical model. Afterwards the second sample set was tested in the Surface Plasmon Resonance Enhanced Ellipsometric (SPREE) gas measurement with CO gas. It was found that the thickness has significant influence on the sensitivity and thus the adsorption of the CO gas. By increasing the thickness from 1.6 nm to 5.1 nm, the sensing ability is enhanced due to a higher coverage of the surface with the over coating. This is explained by the high affinity of CO molecules to the incorporated Fe-nanoparticles in the tin oxide coating. By increasing the thickness further to 6.3 nm, the sensing ability drops because the layer disturbs the SPR sensing effect too much.

Selective colors reflection from stratified aragonite calcium carbonate plates of mollusk shells.

PubMed

Lertvachirapaiboon, Chutiparn; Parnklang, Tewarak; Pienpinijtham, Prompong; Wongravee, Kanet; Thammacharoen, Chuchaat; Ekgasit, Sanong

2015-08-01

An interaction between the incident light and the structural architecture within the shell of Asian green mussel (Perna viridis) induces observable pearlescent colors. In this paper, we investigate the influence of the structural architecture on the expressed colors. After a removal of the organic binder, small flakes from crushed shells show vivid rainbow reflection under an optical microscope. An individual flake expresses vivid color under a bright-field illumination while become transparent under a dark-field illumination. The expressed colors of the aragonite flakes are directly associated with its structural architecture. The flakes with aragonite thickness of 256, 310, and 353 nm, respectively, appear blue, green, and red under an optical microscope. The spectral simulation corroborates the experimentally observed optical effects as the flakes with thicker aragonite layers selectively reflected color with longer wavelengths. Flakes with multiple aragonite thicknesses expressed multi-color as the upper aragonite layers allow reflected colors from the lower layers to be observed. Copyright © 2015 Elsevier Inc. All rights reserved.

Evaluation of Central Macular Thickness and Retinal Nerve Fiber Layer Thickness using Spectral Domain Optical Coherence Tomography in a Tertiary Care Hospital

PubMed Central

Saini, VK; Gupta, Saroj; Sharma, Anjali

2014-01-01

ABSTRACT Purpose: To evaluate the normative data of macular thickness and retinal nerve fiber layer thickness (RNFL) among normal subjects using spectral domain optical coherence tomography (OCT). Materials and methods: Normal subjects presenting to a tertiary medical hospital were included in the study. All patient underwent clinical examination followed by study of macular thickness and RN FL thick ness by spectral domain Topc on OCT. The data was collected and analyzed for variations in gender and age. The data was also compared with available literature. Results: Total numbers of patients enrolled in the study were 154 (308 eyes). Numbers of males were 79 (158 eyes) and numbers of females were 75 (150 eyes). The mean age among males was 42.67 ± 12.15 years and mean age among females was 42.88 ± 11.73 years. Overall the mean mac ular thickness (central 1 mm zone) with SD - OCT was 241.75 ± 17.3 microns. The mean macular volume was 7.6 cu. mm ± 0.33. On analysis of the RNFL thickness, we observed that the RNFL was thickest in the inferior quadrant (138.58) followed by superior (122.30) nasal (116.32) and temporal quadrant (73.04). Gender-wise comparison of the data revealed no statistically significant difference for age, macular thickness parameters, volume and RFNL values except outer temporal thickness among males and females. No age-related difference was noted in the above parameters. On comparison with available norma tive data from India and elsewhere, we found significant variations with different machines. Conclusion: The study is the first to provide normative data using SD-OCT from central India. The data from spectral domain OCT correlated well with the values obtained from similar studies with SD - OCT. Values obtained from time domain OCT machines are different and are not comparable. How to cite this article: Agarwal P, Saini VK, Gupta S, Sharma A. Evaluation of Central Macular Thickness and Retinal Nerve Fiber Layer Thickness using Spectral Domain Optical Coherence Tomography in a Tertiary Care Hospital. J Curr Glaucoma Pract 2014;8(2):75-81. PMID:26997813

Heteroepitaxy of orientation-patterned nonlinear optical materials

NASA Astrophysics Data System (ADS)

Tassev, Vladimir L.; Vangala, Shivashankar R.; Peterson, Rita D.; Snure, Michael

2018-03-01

We report some recent results on thick heteroepitaxial growth of GaP on GaAs substrates and on orientation-patterned (OP) GaAs templates conducted in a hot-wall horizontal quartz reactor for Hydride Vapor Phase Epitaxy. The growths on the plain substrates resulted in up to 500 μm thick GaP with smooth surface morphology (RMS < 1-2 nm) and high crystalline quality (FWHM = 100-150 arcsec), comparable to the quality of the related homoepitaxial growths of GaP on GaP. Up to 300 μm thick OPGaP quasi-phase matching structures with excellent domain fidelity were also heteroepitaxially grown with high reproducibility on OPGaAs templates in support of frequency conversion laser source development for the mid and longwave infrared. We studied the GaAsxP1-x ternary transition layer that forms between the growing film and the substrate. We also undertook steps to determine some important characteristics of heteroepitaxy such as thickness of the pseudomorphous growth and periodicity of the expected misfit dislocations. The formation of these and some other defects and their distribution within the layer thickness was also investigated. Samples were characterized by Nomarski optical microscopy, transmission optical measurements, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The focus was predominantly on the interface and, more precisely, on what influence the pre-growth surface treatment of the substrate has on the initial and the following stages of growth, as well on the mechanisms of the strain relaxation from the lattice and thermal mismatch between layer and substrate. The efforts to accommodate the growing film to the foreign substrate by engineering an intermediate buffer layer were extended to thick growths of GaAsxP1-x ternary with the idea to combine in one material the best of the nonlinear properties of GaP and GaAs that are strictly relevant to the pursued applications.

Choroidal thickness in Chinese patients with non-arteritic anterior ischemic optic neuropathy.

PubMed

Jiang, Libin; Chen, Lanlan; Qiu, Xiujuan; Jiang, Ran; Wang, Yaxing; Xu, Liang; Lai, Timothy Y Y

2016-08-31

Non-arteritic anterior ischemic optic neuropathy (NA-AION) is one of the most common types of ischemic optic neuropathy. Several recent studies suggested that abnormalities of choroidal thickness might be associated with NA-AION. The main objective of this case-control study was to evaluate whether choroidal thickness is an ocular risk factor for the development of NA-AION by evaluating the peripapillary and subfoveal choroidal thicknesses in affected Chinese patients. Forty-four Chinese patients with unilateral NA-AION were recruited and compared with 60 eyes of 60 normal age and refractive-error matched control subjects. Peripapillary and subfoveal choroidal thicknesses were measured by enhanced depth imaging optical coherence tomography. Choroidal thicknesses of eyes with NA-AION and unaffected fellow eyes were compared with normal controls. Choroidal thicknesses of NA-AION eyes with or without optic disc edema were also compared. The correlation between choroidal thickness and retinal nerve fiber layer (RNFL) thickness, logMAR best-corrected visual acuity (BCVA), and the mean deviation (MD) of Humphrey static perimetry in NA-AION eyes were analyzed. The peripapillary choroidal thicknesses at the nasal, nasal inferior and temporal inferior segments in NA-AION eyes with optic disc edema were significantly thicker compared with that of normal subjects (P < 0.05). There was no significant difference in the choroidal thicknesses between the unaffected fellow eyes of NA-AION patients and normal eyes of healthy controls; or between the NA-AION eyes with resolved optic disc edema and normal eyes (all P > 0.05). No significant correlation between choroidal thickness and RNFL thickness, logMAR BCVA and perimetry MD was found in eyes affected by NA-AION (all P > 0.05). Increase in peripapillary choroid thickness in some segments was found in NA-ION eyes with optic disc edema. However, our findings do not support the hypothesis that choroidal thickness is abnormal in Chinese patients with NA-AION compared with normal subjects with similar age and refractive error status.

Lamina cribrosa position and Bruch's membrane opening differences between anterior ischemic optic neuropathy and open-angle glaucoma.

PubMed

Rebolleda, Gema; Pérez-Sarriegui, Ane; Díez-Álvarez, Laura; De Juan, Victoria; Muñoz-Negrete, Francisco J

2018-06-01

To compare the optic nerve head morphology among primary open-angle glaucoma, non-arteritic anterior ischemic optic neuropathy eyes, their fellow healthy eyes and control eyes, using spectral-domain optical coherence tomography with enhanced depth imaging. Observational cross-sectional study including 88 eyes of 68 patients. In this study, 23 non-arteritic anterior ischemic optic neuropathy eyes, 17 fellow unaffected eyes, 25 primary open-angle glaucoma eyes, and 23 age-matched control eyes were included. Peripapillary retinal nerve fiber layer thickness and optic disk area were evaluated. Bruch's membrane opening diameter, optic cup depth, anterior lamina cribrosa depth, and prelaminar tissue thickness were assessed. Non-arteritic anterior ischemic optic neuropathy and primary open-angle glaucoma eyes had similar visual field mean deviation and peripapillary retinal nerve fiber layer thickness (P = 0.6 and P = 0.56, respectively). Bruch's membrane opening diameter was significantly larger in primary open-angle glaucoma eyes than in control eyes (P = 0.02). Lamina cribrosa and disk cup were deeper in eyes with primary open-angle glaucoma than both control and non-arteritic anterior ischemic optic neuropathy eyes (P < 0.001). Prelaminar tissue thickness was significantly thinner in primary open-angle glaucoma eyes than in non-arteritic anterior ischemic optic neuropathy eyes (P < 0.001). Lamina cribrosa was shallower in both non-arteritic anterior ischemic optic neuropathy and unaffected fellow eyes compared to healthy eyes (P < 0.001 and P = 0.04, respectively). No differences were found in the optic disk area. A forward lamina cribrosa placement and not a smaller disk could be involved in the pathogenesis of non-arteritic anterior ischemic optic neuropathy. A significantly larger Bruch's membrane opening diameter was found in primary open-angle glaucoma eyes compared with control eyes. This issue has clinical implications because Bruch's membrane opening has been considered a stable reference for disk-related measures.

Imaging slit-coupled surface plasmon polaritons using conventional optical microscopy.

PubMed

Mehfuz, R; Chowdhury, F A; Chau, K J

2012-05-07

We develop a technique that now enables surface plasmon polaritons (SPPs) coupled by nano-patterned slits in a metal film to be detected using conventional optical microscopy with standard objective lenses. The crux of this method is an ultra-thin polymer layer on the metal surface, whose thickness can be varied over a nanoscale range to enable controllable tuning of the SPP momentum. At an optimal layer thickness for which the SPP momentum matches the momentum of light emerging from the slit, the SPP coupling efficiency is enhanced about six times relative to that without the layer. The enhanced efficiency results in distinctive and bright plasmonic signatures near the slit visible by naked eye under an optical microscope. We demonstrate how this capability can be used for parallel measurement through a simple experiment in which the SPP propagation distance is extracted from a single microscope image of an illuminated array of nano-patterned slits on a metal surface. We also use optical microscopy to image the focal region of a plasmonic lens and obtain results consistent with a previously-reported results using near-field optical microscopy. Measurement of SPPs near a nano-slit using conventional and widely-available optical microscopy is an important step towards making nano-plasmonic device technology highly accessible and easy-to-use.

A multi-spectral approach to simultaneously retrieve above-cloud smoke optical depth and the optical and microphysical properties of underlying marine stratocumulus clouds using MODIS

NASA Astrophysics Data System (ADS)

Meyer, K.; Platnick, S. E.; Zhang, Z.

2013-12-01

Clouds, aerosols, and their interactions are widely considered to be key uncertainty components in our current understanding of the Earth's atmosphere and radiation budget. The work presented here is focused on the quasi-permanent marine boundary layer (MBL) clouds over the southeastern Atlantic Ocean, which underlie a near-persistent smoke layer produced from extensive biomass burning throughout the southern African savanna during austral winter. The absorption of the above-cloud smoke layer, which increases with decreasing wavelength, can introduce biases into the standard MODIS cloud optical and microphysical property retrievals of the underlying MBL clouds. This effect is more pronounced in the cloud optical thickness retrievals, which over ocean are derived from the wavelength channel centered near 0.86 μm (effective particle size retrievals are derived from the short and mid-wave IR channels at 1.6, 2.1, and 3.7 μm). Here, a new method is introduced to simultaneously retrieve the above-cloud smoke aerosol optical depth (AOD) and the unbiased cloud optical thickness (COT) and effective radius (CER) using multiple MODIS spectral channels in the visible and near- and shortwave-infrared. Preliminary retrieval results are shown, as are comparisons with other A-Train sensors.

An imager-based multispectral retrieval of above-cloud absorbing aerosol optical depth and the optical and microphysical properties of underlying marine stratocumulus clouds

NASA Astrophysics Data System (ADS)

Meyer, K.; Platnick, S. E.; Zhang, Z.

2014-12-01

Clouds, aerosols, and their interactions are widely considered to be key uncertainty components in our current understanding of the Earth's atmosphere and radiation budget. The work presented here is focused on the quasi-permanent marine boundary layer (MBL) clouds over the southeastern Atlantic Ocean, which underlie a near-persistent smoke layer produced from extensive biomass burning throughout the southern African savanna during austral winter. The absorption of the above-cloud smoke layer, which increases with decreasing wavelength, can introduce biases into imager-based cloud optical and microphysical property retrievals of the underlying MBL clouds. This effect is more pronounced for cloud optical thickness retrievals, which are typically derived from the visible or near-IR wavelength channels (effective particle size retrievals are derived from short and mid-wave IR channels that are less affected by aerosol absorption). Here, a new method is introduced to simultaneously retrieve the above-cloud smoke aerosol optical depth (AOD) and the unbiased cloud optical thickness (COT) and effective radius (CER) using multiple spectral channels in the visible and near- and shortwave-IR. The technique has been applied to MODIS, and retrieval results and statistics, as well as comparisons with other A-Train sensors, are shown.

Non-polar a-plane ZnO films grown on r-Al2O3 substrates using GaN buffer layers

NASA Astrophysics Data System (ADS)

Xu, C. X.; Chen, W.; Pan, X. H.; Chen, S. S.; Ye, Z. Z.; Huang, J. Y.

2016-09-01

In this work, GaN buffer layer has been used to grow non-polar a-plane ZnO films by laser-assisted and plasma-assisted molecular beam epitaxy. The thickness of GaN buffer layer ranges from ∼3 to 12 nm. The GaN buffer thickness effect on the properties of a-plane ZnO thin films is carefully investigated. The results show that the surface morphology, crystal quality and optical properties of a-plane ZnO films are strongly correlated with the thickness of GaN buffer layer. It was found that with 6 nm GaN buffer layer, a-plane ZnO films display the best crystal quality with X-ray diffraction rocking curve full-width at half-maximum of only 161 arcsec for the (101) reflection.

Thermal conductivity and thermal boundary resistance of atomic layer deposited high-k dielectric aluminum oxide, hafnium oxide, and titanium oxide thin films on silicon

NASA Astrophysics Data System (ADS)

Scott, Ethan A.; Gaskins, John T.; King, Sean W.; Hopkins, Patrick E.

2018-05-01

The need for increased control of layer thickness and uniformity as device dimensions shrink has spurred increased use of atomic layer deposition (ALD) for thin film growth. The ability to deposit high dielectric constant (high-k) films via ALD has allowed for their widespread use in a swath of optical, optoelectronic, and electronic devices, including integration into CMOS compatible platforms. As the thickness of these dielectric layers is reduced, the interfacial thermal resistance can dictate the overall thermal resistance of the material stack compared to the resistance due to the finite dielectric layer thickness. Time domain thermoreflectance is used to interrogate both the thermal conductivity and the thermal boundary resistance of aluminum oxide, hafnium oxide, and titanium oxide films on silicon. We calculate a representative design map of effective thermal resistances, including those of the dielectric layers and boundary resistances, as a function of dielectric layer thickness, which will be of great importance in predicting the thermal resistances of current and future devices.

NiCrNx interlayer thickness dependence of spectral performance and environmental durability of protected-silver mirrors

NASA Astrophysics Data System (ADS)

Xu, Xu; Li, Bincheng; He, Wenyan; Wang, Changjun; Wei, Ming

2018-04-01

Gemini-style protected-silver mirror (Sub / NiCrNx / Ag / NiCrNx / SiNx / Air) is a suitable choice for optical instruments requiring both long-term environmental durability and high broadband reflectance. Three Gemini-style protected-silver mirrors with NiCrNx interlayer thicknesses between 0.1 and 0.6 nm were prepared by magnetron sputtering, and the dependences of spectral properties and environmental durability of these protected-silver mirrors on the thickness of NiCrNx interlayer between the silver layer and SiNx layer were investigated in-depth. The reflectance, transmittance and total scattering loss measurements, optical microscope, and scanning electron microscope imaging were employed to characterize the spectral properties and surface morphology, and accelerated environmental tests, including humidity test and salt fog test, were applied to investigate the environmental durability. The experimental results showed that both optical and corrosion-resistant properties of protected-silver mirrors were NiCrNx interlayer thickness dependent, and an optimum NiCrNx interlayer thickness should be ˜0.3 nm for Gemini-style protected-silver mirrors to have reasonably both high reflectance in a broadband spectral range from visible to far infrared and good corrosion resistance for long-lifetime applications in harsh environments.

Nerve Fiber Layer Thickness and Characteristics Associated with Glaucoma in Community Living Older Adults: Prelude to a Screening Trial?

PubMed

Klein, Barbara E K; Johnson, Chris A; Meuer, Stacy M; Lee, Kyungmoo; Wahle, Andreas; Lee, Kristine E; Kulkarni, Amruta; Sonka, Milan; Abràmoff, Michael D; Klein, Ronald

2017-04-01

To examine the associations of nerve fiber layer (NFL) thickness with other ocular characteristics in older adults. Participants in the Beaver Dam Eye Study (2008-2010) underwent spectral domain optical coherence tomography (SD-OCT) scans of the optic nerve head, imaging of optic discs, frequency doubling technology (FDT) perimetry, measurement of intraocular pressure (IOP), and an interview concerning their history of glaucoma and use of drops to lower eye pressure. Self-reported histories of glaucoma and the use of drops to lower eye pressure were obtained at follow-up examinations (2014-2016). NFL thickness measured on OCTs varied by location around the optic nerve. Age was associated with mean NFL thickness. Mean NFL was thinnest in eyes with larger cup/disc (C/D) ratios. Horizontal hemifield defects or other optic nerve-field defects were associated with thinner NFL. NFL in persons who reported taking eye drops for high intraocular pressure was thinner compared to those not taking drops. After accounting for the presence of high intraocular pressure, large C/D ratios or hemifield defects, eyes with thinner NFL in the arcades were more likely (OR = 2.3 for 30 micron thinner NFL, p = 0.04) to have incident glaucoma at examination 5 years later. Retinal NFL thickness was associated with a new history of self-reported glaucoma 5 years later. A trial testing the usefulness of NFL as part of a screening battery for predicting glaucoma in those previously undiagnosed might lead to improved case finding and, ultimately, to diminishing the risk of visual field loss.

Optical gradients in a-Si:H thin films detected using real-time spectroscopic ellipsometry with virtual interface analysis

NASA Astrophysics Data System (ADS)

Junda, Maxwell M.; Karki Gautam, Laxmi; Collins, Robert W.; Podraza, Nikolas J.

2018-04-01

Virtual interface analysis (VIA) is applied to real time spectroscopic ellipsometry measurements taken during the growth of hydrogenated amorphous silicon (a-Si:H) thin films using various hydrogen dilutions of precursor gases and on different substrates during plasma enhanced chemical vapor deposition. A procedure is developed for optimizing VIA model configurations by adjusting sampling depth into the film and the analyzed spectral range such that model fits with the lowest possible error function are achieved. The optimal VIA configurations are found to be different depending on hydrogen dilution, substrate composition, and instantaneous film thickness. A depth profile in the optical properties of the films is then extracted that results from a variation in an optical absorption broadening parameter in a parametric a-Si:H model as a function of film thickness during deposition. Previously identified relationships are used linking this broadening parameter to the overall shape of the optical properties. This parameter is observed to converge after about 2000-3000 Å of accumulated thickness in all layers, implying that similar order in the a-Si:H network can be reached after sufficient thicknesses. In the early stages of growth, however, significant variations in broadening resulting from substrate- and processing-induced order are detected and tracked as a function of bulk layer thickness yielding an optical property depth profile in the final film. The best results are achieved with the simplest film-on-substrate structures while limitations are identified in cases where films have been deposited on more complex substrate structures.

FIBER AND INTEGRATED OPTICS: Optimization of optical film waveguides

NASA Astrophysics Data System (ADS)

Adamson, P. V.

1990-10-01

Theoretical investigations were made of the possibility of optimization of the effective thickness, of the optical confinement factor Γ1, and of the birefringence of a planar dielectric waveguide as a function of the waveguide parameter V and the waveguide asymmetry. For a given value of V it is possible to ensure higher values of Γ1, for an asymmetric waveguide than for a symmetric one. An approximate expression is proposed for the factor Γ1, of an asymmetric waveguide directly in terms of its thickness and the refractive indices of the layers.

Multi-layered fabrication of large area PDMS flexible optical light guide sheets

NASA Astrophysics Data System (ADS)

Green, Robert; Knopf, George K.; Bordatchev, Evgueni V.

2017-02-01

Large area polydimethylsiloxane (PDMS) flexible optical light guide sheets can be used to create a variety of passive light harvesting and illumination systems for wearable technology, advanced indoor lighting, non-planar solar light collectors, customized signature lighting, and enhanced safety illumination for motorized vehicles. These thin optically transparent micro-patterned polymer sheets can be draped over a flat or arbitrarily curved surface. The light guiding behavior of the optical light guides depends on the geometry and spatial distribution of micro-optical structures, thickness and shape of the flexible sheet, refractive indices of the constituent layers, and the wavelength of the incident light. A scalable fabrication method that combines soft-lithography, closed thin cavity molding, partial curing, and centrifugal casting is described in this paper for building thin large area multi-layered PDMS optical light guide sheets. The proposed fabrication methodology enables the of internal micro-optical structures (MOSs) in the monolithic PDMS light guide by building the optical system layer-by-layer. Each PDMS layer in the optical light guide can have the similar, or a slightly different, indices of refraction that permit total internal reflection within the optical sheet. The individual molded layers may also be defect free or micro-patterned with microlens or reflecting micro-features. In addition, the bond between adjacent layers is ensured because each layer is only partially cured before the next functional layer is added. To illustrate the scalable build-by-layers fabrication method a three-layer mechanically flexible illuminator with an embedded LED strip is constructed and demonstrated.

Ultra-high resolution profiles of macular intra-retinal layer thicknesses and associations with visual field defects in primary open angle glaucoma

NASA Astrophysics Data System (ADS)

Chen, Qi; Huang, Shenghai; Ma, Qingkai; Lin, Huiling; Pan, Mengmeng; Liu, Xinting; Lu, Fan; Shen, Meixiao

2017-02-01

The structural characteristics of the outer retinal layers in primary open angle glaucoma (POAG) are still controversial, and these changes, along with those in the inner retinal layers, could have clinical and/or pathophysiological significance. A custom-built ultra-high resolution optical coherence tomography (UHR-OCT) combined with an automated segmentation algorithm can image and measure the eight intra-retinal layers. The purpose of this study is to determine the thickness characteristics of the macular intra-retinal layers, especially the outer layers, in POAG patients. Thirty-four POAG patients (56 eyes) and 33 normal subjects (63 eyes) were enrolled. Thickness profiles of the eight intra-retinal layers along a 6-mm length centred on the fovea at the horizontal and vertical meridians were obtained and the regional thicknesses were compared between two groups. The associations between the thicknesses of each intra-retinal layer and the macular visual field (VF) sensitivity were then analysed. POAG affected not only the inner retinal layers but also the photoreceptor layers and retinal pigment epithelium of the outer retina. However, the VF loss was correlated mainly with the damage of the inner retinal layers. UHR-OCT with automated algorithm is a useful tool in detecting microstructural changes of macula with respect to the progression of glaucoma.

Changes in Inner and Outer Retinal Layer Thicknesses after Vitrectomy for Idiopathic Macular Hole: Implications for Visual Prognosis

PubMed Central

Hashimoto, Yuki; Saito, Wataru; Fujiya, Akio; Yoshizawa, Chikako; Hirooka, Kiriko; Mori, Shohei; Noda, Kousuke; Ishida, Susumu

2015-01-01

Purpose To investigate sequential post-operative thickness changes in inner and outer retinal layers in eyes with an idiopathic macular hole (MH). Methods Retrospective case series. Twenty-four eyes of 23 patients who had received pars plana vitrectomy (PPV) for the closure of MH were included in the study. Spectral domain optical coherence tomography C-scan was used to automatically measure the mean thickness of the inner and outer retinal layers pre-operatively and up to 6 months following surgery. The photoreceptor outer segment (PROS) length was measured manually and was used to assess its relationship with best-corrected visual acuity (BCVA). Results Compared with the pre-operative thickness, the inner layers significantly thinned during follow-up (P = 0.02), particularly in the parafoveal (P = 0.01), but not perifoveal, area. The post-operative inner layer thinning ranged from the ganglion cell layer to the inner plexiform layer (P = 0.002), whereas the nerve fiber layer was unaltered. Outer layer thickness was significantly greater post-operatively (P = 0.002), and especially the PROS lengthened not only in the fovea but also in the parafovea (P < 0.001). Six months after surgery, BCVA was significantly correlated exclusively with the elongated foveal PROS (R = 0.42, P = 0.03), but not with any of the other thickness parameters examined. Conclusions Following PPV for MH, retinal inner layers other than the nerve fiber layer thinned, suggestive of subclinical thickening in the inner layers where no cyst was evident pre-operatively. In contrast, retinal outer layer thickness significantly increased, potentially as a result of PROS elongation linking tightly with favorable visual prognosis in MH eyes. PMID:26291526

Preparation of TiO2/Ag/TiO2 (TAT) multilayer films with optical and electrical properties enhanced by using Cr-added Ag film

NASA Astrophysics Data System (ADS)

Loka, Chadrasekhar; Lee, Kee-Sun

2017-09-01

The dielectric-metal-dielectric tri-layer films have attracted much attention by virtue of their low-cost and high quality device performance as a transparent conductive electrode. Here, we report the deposition of Cr doped Ag films sandwiched between thin TiO2 layers and investigation on the surface microstructure, optical and electrical properties depending on the thickness of the Ag(Cr). The activation energy (1.18 eV) for grain growth of Ag was calculated from the Arrhenius plot using the law Dn -D0n = kt , which was comparable to the bulk diffusion of Ag. This result indicated the grain growth of Ag was effectively retarded by the Cr addition, which was presumed to related with blocking the surface and grain boundary diffusion due to Cr segregation. Based on thermal stability of Cr added Ag film, we deposited TiO2/Ag(Cr)/TiO2 (TAT) multilayer thin films and with a 10 nm thick Ag(Cr), the TAT films showed high optical transmittance in the visible region (94.2%), low electrical resistivity (8.66 × 10-5 Ω cm), and hence the high figure of merit 57.15 × 10-3 Ω-1 was achieved. The high transmittance of the TAT film was believed to be attributed to the low optical loss due to a reduction in the Ag layer thickness, the surface plasmon effect, and the electron scattering reduced by the Ag layer with a low electrical resistivity.

In situ evaluation of density, viscosity, and thickness of adsorbed soft layers by combined surface acoustic wave and surface plasmon resonance.

PubMed

Francis, Laurent A; Friedt, Jean-Michel; Zhou, Cheng; Bertrand, Patrick

2006-06-15

We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the waveguide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40 degrees C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.

Optical coating design for the annular mirrors of the Alpha I HF laser

NASA Astrophysics Data System (ADS)

Shellan, Jeffrey B.

The dielectric-coating design for the annular mirrors of the Alpha I HF laser is described along with the numerous other designs that were considered. The coatings were required to produce a 0-deg phase shift after one round trip, which involved reflections from six surfaces. Although novel high-reflectivity multilayer dielectric coatings satisfied this requirement, single-layer phase control coatings were preferred because the use of these greatly reduced coating layer-thickness control and thus resulted in significant program savings. Among the single-layer designs investigated, a coating consisting of a 0.06-micron-thick SiO layer was found to be sufficient for all surfaces except those of the rear cone, for which a 0.515-micron thick SiO layer was recommended. The metallic substrate selected was Au. These coatings were found to have a high damage threshold, provide the necessary polarization phase control, and to be quite forgiving to thickness deposition errors that were anticipated using existing chambers.

High Transparent and Conductive TiO2/Ag/TiO2 Multilayer Electrode Films Deposited on Sapphire Substrate

NASA Astrophysics Data System (ADS)

Loka, Chadrasekhar; Moon, Sung Whan; Choi, YiSik; Lee, Kee-Sun

2018-03-01

Transparent conducting oxides attract intense interests due to its diverse industrial applications. In this study, we report sapphire substrate-based TiO2/Ag/TiO2 (TAT) multilayer structure of indium-free transparent conductive multilayer coatings. The TAT thin films were deposited at room temperature on sapphire substrates and a rigorous analysis has been presented on the electrical and optical properties of the films as a function of Ag thickness. The optical and electrical properties were mainly controlled by the Ag mid-layer thickness of the TAT tri-layer. The TAT films showed high luminous transmittance 84% at 550 nm along with noteworthy low electrical resistance 3.65 × 10-5 Ω-cm and sheet resistance of 3.77 Ω/square, which is better are than those of amorphous ITO films and any sapphire-based dielectric/metal/dielectric multilayer stack. The carrier concentration of the films was increased with respect to Ag thickness. We obtained highest Hackke's figure of merit 43.97 × 10-3 Ω-1 from the TAT multilayer thin film with a 16 nm thick Ag mid-layer.

Influence of Filler Alloy Composition and Process Parameters on the Intermetallic Layer Thickness in Single-Sided Cold Metal Transfer Welding of Aluminum-Steel Blanks

NASA Astrophysics Data System (ADS)

Silvayeh, Zahra; Vallant, Rudolf; Sommitsch, Christof; Götzinger, Bruno; Karner, Werner; Hartmann, Matthias

2017-11-01

Hybrid components made of aluminum alloys and high-strength steels are typically used in automotive lightweight applications. Dissimilar joining of these materials is quite challenging; however, it is mandatory in order to produce multimaterial car body structures. Since especially welding of tailored blanks is of utmost interest, single-sided Cold Metal Transfer butt welding of thin sheets of aluminum alloy EN AW 6014 T4 and galvanized dual-phase steel HCT 450 X + ZE 75/75 was experimentally investigated in this study. The influence of different filler alloy compositions and welding process parameters on the thickness of the intermetallic layer, which forms between the weld seam and the steel sheet, was studied. The microstructures of the weld seam and of the intermetallic layer were characterized using conventional optical light microscopy and scanning electron microscopy. The results reveal that increasing the heat input and decreasing the cooling intensity tend to increase the layer thickness. The silicon content of the filler alloy has the strongest influence on the thickness of the intermetallic layer, whereas the magnesium and scandium contents of the filler alloy influence the cracking tendency. The layer thickness is not uniform and shows spatial variations along the bonding interface. The thinnest intermetallic layer (mean thickness < 4 µm) is obtained using the silicon-rich filler Al-3Si-1Mn, but the layer is more than twice as thick when different low-silicon fillers are used.

Evaluation of the lamina cribrosa in patients with diabetes mellitus using enhanced depth imaging spectral-domain optical coherence tomography.

PubMed

Akkaya, Serkan; Küçük, Bekir; Doğan, Hatice Karaköse; Can, Ertuğrul

2018-06-01

To compare the lamina cribrosa thickness and anterior lamina cribrosa depth between patients with and without diabetes mellitus and to investigate the effect of metabolic control and duration of diabetes mellitus on lamina cribrosa thickness and anterior lamina cribrosa depth using enhanced depth imaging spectral-domain optical coherence tomography. A total of 70 patients were enrolled in this cross-sectional study and were divided into the diabetes and control groups. Intraocular pressure, circumpapillary retinal nerve fibre layer thickness, anterior lamina cribrosa depth and lamina cribrosa thickness were compared between the groups. In the control group, the mean intraocular pressure was 14.6 ± 3.1 (mean ± standard deviation) mmHg, mean circumpapillary retinal nerve fibre layer thickness was 105.41 ± 5.86 μm, mean anterior lamina cribrosa depth was 420.3 ± 90.2 μm and mean lamina cribrosa thickness was 248.5 ± 5.4 μm. In the diabetes group, the mean intraocular pressure was 13.9 ± 2.2 mmHg, mean circumpapillary retinal nerve fibre layer thickness was 101.37 ± 10.97 μm, mean anterior lamina cribrosa depth was 351.4 ± 58.6 μm and mean lamina cribrosa thickness was 271.6 ± 33.9 μm. Lamina cribrosa thickness was significantly higher ( p < 0.001) and anterior lamina cribrosa depth was significantly lower ( p = 0.003) in the diabetes group. There was no statistical difference between the groups with regard to age, spherical equivalent, axial length, circumpapillary retinal nerve fibre layer thickness and intraocular pressure ( p  = 0.69, 0.26, 0.47, 0.06 and 0.46, respectively). Lamina cribrosa thickness and anterior lamina cribrosa depth were not significantly correlated with duration of diabetes mellitus (lamina cribrosa thickness: r = -0.078, p = 0.643; anterior lamina cribrosa depth: r = -0.062, p = 0.710) or HbA1c levels (lamina cribrosa thickness: r = -0.078, p = 0.596; anterior lamina cribrosa depth: r = -0.228, p = 0.169). The results of this study showed that the optical coherence tomography measurement of lamina cribrosa revealed thicker and more anteriorly positioned lamina cribrosa for patients with diabetes mellitus compared with those for healthy controls.

Reproducibility of peripapillary retinal nerve fiber layer thickness with spectral domain cirrus high-definition optical coherence tomography in normal eyes.

PubMed

Hong, Samin; Kim, Chan Yun; Lee, Won Seok; Seong, Gong Je

2010-01-01

To assess the reproducibility of the new spectral domain Cirrus high-definition optical coherence tomography (HD-OCT; Carl Zeiss Meditec, Dublin, CA, USA) for analysis of peripapillary retinal nerve fiber layer (RNFL) thickness in healthy eyes. Thirty healthy Korean volunteers were enrolled. Three optic disc cube 200 x 200 Cirrus HD-OCT scans were taken on the same day in discontinuous sessions by the same operator without using the repeat scan function. The reproducibility of the calculated RNFL thickness and probability code were determined by the intraclass correlation coefficient (ICC), coefficient of variation (CV), test-retest variability, and Fleiss' generalized kappa (kappa). Thirty-six eyes were analyzed. For average RNFL thickness, the ICC was 0.970, CV was 2.38%, and test-retest variability was 4.5 microm. For all quadrants except the nasal, ICCs were 0.972 or higher and CVs were 4.26% or less. Overall test-retest variability ranged from 5.8 to 8.1 microm. The kappa value of probability codes for average RNFL thickness was 0.690. The kappa values of quadrants and clock-hour sectors were lower in the nasal areas than in other areas. The reproducibility of Cirrus HD-OCT to analyze peripapillary RNFL thickness in healthy eyes was excellent compared with the previous reports for time domain Stratus OCT. For the calculated RNFL thickness and probability code, variability was relatively higher in the nasal area, and more careful analyses are needed.

Effect of thickness on physical properties of electron beam vacuum evaporated CdZnTe thin films for tandem solar cells

NASA Astrophysics Data System (ADS)

Chander, Subhash; Dhaka, M. S.

2016-10-01

The thickness and physical properties of electron beam vacuum evaporated CdZnTe thin films have been optimized in the present work. The films of thickness 300 nm and 400 nm were deposited on ITO coated glass substrates and subjected to different characterization tools like X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) to investigate the structural, optical, electrical and surface morphological properties respectively. The XRD results show that the as-deposited CdZnTe thin films have zinc blende cubic structure and polycrystalline in nature with preferred orientation (111). Different structural parameters are also evaluated and discussed. The optical study reveals that the optical transition is found to be direct and energy band gap is decreased for higher thickness. The transmittance is found to increase with thickness and red shift observed which is suitable for CdZnTe films as an absorber layer in tandem solar cells. The current-voltage characteristics of deposited films show linear behavior in both forward and reverse directions as well as the conductivity is increased for higher film thickness. The SEM studies show that the as-deposited CdZnTe thin films are found to be homogeneous, uniform, small circle-shaped grains and free from crystal defects. The experimental results confirm that the film thickness plays an important role to optimize the physical properties of CdZnTe thin films for tandem solar cell applications as an absorber layer.

Broader color gamut of color-modulating optical coating display based on indium tin oxide and phase change materials.

PubMed

Ni, Zhigang; Mou, Shenghong; Zhou, Tong; Cheng, Zhiyuan

2018-05-01

A color-modulating optical coating display based on phase change materials (PCM) and indium tin oxide (ITO) is fabricated and analyzed. We demonstrate that altering the thickness of top-ITO in this PCM-based display device can effectively change color. The significant role of the top-ITO layer in the thin-film interference in this multilayer system is confirmed by experiment as well as simulation. The ternary-color modulation of devices with only 5 nano thin layer of phase change material is achieved. Furthermore, simulation work demonstrates that a stirringly broader color gamut can be obtained by introducing the control of the top-ITO thickness.

Influence of interface layer on optical properties of sub-20 nm-thick TiO2 films

NASA Astrophysics Data System (ADS)

Shi, Yue-Jie; Zhang, Rong-Jun; Li, Da-Hai; Zhan, Yi-Qiang; Lu, Hong-Liang; Jiang, An-Quan; Chen, Xin; Liu, Juan; Zheng, Yu-Xiang; Wang, Song-You; Chen, Liang-Yao

2018-02-01

The sub-20 nm ultrathin titanium dioxide (TiO2) films with tunable thickness were deposited on Si substrates by atomic layer deposition (ALD). The structural and optical properties were acquired by transmission electron microscopy, atomic force microscopy and spectroscopic ellipsometry. Afterwards, a constructive and effective method of analyzing interfaces by applying two different optical models consisting of air/TiO2/Ti x Si y O2/Si and air/effective TiO2 layer/Si, respectively, was proposed to investigate the influence of interface layer (IL) on the analysis of optical constants and the determination of band gap of TiO2 ultrathin films. It was found that two factors including optical constants and changing components of the nonstoichiometric IL could contribute to the extent of the influence. Furthermore, the investigated TiO2 ultrathin films of 600 ALD cycles were selected and then annealed at the temperature range of 400-900 °C by rapid thermal annealing. Thicker IL and phase transition cause the variation of optical properties of TiO2 films after annealing and a shorter electron relaxation time reveals the strengthened electron-electron and electron-phonon interactions in the TiO2 ultrathin films at high temperature. The as-obtained results in this paper will play a role in other studies of high dielectric constants materials grown on Si substrates and in the applications of next generation metal-oxide-semiconductor devices.

Polished polymide substrate

DOEpatents

Farah, John; Sudarshanam, Venkatapuram S.

2003-05-13

Polymer substrates, in particular polyimide substrates, and polymer laminates for optical applications are described. Polyimide substrates are polished on one or both sides depending on their thickness, and single-layer or multi-layer waveguide structures are deposited on the polished polyimide substrates. Optical waveguide devices are machined by laser ablation using a combination of IR and UV lasers. A waveguide-fiber coupler with a laser-machined groove for retaining the fiber is also disclosed.

Evaluation of Macular Ganglion Cell-inner Plexiform Layer and Choroid in Psoriasis Patients Using Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography.

PubMed

Ersan, Ismail; Kilic, Sevilay; Arikan, Sedat; Kara, Selcuk; Işik, Selda; Gencer, Baran; Ogretmen, Zerrin

2017-08-01

To evaluate changes in the thickness of the central macula, macular ganglion cell-inner plexiform layer (mGCIPL), and subfoveal choroid in patients with psoriasis using spectral domain optical coherence tomography (SD-OCT). The measurements of macular, mGCIPL thicknesses and subfoveal choroidal thickness (SFCT) obtained by SD-OCT of psoriasis patients (n = 46). These measurements were compared with those of 50 healthy controls. The macular, mGCIPL, and choroidal thicknesses did not differ between the controls and psoriatic subjects (p>0.05). When the patients were divided into two distinct groups, only the SFCT was significantly thicker in the severe psoriasis group compared with the mild psoriasis group (p = 0.003). These findings suggest that choroidal alterations are seen without macular changes in patients with psoriasis. Severe psoriasis appears to be related to increases in SFCT as a consequence of possible inflammatory cascades that are part of the disease's pathogenesis.

Effects of fixture rotation on coating uniformity for high-performance optical filter fabrication

NASA Astrophysics Data System (ADS)

Rubin, Binyamin; George, Jason; Singhal, Riju

2018-04-01

Coating uniformity is critical in fabricating high-performance optical filters by various vacuum deposition methods. Simple and planetary rotation systems with shadow masks are used to achieve the required uniformity [J. B. Oliver and D. Talbot, Appl. Optics 45, 13, 3097 (2006); O. Lyngnes, K. Kraus, A. Ode and T. Erguder, in `Method for Designing Coating Thickness Uniformity Shadow Masks for Deposition Systems with a Planetary Fixture', 2014 Technical Conference Proceedings, Optical Coatings, August 13, 2014, DOI: 10.14332/svc14.proc.1817.]. In this work, we discuss the effect of rotation pattern and speed on thickness uniformity in an ion beam sputter deposition system. Numerical modeling is used to determine statistical distribution of random thickness errors in coating layers. The relationship between thickness tolerance and production yield are simulated theoretically and demonstrated experimentally. Production yields for different optical filters produced in an ion beam deposition system with planetary rotation are presented. Single-wavelength and broadband optical monitoring systems were used for endpoint monitoring during filter deposition. Limitations of thickness tolerances that can be achieved in systems with planetary rotation are shown. Paths for improving production yield in an ion beam deposition system are described.

Thickness dependence of crystal and optical characterization on ZnO thin film grown by atomic layer deposition

NASA Astrophysics Data System (ADS)

Baek, Seung-Hye; Lee, Hyun-Jin; Lee, Sung-Nam

2018-06-01

We studied the thickness dependence of the crystallographic and optical properties of ZnO thin films grown on c-plane sapphire substrate using atomic layer deposition. High-resolution X-ray diffraction (HR-XRD) revealed two peaks at 34.5° and 36.2° in the initial growth stage of ZnO on the sapphire substrate, corresponding to the (002) and (101) ZnO planes, respectively. However, as the thickness of the ZnO film increased, the XRD intensity of the (002) ZnO peak increased drastically, compared with that of the (101) ZnO peak. This indicated that (002) and (101) ZnO were simultaneously grown on the c-plane sapphire substrate in the initial growth stage, and that (002) ZnO was predominantly grown with the increase in the thickness of ZnO film. The ZnO thin film presented an anisotropic surface structure at the initial stage, whereas the isotropic surface morphology was developed with an increase in the film thickness of ZnO. These observations were consistent with the HR-XRD results.

Fabrication and Theoretical Evaluation of Microlens Arrays on Layered Polymers

NASA Astrophysics Data System (ADS)

Oder, Tom; McMaster, Michael; Merlo, Corey; Bagheri, Camron; Reakes, Clayton; Petrus, Joshua; Li, Dingqiang; Crescimanno, Michael; Andrews, James

2014-03-01

Arrays of microlens were fabricated on nano-layered polymers using reactive ion etching. Semi hemispherical patterns with diameters ranging from 20 to 80 micrometers were first formed on a thick photoresist film that was spin-coated on the layered polymers using standard photolithographic process employing a gray scale glass mask. These patterns were then transferred to the polymers using dry etching in a reactive ion etching system. The optimized etch condition included a mixture of sulfur hexafluoride and oxygen, which resulted in an etch depth of 5 micrometers and successfully exposed the individual sub-micron thick layers in the polymers. Physical characterization of the microlens arrays was done using atomic force microscope and scanning electron microscope. We combine basic physical optics theory with the transfer matrix analysis of optical transport in nano-layered polymers to address subtleties in the chromatic response of microlenses made from these materials. In particular this method explains the len's behavior in and around the reflection band of the materials. We wish to acknowledge support of funds from NSF through its Center for Layered Polymeric Systems (CLiPS) at Case Western Reserve University.

Broadband nonlinear optical response in multi-layer black phosphorus: an emerging infrared and mid-infrared optical material.

PubMed

Lu, S B; Miao, L L; Guo, Z N; Qi, X; Zhao, C J; Zhang, H; Wen, S C; Tang, D Y; Fan, D Y

2015-05-04

Black phosphorous (BP), the most thermodynamically stable allotrope of phosphorus, is a high-mobility layered semiconductor with direct band-gap determined by the number of layers from 0.3 eV (bulk) to 2.0 eV (single layer). Therefore, BP is considered as a natural candidate for broadband optical applications, particularly in the infrared (IR) and mid-IR part of the spectrum. The strong light-matter interaction, narrow direct band-gap, and wide range of tunable optical response make BP as a promising nonlinear optical material, particularly with great potentials for infrared and mid-infrared opto-electronics. Herein, we experimentally verified its broadband and enhanced saturable absorption of multi-layer BP (with a thickness of ~10 nm) by wide-band Z-scan measurement technique, and anticipated that multi-layer BPs could be developed as another new type of two-dimensional saturable absorber with operation bandwidth ranging from the visible (400 nm) towards mid-IR (at least 1930 nm). Our results might suggest that ultra-thin multi-layer BP films could be potentially developed as broadband ultra-fast photonics devices, such as passive Q-switcher, mode-locker, optical switcher etc.

Optical measurements of degradation in aircraft boundary layers

NASA Technical Reports Server (NTRS)

Kelsall, D.

1980-01-01

Visible wavelength measurements of the degradation of optical beams when transmitted through the thin aerodynamic boundary layers around an aircraft are reviewed. The measured results indicated degradation levels for the KC-135 airplanes between 0.10 to 0.13 lambda increasing to 0.18 lambda (rms wavefront distortion). For the Lear Jet, degradation with a 25 mm diameter optics was roughly 0.07 lambda. The corresponding infinite aperture degradation levels are also calculated. The corresponding measured correlation lengths of roughly 12 mm for the KC-135 aircraft and 6 mm for the Lear Jet scale to roughly 20 and 25 mm, respectively, for infinite apertures. These boundary layer correlation lengths do not appear to reflect the different boundary layer thicknesses on the two different aircraft.

Transient Infrared Emission Spectroscopy

NASA Astrophysics Data System (ADS)

Jones, Roger W.; McClelland, John F.

1989-12-01

Transient Infrared Emission Spectroscopy (TIRES) is a new technique that reduces the occurrence of self-absorption in optically thick solid samples so that analytically useful emission spectra may be observed. Conventional emission spectroscopy, in which the sample is held at an elevated, uniform temperature, is practical only for optically thin samples. In thick samples the emission from deep layers of the material is partially absorbed by overlying layers.1 This self-absorption results in emission spectra from most optically thick samples that closely resemble black-body spectra. The characteristic discrete emission bands are severely truncated and altered in shape. TIRES bypasses this difficulty by using a laser to heat only an optically thin surface layer. The increased temperature of the layer is transient since the layer will rapidly cool and thicken by thermal diffusion; hence the emission collection must be correlated with the laser heating. TIRES may be done with both pulsed and cw lasers.2,3 When a pulsed laser is used, the spectrometer sampling must be synchronized with the laser pulsing so that only emission during and immediately after each laser pulse is observed.3 If a cw laser is used, the sample must move rapidly through the beam. The hot, transient layer is then in the beam track on the sample at and immediately behind the beam position, so the spectrometer field of view must be limited to this region near the beam position.2 How much self-absorption the observed emission suffers depends on how thick the heated layer has grown by thermal diffusion when the spectrometer samples the emission. Use of a pulsed laser synchronized with the spectrometer sampling readily permits reduction of the time available for heat diffusion to about 100 acs .3 When a cw laser is used, the heat-diffusion time is controlled by how small the spectrometer field of view is and by how rapidly the sample moves past within this field. Both a very small field of view and a very high sample speed would be required to attain a diffusion time of 100 μs. Accordingly, pulsed-laser TIRES generally produces spectra suffering from less self-absorption than cw-laser TIRES does, but the cw-laser technique is technically much simpler since no synchronization is required.

Fabrication of GaAs/Al0.3Ga0.7As multiple quantum well nanostructures on (100) si substrate using a 1-nm InAs relief layer.

PubMed

Oh, H J; Park, S J; Lim, J Y; Cho, N K; Song, J D; Lee, W; Lee, Y J; Myoung, J M; Choi, W J

2014-04-01

Nanometer scale thin InAs layer has been incorporated between Si (100) substrate and GaAs/Al0.3Ga0.7As multiple quantum well (MQW) nanostructure in order to reduce the defects generation during the growth of GaAs buffer layer on Si substrate. Observations based on atomic force microscopy (AFM) and transmission electron microscopy (TEM) suggest that initiation and propagation of defect at the Si/GaAs interface could be suppressed by incorporating thin (1 nm in thickness) InAs layer. Consequently, the microstructure and resulting optical properties improved as compared to the MQW structure formed directly on Si substrate without the InAs layer. It was also observed that there exists some limit to the desirable thickness of the InAs layer since the MQW structure having thicker InAs layer (4 nm-thick) showed deteriorated properties.

Glaucoma diagnosis by mapping macula with Fourier domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Tan, Ou; Lu, Ake; Chopra, Vik; Varma, Rohit; Hiroshi, Ishikawa; Schuman, Joel; Huang, David

2008-03-01

A new image segmentation method was developed to detect macular retinal sub-layers boundary on newly-developed Fourier-Domain Optical Coherence Tomography (FD-OCT) with macular grid scan pattern. The segmentation results were used to create thickness map of macular ganglion cell complex (GCC), which contains the ganglion cell dendrites, cell bodies and axons. Overall average and several pattern analysis parameters were defined on the GCC thickness map and compared for the diagnosis of glaucoma. Intraclass correlation (ICC) is used to compare the reproducibility of the parameters. Area under receiving operative characteristic curve (AROC) was calculated to compare the diagnostic power. The result is also compared to the output of clinical time-domain OCT (TD-OCT). We found that GCC based parameters had good repeatability and comparable diagnostic power with circumpapillary nerve fiber layer (cpNFL) thickness. Parameters based on pattern analysis can increase the diagnostic power of GCC macular mapping.

Retinal and Optic Nerve Degeneration in Patients with Multiple Sclerosis Followed up for 5 Years.

PubMed

Garcia-Martin, Elena; Ara, Jose R; Martin, Jesus; Almarcegui, Carmen; Dolz, Isabel; Vilades, Elisa; Gil-Arribas, Laura; Fernandez, Francisco J; Polo, Vicente; Larrosa, Jose M; Pablo, Luis E; Satue, Maria

2017-05-01

To quantify retinal nerve fiber layer (RNFL) changes in patients with multiple sclerosis (MS) and healthy controls with a 5-year follow-up and to analyze correlations between disability progression and RNFL degeneration. Observational and longitudinal study. One hundred patients with relapsing-remitting MS and 50 healthy controls. All participants underwent a complete ophthalmic and electrophysiologic exploration and were re-evaluated annually for 5 years. Visual acuity (Snellen chart), color vision (Ishihara pseudoisochromatic plates), visual field examination, optical coherence tomography (OCT), scanning laser polarimetry (SLP), and visual evoked potentials. Expanded Disability Status Scale (EDSS) scores, disease duration, treatments, prior optic neuritis episodes, and quality of life (QOL; based on the 54-item Multiple Sclerosis Quality of Life Scale score). Optical coherence tomography (OCT) revealed changes in all RNFL thicknesses in both groups. In the MS group, changes were detected in average thickness and in the mean deviation using the GDx-VCC nerve fiber analyzer (Laser Diagnostic Technologies, San Diego, CA) and in the P100 latency of visual evoked potentials; no changes were detected in visual acuity, color vision, or visual fields. Optical coherence tomography showed greater differences in the inferior and temporal RNFL thicknesses in both groups. In MS patients only, OCT revealed a moderate correlation between the increase in EDSS and temporal and superior RNFL thinning. Temporal RNFL thinning based on OCT results was correlated moderately with decreased QOL. Multiple sclerosis patients exhibit a progressive axonal loss in the optic nerve fiber layer. Retinal nerve fiber layer thinning based on OCT results is a useful marker for assessing MS progression and correlates with increased disability and reduced QOL. Copyright © 2017 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Effect of race, age, and axial length on optic nerve head parameters and retinal nerve fiber layer thickness measured by Cirrus HD-OCT.

PubMed

Knight, O'Rese J; Girkin, Christopher A; Budenz, Donald L; Durbin, Mary K; Feuer, William J

2012-03-01

To determine the effect of race, demographic, and ocular variables on optic nerve head and retinal nerve fiber layer (RNFL) thickness measurements using spectral-domain optical coherence tomography. In a cross-sectional observational study, 284 normal subjects aged 18 to 84 years were evaluated at 7 sites using Cirrus HD-OCT. Disc area, rim area, average cup-disc ratio, vertical cup-disc ratio, cup volume, and average, temporal, superior, nasal, and inferior RNFL thicknesses were calculated. The main outcome measures were associations between Cirrus HD-OCT optic nerve head and RNFL measurements and age, sex, and race. The 284 subjects self-identified as being of European (122), Chinese (63), African (51), or Hispanic (35) descent. After adjusting for the effect of age, there was a statistically significant difference among racial groups for all optic nerve head and RNFL parameters (all P ≤ .005) except rim area (P = .22). Rim area, average cup-disc ratio, vertical cup-disc ratio, and cup volume were moderately associated with disc area (r(2) = 0.15, 0.33, 0.33, and 0.37, respectively). After a linear adjustment for disc area, there was no statistically significant difference among racial groups for any optic nerve head parameter. Individuals of European descent had thinner RNFL measurements except in the temporal quadrant. There are racial differences in optic disc area, average cup-disc ratio, vertical cup-disc ratio, cup volume, and RNFL thickness as measured by Cirrus HD-OCT. These differences should be considered when using Cirrus HD-OCT to assess for glaucomatous damage in differing population groups.

Effect of Race, Age, and Axial Length on Optic Nerve Head Parameters and Retinal Nerve Fiber Layer Thickness Measured by Cirrus HD-OCT

PubMed Central

Knight, O’Rese J.; Girkin, Christopher A.; Budenz, Donald L.; Durbin, Mary K.; Feuer, William J.

2017-01-01

Objective To determine the effect of race, demographic, and ocular variables on optic nerve head and retinal nerve fiber layer (RNFL) thickness measurements using spectral-domain optical coherence tomography. Methods In a cross-sectional observational study, 284 normal subjects aged 18 to 84 years were evaluated at 7 sites using Cirrus HD-OCT. Disc area, rim area, average cup-disc ratio, vertical cup-disc ratio, cup volume, and average, temporal, superior, nasal, and inferior RNFL thicknesses were calculated. The main outcome measures were associations between Cirrus HD-OCT optic nerve head and RNFL measurements and age, sex, and race. Results The 284 subjects self-identified as being of European (122), Chinese (63), African (51), or Hispanic (35) descent. After adjusting for the effect of age, there was a statistically significant difference among racial groups for all optic nerve head and RNFL parameters (all P≤.005) except rim area (P=.22). Rim area, average cup-disc ratio, vertical cup-disc ratio, and cup volume were moderately associated with disc area (r2=0.15, 0.33, 0.33, and 0.37, respectively). After a linear adjustment for disc area, there was no statistically significant difference among racial groups for any optic nerve head parameter. Individuals of European descent had thinner RNFL measurements except in the temporal quadrant. Conclusions There are racial differences in optic disc area, average cup-disc ratio, vertical cup-disc ratio, cup volume, and RNFL thickness as measured by Cirrus HD-OCT. These differences should be considered when using Cirrus HD-OCT to assess for glaucomatous damage in differing population groups. PMID:22411660

Influence of optic disc size on the diagnostic performance of macular ganglion cell complex and peripapillary retinal nerve fiber layer analyses in glaucoma.

PubMed

Cordeiro, Daniela Valença; Lima, Verônica Castro; Castro, Dinorah P; Castro, Leonardo C; Pacheco, Maria Angélica; Lee, Jae Min; Dimantas, Marcelo I; Prata, Tiago Santos

2011-01-01

To evaluate the influence of optic disc size on the diagnostic accuracy of macular ganglion cell complex (GCC) and conventional peripapillary retinal nerve fiber layer (pRNFL) analyses provided by spectral domain optical coherence tomography (SD-OCT) in glaucoma. Eighty-two glaucoma patients and 30 healthy subjects were included. All patients underwent GCC (7 × 7 mm macular grid, consisting of RNFL, ganglion cell and inner plexiform layers) and pRNFL thickness measurement (3.45 mm circular scan) by SD-OCT. One eye was randomly selected for analysis. Initially, receiver operating characteristic (ROC) curves were generated for different GCC and pRNFL parameters. The effect of disc area on the diagnostic accuracy of these parameters was evaluated using a logistic ROC regression model. Subsequently, 1.5, 2.0, and 2.5 mm(2) disc sizes were arbitrarily chosen (based on data distribution) and the predicted areas under the ROC curves (AUCs) and sensitivities were compared at fixed specificities for each. Average mean deviation index for glaucomatous eyes was -5.3 ± 5.2 dB. Similar AUCs were found for the best pRNFL (average thickness = 0.872) and GCC parameters (average thickness = 0.824; P = 0.19). The coefficient representing disc area in the ROC regression model was not statistically significant for average pRNFL thickness (-0.176) or average GCC thickness (0.088; P ≥ 0.56). AUCs for fixed disc areas (1.5, 2.0, and 2.5 mm(2)) were 0.904, 0.891, and 0.875 for average pRNFL thickness and 0.834, 0.842, and 0.851 for average GCC thickness, respectively. The highest sensitivities - at 80% specificity for average pRNFL (84.5%) and GCC thicknesses (74.5%) - were found with disc sizes fixed at 1.5 mm(2) and 2.5 mm(2). Diagnostic accuracy was similar between pRNFL and GCC thickness parameters. Although not statistically significant, there was a trend for a better diagnostic accuracy of pRNFL thickness measurement in cases of smaller discs. For GCC analysis, an inverse effect was observed.

New ultrathin film heterostructure for low-e application by sputtering technique: a theoretical and experimental study

NASA Astrophysics Data System (ADS)

Ruíz-Robles, M. A.; Abundiz-Cisneros, N.; Bender-Pérez, C. E.; Gutiérrez-Lazos, C. D.; Fundora-Cruz, A.; Solís-Pomar, F.; Pérez-Tijerina, E.

2018-03-01

The design and optical characterization by UV–vis transmittance of ultrathin low-emissivity (low-e) windows by reactive sputtering are reported. Two heterostructures on a glass substrate were considered for the low-e windows. The first heterostructure is Si3N4/TiO2/ZnO/Ag/SnO2/Si3N4 and the second is Si3N4/Ag/Si3N4. The transmittance and reflectance of these heterostructures were simulated to determine the required thickness of each layer. The first heterostructure exhibited maximum transmittance of 85% at 550 nm, slightly higher than the one determined by simulation and less than 50% transmittance in the near-infrared region (900 nm). The second heterostructure exhibited transmittance greater than 86% at 550 nm and <50% transmittance in the near-infrared region. In addition, we found that the bandwidth and maximum position of the transmittance depend on the Si3N4 layer thickness. Specifically, the thickness of the first Si3N4 layer allows the modulation of the transmittance bandwidth and the thickness of the second Si3N4 layer allows the modulation of the maximum position. The low-e windows were protected by the deposition of an ultrathin film of NiCr alloy (Ni 80%, Cr 20%) that preserved the optical characteristics and decreased the maximum of the transmittance only by 3%.

Optical measurements of absorption changes in two-layered diffusive media

NASA Astrophysics Data System (ADS)

Fabbri, Francesco; Sassaroli, Angelo; Henry, Michael E.; Fantini, Sergio

2004-04-01

We have used Monte Carlo simulations for a two-layered diffusive medium to investigate the effect of a superficial layer on the measurement of absorption variations from optical diffuse reflectance data processed by using: (a) a multidistance, frequency-domain method based on diffusion theory for a semi-infinite homogeneous medium; (b) a differential-pathlength-factor method based on a modified Lambert-Beer law for a homogeneous medium and (c) a two-distance, partial-pathlength method based on a modified Lambert-Beer law for a two-layered medium. Methods (a) and (b) lead to a single value for the absorption variation, whereas method (c) yields absorption variations for each layer. In the simulations, the optical coefficients of the medium were representative of those of biological tissue in the near-infrared. The thickness of the first layer was in the range 0.3-1.4 cm, and the source-detector distances were in the range 1-5 cm, which is typical of near-infrared diffuse reflectance measurements in tissue. The simulations have shown that (1) method (a) is mostly sensitive to absorption changes in the underlying layer, provided that the thickness of the superficial layer is ~0.6 cm or less; (2) method (b) is significantly affected by absorption changes in the superficial layer and (3) method (c) yields the absorption changes for both layers with a relatively good accuracy of ~4% for the superficial layer and ~10% for the underlying layer (provided that the absorption changes are less than 20-30% of the baseline value). We have applied all three methods of data analysis to near-infrared data collected on the forehead of a human subject during electroconvulsive therapy. Our results suggest that the multidistance method (a) and the two-distance partial-pathlength method (c) may better decouple the contributions to the optical signals that originate in deeper tissue (brain) from those that originate in more superficial tissue layers.

High Performance Photodiode Based on p-Si/Copper Phthalocyanine Heterojunction.

PubMed

Zhong, Junkang; Peng, Yingquan; Zheng, Tingcai; Lv, Wenli; Ren, Qiang; Fobao, Huang; Ying, Wang; Chen, Zhen; Tang, Ying

2016-06-01

Hybrid organic-inorganic (HOI) photodiodes have both advantages of organic and inorganic materials, including compatibility of traditional Si-based semiconductor technology, low cost, high photosensitivity and high reliability, showing tremendous value in application. Red light sensitive HOI photodiodes based on the p-Si/copper phthalocyanine (CuPc) hetrojunction were fabricated and characterized. The effects of CuPc layer thickness on the performance were investigated, and an optimal layer thickness of around 30 nm was determined. An analytical expression is derived to describe the measured thickness dependence of the saturation photocurrent. For the device with optimal CuPc layer thickness, a photoresponsivity of 0.35 A/W and external quantum efficiency of 70% were obtained at 9 V reverse voltage bias and 655 nm light illumination of 0.451 mW. Furthermore, optical power dependent performances were investigated.

Effect of stratospheric aerosol layers on the TOMS/SBUV ozone retrieval

NASA Technical Reports Server (NTRS)

Torres, O.; Ahmad, Zia; Pan, L.; Herman, J. R.; Bhartia, P. K.; Mcpeters, R.

1994-01-01

An evaluation of the optical effects of stratospheric aerosol layers on total ozone retrieval from space by the TOMS/SBUV type instruments is presented here. Using the Dave radiative transfer model we estimate the magnitude of the errors in the retrieved ozone when polar stratospheric clouds (PSC's) or volcanic aerosol layers interfere with the measurements. The largest errors are produced by optically thick water ice PSC's. Results of simulation experiments on the effect of the Pinatubo aerosol cloud on the Nimbus-7 and Meteor-3 TOMS products are presented.

Spectroscopic Ellipsometry Studies of Ag and ZnO Thin Films and Their Interfaces for Thin Film Photovoltaics

NASA Astrophysics Data System (ADS)

Sainju, Deepak

Many modern optical and electronic devices, including photovoltaic devices, consist of multilayered thin film structures. Spectroscopic ellipsometry (SE) is a critically important characterization technique for such multilayers. SE can be applied to measure key parameters related to the structural, optical, and electrical properties of the components of multilayers with high accuracy and precision. One of the key advantages of this non-destructive technique is its capability of monitoring the growth dynamics of thin films in-situ and in real time with monolayer level precision. In this dissertation, the techniques of SE have been applied to study the component layer materials and structures used as back-reflectors and as the transparent contact layers in thin film photovoltaic technologies, including hydrogenated silicon (Si:H), copper indium-gallium diselenide (CIGS), and cadmium telluride (CdTe). The component layer materials, including silver and both intrinsic and doped zinc oxide, are fabricated on crystalline silicon and glass substrates using magnetron sputtering techniques. These thin films are measured in-situ and in real time as well as ex-situ by spectroscopic ellipsometry in order to extract parameters related to the structural properties, such as bulk layer thickness and surface roughness layer thickness and their time evolution, the latter information specific to real time measurements. The index of refraction and extinction coefficient or complex dielectric function of a single unknown layer can also be obtained from the measurement versus photon energy. Applying analytical expressions for these optical properties versus photon energy, parameters that describe electronic transport, such as electrical resistivity and electron scattering time, can be extracted. The SE technique is also performed as the sample is heated in order to derive the effects of annealing on the optical properties and derived electrical transport parameters, as well as the intrinsic temperature dependence of these properties and parameters. One of the major achievements of this dissertation research is the characterization of the thickness and optical properties of the interface layer formed between the silver and zinc oxide layers in a back-reflector structure used in thin film photovoltaics. An understanding of the impact of these thin film material properties on solar cell device performance has been complemented by applying reflectance and transmittance spectroscopy as well as simulations of cell performance.

Finite-element modelling of multilayer X-ray optics.

PubMed

Cheng, Xianchao; Zhang, Lin

2017-05-01

Multilayer optical elements for hard X-rays are an attractive alternative to crystals whenever high photon flux and moderate energy resolution are required. Prediction of the temperature, strain and stress distribution in the multilayer optics is essential in designing the cooling scheme and optimizing geometrical parameters for multilayer optics. The finite-element analysis (FEA) model of the multilayer optics is a well established tool for doing so. Multilayers used in X-ray optics typically consist of hundreds of periods of two types of materials. The thickness of one period is a few nanometers. Most multilayers are coated on silicon substrates of typical size 60 mm × 60 mm × 100-300 mm. The high aspect ratio between the size of the optics and the thickness of the multilayer (10 7 ) can lead to a huge number of elements for the finite-element model. For instance, meshing by the size of the layers will require more than 10 16 elements, which is an impossible task for present-day computers. Conversely, meshing by the size of the substrate will produce a too high element shape ratio (element geometry width/height > 10 6 ), which causes low solution accuracy; and the number of elements is still very large (10 6 ). In this work, by use of ANSYS layer-functioned elements, a thermal-structural FEA model has been implemented for multilayer X-ray optics. The possible number of layers that can be computed by presently available computers is increased considerably.

Finite-element modelling of multilayer X-ray optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Xianchao; Zhang, Lin

Multilayer optical elements for hard X-rays are an attractive alternative to crystals whenever high photon flux and moderate energy resolution are required. Prediction of the temperature, strain and stress distribution in the multilayer optics is essential in designing the cooling scheme and optimizing geometrical parameters for multilayer optics. The finite-element analysis (FEA) model of the multilayer optics is a well established tool for doing so. Multilayers used in X-ray optics typically consist of hundreds of periods of two types of materials. The thickness of one period is a few nanometers. Most multilayers are coated on silicon substrates of typical sizemore » 60 mm × 60 mm × 100–300 mm. The high aspect ratio between the size of the optics and the thickness of the multilayer (10 7) can lead to a huge number of elements for the finite-element model. For instance, meshing by the size of the layers will require more than 10 16elements, which is an impossible task for present-day computers. Conversely, meshing by the size of the substrate will produce a too high element shape ratio (element geometry width/height > 10 6), which causes low solution accuracy; and the number of elements is still very large (10 6). In this work, by use of ANSYS layer-functioned elements, a thermal-structural FEA model has been implemented for multilayer X-ray optics. The possible number of layers that can be computed by presently available computers is increased considerably.« less

Features of tropospheric and stratospheric dust.

PubMed

Elterman, L; Wexler, R; Chang, D T

1969-05-01

A series of 119 profiles obtained over New Mexico comprise aerosol attenuation coefficients vs altitude to about 35 km. These profiles show the existence of several features. A surface convective dust layer extending up to about 5 km is seasonally dependent. Also, a turbidity maximum exists below the tropopause. The altitude of an aerosol maximum in the lower stratosphere is located just below that of the minimum temperature. The colder the minimum temperature, the greater is the aerosol content of the layer. This relationship suggests that the 20-km dust layer is due to convection in tropical air and advection to higher latitudes. Computed averages of optical thickness show that abatement of stratospheric dust from the Mt. Agung eruption became evident in April 1964. Results based on seventy-nine profiles characterizing volcanic dust abatement indicate that above 26 km, the aerosol scale height averages 3.75 km. Extrapolating with this scale height, tabulations are developed for uv, visible, and ir attenuation to 50 km. Optical mixing ratios are used to examine the aerosol concentrations at various altitudes, including a layer at 26 km having an optical thickness 10(-3) for 0.55-micro wavelength.

Evaluation of inner retinal layers as biomarkers in mild cognitive impairment to moderate Alzheimer’s disease

PubMed Central

Mukherjee, Dibyendu; Stinnett, Sandra S.; Cousins, Scott W.; Potter, Guy G.; Burke, James R.; Farsiu, Sina; Whitson, Heather E.

2018-01-01

Inner retina in Alzheimer's Disease (AD) may experience neuroinflammation resulting in atrophy. The objective of our study was to determine whether retinal GCIPL (ganglion cell-inner plexiform layer) or nerve fiber layer (NFL) thickness may serve as noninvasive biomarkers to diagnose AD. This cross-sectional case-control study enrolled 15 mild cognitive impairment (MCI) patients, 15 mild-moderate AD patients, and 18 cognitively normal adults. NFL and GCIPL thicknesses on optical coherence tomography (OCT) were measured using Duke Optical Coherence Tomography Retinal Analysis Program (DOCTRAP) and Spectralis software. We demonstrated that regional thicknesses of NFL or GCIPL on macular or nerve OCTs did not differ between groups. However, a multi-variate regression analysis identified macular areas with a significant thickening or thinning in NFL and GCIPL in MCI and AD patients. Our primary findings controvert previous reports of thinner NFL in moderate-to-severe AD. The areas of thickening of GCIPL and NFL in the macula adjacent to areas of thinning, as revealed by a more complex statistical model, suggest that NFL and GCIPL may undergo dynamic changes during AD progression. PMID:29420642

Performance Dependences of Multiplication Layer Thickness for InP/InGaAs Avalanche Photodiodes Based on Time Domain Modeling

NASA Technical Reports Server (NTRS)

Xiao, Yegao; Bhat, Ishwara; Abedin, M. Nurul

2005-01-01

InP/InGaAs avalanche photodiodes (APDs) are being widely utilized in optical receivers for modern long haul and high bit-rate optical fiber communication systems. The separate absorption, grading, charge, and multiplication (SAGCM) structure is an important design consideration for APDs with high performance characteristics. Time domain modeling techniques have been previously developed to provide better understanding and optimize design issues by saving time and cost for the APD research and development. In this work, performance dependences on multiplication layer thickness have been investigated by time domain modeling. These performance characteristics include breakdown field and breakdown voltage, multiplication gain, excess noise factor, frequency response and bandwidth etc. The simulations are performed versus various multiplication layer thicknesses with certain fixed values for the areal charge sheet density whereas the values for the other structure and material parameters are kept unchanged. The frequency response is obtained from the impulse response by fast Fourier transformation. The modeling results are presented and discussed, and design considerations, especially for high speed operation at 10 Gbit/s, are further analyzed.

Thickness and composition of ultrathin SiO2 layers on Si

NASA Astrophysics Data System (ADS)

van der Marel, C.; Verheijen, M. A.; Tamminga, Y.; Pijnenburg, R. H. W.; Tombros, N.; Cubaynes, F.

2004-07-01

Ultrathin SiO2 layers are of importance for the semiconductor industry. One of the techniques that can be used to determine the chemical composition and thickness of this type of layers is x-ray photoelectron spectroscopy (XPS). As shown by Seah and Spencer [Surf. Interface Anal. 33, 640 (2002)], it is not trivial to characterize this type of layer by means of XPS in a reliable way. We have investigated a series of ultrathin layers of SiO2 on Si (in the range from 0.3 to 3 nm) using XPS. The samples were also analyzed by means of transmission electron microscopy (TEM), Rutherford backscattering (RBS), and ellipsometry. The thickness of the SiO2 layers (d) was determined from the XPS results using three different approaches: the ``standard'' equation (Seah and Spencer) for d, an overlayer-substrate model calculation, and the QUASES-Tougaard [Surf. Interface Anal. 26, 249 (1998), QUASES-Tougaard: Software package for Quantitative Analysis of Surfaces by Electron Spectroscopy, version 4.4 (2000); http://www.quases.com] method. Good agreement was obtained between the results of XPS analyses using the ``standard'' equation, the overlayer-substrate model calculation, and RBS results. The QUASES-Tougaard results were approximately 62% above the other XPS results. The optical values for the thickness were always slightly higher than the thickness according to XPS or RBS. Using the model calculation, these (relatively small) deviations from the optical results could be explained as being a consequence of surface contaminations with hydrocarbons. For a thickness above 2.5 nm, the TEM results were in good agreement with the results obtained from the other techniques (apart from QUASES-Tougaard). Below 2.5 nm, significant deviations were found between RBS, XPS, and optical data on the one hand and TEM results on the other hand; the deviations became larger as the thickness of the SiO2 decreased. This effect may be related to interface states of oxygen, which have been investigated [D. A. Muller, T. Sorsch, S. Moccio, F. H. Baumann, K. Evans-Lutterodt, and G. Timp, Nature (London) 399, 758 (1999); D. A. Muller and J. B. Neaton, Structure and Energetics of the Interface Between Si and Amorphous SiO2 in Fundamental Aspects of Silicon Oxidation, edited by Y. J. Chabal (Springer, Berlin, 2001), pp. 219-246.] by means of high-resolution electron energy loss spectroscopy measurements of the O K edge in ultrathin gate oxides of SiO2. .

Evaluation of fouling in nanofiltration for desalination using a resistance-in-series model and optical coherence tomography.

PubMed

Park, Jongkwan; Lee, Sungyun; You, Jeongyeop; Park, Sanghun; Ahn, Yujin; Jung, Woonggyu; Cho, Kyung Hwa

2018-06-12

Resistance-in-series models have been applied to investigate fouling behavior. However, it is difficult to model the influence of morphology on fouling behavior because resistance is indirectly calculated from the water flux and transmembrane pressure. In this study, optical coherence tomography (OCT) was applied to evaluate the resistance of the fouling layer based on fouling morphology. Sodium alginate, humic acid, and bovine serum albumin (BSA) with high salts concentrations (conductivity: 23 mS/cm) were used as model foulants. At the same total fouling resistance, BSA showed the highest cake layer thickness (BSA (114.5 μm) > humic acid (53.5 μm) > sodium alginate (20.0 μm)). However, a different order was found for the cake layer resistance (BSA > sodium alginate > humic acid). This indicates that fouling thickness is not correlated with cake layer resistance. According to the Carman-Kozeny equation, fouling layer porosity decreased in the following order: humic acid (0.30) > BSA (0.21) > sodium alginate (0.20). In addition, we provided a specific value that was calculated using the ratio between the fouling thickness and cake layer resistance. The results show that alginic acid induced a stronger cake layer resistance, despite its thin fouling layer, whereas BSA showed a relatively low potential for inducing cake layer resistance. The results obtained in this study could be used for estimating and predicting fouling behavior. Copyright © 2018 Elsevier B.V. All rights reserved.

Optical Coherence Tomography as a Biomarker for Diagnosis, Progression, and Prognosis of Neurodegenerative Diseases

PubMed Central

Otin, Sofia; Fuertes, Maria I.; Vilades, Elisa; Gracia, Hector; Ara, Jose R.; Alarcia, Raquel; Polo, Vicente; Larrosa, Jose M.; Pablo, Luis E.

2016-01-01

Neurodegenerative diseases present a current challenge for accurate diagnosis and for providing precise prognostic information. Developing imaging biomarkers for multiple sclerosis (MS), Parkinson disease (PD), and Alzheimer's disease (AD) will improve the clinical management of these patients and may be useful for monitoring treatment effectiveness. Recent research using optical coherence tomography (OCT) has demonstrated that parameters provided by this technology may be used as potential biomarkers for MS, PD, and AD. Retinal thinning has been observed in these patients and new segmentation software for the analysis of the different retinal layers may provide accurate information on disease progression and prognosis. In this review we analyze the application of retinal evaluation using OCT technology to provide better understanding of the possible role of the retinal layers thickness as biomarker for the detection of these neurodegenerative pathologies. Current OCT analysis of the retinal nerve fiber layer and, specially, the ganglion cell layer thickness may be considered as a good biomarker for disease diagnosis, severity, and progression. PMID:27840739

Generation of individually modulated femtosecond pulse string by multilayer volume holographic gratings.

PubMed

Yan, Xiaona; Gao, Lirun; Yang, Xihua; Dai, Ye; Chen, Yuanyuan; Ma, Guohong

2014-10-20

A scheme to generate individually modulated femtosecond pulse string by multilayer volume holographic grating (MVHG) is proposed. Based on Kogelnik's coupled-wave theory and matrix optics, temporal and spectral expressions of diffracted field are given when a femtosecond pulse is diffracted by a MVHG. It is shown that the number of diffracted sub-pulses in the pulse string equals to the number of grating layers of the MVHG, peak intensity and duration of each diffracted sub-pulse depend on thickness of the corresponding grating layer, whereas pulse interval between adjacent sub-pulses is related to thickness of the corresponding buffer layer. Thus by modulating parameters of the MVHG, individually modulated femtosecond pulse string can be acquired. Based on Bragg selectivity of the volume grating and phase shift provided by the buffer layers, we give an explanation on these phenomena. The result is useful to design MVHG-based devices employed in optical communications, pulse shaping and processing.

Correlation of outer nuclear layer thickness with cone density values in patients with retinitis pigmentosa and healthy subjects.

PubMed

Menghini, Moreno; Lujan, Brandon J; Zayit-Soudry, Shiri; Syed, Reema; Porco, Travis C; Bayabo, Kristine; Carroll, Joseph; Roorda, Austin; Duncan, Jacque L

2014-12-16

We studied the correlation between outer nuclear layer (ONL) thickness and cone density in normal eyes and eyes with retinitis pigmentosa (RP). Spectral-domain optical coherence tomography (SD-OCT) scans were acquired using a displaced pupil entry position of the scanning beam to distinguish Henle's fiber layer from the ONL in 20 normal eyes (10 subjects) and 12 eyes with RP (7 patients). Cone photoreceptors were imaged using adaptive optics scanning laser ophthalmoscopy. The ONL thickness and cone density were measured at 0.5° intervals along the horizontal meridian through the fovea nasally and temporally. The ONL thickness and cone density were correlated using Spearman's rank correlation coefficient r. Cone densities averaged over the central 6° were lower in eyes with RP than normal, but showed high variability in both groups. The ONL thickness and cone density were significantly correlated when all retinal eccentricities were combined (r = 0.74); the correlation for regions within 0.5° to 1.5° eccentricity was stronger (r = 0.67) than between 1.5° and 3.0° eccentricity (r = 0.23). Although cone densities were lower between 0.5° and 1.5° in eyes with RP, ONL thickness measures at identical retinal locations were similar in the two groups (P = 0.31), and interindividual variation was high for ONL and cone density measures. Although ONL thickness and retinal eccentricity were important predictors of cone density, eccentricity was over 3 times more important. The ONL thickness and cone density were correlated in normal eyes and eyes with RP, but both were strongly correlated with retinal eccentricity, precluding estimation of cone density from ONL thickness. (ClinicalTrials.gov number, NCT00254605.). Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.

Correlation of Outer Nuclear Layer Thickness With Cone Density Values in Patients With Retinitis Pigmentosa and Healthy Subjects

PubMed Central

Menghini, Moreno; Lujan, Brandon J.; Zayit-Soudry, Shiri; Syed, Reema; Porco, Travis C.; Bayabo, Kristine; Carroll, Joseph; Roorda, Austin; Duncan, Jacque L.

2015-01-01

Purpose. We studied the correlation between outer nuclear layer (ONL) thickness and cone density in normal eyes and eyes with retinitis pigmentosa (RP). Methods. Spectral-domain optical coherence tomography (SD-OCT) scans were acquired using a displaced pupil entry position of the scanning beam to distinguish Henle's fiber layer from the ONL in 20 normal eyes (10 subjects) and 12 eyes with RP (7 patients). Cone photoreceptors were imaged using adaptive optics scanning laser ophthalmoscopy. The ONL thickness and cone density were measured at 0.5° intervals along the horizontal meridian through the fovea nasally and temporally. The ONL thickness and cone density were correlated using Spearman's rank correlation coefficient r. Results. Cone densities averaged over the central 6° were lower in eyes with RP than normal, but showed high variability in both groups. The ONL thickness and cone density were significantly correlated when all retinal eccentricities were combined (r = 0.74); the correlation for regions within 0.5° to 1.5° eccentricity was stronger (r = 0.67) than between 1.5° and 3.0° eccentricity (r = 0.23). Although cone densities were lower between 0.5° and 1.5° in eyes with RP, ONL thickness measures at identical retinal locations were similar in the two groups (P = 0.31), and interindividual variation was high for ONL and cone density measures. Although ONL thickness and retinal eccentricity were important predictors of cone density, eccentricity was over 3 times more important. Conclusions. The ONL thickness and cone density were correlated in normal eyes and eyes with RP, but both were strongly correlated with retinal eccentricity, precluding estimation of cone density from ONL thickness. (ClinicalTrials.gov number, NCT00254605.) PMID:25515570

Foveal fine structure in retinopathy of prematurity: an adaptive optics Fourier domain optical coherence tomography study.

PubMed

Hammer, Daniel X; Iftimia, Nicusor V; Ferguson, R Daniel; Bigelow, Chad E; Ustun, Teoman E; Barnaby, Amber M; Fulton, Anne B

2008-05-01

To describe the fine structure of the fovea in subjects with a history of mild retinopathy of prematurity (ROP) using adaptive optics-Fourier domain optical coherence tomography (AO-FDOCT). High-speed, high-resolution AO-FDOCT videos were recorded in subjects with a history of ROP (n = 5; age range, 14-26 years) and in control subjects (n = 5; age range, 18-25 years). Custom software was used to extract foveal pit depth and volume from three-dimensional (3-D) retinal maps. The thickness of retinal layers as a function of retinal eccentricity was measured manually. The retinal vasculature in the parafoveal region was assessed. The foveal pit was wider and shallower in ROP than in control subjects. Mean pit depth, defined from the base to the level at which the pit reaches a lateral radius of 728 microm, was 121 microm compared with 53 microm. Intact, contiguous inner retinal layers overlay the fovea in ROP subjects but were absent in the control subjects. Mean full retinal thickness at the fovea was greater in the subjects with ROP (279.0 microm vs. 190.2 microm). The photoreceptor layer thickness did not differ between ROP and control subjects. An avascular zone was not identified in the subjects with ROP but was present in all the control subjects. The foveas of subjects with a history of mild ROP have significant structural abnormalities that are probably a consequence of perturbations of neurovascular development.

Effect of the spin-twist structure on the spin-wave dynamics in Fe{sub 55}Pt{sub 45}/Ni{sub 80}Fe{sub 20} exchange coupled bi-layers with varying Ni{sub 80}Fe{sub 20} thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pal, Semanti; Barman, Saswati, E-mail: saswati@bose.res.in; Barman, Anjan, E-mail: abarman@bose.res.in

2014-05-07

We have investigated optically induced ultrafast magnetization dynamics of a series of Fe{sub 55}Pt{sub 45}/Ni{sub 80}Fe{sub 20} exchange spring bi-layers with varying Ni{sub 80}Fe{sub 20} thickness. Rich spin-wave spectra are observed; whose frequency shows a strong dependence on the Ni{sub 80}Fe{sub 20} layer thickness. Micromagnetic simulations based on a simplified magnetic microstructure were able to reproduce the experimental data qualitatively. The spin twist structure introduced in the Ni{sub 80}Fe{sub 20} layer gives rise to new modes in the composite system as opposed to the bare Ni{sub 80}Fe{sub 20} films.

Corneal epithelium, visual acuity, and laser refractive keratectomy

NASA Astrophysics Data System (ADS)

Simon, Gabriel; Parel, Jean-Marie A.; Kervick, Gerard N.; Rol, Pascal O.; Hanna, Khalil; Thompson, Keith P.

1991-06-01

Photorefractive keratectomy (PRK) using an argon fluoride excimer laser for photoablation of the cornea shows potential for the precise correction of refractive errors in patients. Usually, the epithelium is mechanically removed, and Bowman's layer and stromal tissue are photoablated to precomputed depths and shapes that are based on known ablation rates for these tissues. After four day's time, the epithelium has regrown. Assuming the epithelium to be preoperatively uniform in thickness across the central optical zone, and assuming that it regrows to the same thickness, a theoretical precision of +/- 0.05 diopters is achievable with PRK. Keratometric measurements of the epithelium and of Bowman's layer were made at the 2.0 and 3.6 mm optical zones on 10 fresh cadaver eyes (<21 hours postmortem). In the eyes studied, the epithelium thickness was found to vary across the central optical zone, accounting for the measured refractive differences of 0.5 to 1.8 diopters. Bowman's layer was found to be more prolated than the epithelial surface (ratios: 1.005 compared to 1.033). In addition, the surface of Bowman's layer had a larger degree of astigmatism. Other studies have shown that the epithelium regrowth is a function of the newly exposed corneal topography as the wing cells compensate for irregularities in Bowman's surface. As the preoperative topography of the epithelium cannot be used as a reference surface when computing photoablation depth, intraoperative keratometry of Bowman's surface becomes a necessity in PRK.

Influence of electron transport layer thickness on optical properties of organic light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Guohong; Liu, Yong; Li, Baojun

2015-06-07

We investigate experimentally and theoretically the influence of electron transport layer (ETL) thickness on properties of typical N,N′-diphenyl-N,N′-bis(1-naphthyl)-[1,1′-biphthyl]-4,4′-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) heterojunction based organic light-emitting diodes (OLEDs), where the thickness of ETL is varied to adjust the distance between the emitting zone and the metal electrode. The devices showed a maximum current efficiency of 3.8 cd/A when the ETL thickness is around 50 nm corresponding to an emitter-cathode distance of 80 nm, and a second maximum current efficiency of 2.6 cd/A when the ETL thickness is around 210 nm corresponding to an emitter-cathode distance of 240 nm. We adopt a rigorous electromagnetic approach that takesmore » parameters, such as dipole orientation, polarization, light emitting angle, exciton recombination zone, and diffusion length into account to model the optical properties of devices as a function of varying ETL thickness. Our simulation results are accurately consistent with the experimental results with a widely varying thickness of ETL, indicating that the theoretical model may be helpful to design high efficiency OLEDs.« less

Spectral domain polarization-sensitive optical coherence tomography at 850 nm

NASA Astrophysics Data System (ADS)

Cense, Barry; Chen, Teresa C.; Mujat, Mircea; Joo, Chulmin; Akkin, Taner; Park, B. H.; Pierce, Mark C.; Yun, Andy; Bouma, Brett E.; Tearney, Guillermo J.; de Boer, Johannes F.

2005-04-01

Spectral-Domain Polarization-Sensitive Optical Coherence Tomography (SD-PS-OCT) is a technique developed to measure the thickness and birefringence of the nerve fiber layer in vivo as a tool for the early diagnosis of glaucoma. A clinical SD-PS-OCT system was developed and scans were made around the optic nerve head (ONH) using ten concentric circles of increasing diameter. One healthy volunteer was imaged. Retinal nerve fiber layer thickness and birefringence information was extracted from the data. Polarization-sensitive OCT images were acquired at video rate (29 frames per second (fps), 1000 A-lines / frame) and at 7 fps (1000 A-lines / frame). The last setting improved the signal to noise ratio by approximately 6 dB. Birefringence measurements on the healthy volunteer gave similar results as earlier reported values that were obtained with a time-domain setup. The measurement time was reduced from more than a minute to less than a second.

Optical analysis of AlGaInP laser diodes with real refractive index guided self-aligned structure

NASA Astrophysics Data System (ADS)

Xu, Yun; Zhu, Xiaopeng; Ye, Xiaojun; Kang, Xiangning; Cao, Qing; Guo, Liang; Chen, Lianghui

2004-05-01

Optical modes of AlGaInP laser diodes with real refractive index guided self-aligned (RISA) structure were analyzed theoretically on the basis of two-dimension semivectorial finite-difference methods (SV-FDMs) and the computed simulation results were presented. The eigenvalue and eigenfunction of this two-dimension waveguide were obtained and the dependence of the confinement factor and beam divergence angles in the direction of parallel and perpendicular to the pn junction on the structure parameters such as the number of quantum wells, the Al composition of the cladding layers, the ridge width, the waveguide thickness and the residual thickness of the upper P-cladding layer were investigated. The results can provide optimized structure parameters and help us design and fabricate high performance AlGaInP laser diodes with a low beam aspect ratio required for optical storage applications.

Coordinated Airborne, Spaceborne and Ground-based Measurements of Massive Thick Aerosol Layers during the Dry Season in Southern Africa

NASA Technical Reports Server (NTRS)

Schmid, B.; Redemann, J.; Russell, P. B.; Hobbs, P. V.; Hlavka, D. L.; McGill, M. J.; Holben, B. N.; Welton, E. J.; Campbell, J. R.; Torres, O.

2003-01-01

During the dry season airborne campaign of the Southern African Regional Science Initiative (SAFARI 2000), coordinated observations were made of massive thick aerosol layers. These layers were often dominated by aerosols from biomass burning. We report on airborne Sun photometer measurements of aerosol optical depth (lambda = 0.354- 1.557 microns), columnar water vapor, and vertical profiles of aerosol extinction and water vapor density that were obtained aboard the University of Washington's Convair-580 research aircraft. We compare these with ground-based AERONET Sun/sky radiometer results, with ground based lidar data (MPL-Net), and with measurements from a downward pointing lidar aboard the high-flying NASA ER-2 aircraft. Finally, we show comparisons between aerosol optical depths fiom the Sun photometer and those retrieved over land and over water using four spaceborne sensors (TOMS, MODIS, MISR, and ATSR-2).

Deep Retinal Layer Microvasculature Dropout detected by the Optical Coherence Tomography Angiography in Glaucoma

PubMed Central

Suh, Min Hee; Zangwill, Linda M.; Manalastas, Patricia Isabel C.; Belghith, Akram; Yarmohammadi, Adeleh; Medeiros, Felipe A.; Diniz-Filho, Alberto; Saunders, Luke J.; Weinreb, Robert N.

2016-01-01

Purpose To investigate factors associated with dropout of the deep retinal layer microvasculature within the β-zone parapapillary atrophy (βPPA) assessed by optical coherence tomography angiography (OCT-A) in glaucomatous eyes. Design Cross-sectional study. Participants Seventy-one eyes from 71 primary open angle glaucoma (POAG) patients with βPPA enrolled in the Diagnostic Innovations in Glaucoma Study. Methods βPPA deep layer microvasculature dropout was defined as a complete loss of the microvasculature located within deep retinal layer of the βPPA from OCT-A-derived optic nerve head vessel density maps by standardized qualitative assessment. Circumpapillary vessel density (cpVD) within the retinal nerve fiber layer (RNFL) was also calculated using OCT-A. Choroidal thickness and presence of the focal lamina cribrosa (LC) defect were determined using swept-source OCT. Main Outcome Measures Presence of the βPPA deep layer microvasculature dropout. Parameters including age, systolic and diastolic blood pressure, axial length, intraocular pressure, disc hemorrhage, cpVD, visual field (VF) mean deviation (MD), focal LC defect, βPPA area, and choroidal thickness were analyzed. Results βPPA deep layer microvasculature dropout was detected in 37 eyes (52.1%) of eyes with POAG. Eyes with dropouts had a higher prevalence of LC defect (70.3 vs. 32.4%), lower cpVD (52.7 vs. 58.8%), worse VF MD (-9.06 vs. -3.83dB), thinner total choroidal thickness (126.5 vs. 169.1/μm), longer axial length (24.7 vs. 24.0mm), larger βPPA (1.2 vs. 0.76mm2) and lower diastolic blood pressure (74.7 vs. 81.7mmHg) than those without dropouts (P< 0.05, respectively). In the multivariate logistic regression, higher prevalence of focal LC defect (odds ratio [OR], 6.27; P = 0.012), reduced cpVD (OR, 1.27; P = 0.002), worse VF MD (OR, 1.27; P = 0.001), thinner choroidal thickness (OR, 1.02; P = 0.014), and lower diastolic blood pressure (OR, 1.16; P = 0.003) were significantly associated with the dropout. Conclusions Certain systemic and ocular factors such as focal LC defect, more advanced disease status, reduced RNFL vessel density, thinner choroidal thickness, and lower diastolic blood pressure were factors associated with the βPPA deep layer microvasculature dropout in glaucomatous eyes. Longitudinal studies are required to elucidate the temporal relationship between βPPA deep layer dropout and these factors. PMID:27769587

Characterization of SiGe/Ge heterostructures and graded layers using variable angle spectroscopic ellipsometry

NASA Technical Reports Server (NTRS)

Croke, E. T.; Wang, K. L.; Heyd, A. R.; Alterovitz, S. A.; Lee, C. H.

1996-01-01

Variable angle spectroscopic ellipsometry (VASE) has been used to characterize Si(x)Ge(1-x)/Ge superlattices (SLs) grown on Ge substrates and thick Si(x)Ge(1-x)/Ge heterostructures grown on Si substrates. Our VASE analysis yielded the thicknesses and alloy compositions of all layers within the optical penetration depth of the surface. In addition, strain effects were observed in the VASE results for layers under both compressive and tensile strain. Results for the SL structures were found to be in close agreement with high resolution x-ray diffraction measurements made on the same samples. The VASE analysis has been upgraded to characterize linearly graded Si(x)Ge(1-x) buffer layers. The algorithm has been used to determine the total thickness of the buffer layer along with the start and end alloy composition by breaking the total thickness into many (typically more than 20) equal layers. Our ellipsometric results for 1 (mu)m buffer layers graded in the ranges 0.7 less than or = x less than or = 1.0, and 0.5 less than or = x less than or = 1.0 are presented, and compare favorably with the nominal values.

Macular retinal and choroidal thickness in unilateral amblyopia using swept-source optical coherence tomography.

PubMed

Araki, Syunsuke; Miki, Atsushi; Goto, Katsutoshi; Yamashita, Tsutomu; Takizawa, Go; Haruishi, Kazuko; Ieki, Yoshiaki; Kiryu, Junichi; Yaoeda, Kiyoshi

2017-09-15

To investigate macular retinal and choroidal thickness in amblyopic eyes compared to that in fellow and normal eyes using swept-source optical coherence tomography (SS-OCT). This study examined 31 patients with hyperopic anisometropic amblyopia (6.9 ± 3.8 years, mean ± standard deviation), 15 patients with strabismic amblyopia without anisometropia (7.9 ± 4.2 years), and 24 age-matched controls (7.8 ± 3.3 years). Retinal and choroidal thickness was measured by 3D scans using SS-OCT. A 6-mm area around the fovea was automatically analyzed using the Early Treatment Diabetic Retinopathy Study map. The thickness from SS-OCT was corrected for magnification error using individual axial length, spherical refraction, cylinder refraction, and corneal radius. Retinal thickness was divided into the macular retinal nerve fiber layer (mRNFL), ganglion cell layer + inner plexiform layer (GCL+IPL), ganglion cell complex (GCC), and the inner limiting membrane to the retinal pigment epithelium (ILM-RPE) thickness. Retinal and choroidal thickness was compared among amblyopic, fellow, and normal eyes. In both amblyopia groups, there was no significant difference in the mRNFL, GCL+IPL, and GCC thicknesses among the amblyopic, fellow, and control eyes. In the anisometropic amblyopia group, choroidal thickness (subfovea, center 1 mm, nasal and inferior of the inner ring, nasal of the outer ring, and center 6 mm) of amblyopic eyes were significantly greater than that of fellow and normal eyes. In contrast, none of the choroidal thicknesses were significantly different among the investigated eyes in the strabismic amblyopia group. We found no significant difference in inner retinal thickness in patients with unilateral amblyopia. Although there were significant differences in choroidal thickness with hyperopic anisometropic amblyopia, there was no significant difference for the strabismic amblyopia. The discrepancy in choroidal thickness between the two types of amblyopia may be due to both differences in ocular size and underlying mechanism.

Baseline OCT Measurements in the Idiopathic Intracranial Hypertension Treatment Trial, Part I: Quality Control, Comparisons, and Variability

PubMed Central

2014-01-01

Purpose. Optical coherence tomography (OCT) has been used to investigate papilledema in single-site, mostly retrospective studies. We investigated whether spectral-domain OCT (SD-OCT), which provides thickness and volume measurements of the optic nerve head and retina, could reliably demonstrate structural changes due to papilledema in a prospective multisite clinical trial setting. Methods. At entry, 126 subjects in the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) with mild visual field loss had optic disc and macular scans, using the Cirrus SD-OCT. Images were analyzed by using the proprietary commercial and custom 3D-segmentation algorithms to calculate retinal nerve fiber layer (RNFL), total retinal thickness (TRT), optic nerve head volume (ONHV), and retinal ganglion cell layer (GCL) thickness. We evaluated variability, with interocular comparison and correlation between results for both methods. Results. The average RNFL thickness > 95% of normal controls in 90% of eyes and the RNFL, TRT, ONH height, and ONHV showed strong (r > 0.8) correlations for interocular comparisons. Variability for repeated testing of OCT parameters was low for both methods and intraclass correlations > 0.9 except for the proprietary GCL thickness. The proprietary algorithm–derived RNFL, TRT, and GCL thickness measurements had failure rates of 10%, 16%, and 20% for all eyes respectively, which were uncommon with 3D-segmentation–derived measurements. Only 7% of eyes had GCL thinning that was less than fifth percentile of normal age-matched control eyes by both methods. Conclusions. Spectral-domain OCT provides reliable continuous variables and quantified assessment of structural alterations due to papilledema. (ClinicalTrials.gov number, NCT01003639.) PMID:25370510

The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography.

PubMed

Liu, Lin; Zou, Jun; Huang, Hui; Yang, Jian-guo; Chen, Shao-rong

2012-05-23

To evaluate the influence of corneal astigmatism (CA) on retinal nerve fiber layer (RNFL) thickness and optic nerve head(ONH) parameters measured with spectral-domain optical coherence tomography (OCT) in high myopes patients before refractive surgery. Seventy eyes of 35 consecutive refractive surgery candidates were included in this study. The mean age of the subjects was 26.42 ± 6.95 years, the average CA was -1.17 diopters (D; SD 0.64; range -0.2 to-3.3D), All subjects in this study were WTR CA. 34 eyes were in the normal CA group with a mean CA was -0.67 ± 0.28D, 36 eyes were in the high CA group with an average CA of -1.65 ± 0.49D. All subjects underwent ophthalmic examination and imaging with the Cirrus HD OCT. No significant difference was noted in the average cup-to-disk ratio, vertical cup-to-disk ratio and cup volume (all P values > 0.05). Compared with the normal CA group, the high CA group had a larger disc area and rim area, thinner RNFL thickness in the temporal quadrant, and the superotemporal and inferotemporal peaks were farther to the temporal horizon (All P values < 0.05). There were no significant differences between the two groups in global average RNFL thickness, as well as superior, nasal and inferior quadrant RNFL thickness (all P values > 0.05). The degree of with-the-rule CA should be considered when interpreting ONH parameters and peripapillary RNFL thickness measured by the Cirrus HD OCT. The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1148475676881895.

Process for growing a film epitaxially upon a MgO surface

DOEpatents

McKee, Rodney Allen; Walker, Frederick Joseph

1997-01-01

A process and structure wherein optical quality perovskites, such as BaTiO.sub.3 or SrTiO.sub.3, are grown upon a single crystal MgO substrate involves the epitaxial build up of alternating planes of TiO.sub.2 and metal oxide wherein the first plane grown upon the MgO substrate is a plane of TiO.sub.2. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

Optical properties of composite restorations influenced by dissimilar dentin restoratives.

PubMed

Marjanovic, Jovana; Veljovic, Djordje N; Stasic, Jovana N; Savic-Stankovic, Tatjana; Trifkovic, Branka; Miletic, Vesna

2018-05-01

To evaluate optical properties (color and translucency) of 'sandwich' restorations of resin-based composites and esthetically unfavorable dentin restoratives. Cylindrical 'dentin' specimens (8mm in diameter and 2mm thick, N=5/group) were prepared using EverX Posterior (GC), Biodentine (Septodont), experimental hydroxyapatite (HAP) or conventional composites (Gradia Direct Posterior, GC; Filtek Z250 and Filtek Z500, 3M ESPE). Capping 'enamel' layers were prepared using composites (Gradia Direct Posterior, Filtek Z250 or Z550) of A1 or A3 shade and the following thickness: 0.6, 1 or 2mm. Color (ΔE) and translucency parameter (TP) were determined using a spectrophotometer (VITA Easyshade Advance 4.0, VITA Zahnfabrik). Data were statistically analyzed using analysis of variance with Tukey's post-hoc tests (α=0.05). TP was greatly affected by layer thickness, whilst ΔE depended on shade and layer thickness of the capping composite. HAP and Biodentine showed significantly lower TP and higher ΔE (deviation from 'ideal white') than composites (p<0.05). Greater TP was seen in EverX_composite groups than in corresponding control groups of the same shade and thickness. TP of composites combined with Biodentine or HAP was below 2, lower than the corresponding control groups (p<0.05). Within-group differences of ΔE were greatest in HAP_composite groups. EverX_Gradia and EverX_FiltekZ250 combinations showed the most comparable ΔE with the control groups. A 2mm thick layer of composite covering dentin restoratives with unfavorable esthetics is recommended for a final 'sandwich' restoration that is esthetically comparable to a conventional, mono-composite control restoration. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Optically transduced MEMS gyro device

DOEpatents

Nielson, Gregory N; Bogart, Gregory R; Langlois, Eric; Okandan, Murat

2014-05-20

A bulk micromachined vibratory gyro in which a proof mass has a bulk substrate thickness for a large mass and high inertial sensitivity. In embodiments, optical displacement transduction is with multi-layer sub-wavelength gratings for high sensitivity and low cross-talk with non-optical drive elements. In embodiments, the vibratory gyro includes a plurality of multi-layer sub-wavelength gratings and a plurality of drive electrodes to measure motion of the proof mass induced by drive forces and/or moments and induced by the Coriolis Effect when the gyro experiences a rotation. In embodiments, phase is varied across the plurality gratings and a multi-layer grating having the best performance is selected from the plurality.

Photonic band gaps from a stack of right- and left-hand chiral photonic crystal layers.

PubMed

Gevorgyan, A H

2012-02-01

In the present paper we investigated the optical properties of a stack of right- and left- hand chiral photonic crystal layers. The problem is solved by Ambartsumian's layer addition modified method. We investigated the reflection spectra peculiarities of this system and showed that in contrast to a single cholesteric liquid crystal (CLC) layer this system has multiple photonic band gaps (PBGs) (at light normal incidence). We showed that this system has unique polarization properties, particularly the eigenpolarizations (EPs) of the system are degenerated (i.e., the two EPs coincide) for an even number of layers and, in contrast to ordinary gyrotropic systems, the polarization plane rotation decreases if the system thickness is increased, the rotation sign depends on the first sublayer chirality sign, the system is very sensitive to the change of the sublayer number in the system, etc. We also investigated the influence of sublayer thicknesses, incidence angle, the sublayer local dielectric anisotropies, the sublayer helix pitches on the reflection peculiarities, and other optical parameters of the system. © 2012 American Physical Society

Optical absorption characteristics in the assessment of powder phosphor-based x-ray detectors: from nano- to micro-scale.

PubMed

Liaparinos, P F

2015-11-21

X-ray phosphor-based detectors have enormously improved the quality of medical imaging examinations through the optimization of optical diffusion. In recent years, with the development of science and technology in the field of materials, improved powder phosphors require structural and optical properties that contribute to better optical signal propagation. The purpose of this paper was to provide a quantitative and qualitative understanding of the optical absorption characteristics in the assessment of powder phosphor-based detectors (from nano- scale up to micro-scale). Variations on the optical absorption parameters (i.e. the light extinction coefficient [Formula: see text] and the percentage probability of light absorption p%) were evaluated based on Mie calculations examining a wide range of light wavelengths, particle refractive indices and sizes. To model and assess the effects of the aforementioned parameters on optical diffusion, Monte Carlo simulation techniques were employed considering: (i) phosphors of different layer thickness, 100 μm (thin layer) and 300 μm (thick layer), respectively, (ii) light extinction coefficient values, 1, 3 and 6 μm(-1), and (iii) percentage probability of light absorption p% in the range 10(-4)-10(-2). Results showed that the [Formula: see text] coefficient is high for phosphor grains in the submicron scale and for low light wavelengths. At higher wavelengths (above 650 nm), optical quanta follow approximately similar depths until interaction for grain diameter 500 nm and 1 μm. Regarding the variability of the refractive index, high variations of the [Formula: see text] coefficient occurred above 1.6. Furthermore, results derived from Monte Carlo modeling showed that high spatial resolution phosphors can be accomplished by increasing the [Formula: see text] parameter. More specifically, the FWHM was found to decrease (i.e. higher resolution): (i) 4.8% at 100 μm and (ii) 9.5%, at 300 μm layer thickness. This study attempted to examine the role of the optical absorption parameters on optical diffusion studies. A significant outcome of the present investigation was that the improvement of phosphor spatial resolution without decreasing the light collection efficiency too much can be better achieved by increasing the parameter [Formula: see text] rather than the parameter p%.

Microstructure and opto-electronic properties of Sn-rich Au-Sn diffusive solders

NASA Astrophysics Data System (ADS)

Rerek, T.; Skowronski, L.; Kobierski, M.; Naparty, M. K.; Derkowska-Zielinska, B.

2018-09-01

Microstructural and opto-electronic properties of Au ⧹ Sn and Sn ⧹ Au bilayers, obtained by sequential evaporating of metals on the Si substrate, were investigated by means of atomic force microscopy, X-ray diffraction and spectroscopic ellipsometry. Thicknesses of individual films were established to obtain the atomic ratio of Au:Sn atoms 1:1, 1:2 and 1:4, which were favor the formation of AuSn, AuSn2 and AuSn4, respectively. However, the produced intermatallic compounds were detected as AuSn and AuSn2. Additionally, the unbounded Sn was found. The sequence of deposition of Au and Sn films as well as their thickness strongly affect on the composition, microstructure, optical and electrical properties of the produced layers. The Au ⧹ Sn (Sn on the top) layers were more smooth than Sn ⧹ Au (Au on the top) films. Generally, the Au ⧹ Sn layers exhibit a better electrical and optical properties than Sn ⧹ Au films. The optical parameters: plasma energy, free-carrier damping, mean relaxation time of conduction electrons and optical resistivity were determined from the effective complex dielectric function of the formed Au, Sn and Au-Sn films. The optical resistivity values are in the range from 17.8 μΩ cm to 85.1 μΩ cm and from 29.6 μΩ cm to 113.3 μΩ cm for Au ⧹ Sn and Sn ⧹ Au layers, respectively.

4P-NPD ultra-thin films as efficient exciton blocking layers in DBP/C70 based organic solar cells

NASA Astrophysics Data System (ADS)

Patil, Bhushan R.; Liu, Yiming; Qamar, Talha; Rubahn, Horst-Günter; Madsen, Morten

2017-09-01

Exciton blocking effects from ultra-thin layers of N,N‧-di-1-naphthalenyl-N,N‧-diphenyl [1,1‧:4‧,1″:4″,1‴-quaterphenyl]-4,4‴-diamine (4P-NPD) were investigated in small molecule-based inverted organic solar cells (OSCs) using tetraphenyldibenzoperiflanthene as the electron donor material and fullerene (C70) as the electron acceptor material. The short-circuit current density (J SC) and power conversion efficiency (PCE) of the optimized OSCs with 0.7 nm thick 4P-NPD were approximately 16% and 24% higher, respectively, compared to reference devices without exciton blocking layers (EBLs). Drift diffusion-based device modeling was conducted to model the full current density-voltage (JV) characteristics and external quantum efficiency spectrum of the OSCs, and photoluminescence measurements were conducted to investigate the exciton blocking effects with increasing thicknesses of the 4P-NPD layer. Importantly, coupled optical and electrical modeling studies of the device behaviors and exciton generation rates and densities in the active layer for different 4P-NPD layer thicknesses were conducted, in order to gain a complete understanding of the observed increase in PCE for 4P-NPD layer thicknesses up to 1 nm, and the observed decrease in PCE for layer thicknesses beyond 1 nm. This work demonstrates a route for guiding the integration of EBLs in OSC devices.

Photoacoustic signal attenuation analysis for the assessment of thin layers thickness in paintings

NASA Astrophysics Data System (ADS)

Tserevelakis, George J.; Dal Fovo, Alice; Melessanaki, Krystalia; Fontana, Raffaella; Zacharakis, Giannis

2018-03-01

This study introduces a novel method for the thickness estimation of thin paint layers in works of art, based on photoacoustic signal attenuation analysis (PAcSAA). Ad hoc designed samples with acrylic paint layers (Primary Red Magenta, Cadmium Yellow, Ultramarine Blue) of various thicknesses on glass substrates were realized for the specific application. After characterization by Optical Coherence Tomography imaging, samples were irradiated at the back side using low energy nanosecond laser pulses of 532 nm wavelength. Photoacoustic waves undergo a frequency-dependent exponential attenuation through the paint layer, before being detected by a broadband ultrasonic transducer. Frequency analysis of the recorded time-domain signals allows for the estimation of the average transmitted frequency function, which shows an exponential decay with the layer thickness. Ultrasonic attenuation models were obtained for each pigment and used to fit the data acquired on an inhomogeneous painted mock-up simulating a real canvas painting. Thickness evaluation through PAcSAA resulted in excellent agreement with cross-section analysis with a conventional brightfield microscope. The results of the current study demonstrate the potential of the proposed PAcSAA method for the non-destructive stratigraphic analysis of painted artworks.

Fast retinal layer segmentation of spectral domain optical coherence tomography images

NASA Astrophysics Data System (ADS)

Zhang, Tianqiao; Song, Zhangjun; Wang, Xiaogang; Zheng, Huimin; Jia, Fucang; Wu, Jianhuang; Li, Guanglin; Hu, Qingmao

2015-09-01

An approach to segment macular layer thicknesses from spectral domain optical coherence tomography has been proposed. The main contribution is to decrease computational costs while maintaining high accuracy via exploring Kalman filtering, customized active contour, and curve smoothing. Validation on 21 normal volumes shows that 8 layer boundaries could be segmented within 5.8 s with an average layer boundary error <2.35 μm. It has been compared with state-of-the-art methods for both normal and age-related macular degeneration cases to yield similar or significantly better accuracy and is 37 times faster. The proposed method could be a potential tool to clinically quantify the retinal layer boundaries.

ITO/Au/ITO sandwich structure for near-infrared plasmonics.

PubMed

Fang, Xu; Mak, Chee Leung; Dai, Jiyan; Li, Kan; Ye, Hui; Leung, Chi Wah

2014-09-24

ITO/Au/ITO trilayers with varying gold spacer layer thicknesses were deposited on glass substrates by pulsed laser deposition. Transmission electron microscopy measurements demonstrated the continuous nature of the Au layer down to 2.4 nm. XRD patterns clearly showed an enhanced crystallinity of the ITO films promoted by the insertion of the gold layer. Compared with a single layer of ITO with a carrier concentration of 7.12 × 10(20) cm(-3), the ITO/Au/ITO structure achieved an effective carrier concentration as high as 3.26 × 10(22) cm(-3). Transmittance and ellipsometry measurements showed that the optical properties of ITO/Au/ITO films were greatly influenced by the thickness of the inserted gold layer. The cross-point wavelength of the trilayer samples was reduced with increasing gold layer thickness. Importantly, the trilayer structure exhibited a reduced loss (compared with plain Au) in the near-infrared region, suggesting its potential for plasmonic applications in the near-infrared range.

Enhanced Visible Transmittance of Thermochromic VO₂ Thin Films by SiO₂ Passivation Layer and Their Optical Characterization.

PubMed

Yu, Jung-Hoon; Nam, Sang-Hun; Lee, Ji Won; Boo, Jin-Hyo

2016-07-09

This paper presents the preparation of high-quality vanadium dioxide (VO₂) thermochromic thin films with enhanced visible transmittance (T vis ) via radio frequency (RF) sputtering and plasma enhanced chemical vapor deposition (PECVD). VO₂ thin films with high T vis and excellent optical switching efficiency (E os ) were successfully prepared by employing SiO₂ as a passivation layer. After SiO₂ deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO₂ coating, the phase transition temperature (T c ) of the prepared films was not affected. Compared with pristine VO₂, the total layer thickness after SiO₂ coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO₂ thin films showed a higher T vis value (λ 650 nm, 58%) compared with the pristine samples (λ 650 nm, 43%). This enhancement of T vis while maintaining high E os is meaningful for VO₂-based smart window applications.

Error Analysis of Indirect Broadband Monitoring of Multilayer Optical Coatings using Computer Simulations

NASA Astrophysics Data System (ADS)

Semenov, Z. V.; Labusov, V. A.

2017-11-01

Results of studying the errors of indirect monitoring by means of computer simulations are reported. The monitoring method is based on measuring spectra of reflection from additional monitoring substrates in a wide spectral range. Special software (Deposition Control Simulator) is developed, which allows one to estimate the influence of the monitoring system parameters (noise of the photodetector array, operating spectral range of the spectrometer and errors of its calibration in terms of wavelengths, drift of the radiation source intensity, and errors in the refractive index of deposited materials) on the random and systematic errors of deposited layer thickness measurements. The direct and inverse problems of multilayer coatings are solved using the OptiReOpt library. Curves of the random and systematic errors of measurements of the deposited layer thickness as functions of the layer thickness are presented for various values of the system parameters. Recommendations are given on using the indirect monitoring method for the purpose of reducing the layer thickness measurement error.

Prevalence of Split Nerve Fiber Layer Bundles in Healthy People Imaged with Spectral Domain Optical Coherence Tomography.

PubMed

Gür Güngör, Sirel; Akman, Ahmet; Sarıgül Sezenöz, Almila; Tanrıaşıkı, Gülşah

2016-12-01

The presence of retinal nerve fiber layer (RNFL) split bundles was recently described in normal eyes scanned using scanning laser polarimetry and by histologic studies. Split bundles may resemble RNFL loss in healthy eyes. The aim of our study was to determine the prevalence of nerve fiber layer split bundles in healthy people. We imaged 718 eyes of 359 healthy persons with the spectral domain optical coherence tomography in this cross-sectional study. All eyes had intraocular pressure of 21 mmHg or less, normal appearance of the optic nerve head, and normal visual fields (Humphrey Field Analyzer 24-2 full threshold program). In our study, a bundle was defined as 'split' when there is localized defect not resembling a wedge defect in the RNFL deviation map with a symmetrically divided RNFL appearance on the RNFL thickness map. The classification was performed by two independent observers who used an identical set of reference examples to standardize the classification. Inter-observer consensus was reached in all cases. Bilateral superior split bundles were seen in 19 cases (5.29%) and unilateral superior split was observed in 15 cases (4.16%). In 325 cases (90.52%) there was no split bundle. Split nerve fiber layer bundles, in contrast to single nerve fiber layer bundles, are not common findings in healthy eyes. In eyes with normal optic disc appearance, especially when a superior RNFL defect is observed in RNFL deviation map, the RNLF thickness map and graphs should also be examined for split nerve fiber layer bundles.

Asymmetry Analysis of Macular Inner Retinal Layers for Glaucoma Diagnosis: Swept-Source Optical Coherence Tomography Study.

PubMed

Lee, Sang-Yoon; Lee, Eun Kyoung; Park, Ki Ho; Kim, Dong Myung; Jeoung, Jin Wook

2016-01-01

To report an asymmetry analysis of macular inner retinal layers using swept-source optical coherence tomography (OCT) and to evaluate the utility for glaucoma diagnosis. Observational, cross-sectional study. Seventy normal healthy subjects and 62 glaucoma patients. Three-dimensional scans were acquired from 70 normal subjects and 62 open angle glaucoma patients by swept-source OCT. The thickness of the retinal nerve fiber layer, ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex, and total retina were calculated within a 6.2×6.2 mm macular area divided into a 31×31 grid of 200×200 μm superpixels. For each of the corresponding superpixels, the thickness differences between the subject eyes and contra-lateral eyes and between the upper and lower macula halves of the subject eyes were determined. The negative differences were displayed on a gray-scale asymmetry map. Black superpixels were defined as thickness decreases over the cut-off values. The negative inter-ocular and inter-hemisphere differences in GCIPL thickness (mean ± standard deviation) were -2.78 ± 0.97 μm and -3.43 ± 0.71 μm in the normal group and -4.26 ± 2.23 μm and -4.88 ± 1.46 μm in the glaucoma group. The overall extent of the four layers' thickness decrease was larger in the glaucoma group than in the normal group (all Ps<0.05). The numbers of black superpixels on all of the asymmetry maps were larger in the glaucoma group than in the normal group (all Ps<0.05). The area under receiver operating characteristic curves of average negative thickness differences in macular inner layers for glaucoma diagnosis ranged from 0.748 to 0.894. The asymmetry analysis of macular inner retinal layers showed significant differences between the normal and glaucoma groups. The diagnostic performance of the asymmetry analysis was comparable to that of previous methods. These findings suggest that the asymmetry analysis can be a potential ancillary diagnostic tool.

Prediction of the limit of detection of an optical resonant reflection biosensor.

PubMed

Hong, Jongcheol; Kim, Kyung-Hyun; Shin, Jae-Heon; Huh, Chul; Sung, Gun Yong

2007-07-09

A prediction of the limit of detection of an optical resonant reflection biosensor is presented. An optical resonant reflection biosensor using a guided-mode resonance filter is one of the most promising label-free optical immunosensors due to a sharp reflectance peak and a high sensitivity to the changes of optical path length. We have simulated this type of biosensor using rigorous coupled wave theory to calculate the limit of detection of the thickness of the target protein layer. Theoretically, our biosensor has an estimated ability to detect thickness change approximately the size of typical antigen proteins. We have also investigated the effects of the absorption and divergence of the incident light on the detection ability of the biosensor.

Interferometric pump-probe characterization of the nonlocal response of optically transparent ion implanted polymers

NASA Astrophysics Data System (ADS)

Stefanov, Ivan L.; Hadjichristov, Georgi B.

2012-03-01

Optical interferometric technique is applied to characterize the nonlocal response of optically transparent ion implanted polymers. The thermal nonlinearity of the ion-modified material in the near-surface region is induced by continuous wave (cw) laser irradiation at a relatively low intensity. The interferometry approach is demonstrated for a subsurface layer of a thickness of about 100 nm formed in bulk polymethylmethacrylate (PMMA) by implantation with silicon ions at an energy of 50 keV and fluence in the range 1014-1017 cm-2. The laser-induced thermooptic effect in this layer is finely probed by interferometric imaging. The interference phase distribution in the plane of the ion implanted layer is indicative for the thermal nonlinearity of the near-surface region of ion implanted optically transparent polymeric materials.

Effects of different wetting layers on the growth of smooth ultra-thin silver thin films

NASA Astrophysics Data System (ADS)

Ni, Chuan; Shah, Piyush; Sarangan, Andrew M.

2014-09-01

Ultrathin silver films (thickness below 10 nm) are of great interest as optical coatings on windows and plasmonic devices. However, producing these films has been a continuing challenge because of their tendency to form clusters or islands rather than smooth contiguous thin films. In this work we have studied the effect of Cu, Ge and ZnS as wetting layers (1.0 nm) to achieve ultrasmooth thin silver films. The silver films (5 nm) were grown by RF sputter deposition on silicon and glass substrates using a few monolayers of the different wetting materials. SEM imaging was used to characterize the surface properties such as island formation and roughness. Also the optical properties were measured to identify the optical impact of the different wetting layers. Finally, a multi-layer silver based structure is designed and fabricated, and its performance is evaluated. The comparison between the samples with different wetting layers show that the designs with wetting layers which have similar optical properties to silver produce the best overall performance. In the absence of a wetting layer, the measured optical spectra show a significant departure from the model predictions, which we attribute primarily to the formation of clusters.

High efficiency, low cost, thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

2001-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

1999-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

Sensitivity control of optical fiber biosensors utilizing turnaround point long period gratings with self-assembled polymer coatings

NASA Astrophysics Data System (ADS)

Gifford, Erika; Wang, Z.; Ramachandran, S.; Heflin, J. R.

2007-09-01

Ionic self-assembled multilayers (ISAMs) adsorbed on long period fiber gratings (LPGs) can serve as an inexpensive, robust, portable, biosensor platform. The ISAM technique is a layer-by-layer deposition technique that creates thin films on the nanoscale level. The combination of ISAMs with LPGs yields exceptional sensitivity of the optical fiber transmission spectrum. We have shown theoretically that the resonant wavelength shift for a thin-film coated LPG can be caused by the variation of the film's refractive index and/or the variation of the thickness of the film. We have experimentally demonstrated that the deposition of nm-thick ISAM films on LPGs induces shifts in the resonant wavelength of > 1.6 nm per nm of thin film. It has also been shown that the sensitivity of the LPG to the thickness of the ISAM film increases with increased film thickness. We have further demonstrated that ISAM-coated LPGs can function effectively as biosensors by using the biotin-streptavidin system and by using the Bacillus anthracis (Anthrax) antibody- PA (Protective Antigen) system. Experiments have been successfully performed in both air and solution, which illustrates the versatility of the biosensor. The results confirm that ISAM-LPGs yield a reusable, thermally-stable, and robust platform for designing and building efficient optical biosensors.

Optical Coherence Tomography Study of Experimental Anterior Ischemic Optic Neuropathy and Histologic Confirmation

PubMed Central

Ho, Joyce K.; Stanford, Madison P.; Shariati, Mohammad A.; Dalal, Roopa; Liao, Yaping Joyce

2013-01-01

Purpose. The optic nerve is part of the central nervous system, and interruption of this pathway due to ischemia typically results in optic atrophy and loss of retinal ganglion cells. In this study, we assessed in vivo retinal changes following murine anterior ischemic optic neuropathy (AION) by using spectral-domain optical coherence tomography (SD-OCT) and compared these anatomic measurements to that of histology. Methods. We induced ischemia at the optic disc via laser-activated photochemical thrombosis, performed serial SD-OCT and manual segmentation of the retinal layers to measure the ganglion cell complex (GCC) and total retinal thickness, and correlated these measurements with that of histology. Results. There was impaired perfusion and leakage at the optic disc on fluorescein angiography immediately after AION and severe swelling and distortion of the peripapillary retina on day-1. We used SD-OCT to quantify the changes in retinal thickness following experimental AION, which revealed significant thickening of the GCC on day-1 after ischemia followed by gradual thinning that plateaued by week-3. Thickness of the peripapillary sensory retina was also increased on day-1 and thinned chronically. This pattern of acute retinal swelling and chronic thinning on SD-OCT correlated well with changes seen in histology and corresponded to loss of retinal ganglion layer cells after ischemia. Conclusions. This was a serial SD-OCT quantification of acute and chronic changes following experimental AION, which revealed changes in the GCC similar to that of human AION, but over a time frame of weeks rather than months. PMID:23887804

Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nandi, R., E-mail: rajunandi@iitb.ac.in; Mohan, S., E-mail: rajunandi@iitb.ac.in; Major, S. S.

2014-04-24

ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology andmore » vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.« less

Photonics of 2D gold nanolayers on sapphire surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Nabatov, B. V.

Gold layers with thicknesses of up to several nanometers, including ordered and disordered 2D nanostructures of gold particles, have been formed on sapphire substrates; their morphology is described; and optical investigations are carried out. The possibility of increasing the accuracy of predicting the optical properties of gold layers and 2D nanostructures using quantum-mechanical models based on functional density theory calculation techniques is considered. The application potential of the obtained materials in photonics is estimated.

Absorptive carbon nanotube electrodes: Consequences of optical interference loss in thin film solar cells

NASA Astrophysics Data System (ADS)

Tait, Jeffrey G.; de Volder, Michaël F. L.; Cheyns, David; Heremans, Paul; Rand, Barry P.

2015-04-01

A current bottleneck in the thin film photovoltaic field is the fabrication of low cost electrodes. We demonstrate ultrasonically spray coated multiwalled carbon nanotube (CNT) layers as opaque and absorptive metal-free electrodes deposited at low temperatures and free of post-deposition treatment. The electrodes show sheet resistance as low as 3.4 Ω □-1, comparable to evaporated metallic contacts deposited in vacuum. Organic photovoltaic devices were optically simulated, showing comparable photocurrent generation between reflective metal and absorptive CNT electrodes for photoactive layer thickness larger than 600 nm when using archetypal poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61-butyric acid methyl ester (PCBM) cells. Fabricated devices clearly show that the absorptive CNT electrodes display comparable performance to solution processed and spray coated Ag nanoparticle devices. Additionally, other candidate absorber materials for thin film photovoltaics were simulated with absorptive contacts, elucidating device design in the absence of optical interference and reflection.A current bottleneck in the thin film photovoltaic field is the fabrication of low cost electrodes. We demonstrate ultrasonically spray coated multiwalled carbon nanotube (CNT) layers as opaque and absorptive metal-free electrodes deposited at low temperatures and free of post-deposition treatment. The electrodes show sheet resistance as low as 3.4 Ω □-1, comparable to evaporated metallic contacts deposited in vacuum. Organic photovoltaic devices were optically simulated, showing comparable photocurrent generation between reflective metal and absorptive CNT electrodes for photoactive layer thickness larger than 600 nm when using archetypal poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61-butyric acid methyl ester (PCBM) cells. Fabricated devices clearly show that the absorptive CNT electrodes display comparable performance to solution processed and spray coated Ag nanoparticle devices. Additionally, other candidate absorber materials for thin film photovoltaics were simulated with absorptive contacts, elucidating device design in the absence of optical interference and reflection. Electronic supplementary information (ESI) available: An animation of the MWCNT spray coating process, and five figures, including: a photograph of completed devices with MWCNT electrodes, performance metrics for devices with photoactive layer thickness up to 3000 nm, contour plots of simulated devices used to build Fig. 5, simulation data for perovskite devices, and a contour plot of the simplified equation of photoactive layer thickness required to attain a specified photocurrent ratio (x-axis) and absorption coefficient (y-axis). See DOI: 10.1039/c5nr01119a

Toward Efficient Thick Active PTB7 Photovoltaic Layers Using Diphenyl Ether as a Solvent Additive.

PubMed

Zheng, Yifan; Goh, Tenghooi; Fan, Pu; Shi, Wei; Yu, Junsheng; Taylor, André D

2016-06-22

The development of thick organic photovoltaics (OPV) could increase absorption in the active layer and ease manufacturing constraints in large-scale solar panel production. However, the efficiencies of most low-bandgap OPVs decrease substantially when the active layers exceed ∼100 nm in thickness (because of low crystallinity and a short exciton diffusion length). Herein, we report the use of solvent additive diphenyl ether (DPE) that facilitates the fabrication of thick (180 nm) active layers and triples the power conversion efficiency (PCE) of conventional thienothiophene-co-benzodithiophene polymer (PTB7)-based OPVs from 1.75 to 6.19%. These results demonstrate a PCE 20% higher than those of conventional (PTB7)-based OPV devices using 1,8-diiodooctane. Morphology studies reveal that DPE promotes the formation of nanofibrillar networks and ordered packing of PTB7 in the active layer that facilitate charge transport over longer distances. We further demonstrate that DPE improves the fill factor and photocurrent collection by enhancing the overall optical absorption, reducing the series resistance, and suppressing bimolecular recombination.

Optical coherence tomography as an accurate inspection and quality evaluation technique in paper industry

NASA Astrophysics Data System (ADS)

Prykäri, Tuukka; Czajkowski, Jakub; Alarousu, Erkki; Myllylä, Risto

2010-05-01

Optical coherence tomography (OCT), a technique for the noninvasive imaging of turbid media, based on low-coherence interferometry, was originally developed for the imaging of biological tissues. Since the development of the technique, most of its applications have been related to the area of biomedicine. However, from early stages, the vertical resolution of the technique has already been improved to a submicron scale. This enables new possibilities and applications. This article presents the possible applications of OCT in paper industry, where submicron or at least a resolution close to one micron is required. This requirement comes from the layered structure of paper products, where layer thickness may vary from single microns to tens of micrometers. This is especially similar to the case with high-quality paper products, where several different coating layers are used to obtain a smooth surface structure and a high gloss. In this study, we demonstrate that optical coherence tomography can be used to measure and evaluate the quality of the coating layer of a premium glossy photopaper. In addition, we show that for some paper products, it is possible to measure across the entire thickness range of a paper sheet. Furthermore, we suggest that in addition to topography and tomography images of objects, it is possible to obtain information similar to gloss by tracking the magnitude of individual interference signals in optical coherence tomography.

Designing optimal nanofocusing with a gradient hyperlens

NASA Astrophysics Data System (ADS)

Shen, Lian; Prokopeva, Ludmila J.; Chen, Hongsheng; Kildishev, Alexander V.

2017-11-01

We report the design of a high-throughput gradient hyperbolic lenslet built with real-life materials and capable of focusing a beam into a deep sub-wavelength spot of λ/23. This efficient design is achieved through high-order transformation optics and circular effective-medium theory (CEMT), which are used to engineer the radially varying anisotropic artificial material based on the thin alternating cylindrical metal and dielectric layers. The radial gradient of the effective anisotropic optical constants allows for matching the impedances at the input and output interfaces, drastically improving the throughput of the lenslet. However, it is the use of the zeroth-order CEMT that enables the practical realization of a gradient hyperlens with realistic materials. To illustrate the importance of using the CEMT versus the conventional planar effective-medium theory (PEMT) for cylindrical anisotropic systems, such as our hyperlens, both the CEMT and PEMT are adopted to design gradient hyperlenses with the same materials and order of elemental layers. The CEMT- and PEMT-based designs show similar performance if the number of metal-dielectric binary layers is sufficiently large (9+ pairs) and if the layers are sufficiently thin. However, for the manufacturable lenses with realistic numbers of layers (e.g. five pairs) and thicknesses, the performance of the CEMT design continues to be practical, whereas the PEMT-based design stops working altogether. The accurate design of transformation optics-based layered cylindrical devices enabled by CEMT allow for a new class of robustly manufacturable nanophotonic systems, even with relatively thick layers of real-life materials.

Enface Thickness Mapping and Reflectance Imaging of Retinal Layers in Diabetic Retinopathy.

PubMed

Francis, Andrew W; Wanek, Justin; Lim, Jennifer I; Shahidi, Mahnaz

2015-01-01

To present a method for image segmentation and generation of enface thickness maps and reflectance images of retinal layers in healthy and diabetic retinopathy (DR) subjects. High density spectral domain optical coherence tomography (SDOCT) images were acquired in 10 healthy and 4 DR subjects. Customized image analysis software identified 5 retinal cell layer interfaces and generated thickness maps and reflectance images of the total retina (TR), inner retina (IR), outer retina (OR), and the inner segment ellipsoid (ISe) band. Thickness maps in DR subjects were compared to those of healthy subjects by generating deviation maps which displayed retinal locations with thickness below, within, and above the normal 95% confidence interval. In healthy subjects, TR and IR thickness maps displayed the foveal depression and increased thickness in the parafoveal region. OR and ISe thickness maps showed increased thickness at the fovea, consistent with normal retinal anatomy. In DR subjects, thickening and thinning in localized regions were demonstrated on TR, IR, OR, and ISe thickness maps, corresponding to retinal edema and atrophy, respectively. TR and OR reflectance images showed reduced reflectivity in regions of increased thickness. Hard exudates appeared as hyper-reflective spots in IR reflectance images and casted shadows on the deeper OR and ISe reflectance images. The ISe reflectance image clearly showed the presence of focal laser scars. Enface thickness mapping and reflectance imaging of retinal layers is a potentially useful method for quantifying the spatial and axial extent of pathologies due to DR.

Enface Thickness Mapping and Reflectance Imaging of Retinal Layers in Diabetic Retinopathy

PubMed Central

Francis, Andrew W.; Wanek, Justin; Lim, Jennifer I.; Shahidi, Mahnaz

2015-01-01

Purpose To present a method for image segmentation and generation of enface thickness maps and reflectance images of retinal layers in healthy and diabetic retinopathy (DR) subjects. Methods High density spectral domain optical coherence tomography (SDOCT) images were acquired in 10 healthy and 4 DR subjects. Customized image analysis software identified 5 retinal cell layer interfaces and generated thickness maps and reflectance images of the total retina (TR), inner retina (IR), outer retina (OR), and the inner segment ellipsoid (ISe) band. Thickness maps in DR subjects were compared to those of healthy subjects by generating deviation maps which displayed retinal locations with thickness below, within, and above the normal 95% confidence interval. Results In healthy subjects, TR and IR thickness maps displayed the foveal depression and increased thickness in the parafoveal region. OR and ISe thickness maps showed increased thickness at the fovea, consistent with normal retinal anatomy. In DR subjects, thickening and thinning in localized regions were demonstrated on TR, IR, OR, and ISe thickness maps, corresponding to retinal edema and atrophy, respectively. TR and OR reflectance images showed reduced reflectivity in regions of increased thickness. Hard exudates appeared as hyper-reflective spots in IR reflectance images and casted shadows on the deeper OR and ISe reflectance images. The ISe reflectance image clearly showed the presence of focal laser scars. Conclusions Enface thickness mapping and reflectance imaging of retinal layers is a potentially useful method for quantifying the spatial and axial extent of pathologies due to DR. PMID:26699878

Optical properties of hybrid quantum-well–dots nanostructures grown by MOCVD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mintairov, S. A., E-mail: mintairov@scell.ioffe.ru; Kalyuzhnyy, N. A.; Nadtochiy, A. M.

The deposition of In{sub x}Ga{sub 1–x}As with an indium content of 0.3–0.5 and an average thickness of 3–27 single layers on a GaAs wafer by metalorganic chemical vapor deposition (MOCVD) at low temperatures results in the appearance of thickness and composition modulations in the layers being formed. Such structures can be considered to be intermediate nanostructures between ideal quantum wells and quantum dots. Depending on the average thickness and composition of the layers, the wavelength of the photoluminescence peak for the hybrid InGaAs quantum well–dots nanostructures varies from 950 to 1100 nm. The optimal average In{sub x}Ga{sub 1–x}As thicknesses andmore » compositions at which the emission wavelength is the longest with a high quantum efficiency retained are determined.« less

The Effects of Zr Doping on the Optical, Electrical and Microstructural Properties of Thin ZnO Films Deposited by Atomic Layer Deposition

PubMed Central

Herodotou, Stephania; Treharne, Robert E.; Durose, Ken; Tatlock, Gordon J.; Potter, Richard J.

2015-01-01

Transparent conducting oxides (TCOs), with high optical transparency (≥85%) and low electrical resistivity (10−4 Ω·cm) are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant materials. In the current study, we dope Zr into thin ZnO films grown by atomic layer deposition (ALD) to target properties of an efficient TCO. The effects of doping (0–10 at.% Zr) were investigated for ~100 nm thick films and the effect of thickness on the properties was investigated for 50–250 nm thick films. The addition of Zr4+ ions acting as electron donors showed reduced resistivity (1.44 × 10−3 Ω·cm), increased carrier density (3.81 × 1020 cm−3), and increased optical gap (3.5 eV) with 4.8 at.% doping. The increase of film thickness to 250 nm reduced the electron carrier/photon scattering leading to a further reduction of resistivity to 7.5 × 10−4 Ω·cm and an average optical transparency in the visible/near infrared (IR) range up to 91%. The improved n-type properties of ZnO: Zr films are promising for TCO applications after reaching the targets for high carrier density (>1020 cm−3), low resistivity in the order of 10−4 Ω·cm and high optical transparency (≥85%). PMID:28793633

The structure and function of the macula in patients with advanced retinitis pigmentosa.

PubMed

Vámos, Rita; Tátrai, Erika; Németh, János; Holder, Graham E; DeBuc, Delia Cabrera; Somfai, Gábor Márk

2011-10-28

To assess the structure and function of the macula in advanced retinitis pigmentosa (RP). Twenty-nine eyes of 22 patients with RP were compared against 17 control eyes. Time-domain optical coherence tomography (OCT) data were processed using OCTRIMA (optical coherence tomography retinal image analysis) as a means of quantifying commercial OCT system images. The thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer complex (GCL+IPL), inner nuclear layer and outer plexiform layer complex (INL+OPL), and the outer nuclear layer (ONL) were measured. Multifocal electroretinography (mfERG) was performed; two groups were formed based on the mfERG findings. Fourteen eyes had no detectable central retinal function (NCRF) on mfERG; detectable but abnormal retinal function (DRF) was present in the mfERG of the other 15 eyes. The thickness of the ONL in the central macular region was significantly less in the NCRF eyes compared with that in both DRF eyes and controls. The ONL was significantly thinner in the pericentral region in both patient groups compared with that in controls, whereas the thickness of the GCL+IPL and INL+OPL was significantly decreased only in the NCRF eyes. The RNFL in the peripheral region was significantly thicker, whereas the thickness of the GCL+IPL and ONL was significantly thinner in both patient groups compared with that in controls. The results are consistent with degeneration of the outer retina preceding inner retinal changes in RP. OCT image segmentation enables objective evaluation of retinal structural changes in RP, with potential use in the planning of therapeutic interventions and conceivably as an outcome measure.

The Structure and Function of the Macula in Patients with Advanced Retinitis Pigmentosa

PubMed Central

Vámos, Rita; Tátrai, Erika; Németh, János; Holder, Graham E.; DeBuc, Delia Cabrera

2011-01-01

Purpose. To assess the structure and function of the macula in advanced retinitis pigmentosa (RP). Methods. Twenty-nine eyes of 22 patients with RP were compared against 17 control eyes. Time-domain optical coherence tomography (OCT) data were processed using OCTRIMA (optical coherence tomography retinal image analysis) as a means of quantifying commercial OCT system images. The thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer complex (GCL+IPL), inner nuclear layer and outer plexiform layer complex (INL+OPL), and the outer nuclear layer (ONL) were measured. Multifocal electroretinography (mfERG) was performed; two groups were formed based on the mfERG findings. Fourteen eyes had no detectable central retinal function (NCRF) on mfERG; detectable but abnormal retinal function (DRF) was present in the mfERG of the other 15 eyes. Results. The thickness of the ONL in the central macular region was significantly less in the NCRF eyes compared with that in both DRF eyes and controls. The ONL was significantly thinner in the pericentral region in both patient groups compared with that in controls, whereas the thickness of the GCL+IPL and INL+OPL was significantly decreased only in the NCRF eyes. The RNFL in the peripheral region was significantly thicker, whereas the thickness of the GCL+IPL and ONL was significantly thinner in both patient groups compared with that in controls. Conclusions. The results are consistent with degeneration of the outer retina preceding inner retinal changes in RP. OCT image segmentation enables objective evaluation of retinal structural changes in RP, with potential use in the planning of therapeutic interventions and conceivably as an outcome measure. PMID:21948552

Effect of duration and severity of migraine on retinal nerve fiber layer, ganglion cell layer, and choroidal thickness.

PubMed

Abdellatif, Mona K; Fouad, Mohamed M

2018-03-01

To investigate the factors in migraine that have the highest significance on retinal and choroidal layers' thickness. Ninety patients with migraine and 40 age-matched healthy participants were enrolled in this observational, cross-sectional study. After full ophthalmological examination, spectral domain-optical coherence tomography was done for all patients measuring the thickness of ganglion cell layer and retinal nerve fiber layer. Enhanced depth imaging technique was used to measure the choroidal thickness. There was significant thinning in the superior and inferior ganglion cell layers, all retinal nerve fiber layer quadrants, and all choroidal quadrants (except for the central subfield) in migraineurs compared to controls. The duration of migraine was significantly correlated with ganglion cell layer, retinal nerve fiber layer, and all choroidal quadrants, while the severity of migraine was significantly correlated with ganglion cell layer and retinal nerve fiber layer only. Multiregression analysis showed that the duration of migraine is the most important determinant factor of the superior retinal nerve fiber layer quadrant (β = -0.375, p = 0.001) and in all the choroidal quadrants (β = -0.531, -0.692, -0.503, -0.461, -0.564, respectively, p  < 0.001), while severity is the most important determinant factor of inferior, nasal, and temporal retinal nerve fiber layer quadrants (β = -0.256, -0.335, -0.308; p  = 0.036, 0.005, 0.009, respectively) and the inferior ganglion cell layer hemisphere (β = -0.377 and p = 0.001). Ganglion cell layer, retinal nerve fiber layer, and choroidal thickness are significantly thinner in patients with migraine. The severity of migraine has more significant influence in the thinning of ganglion cell layer and retinal nerve fiber layer, while the duration of the disease affected the choroidal thickness more.

Second Harmonic Generation characterization of SOI wafers: Impact of layer thickness and interface electric field

NASA Astrophysics Data System (ADS)

Damianos, D.; Vitrant, G.; Lei, M.; Changala, J.; Kaminski-Cachopo, A.; Blanc-Pelissier, D.; Cristoloveanu, S.; Ionica, I.

2018-05-01

In this work, we investigate Second Harmonic Generation (SHG) as a non-destructive characterization method for Silicon-On-Insulator (SOI) materials. For thick SOI stacks, the SHG signal is related to the thickness variations of the different layers. However, in thin SOI films, the comparison between measurements and optical modeling suggests a supplementary SHG contribution attributed to the electric fields at the SiO2/Si interfaces. The impact of the electric field at each interface of the SOI on the SHG is assessed. The SHG technique can be used to evaluate interfacial electric fields and consequently interface charge density in SOI materials.

Theoretical investigation on multilayer nanocomposite-based fiber optic SPR sensor

NASA Astrophysics Data System (ADS)

Shojaie, Ehsan; Madanipour, Khosro; Gharibzadeh, Azadeh; Abbasi, Shabnam

2017-06-01

In this work, a multilayer nanocomposite based fiber optic SPR sensor is considered and especially designed for CO2 gas detection. This proposed fiber sensor consists of fiber core, gold-silver alloy and the absorber layers. The investigation is based on the evaluation of the transmitted-power derived under the transfer matrix method and the multiple-reflection in the sensing area. In terms of sensitivity, the sensor performance is studied theoretically under various conditions related to the metal layer and its gold and silver nanoparticles to form a single alloy film. Effect of additional parameters such as the ratio of the alloy composition and the thickness of the alloy film on the performance of the SPR sensor is studied, as well. Finally, a four-layer structure is introduced to detect carbon dioxide gas. It contains core fiber, gold-silver alloy layer, an absorbent layer of carbon dioxide gas (KOH) and measurement environment. Lower price and size are the main advantages of using such a sensor in compare with commercial (NDIR) gas sensor. Theoretical results show by increasing the metal layer thickness the sensitivity of sensor is increased, and by increasing the ratio of the gold in alloy the sensitivity is decreased.

Preparation and characterization of B4C coatings for advanced research light sources.

PubMed

Störmer, Michael; Siewert, Frank; Sinn, Harald

2016-01-01

X-ray optical elements are required for beam transport at the current and upcoming free-electron lasers and synchrotron sources. An X-ray mirror is a combination of a substrate and a coating. The demand for large mirrors with single layers consisting of light or heavy elements has increased during the last few decades; surface finishing technology is currently able to process mirror lengths up to 1 m with microroughness at the sub-nanometre level. Additionally, thin-film fabrication is able to deposit a suitable single-layer material, such as boron carbide (B4C), some tens of nanometres thick. After deposition, the mirror should provide excellent X-ray optical properties with respect to coating thickness errors, microroughness values and slope errors; thereby enabling the mirror to transport the X-ray beam with high reflectivity, high beam flux and an undistorted wavefront to an experimental station. At the European XFEL, the technical specifications of the future mirrors are extraordinarily challenging. The acceptable shape error of the mirrors is below 2 nm along the whole length of 1 m. At the Helmholtz-Zentrum Geesthacht (HZG), amorphous layers of boron carbide with thicknesses in the range 30-60 nm were fabricated using the HZG sputtering facility, which is able to cover areas up to 1500 mm long by 120 mm wide in one step using rectangular B4C sputtering targets. The available deposition area is suitable for the specified X-ray mirror dimensions of upcoming advanced research light sources such as the European XFEL. The coatings produced were investigated by means of X-ray reflectometry and interference microscopy. The experimental results for the B4C layers are discussed according to thickness uniformity, density, microroughness and thermal stability. The variation of layer thickness in the tangential and sagittal directions was investigated in order to estimate the achieved level of uniformity over the whole deposition area, which is considerably larger than the optical area of a mirror. A waisted mask was positioned during deposition between the sputtering source and substrate to improve the thickness uniformity; particularly to prevent the formation a convex film shape in the sagittal direction. Additionally the inclination of the substrate was varied to change the layer uniformity in order to optimize the position of the mirror quality deposited area during deposition. The level of mirror microroughness was investigated for different substrates before and after deposition of a single layer of B4C. The thermal stability of the B4C layers on the various substrate materials was investigated.

Preparation and characterization of B4C coatings for advanced research light sources

PubMed Central

Störmer, Michael; Siewert, Frank; Sinn, Harald

2016-01-01

X-ray optical elements are required for beam transport at the current and upcoming free-electron lasers and synchrotron sources. An X-ray mirror is a combination of a substrate and a coating. The demand for large mirrors with single layers consisting of light or heavy elements has increased during the last few decades; surface finishing technology is currently able to process mirror lengths up to 1 m with microroughness at the sub-nanometre level. Additionally, thin-film fabrication is able to deposit a suitable single-layer material, such as boron carbide (B4C), some tens of nanometres thick. After deposition, the mirror should provide excellent X-ray optical properties with respect to coating thickness errors, microroughness values and slope errors; thereby enabling the mirror to transport the X-ray beam with high reflectivity, high beam flux and an undistorted wavefront to an experimental station. At the European XFEL, the technical specifications of the future mirrors are extraordinarily challenging. The acceptable shape error of the mirrors is below 2 nm along the whole length of 1 m. At the Helmholtz-Zentrum Geesthacht (HZG), amorphous layers of boron carbide with thicknesses in the range 30–60 nm were fabricated using the HZG sputtering facility, which is able to cover areas up to 1500 mm long by 120 mm wide in one step using rectangular B4C sputtering targets. The available deposition area is suitable for the specified X-ray mirror dimensions of upcoming advanced research light sources such as the European XFEL. The coatings produced were investigated by means of X-ray reflectometry and interference microscopy. The experimental results for the B4C layers are discussed according to thickness uniformity, density, microroughness and thermal stability. The variation of layer thickness in the tangential and sagittal directions was investigated in order to estimate the achieved level of uniformity over the whole deposition area, which is considerably larger than the optical area of a mirror. A waisted mask was positioned during deposition between the sputtering source and substrate to improve the thickness uniformity; particularly to prevent the formation a convex film shape in the sagittal direction. Additionally the inclination of the substrate was varied to change the layer uniformity in order to optimize the position of the mirror quality deposited area during deposition. The level of mirror microroughness was investigated for different substrates before and after deposition of a single layer of B4C. The thermal stability of the B4C layers on the various substrate materials was investigated. PMID:26698045

Measuring the complex optical conductivity of graphene by Fabry-Pérot reflectance spectroscopy [Determination of the optical index for few-layer graphene by reflectivity spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghamsari, Behnood G.; Tosado, Jacob; Yamamoto, Mahito

Here, we have experimentally studied the optical refractive index of few-layer graphene through reflection spectroscopy at visible wavelengths. A laser scanning microscope (LSM) with a coherent supercontinuum laser source measured the reflectivity of an exfoliated graphene flake on a Si/SiO 2 substrate, containing monolayer, bilayer and trilayer areas, as the wavelength of the laser was varied from 545nm to 710nm. The complex refractive index of few-layer graphene, n-ik, was extracted from the reflectivity contrast to the bare substrate and the Fresnel reflection theory. Since the SiO 2 thickness enters to the modeling as a parameter, it was precisely measured atmore » the location of the sample. It was found that a common constant optical index cannot explain the wavelength-dependent reflectivity data for single-, double- and three-layer graphene simultaneously, but rather each individual few-layer graphene possesses a unique optical index whose complex values were precisely and accurately determined from the experimental data.« less

Measuring the complex optical conductivity of graphene by Fabry-Pérot reflectance spectroscopy [Determination of the optical index for few-layer graphene by reflectivity spectroscopy

DOE PAGES

Ghamsari, Behnood G.; Tosado, Jacob; Yamamoto, Mahito; ...

2016-09-29

Here, we have experimentally studied the optical refractive index of few-layer graphene through reflection spectroscopy at visible wavelengths. A laser scanning microscope (LSM) with a coherent supercontinuum laser source measured the reflectivity of an exfoliated graphene flake on a Si/SiO 2 substrate, containing monolayer, bilayer and trilayer areas, as the wavelength of the laser was varied from 545nm to 710nm. The complex refractive index of few-layer graphene, n-ik, was extracted from the reflectivity contrast to the bare substrate and the Fresnel reflection theory. Since the SiO 2 thickness enters to the modeling as a parameter, it was precisely measured atmore » the location of the sample. It was found that a common constant optical index cannot explain the wavelength-dependent reflectivity data for single-, double- and three-layer graphene simultaneously, but rather each individual few-layer graphene possesses a unique optical index whose complex values were precisely and accurately determined from the experimental data.« less

A Fast Hyperspectral Vector Radiative Transfer Model in UV to IR spectral bands

NASA Astrophysics Data System (ADS)

Ding, J.; Yang, P.; Sun, B.; Kattawar, G. W.; Platnick, S. E.; Meyer, K.; Wang, C.

2016-12-01

We develop a fast hyperspectral vector radiative transfer model with a spectral range from UV to IR with 5 nm resolutions. This model can simulate top of the atmosphere (TOA) diffuse radiance and polarized reflectance by considering gas absorption, Rayleigh scattering, and aerosol and cloud scattering. The absorption component considers several major atmospheric absorbers such as water vapor, CO2, O3, and O2 including both line and continuum absorptions. A regression-based method is used to parameterize the layer effective optical thickness for each gas, which substantially increases the computation efficiency for absorption while maintaining high accuracy. This method is over 500 times faster than the existing line-by-line method. The scattering component uses the successive order of scattering (SOS) method. For Rayleigh scattering, convergence is fast due to the small optical thickness of atmospheric gases. For cloud and aerosol layers, a small-angle approximation method is used in SOS calculations. The scattering process is divided into two parts, a forward part and a diffuse part. The scattering in the small-angle range in the forward direction is approximated as forward scattering. A cloud or aerosol layer is divided into thin layers. As the ray propagates through each thin layer, a portion diverges as diffuse radiation, while the remainder continues propagating in forward direction. The computed diffuse radiance is the sum of all of the diffuse parts. The small-angle approximation makes the SOS calculation converge rapidly even in a thick cloud layer.

SiGe layer thickness effect on the structural and optical properties of well-organized SiGe/SiO2 multilayers

NASA Astrophysics Data System (ADS)

Vieira, E. M. F.; Toudert, J.; Rolo, A. G.; Parisini, A.; Leitão, J. P.; Correia, M. R.; Franco, N.; Alves, E.; Chahboun, A.; Martín-Sánchez, J.; Serna, R.; Gomes, M. J. M.

2017-08-01

In this work, we report on the production of regular (SiGe/SiO2)20 multilayer structures by conventional RF-magnetron sputtering, at 350 °C. Transmission electron microscopy, scanning transmission electron microscopy, raman spectroscopy, and x-ray reflectometry measurements revealed that annealing at a temperature of 1000 °C leads to the formation of SiGe nanocrystals between SiO2 thin layers with good multilayer stability. Reducing the nominal SiGe layer thickness (t SiGe) from 3.5-2 nm results in a transition from continuous SiGe crystalline layer (t SiGe ˜ 3.5 nm) to layers consisting of isolated nanocrystals (t SiGe ˜ 2 nm). Namely, in the latter case, the presence of SiGe nanocrystals ˜3-8 nm in size, is observed. Spectroscopic ellipsometry was applied to determine the evolution of the onset in the effective optical absorption, as well as the dielectric function, in SiGe multilayers as a function of the SiGe thickness. A clear blue-shift in the optical absorption is observed for t SiGe ˜ 2 nm multilayer, as a consequence of the presence of isolated nanocrystals. Furthermore, the observed near infrared values of n = 2.8 and k = 1.5 are lower than those of bulk SiGe compounds, suggesting the presence of electronic confinement effects in the nanocrystals. The low temperature (70 K) photoluminescence measurements performed on annealed SiGe/SiO2 nanostructures show an emission band located between 0.7-0.9 eV associated with the development of interface states between the formed nanocrystals and surrounding amorphous matrix.

Illumination angle and layer thickness influence on the photo current generation in organic solar cells: A combined simulative and experimental study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mescher, Jan, E-mail: jan.mescher@kit.edu; Mertens, Adrian; Egel, Amos

2015-07-15

In most future organic photovoltaic applications, such as fixed roof installations, facade or clothing integration, the solar cells will face the sun under varying angles. By a combined simulative and experimental study, we investigate the mutual interdependencies of the angle of light incidence, the absorber layer thickness and the photon harvesting efficiency within a typical organic photovoltaic device. For thin absorber layers, we find a steady decrease of the effective photocurrent towards increasing angles. For 90-140 nm thick absorber layers, however, we observe an effective photocurrent enhancement, exhibiting a maximum yield at angles of incidence of about 50°. Both effectsmore » mainly originate from the angle-dependent spatial broadening of the optical interference pattern inside the solar cell and a shift of the absorption maximum away from the metal electrode.« less

Manufacturing polymer light emitting diode with high luminance efficiency by solution process

NASA Astrophysics Data System (ADS)

Kim, Miyoung; Jo, SongJin; Yang, Ho Chang; Yoon, Dang Mo; Kwon, Jae-Taek; Lee, Seung-Hyun; Choi, Ju Hwan; Lee, Bum-Joo; Shin, Jin-Koog

2012-06-01

While investigating polymer light emitting diodes (polymer-LEDs) fabricated by solution process, surface roughness influences electro-optical (E-O) characteristics. We expect that E-O characteristics such as luminance and power efficiency related to surface roughness and layer thickness of emitting layer with poly-9-Vinylcarbazole. In this study, we fabricated polymer organic light emitting diodes by solution process which guarantees easy, eco-friendly and low cost manufacturing for flexible display applications. In order to obtain high luminescence efficiency, E-O characteristics of these devices by varying parameters for printing process have been investigated. Therefore, we optimized process condition for polymer-LEDs by adjusting annealing temperatures of emission, thickness of emission layer showing efficiency (10.8 cd/A) at 10 mA/cm2. We also checked wavelength dependent electroluminescence spectrum in order to find the correlation between the variation of efficiency and the thickness of the layer.

Illumination angle and layer thickness influence on the photo current generation in organic solar cells: A combined simulative and experimental study

NASA Astrophysics Data System (ADS)

Mescher, Jan; Mertens, Adrian; Egel, Amos; Kettlitz, Siegfried W.; Lemmer, Uli; Colsmann, Alexander

2015-07-01

In most future organic photovoltaic applications, such as fixed roof installations, facade or clothing integration, the solar cells will face the sun under varying angles. By a combined simulative and experimental study, we investigate the mutual interdependencies of the angle of light incidence, the absorber layer thickness and the photon harvesting efficiency within a typical organic photovoltaic device. For thin absorber layers, we find a steady decrease of the effective photocurrent towards increasing angles. For 90-140 nm thick absorber layers, however, we observe an effective photocurrent enhancement, exhibiting a maximum yield at angles of incidence of about 50°. Both effects mainly originate from the angle-dependent spatial broadening of the optical interference pattern inside the solar cell and a shift of the absorption maximum away from the metal electrode.

Catalyst-free growth of ZnO nanowires on ITO seed/glass by thermal evaporation method: Effects of ITO seed layer thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alsultany, Forat H., E-mail: foratusm@gmail.com; Ahmed, Naser M.; Hassan, Z.

A seed/catalyst-free growth of ZnO nanowires (ZnO-NWs) on a glass substrate were successfully fabricated using thermal evaporation technique. These nanowires were grown on ITO seed layers of different thicknesses of 25 and 75 nm, which were deposited on glass substrates by radio frequency (RF) magnetron sputtering. Prior to synthesized ITO nanowires, the sputtered ITO seeds were annealed using the continuous wave (CW) CO2 laser at 450 °C in air for 15 min. The effect of seed layer thickness on the morphological, structural, and optical properties of ZnO-NWs were systematically investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM),more » and UV-Vis spectrophotometer.« less

Development of graphene process control by industrial optical spectroscopy setup

NASA Astrophysics Data System (ADS)

Fursenko, O.; Lukosius, M.; Lupina, G.; Bauer, J.; Villringer, C.; Mai, A.

2017-06-01

The successful integration of graphene into microelectronic devices depends strongly on the availability of fast and nondestructive characterization methods of graphene grown by CVD on large diameter production wafers [1-3] which are in the interest of the semiconductor industry. Here, a high-throughput optical metrology method for measuring the thickness and uniformity of large-area graphene sheets is demonstrated. The method is based on the combination of spectroscopic ellipsometry and normal incidence reflectometry in UV-Vis wavelength range (200-800 nm) with small light spots ( 30 μm2) realized in wafer optical metrology tool. In the first step graphene layers were transferred on a SiO2/Si substrate in order to determine the optical constants of graphene by the combination of multi-angle ellipsometry and reflectometry. Then these data were used for the development of a process control recipe of CVD graphene on 200 mm Ge(100)/Si(100) wafers. The graphene layer quality was additionally monitored by Raman spectroscopy. Atomic force microscopy measurements were performed for micro topography evaluation. In consequence, a robust recipe for unambiguous thickness monitoring of all components of a multilayer film stack, including graphene, surface residuals or interface layer underneath graphene and surface roughness is developed. Optical monitoring of graphene thickness uniformity over a wafer has shown an excellent long term stability (s=0.004 nm) regardless of the growth of interfacial GeO2 and surface roughness. The sensitivity of the optical identification of graphene during microelectronic processing was evaluated. This optical metrology technique with combined data collection exhibit a fast and highly precise method allowing one an unambiguous detection of graphene after transferring as well as after the CVD deposition process on a Ge(100)/Si(100) wafer. This approach is well suited for industrial applications due to its repeatability and flexibility.

Space-time modeling of the photon diffusion in a three-layered model: application to the study of muscular oxygenation

NASA Astrophysics Data System (ADS)

Mansouri, C.; L'Huillier, J. P.; Piron, V.

2007-07-01

This work presents results on the modeling of the photon diffusion in a three-layered model, (skin, fat and muscle). The Finite Element method was performed in order to calculate the temporal response of the above-mentioned structure. The thickness of the fat layer was varied from 1 to 15 mm to investigate the effects of increasing fat thickness on the muscle layer absorption coefficient measurements for a source-detector spacing of 30 mm. The simulated time-resolved reflectance data, at different wavelengths, were fitted to the diffusion model to yield the scattering and absorption coefficients of muscle. The errors in estimating muscle absorption coefficients μ α depend on the thickness of the fat layer and its optical properties. In addition, it was shown that it is possible to recover with a good precision (~2.6 % of error) the absorption coefficient of muscle and this up to a thickness of the fat layer not exceeding 4mm. Beyond this limit a correction is proposed in order to make measurements coherent. The muscle-corrected absorption coefficient can be then used to calculate hemoglobin oxygenation.

Electrode with transparent series resistance for uniform switching of optical modulation devices

DOEpatents

Tench, D Morgan [Camarillo, CA; Cunningham, Michael A [Thousand Oaks, CA; Kobrin, Paul H [Newbury Park, CA

2008-01-08

Switching uniformity of an optical modulation device for controlling the propagation of electromagnetic radiation is improved by use of an electrode comprising an electrically resistive layer that is transparent to the radiation. The resistive layer is preferably an innerlayer of a wide-bandgap oxide sandwiched between layers of indium tin oxide or another transparent conductor, and may be of uniform thickness, or may be graded so as to provide further improvement in the switching uniformity. The electrode may be used with electrochromic and reversible electrochemical mirror (REM) smart window devices, as well as display devices based on various technologies.

Optic nerve head cupping in glaucomatous and non-glaucomatous optic neuropathy.

PubMed

Fard, Masoud Aghsaei; Moghimi, Sasan; Sahraian, Alireza; Ritch, Robert

2018-05-23

Enlargement of optic disc cupping is seen both in glaucoma and in neurological disorders. We used enhanced depth imaging with spectral-domain optical coherence tomography to differentiate glaucoma from non-glaucomatous optic neuropathy. The optic discs were scanned in this prospective comparative study, and the lamina cribrosa (LC) thickness and anterior laminar depth (ALD) in the central, superior and inferior optic nerve head, and peripapillary choroidal thicknesses, were measured. There were 31 eyes of 31 patients with severe glaucoma and 33 eyes of 19 patients with non-glaucomatous cupping. Eyes of 29 healthy controls were also enrolled. There was no significant difference in the cup-to-disc ratio and in the average peripapillary nerve fibre layer thickness between the glaucoma and non-glaucomatous cupping groups (p>0.99). The average peripapillary choroidal thickness was thinner in glaucoma eyes than in the control eyes after adjusting for age and axial length. Glaucomatous and non-glaucomatous eyes had greater ALD and thinner LC than the control eyes (p<0.001 for both). ALDs of glaucoma eyes were deeper than non-glaucomatous eyes (p=0.01 for central ALD) when age, axial length and peripapillary choroidal thickness were included in the linear mixed model. Prelaminar thickness and LC thickness of glaucoma eyes were not different from non-glaucomatous eyes after adjusting. Deeper ALD was observed in glaucoma than non-glaucomatous cupping after adjusting for choroidal thickness. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Application of scanning angle Raman spectroscopy for determining the location of buried polymer interfaces with tens of nanometer precision

DOE PAGES

Damin, Craig A.; Nguyen, Vy H. T.; Niyibizi, Auguste S.; ...

2015-02-11

In this study, near-infrared scanning angle (SA) Raman spectroscopy was utilized to determine the interface location in bilayer films (a stack of two polymer layers) of polystyrene (PS) and polycarbonate (PC). Finite-difference-time-domain (FDTD) calculations of the sum square electric field (SSEF) for films with total bilayer thicknesses of 1200–3600 nm were used to construct models for simultaneously measuring the film thickness and the location of the buried interface between the PS and PC layers. Samples with total thicknesses of 1320, 1890, 2300, and 2750 nm and varying PS/PC interface locations were analyzed using SA Raman spectroscopy. Comparing SA Raman spectroscopymore » and optical profilometry measurements, the average percent difference in the total bilayer thickness was 2.0% for films less than ~2300 nm thick. The average percent difference in the thickness of the PS layer, which reflects the interface location, was 2.5% when the PS layer was less than ~1800 nm. SA Raman spectroscopy has been shown to be a viable, non-destructive method capable of determining the total bilayer thickness and buried interface location for bilayer samples consisting of thin polymer films with comparable indices of refraction.« less

Optical characterization of thin nickel films on polymer substrates using reflectance difference spectroscopy

NASA Astrophysics Data System (ADS)

Rinnerbauer, V.; Schmidegg, K.; Hohage, M.; Sun, L. D.; Flores-Camacho, J. M.; Zeppenfeld, P.

2009-06-01

We have used reflectance difference spectroscopy (RDS) and its extension, azimuth-dependent RDS (ADRDS), to study the properties of sputtered and evaporated nickel films on biaxially oriented poly(ethylene terephtalate) (PET) films in a roll to roll web-coating process. From the full set of ADRDS spectra we extract and analyze both the intrinsic RDS spectra and the azimuthal orientation of the effective optical anisotropy of the samples. From the latter, contributions to the RDS spectra arising from the nickel layer and the PET substrate with different orientations of the optical eigenaxes can be inferred. We find an attenuation of the characteristic RDS signal of the PET substrate with increasing nickel film thickness which is in good agreement with the theoretical prediction. For film thicknesses above 20 nm another contribution to the RDS signal attributed to the optical anisotropy of the deposited nickel layers can be observed. Its strength depends on the deposition method, and is considerably larger for evaporated films than for sputtered ones. With increasing nickel film thickness, the azimuthal orientation of the sample anisotropy changes from the initial value of the PET substrate by about 20° toward the machine direction of the foil. We demonstrate that RDS is also a valuable tool for inline monitoring in the roll to roll process, as the attenuation of the RDS signal, under proper consideration of the orientation of the effective anisotropy, is a function of the film thickness and characteristic for the deposited material.

Segmented inner plexiform layer thickness as a potential biomarker to evaluate open-angle glaucoma: Dendritic degeneration of retinal ganglion cell.

PubMed

Kim, Eun Kyoung; Park, Hae-Young Lopilly; Park, Chan Kee

2017-01-01

To evaluate the changes of retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), and ganglion cell-inner plexiform layer (GCIPL) thicknesses and compare structure-function relationships of 4 retinal layers using spectral-domain optical coherence tomography (SD-OCT) in macular region of glaucoma patients. In cross-sectional study, a total of 85 eyes with pre-perimetric to advanced glaucoma and 26 normal controls were enrolled. The glaucomatous eyes were subdivided into three groups according to the severity of visual field defect: a preperimetric glaucoma group, an early glaucoma group, and a moderate to advanced glaucoma group. RNFL, GCL, IPL, and GCIPL thicknesses were measured at the level of the macula by the Spectralis (Heidelberg Engineering, Heidelberg, Germany) SD-OCT with automated segmentation software. For functional evaluation, corresponding mean sensitivity (MS) values were measured using 24-2 standard automated perimetry (SAP). RNFL, GCL, IPL, and GCIPL thicknesses were significantly different among 4 groups (P < .001). Macular structure losses were positively correlated with the MS values of the 24-2 SAP for RNFL, GCL, IPL, and GCIPL (R = 0.553, 0.636, 0.648 and 0.646, respectively, P < .001). In regression analysis, IPL and GCIPL thicknesses showed stronger association with the corresponding MS values of 24-2 SAP compared with RNFL and GCL thicknesses (R2 = 0.420, P < .001 for IPL; R2 = 0.417, P< .001 for GCIPL thickness). Segmented IPL thickness was significantly associated with the degree of glaucoma. Segmental analysis of the inner retinal layer including the IPL in macular region may provide valuable information for evaluating glaucoma.

New Normative Database of Inner Macular Layer Thickness Measured by Spectralis OCT Used as Reference Standard for Glaucoma Detection.

PubMed

Nieves-Moreno, María; Martínez-de-la-Casa, José M; Bambo, María P; Morales-Fernández, Laura; Van Keer, Karel; Vandewalle, Evelien; Stalmans, Ingeborg; García-Feijoó, Julián

2018-02-01

This study examines the capacity to detect glaucoma of inner macular layer thickness measured by spectral-domain optical coherence tomography (SD-OCT) using a new normative database as the reference standard. Participants ( N = 148) were recruited from Leuven (Belgium) and Zaragoza (Spain): 74 patients with early/moderate glaucoma and 74 age-matched healthy controls. One eye was randomly selected for a macular scan using the Spectralis SD-OCT. The variables measured with the instrument's segmentation software were: macular nerve fiber layer (mRNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) volume and thickness along with circumpapillary RNFL thickness (cpRNFL). The new normative database of macular variables was used to define the cutoff of normality as the fifth percentile by age group. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) of each macular measurement and of cpRNFL were used to distinguish between patients and controls. Overall sensitivity and specificity to detect early-moderate glaucoma were 42.2% and 88.9% for mRNFL, 42.4% and 95.6% for GCL, 42.2% and 94.5% for IPL, and 53% and 94.6% for RNFL, respectively. The best macular variable to discriminate between the two groups of subjects was outer temporal GCL thickness as indicated by an AUROC of 0.903. This variable performed similarly to mean cpRNFL thickness (AUROC = 0.845; P = 0.29). Using our normative database as reference, the diagnostic power of inner macular layer thickness proved comparable to that of peripapillary RNFL thickness. Spectralis SD-OCT, cpRNFL thickness, and individual macular inner layer thicknesses show comparable diagnostic capacity for glaucoma and RNFL, GCL, and IPL thickness may be useful as an alternative diagnostic test when the measure of cpRNFL shows artifacts.

Optical Metrology for CIGS Solar Cell Manufacturing and its Cost Implications

NASA Astrophysics Data System (ADS)

Sunkoju, Sravan Kumar

Solar energy is a promising source of renewable energy which can meet the demand for clean energy in near future with advances in research in the field of photovoltaics and cost reduction by commercialization. Availability of a non-contact, in-line, real time robust process control strategies can greatly aid in reducing the gap between cell and module efficiencies, thereby leading to cost-effective large-scale manufacturing of high efficiency CIGS solar cells. In order to achieve proper process monitoring and control for the deposition of the functional layers of CuIn1-xGaxSe 2 (CIGS) based thin film solar cell, optical techniques such as spectroscopic reflectometry and polarimetry are advantageous because they can be set up in an unobtrusive manner in the manufacturing line, and collect data in-line and in-situ. The use of these techniques requires accurate optical models that correctly represent the properties of the layers being deposited. In this study, Spectroscopic ellipsometry (SE) has been applied for the characterization of each individual stage of CIGS layers deposited using the 3-stage co-evaporation process along with the other functional layers. Dielectric functions have been determined for the energy range from 0.7 eV to 5.1 eV. Critical-point line-shape analysis was used in this study to determine the critical point energies of the CIGS based layers. To control the compositional and thickness uniformity of all the functional layers during the fabrication of CIGS solar cells over large areas, multilayer photovoltaics (PV) stack optical models were developed with the help of extracted dielectric functions. In this study, mapping capability of RC2 spectroscopic ellipsometer was used to map all the functional layer thicknesses of a CIGS solar cell in order to probe the spatial non-uniformities that can affect the performance of a cell. The optical functions for each of the stages of CIGS 3-stage deposition process along with buffer layer and transparent conducting oxide (TCO) bi-layer, thus derived were used in a fiber optic-based spectroscopic reflectometry optical monitoring system installed in the pilot line at the PVMC's Halfmoon facility. Results obtained from this study show that the use of regular fiber optics, instead of polarization-maintaining fiber optics, is sufficient for the purpose of process monitoring. Also, the technique does not need to be used "in-situ", but the measurements can be taken in-line, and are applicable to a variety of deposition techniques used for different functional layers deposited on rigid or flexible substrates. In addition, effect of Cu concentration on the CIGS optical properties has been studied. Mixed CIGS/Cu2-xSe phase was observed at the surface at the end of the second stage of 3-stage deposition process, under Cu-rich conditions. A significant change in optical behavior of CIGS due to Cu2-xSe at the surface was observed under Cu-rich conditions, which can be used as end-point detection method to move from 2nd stage to 3rd stage in the deposition process. Developed optical functions were applied to in-line reflectance measurements not only to identify the Cu2-xSe phase at the surface but also to measure the thickness of the mixed CIGS/Cu2-xSe layer. This spectroscopic reflectometry based in-line process control technique can be used for end-point detection as well as to control thickness during the preparation of large area CIGS films. These results can assist in the development of optical process-control tools for the manufacturing of high quality CIGS based photovoltaic cells, increasing the uptime and yield of the production line. Finally, to understand the cost implications, low cost potential of two different deposition technologies has been studied on both rigid and flexible substrates with the help of cost analysis. Cost advantages of employing a contactless optics based process control technique have been investigated in order to achieve a low cost of < 0.5 $/W for CIGS module production. Based on cost analysis, one of the best strategies for achieving the low cost targets would be increasing manufacturing throughput, using roll-to-roll thin-film module manufacturing, with co-evaporation and chemical bath deposition processes for absorber and buffer layer respectively, while applying a low-cost process control technique such as spectroscopic reflectometry to improve module efficiencies and maintain high yield.

Tomographic Structural Changes of Retinal Layers after Internal Limiting Membrane Peeling for Macular Hole Surgery.

PubMed

Faria, Mun Yueh; Ferreira, Nuno P; Cristóvao, Diana M; Mano, Sofia; Sousa, David Cordeiro; Monteiro-Grillo, Manuel

2018-01-01

To highlight tomographic structural changes of retinal layers after internal limiting membrane (ILM) peeling in macular hole surgery. Nonrandomized prospective, interventional study in 38 eyes (34 patients) subjected to pars plana vitrectomy and ILM peeling for idiopathic macular hole. Retinal layers were assessed in nasal and temporal regions before and 6 months after surgery using spectral domain optical coherence tomography. Total retinal thickness increased in the nasal region and decreased in the temporal region. The retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) showed thinning on both nasal and temporal sides of the fovea. The thickness of the outer plexiform layer (OPL) increased. The outer nuclear layer (ONL) and outer retinal layers (ORL) increased in thickness after surgery in both nasal and temporal regions. ILM peeling is associated with important alterations in the inner retinal layer architecture, with thinning of the RNFL-GCL-IPL complex and thickening of OPL, ONL, and ORL. These structural alterations can help explain functional outcome and could give indications regarding the extent of ILM peeling, even though peeling seems important for higher rate of hole closure. © 2017 S. Karger AG, Basel.

Improved conductivity of indium-tin-oxide film through the introduction of intermediate layer

NASA Astrophysics Data System (ADS)

Ng, S. W.; Yam, F. K.; Beh, K. P.; Tneh, S. S.; Hassan, Z.

2016-09-01

A thin intermediate layer (Ag, AuSn, In, Ni, Sn, SiO2) was individually deposited on glass substrates prior to the deposition of indium-tin-oxide (ITO) thin film by radio-frequency (RF) magnetron sputtering employing ITO target (composition ratio of In2O3:SnO2 = 9:1). The structural, optical and electrical properties were investigated to compare the ITO thin film with and without an intermediate layer. The preferential orientation of all ITO films was along (222) plane. Although all thin films were polycrystalline, the presence of intermediate layer promoted the overall crystallinity. The sheet resistance and resistivity of the ITO film were reduced from ∼68 Ω/□ to ∼29-45 Ω/□, and 16.2 × 10-4 Ω cm up to 7.58 × 10-4 Ω cm, respectively, by inserting a thin metal layer underneath the ITO film, and it is dependent on the degree of crystallization. The optical transmittance in the visible region varies from 40 to 88% for different samples. Based on the evaluation from Tauc plot, the optical band gap falls in the range of 4.02-4.12 eV. Physical film thickness was compared with that evaluated by optical measurement in the visible range and the physical thickness was found to be smaller. Similarly, the carrier concentration/scattering time from Hall effect measurement were also compared with that from optical measurement in the infrared region. Haacke's figure of merit (FOM) was employed to assess the quality of the ITO films, and the highest FOM is credited to ITO/In up to ∼8 × 10-3 Ω-1 in the visible light region.

Photoreceptor layer map using spectral-domain optical coherence tomography.

PubMed

Lee, Ji Eun; Lim, Dae Won; Bae, Han Yong; Park, Hyun Jin

2009-12-01

To develop a novel method for analysis of the photoreceptor layer map (PLM) generated using spectral-domain optical coherence tomography (OCT). OCT scans were obtained from 20 eyes, 10 with macular holes (MH) and 10 with central serous chorioretinopathy (CSC) using the Macular Cube (512 x 128) protocol of the Cirrus HD-OCT (Carl Zeiss). The scanned data were processed using embedded tools of the advanced visualization. A partial thickness OCT fundus image of the photoreceptor layer was generated by setting the region of interest to a 50-microm thick layer that was parallel and adjacent to the retinal pigment epithelium. The resulting image depicted the photoreceptor layer as a map of the reflectivity in OCT. The PLM was compared with fundus photography, auto-fluorescence, tomography, and retinal thickness map. The signal from the photoreceptor layer of every OCT scan in each case was demonstrated as a single image of PLM in a fundus photograph fashion. In PLM images, detachment of the sensory retina is depicted as a hypo-reflective area, which represents the base of MH and serous detachment in CSC. Relative hypo-reflectivity, which was also noted at closed MH and at recently reattached retina in CSC, was associated with reduced signal from the junction between the inner and outer segments of photoreceptors in OCT images. Using PLM, changes in the area of detachment and reflectivity of the photoreceptor layer could be efficiently monitored. The photoreceptor layer can be analyzed as a map using spectral-domain OCT. In the treatment of both MH and CSC, PLM may provide new pathological information about the photoreceptor layer to expand our understanding of these diseases.

Layered Organization in the Coastal Ocean: 4-D Assessment of Thin Layer Structure, Dynamics and Impacts

DTIC Science & Technology

2009-09-30

maintenance and dissipation of layers; (2) to understand the spatial coherence and spatial properties of thin layers in the coastal ocean (especially in...ORCAS profilers at K1 South and K2 had a Nortek ADV (Acoustic Doppler Velocity meter) for simultaneously measuring centimeter- scale currents and...year will be used to (1) detect the presence, intensity, thickness, temporal persistence, and spatial coherence of thin optical and acoustical layers

Confirmation of theoretical colour predictions for layering dental composite materials.

PubMed

Mikhail, Sarah S; Johnston, William M

2014-04-01

The aim of this study is to confirm the theoretical colour predictions for single and double layers of dental composite materials on an opaque backing. Single and double layers of composite resins were fabricated, placed in optical contact with a grey backing and measured for spectral radiance. The spectral reflectance and colour were directly determined. Absorption and scattering coefficients as previously reported, the measured thickness of the single layers and the effective reflectance of the grey backing were utilized to theoretically predict the reflectance of the single layer using corrected Kubelka-Munk reflectance theory. For double layers the predicted effective reflectance of the single layer was used as the reflectance of the backing of the second layer and the thickness of the second layer was used to predict the reflectance of the double layer. Colour differences, using both the CIELAB and CIEDE2000 formulae, measured the discrepancy between each directly determined colour and its corresponding theoretical colour. The colour difference discrepancies generally ranged around the perceptibility threshold but were consistently below the respective acceptability threshold. This theory can predict the colour of layers of composite resin within acceptability limits and generally also within perceptibility limits. This theory could therefore be incorporated into computer-based optical measuring instruments that can automate the shade selections for layers of a more opaque first layer under a more translucent second layer for those clinical situations where an underlying background colour and a desirable final colour can be measured. Copyright © 2014 Elsevier Ltd. All rights reserved.

Characterization of Titan surface scenarios combining Cassini SAR images and radiometric data

NASA Astrophysics Data System (ADS)

Ventura, B.; Notarnicola, C.; Casarano, D.; Janssen, M.; Posa, F.; Cassini RADAR Science Team

2009-04-01

A great amount of data and images was provided by the radar on Cassini probe, thus opening and suggesting new scenarios about Titan's formation and evolution. An important result was the detection, among the peculiar and heterogeneous Titan's surface features, of lakes most likely constituted by liquid hydrocarbons, thus supporting the hypothesis of a methane cycle similar to water cycle on Earth.These areas, which resemble terrestrial lakes, seem to be sprinkled all over the high latitudes surrounding Titan's pole. The abundant methane in Titan's atmosphere combined with the low temperature, 94 K, lead scientists to interpret them as lakes of liquid methane or ethane. In this work, scattering models and a Bayesian inversion algorithm are applied in order to characterize lake and land surfaces. The possibility of combining the SAR data with radiometric ones on both lakes and neighboring land areas is also presented. Radar backscattering from lakes is described in terms of a double layer model, consisting of Bragg or facets scattering for the upper liquid layer and the Integral Equation Model (IEM) model for the lower solid surface. Furthermore, by means of a gravity-capillary wave model (Donelan-Pierson), the wave spectra of liquid hydrocarbons surfaces are introduced as a function of wind speed and direction. Theoretical radar backscattering coefficient values are compared with the experimental ones collected by the radar in order to estimate physical and morphological surface parameters, and to evaluate their compatibility with the expected constituents for Titan surfaces. This electromagnetic analysis is the starting point for a statistical inversion algorithm which allows determining limits on the parameters values, especially on the optical thickness and wind speed of the lakes. The physical surface parameters inferred by using the inversion algorithm are used as input for a forward radiative transfer model calculation to obtain simulated brightness temperatures. The radiometric model has been introduced to further verify the values ranges for the different parameters. In fact the same parameters derived from the radar data analysis have been used as input for the radiometric model. The comparison between the observed and computed brightness temperatures has been performed in order to address the consistency of the observations from the two instruments and to determine the coarse characteristics of the surface parameters. For both radar and radiometric data the soil medium is horizontally stratified into 2 layers. Each layer can be characterized by different absorption coefficients depending on the optical thickness, dielectric constant and physical temperature. In this algorithm, the starting point is the map of optical thickness derived from the SAR images. The simulated brightness temperature is calculated by applying the forward radiative transfer model to the optical thickness map with the same hypotheses assumed to derive it. The simulation is also carried out on the neighboring land areas by considering a double layer model including a contribution of volume scattering. Each layer is described in terms of dielectric constant values, albedo and roughness parameters with the hypothesis of water ice ammonia on layers of solid hydrocarbons and organic compounds like tholins. The analysis is applied to the areas detected on flybys 25 and 30. One important result arises from the analysis of the inverted optical thickness on deep lakes. In this case, found values of optical thickness can be considered limit values because, beyond these values, a complete attenuation can be considered. This limit value is important as it is stable even if the other parameters vary. Starting from this point, posing the condition of a complete attenuation of the second layer, i.e. fixing the value of the optical thickness, the algorithm can be used to estimate the wind speed. The retrieved values vary between 0.2 to 0.5 m/s. The first results also show a good agreement between the simulated data and the measured brightness temperature for both the liquid surface and the surrounding areas. In the last case, a good agreement is obtained only if the contribution from volume scattering is included in the model

Measurement method for the refractive index of thick solid and liquid layers.

PubMed

Santić, Branko; Gracin, Davor; Juraić, Krunoslav

2009-08-01

A simple method is proposed for the refractive index measurement of thick solid and liquid layers. In contrast to interferometric methods, no mirrors are used, and the experimental setup is undemanding and simple. The method is based on the variation of transmission caused by optical interference within the layer as a function of incidence angle. A new equation is derived for the positions of the interference extrema versus incidence angle. Scattering at the surfaces and within the sample, as well as weak absorption, do not play important roles. The method is illustrated by the refractive index measurements of sapphire, window glass, and water.

Optical Coherence Tomography (OCT) Device Independent Intraretinal Layer Segmentation

PubMed Central

Ehnes, Alexander; Wenner, Yaroslava; Friedburg, Christoph; Preising, Markus N.; Bowl, Wadim; Sekundo, Walter; zu Bexten, Erdmuthe Meyer; Stieger, Knut; Lorenz, Birgit

2014-01-01

Purpose To develop and test an algorithm to segment intraretinal layers irrespectively of the actual Optical Coherence Tomography (OCT) device used. Methods The developed algorithm is based on the graph theory optimization. The algorithm's performance was evaluated against that of three expert graders for unsigned boundary position difference and thickness measurement of a retinal layer group in 50 and 41 B-scans, respectively. Reproducibility of the algorithm was tested in 30 C-scans of 10 healthy subjects each with the Spectralis and the Stratus OCT. Comparability between different devices was evaluated in 84 C-scans (volume or radial scans) obtained from 21 healthy subjects, two scans per subject with the Spectralis OCT, and one scan per subject each with the Stratus OCT and the RTVue-100 OCT. Each C-scan was segmented and the mean thickness for each retinal layer in sections of the early treatment of diabetic retinopathy study (ETDRS) grid was measured. Results The algorithm was able to segment up to 11 intraretinal layers. Measurements with the algorithm were within the 95% confidence interval of a single grader and the difference was smaller than the interindividual difference between the expert graders themselves. The cross-device examination of ETDRS-grid related layer thicknesses highly agreed between the three OCT devices. The algorithm correctly segmented a C-scan of a patient with X-linked retinitis pigmentosa. Conclusions The segmentation software provides device-independent, reliable, and reproducible analysis of intraretinal layers, similar to what is obtained from expert graders. Translational Relevance Potential application of the software includes routine clinical practice and multicenter clinical trials. PMID:24820053

Effect of silver thickness on structural, optical and morphological properties of nanocrystalline Ag/NiO thin films

NASA Astrophysics Data System (ADS)

Jalili, S.; Hajakbari, F.; Hojabri, A.

2018-03-01

Silver (Ag) nanolayers were deposited on nickel oxide (NiO) thin films by DC magnetron sputtering. The thickness of Ag layers was in range of 20-80 nm by variation of deposition time between 10 and 40 s. X-ray diffraction results showed that the crystalline properties of the Ag/NiO films improved by increasing the Ag film thickness. Also, atomic force microscopy and field emission scanning electron microscopy images demonstrated that the surface morphology of the films was highly affected by film thickness. The film thickness and the size of particles change by elevating the Ag deposition times. The composition of films was determined by Rutherford back scattering spectroscopy. The transmission of light was gradually reduced by augmentation of Ag films thickness. Furthermore; the optical band gap of the films was also calculated from the transmittance spectra.

Process for growing a film epitaxially upon a MGO surface and structures formed with the process

DOEpatents

McKee, Rodney Allen; Walker, Frederick Joseph

1998-01-01

A process and structure wherein optical quality perovskites, such as BaTiO.sub.3 or SrTiO.sub.3, are grown upon a single crystal MgO substrate involves the epitaxial build up of alternating planes of TiO.sub.2 and metal oxide wherein the first plane grown upon the MgO substrate is a plane of TiO.sub.2. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

Ischaemia-reperfusion injury in central retinal artery occlusion.

PubMed

Saxena, Sandeep; Mishra, Nibha; Meyer, Carsten H; Akduman, Levent

2013-10-21

A 53-year-old man presented with sudden painless diminution of vision in his right eye for 3 days. His fundus examination showed diffuse whitening of the retina with a cherry red spot at the fovea with cilioretinal artery sparing. On fluorescein angiography delayed arteriovenous transit was observed. Three-dimensional spectral domain optical coherence tomography was used to assess retinal nerve fibre layer thickness and average macular central subfield thickness on days 3, 7, 30 and 90. Marked retinal oedema due to ischaemia was observed on day 3 of occurrence of central retinal artery occlusion. On day 7, significant decrease in retinal nerve fibre thickness and macular thickness was noted suggestive of acute reperfusion injury. Retinal nerve fibre layer thickness and macular thickness returned to near normal on day 30 due to restoration of blood supply with wash out of stress mediators. Retinal atrophy was observed on day 90.

Ischaemia-reperfusion injury in central retinal artery occlusion

PubMed Central

Saxena, Sandeep; Mishra, Nibha; Meyer, Carsten H; Akduman, Levent

2013-01-01

A 53-year-old man presented with sudden painless diminution of vision in his right eye for 3 days. His fundus examination showed diffuse whitening of the retina with a cherry red spot at the fovea with cilioretinal artery sparing. On fluorescein angiography delayed arteriovenous transit was observed. Three-dimensional spectral domain optical coherence tomography was used to assess retinal nerve fibre layer thickness and average macular central subfield thickness on days 3, 7, 30 and 90. Marked retinal oedema due to ischaemia was observed on day 3 of occurrence of central retinal artery occlusion. On day 7, significant decrease in retinal nerve fibre thickness and macular thickness was noted suggestive of acute reperfusion injury. Retinal nerve fibre layer thickness and macular thickness returned to near normal on day 30 due to restoration of blood supply with wash out of stress mediators. Retinal atrophy was observed on day 90. PMID:24145508

Multilayer thin-film phantoms for axial contrast transfer function measurement in optical coherence tomography.

PubMed

Agrawal, Anant; Chen, Chao-Wei; Baxi, Jigesh; Chen, Yu; Pfefer, T Joshua

2013-07-01

In optical coherence tomography (OCT), axial resolution is one of the most critical parameters impacting image quality. It is commonly measured by determining the point spread function (PSF) based on a specular surface reflection. The contrast transfer function (CTF) provides more insights into an imaging system's resolving characteristics and can be readily generated in a system-independent manner, without consideration for image pixel size. In this study, we developed a test method for determination of CTF based on multi-layer, thin-film phantoms, evaluated using spectral- and time-domain OCT platforms with different axial resolution values. Phantoms representing six spatial frequencies were fabricated and imaged. The fabrication process involved spin coating silicone films with precise thicknesses in the 8-40 μm range. Alternating layers were doped with a specified concentration of scattering particles. Validation of layer optical properties and thicknesses were achieved with spectrophotometry and stylus profilometry, respectively. OCT B-scans were used to calculate CTFs and results were compared with convetional PSF measurements based on specular reflections. Testing of these phantoms indicated that our approach can provide direct access to axial resolution characteristics highly relevant to image quality. Furthermore, tissue phantoms based on our thin-film fabrication approach may have a wide range of additional applications in optical imaging and spectroscopy.

Characteristics of peripapillary retinal nerve fiber layer in preterm children.

PubMed

Wang, Jingyun; Spencer, Rand; Leffler, Joel N; Birch, Eileen E

2012-05-01

To examine quantitatively characteristics of the peripapillary retinal nerve fiber layer (RNFL) in preterm children using Fourier-domain optical coherence tomography (FD-OCT). Prospective cross-sectional study. A 3-mm high-resolution FD-OCT peripapillary RNFL circular scan centered on the optic disc was obtained from right eyes of 25 preterm children (10.6 ± 3.7 years old, 8 preterm and 17 with regressed retinopathy of prematurity with normal-appearing posterior poles) and 54 full-term controls (9.8 ± 3.2 years old). Images were analyzed using Spectralis FD-OCT software to obtain average thickness measurements for 6 sectors (temporal superior, temporal, temporal inferior, nasal inferior, nasal, nasal superior), and the global average. The RNFL global average for preterm children was 8% thinner than for full-term controls. In the preterm group, peripapillary RNFL thickness on the temporal side of the disc was 6% thicker than in full-term controls, while all other peripapillary RNFL sectors were 9% to 13% thinner. In the preterm group, temporal sector peripapillary RNFL thickness was correlated with gestational age (r = -0.47, P < .001), with foveal center total thickness (r = 0.48, P = .008, 1-tailed), and with visual acuity (r = 0.42; P = .026, 1-tailed). The significantly thinner RNFL global average for preterm children suggests that prematurity is associated with subclinical optic nerve hypoplasia. Significant correlations between temporal sector RNFL thickness and both the foveal thickness and visual acuity suggest that the peripapillary RNFL is related to abnormalities in macular development as a result of preterm birth. Copyright © 2012 Elsevier Inc. All rights reserved.

Change of Retinal Nerve Layer Thickness in Non-Arteritic Anterior Ischemic Optic Neuropathy Revealed by Fourier Domain Optical Coherence Tomography.

PubMed

Han, Mei; Zhao, Chen; Han, Quan-Hong; Xie, Shiyong; Li, Yan

2016-08-01

To examine the changes of non-arteritic anterior ischemic optic neuropathy (NAION) by serial morphometry using Fourier domain optical coherence tomography (FD-OCT). Retrospective study in patients with newly diagnosed NAION (n=33, all unilateral) and controls (n=75 unilateral NAION patients with full contralateral eye vision) who underwent FD-OCT of the optic disk, optic nerve head (ONH), and macula within 1 week of onset and again 1, 3, 6, and 12 months later. The patients showed no improvement in vision during follow-up. Within 1 week of onset, all NAION eyes exhibited severe ONH fiber crowding and peripapillary retinal nerve fiber layer (RNFL) edema. Four had subretinal fluid accumulation and 12 had posterior vitreous detachment (PVD) at the optic disc surface. Ganglion cell complex (GCC) and RNFL thicknesses were reduced at 1 and 3 months (p < 0.05), with no deterioration thereafter. Initial RNFL/GCC contraction magnitude in the superior hemisphere correlated with the severity of inferior visual field deficits. NAION progression is characterized by an initial phase of accelerated RNFL and GCC deterioration. These results reveal that the kinetic change of neural retina in NAION and may have implication on the time window for treatment of NAION. FD-OCT is useful in the evaluation of NAION.

Asymmetry Analysis of Macular Inner Retinal Layers for Glaucoma Diagnosis: Swept-Source Optical Coherence Tomography Study

PubMed Central

Lee, Sang-Yoon; Lee, Eun Kyoung; Park, Ki Ho; Kim, Dong Myung

2016-01-01

Purpose To report an asymmetry analysis of macular inner retinal layers using swept-source optical coherence tomography (OCT) and to evaluate the utility for glaucoma diagnosis. Design Observational, cross-sectional study. Participants Seventy normal healthy subjects and 62 glaucoma patients. Methods Three-dimensional scans were acquired from 70 normal subjects and 62 open angle glaucoma patients by swept-source OCT. The thickness of the retinal nerve fiber layer, ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex, and total retina were calculated within a 6.2×6.2 mm macular area divided into a 31×31 grid of 200×200 μm superpixels. For each of the corresponding superpixels, the thickness differences between the subject eyes and contra-lateral eyes and between the upper and lower macula halves of the subject eyes were determined. The negative differences were displayed on a gray-scale asymmetry map. Black superpixels were defined as thickness decreases over the cut-off values. Results The negative inter-ocular and inter-hemisphere differences in GCIPL thickness (mean ± standard deviation) were -2.78 ± 0.97 μm and -3.43 ± 0.71 μm in the normal group and -4.26 ± 2.23 μm and -4.88 ± 1.46 μm in the glaucoma group. The overall extent of the four layers’ thickness decrease was larger in the glaucoma group than in the normal group (all Ps<0.05). The numbers of black superpixels on all of the asymmetry maps were larger in the glaucoma group than in the normal group (all Ps<0.05). The area under receiver operating characteristic curves of average negative thickness differences in macular inner layers for glaucoma diagnosis ranged from 0.748 to 0.894. Conclusions The asymmetry analysis of macular inner retinal layers showed significant differences between the normal and glaucoma groups. The diagnostic performance of the asymmetry analysis was comparable to that of previous methods. These findings suggest that the asymmetry analysis can be a potential ancillary diagnostic tool. PMID:27764166

Space Telescopes

DTIC Science & Technology

2010-01-01

of refraction for a vacuum/matter transition are often called the optical constants of the material . In the optical wavelength range, for instance...thick, can also be applied to GI mirrors, thereby extending the photon energy range out to about 100 keV. The index of refraction or the optical constants...consists of alternating layers of two materials with high contrast in the optical constants δ and β, where 1 − δ is the real part of the index of

Disordered animal multilayer reflectors and the localization of light

PubMed Central

Jordan, T. M.; Partridge, J. C.; Roberts, N. W.

2014-01-01

Multilayer optical reflectors constructed from ‘stacks’ of alternating layers of high and low refractive index dielectric materials are present in many animals. For example, stacks of guanine crystals with cytoplasm gaps occur within the skin and scales of fish, and stacks of protein platelets with cytoplasm gaps occur within the iridophores of cephalopods. Common to all these animal multilayer reflectors are different degrees of random variation in the thicknesses of the individual layers in the stack, ranging from highly periodic structures to strongly disordered systems. However, previous discussions of the optical effects of such thickness disorder have been made without quantitative reference to the propagation of light within the reflector. Here, we demonstrate that Anderson localization provides a general theoretical framework to explain the common coherent interference and optical properties of these biological reflectors. Firstly, we illustrate how the localization length enables the spectral properties of the reflections from more weakly disordered ‘coloured’ and more strongly disordered ‘silvery’ reflectors to be explained by the same physical process. Secondly, we show how the polarization properties of reflection can be controlled within guanine–cytoplasm reflectors, with an interplay of birefringence and thickness disorder explaining the origin of broadband polarization-insensitive reflectivity. PMID:25339688

Applications of optical coherence tomography in the non-contact assessment of automotive paints

NASA Astrophysics Data System (ADS)

Lawman, Samuel; Zhang, Jinke; Williams, Bryan M.; Zheng, Yalin; Shen, Yao-Chun

2017-06-01

The multiple layer paint systems on modern cars serve two end purposes, they firstly protect against corrosion and secondly give the desired visual appearance. To ensure consistent corrosion protection and appearance, suitable Quality Assurance (QA) measures on the final product are required. Various (layer thickness and consistency, layer composition, flake statistics, surface profile and layer dryness) parameters are of importance, each with specific techniques that can measure one or some of them but no technique that can measure all or most of them. Optical Coherence Tomography (OCT) is a 3D imaging technique with micrometre resolution. Since 2016, OCT measurements of layer thickness and consistency, layer composition fingerprint and flake statistics have been reported. In this paper we demonstrate two more novel applications of OCT to automotive paints. Firstly, we use OCT to quantify unwanted surface texture, which leads to an "orange peel" visual defect. This was done by measuring the surface profiles of automotive paints, with an unoptimised precision of 37 nm over lateral range of 7 mm, to quantify texture of less than 500 nm. Secondly, we demonstrate that OCT can measure how dry a coating layer is by measuring how fast it is still shrinking quasiinstantaneously, using Fourier phase sensitivity.

Investigation of alterations in multifractality in optical coherence tomographic images of in vivo human retina

NASA Astrophysics Data System (ADS)

Das, Nandan Kumar; Mukhopadhyay, Sabyasachi; Ghosh, Nirmalya; Chhablani, Jay; Richhariya, Ashutosh; Divakar Rao, Kompalli; Sahoo, Naba Kishore

2016-09-01

Optical coherence tomography (OCT) enables us to monitor alterations in the thickness of the retinal layer as disease progresses in the human retina. However, subtle morphological changes in the retinal layers due to early disease progression often may not lead to detectable alterations in the thickness. OCT images encode depth-dependent backscattered intensity distribution arising due to the depth distributions of the refractive index from tissue microstructures. Here, such depth-resolved refractive index variations of different retinal layers were analyzed using multifractal detrended fluctuation analysis, a special class of multiresolution analysis tools. The analysis extracted and quantified microstructural multifractal information encoded in normal as well as diseased human retinal OCT images acquired in vivo. Interestingly, different layers of the retina exhibited different degrees of multifractality in a particular retina, and the individual layers displayed consistent multifractal trends in healthy retinas of different human subjects. In the retinal layers of diabetic macular edema (DME) subjects, the change in multifractality manifested prominently near the boundary of the DME as compared to the normal retinal layers. The demonstrated ability to quantify depth-resolved information on multifractality encoded in OCT images appears promising for the early diagnosis of diseases of the human eye, which may also prove useful for detecting other types of tissue abnormalities from OCT images.

Reproducibility of retinal nerve fiber layer thickness measures using eye tracking in children with nonglaucomatous optic neuropathy.

PubMed

Rajjoub, Raneem D; Trimboli-Heidler, Carmelina; Packer, Roger J; Avery, Robert A

2015-01-01

To determine the intra- and intervisit reproducibility of circumpapillary retinal nerve fiber layer (RNFL) thickness measures using eye tracking-assisted spectral-domain optical coherence tomography (SD OCT) in children with nonglaucomatous optic neuropathy. Prospective longitudinal study. Circumpapillary RNFL thickness measures were acquired with SD OCT using the eye-tracking feature at 2 separate study visits. Children with normal and abnormal vision (visual acuity ≥ 0.2 logMAR above normal and/or visual field loss) who demonstrated clinical and radiographic stability were enrolled. Intra- and intervisit reproducibility was calculated for the global average and 9 anatomic sectors by calculating the coefficient of variation and intraclass correlation coefficient. Forty-two subjects (median age 8.6 years, range 3.9-18.2 years) met inclusion criteria and contributed 62 study eyes. Both the abnormal and normal vision cohort demonstrated the lowest intravisit coefficient of variation for the global RNFL thickness. Intervisit reproducibility remained good for those with normal and abnormal vision, although small but statistically significant increases in the coefficient of variation were observed for multiple anatomic sectors in both cohorts. The magnitude of visual acuity loss was significantly associated with the global (ß = 0.026, P < .01) and temporal sector coefficient of variation (ß = 0.099, P < .01). SD OCT with eye tracking demonstrates highly reproducible RNFL thickness measures. Subjects with vision loss demonstrate greater intra- and intervisit variability than those with normal vision. Copyright © 2015 Elsevier Inc. All rights reserved.

Boundary layers in cataclysmic variables: The HEAO-1 X-ray constraints

NASA Technical Reports Server (NTRS)

Jensen, K. A.

1983-01-01

The predictions of the boundary layer model for the X-ray emission from novae are summarized. A discrepancy between observations and theory in the X-ray observations is found. Constraints on the nature of the boundary layers in novae, based on the lack of detections of novae in the HEAO-1 soft X-ray survey are provided. Temperature and column densities for optically thick boundary layers in novae are estimated.

Monitoring the layer-by-layer self-assembly of graphene and graphene oxide by spectroscopic ellipsometry.

PubMed

Zhou, Kai-Ge; Chang, Meng-Jie; Wang, Hang-Xing; Xie, Yu-Long; Zhang, Hao-Li

2012-01-01

Thin films of graphene oxide, graphene and copper (II) phthalocyanine dye have been successfully fabricated by electrostatic layer-by-layer (LbL) assembly approach. We present the first variable angle spectroscopic ellipsometry (VASE) investigation on these graphene-dye hybrid thin films. The thickness evaluation suggested that our LbL assembly process produces highly uniform and reproducible thin films. We demonstrate that the refractive indices of the graphene-dye thin films undergo dramatic variation in the range close to the absorption of the dyes. This investigation provides new insight to the optical properties of graphene containing thin films and shall help to establish an appropriate optical model for graphene-based hybrid materials.

Two-photon absorption in layered transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Dong, Ningning; Zhang, Saifeng; Li, Yuanxin; Wang, Jun

2018-02-01

Two-dimensional (2D) layered transition metal dichalcogenides (TMDCs) exhibit unique nonlinear optical (NLO) features and have becoming intriguing and promising candidate materials for photonic and optoelectronic devices with high performance and unique functions. Owing to layered geometry and the thickness-dependent bandgap, we studied the ultrafast NLO properties of a range of TMDCs. TMDCs with high-quality layered nanosheets were prepared through chemical vapor deposition (CVD) technique and vapor-phase growth method. Saturable absorption, two photon absorption (TPA) and two photon pumped frequency up-converted luminescence were observed from these 2D nanostructures. The exciting results open up the door to 2D photonic devices, such as passive mode-lockers, Q-switchers, optical limiters, light emitters, etc.

Optical Coherence Tomography Scan Circle Location and Mean Retinal Nerve Fiber Layer Measurement Variability

PubMed Central

Gabriele, Michelle L.; Ishikawa, Hiroshi; Wollstein, Gadi; Bilonick, Richard A.; Townsend, Kelly A.; Kagemann, Larry; Wojtkowski, Maciej; Srinivasan, Vivek J.; Fujimoto, James G.; Duker, Jay S.; Schuman, Joel S.

2009-01-01

PURPOSE To investigate the effect on optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurements of varying the standard 3.4-mm-diameter circle location. METHODS The optic nerve head (ONH) region of 17 eyes of 17 healthy subjects was imaged with high-speed, ultrahigh-resolution OCT (hsUHR-OCT; 501 × 180 axial scans covering a 6 × 6-mm area; scan time, 3.84 seconds) for a comprehensive sampling. This method allows for systematic simulation of the variable circle placement effect. RNFL thickness was measured on this three-dimensional dataset by using a custom-designed software program. RNFL thickness was resampled along a 3.4-mm-diameter circle centered on the ONH, then along 3.4-mm circles shifted horizontally (x-shift), vertically (y-shift) and diagonally up to ±500 µm (at 100-µm intervals). Linear mixed-effects models were used to determine RNFL thickness as a function of the scan circle shift. A model for the distance between the two thickest measurements along the RNFL thickness circular profile (peak distance) was also calculated. RESULTS RNFL thickness tended to decrease with both positive and negative x- and y-shifts. The range of shifts that caused a decrease greater than the variability inherent to the commercial device was greater in both nasal and temporal quadrants than in the superior and inferior ones. The model for peak distance demonstrated that as the scan moves nasally, the RNFL peak distance increases, and as the circle moves temporally, the distance decreases. Vertical shifts had a minimal effect on peak distance. CONCLUSIONS The location of the OCT scan circle affects RNFL thickness measurements. Accurate registration of OCT scans is essential for measurement reproducibility and longitudinal examination (ClinicalTrials.gov number, NCT00286637). PMID:18515577

Dielectric function of InGaAs in the visible

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Sieg, R. E.; Yao, H. D.; Snyder, P. G.; Woollam, J. A.; Pamulapati, J.; Bhattacharya, P. K.; Sekula-Moise, P. A.

1990-01-01

Measurements are reported of the dielectric function of thermodynamically stable In(x)Ga(1-x)As in the composition range 0.3 equal to or less than X = to or less than 0.7. The optically thick samples of InGaAs were made by molecular beam epitaxy (MBE) in the range 0.4 = to or less than X = to or less than 0.7 and by metal-organic chemical vapor deposition (MOCVD) for X = 0.3. The MBE made samples, usually 1 micron thick, were grown on semi-insulating InP and included a strain release structure. The MOCVD sample was grown on GaAs and was 2 microns thick. The dielectric functions were measured by variable angle spectroscopic ellipsometry in the range 1.55 to 4.4 eV. The data was analyzed assuming an optically thick InGaAs material with an oxide layer on top. The thickness of this layer was estimated by comparing the results for the InP lattice matched material, i.e., X = 0.53, with results published in the literature. The top oxide layer mathematically for X = 0.3 and X = 0.53 was removed to get the dielectric function of the bare InGaAs. In addition, the dielectric function of GaAs in vacuum, after a protective arsenic layer was removed. The dielectric functions for X = 0, 0.3, and 0.53 together with the X = 1 result from the literature to evaluate an algorithm for calculating the dielectric function of InGaAs for an arbitrary value of X(0 = to or less than X = to or less than 1) were used. Results of the dielectric function calculated using the algorithm were compared with experimental data.

Dielectric function of InGaAs in the visible

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Yao, H. D.; Snyder, P. G.; Woolam, J. A.; Pamulapati, J.; Bhattacharya, P. K.; Sekula-Moise, P. A.; Sieg, R. E.

1990-01-01

Measurements are reported of the dielectric function of thermodynamically stable In(x)Ga(1-x)As in the composition range 0.3 equal to or less than X = to or less than 0.7. The optically thick samples of InGaAs were made by molecular beam epitaxy (MBE) in the range 0.4 = to or less than X = to or less than 0.7 and by metal-organic chemical vapor deposition (MOCVD) for X = 0.3. The MBE made samples, usually 1 micron thick, were grown on semi-insulating InP and included a strain release structure. The MOCVD sample was grown on GaAs and was 2 microns thick. The dielectric functions were measured by variable angle spectroscopic ellipsometry in the range 1.55 to 4.4 eV. The data was analyzed assuming an optically thick InGaAs material with an oxide layer on top. The thickness of this layer was estimated by comparing the results for the InP lattice matched material, i.e., X = 0.53, with results published in the literature. The top oxide layer mathematically for X = 0.3 and X = 0.53 was removed to get the dielectric function of the bare InGaAs. In addition, the dielectric function of GaAs in vacuum, after a protective arsenic layer was removed. The dielectric functions for X = 0, 0.3, and 0.53 together with the X = 1 result from the literature to evaluate an algorithm for calculating the dielectric function of InGaAs for an arbitrary value of X (0 = to or less than X = to or less than 1) were used. Results of the dielectric function calculated using the algorithm were compared with experimental data.

Numerical modelling of high efficiency InAs/GaAs intermediate band solar cell

NASA Astrophysics Data System (ADS)

Imran, Ali; Jiang, Jianliang; Eric, Debora; Yousaf, Muhammad

2018-01-01

Quantum Dots (QDs) intermediate band solar cells (IBSC) are the most attractive candidates for the next generation of photovoltaic applications. In this paper, theoretical model of InAs/GaAs device has been proposed, where we have calculated the effect of variation in the thickness of intrinsic and IB layer on the efficiency of the solar cell using detailed balance theory. IB energies has been optimized for different IB layers thickness. Maximum efficiency 46.6% is calculated for IB material under maximum optical concentration.

Coincident Above- and Below-ground Autonomous Monitoring to Quantify Co-variability in Permafrost, Soil and Vegetation Properties in Arctic Tundra: Supporting Data

DOE Data Explorer

Baptiste Dafflon; Rusen Oktem; John Peterson; Craig Ulrich; Anh Phuong Tran; Vladimir Romanovsky; Susan Hubbard

2017-05-10

The dataset contains measurements obtained through electrical resistivity tomography (ERT) to monitor soil properties, pole-mounted optical cameras to monitor vegetation dynamics, point probes to measure soil temperature, and periodic manual measurements of thaw layer thickness, snow thickness and soil dielectric permittivity.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, B.L.

1999-04-27

A semiconductor device is described having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer. 9 figs.

Strained-layer epitaxy of germanium-silicon alloys

NASA Astrophysics Data System (ADS)

Bean, J. C.

1985-10-01

Strained-layer epitaxy is presented as a developing technique for combining Si with other materials in order to obtain semiconductors with enhanced electronic properties. The method involves applying layers sufficiently thin so that the atoms deposited match the bonding configurations of the substrate crystal. When deposited on Si, a four-fold bonding pattern is retained, with a lowered interfacial energy and augmented stored strain energy in the epitaxial layer. The main problem which remains is building an epitaxial layer thick enough to yield desired epitaxial properties while avoiding a reversion to an unstrained structure. The application of a Ge layer to Si using MBE is described, along with the formation of heterojunction multi-layer superlattices, which can reduce the dislocation effects in some homojunctions. The technique shows promise for developing materials of use as bipolar transistors, optical detectors and fiber optic transmission devices.

Inferring regional vertical crustal velocities from averaged relative sea level trends: A proof of concept

NASA Astrophysics Data System (ADS)

Bâki Iz, H.; Shum, C. K.; Zhang, C.; Kuo, C. Y.

2017-11-01

We report the design of a high-throughput gradient hyperbolic lenslet built with real-life materials and capable of focusing a beam into a deep sub-wavelength spot of λ/23. This efficient design is achieved through high-order transformation optics and circular effective-medium theory (CEMT), which are used to engineer the radially varying anisotropic artificial material based on the thin alternating cylindrical metal and dielectric layers. The radial gradient of the effective anisotropic optical constants allows for matching the impedances at the input and output interfaces, drastically improving the throughput of the lenslet. However, it is the use of the zeroth-order CEMT that enables the practical realization of a gradient hyperlens with realistic materials. To illustrate the importance of using the CEMT versus the conventional planar effective-medium theory (PEMT) for cylindrical anisotropic systems, such as our hyperlens, both the CEMT and PEMT are adopted to design gradient hyperlenses with the same materials and order of elemental layers. The CEMT- and PEMT-based designs show similar performance if the number of metal-dielectric binary layers is sufficiently large (9+ pairs) and if the layers are sufficiently thin. However, for the manufacturable lenses with realistic numbers of layers (e.g. five pairs) and thicknesses, the performance of the CEMT design continues to be practical, whereas the PEMT-based design stops working altogether. The accurate design of transformation optics-based layered cylindrical devices enabled by CEMT allow for a new class of robustly manufacturable nanophotonic systems, even with relatively thick layers of real-life materials.

Enhanced sensitivity to dielectric function and thickness of absorbing thin films by combining total internal reflection ellipsometry with standard ellipsometry and reflectometry

NASA Astrophysics Data System (ADS)

Lizana, A.; Foldyna, M.; Stchakovsky, M.; Georges, B.; Nicolas, D.; Garcia-Caurel, E.

2013-03-01

High sensitivity of spectroscopic ellipsometry and reflectometry for the characterization of thin films can strongly decrease when layers, typically metals, absorb a significant fraction of the light. In this paper, we propose a solution to overcome this drawback using total internal reflection ellipsometry (TIRE) and exciting a surface longitudinal wave: a plasmon-polariton. As in the attenuated total reflectance technique, TIRE exploits a minimum in the intensity of reflected transversal magnetic (TM) polarized light and enhances the sensitivity of standard methods to thicknesses of absorbing films. Samples under study were stacks of three films, ZnO : Al/Ag/ZnO : Al, deposited on glass substrates. The thickness of the silver layer varied from sample to sample. We performed measurements with a UV-visible phase-modulated ellipsometer, an IR Mueller ellipsometer and a UV-NIR reflectometer. We used the variance-covariance formalism to evaluate the sensitivity of the ellipsometric data to different parameters of the optical model. Results have shown that using TIRE doubled the sensitivity to the silver layer thickness when compared with the standard ellipsometry. Moreover, the thickness of the ZnO : Al layer below the silver layer can be reliably quantified, unlike for the fit of the standard ellipsometry data, which is limited by the absorption of the silver layer.

Engineering optical properties of gold-coated nanoporous anodic alumina for biosensing

NASA Astrophysics Data System (ADS)

Hernández-Eguía, Laura P.; Ferré-Borrull, Josep; Macias, Gerard; Pallarès, Josep; Marsal, Lluís F.

2014-08-01

The effect in the Fabry-Pérot optical interferences of nanoporous anodic alumina films coated with gold is studied as a function of the porosity and of the gold thickness by means of reflectance spectroscopy. Samples with porosities between 14 and 70% and gold thicknesses (10 and 20 nm) were considered. The sputtering of gold on the nanoporous anodic alumina (NAA) films results in an increase of the fringe intensity of the oscillations in the spectra resulting from Fabry-Pérot interferences in the porous layer, with a reduction in the maximum reflectance in the UV-visible region. For the thicker gold layer, sharp valleys appear in the near-infrared (IR) range that can be useful for accurate spectral shift measurements in optical biosensing. A theoretical model for the optical behavior has also been proposed. The model shows a very good agreement with the experimental measurements, what makes it useful for design and optimization of devices based on this material. This material capability is enormous for using it as an accurate and sensitive optical sensor, since gold owns a well-known surface chemistry with certain molecules, most of them biomolecules.

Microelectromechanical system pressure sensor integrated onto optical fiber by anodic bonding.

PubMed

Saran, Anish; Abeysinghe, Don C; Boyd, Joseph T

2006-03-10

Optical microelectromechanical system pressure sensors based on the principle of Fabry-Perot interferometry have been developed and fabricated using the technique of silicon-to-silicon anodic bonding. The pressure sensor is then integrated onto an optical fiber by a novel technique of anodic bonding without use of any adhesives. In this anodic bonding technique we use ultrathin silicon of thickness 10 microm to bond the optical fiber to the sensor head. The ultrathin silicon plays the role of a stress-reducing layer, which helps the bonding of an optical fiber to silicon having conventional wafer thickness. The pressure-sensing membrane is formed by 8 microm thick ultrathin silicon acting as a membrane, thus eliminating the need for bulk silicon etching. The pressure sensor integrated onto an optical fiber is tested for static response, and experimental results indicate degradation in the fringe visibility of the Fabry-Perot interferometer. This effect was mainly due to divergent light rays from the fiber degrading the fringe visibility. This effect is demonstrated in brief by an analytical model.

Human Chorioretinal Layer Thicknesses Measured in Macula-wide, High-Resolution Histologic Sections

PubMed Central

Messinger, Jeffrey D.; Sloan, Kenneth R.; Mitra, Arnab; McGwin, Gerald; Spaide, Richard F.

2011-01-01

Purpose. To provide a comprehensive description of chorioretinal layer thicknesses in the normal human macula, including two-layer pairs that can produce a combined signal in some optical coherence tomography (OCT) devices (ganglion cell [GCL] and inner plexiform [IPL] layers and outer plexiform [OPL] and outer nuclear [ONL] layers). Methods. In 0.8-μm-thick, macula-wide sections through the foveola of 18 donors (age range, 40–92 years), 21 layers were measured at 25 locations by a trained observer and validated by a second observer. Tissue volume changes were assessed by comparing total retinal thickness in ex vivo OCT and in sections. Results. Median tissue shrinkage was 14.5% overall and 29% in the fovea. Histologic laminar boundaries resembled those in SD-OCT scans, but the shapes of the foveolar OPL and ONL differed. Histologic GCL, IPL, and OPLHenle were thickest at 0.8. to 1, 1.5, and 0.4 mm eccentricity, respectively. ONL was thickest in an inward bulge at the foveal center. At 1 mm eccentricity, GCL, INL, and OPLHenle represented 17.3% to 21.1%, 18.0% to 18.5%, and 14.2% to 16.6% of total retinal thickness, respectively. In donors ≥70 years of age, the RPE and choroid were 17.1% and 29.6% thinner and OPLHenle was 20.8% thicker than in donors <70 years. Conclusions. In this study, the first graphic representation and thickness database of chorioretinal layers in normal macula were generated. Newer OCT systems can separate GCL from IPL and OPLHenle from ONL, with good agreement for the proportion of retinal thickness occupied by OPLHenle in OCT and histology. The thickening of OPLHenle in older eyes may reflect Müller cell hypertrophy associated with rod loss. PMID:21421869

MULTIPLICITY OF NOVA ENVELOPE SOLUTIONS AND OCCURRENCE OF OPTICALLY THICK WINDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kato, Mariko; Hachisu, Izumi

2009-07-10

We revisit the occurrence condition of optically thick winds reported by Kato in 1985 and Kato and Hachisu in 1989 who mathematically examined nova envelope solutions with an old opacity and found that optically thick winds are accelerated only in massive white dwarfs (WDs) of {approx}>0.9 M{sub sun}. With the OPAL opacity we find that the optically thick wind occurs for {approx}>0.6 M{sub sun} WDs and that the occurrence of winds depends not only on the WD mass but also on the ignition mass. When the ignition mass is larger than a critical value, winds are suppressed by a density-inversionmore » layer. Such a static solution can be realized in WDs of mass {approx}0.6-0.7 M{sub sun}. We propose that sequences consisting only of static solutions correspond to slow evolutions in symbiotic novae like PU Vul because PU Vul shows no indication of strong winds in a long-lasted flat peak followed by a very slow decline in its light curve.« less

Simplified design of thin-film polarizing beam splitter using embedded symmetric trilayer stack.

PubMed

Azzam, R M A

2011-07-01

An analytically tractable design procedure is presented for a polarizing beam splitter (PBS) that uses frustrated total internal reflection and optical tunneling by a symmetric LHL trilayer thin-film stack embedded in a high-index prism. Considerable simplification arises when the refractive index of the high-index center layer H matches the refractive index of the prism and its thickness is quarter-wave. This leads to a cube design in which zero reflection for the p polarization is achieved at a 45° angle of incidence independent of the thicknesses of the identical symmetric low-index tunnel layers L and L. Arbitrarily high reflectance for the s polarization is obtained at subwavelength thicknesses of the tunnel layers. This is illustrated by an IR Si-cube PBS that uses an embedded ZnS-Si-ZnS trilayer stack.

Wafer-scale synthesis of monolayer and few-layer MoS2 via thermal vapor sulfurization

NASA Astrophysics Data System (ADS)

Robertson, John; Liu, Xue; Yue, Chunlei; Escarra, Matthew; Wei, Jiang

2017-12-01

Monolayer molybdenum disulfide (MoS2) is an atomically thin, direct bandgap semiconductor crystal potentially capable of miniaturizing optoelectronic devices to an atomic scale. However, the development of 2D MoS2-based optoelectronic devices depends upon the existence of a high optical quality and large-area monolayer MoS2 synthesis technique. To address this need, we present a thermal vapor sulfurization (TVS) technique that uses powder MoS2 as a sulfur vapor source. The technique reduces and stabilizes the flow of sulfur vapor, enabling monolayer wafer-scale MoS2 growth. MoS2 thickness is also controlled with great precision; we demonstrate the ability to synthesize MoS2 sheets between 1 and 4 layers thick, while also showing the ability to create films with average thickness intermediate between integer layer numbers. The films exhibit wafer-scale coverage and uniformity, with electrical quality varying depending on the final thickness of the grown MoS2. The direct bandgap of grown monolayer MoS2 is analyzed using internal and external photoluminescence quantum efficiency. The photoluminescence quantum efficiency is shown to be competitive with untreated exfoliated MoS2 monolayer crystals. The ability to consistently grow wafer-scale monolayer MoS2 with high optical quality makes this technique a valuable tool for the development of 2D optoelectronic devices such as photovoltaics, detectors, and light emitters.

Enhanced photovoltaic property by forming p-i-n structures containing Si quantum dots/SiC multilayers

PubMed Central

2014-01-01

Si quantum dots (Si QDs)/SiC multilayers were fabricated by annealing hydrogenated amorphous Si/SiC multilayers prepared in a plasma-enhanced chemical vapor deposition system. The thickness of amorphous Si layer was designed to be 4 nm, and the thickness of amorphous SiC layer was kept at 2 nm. Transmission electron microscopy observation revealed the formation of Si QDs after 900°C annealing. The optical properties of the Si QDs/SiC multilayers were studied, and the optical band gap deduced from the optical absorption coefficient result is 1.48 eV. Moreover, the p-i-n structure with n-a-Si/i-(Si QDs/SiC multilayers)/p-Si was fabricated, and the carrier transportation mechanism was investigated. The p-i-n structure was used in a solar cell device. The cell had the open circuit voltage of 532 mV and the power conversion efficiency (PCE) of 6.28%. PACS 81.07.Ta; 78.67.Pt; 88.40.jj PMID:25489285

Coordinated Airborne, Spaceborne, and Ground-Based Measurements of Massive, Thick Aerosol Layers During the Dry Season in Southern Africa

NASA Technical Reports Server (NTRS)

Schmid, B.; Redemann, J.; Russell, P. B.; Hobbs, P. V.; Hlavka, D. L.; McGill, M. J.; Holben, B. N.; Welton, E. J.; Campbell, J.; Torres, O.;

Effect of temperature rise and hydrostatic pressure on microbending loss and refractive index change in double-coated optical fiber

NASA Astrophysics Data System (ADS)

Seraji, Faramarz E.; Toutian, Golnoosh

This paper presents an analysis of the effect of temperature rise and hydrostatic pressure on microbending loss, refractive index change, and stress components of a double-coated optical fiber by considering coating material parameters such as Young's modulus and the Poisson ratio. It is shown that, when temperature rises, the microbending loss and refractive index changes would decrease with increase of thickness of primary coating layer and will increase after passing through a minima. Increase of thickness of secondary coating layer causes the microbending loss and refractive index changes to decrease. We have shown that the temperature rise affecting the fiber makes the microbending loss and refractive index decrease, linearly. At a particular temperature, the microbending loss takes negative values, due to tensile pressure applied on the fiber. The increase of Young's modulus and the Poisson ratio of primary coating would lower the microbending loss and refractive index change whereas in the secondary coating layer, the condition reverses.

Effect of spacer layer thickness on structural and optical properties of multi-stack InAs/GaAsSb quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Yeongho; Ban, Keun-Yong, E-mail: kban1@asu.edu; Honsberg, Christiana B.

2015-10-26

The structural and optical properties of ten-stack InAs/GaAsSb quantum dots (QDs) with different spacer layer thicknesses (d{sub s} = 2, 5, 10, and 15 nm) are reported. X-ray diffraction analysis reveals that the strain relaxation of the GaAsSb spacers increases linearly from 0% to 67% with larger d{sub s} due to higher elastic stress between the spacer and GaAs matrix. In addition, the dislocation density in the spacers with d{sub s} = 10 nm is lowest as a result of reduced residual strain. The photoluminescence peak energy from the QDs does not change monotonically with increasing d{sub s} due to the competing effects of decreased compressivemore » strain and weak electronic coupling of stacked QD layers. The QD structure with d{sub s} = 10 nm is demonstrated to have improved luminescence properties and higher carrier thermal stability.« less

Optical coherence tomography for nondestructive evaluation of fuel rod degradation

NASA Astrophysics Data System (ADS)

Renshaw, Jeremy B.; Jenkins, Thomas P.; Buckner, Benjamin D.; Friend, Brian

2015-03-01

Nuclear power plants regularly inspect fuel rods to ensure safe and reliable operation. Excessive corrosion can cause fuel failures which can have significant repercussions for the plant, including impacts on plant operation, worker exposure to radiation, and the plant's INPO rating. While plants typically inspect for fuel rod corrosion using eddy current techniques, these techniques have known issues with reliability in the presence of tenacious, ferromagnetic crud layers that can deposit during operation, and the nondestructive evaluation (NDE) inspection results can often be in error by a factor of 2 or 3. For this reason, alternative measurement techniques, such as Optical Coherence Tomography (OCT), have been evaluated that are not sensitive to the ferromagnetic nature of the crud. This paper demonstrates that OCT has significant potential to characterize the thickness of crud layers that can deposit on the surfaces of fuel rods during operation. Physical trials have been performed on simulated crud samples, and the resulting data show an apparent correlation between the crud layer thickness and the OCT signal.

Enhanced Visible Transmittance of Thermochromic VO2 Thin Films by SiO2 Passivation Layer and Their Optical Characterization

PubMed Central

Yu, Jung-Hoon; Nam, Sang-Hun; Lee, Ji Won; Boo, Jin-Hyo

2016-01-01

This paper presents the preparation of high-quality vanadium dioxide (VO2) thermochromic thin films with enhanced visible transmittance (Tvis) via radio frequency (RF) sputtering and plasma enhanced chemical vapor deposition (PECVD). VO2 thin films with high Tvis and excellent optical switching efficiency (Eos) were successfully prepared by employing SiO2 as a passivation layer. After SiO2 deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO2 coating, the phase transition temperature (Tc) of the prepared films was not affected. Compared with pristine VO2, the total layer thickness after SiO2 coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO2 thin films showed a higher Tvis value (λ 650 nm, 58%) compared with the pristine samples (λ 650 nm, 43%). This enhancement of Tvis while maintaining high Eos is meaningful for VO2-based smart window applications. PMID:28773679

Drop impact on liquid film: dynamics of interfacial gas layer

NASA Astrophysics Data System (ADS)

Tang, Xiaoyu; Saha, Abhishek; Law, Chung K.; Sun, Chao

2016-11-01

Drop impacting liquid film is commonly observed in many processes including inkjet printing and thermal sprays. Owing to the resistance from the interfacial gas layer trapped between the drop and film surface, impact may not always result in coalescence; and as such investigating the behavior of the interfacial gas layer is important to understand the transition between bouncing and merging outcomes. The gas layer is, however, not easily optically accessible due to its microscopic scale and curved interfaces. We report the measurement of this critical gas layer thickness between two liquid surfaces using high-speed color interferometry capable of measuring micron and submicron thicknesses. The complete gas layer dynamics for the bouncing cases can be divided into two stages: the approaching stage when the drop squeezes the gas layer at the beginning of the impact, and the rebounding stage when the drop retracts and rebounds from the liquid film. The approaching stage is found to be similar across wide range of conditions studied. However, for the rebounding stage, with increase of liquid film thickness, the evolution of gas layer changes dramatically, displaying a non-monotonic behavior. Such dynamics is analyzed in lights of various competing timescales.

Quantitative, depth-resolved determination of particle motion using multi-exposure, spatial frequency domain laser speckle imaging.

PubMed

Rice, Tyler B; Kwan, Elliott; Hayakawa, Carole K; Durkin, Anthony J; Choi, Bernard; Tromberg, Bruce J

2013-01-01

Laser Speckle Imaging (LSI) is a simple, noninvasive technique for rapid imaging of particle motion in scattering media such as biological tissue. LSI is generally used to derive a qualitative index of relative blood flow due to unknown impact from several variables that affect speckle contrast. These variables may include optical absorption and scattering coefficients, multi-layer dynamics including static, non-ergodic regions, and systematic effects such as laser coherence length. In order to account for these effects and move toward quantitative, depth-resolved LSI, we have developed a method that combines Monte Carlo modeling, multi-exposure speckle imaging (MESI), spatial frequency domain imaging (SFDI), and careful instrument calibration. Monte Carlo models were used to generate total and layer-specific fractional momentum transfer distributions. This information was used to predict speckle contrast as a function of exposure time, spatial frequency, layer thickness, and layer dynamics. To verify with experimental data, controlled phantom experiments with characteristic tissue optical properties were performed using a structured light speckle imaging system. Three main geometries were explored: 1) diffusive dynamic layer beneath a static layer, 2) static layer beneath a diffuse dynamic layer, and 3) directed flow (tube) submerged in a dynamic scattering layer. Data fits were performed using the Monte Carlo model, which accurately reconstructed the type of particle flow (diffusive or directed) in each layer, the layer thickness, and absolute flow speeds to within 15% or better.

Photovoltaic driven multiple quantum well optical modulator

NASA Technical Reports Server (NTRS)

Maserjian, Joseph (Inventor)

1990-01-01

Multiple quantum well (MQW) structures (12) are utilized to provide real-time, reliable, high-performance, optically-addressed spatial-light modulators (SLM) (10). The optically-addressed SLM comprises a vertical stack of quantum well layers (12a) within the penetration depth of an optical write signal 18, a plurality of space charge barriers (12b) having predetermined tunneling times by control of doping and thickness. The material comprising the quantum well layers has a lower bandgap than that of the space charge barrier layers. The write signal modulates a read signal (20). The modulation sensitivity of the device is high and no external voltage source is required. In a preferred embodiment, the SLM having interleaved doped semiconductor layers for driving the MQW photovoltaically is characterized by the use of a shift analogous to the Moss-Burnstein shift caused by the filling of two-dimensional states in the multiple quantum wells, thus allowing high modulation sensitivity in very narrow wells. Arrays (30) may be formed with a plurality of the modulators.

Self-propagated combustion synthesis of few-layered graphene: an optical properties perspective.

PubMed

Mohandoss, Manonmani; Sen Gupta, Soujit; Kumar, Ramesh; Islam, Md Rabiul; Som, Anirban; Mohd, Azhardin Ganayee; Pradeep, T; Maliyekkal, Shihabudheen M

2018-04-26

This paper describes a labour efficient and cost-effective strategy to prepare few-layered of reduced graphene oxide like (RGOL) sheets from graphite. The self-propagated combustion route enables the bulk production of RGOL sheets. Microscopic and spectroscopic analyses confirmed the formation of few-layer graphene sheets of an average thickness of ∼3 nm and the presence of some oxygen functional groups with a C/O ratio of 8.74. A possible mechanistic pathway for the formation of RGOL sheets is proposed. The optical properties of the RGOL sample were studied in detail by means of Spectroscopic Ellipsometry (SE). The experimental abilities of SE in relating the optical properties with the number of oxygen functionalities present in the samples are explored. The data were analysed by a double-layered optical model along with the Drude-Lorentz oscillatory dispersion relation. The refractive index (n = 2.24), extinction coefficient (k = 2.03), and dielectric functions are obtained using point-by-point analysis and are also checked for Kramers-Kronig (KK) consistency.

Active polymer materials for optical fiber CO2 sensors

NASA Astrophysics Data System (ADS)

Wysokiński, Karol; Filipowicz, Marta; Stańczyk, Tomasz; Lipiński, Stanisław; Napierała, Marek; Murawski, Michał; Nasiłowski, Tomasz

2017-04-01

CO2 optical fiber sensors based on polymer active materials are presented in this paper. Ethyl cellulose was proven to be a good candidate for a matrix material of the sensor, since it gives porous, thick and very sensitive layers. Low-cost sensors based on polymer optical fibers have been elaborated. Sensors have been examined for their sensitivity to CO2, temperature and humidity. Response time during cyclic exposures to CO2 have been also determined. Special layers exhibiting irreversible change of color during exposure to carbon dioxide have been developed. They have been verified for a possible use in smart food packaging.

Magneto-optical properties of cerium substituted yttrium iron garnet films with reduced thermal budget for monolithic photonic integrated circuits.

PubMed

Goto, Taichi; Onbaşlı, Mehmet C; Ross, C A

2012-12-17

Thin films of polycrystalline cerium substituted yttrium iron garnet (CeYIG) were grown on an yttrium iron garnet (YIG) seed layer on Si and Si-on-insulator substrates by pulsed laser deposition, and their optical and magneto-optical properties in the near-IR region were measured. A YIG seed layer of ~30 nm thick processed by rapid thermal anneal at 800°C provided a virtual substrate to promote crystallization of the CeYIG. The effect of the thermal budget of the YIG/CeYIG growth process on the film structure, magnetic and magnetooptical properties was determined.

Retinal Nerve Fiber Layer and Peripapillary Choroidal Thicknesses in Non-Glaucomatous Unilateral Optic Atrophy Compared with Unilateral Advanced Pseudoexfoliative Glaucoma.

PubMed

Kucukevcilioglu, Murat; Ayyildiz, Onder; Aykas, Seckin; Gokce, Gokcen; Koylu, Mehmet Talay; Ozgonul, Cem; Ozge, Gokhan; Mumcuoglu, Tarkan; Yumusak, Erhan

2017-02-01

To investigate retinal nerve fiber layer thickness (RNFL-T) and peripapillary choroidal thickness (PC-T) in non-glaucomatous optic atrophy (OA) patients in comparison with unaffected and control eyes, furthermore, to compare thickness profiles with unilateral pseudoexfoliative advanced glaucoma. Thirty-three eyes with OA (Group A), 33 unaffected fellow eyes (Group B), 25 right eyes of 25 control subjects (Group C), and 15 eyes with advanced glaucoma (Group D) were enrolled. RNFL-T was measured in six regions by spectral-domain optical coherence tomography. Enhanced depth imaging optical coherence tomography was obtained to evaluate PC-T in corresponding regions. RNFL-T was significantly lower in Group A than in Groups B and C globally and at all peripapillary regions (all p < 0.001). P-CT in Group A was significantly lower globally (p = 0.03) and in three regions (temporal, p = 0.001; temporal-superior, p = 0.01; and nasal-inferior, p = 0.037) versus Group C. However, it was significantly thinner than in Group B in all regions (temporal, p = 0.02; temporal-superior, p = 0.013; nasal-superior, p = 0.044; nasal, p = 0.02; nasal-inferior, p < 0.001; and temporal-inferior, p < 0.001) and globally (p < 0.001). In Group A RNFL-T (thicker superiorly and inferiorly; thinner temporally and nasally) and PC-T (superior > temporal > nasal > inferior) profiles were almost identical to that in unaffected fellow eyes and control eyes. However, Group D showed different patterns with less regional differences in RNFL-T, and the greatest value of PC-T in nasal quadrant. Besides retinal nerve fiber layer thinning, non-glaucomatous OA is associated with choroidal thinning. The RNFL-T and PC-T profiles in advanced glaucoma eyes differed from the common patterns seen among OA eyes, unaffected fellow eyes, and control eyes.

Ice Cloud Optical Thickness and Extinction Estimates from Radar Measurements.

NASA Astrophysics Data System (ADS)

Matrosov, Sergey Y.; Shupe, Matthew D.; Heymsfield, Andrew J.; Zuidema, Paquita

2003-11-01

A remote sensing method is proposed to derive vertical profiles of the visible extinction coefficients in ice clouds from measurements of the radar reflectivity and Doppler velocity taken by a vertically pointing 35-GHz cloud radar. The extinction coefficient and its vertical integral, optical thickness τ, are among the fundamental cloud optical parameters that, to a large extent, determine the radiative impact of clouds. The results obtained with this method could be used as input for different climate and radiation models and for comparisons with parameterizations that relate cloud microphysical parameters and optical properties. An important advantage of the proposed method is its potential applicability to multicloud situations and mixed-phase conditions. In the latter case, it might be able to provide the information on the ice component of mixed-phase clouds if the radar moments are dominated by this component. The uncertainties of radar-based retrievals of cloud visible optical thickness are estimated by comparing retrieval results with optical thicknesses obtained independently from radiometric measurements during the yearlong Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment. The radiometric measurements provide a robust way to estimate τ but are applicable only to optically thin ice clouds without intervening liquid layers. The comparisons of cloud optical thicknesses retrieved from radar and from radiometer measurements indicate an uncertainty of about 77% and a bias of about -14% in the radar estimates of τ relative to radiometric retrievals. One possible explanation of the negative bias is an inherently low sensitivity of radar measurements to smaller cloud particles that still contribute noticeably to the cloud extinction. This estimate of the uncertainty is in line with simple theoretical considerations, and the associated retrieval accuracy should be considered good for a nonoptical instrument, such as radar. This paper also presents relations between radar-derived characteristic cloud particle sizes and effective sizes used in models. An average relation among τ, cloud ice water path, and the layer mean value of cloud particle characteristic size is also given. This relation is found to be in good agreement with in situ measurements. Despite a high uncertainty of radar estimates of extinction, this method is useful for many clouds where optical measurements are not available because of cloud multilayering or opaqueness.

Controlling contamination in Mo/Si multilayer mirrors by Si surface capping modifications

NASA Astrophysics Data System (ADS)

Malinowski, Michael E.; Steinhaus, Chip; Clift, W. Miles; Klebanoff, Leonard E.; Mrowka, Stanley; Soufli, Regina

2002-07-01

The performance of Mo/Si multilayer mirrors (MLMs) used to reflect UV (EUV) radiation in an EUV + hydrocarbon (NC) vapor environment can be improved by optimizing the silicon capping layer thickness on the MLM in order to minimize the initial buildup of carbon on MLMs. Carbon buildup is undesirable since it can absorb EUV radiation and reduce MLM reflectivity. A set of Mo/Si MLMs deposited on Si wafers was fabricated such that each MLM had a different Si capping layer thickness ranging form 2 nm to 7 nm. Samples from each MLM wafer were exposed to a combination of EUV light + (HC) vapors at the Advanced Light Source (ALS) synchrotron in order to determine if the Si capping layer thickness affected the carbon buildup on the MLMs. It was found that the capping layer thickness had a major influence on this 'carbonizing' tendency, with the 3 nm layer thickness providing the best initial resistance to carbonizing and accompanying EUV reflectivity loss in the MLM. The Si capping layer thickness deposited on a typical EUV optic is 4.3 nm. Measurements of the absolute reflectivities performed on the Calibration and Standards beamline at the ALS indicated the EUV reflectivity of the 3 nm-capped MLM was actually slightly higher than that of the normal, 4 nm Si-capped sample. These results show that he use of a 3 nm capping layer represents an improvement over the 4 nm layer since the 3 nm has both a higher absolute reflectivity and better initial resistance to carbon buildup. The results also support the general concept of minimizing the electric field intensity at the MLM surface to minimize photoelectron production and, correspondingly, carbon buildup in a EUV + HC vapor environment.

Feasibility study of multi-pixel retrieval of optical thickness and droplet effective radius of inhomogeneous clouds using deep learning

NASA Astrophysics Data System (ADS)

Okamura, Rintaro; Iwabuchi, Hironobu; Schmidt, K. Sebastian

2017-12-01

Three-dimensional (3-D) radiative-transfer effects are a major source of retrieval errors in satellite-based optical remote sensing of clouds. The challenge is that 3-D effects manifest themselves across multiple satellite pixels, which traditional single-pixel approaches cannot capture. In this study, we present two multi-pixel retrieval approaches based on deep learning, a technique that is becoming increasingly successful for complex problems in engineering and other areas. Specifically, we use deep neural networks (DNNs) to obtain multi-pixel estimates of cloud optical thickness and column-mean cloud droplet effective radius from multispectral, multi-pixel radiances. The first DNN method corrects traditional bispectral retrievals based on the plane-parallel homogeneous cloud assumption using the reflectances at the same two wavelengths. The other DNN method uses so-called convolutional layers and retrieves cloud properties directly from the reflectances at four wavelengths. The DNN methods are trained and tested on cloud fields from large-eddy simulations used as input to a 3-D radiative-transfer model to simulate upward radiances. The second DNN-based retrieval, sidestepping the bispectral retrieval step through convolutional layers, is shown to be more accurate. It reduces 3-D radiative-transfer effects that would otherwise affect the radiance values and estimates cloud properties robustly even for optically thick clouds.

Layer-Dependent Third-Harmonic Generation in Graphene

NASA Astrophysics Data System (ADS)

Yang, Hao; Guan, Honghua; Dadap, Jerry; Osgood, Richard; Richard Osgood Team

Graphene has become a subject of intense interest and study because of its remarkable 2D electronic properties. Multilayer graphene also offers an array of properties that are also of interest for optical physics and devices. Despite its second-order-nonlinear optical response is intrinsically weak, third-order nonlinear optical effects in graphene are symmetry-allowed thus leading to studies of several third-order process in few-layer graphene. In this work, we report third-harmonic generation in multilayer graphene mounted on fused silica and with thicknesses which approach the bulk continuum. THG signals show cubic power dependence with respect to the intensity of fundamental beam. Third-harmonic generation spectroscopy enables a good fit using linear optical detection, which shows strong contrast for different layer number graphene. The maximum THG efficiency appears at layer number around 30. Two models are used for describing this layer dependent phenomenon and shows absorption plays a key role in THG of multilayer graphene. This work also provides a new imaging technology for graphene detection and identification with better contrast and resolution. U.S. Department of Energy under Contract No. DE-FG 02-04-ER-46157.

Accurate Spectral Fits of Jupiter's Great Red Spot: VIMS Visual Spectra Modelled with Chromophores Created by Photolyzed Ammonia Reacting with Acetyleneχ±

NASA Astrophysics Data System (ADS)

Baines, Kevin; Sromovsky, Lawrence A.; Fry, Patrick M.; Carlson, Robert W.; Momary, Thomas W.

2016-10-01

We report results incorporating the red-tinted photochemically-generated aerosols of Carlson et al (2016, Icarus 274, 106-115) in spectral models of Jupiter's Great Red Spot (GRS). Spectral models of the 0.35-1.0-micron spectrum show good agreement with Cassini/VIMS near-center-meridian and near-limb GRS spectra for model morphologies incorporating an optically-thin layer of Carlson (2016) aerosols at high altitudes, either at the top of the tropospheric GRS cloud, or in a distinct stratospheric haze layer. Specifically, a two-layer "crème brûlée" structure of the Mie-scattering Carlson et al (2016) chromophore attached to the top of a conservatively scattering (hereafter, "white") optically-thick cloud fits the spectra well. Currently, best agreement (reduced χ2 of 0.89 for the central-meridian spectrum) is found for a 0.195-0.217-bar, 0.19 ± 0.02 opacity layer of chromophores with mean particle radius of 0.14 ± 0.01 micron. As well, a structure with a detached stratospheric chromophore layer ~0.25 bar above a white tropospheric GRS cloud provides a good spectral match (reduced χ2 of 1.16). Alternatively, a cloud morphology with the chromophore coating white particles in a single optically- and physically-thick cloud (the "coated-shell model", initially explored by Carlson et al 2016) was found to give significantly inferior fits (best reduced χ2 of 2.9). Overall, we find that models accurately fit the GRS spectrum if (1) most of the optical depth of the chromophore is in a layer near the top of the main cloud or in a distinct separated layer above it, but is not uniformly distributed within the main cloud, (2) the chromophore consists of relatively small, 0.1-0.2-micron-radius particles, and (3) the chromophore layer optical depth is small, ~ 0.1-0.2. Thus, our analysis supports the exogenic origin of the red chromophore consistent with the Carlson et al (2016) photolytic production mechanism rather than an endogenic origin, such as upwelling of material from the depths of Jupiter.

Mode propagation in optical nanowaveguides with dielectric cores and surrounding metal layers.

PubMed

Lapchuk, Anatoly S; Shin, Dongho; Jeong, Ho-Seop; Kyong, Chun Su; Shin, Dong-Ik

2005-12-10

The mode spectrum in an optical nanowaveguide consisting of a dielectric-core layer surrounded by two identical metal layers is investigated. A simple model based on mode matching to predict the properties of mode propagation in such optical nanowaveguides is proposed. It is shown that quasi-TM00 and quasi-TM10 modes supported by an optical microstrip line do not have a cutoff frequency, regardless of the size of the metal strips, the thickness of the dielectric slab, and the cross-sectional shape. The transverse size of the TM00 mode supported by a nanosized microstrip line was found to be approximately equal to the transverse dimension of the microstrip line. In closed rectangular and elliptical nanowaveguides, i.e., in which all dielectric surfaces are covered with metal films, the cross-sectional shape of the waveguide should be stretched along one side to produce propagation conditions for the fundamental mode.

A comparison between high-altitude horizon photography and direct sampling of El Chichon cloud particles

NASA Technical Reports Server (NTRS)

Coletti, A.; Hofmann, D. J.; Rosen, J. M.

1986-01-01

Perturbations to the visible radiation by the El Chichon aerosol layers in the stratosphere observed on May 18, 1982 in Laredo, Texas using in situ, time-lapsed photography are analyzed. The densitometric data are compared with optical counter data. Good correlation is detected for the scattered light intensities of the sky estimated with the two techniques. It is observed that the optical thickness of the stratosphere from 18.8 km to the top of the atmosphere = 0.18 and the residual optical thickness at 27 km = 0.0007. The relationship between the isodensity contours and the height of the observations, cloud cover, specific vertical aerosol distribution, and earth curvature is examined.

Elevated serum IGF-1 level enhances retinal and choroidal thickness in untreated acromegaly patients.

PubMed

Zhang, Xia; Ma, Jin; Wang, Yuhan; Li, Lüe; Gao, Lu; Guo, Xiaopeng; Xing, Bing; Zhong, Yong

2018-03-01

1) To compare the retinal, choroidal, Haller's layer, and Sattler's/choriocapillaris thicknesses of untreated acromegaly patients without chiasm compression or diabetes mellitus and healthy controls. 2) To evaluate the correlations of retinal and choroidal thicknesses with serum growth hormone (GH) and insulin-like growth factor 1 (IGF) burden. This prospective, case-control study included 27 untreated acromegaly patients and 27 sex-matched and age-matched controls. Subfoveal choroidal, Haller's layer and Sattler's/choriocapillaris thicknesses were determined by enhanced-depth imaging optical coherence tomography (EDI-OCT). Foveal and macular retinal thicknesses were determined with SD-OCT. GH and IGF-1 burdens were defined as the product of disease duration and treatment-naïve serum GH and IGF-1 levels. Compared with healthy controls, patients with acromegaly exhibited significantly increased foveal retinal (p = 0.003), subfoveal choroidal (p < 0.001), and Haller's layer (p < 0.001) thicknesses, with no differences in Sattler's/choriocapillaris layer thickness. Multiple point measurements in the posterior pole area showed equally increased nasal and temporal parts of the choroid. The retinal thickness maps of the two groups did not significantly differ. Correlation analysis indicated that choroidal thickness was significantly correlated with disease duration (p = 0.01), serum IGF-1 level (p = 0.03) and IGF-1 burden (p = 0.009). No significant correlations were detected between choroidal thickness and GH burden (p = 0.44). Retinal thickness was not significantly correlated with any factor. The choroidal thickness of acromegaly patients was greater than that of healthy controls and was significantly correlated with disease duration, IGF-1 level and IGF-1 burden, indicating that excessive serum IGF-1 and its exposure time have a combined effect on choroidal thickness.

Enhanced interface perpendicular magnetic anisotropy in electrodeposited Co/Au(111) layers

NASA Astrophysics Data System (ADS)

Cagnon, L.; Devolder, T.; Cortes, R.; Morrone, A.; Schmidt, J. E.; Chappert, C.; Allongue, P.

2001-03-01

This work investigates the structure and interface perpendicular magnetic anisotropy (PMA) of electrodeposited Cu/Co/Au(111) sandwiches with variable Co thickness [2-20 monolayers (ML's)]. In optimum deposition conditions, polar magneto-optical Kerr effect measurements show that the axis of easy magnetization is perpendicular to the layers for thicknesses below ca. 7.2 ML's. This value is among the best ever reported for the Cu/Co/Au(111) structure. While extended x-ray-absorption fine structure indicates that layers are hcp, in situ STM imaging suggests that magnetoelastic effects contribute significantly to PMA. The correlation observed between the strength of PMA and film structure is discussed in details.

Optical transparency of graphene layers grown on metal surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rut’kov, E. V.; Lavrovskaya, N. P.; Sheshenya, E. S., E-mail: sheshenayket@gmail.ru

It is shown that, in contradiction with the fundamental results obtained for free graphene, graphene films grown on the Rh(111) surface to thicknesses from one to ~(12–15) single layers do not absorb visible electromagnetic radiation emitted from the surface and influence neither the brightness nor true temperature of the sample. At larger thicknesses, such absorption occurs. This effect is observed for the surfaces of other metals, specifically, Pt(111), Re(1010), and Ni(111) and, thus, can be considered as being universal. It is thought that the effect is due to changes in the electronic properties of thin graphene layers because of electronmore » transfer between graphene and the metal substrate.« less

Optical Tamm states in one-dimensional superconducting photonic crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

El Abouti, O.; El Boudouti, E. H.; IEMN, UMR-CNRS 8520, UFR de Physique, Université de Lille 1, 59655 Villeneuve d'Ascq

2016-08-15

In this study, we investigate localized and resonant optical waves associated with a semi-infinite superlattice made out of superconductor-dielectric bilayers and terminated with a cap layer. Both transverse electric and transverse magnetic waves are considered. These surface modes are analogous to the so-called Tamm states associated with electronic states found at the surface of materials. The surface guided modes induced by the cap layer strongly depend on whether the superlattice ends with a superconductor or a dielectric layer, the thickness of the surface layer, the temperature of the superconductor layer as well as on the polarization of the waves. Differentmore » kinds of surface modes are found and their properties examined. These structures can be used to realize the highly sensitive photonic crystal sensors.« less

Nanostructured diamond layers enhance the infrared spectroscopy of biomolecules.

PubMed

Kozak, Halyna; Babchenko, Oleg; Artemenko, Anna; Ukraintsev, Egor; Remes, Zdenek; Rezek, Bohuslav; Kromka, Alexander

2014-03-04

We report on the fabrication and practical use of high-quality optical elements based on Au mirrors coated with diamond layers with flat, nanocolumnar, and nanoporous morphologies. Diamond layers (100 nm thickness) are grown at low temperatures (about 300 °C) from a methane, carbon dioxide, and hydrogen gas mixture by a pulsed microwave plasma system with linear antennas. Using grazing angle reflectance (GAR) Fourier transform infrared spectroscopy with p-polarized light, we compare the IR spectra of fetal bovine serum proteins adsorbed on diamond layers with oxidized (hydrophilic) surfaces. We show that the nanoporous diamond layers provide IR spectra with a signal gain of about 600% and a significantly improved sensitivity limit. This is attributed to its enhanced internal surface area. The improved sensitivity enabled us to distinguish weak infrared absorption peaks of <10-nm-thick protein layers and thereby to analyze the intimate diamond-molecule interface.

Photoinduced charge-transfer materials for nonlinear optical applications

DOEpatents

McBranch, Duncan W.

2006-10-24

A method using polyelectrolyte self-assembly for preparing multi-layered organic molecular materials having individual layers which exhibit ultrafast electron and/or energy transfer in a controlled direction occurring over the entire structure. Using a high molecular weight, water-soluble, anionic form of poly-phenylene vinylene, self-assembled films can be formed which show high photoluminescence quantum efficiency (QE). The highest emission QE is achieved using poly(propylene-imine) (PPI) dendrimers as cationic binders. Self-quenching of the luminescence is observed as the solid polymer film thickness is increased and can be reversed by inserting additional spacer layers of transparent polyelectrolytes between each active conjugated layer, such that the QE grows with thickness. A red shift of the luminescence is also observed as additional PPV layers are added. This effect persists as self-quenching is eliminated. Charge transfer superlattices can be formed by additionally incorporating C.sub.60 acceptor layers.

Infrared fingerprints of few-layer black phosphorus.

PubMed

Zhang, Guowei; Huang, Shenyang; Chaves, Andrey; Song, Chaoyu; Özçelik, V Ongun; Low, Tony; Yan, Hugen

2017-01-06

Black phosphorus is an infrared layered material. Its bandgap complements other widely studied two-dimensional materials: zero-gap graphene and visible/near-infrared gap transition metal dichalcogenides. Although highly desirable, a comprehensive infrared characterization is still lacking. Here we report a systematic infrared study of mechanically exfoliated few-layer black phosphorus, with thickness ranging from 2 to 15 layers and photon energy spanning from 0.25 to 1.36 eV. Each few-layer black phosphorus exhibits a thickness-dependent unique infrared spectrum with a series of absorption resonances, which reveals the underlying electronic structure evolution and serves as its infrared fingerprints. Surprisingly, unexpected absorption features, which are associated with the forbidden optical transitions, have been observed. Furthermore, we unambiguously demonstrate that controllable uniaxial strain can be used as a convenient and effective approach to tune the electronic structure of few-layer black phosphorus. Our study paves the way for black phosphorus applications in infrared photonics and optoelectronics.

The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

PubMed Central

2012-01-01

Background To evaluate the influence of corneal astigmatism (CA) on retinal nerve fiber layer (RNFL) thickness and optic nerve head(ONH) parameters measured with spectral-domain optical coherence tomography (OCT) in high myopes patients before refractive surgery. Methods Seventy eyes of 35 consecutive refractive surgery candidates were included in this study. The mean age of the subjects was 26.42 ± 6.95 years, the average CA was −1.17 diopters (D; SD 0.64; range −0.2 to-3.3D), All subjects in this study were WTR CA. 34 eyes were in the normal CA group with a mean CA was −0.67 ± 0.28D, 36 eyes were in the high CA group with an average CA of −1.65 ± 0.49D. All subjects underwent ophthalmic examination and imaging with the Cirrus HD OCT. Results No significant difference was noted in the average cup-to-disk ratio, vertical cup-to-disk ratio and cup volume (all P values > 0.05). Compared with the normal CA group, the high CA group had a larger disc area and rim area, thinner RNFL thickness in the temporal quadrant, and the superotemporal and inferotemporal peaks were farther to the temporal horizon (All P values < 0.05). There were no significant differences between the two groups in global average RNFL thickness, as well as superior, nasal and inferior quadrant RNFL thickness (all P values > 0.05). Conclusions The degree of with-the-rule CA should be considered when interpreting ONH parameters and peripapillary RNFL thickness measured by the Cirrus HD OCT. Virtual slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1148475676881895 PMID:22621341

Composite material for optical oxygen sensor

NASA Astrophysics Data System (ADS)

Antropov, A. P.; Ragutkin, A. V.; Melnikov, P. V.; Luchnikov, P. A.; Zaitsev, N. K.

2018-01-01

A new composite material for use in optical molecular oxygen sensors is proposed. The absence of pores on the surface of the material avoids microbiological fouling and concomitant deterioration of the characteristics with time, and the presence of the mesoporous phase results in a linear calibration and acceptable response times, even for layers that are significant in thickness.

Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties

NASA Astrophysics Data System (ADS)

Richardson, Mark; Stephens, Graeme L.

2018-03-01

Information content analysis is used to select channels for a marine liquid cloud retrieval using the high-spectral-resolution oxygen A-band instrument on NASA's Orbiting Carbon Observatory-2 (OCO-2). Desired retrieval properties are cloud optical depth, cloud-top pressure and cloud pressure thickness, which is the geometric thickness expressed in hectopascals. Based on information content criteria we select a micro-window of 75 of the 853 functioning OCO-2 channels spanning 763.5-764.6 nm and perform a series of synthetic retrievals with perturbed initial conditions. We estimate posterior errors from the sample standard deviations and obtain ±0.75 in optical depth and ±12.9 hPa in both cloud-top pressure and cloud pressure thickness, although removing the 10 % of samples with the highest χ2 reduces posterior error in cloud-top pressure to ±2.9 hPa and cloud pressure thickness to ±2.5 hPa. The application of this retrieval to real OCO-2 measurements is briefly discussed, along with limitations and the greatest caution is urged regarding the assumption of a single homogeneous cloud layer, which is often, but not always, a reasonable approximation for marine boundary layer clouds.

Demonstration of enhanced continuous-wave operation of blue laser diodes on a semipolar 202¯1¯ GaN substrate using indium-tin-oxide/thin-p-GaN cladding layers.

PubMed

Mehari, Shlomo; Cohen, Daniel A; Becerra, Daniel L; Nakamura, Shuji; DenBaars, Steven P

2018-01-22

The benefits of utilizing transparent conductive oxide on top of a thin p-GaN layer for continuous-wave (CW) operation of blue laser diodes (LDs) were investigated. A very low operating voltage of 5.35 V at 10 kA/cm 2 was obtained for LDs with 250 nm thick p-GaN compared to 7.3 V for LDs with conventional 650 nm thick p-GaN. An improved thermal performance was also observed for the thin p-GaN samples resulting in a 40% increase in peak light output power and a 32% decrease in surface temperature. Finally, a tradeoff was demonstrated between low operating voltage and increased optical modal loss in the indium tin oxide (ITO) with thinner p-GaN. LDs lasing at 445 nm with 150 nm thick p-GaN had an excess modal loss while LDs with an optimal 250 nm thick p-GaN resulted in optical output power of 1.1 W per facet without facet coatings and a wall-plug efficiency of 15%.

Multilayer optical dielectric coating

DOEpatents

Emmett, John L.

1990-01-01

A highly damage resistant, multilayer, optical reflective coating includes alternating layers of doped and undoped dielectric material. The doping levels are low enough that there are no distinct interfaces between the doped and undoped layers so that the coating has properties nearly identical to the undoped material. The coating is fabricated at high temperature with plasma-assisted chemical vapor deposition techniques to eliminate defects, reduce energy-absorption sites, and maintain proper chemical stoichiometry. A number of differently-doped layer pairs, each layer having a thickness equal to one-quarter of a predetermined wavelength in the material are combined to form a narrowband reflective coating for a predetermined wavelength. Broadband reflectors are made by using a number of narrowband reflectors, each covering a portion of the broadband.

Automated 3D segmentation of intraretinal layers from optic nerve head optical coherence tomography images

NASA Astrophysics Data System (ADS)

Antony, Bhavna J.; Abràmoff, Michael D.; Lee, Kyungmoo; Sonkova, Pavlina; Gupta, Priya; Kwon, Young; Niemeijer, Meindert; Hu, Zhihong; Garvin, Mona K.

2010-03-01

Optical coherence tomography (OCT), being a noninvasive imaging modality, has begun to find vast use in the diagnosis and management of ocular diseases such as glaucoma, where the retinal nerve fiber layer (RNFL) has been known to thin. Furthermore, the recent availability of the considerably larger volumetric data with spectral-domain OCT has increased the need for new processing techniques. In this paper, we present an automated 3-D graph-theoretic approach for the segmentation of 7 surfaces (6 layers) of the retina from 3-D spectral-domain OCT images centered on the optic nerve head (ONH). The multiple surfaces are detected simultaneously through the computation of a minimum-cost closed set in a vertex-weighted graph constructed using edge/regional information, and subject to a priori determined varying surface interaction and smoothness constraints. The method also addresses the challenges posed by presence of the large blood vessels and the optic disc. The algorithm was compared to the average manual tracings of two observers on a total of 15 volumetric scans, and the border positioning error was found to be 7.25 +/- 1.08 μm and 8.94 +/- 3.76 μm for the normal and glaucomatous eyes, respectively. The RNFL thickness was also computed for 26 normal and 70 glaucomatous scans where the glaucomatous eyes showed a significant thinning (p < 0.01, mean thickness 73.7 +/- 32.7 μm in normal eyes versus 60.4 +/- 25.2 μm in glaucomatous eyes).

Macular Ganglion Cell and Retinal Nerve Fiber Layer Thickness in Children With Refractive Errors-An Optical Coherence Tomography Study.

PubMed

Goh, Jody P; Koh, Victor; Chan, Yiong Huak; Ngo, Cheryl

2017-07-01

To study the distribution of macular ganglion cell-inner plexiform layer (GC-IPL) thickness and peripapillary retinal nerve fiber layer (RNFL) thickness in children with refractive errors. Two hundred forty-three healthy eyes from 139 children with refractive error ranging from -10.00 to +5.00 D were recruited from the National University Hospital Eye Surgery outpatient clinic. After a comprehensive ocular examination, refraction, and axial length (AL) measurement (IOLMaster), macular GC-IPL and RNFL thickness values were obtained with a spectral domain Cirrus high definition optical coherence tomography system (Carl Zeiss Meditec Inc.). Only scans with signal strength of >6/10 were included. Correlation between variables was calculated using the Pearson correlation coefficient. A multivariate analysis using mixed models was done to adjust for confounders. The mean spherical equivalent refraction was -3.20±3.51 D and mean AL was 24.39±1.72 mm. Average, minimum, superior, and inferior GC-IPL were 82.59±6.29, 77.17±9.65, 83.68±6.96, and 81.64±6.70 μm, respectively. Average, superior, and inferior peripapillary RNFL were 99.00±11.45, 123.20±25.81, and 124.24±22.23 μm, respectively. Average, superior, and inferior GC-IPL were correlated with AL (β=-2.056, P-value 0.000; β=-2.383, P-value 0.000; β=-1.721, P-value 0.000), but minimum GC-IPL was not (β=-1.056, P-value 0.115). None of the RNFL parameters were correlated with AL. This study establishes normative macular GC-IPL and RNFL thickness in children with refractive errors. Our results suggest that high definition optical coherence tomography RNFL parameters and minimum GC-IPL are not affected by AL or myopia in children, and therefore warrants further evaluation in pediatric glaucoma patients.

FIBER AND INTEGRATED OPTICS: Waveguide characteristics of real optical strip waveguides

NASA Astrophysics Data System (ADS)

Shmal'ko, A. V.; Frolov, V. V.

1990-01-01

A study is reported of the influence of the parameters of real thin-film optical strip waveguides on their waveguide characteristics (propagation constants, localization of the mode field, etc.) allowing for the presence of transition layers in a transverse cross section of the base planar waveguide, for the real geometry of this section (which is nearly trapezoidal), and for the thickness of the guiding strip. Analytic expressions are obtained for the optical confinement coefficient and the effective mode format of a weakly guiding symmetric strip waveguide. It is shown that the coefficient representing the fundamental E11x(y) mode is practically independent of the relative thickness t /h (h is the thickness of the base planar waveguide) of the guiding strip provided t /h>=0.5. The corrections to the normalized effective refractive indices of the base planar and strip waveguides are found in order to allow for the real geometry and for the refractive index profile in the strip waveguide.

Fiber optic interferometry for industrial process monitoring and control applications

NASA Astrophysics Data System (ADS)

Marcus, Michael A.

2002-02-01

Over the past few years we have been developing applications for a high-resolution (sub-micron accuracy) fiber optic coupled dual Michelson interferometer-based instrument. It is being utilized in a variety of applications including monitoring liquid layer thickness uniformity on coating hoppers, film base thickness uniformity measurement, digital camera focus assessment, optical cell path length assessment and imager and wafer surface profile mapping. The instrument includes both coherent and non-coherent light sources, custom application dependent optical probes and sample interfaces, a Michelson interferometer, custom electronics, a Pentium-based PC with data acquisition cards and LabWindows CVI or LabView based application specific software. This paper describes the development evolution of this instrument platform and applications highlighting robust instrument design, hardware, software, and user interfaces development. The talk concludes with a discussion of a new high-speed instrument configuration, which can be utilized for high speed surface profiling and as an on-line web thickness gauge.

The opto-thermal effect on encapsulated cholesteric liquid crystals

NASA Astrophysics Data System (ADS)

Liu, Yu-Sung; Lin, Hui-Chi; Yang, Kin-Min

2017-12-01

In this study, we implemented a micro-encapsulated CLC electronic paper that is optically addressed and electrically erasable. The mechanism that forms spot diameters on the CLC films is discussed and verified through various experimental parameters, including the thickness of CLCs and Poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) (PEDOT:PSS), pump intensity, and pumping time. The opto-thermal effect, brought on by the PEDOT:PSS absorbing layer, causes the spot diameters on the cholesteric liquid crystal thin films to vary. According to our results, the spot diameter is larger for a sample with a thinner cholesteric liquid crystal layer with the same excitation conditions and same thickness of the PEDOT layer. The spot diameter is also larger for a sample with a thicker PEDOT under the same excitation conditions and same thickness of the cholesteric liquid crystal layer. We proposed a simple heat-conducting model to explain the experimental results, which qualitatively agree with this theoretical model.

An ultra-thin, un-doped NiO hole transporting layer of highly efficient (16.4%) organic-inorganic hybrid perovskite solar cells.

PubMed

Seo, Seongrok; Park, Ik Jae; Kim, Myungjun; Lee, Seonhee; Bae, Changdeuck; Jung, Hyun Suk; Park, Nam-Gyu; Kim, Jin Young; Shin, Hyunjung

2016-06-02

NiO is a wide band gap p-type oxide semiconductor and has potential for applications in solar energy conversion as a hole-transporting layer (HTL). It also has good optical transparency and high chemical stability, and the capability of aligning the band edges to the perovskite (CH3NH3PbI3) layers. Ultra-thin and un-doped NiO films with much less absorption loss were prepared by atomic layer deposition (ALD) with highly precise control over thickness without any pinholes. Thin enough (5-7.5 nm in thickness) NiO films with the thickness of few time the Debye length (LD = 1-2 nm for NiO) show enough conductivities achieved by overlapping space charge regions. The inverted planar perovskite solar cells with NiO films as HTLs exhibited the highest energy conversion efficiency of 16.40% with high open circuit voltage (1.04 V) and fill factor (0.72) with negligible current-voltage hysteresis.

Using spectral-domain optical coherence tomography to detect optic neuropathy in patients with craniosynostosis.

PubMed

Dagi, Linda R; Tiedemann, Laura M; Heidary, Gena; Robson, Caroline D; Hall, Amber M; Zurakowski, David

2014-12-01

Detecting and monitoring optic neuropathy in patients with craniosynostosis is a clinical challenge due to limited cooperation, and subjective measures of visual function. The purpose of this study was to appraise the correlation of peripapillary retinal nerve fiber layer (RNFL) thickness measured by spectral-domain ocular coherence tomography (SD-OCT) with indication of optic neuropathy based on fundus examination. The medical records of all patients with craniosynostosis presenting for ophthalmic evaluation during 2013 were retrospectively reviewed. The following data were abstracted from the record: diagnosis, historical evidence of elevated intracranial pressure, current ophthalmic evaluation and visual field results, and current peripapillary RNFL thickness. A total of 54 patients were included (mean age, 10.6 years [range, 2.4-33.8 years]). Thirteen (24%) had evidence of optic neuropathy based on current fundus examination. Of these, 10 (77%) demonstrated either peripapillary RNFL elevation and papilledema or depression with optic atrophy. Sensitivity for detecting optic atrophy was 88%; for papilledema, 60%; and for either form of optic neuropathy, 77%. Specificity was 94%, 90%, and 83%, respectively. Kappa agreement was substantial for optic atrophy (κ = 0.73) and moderate for papilledema (κ = 0.39) and for either form of optic neuropathy (κ = 0.54). Logistic regression indicated that peripapillary RNFL thickness was predictive of optic neuropathy (P < 0.001). Multivariable analysis demonstrated that RNFL thickness measurements were more sensitive at detecting optic neuropathy than visual field testing (likelihood ratio = 10.02; P = 0.002). Sensitivity and specificity of logMAR visual acuity in detecting optic neuropathy were 15% and 95%, respectively. Peripapillary RNFL thickness measured by SD-OCT provides adjunctive evidence for identifying optic neuropathy in patients with craniosynostosis and appears more sensitive at detecting optic atrophy than papilledema. Copyright © 2014 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

Optical bandgap of single- and multi-layered amorphous germanium ultra-thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Pei; Zaslavsky, Alexander; Longo, Paolo

2016-01-07

Accurate optical methods are required to determine the energy bandgap of amorphous semiconductors and elucidate the role of quantum confinement in nanometer-scale, ultra-thin absorbing layers. Here, we provide a critical comparison between well-established methods that are generally employed to determine the optical bandgap of thin-film amorphous semiconductors, starting from normal-incidence reflectance and transmittance measurements. First, we demonstrate that a more accurate estimate of the optical bandgap can be achieved by using a multiple-reflection interference model. We show that this model generates more reliable results compared to the widely accepted single-pass absorption method. Second, we compare two most representative methods (Taucmore » and Cody plots) that are extensively used to determine the optical bandgap of thin-film amorphous semiconductors starting from the extracted absorption coefficient. Analysis of the experimental absorption data acquired for ultra-thin amorphous germanium (a-Ge) layers demonstrates that the Cody model is able to provide a less ambiguous energy bandgap value. Finally, we apply our proposed method to experimentally determine the optical bandgap of a-Ge/SiO{sub 2} superlattices with single and multiple a-Ge layers down to 2 nm thickness.« less

Optical absorption enhancement by inserting ZnO optical spacer in plasmonic organic solar cells

NASA Astrophysics Data System (ADS)

N'Konou, Kekeli; Torchio, Philippe

2018-01-01

Optical absorption enhancement (AE) using coupled optical spacer and plasmonic effects in standard and inverted organic solar cells (OSCs) are demonstrated using the finite-difference time-domain numerical method. The influence of an added zinc oxide (ZnO) optical spacer layer inserted below the active layer in standard architecture is first theoretically investigated while the influence of varying the ZnO cathodic buffer layer thickness in inverted design is studied on AE. Then, the embedding of a square periodic array of core-shell silver-silica nanospheres (Ag@SiO2 NSs) at different positions in standard and inverted OSCs is performed while AE and short-circuit current density (Jsc) are calculated. As a result of previous combined effects, the optimized standard plasmonic OSCs present 15% and 79.45% enhancement in J over the reference with and without ZnO optical spacer layer, respectively, and a 16% increase of AE when Ag@SiO2 NSs are placed on top of the PEDOT:PSS layer. Compared to the inverted OSC reference, the plasmonic OSCs present 26% and 27% enhancement in J and AE, respectively, when the Ag@SiO2 NSs are located on top of the ZnO layer. Furthermore, the spatial position of these NSs in such OSCs is a key parameter for increasing light absorption via enhanced electromagnetic field distribution.

Optical and electrical characterization methods of plasma-induced damage in silicon nitride films

NASA Astrophysics Data System (ADS)

Kuyama, Tomohiro; Eriguchi, Koji

2018-06-01

We proposed evaluation methods of plasma-induced damage (PID) in silicon nitride (SiN) films. The formation of an oxide layer by air exposure was identified for damaged SiN films by X-ray photoelectron spectroscopy (XPS). Bruggeman’s effective medium approximation was employed for an optical model consisting of damaged and undamaged layers, which is applicable to an in-line monitoring by spectroscopic ellipsometry (SE). The optical thickness of the damaged layer — an oxidized layer — extended after plasma exposure, which was consistent with the results obtained by a diluted hydrofluoric acid (DHF) wet etching. The change in the conduction band edge of the damaged SiN films was presumed from two electrical techniques, i.e., current–voltage (I–V) measurement and time-dependent dielectric breakdown (TDDB) test with a constant voltage stress. The proposed techniques can be used for assigning the plasma-induced structural change in an SiN film widely used as an etch-protecting layer.

Numerical study of the light output intensity of the bilayer organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Lu, Feiping

2017-02-01

The structure of organic light-emitting diodes (OLEDs) is one of most important issues that influence the light output intensity (LOI) of OLEDs. In this paper, based on a simple but accurate optical model, the influences of hole and electron transport layer thickness on the LOI of bilayer OLEDs, which with N,N0- bis(naphthalen-1-yl)-N,N0- bis(phenyl)- benzidine (NPB) or N,N'- diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4-diamine (TPD) as hole transport layer, with tris(8-hydroxyquinoline) aluminum (Alq3) as electron transport and light emitting layers, were investigated. The laws of LOI for OLEDs under different organic layer thickness values were obtained. The results show that the LOI of devices varies in accordance with damped cosine or sine function as the increasing of organic layer thickness, and the results show that the bilayer OLEDs with the structure of Glass/ITO/NPB (55 nm)/Alq3 (75 nm)/Al and Glass/ITO/TPB (60 nm)/Alq3 (75 nm)/Al have most largest LOI. When the thickness of Alq3 is less than 105 nm, the OLEDs with TPD as hole transport layer have larger LOI than that with NPB as hole transport layer. The results obtained in this paper can present an in-depth understanding of the working mechanism of OLEDs and help ones fabricate high efficiency OLEDs.

Staging of Macular Telangiectasia: Power-Doppler Optical Coherence Tomography and Macular Pigment Optical Density

PubMed Central

Chin, Eric K.; Kim, Dae Yu; Hunter, Allan A.; Pilli, Suman; Wilson, Machelle; Zawadzki, Robert J.; Werner, John S.; Park, Susanna S.

2013-01-01

Purpose. Two methods were used to study the stages of macular telangiectasia (MacTel): Power-Doppler optical coherence tomography (PD-OCT), which allows imaging of the retinal circulation in three dimensions, and macular pigment optical density (MPOD), which quantifies the distribution of macular carotenoids. Methods. Among 49 patients with MacTel identified, 12 eyes (6 patients) with MacTel and 7 age-matched control eyes (7 patients) were imaged with a custom-built Fourier-domain OCT instrument to acquire PD-OCT images. MPOD was measured using heterochromatic flicker photometry in 10 eyes (5 patients) with MacTel and compared with 44 age-matched control eyes (44 patients). Clinical staging of MacTel was based on best-corrected visual acuity, fundus biomicroscopy, fluorescein angiography, and OCT. Results. Stage 1 eyes (n = 2) had subtle punctate vascular signal confined to the inner portion of the outer plexiform layer (OPL) on PD-OCT. Stage 2 (n = 2) showed larger oblique vascular signal extending into deeper OPL. Stage 3 (n = 5) had disruption of outer retinal layers with abnormal vasculature extending into the outer nuclear layer. Stage 4 (n = 3) showed diffuse blurring of the retinal layers with vascular channels extending the full thickness of the retina. MPOD values in four eyes with stage 1 or 2 MacTel correlated well with age-matched controls. Six eyes with stage 3 or 4 MacTel had loss of MPOD especially at the fovea. Conclusions. PD-OCT shows penetration of the retinal capillaries into the deeper retinal layers in early stages of MacTel, with full thickness vascular proliferation in advanced disease. MPOD is commonly depleted but may appear normal in early stage MacTel. PMID:23716628

Antireflection coatings with SiOx-TiO2 multilayer structures

NASA Astrophysics Data System (ADS)

Lu, Jong-Hong; Luo, Jen-Wei; Chuang, Shiou-Ruei; Chen, Bo-Ying

2014-11-01

In this study, we used SiOx-TiO2 multilayer antireflective coatings to achieve optical average transmittances of 94.93 and 98.07% for one-sided and double-sided coatings on a glass substrate, respectively. A SiOx film was employed as the material with a low refractive index and a TiO2 film as the material with a high refractive index. Results showed that when any layer thickness of the SiOx-TiO2 nano-multilayer (NML) structure is much less than the wavelength of visible light, the SiOx-TiO2 thickness ratio can be used to adjust the optical refractive index of the entire NML film. In this study, we produced dense antireflective coatings of three layers (SiOx, TiO2, and SiOx-TiO2 NML/glass substrate) and four layers (SiOx, TiO2, SiOx, and TiO2/glass substrate) with film thicknesses and refractive indices controlled by reactive magnetron sputtering. Thermal treatment at 600 °C in an air atmosphere was also shown to reduce the absorption of visible light, resolving the issue of degraded transparency caused by increasing sputtering speed. The microhardness of the antireflective film was 8.44 GPa, similar to that of the glass substrate. Process window analysis demonstrated the feasibility of the antireflective coating process window from an engineering standpoint. The thickness of the film deviated by less than 10% from the ideal thickness, corresponding to a 98% transmittance range, and the simulation and experimental results were relatively consistent.

The optical response of monolayer, few-layer and bulk tungsten disulfide.

PubMed

Molas, Maciej R; Nogajewski, Karol; Slobodeniuk, Artur O; Binder, Johannes; Bartos, Miroslav; Potemski, Marek

2017-09-14

We present a comprehensive optical study of thin flakes of tungsten disulfide (WS 2 ) with thickness ranging from mono- to octalayer and in the bulk limit. It is shown that the optical band-gap absorption of monolayer WS 2 is governed by competing resonances arising from one neutral and two distinct negatively charged excitons whose contributions to the overall absorption of light vary as a function of temperature and carrier concentration. The photoluminescence response of monolayer WS 2 is found to be largely dominated by disorder/impurity- and/or phonon-assisted recombination processes. The indirect band-gap luminescence in multilayer WS 2 turns out to be a phonon-mediated process whose energy evolution with the number of layers surprisingly follows a simple model of a two-dimensional confinement. The energy position of the direct band-gap response (A and B resonances) is only weakly dependent on the layer thickness, which underlines an approximate compensation of the effect of the reduction of the exciton binding energy by the shrinkage of the apparent band gap. The A-exciton absorption-type spectra in multilayer WS 2 display a non-trivial fine structure which results from the specific hybridization of the electronic states in the vicinity of the K-point of the Brillouin zone. The effects of temperature on the absorption-like and photoluminescence spectra of various WS 2 layers are also quantified.

Boundary layers in cataclysmic variables - The HEAO 1 X-ray constraints

NASA Technical Reports Server (NTRS)

Jensen, K. A.

1984-01-01

The predictions of the boundary layer model for the X-ray emission from novae are summarized. A discrepancy between observations and theory in the X-ray observations is found. Constraints on the nature of the boundary layers in novae, based on the lack of detections of novae in the HEAO-1 soft X-ray survey are provided. Temperature and column densities for optically thick boundary layers in novae are estimated. Previously announced in STAR as N84-13046

Observation of enhanced infrared absorption in silicon supersaturated with gold by pulsed laser melting of nanometer-thick gold films

NASA Astrophysics Data System (ADS)

Chow, Philippe K.; Yang, Wenjie; Hudspeth, Quentin; Lim, Shao Qi; Williams, Jim S.; Warrender, Jeffrey M.

2018-04-01

We demonstrate that pulsed laser melting (PLM) of thin 1, 5, and 10 nm-thick vapor-deposited gold layers on silicon enhances its room-temperature sub-band gap infrared absorption, as in the case of ion-implanted and PLM-treated silicon. The former approach offers reduced fabrication complexity and avoids implantation-induced lattice damage compared to ion implantation and pulsed laser melting, while exhibiting comparable optical absorptance. We additionally observed strong broadband absorptance enhancement in PLM samples made using 5- and 10-nm-thick gold layers. Raman spectroscopy and Rutherford backscattering analysis indicate that such an enhancement could be explained by absorption by a metastable, disordered and gold-rich surface layer. The sheet resistance and the diode electrical characteristics further elucidate the role of gold-supersaturation in silicon, revealing the promise for future silicon-based infrared device applications.

SnO2 epitaxial films with varying thickness on c-sapphire: Structure evolution and optical band gap modulation

NASA Astrophysics Data System (ADS)

Zhang, Mi; Xu, Maji; Li, Mingkai; Zhang, Qingfeng; Lu, Yinmei; Chen, Jingwen; Li, Ming; Dai, Jiangnan; Chen, Changqing; He, Yunbin

2017-11-01

A series of a-plane SnO2 films with thickness between 2.5 nm and 1436 nm were grown epitaxially on c-sapphire by pulsed laser deposition (PLD), to allow a detailed probe into the structure evolution and optical band gap modulation of SnO2 with growing thickness. All films exhibit excellent out-of-plane ordering (lowest (200) rocking-curve half width ∼0.01°) with an orientation of SnO2(100) || Al2O3(0001), while three equivalent domains that are rotated by 120° with one another coexist in-plane with SnO2[010] || Al2O3 [11-20]. Initially the SnO2(100) film assumes a two-dimensional (2D) layer-by-layer growth mode with atomically smooth surface (minimum root-mean-square roughness of 0.183 nm), and endures compressive strain along both c and a axes as well as mild tensile strain along the b-axis. With increasing thickness, transition from the 2D to 3D island growth mode takes place, leading to formation of various defects to allow relief of the stress and thus relaxation of the film towards bulk SnO2. More interestingly, with increasing thickness from nm to μm, the SnO2 films present a non-monotonic V-shaped variation in the optical band gap energy. While the band gap of SnO2 films thinner than 6.1 nm increases rapidly with decreasing film thickness due to the quantum size effect, the band gap of thicker SnO2 films broadens almost linearly with increasing film thickness up to 374 nm, as a result of the strain effect. The present work sheds light on future design of SnO2 films with desired band gap for particular applications by thickness control and strain engineering.

Organic solar cells using a ZnO/Cu/ZnO anode deposited by ion beam sputtering at room temperature for flexible devices.

PubMed

El Hajj, Ahmad; Lucas, Bruno; Barbot, Anthony; Antony, Rémi; Ratier, Bernard; Aldissi, Matt

2013-07-01

The development of indium-free transparent conductive oxides (TCOs) on polymer substrates for flexible devices requires deposition at low temperatures and a limited thermal treatment. In this paper, we investigated the optical and electrical properties of ZnO/Cu/ZnO multi-layer electrodes obtained by ion beam sputtering at room temperature for flexible optoelectronic devices. This multilayer structure has the advantage of adjusting the layer thickness to favor antireflection and surface plasmon resonance of the metallic layer. We found that the optimal electrode is made up of a 10 nm-thick Cu layer between two 40 nm-thick ZnO layers, which results in a sheet resistance of 12 omega/(see symbol), a high transmittance of 85% in the visible range, and the highest figure of merit of 5.4 x 10(-3) (see symbol)/omega. A P3HT:PCBM-based solar cell showed a power conversion efficiency (PCE) of 2.26% using the optimized ZnO (40 nm)/Cu (10 nm)/ZnO (40 nm) anode.

Surface roughness of Saturn's rings and ring particles inferred from thermal phase curves

NASA Astrophysics Data System (ADS)

Morishima, Ryuji; Turner, Neal J.; Spilker, Linda

2017-10-01

We analyze thermal phase curves of all the main rings of Saturn (the A, B, C rings, and the Cassini division) measured by both the far-IR and mid-IR detectors of the Cassini Composite InfraRed Spectrometer (CIRS). All the rings show temperature increases toward zero phase angle, known as an opposition effect or thermal beaming. For the C ring and Cassini division, which have low optical depths, intra-particle shadowing is considered the dominant mechanism causing the effect. On the other hand, the phase curves of the optically thick B and A rings steepen significantly with decreasing absolute solar elevation angle from 21° to 14°, suggesting inter-particle shadowing plays an important role in these rings. We employ an analytic roughness model to estimate the degrees of surface roughness of the rings or ring particles. For optically thin rings, an isolated particle covered by spherical segment craters is employed while for the thick rings we approximate a packed particle layer as a slab covered by craters. The particles in the thin rings are found to have generally rough surfaces, except in the middle C ring. Across the C ring, the optical depth correlates with the degree of surface roughness. This may indicate that surface roughness comes mainly from particle clumping, while individual particles have rather smooth surfaces. For the optically thick rings, the surface roughness of the particle layer is found to be moderate. The modeled phase curves of optically thick rings are shallow if the phase angle change is primarily due to change of observer azimuthal angle. On the other hand, the phase curves are steep if the phase angle change is due to change of observer elevation angle, as inter-particle shadows become visible at higher observer elevation. In addition, the area of shadowed facets increases with decreasing solar elevation angle. These combined effects explain the large seasonal change of the phase curve steepness observed for the thick rings. The degrees of surface roughness inferred from the thermal phase curves are generally less than those from the phase curves in visible light. This is probably explained by different roughness scales seen in thermal and visible light.

Hybrid ZnO/phthalocyanine photovoltaic device with highly resistive ZnO intermediate layer.

PubMed

Izaki, Masanobu; Chizaki, Ryo; Saito, Takamasa; Murata, Kazufumi; Sasano, Junji; Shinagawa, Tsutomu

2013-10-09

We report a hybrid photovoltaic device composed of a 3.3 eV bandgap zinc oxide (ZnO) semiconductor and metal-free phthalocyanine layers and the effects of the insertion of the highly resistive ZnO buffer layer on the electrical characteristics of the rectification feature and photovoltaic performance. The hybrid photovoltaic devices have been constructed by electrodeposition of the 300 nm thick ZnO layer in a simple zinc nitrate aqueous solution followed by vacuum evaporation of 50-400 nm thick-phthalocyanine layers. The ZnO layers with the resistivity of 1.8 × 10(3) and 1 × 10(8) Ω cm were prepared by adjusting the cathodic current density and were installed into the hybrid photovoltaic devices as the n-type and buffer layer, respectively. The phthalocyanine layers with the characteristic monoclinic lattice showed a characteristic optical absorption feature regardless of the thickness, but the preferred orientation changed depending on the thickness. The ZnO buffer-free hybrid 50 nm thick phthalocyanine/n-ZnO photovoltaic device showed a rectification feature but possessed a poor photovoltaic performance with a conversion efficiency of 7.5 × 10(-7) %, open circuit voltage of 0.041 V, and short circuit current density of 8.0 × 10(-5) mA cm(-2). The insertion of the ZnO buffer layer between the n-ZnO and phthalocyanine layers induced improvements in both the rectification feature and photovoltaic performance. The excellent rectification feature with a rectification ratio of 3188 and ideally factor of 1.29 was obtained for the hybrid 200 nm thick phthalocyanine/ZnO buffer/n-ZnO photovoltaic device, and the hybrid photovoltaic device possessed an improved photovoltaic performance with the conversion efficiency of 0.0016%, open circuit voltage of 0.31 V, and short circuit current density of 0.015 mA cm(-2).

Using iridium films to compensate for piezo-electric materials processing stresses in adjustable x-ray optics

NASA Astrophysics Data System (ADS)

Ames, A.; Bruni, R.; Cotroneo, V.; Johnson-Wilke, R.; Kester, T.; Reid, P.; Romaine, S.; Tolier-McKinstry, S.; Wilke, R. H. T.

2015-09-01

Adjustable X-ray optics represent a potential enabling technology for simultaneously achieving large effective area and high angular resolution for future X-ray Astronomy missions. The adjustable optics employ a bimorph mirror composed of a thin (1.5 μm) film of piezoelectric material deposited on the back of a 0.4 mm thick conical mirror segment. The application of localized electric fields in the piezoelectric material, normal to the mirror surface, result in localized deformations in mirror shape. Thus, mirror fabrication and mounting induced figure errors can be corrected, without the need for a massive reaction structure. With this approach, though, film stresses in the piezoelectric layer, resulting from deposition, crystallization, and differences in coefficient of thermal expansion, can distort the mirror. The large relative thickness of the piezoelectric material compared to the glass means that even 100MPa stresses can result in significant distortions. We have examined compensating for the piezoelectric processing related distortions by the deposition of controlled stress chromium/iridium films on the front surface of the mirror. We describe our experiments with tuning the product of the chromium/iridium film stress and film thickness to balance that resulting from the piezoelectric layer. We also evaluated the repeatability of this deposition process, and the robustness of the iridium coating.

Optical and electrical properties of Mn1.56Co0.96Ni0.48O4 thin films

NASA Astrophysics Data System (ADS)

Gao, Y. Q.; Huang, Z. M.; Hou, Y.; Wu, J.; Chu, J. H.

2013-12-01

Mn1.56Co0.96Ni0.48O4 (MCN) films with different layers have been prepared on Al2O3 substrate by chemical solution deposition method. The microstructures, optical and electrical properties of the films are investigated. X-ray diffraction and microstructure analyses show good crystallization and both the crystalline quality and the grain size are improved with the increasing thickness of the films. Mid-infrared optical properties of MCN films have been investigated using transmission spectra. The results show the red shift of absorption with the increasing film thickness and the energy gap Eg decrease from 0.6422 eV to 0.6354 eV. All the MCN films show an exponential decrease in the resistivity with increasing temperature within the measured range. The temperature dependence resistivity can be described by the small polarons hopping model. Using this model, the characteristic temperature T0 and activation energy E of the MCN films were derived. With the film thickness increase, the T0 and E of the MCN films increase. The calculated room temperature coefficient of resistance (TCR) of MCN film with 100 layers is -3.5% K-1. The MCN films showed appropriate resistance and high value of TCR, these advantages make them very preponderant for thermal sensors.

Wavelength dependence of polarization. XXXX. Venus upper atmosphere aerosol layers from polarimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santer, R.; Dollfus, A.

1980-06-01

Previous photometric and polarimetric observations of Venus have indicated the presence of a thin layer of small particles above the usual cloud layers. We sensed some characteristics of this upper layer on the basis of the Meudon and Pic-du-Midi regional polarization survey, covering from 1950 to 1972. Optical thicknesses of the order of several percent with particle radii of around 0.2 ..mu..m are indicated. The refraction index is not known. Although this layer is apparently globally permanent, variations occur regionally and with time.

Comprehensive Three-Dimensional Analysis of the Neuroretinal Rim in Glaucoma Using High-Density Spectral-Domain Optical Coherence Tomography Volume Scans

PubMed Central

Tsikata, Edem; Lee, Ramon; Shieh, Eric; Simavli, Huseyin; Que, Christian J.; Guo, Rong; Khoueir, Ziad; de Boer, Johannes; Chen, Teresa C.

2016-01-01

Purpose To describe spectral-domain optical coherence tomography (OCT) methods for quantifying neuroretinal rim tissue in glaucoma and to compare these methods to the traditional retinal nerve fiber layer thickness diagnostic parameter. Methods Neuroretinal rim parameters derived from three-dimensional (3D) volume scans were compared with the two-dimensional (2D) Spectralis retinal nerve fiber layer (RNFL) thickness scans for diagnostic capability. This study analyzed one eye per patient of 104 glaucoma patients and 58 healthy subjects. The shortest distances between the cup surface and the OCT-based disc margin were automatically calculated to determine the thickness and area of the minimum distance band (MDB) neuroretinal rim parameter. Traditional 150-μm reference surface–based rim parameters (volume, area, and thickness) were also calculated. The diagnostic capabilities of these five parameters were compared with RNFL thickness using the area under the receiver operating characteristic (AUROC) curves. Results The MDB thickness had significantly higher diagnostic capability than the RNFL thickness in the nasal (0.913 vs. 0.818, P = 0.004) and temporal (0.922 vs. 0.858, P = 0.026) quadrants and the inferonasal (0.950 vs. 0.897, P = 0.011) and superonasal (0.933 vs. 0.868, P = 0.012) sectors. The MDB area and the three neuroretinal rim parameters based on the 150-μm reference surface had diagnostic capabilities similar to RNFL thickness. Conclusions The 3D MDB thickness had a high diagnostic capability for glaucoma and may be of significant clinical utility. It had higher diagnostic capability than the RNFL thickness in the nasal and temporal quadrants and the inferonasal and superonasal sectors. PMID:27768203

Few-layer 1T‧ MoTe2 as gapless semimetal with thickness dependent carrier transport

NASA Astrophysics Data System (ADS)

Song, Peng; Hsu, Chuanghan; Zhao, Meng; Zhao, Xiaoxu; Chang, Tay-Rong; Teng, Jinghua; Lin, Hsin; Loh, Kian Ping

2018-07-01

Semimetal MoTe2 can be a type II Weyl semimetal in the bulk, but monolayer of this material is predicted to be quantum spin hall insulators. This dramatic change in electronic properties with number of layers is an excellent example of the dimensional effects of quantum transport. However, a detailed experimental study of the carrier transport and band structure of ultrathin semimetal MoTe2 is lacking so far. We performed magneto-transport measurements to study the conduction behavior and quantum phase coherence of 1T‧ MoTe2 as a function of its thickness. We show that due to a unique two-band transport mechanism (synergetic contribution from electron conduction and hole conduction), the conduction behavior of 1T‧ MoTe2 changes from metallic to p-type unipolar, and finally to ambipolar as the thickness decreases, suggesting that this effect can be used in devices by effectively controlling the thickness. Our transport studies, optical measurements and first-principles electronic structure calculations reveal that 1T‧ MoTe2 remains gapless down to a few (~2–3) layers. Despite being gapless, 1T‧ MoTe2 exhibits metal-insulator transition at 3-layer thickness, due to enhanced carrier localization effect.

Evaluation of the Ganglion Cell Complex and Retinal Nerve Fiber Layer in Low, Moderate, and High Myopia: A Study by RTVue Spectral Domain Optical Coherence Tomography.

PubMed

Sezgin Akcay, Betul Ilkay; Gunay, Betul Onal; Kardes, Esra; Unlu, Cihan; Ergin, Ahmet

2017-01-01

To assess the effect of low, moderate, and high myopia on the thickness of the retinal nerve fiber layer (RNFL) and Ganglion cell complex (GCC) measured by Spectral Domain Optical Coherence Tomography (SD-OCT) in non-glaucomatous subjects. The subjects were divided into three groups: low (n = 81, 35.6%), moderate (n = 79, 34.8%), and highly myopic eyes (n = 67, 29.5%). The RNFL thickness profile, including the average, superior, nasal, inferior, and temporal quadrant and each of the eight directional thicknesses, was measured. GCC parameters, including the average, superior, and inferior values, the focal loss volume (FLV), and the global loss volume (GLV), were measured. The correlation between the OCT measurements and the axial length was evaluated. The average, superior, inferior, and nasal RNFL thicknesses of low and moderate myopic eyes were found to be significantly higher than those of highly myopic eyes. The temporal RNFL thicknesses were not different among the three groups. The average, superior, and inferior ganglion cell complex values of low and moderate myopic eyes were significantly higher than those of highly myopic eyes. The FLV and GLV of low and moderate myopic eyes were significantly higher than those of highly myopic eyes (p = 0.001 for all). In the moderate and high myopia groups, the average RNFL thickness and GCC thickness were both negatively correlated with the axial length. Highly myopic subjects tend to have thinner RNFL and GCC thicknesses than subjects with low and moderate myopia.

Retinal nerve fiber layer thickness in normals measured by spectral domain OCT.

PubMed

Bendschneider, Delia; Tornow, Ralf P; Horn, Folkert K; Laemmer, Robert; Roessler, Christopher W; Juenemann, Anselm G; Kruse, Friedrich E; Mardin, Christian Y

2010-09-01

To determine normal values for peripapillary retinal nerve fiber layer thickness (RNFL) measured by spectral domain Optical Coherence Tomography (SOCT) in healthy white adults and to examine the relationship of RNFL with age, gender, and clinical variables. The peripapillary RNFL of 170 healthy patients (96 males and 74 females, age 20 to 78 y) was imaged with a high-resolution SOCT (Spectralis HRA+OCT, Heidelberg Engineering) in an observational cross-sectional study. RNFL thickness was measured around the optic nerve head using 16 automatically averaged, consecutive circular B-scans with 3.4-mm diameter. The automatically segmented RNFL thickness was divided into 32 segments (11.25 degrees each). One randomly selected eye per subject entered the study. Mean RNFL thickness in the study population was 97.2 ± 9.7 μm. Mean RNFL thickness was significantly negatively correlated with age (r = -0.214, P = 0.005), mean RNFL decrease per decade was 1.90 μm. As age dependency was different in different segments, age-correction of RNFL values was made for all segments separately. Age-adjusted RNFL thickness showed a significant correlation with axial length (r = -0.391, P = 0.001) and with refractive error (r = 0.396, P<0.001), but not with disc size (r = 0.124). Normal RNFL results with SOCT are comparable to those reported with time-domain OCT. In accordance with the literature on other devices, RNFL thickness measured with SOCT was significantly correlated with age and axial length. For creating a normative database of SOCT RNFL values have to be age adjusted.

Structural and functional correlates in color vision deficiency

PubMed Central

Gupta, A; Laxmi, G; Nittala, M G; Raman, R

2011-01-01

Purpose The aim of this study is to assess the photoreceptor integrity, using spectral domain optical coherence tomography (SD-OCT), and to measure the retinal sensitivity of patients with congenital red–green color vision deficiency (CVD). Methods In all, 14 eyes from 7 patients with congenital red–green CVD (diagnosed by Farnsworth Munsell 100 hue test), and 14 eyes from 7 control subjects were examined by SD-OCT and microperimetry. Radial scans (7-mm) were taken of the macula. The center of the fovea was defined. The thickness of different retinal layers, at the foveal center, and at multiple defined points along all six radial scans, was measured. The median readings were compared between the two groups using Mann–Whitney U-test. Results SD-OCT demonstrated normal total retinal thickness, normal thickness of the photoreceptor layer, normal thickness of the outer nuclear layer, normal vertical thickness of the outer segments (OSs), and normal vertical thickness of the inner segments. OS horizontal diameter was less in left eye in cases with CVD when compared with controls. The mean retinal and foveal sensitivity was similar between cases and controls. Conclusions In subjects with congenital red–green CVD, there are no discernible anatomical abnormalities seen on SD-OCT in various retinal layers, except for a narrower foveal pit. However, further studies with larger sample size are required. PMID:21494280

The study of genomic DNA adsorption and subsequent interactions using total internal reflection ellipsometry.

PubMed

Nabok, Alexei; Tsargorodskaya, Anna; Davis, Frank; Higson, Séamus P J

2007-10-31

The adsorption of genomic DNA and subsequent interactions between adsorbed and solvated DNA was studied using a novel sensitive optical method of total internal reflection ellipsometry (TIRE), which combines spectroscopic ellipsometry with surface plasmon resonance (SPR). Single strands of DNA of two species of fish (herring and salmon) were electrostatically adsorbed on top of polyethylenimine films deposited upon gold coated glass slides. The ellipsometric spectra were recorded and data fitting utilized to extract optical parameters (thickness and refractive index) of adsorbed DNA layers. The further adsorption of single stranded DNA from an identical source, i.e. herring ss-DNA on herring ss-DNA or salmon ss-DNA on salmon ss-DNA, on the surface was observed to give rise to substantial film thickness increases at the surface of about 20-21 nm. Conversely adsorption of DNA from alternate species, i.e. salmon ss-DNA on herring ss-DNA or herring ss-DNA on salmon ss-DNA, yielded much smaller changes in thickness of 3-5 nm. AFM studies of the surface roughness of adsorbed layers were in line with the TIRE data.

Cloud Optical Depth Retrievals from Solar Background "signal" of Micropulse Lidars

NASA Technical Reports Server (NTRS)

Chiu, J. Christine; Marshak, A.; Wiscombe, W.; Valencia, S.; Welton, E. J.

2007-01-01

Pulsed lidars are commonly used to retrieve vertical distributions of cloud and aerosol layers. It is widely believed that lidar cloud retrievals (other than cloud base altitude) are limited to optically thin clouds. Here we demonstrate that lidars can retrieve optical depths of thick clouds using solar background light as a signal, rather than (as now) merely a noise to be subtracted. Validations against other instruments show that retrieved cloud optical depths agree within 10-15% for overcast stratus and broken clouds. In fact, for broken cloud situations one can retrieve not only the aerosol properties in clear-sky periods using lidar signals, but also the optical depth of thick clouds in cloudy periods using solar background signals. This indicates that, in general, it may be possible to retrieve both aerosol and cloud properties using a single lidar. Thus, lidar observations have great untapped potential to study interactions between clouds and aerosols.

Mechanical Behavior of Al-SiC Nanolaminate Composites Using Micro-Scale Testing Methods

NASA Astrophysics Data System (ADS)

Mayer, Carl Randolph

Nanolaminate composite materials consist of alternating layers of materials at the nanoscale (≤100 nm). Due to the nanometer scale thickness of their layers, these materials display unique and tailorable properties. This enables us to alter both mechanical attributes such as strength and wear properties, as well as functional characteristics such as biocompatibility, optical, and electronic properties. This dissertation focuses on understanding the mechanical behavior of the Al-SiC system. From a practical perspective, these materials exhibit a combination of high toughness and strength which is attractive for many applications. Scientifically, these materials are interesting due to the large elastic modulus mismatch between the layers. This, paired with the small layer thickness, allows a unique opportunity for scientists to study the plastic deformation of metals under extreme amounts of constraint. Previous studies are limited in scope and a more diverse range of mechanical characterization is required to understand both the advantages and limitations of these materials. One of the major challenges with testing these materials is that they are only able to be made in thicknesses on the order of micrometers so the testing methods are limited to small volume techniques. This work makes use of both microscale testing techniques from the literature as well as novel methodologies. Using these techniques we are able to gain insight into aspects of the material's mechanical behavior such as the effects of layer orientation, flaw dependent fracture, tension-compression asymmetry, fracture toughness as a function of layer thickness, and shear behavior as a function of layer thickness.

Polarization and Thickness Dependent Absorption Properties of Black Phosphorus: New Saturable Absorber for Ultrafast Pulse Generation

PubMed Central

Li, Diao; Jussila, Henri; Karvonen, Lasse; Ye, Guojun; Lipsanen, Harri; Chen, Xianhui; Sun, Zhipei

2015-01-01

Black phosphorus (BP) has recently been rediscovered as a new and interesting two-dimensional material due to its unique electronic and optical properties. Here, we study the linear and nonlinear optical properties of BP flakes. We observe that both the linear and nonlinear optical properties are anisotropic and can be tuned by the film thickness in BP, completely different from other typical two-dimensional layered materials (e.g., graphene and the most studied transition metal dichalcogenides). We then use the nonlinear optical properties of BP for ultrafast (pulse duration down to ~786 fs in mode-locking) and large-energy (pulse energy up to >18 nJ in Q-switching) pulse generation in fiber lasers at the near-infrared telecommunication band ~1.5 μm. We observe that the output of our BP based pulsed lasers is linearly polarized (with a degree-of-polarization ~98% in mode-locking, >99% in Q-switching, respectively) due to the anisotropic optical property of BP. Our results underscore the relatively large optical nonlinearity of BP with unique polarization and thickness dependence, and its potential for polarized optical pulse generation, paving the way to BP based nonlinear and ultrafast photonic applications (e.g., ultrafast all-optical polarization switches/modulators, frequency converters etc.). PMID:26514090

Flexible Silk-Inorganic Nanocomposites: From Transparent to Highly Reflective

DTIC Science & Technology

2010-02-16

assembly. The organized assembly of the silk fibroin with clay ( montmorillonite ) nanosheets results in highly transparent nanoscale films with...mechanical and optical properties of the nanocomposites. For that purpose we utilized individually dispersed, aluminosilicate layers of montmorillonite (MMT...to the thickness of an individual aluminosilicate layer of montmorillonite ,[43] and indicates that monolayer formation occurs upon adsorption (Fig. 2a

Poly-SiGe MEMS actuators for adaptive optics

NASA Astrophysics Data System (ADS)

Lin, Blake C.; King, Tsu-Jae; Muller, Richard S.

2006-01-01

Many adaptive optics (AO) applications require mirror arrays with hundreds to thousands of segments, necessitating a CMOS-compatible MEMS process to integrate the mirrors with their driving electronics. This paper proposes a MEMS actuator that is fabricated using low-temperature polycrystalline silicon-germanium (poly-SiGe) surface-micromaching technology (total thermal budget is 6 hours at or below 425°C). The MEMS actuator consists of three flexures and a hexagonal platform, on which a micromirror is to be assembled. The flexures are made of single-layer poly-SiGe with stress gradient across thickness of the film, making them bend out-of-plane after sacrificial-layer release to create a large nominal gap. The platform, on the other hand, has an additional stress-balancing SiGe layer deposited on top, making the dual-layer stack stay flat after release. Using this process, we have successfully fabricated the MEMS actuator which is lifted 14.6 μm out-of-plane by 290-μm-long flexures. The 2-μm-thick hexagonal mirror-platform exhibits a strain gradient of -5.5×10 -5 μm -1 (equivalent to 18 mm radius-of-curvature), which would be further reduced once the micromirror is assembled.

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

PubMed

Wang, Qing Hua; Kalantar-Zadeh, Kourosh; Kis, Andras; Coleman, Jonathan N; Strano, Michael S

2012-11-01

The remarkable properties of graphene have renewed interest in inorganic, two-dimensional materials with unique electronic and optical attributes. Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickness. Although TMDCs have been studied for decades, recent advances in nanoscale materials characterization and device fabrication have opened up new opportunities for two-dimensional layers of thin TMDCs in nanoelectronics and optoelectronics. TMDCs such as MoS(2), MoSe(2), WS(2) and WSe(2) have sizable bandgaps that change from indirect to direct in single layers, allowing applications such as transistors, photodetectors and electroluminescent devices. We review the historical development of TMDCs, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.

Directional Emission from Metal-Dielectric-Metal Structures: Effect of Mixed Metal Layers, Dye Location and Dielectric Thickness.

PubMed

Choudhury, Sharmistha Dutta; Badugu, Ramachandram; Ray, Krishanu; Lakowicz, Joseph R

2015-02-12

Metal-dielectric-metal (MDM) structures provide directional emission close to the surface normal, which offers opportunities for new design formats in fluorescence based applications. The directional emission arises due to near-field coupling of fluorophores with the optical modes present in the MDM substrate. Reflectivity simulations and dispersion diagrams provide a basic understanding of the mode profiles and the factors that affect the coupling efficiency and the spatial distribution of the coupled emission. This work reveals that the composition of the metal layers, the location of the dye in the MDM substrate and the dielectric thickness are important parameters that can be chosen to tune the color of the emission wavelength, the angle of observation, the angular divergence of the emission and the polarization of the emitted light. These features are valuable for displays and optical signage.

Directional Emission from Metal-Dielectric-Metal Structures: Effect of Mixed Metal Layers, Dye Location and Dielectric Thickness

PubMed Central

Choudhury, Sharmistha Dutta; Badugu, Ramachandram; Ray, Krishanu; Lakowicz, Joseph R.

2015-01-01

Metal-dielectric-metal (MDM) structures provide directional emission close to the surface normal, which offers opportunities for new design formats in fluorescence based applications. The directional emission arises due to near-field coupling of fluorophores with the optical modes present in the MDM substrate. Reflectivity simulations and dispersion diagrams provide a basic understanding of the mode profiles and the factors that affect the coupling efficiency and the spatial distribution of the coupled emission. This work reveals that the composition of the metal layers, the location of the dye in the MDM substrate and the dielectric thickness are important parameters that can be chosen to tune the color of the emission wavelength, the angle of observation, the angular divergence of the emission and the polarization of the emitted light. These features are valuable for displays and optical signage. PMID:25844110

Growth of low temperature silicon nano-structures for electronic and electrical energy generation applications.

PubMed

Gabrielyan, Nare; Saranti, Konstantina; Manjunatha, Krishna Nama; Paul, Shashi

2013-02-15

This paper represents the lowest growth temperature for silicon nano-wires (SiNWs) via a vapour-liquid-solid method, which has ever been reported in the literature. The nano-wires were grown using plasma-enhanced chemical vapour deposition technique at temperatures as low as 150°C using gallium as the catalyst. This study investigates the structure and the size of the grown silicon nano-structure as functions of growth temperature and catalyst layer thickness. Moreover, the choice of the growth temperature determines the thickness of the catalyst layer to be used.The electrical and optical characteristics of the nano-wires were tested by incorporating them in photovoltaic solar cells, two terminal bistable memory devices and Schottky diode. With further optimisation of the growth parameters, SiNWs, grown by our method, have promising future for incorporation into high performance electronic and optical devices.

Growth of low temperature silicon nano-structures for electronic and electrical energy generation applications

PubMed Central

2013-01-01

This paper represents the lowest growth temperature for silicon nano-wires (SiNWs) via a vapour-liquid–solid method, which has ever been reported in the literature. The nano-wires were grown using plasma-enhanced chemical vapour deposition technique at temperatures as low as 150°C using gallium as the catalyst. This study investigates the structure and the size of the grown silicon nano-structure as functions of growth temperature and catalyst layer thickness. Moreover, the choice of the growth temperature determines the thickness of the catalyst layer to be used. The electrical and optical characteristics of the nano-wires were tested by incorporating them in photovoltaic solar cells, two terminal bistable memory devices and Schottky diode. With further optimisation of the growth parameters, SiNWs, grown by our method, have promising future for incorporation into high performance electronic and optical devices. PMID:23413969

Electro-architected porous platinum on metallic multijunction nanolayers to optimize their optical properties for infrared sensor application

NASA Astrophysics Data System (ADS)

Stanca, Sarmiza Elena; Hänschke, Frank; Zieger, Gabriel; Dellith, Jan; Dellith, Andrea; Ihring, Andreas; Belkner, Johannes; Meyer, Hans-Georg

2018-03-01

Tailoring the physicochemical properties of the metallic multijunction nanolayers is a prerequisite for the development of microelectronics. From this perspective, a desired lower reflectance of infrared radiation was achieved by an electrochemical deposition of porous platinum in nonaqueous media on silver mirror supported nickel-chrome and nickel-titanium metallic films with incremental decreasing thicknesses from 80-10 nm. The electro-assembled architectures were examined by means of scanning electron microscopy and Fourier transform infrared spectroscopy and it was observed that the layer and sublayer thicknesses and resistivities have a substantial effect upon the porous platinum morphology and its optical properties. It is here reported that the augmentation of the metallic layer electrical conductivity determines the electroformation of more compact platinum nanolayers. Moreover, the platinum black coating of metallic nanolayers causes a considerable decrease of the reflectance in the region from 1000-8000 cm-1.

In-situ stress measurement of single and multilayer thin-films used in x-ray astronomy optics applications

NASA Astrophysics Data System (ADS)

Broadway, David M.; Ramsey, Brian D.; O'Dell, Stephen L.; Gurgew, Danielle

2017-09-01

We present in-situ stress measurement results for single and multilayer thin-films deposited by magnetron sputtering. In particular, we report on the influence of the material interfaces on the ensuing stress in both the transient and steady-state regimes of film growth. This behavior is used to determine the appropriate thicknesses of the constituent layers that will result in a net tensile stress in multilayers composed of various material combinations. These multilayers can then be used to compensate the compressive integrated stress in single and multilayer EUV and x-ray optical coatings. The use of multilayers to compensate the integrated stress might be advantageous because, unlike single layers of chromium, the roughness is not expected to increase with the total thickness of the multilayer. In this paper, we demonstrate the technique for W/Si and Mo/Si multilayers and discuss its application to other material combinations.

On optical imaging through aircraft turbulent boundary layers

NASA Technical Reports Server (NTRS)

Sutton, G. W.

1980-01-01

Optical resolution quality as affected by aircraft turbulent boundary layers is analyzed. Wind-tunnel data was analyzed to obtained the variation of boundary layer turbulence scale length and mass density rms fluctuations with Mach number. The data gave good agreement with a mass density fluctuation turbulence spectrum that is either isotropic of orthogonally anisotropic. The data did not match an isotropic turbulence velocity spectrum which causes an anisotropic non-orthogonal mass density fluctuation spectrum. The results indicate that the average mass density rms fluctuation is about 10% of the maximum mass density across the boundary layer and that the transverse turbulence scale size is about 10% of the boundary layer thickness. The results indicate that the effect of the turbulent boundary layer is large angle scattering which decreases contrast but not resolution. Using extinction as a criteria the range of acceptable aircraft operating conditions are given.

Effect of fabrication parameters on morphological and optical properties of highly doped p-porous silicon

NASA Astrophysics Data System (ADS)

Zare, Maryam; Shokrollahi, Abbas; Seraji, Faramarz E.

2011-09-01

Porous silicon (PS) layers were fabricated by anodization of low resistive (highly doped) p-type silicon in HF/ethanol solution, by varying current density, etching time and HF concentration. Atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM) analyses were used to investigate the physical properties and reflection spectrum was used to investigate the optical behavior of PS layers in different fabrication conditions. Vertically aligned mesoporous morphology is observed in fabricated films and with HF concentration higher than 20%. The dependence of porosity, layer thickness and rms roughness of the PS layer on current density, etching time and composition of electrolyte is also observed in obtained results. Correlation between reflectivity and fabrication parameters was also explored. Thermal oxidation was performed on some mesoporous layers that resulted in changes of surface roughness, mean height and reflectivity of the layers.

Evidence of early ultrastructural photoreceptor abnormalities in light-induced retinal degeneration using spectral domain optical coherence tomography.

PubMed

Aziz, Mehak K; Ni, Aiguo; Esserman, Denise A; Chavala, Sai H

2014-07-01

To study spatiotemporal in vivo changes in retinal morphology and quantify thickness of retinal layers in a mouse model of light-induced retinal degeneration using spectral domain optical coherence tomography (SD-OCT). BALB/c mice were exposed to 5000 lux of constant light for 3 h. SD-OCT images were taken 3 h, 24 h, 3 days, 1 week and 1 month after light exposure and were compared with histology at the same time points. SD-OCT images were also taken at 0, 1 and 2 h after light exposure in order to analyse retinal changes at the earliest time points. The thickness of retinal layers was measured using the Bioptigen software InVivoVue Diver. SD-OCT demonstrated progressive outer retinal thinning. 3 h after light exposure, the outer nuclear layer converted from hyporeflective to hyper-reflective. At 24 h, outer retinal bands and nuclear layer demonstrated similar levels of hyper-reflectivity. Significant variations in outer retinal thickness, vitreous opacities and retinal detachments occurred within days of injury. Thinning of the retina was observed at 1 month after injury. It was also determined that outer nuclear layer changes precede photoreceptor segment structure disintegration and the greatest change in segment structure occurs between 1 and 2 h after light exposure. Longitudinal SD-OCT reveals intraretinal changes that cannot be observed by histopathology at early time points in the light injury model. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Topotactical growth of thick perovskite oxynitride layers by nitridation of single crystalline oxides

NASA Astrophysics Data System (ADS)

Ebbinghaus, Stefan G.; Aguiar, Rosiana; Weidenkaff, Anke; Gsell, Stefan; Reller, Armin

2008-06-01

Thick films of the perovskite-related oxynitrides LaTiO 2N, NdTiO 2N, SrNbO 2N and SrTaO 2N were synthesised by nitridation of single crystals of the corresponding oxides with general composition ABO 3.5. The oxide crystals were obtained by optical floating zone growth. They correspond to n = 4 member of the A nB nO 3 n+2 family of layered perovskites and were reacted at temperatures between 900 °C and 1050 °C to form the oxynitrides. Electron probe microanalysis proved the presence of nitrogen in a surface layer of a few micrometer thickness. Cross-section SEM revealed additional thin stripes of oxynitride within the bulk of the crystals, indicating that nitrogen is incorporated preferably parallel to the perovskite-type layers, which in turn are connected in a zipper-type mechanism. The formation of the desired perovskite-type oxynitrides was confirmed by X-ray diffraction. Pole figure measurements proved an epitaxial orientation ABO 2N (110)[001] ‖ ABO 3.5 (001)[100]. The mosaicity of the oxynitrides both in polar and azimuthal direction was very small (<2°) indicating a nearly single crystalline quality of the surface layer. The nitridation of the crystals results in a dramatic change in colour. Optical spectroscopy revealed shifts of the absorption edge by more than 200 nm to longer wavelengths with respect to the parent oxides, corresponding to a reduction of the band gap energies by 1.4-1.8 eV.

Control of optical properties of metal-dielectric planar plasmonic nanostructures by adjusting their architecture in the case of TiAlN/Ag system

NASA Astrophysics Data System (ADS)

Wainstein, D. L.; Vakhrushev, V. O.; Kovalev, A. I.

2017-05-01

The multilayer Ag/(Ti34Al66)N metal-insulator-metal (MIM) heterostructures with different thicknesses of individual layers varied from several to several hundred nanometers were fabricated by DC-magnetron sputtering on the surfaces of Si single crystal wafers. The coatings structure was determined by STEM. The phase composition and crystallography of individual layers were studied by X-ray diffraction. The reflection indexes were measured in the photons energies range from 1 to 5 eV, or from 1240 to 248 nm. The spectroscopy of plasmon losses and plasmon microscopy allowed us to measure the plasmons losses characteristic energies and their surface distribution. The energies of plasmons peaks and their locations are strongly depending on Ag layers thickness in the MIM nanocomposite. The surface plasmon with energy about 4 eV was observed in the middle of 20 nm Ag layer. The plasmons were localized at the metal/dielectric interface for Ag layers 5 nm and less. The reflectance spectral profiles edges positions at long and short waves are correlated with plasmons energies and features of their spatial distribution. The MIMs based on the TiAlN/Ag can find applications as optical filters, photovoltaic energy conversion devices, etc.

Optimising sulfuric acid hard coat anodising for an Al-Mg-Si wrought aluminium alloy

NASA Astrophysics Data System (ADS)

Bartolo, N.; Sinagra, E.; Mallia, B.

2014-06-01

This research evaluates the effects of sulfuric acid hard coat anodising parameters, such as acid concentration, electrolyte temperature, current density and time, on the hardness and thickness of the resultant anodised layers. A small scale anodising facility was designed and set up to enable experimental investigation of the anodising parameters. An experimental design using the Taguchi method to optimise the parameters within an established operating window was performed. Qualitative and quantitative methods of characterisation of the resultant anodised layers were carried out. The anodised layer's thickness, and morphology were determined using a light optical microscope (LOM) and field emission gun scanning electron microscope (FEG-SEM). Hardness measurements were carried out using a nano hardness tester. Correlations between the various anodising parameters and their effect on the hardness and thickness of the anodised layers were established. Careful evaluation of these effects enabled optimum parameters to be determined using the Taguchi method, which were verified experimentally. Anodised layers having hardness varying between 2.4-5.2 GPa and a thickness of between 20-80 μm were produced. The Taguchi method was shown to be applicable to anodising. This finding could facilitate on-going and future research and development of anodising, which is attracting remarkable academic and industrial interest.

Organic Light-Emitting Diodes with a Perylene Interlayer Between the Electrode-Organic Interface

NASA Astrophysics Data System (ADS)

Saikia, Dhrubajyoti; Sarma, Ranjit

2018-01-01

The performance of an organic light-emitting diode (OLED) with a vacuum-deposited perylene layer over a fluorine-doped tin oxide (FTO) surface is reported. To investigate the effect of the perylene layer on OLED performance, different thicknesses of perylene are deposited on the FTO surface and their current density-voltages (J-V), luminance-voltages (L-V) and device efficiency characteristics at their respective thickness are studied. Further analysis is carried out with an UV-visible light double-beam spectrophotometer unit, a four-probe resistivity unit and a field emission scanning electron microscope set up to study the optical transmittance, sheet resistance and surface morphology of the bilayer anode film. We used N,N'-bis(3-methyl phenyl)- N,N'(phenyl)-benzidine (TPD) as the hole transport layer, Tris(8-hydroxyquinolinato)aluminum (Alq3) as a light-emitting layer and lithium fluoride as an electron injection layer. The luminance efficiency of an OLED structure with a 9-nm-thick perylene interlayer is increased by 2.08 times that of the single-layer FTO anode OLED. The maximum value of current efficiency is found to be 5.25 cd/A.

Electrical investigations of hybrid OLED microcavity structures with novel encapsulation methods

NASA Astrophysics Data System (ADS)

Meister, Stefan; Brückner, Robert; Fröb, Hartmut; Leo, Karl

2016-04-01

An electrical driven organic solid state laser is a very challenging goal which is so far well beyond reach. As a step towards realization, we monolithically implemented an Organic Light Emitting Diode (OLED) into a dielectric, high quality microcavity (MC) consisting of two Distributed Bragg Reectors (DBR). In order to account for an optimal optical operation, the OLED structure has to be adapted. Furthermore, we aim to excite the device not only electrically but optically as well. Different OLED structures with an emission layer consisting of Alq3:DCM (2 wt%) were investigated. The External Quantum Efficiencies (EQE) of this hybrid structures are in the range of 1-2 %, as expected for this material combination. Including metal layers into a MC is complicated and has a huge impact on the device performance. Using Transfer-Matrix-Algorithm (TMA) simulations, the best positions for the metal electrodes are determined. First, the electroluminescence (EL) of the adjusted OLED structure on top of a DBR is measured under nitrogen atmosphere. The modes showed quality factors of Q = 60. After the deposition of the top DBR, the EL is measured again and the quality factors increased up to Q = 600. Considering the two 25-nm-thick-silver contacts a Q-factor of 600 is very high. The realization of a suitable encapsulation method is important. Two approaches were successfully tested. The first method is based on the substitution of a DBR layer with a layer produced via Atomic Layer Deposition (ALD). The second method uses a 0.15-mm-thick cover glass glued on top of the DBR with a 0.23-μm-thick single-component glue layer. Due to the working encapsulation, it is possible to investigate the sample under ambient conditions.

Numerical investigation of optimized CZTSSe based solar cell in Wx-Amps environment

NASA Astrophysics Data System (ADS)

Mohanty, Soumya Priyadarshini; Padhy, Srinibasa; Chowdhury, Joy; Sing, Udai P.

2018-05-01

The CZTSSe is the modified version of CZTS with selenium infusion. It shows maximum efficiency in the band gap from 1 to 1.4 eV. In our present work CZTSSe based solar cell is investigated using Wx-Amps tool. The Mo layer, absorber layer, CdS layer, i-ZnO [4]and Al-ZnO layers with their electrical, optical and material parameters are fitted in the tool. The vital parameters such as carrier density, thickness of the CZTSSe absorber layer, operating temperature, CdS buffer layer thickness and its carrier density on the cell interpretation are calculated. From[4] the simulation results it is apparent that the optimal absorber layer varies from 2.9 µm to 3.7 µm. The temperature variation has a strong influence on the efficiency of the cell. An optimal efficiency of 22% (With Jsc=33 mA/cm2, Voc=0.98 V, and fill factor= 68%) are attained. These results will give some insight for makeing higher efficiency CZTSSe based solar cell.

Simple scattering analysis and simulation of optical components created by additive manufacturing

NASA Astrophysics Data System (ADS)

Rank, M.; Horsak, A.; Heinrich, A.

2017-10-01

Additive manufacturing of optical elements is known but still new to the field of optical fabrication. In 3D printers, the parts are deposited layer-by-layer approximating the shape defined in optics design enabling new shapes, which cannot be manufactured using conventional methods. However, the layered structure also causes surface roughness and subsurface scattering, which decrease the quality of optical elements. Illuminating a flat sample with a laser beam, different light distributions are generated on a screen depending on the printing orientation of the sample. Whereas the laser beam is mainly diffused by the samples, a line shaped light distribution can be achieved for a special case in which the laser light goes parallel to the layer structure. These optical effects of 3D printed parts are analyzed using a goniometric setup and fed back into the optics simulation with the goal to improve the design considering the characteristics of the real sample. For a detailed look on the effect, the total scattering is split up into surface contributions and subsurface scattering using index matching techniques to isolate the effects from each other. For an index matched sample with negligible surface effects the line shaped distribution turns into a diffraction pattern which corresponds to the layer thickness of the printer. Finally, an optic simulation with the scattering data is set up for a simple curved sample. The light distribution measured with a robot-based goniophotometer differs from the simulation, because the curvature is approximated by the layer structure. This makes additional analysis necessary.

Retinal Ganglion Cell Layer Thickness and Local Visual Field Sensitivity in Glaucoma

PubMed Central

Raza, Ali S.; Cho, Jungsuk; de Moraes, Carlos G. V.; Wang, Min; Zhang, Xian; Kardon, Randy H.; Liebmann, Jeffrey M.; Ritch, Robert; Hood, Donald C.

2015-01-01

Objective To compare loss in sensitivity measured using standard automated perimetry (SAP) with local retinal ganglion cell layer (RGC) thickness measured using frequency-domain optical coherence tomography in the macula of patients with glaucoma. Methods To compare corresponding locations of RGC thickness with total deviation (TD) of 10-2 SAP for 14 patients with glaucoma and 19 controls, an experienced operator hand-corrected automatic segmentation of the combined RGC and inner plexiform layer (RGC + IPL) of 128 horizontal B-scans. To account for displacement of the RGC bodies around the fovea, the location of the SAP test points was adjusted to correspond to the location of the RGC bodies rather than to the photoreceptors, based on published histological findings. For analysis, RGC + IPL thickness vs SAP (TD) data were grouped into 5 eccentricities, from 3.4° to 9.7° radius on the retina with respect to the fovea. Results The RGC + IPL thickness correlated well with SAP loss within approximately 7.2° of the fovea (Spearman ρ = 0.71–0.74). Agreement was worse (0.53–0.65) beyond 7.2°, where the normal RGC layer is relatively thin. A linear model relating RGC + IPL thickness to linear SAP loss provided a reasonable fit for eccentricities within 7.2°. Conclusion In the central 7.2°, local RGC + IPL thickness correlated well with local sensitivity loss in glaucoma when the data were adjusted for RGC displacement. PMID:22159673

Glaucoma diagnostic ability of ganglion cell-inner plexiform layer thickness differs according to the location of visual field loss.

PubMed

Shin, Hye-Young; Park, Hae-Young Lopilly; Jung, Kyoung-In; Choi, Jin-A; Park, Chan Kee

2014-01-01

To determine whether the ganglion cell-inner plexiform layer (GCIPL) or circumpapillary retinal nerve fiber layer (cpRNFL) is better at distinguishing eyes with early glaucoma from normal eyes on the basis of the the initial location of the visual field (VF) damage. Retrospective, observational study. Eighty-four patients with early glaucoma and 43 normal subjects were enrolled. The patients with glaucoma were subdivided into 2 groups according to the location of VF damage: (1) an isolated parafoveal scotoma (PFS, N = 42) within 12 points of a central 10 degrees in 1 hemifield or (2) an isolated peripheral nasal step (PNS, N = 42) within the nasal periphery outside 10 degrees of fixation in 1 hemifield. All patients underwent macular and optic disc scanning using Cirrus high-definition optical coherence tomography (Carl Zeiss Meditec, Dublin, CA). The GCIPL and cpRNFL thicknesses were compared between groups. Areas under the receiver operating characteristic curves (AUCs) were calculated. Comparison of diagnostic ability using AUCs. The average and minimum GCIPL of the PFS group were significantly thinner than those of the PNS group, whereas there was no significant difference in the average retinal nerve fiber layer (RNFL) thickness between the 2 groups. The AUCs of the average (0.962) and minimum GCIPL (0.973) thicknesses did not differ from that of the average RNFL thickness (0.972) for discriminating glaucomatous changes between normal and all glaucoma eyes (P =0.566 and 0.974, respectively). In the PFS group, the AUCs of the average (0.988) and minimum GCIPL (0.999) thicknesses were greater than that of the average RNFL thickness (0.961, P =0.307 and 0.125, respectively). However, the AUCs of the average (0.936) and minimum GCIPL (0.947) thicknesses were lower than that of the average RNFL thickness (0.984) in the PNS group (P =0.032 and 0.069, respectively). The GCIPL parameters were more valuable than the cpRNFL parameters for detecting glaucoma in eyes with parafoveal VF loss, and the cpRNFL parameters were better than the GCIPL parameters for detecting glaucoma in eyes with peripheral VF loss. Clinicians should know that the diagnostic capability of macular GCIPL parameters depends largely on the location of the VF loss. Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

van der Waals torque and force between dielectrically anisotropic layered media.

PubMed

Lu, Bing-Sui; Podgornik, Rudolf

2016-07-28

We analyse van der Waals interactions between a pair of dielectrically anisotropic plane-layered media interacting across a dielectrically isotropic solvent medium. We develop a general formalism based on transfer matrices to investigate the van der Waals torque and force in the limit of weak birefringence and dielectric matching between the ordinary axes of the anisotropic layers and the solvent. We apply this formalism to study the following systems: (i) a pair of single anisotropic layers, (ii) a single anisotropic layer interacting with a multilayered slab consisting of alternating anisotropic and isotropic layers, and (iii) a pair of multilayered slabs each consisting of alternating anisotropic and isotropic layers, looking at the cases where the optic axes lie parallel and/or perpendicular to the plane of the layers. For the first case, the optic axes of the oppositely facing anisotropic layers of the two interacting slabs generally possess an angular mismatch, and within each multilayered slab the optic axes may either be the same or undergo constant angular increments across the anisotropic layers. In particular, we examine how the behaviors of the van der Waals torque and force can be "tuned" by adjusting the layer thicknesses, the relative angular increment within each slab, and the angular mismatch between the slabs.

Differences in Optic Nerve Head, Retinal Nerve Fiber Layer, and Ganglion Cell Complex Parameters Between Caucasian and Chinese Subjects.

PubMed

Chansangpetch, Sunee; Huang, Guofu; Coh, Paul; Oldenburg, Catherine; Amoozgar, Behzad; He, Mingguang; Lin, Shan C

2018-04-01

To compare optic nerve head, peripapillary retinal nerve fiber layer (pRNFL), and ganglion cell complex (GCC) parameters between Caucasian and ethnic Chinese. Normal subjects above 40 years old and self-identified as being Caucasian and Chinese were recruited. They were evaluated with spectral-domain optical coherence tomography (RTVue-100). Parameters related to the optic nerve head, pRNFL, and GCC analysis protocols were acquired. Multivariable linear regression was performed adjusting for potential confounders. Data from 116 Caucasian and 130 Chinese subjects were available for analysis. Mean age of all participants was 66.72 (SD 10.82) years. There were statistically significant differences for disc area (DA), area cup-to-disc, vertical cup-to-disc, and cup volume (P=0.02, 0.004, 0.02, and 0.03, respectively), greater in Chinese. After adjusting for age, sex, axial length (AL), intraocular pressure (IOP), DA, and GCC thickness, Chinese subjects had significantly greater thickness in all pRNFL parameters (mean differences ranged between 4.29 and 9.93 μm; all P<0.001) except the nasal quadrant. GCC outcomes were also adjusted for DA and pRNFL; Caucasians had significantly higher average GCC and inferior GCC (mean difference 2.97 and 3.45 μm, respectively; P<0.01), whereas the Chinese group had significantly higher ganglion cell global loss volume (mean difference 2.47 %, P<0.001). This study suggests there is significantly greater pRNFL thickness in Chinese, which were independent of age, AL, IOP, and DA, and possibly greater GCC in Caucasians after adjustment for age, AL, IOP, DA, and pRNFL thickness.

Diagnostic Ability of Wide-field Retinal Nerve Fiber Layer Maps Using Swept-Source Optical Coherence Tomography for Detection of Preperimetric and Early Perimetric Glaucoma.

PubMed

Lee, Won June; Na, Kyeong Ik; Kim, Young Kook; Jeoung, Jin Wook; Park, Ki Ho

2017-06-01

To evaluate the diagnostic ability of wide-field retinal nerve fiber layer (RNFL) maps with swept-source optical coherence tomography (SS-OCT) for detection of preperimetric (PPG) and early perimetric glaucoma (EG). One hundred eighty-four eyes, including 67 healthy eyes, 43 eyes with PPG, and 74 eyes with EG, were analyzed. Patients underwent a comprehensive ocular examination including red-free RNFL photography, visual field testing and wide-field SS-OCT scanning (DRI-OCT-1 Atlantis; Topcon, Tokyo, Japan). SS-OCT provides a wide-field RNFL thickness map and a SuperPixel map, which are composed of the RNFL deviation map of the peripapillary area and the deviation map of the composition of the ganglion cell layer with the inner plexiform layer and RNFL (GC-IPL+RNFL) in the macular area. The ability to discriminate PPG and EG from healthy eyes was assessed using sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) for all parameters and criteria provided by the wide-field SS-OCT scan. The wide-field RNFL thickness map using SS-OCT showed the highest sensitivity of PPG-diagnostic and EG-diagnostic performance compared with the other SS-OCT criteria based on the internal normative base (93.0 and 97.3%, respectively). Among the SS-OCT continuous parameters, the RFNL thickness of the 7 clock-hour, inferior and inferotemporal macular ganglion cell analyses showed the largest AUC of PPG-diagnostic and EG-diagnostic performance (AUC=0.809 to 0.865). The wide-field RNFL thickness map using SS-OCT performed well in distinguishing eyes with PPG and EG from healthy eyes. In the clinical setting, wide-field RNFL maps of SS-OCT can be useful tools for detection of early-stage glaucoma.

Fast optical detecting media based on semiconductor nanostructures for recording images obtained using charges of free photocarriers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasherininov, P. G., E-mail: peter.kasherininov@mail.ioffe.ru; Tomasov, A. A.; Beregulin, E. V.

2011-01-15

Available published data on the properties of optical recording media based on semiconductor structures are reviewed. The principles of operation, structure, parameters, and the range of application for optical recording media based on MIS structures formed of photorefractive crystals with a thick layer of insulator and MIS structures with a liquid crystal as the insulator (the MIS LC modulators), as well as the effect of optical bistability in semiconductor structures (semiconductor MIS structures with nanodimensionally thin insulator (TI) layer, M(TI)S nanostructures). Special attention is paid to recording media based on the M(TI)S nanostructures promising for fast processing of highly informativemore » images and to fabrication of optoelectronic correlators of images for noncoherent light.« less

Novel Layered Supercell Structure from Bi 2AlMnO 6 for Multifunctionalities

DOE PAGES

Li, Leigang; Boullay, Philippe; Lu, Ping; ...

2017-10-02

Layered materials, e.g., graphene and transition metal (di)chalcogenides, holding great promises in nanoscale device applications have been extensively studied in fundamental chemistry, solid state physics and materials research areas. In parallel, layered oxides (e.g., Aurivillius and Ruddlesden–Popper phases) present an attractive class of materials both because of their rich physics behind and potential device applications. In this work, we report a novel layered oxide material with self-assembled layered supercell structure consisting of two mismatch-layered sublattices of [Bi 3O 3+δ] and [MO 2] 1.84 (M = Al/Mn, simply named BAMO), i.e., alternative layered stacking of two mutually incommensurate sublattices made ofmore » a three-layer-thick Bi–O slab and a one-layer-thick Al/Mn–O octahedra slab in the out-of-plane direction. Strong room-temperature ferromagnetic and piezoelectric responses as well as anisotropic optical property have been demonstrated with great potentials in various device applications. Furthermore, the realization of the novel BAMO layered supercell structure in this work has paved an avenue toward exploring and designing new materials with multifunctionalities.« less

Simulation of the lunar surface emission and inversion of the lunar regolith thickness using fusion of optical and microwave remote sensing data

NASA Astrophysics Data System (ADS)

Jin, Y.-Q.

begin table htbp begin center begin tabular p 442pt hline A correspondence of the lunar regolith layer thickness to the lunar digital elevation mapping DEM is presented to construct the global distribution of lunar regolith layer thickness Based on some measurements the physical temperature distribution over the lunar surface is proposed Albedo of the lunar nearside at the wavelengths 0 42 0 65 0 75 0 95 mu m from the telescopic observation is employed to construct the spatial distribution of the FeO TiO 2 on the lunar regolith layer A statistic relationship between the DEM and FeO TiO 2 content of the lunar nearside is then extended to construction of FeO TiO 2 content of the lunar farside Thus the dielectric permittivity of global lunar regolith layer can be determined par Based on all theses conditions brightness temperature of the lunar regolith layer in passive microwave remote sensing which is planned for China s Chang-E lunar project is numerically simulated by a parallel layer model using the fluctuation dissipation theorem par Furthermore taking these simulations as observations an inversion method of the lunar regolith layer thickness is developed by using three- or two-channels brightness temperatures When the FeO TiO 2 content is low and the four channels brightness temperatures in Chang-E project are well distinguishable the regolith layer thickness and physical temperature of the underlying lunar rocky media can be inverted by the three-channels approach When the FeO TiO 2 content is so high that the

Effects of annealing temperature and duration on the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire.

PubMed

Sui, Mao; Li, Ming-Yu; Kunwar, Sundar; Pandey, Puran; Zhang, Quanzhen; Lee, Jihoon

2017-01-01

Metallic nanostructures (NSs) have been widely adapted in various applications and their physical, chemical, optical and catalytic properties are strongly dependent on their surface morphologies. In this work, the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire (0001) is demonstrated by the control of annealing temperature and dwelling duration with the distinct thickness of Pt films. The formation of Pt NSs is led by the surface diffusion, agglomeration and surface and interface energy minimization of Pt thin films, which relies on the growth parameters such as system temperature, film thickness and annealing duration. The Pt layer of 10 nm shows the formation of overlaying NPs below 650°C and isolated Pt nanoparticles above 700°C based on the enhanced surface diffusion and Volmer-Weber growth model whereas larger wiggly nanostructures are formed with 20 nm thick Pt layers based on the coalescence growth model. The morphologies of Pt nanostructures demonstrate a sharp distinction depending on the growth parameters applied. By the control of dwelling duration, the gradual transition from dense Pt nanoparticles to networks-like and large clusters is observed as correlated to the Rayleigh instability and Ostwald ripening. The various Pt NSs show a significant distinction in the reflectance spectra depending on the morphology evolution: i.e. the enhancement in UV-visible and NIR regions and the related optical properties are discussed in conjunction with the Pt NSs morphology and the surface coverage.

Contamination of grazing incidence EUV mirrors - An assessment

NASA Technical Reports Server (NTRS)

Osantowski, John F.; Fleetwood, C. F.

1988-01-01

Contamination assessment for space optical systems requires an understanding of the sensitivity of component performance, e.g. mirror reflectance, to materials deposited on the mirror surface. In a previous study, the sensitivity of typical normal incidence mirror coatings to surface deposits of generic hydrocarbons was reported. Recent activity in the development of grazing incidence telescopes for extreme ultraviolet space astronomy has stimulated the need for a similar assessment in the spectral region extending from approximately 100 A to 1000 A. The model used for analysis treats the contamination layer as a continuous thin film deposited on the mirror surface. The mirror surfaces selected for this study are opaque vacuum deposited gold and the uncoated and polished Zerodur. Scatter caused by film irregularities or particulates are not included in this assessment. Parametric evaluations at 100, 500, and 1000 A determine the sensitivity of mirror reflectance to a range of optical constants selected for the generic contaminants. This sensitivity analysis combined with the limited amount of optical data in the EUV for hydrocarbons, is used to select representative optical constants for the three wavelength regions. Reflectance versus contamination layer thickness curves are then calculated and used to determine critical thickness limits based on allowable reflectance change. Initial observations indicate that thickness limits will be highly dependent on the real part of the complex index of refraction of the contaminant film being less than 1.0. Preliminary laboratory measurements of samples contaminated with some commonly encountered hydrocarbons confirm trends indicated in the analytical studies.

Growth of ZnMgTe/ZnTe waveguide structures on ZnTe (0 0 1) substrates by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Kumagai, Y.; Imada, S.; Baba, T.; Kobayashi, M.

2011-05-01

ZnMgTe/ZnTe/ZnMgTe layered structures were grown on (0 0 1) ZnTe substrates by molecular beam epitaxy. This structure was designed to apply to waveguides in various optoelectronic devices to reduce light loss. Since the lattice mismatch between ZnTe and ZnMgTe was not negligible, the critical layer thickness (CLT) was theoretically derived. Structures with varying Mg composition and layer thickness of ZnMgTe cladding layer were grown and examined for crystal quality with respect to theoretical data. The crystal quality was investigated by means of cross sectional transmission electron microscopy (TEM) and reciprocal space mapping (RSM). Optical confinements were observed by irradiating a laser beam from one end of the sample and monitoring the transmitted light from the other end.

Simultaneous measurement of lipid and aqueous layers of tear film using optical coherence tomography and statistical decision theory

NASA Astrophysics Data System (ADS)

Huang, Jinxin; Clarkson, Eric; Kupinski, Matthew; Rolland, Jannick P.

2014-03-01

The prevalence of Dry Eye Disease (DED) in the USA is approximately 40 million in aging adults with about $3.8 billion economic burden. However, a comprehensive understanding of tear film dynamics, which is the prerequisite to advance the management of DED, is yet to be realized. To extend our understanding of tear film dynamics, we investigate the simultaneous estimation of the lipid and aqueous layers thicknesses with the combination of optical coherence tomography (OCT) and statistical decision theory. In specific, we develop a mathematical model for Fourier-domain OCT where we take into account the different statistical processes associated with the imaging chain. We formulate the first-order and second-order statistical quantities of the output of the OCT system, which can generate some simulated OCT spectra. A tear film model, which includes a lipid and aqueous layer on top of a rough corneal surface, is the object being imaged. Then we further implement a Maximum-likelihood (ML) estimator to interpret the simulated OCT data to estimate the thicknesses of both layers of the tear film. Results show that an axial resolution of 1 μm allows estimates down to nanometers scale. We use the root mean square error of the estimates as a metric to evaluate the system parameters, such as the tradeoff between the imaging speed and the precision of estimation. This framework further provides the theoretical basics to optimize the imaging setup for a specific thickness estimation task.

Surface plasmon-assisted microscope.

PubMed

Borejdo, Julian; Gryczynski, Zygmunt; Fudala, Rafal; Joshi, Chaitanya R; Borgmann, Kathleen; Ghorpade, Anuja; Gryczynski, Ignacy

2018-06-01

Total internal reflection microscopy (TIRF) has been a powerful tool in biological research. The most valuable feature of the method has been the ability to image 100- to 200-nm-thick layer of cell features adjacent to a coverslip, such as membrane lipids, membrane receptors, and structures proximal-to-basal membranes. Here, we demonstrate an alternative method of imaging thin-layer proximal-to-basal membranes by placing a sample on a high refractive index coverslip covered by a thin layer of gold. The sample is illuminated using the Kretschmann method (i.e., from the top to an aqueous medium). Fluorophores that are close to the metal surface induce surface plasmons in the metal film. Fluorescence from fluorophores near the metal surface couple with surface plasmons allowing them to penetrate the metal surface and emerge at a surface plasmon coupled emission angle. The thickness of the detection layer is further reduced in comparison with TIRF by metal quenching of fluorophores at a close proximity (below 10 nm) to a surface. Fluorescence is collected by a high NA objective and imaged by EMCCD or converted to a signal by avalanche photodiode fed by a single-mode optical fiber inserted in the conjugate image plane of the objective. The system avoids complications of through-the-objective TIRF associated with shared excitation and emission light path, has thin collection thickness, produces excellent background rejection, and is an effective method to study molecular motion. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Traveling wave electro-optic phase modulators based on intrinsically polar self-assembled chromophoric superlattices

NASA Astrophysics Data System (ADS)

Zhao, Y.-G.; Wu, A.; Lu, H.-L.; Chang, S.; Lu, W.-K.; Ho, S. T.; van der Boom, M. E.; Marks, T. J.

2001-07-01

Traveling-wave electro-optic modulators based on chromophoric self-assembled superlattices (SASs) possessing intrinsically polar microstructures have been designed and fabricated. Although the thickness of the SAS layer is only ˜150 nm, a π-phase shift is clearly observed. From the measured Vπ value, the effective electro-optic coefficient of the SAS film is determined to be ˜21.8 pm/V at an input wavelength of 1064 nm.

Retinal nerve fiber layer thickness analysis in suspected malingerers with optic disc temporal pallor

PubMed Central

Civelekler, Mustafa; Halili, Ismail; Gundogan, Faith C; Sobaci, Gungor

2009-01-01

Purpose: To investigate the value of temporal retinal nerve fiber layer (RNFLtemporal) thickness in the prediction of malingering. Materials and Methods: This prospective, cross-sectional study was conducted on 33 military conscripts with optic disc temporal pallor (ODTP) and 33 age-and sex-matched healthy controls. Initial visual acuity (VAi) and visual acuity after simulation examination techniques (VAaset) were assessed. The subjects whose VAaset were two or more lines higher than VAi were determined as malingerers. Thickness of the peripapillary RNFL was determined with OCT (Stratus OCT™, Carl Zeiss Meditec, Inc.). RNFLtemporal thickness of the subjects were categorized into one of the 1+ to 4+ groups according to 50% confidence interval (CI), 25% CI and 5% CI values which were assessed in the control group. The VAs were converted to LogMAR-VAs for statistical comparisons. Results: A significant difference was found only in the temporal quadrant of RNFL thickness in subjects with ODTP (P=0.002). Mean LogMAR-VA increased significantly after SETs (P<0.001). Sensitivity, specificity, positive and negative predictive values of categorized RNFLtemporal thickness in diagnosing malingering were 84.6%, 75.0%, 68.8%, 88.2%, respectively. ROC curve showed that RNFLtemporal thickness of 67.5 μm is a significant cut-off point in determining malingering (P=0.001, area under the curve:0.862). The correlations between LogMAR-VAs and RNFLtemporal thicknesses were significant; the correlation coefficient for LogMAR-VAi was lower than the correlation for LogMAR-VAaset (r=−0.447, P=0.009 for LogMAR-VAi; r=−0.676, P<0.001 for LogMAR-VAaset). Conclusions: RNFLtemporal thickness assessment may be a valuable tool in determining malingering in subjects with ODTP objectively. PMID:19700875

Assessment of Optical Coherence Tomography Color Probability Codes in Myopic Glaucoma Eyes After Applying a Myopic Normative Database.

PubMed

Seol, Bo Ram; Kim, Dong Myung; Park, Ki Ho; Jeoung, Jin Wook

2017-11-01

To evaluate the optical coherence tomography (OCT) color probability codes based on a myopic normative database and to investigate whether the implementation of the myopic normative database can improve the OCT diagnostic ability in myopic glaucoma. Comparative validity study. In this study, 305 eyes (154 myopic healthy eyes and 151 myopic glaucoma eyes) were included. A myopic normative database was obtained based on myopic healthy eyes. We evaluated the agreement between OCT color probability codes after applying the built-in and myopic normative databases, respectively. Another 120 eyes (60 myopic healthy eyes and 60 myopic glaucoma eyes) were included and the diagnostic performance of OCT color codes using a myopic normative database was investigated. The mean weighted kappa (Kw) coefficients for quadrant retinal nerve fiber layer (RNFL) thickness, clock-hour RNFL thickness, and ganglion cell-inner plexiform layer (GCIPL) thickness were 0.636, 0.627, and 0.564, respectively. The myopic normative database showed a higher specificity than did the built-in normative database in quadrant RNFL thickness, clock-hour RNFL thickness, and GCIPL thickness (P < .001, P < .001, and P < .001, respectively). The receiver operating characteristic curve values increased when using the myopic normative database in quadrant RNFL thickness, clock-hour RNFL thickness, and GCIPL thickness (P = .011, P = .004, P < .001, respectively). The diagnostic ability of OCT color codes for detection of myopic glaucoma significantly improved after application of the myopic normative database. The implementation of a myopic normative database is needed to allow more precise interpretation of OCT color probability codes when used in myopic eyes. Copyright © 2017 Elsevier Inc. All rights reserved.

Optical monitoring of rugate filters

NASA Astrophysics Data System (ADS)

Lappschies, Marc; Görtz, Björn; Ristau, Detlev

2005-09-01

Rugate filters have a high potential for solving specific design problems in many applications of modern optics and lighting technology. However, the exact manufacture of these gradual layer systems is still a challenge which could not be solved completely until today. One of the prominent approaches for the production of rugate filters is based on independent quartz crystal devices measuring the rate of the different coating materials. As an alternative, optical broadband monitoring has been already qualified for controlling the deposition of complicated non quarterwave stacks. In the present study, promising results of this deposition control concept as a direct monitoring of rugate filters will be presented. In a first attempt, the continuous change of refractive indices in the graded layers was transformed to a set of discrete homogeneous sub-layers with thicknesses values of around 5 nm. These discrete layers are realized by defined mixtures of two materials. A data base for the dispersion behavior was created for the different mixing ratios and is employed for the production of such quasi-rugate filters. The optical monitor is operated in the routine mode determining the switching points of the layers. Selected examples will be presented for quasi rugate coatings produced by ion beam sputtering from a movable zone target. Different designs will be discussed considering production problems as well as achievable optical properties.

Direct Push Optical Screening Tool for High-Resolution, Real-Time Mapping of Chlorinated Solvent DNAPL Architecture

DTIC Science & Technology

2016-04-01

due to higher densities, lower viscosities , and increased weathering (mass depletion) of residual chlorinated solvent DNAPL compared to those other...demonstration area can be generally classified as stratified layers of fine sand and silt with few clay layers. A silt layer was penetrated consistently at...toxic and carcinogenic. Another potential issue evaluated was that in plastic soils (stiff clays for example) there is potential for the thickness of

Direct Push Optical Screening Tool for High Resolution, Real-Time Mapping of Chlorinated Solvent DNAPL Architecture

DTIC Science & Technology

2016-07-01

petroleum hydrocarbon fuels due to higher densities, lower viscosities , and increased weathering (mass depletion) of residual chlorinated solvent DNAPL...generally classified as stratified layers of fine sand and silt with few clay layers. A silt layer was penetrated consistently at a depth of about 45...e.g., stiff clays ) there is potential for the thickness of the dye interaction zone to increase to approximately 1-2 mm. Intuition suggests that this

Ellipsometric porosimetry on pore-controlled TiO2 layers

NASA Astrophysics Data System (ADS)

Rosu, Dana-Maria; Ortel, Erik; Hodoroaba, Vasile-Dan; Kraehnert, Ralph; Hertwig, Andreas

2017-11-01

The practical performance of surface coatings in applications like catalysis, water splitting or batteries depends critically on the coating materials' porosity. Determining the porosity in a fast and non-destructive way is still an unsolved problem for industrial thin-films technology. As a contribution to calibrated, non-destructive, optical layer characterisation, we present a multi-method comparison study on porous TiO2 films deposited by sol-gel synthesis on Si wafers. The ellipsometric data were collected on a range of samples with different TiO2 layer thickness and different porosity values. These samples were produced by templated sol-gel synthesis resulting in layers with a well-defined pore size and pore density. The ellipsometry measurement data were analysed by means of a Bruggeman effective medium approximation (BEMA), with the aim to determine the mixture ratio of void and matrix material by a multi-sample analysis strategy. This analysis yielded porosities and layer thicknesses for all samples as well as the dielectric function for the matrix material. Following the idea of multi-method techniques in metrology, the data was referenced to imaging by electron microscopy (SEM) and to a new EPMA (electron probe microanalysis) porosity approach for thin film analysis. This work might lead to a better metrological understanding of optical porosimetry and also to better-qualified characterisation methods for nano-porous layer systems.

Corneal thickness: measurement and implications.

PubMed

Ehlers, Niels; Hjortdal, Jesper

2004-03-01

The thickness of the cornea was reported in more than 100-year-old textbooks on physiological optics (Helmholtz, Gullstrand). Physiological interest was revived in the 1950s by David Maurice, and over the next 50 years, this 'simple' biological parameter has been studied extensively. Several techniques for its measurement have been described and physiological and clinical significance have been studied. In this review, the different methods and techniques of measurement are briefly presented (optical, ultrasound). While the corneal thickness of many animals are the same over a considerable part of the surface, in the human cornea anterior and posterior curvature are not concentric giving rise to a problem of definition. Based on this the precision and accuracy of determining the central corneal thickness are discussed. Changes in corneal thickness reflects changes in function of the boundary layers, in particular the endothelial barrier. The absolute value of thickness is of importance for the estimation of IOP but also in diagnosis of corneal and systemic disorders. Finally it is discussed to what extent the thickness is a biometric parameter of significance, e.g. in the progression of myopia or in the development of retinal detachment.

Effect of substrates and thickness on optical properties in atomic layer deposition grown ZnO thin films

NASA Astrophysics Data System (ADS)

Pal, Dipayan; Singhal, Jaya; Mathur, Aakash; Singh, Ajaib; Dutta, Surjendu; Zollner, Stefan; Chattopadhyay, Sudeshna

2017-11-01

Atomic Layer Deposition technique was used to grow high quality, very low roughness, crystalline, Zinc Oxide (ZnO) thin films on silicon (Si) and fused quartz (SiO2) substrates to study the optical properties. Spectroscopic ellipsometry results of ZnO/Si system, staggered type-II quantum well, demonstrate that there is a significant drop in the magnitudes of both the real and imaginary parts of complex dielectric constants and in near-band gap absorption along with a blue shift of the absorption edge with decreasing film thickness at and below ∼20 nm. Conversely, UV-vis absorption spectroscopy of ZnO/SiO2, thin type-I quantum well, consisting of a narrower-band gap semiconductor grown on a wider-band gap (insulator) substrate, shows the similar thickness dependent blue-shift of the absorption edge but with an increase in the magnitude of near-band gap absorption with decreasing film thickness. Thickness dependent blue shift, energy vs. 1/d2, in two different systems, ZnO/Si and ZnO/SiO2, show a difference in their slopes. The observed phenomena can be consistently explained by the corresponding exciton (or carrier/s) deconfinement and confinement effects at the ZnO/Si and ZnO/SiO2 interface respectively, where Tanguy-Elliott amplitude pre-factor plays the key role through the electron-hole overlap factor at the interface.

Fabrication of dense wavelength division multiplexing filters with large useful area

NASA Astrophysics Data System (ADS)

Lee, Cheng-Chung; Chen, Sheng-Hui; Hsu, Jin-Cherng; Kuo, Chien-Cheng

2006-08-01

Dense Wavelength Division Multiplexers (DWDM), a kind of narrow band-pass filter, are extremely sensitive to the optical thickness error in each composite layer. Therefore to have a large useful coating area is extreme difficult because of the uniformity problem. To enlarge the useful coating area it is necessary to improve their design and their fabrication. In this study, we discuss how the tooling factors at different positions and for different materials are related to the optical performance of the design. 100GHz DWDM filters were fabricated by E-gun evaporation with ion-assisted deposition (IAD). To improve the coating uniformity, an analysis technique called shaping tooling factor (STF) was used to analyze the deviation of the optical thickness in different materials so as to enlarge the useful coating area. Also a technique of etching the deposited layers with oxygen ions was introduced. When the above techniques were applied in the fabrication of 100 GHz DWDM filters, the uniformity was better than +/-0.002% over an area of 72 mm in diameter and better than +/-0.0006% over 20mm in diameter.

Experimental investigation on the caries characteristic of dental tissues by photothermal radiometry scanning imaging

NASA Astrophysics Data System (ADS)

Wang, Fei; Liu, Jun-yan; Wang, Xiao-chun; Wang, Yang

2018-03-01

In this paper, a one-dimensional (1D) thermal-wave model coupled diffuse-photon-density-wave for three-layer dental tissues using modulated laser stimulation was employed to illustrate the relationship between dental caries characteristic (i.e. caries layer thickness, optical absorption coefficient and optical scattering coefficient) and photothermal radiometry (PTR) signal. Experimental investigation of artificial caries was carried out using PTR scanning imaging. The PTR amplitude and phase delay were increased with dental demineralized treatment. The local caries characteristic parameters were obtained by the best-fitting method based on the 1D thermal-wave model. The PTR scanning imaging measurements illustrated that the optical absorption coefficient and scattering coefficient of caries region were much higher than those of the healthy enamel area. The demineralization thickness of caries region was measured by PTR scanning imaging and its average value shows in good agreement with the digital microscope. Experimental results show that PTR scanning imaging has the merits of high contrast for local inhomogeneity of dental caries; furthermore, this method is an allowance to provide a flexibility for non-contact quantitative evaluation of dental caries.

Multimodal Imaging in Diabetic Macular Edema.

PubMed

Acón, Dhariana; Wu, Lihteh

2018-01-01

Throughout ophthalmic history it has been shown that progress has gone hand in hand with technological breakthroughs. In the past, fluorescein angiography and fundus photographs were the most commonly used imaging modalities in the management of diabetic macular edema (DME). Today, despite the moderate correlation between macular thickness and functional outcomes, spectral domain optical coherence tomography (SD-OCT) has become the DME workhorse in clinical practice. Several SD-OCT biomarkers have been looked at including presence of epiretinal membrane, vitreomacular adhesion, disorganization of the inner retinal layers, central macular thickness, integrity of the ellipsoid layer, and subretinal fluid, among others. Emerging imaging modalities include fundus autofluorescence, macular pigment optical density, fluorescence lifetime imaging ophthalmoscopy, OCT angiography, and adaptive optics. Technological advances in imaging of the posterior segment of the eye have enabled ophthalmologists to develop hypotheses about pathological mechanisms of disease, monitor disease progression, and assess response to treatment. Spectral domain OCT is the most commonly performed imaging modality in the management of DME. However, reliable biomarkers have yet to be identified. Machine learning may provide treatment algorithms based on multimodal imaging. Copyright 2018 Asia-Pacific Academy of Ophthalmology.

Topical meeting on optical interference coatings (OIC'2001): manufacturing problem.

PubMed

Dobrowolski, J A; Browning, Stephen; Jacobson, Michael; Nadal, Maria

2002-06-01

Measurements are presented of the experimental filters submitted to the first optical thin-film manufacturing problem posed in conjunction with the Topical Meeting on Optical Interference Coatings, in which the object was to produce multilayers with spectral transmittance and reflectance curves that were as close as possible to the target values that were specified in the 400- to 600-nm spectral region. No limit was set on the overall thickness of the solutions or the number of layers used in their construction. The participants were free to use the coating materials of their choice. Six different groups submitted a total of 11 different filters for evaluation. Three different physical vapor deposition processes were used for the manufacture of the coatings: magnetron sputtering, ion-beam sputtering, and plasma-ion-assisted, electron-beam gun evaporation. The solutions ranged in metric thickness from 758 to 4226 nm and consisted of between 8 and 27 layers. For all but two of the samples submitted, the average rms departure of the measured transmittances and reflectances from the target values in the spectral region of interest was between 0.98% and 1.55%.

Multiple scattered radiation emerging from Rayleigh and continental haze layers. I - Radiance, polarization, and neutral points

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Plass, G. N.; Hitzfelder, S. J.

1976-01-01

The matrix operator method was used to calculate the polarization of radiation scattered on layers of various optical thicknesses, with results compared for Rayleigh scattering and for scattering from a continental haze. In both cases, there are neutral points arising from the zeros of the polarization of single scattered photons at scattering angles of zero and 180 degrees. The angular position of these Rayleigh-like neutral points (RNP) in the sky shows appreciable variation with the optical thickness of the scattering layer for a Rayleigh phase matrix, but only a small variation for haze L phase matrix. Another type of neutral point exists for non-Rayleigh phase functions that is associated with the zeros of the polarization for single scattering which occurs between the end points of the curve. A comparison of radiances calculated from the complete theory of radiative transfer using Stokes vectors with those obtained from the scalar theory shows that differences of the order of 23% may be obtained for Rayleigh scattering, while the largest difference found for a haze L phase function was of the order of 0.1%.

Characterization of PET preforms using spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Hosseiny, Hamid; Ferreira, Manuel João.; Martins, Teresa; Carmelo Rosa, Carla

2013-11-01

Polyethylene terephthalate (PET) preforms are massively produced nowadays with the purpose of producing food and beverages packaging and liquid containers. Some varieties of these preforms are produced as multilayer structures, where very thin inner film(s) act as a barrier for nutrients leakage. The knowledge of the thickness of this thin inner layer is important in the production line. The quality control of preforms production requires a fast approach and normally the thickness control is performed by destructive means out of the production line. A spectral domain optical coherence tomography (SD-OCT) method was proposed to examine the thin layers in real time. This paper describes a nondestructive approach and all required signal processing steps to characterize the thin inner layers and also to improve the imaging speed and the signal to noise ratio. The algorithm was developed by using graphics processing unit (GPU) with computer unified device architecture (CUDA). This GPU-accelerated white light interferometry technique nondestructively assesses the samples and has high imaging speed advantage, overcoming the bottlenecks in PET performs quality control.

Optical coherence tomography for nondestructive evaluation of fuel rod degradation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renshaw, Jeremy B., E-mail: jrenshaw@epri.com; Jenkins, Thomas P., E-mail: tjenkins@metrolaserinc.com; Buckner, Benjamin D., E-mail: tjenkins@metrolaserinc.com

Nuclear power plants regularly inspect fuel rods to ensure safe and reliable operation. Excessive corrosion can cause fuel failures which can have significant repercussions for the plant, including impacts on plant operation, worker exposure to radiation, and the plant's INPO rating. While plants typically inspect for fuel rod corrosion using eddy current techniques, these techniques have known issues with reliability in the presence of tenacious, ferromagnetic crud layers that can deposit during operation, and the nondestructive evaluation (NDE) inspection results can often be in error by a factor of 2 or 3. For this reason, alternative measurement techniques, such asmore » Optical Coherence Tomography (OCT), have been evaluated that are not sensitive to the ferromagnetic nature of the crud. This paper demonstrates that OCT has significant potential to characterize the thickness of crud layers that can deposit on the surfaces of fuel rods during operation. Physical trials have been performed on simulated crud samples, and the resulting data show an apparent correlation between the crud layer thickness and the OCT signal.« less

Iridescent colour production in hairs of blind golden moles (Chrysochloridae).

PubMed

Snyder, Holly K; Maia, Rafael; D'Alba, Liliana; Shultz, Allison J; Rowe, Karen M C; Rowe, Kevin C; Shawkey, Matthew D

2012-06-23

Relative to other metazoans, the mammalian integument is thought to be limited in colour. In particular, while iridescence is widespread among birds and arthropods, it has only rarely been reported in mammals. Here, we examine the colour, morphology and optical mechanisms in hairs from four species of golden mole (Mammalia: Chrysochloridae) that are characterized by sheens ranging from purple to green. Microspectrophotometry reveals that this colour is weak and variable. Iridescent hairs are flattened and have highly reduced cuticular scales, providing a broad and smooth surface for light reflection. These scales form multiple layers of light and dark materials of consistent thickness, strikingly similar to those in the elytra of iridescent beetles. Optical modelling suggests that the multi-layers produce colour through thin-film interference, and that the sensitivity of this mechanism to slight changes in layer thickness and number explains colour variability. While coloured integumentary structures are typically thought to evolve as sexual ornaments, the blindness of golden moles suggests that the colour may be an epiphenomenon resulting from evolution via other selective factors, including the ability to move and keep clean in dirt and sand.

Comparison of Foveal, Macular, and Peripapillary Intraretinal Thicknesses Between Autism Spectrum Disorder and Neurotypical Subjects.

PubMed

García-Medina, José Javier; García-Piñero, María; Del-Río-Vellosillo, Mónica; Fares-Valdivia, Jesarán; Ragel-Hernández, Ana Belén; Martínez-Saura, Salvador; Cárcel-López, María Dolores; Zanon-Moreno, Vicente; Pinazo-Duran, María Dolores; Villegas-Pérez, María Paz

2017-11-01

To compare thicknesses of intraretinal layers segmented by spectral-domain optical coherence tomography (SD-OCT) between autism spectrum disorder (ASD) and neurotypical (NT) individuals. We performed 2 scans on 108 eyes from 54 participants (27 high-functioning ASD and 27 age- and sex-matched NT subjects): macular fast volume and peripapillary retinal nerve fiber layer (pRNFL). Macula was automatically segmented. The mean foveal and macular thickness of nine different layers and the thickness of nine pRNFL sectors were considered. Data from the right and left eyes were averaged for each participant. The results were compared between the ASD and NT groups. Associations between the Kaufman brief intelligence test (K-BIT), head circumference and SD-OCT results were also investigated in ASD individuals. ASD subjects showed greater foveal thickness at total retina, total inner retina, inner plexiform and inner nuclear layers, and greater macular thickness at total retina and total inner retina. Inferior, nasal inferior and temporal inferior sectors of pRNFL were also thicker in the ASD participants than in the controls (P < 0.05, unpaired t-test). Significant correlations were found between some K-BIT results and temporal inferior and inferior pRNFL thicknesses in the ASD group (P < 0.05, Spearman's rank correlation). No associations were seen between head circumference and OCT parameters. There are intraretinal thickenings at different locations in ASD subjects when compared to NT controls. This fact should be taken into account when interpreting SD-OCT examinations in ASD individuals. Plus, some pRNFL thicknesses present positive correlations with scores of cognitive status in ASD.

Determination of thickness of thin turbid painted over-layers using micro-scale spatially offset Raman spectroscopy

NASA Astrophysics Data System (ADS)

Conti, Claudia; Realini, Marco; Colombo, Chiara; Botteon, Alessandra; Bertasa, Moira; Striova, Jana; Barucci, Marco; Matousek, Pavel

2016-12-01

We present a method for estimating the thickness of thin turbid layers using defocusing micro-spatially offset Raman spectroscopy (micro-SORS). The approach, applicable to highly turbid systems, enables one to predict depths in excess of those accessible with conventional Raman microscopy. The technique can be used, for example, to establish the paint layer thickness on cultural heritage objects, such as panel canvases, mural paintings, painted statues and decorated objects. Other applications include analysis in polymer, biological and biomedical disciplines, catalytic and forensics sciences where highly turbid overlayers are often present and where invasive probing may not be possible or is undesirable. The method comprises two stages: (i) a calibration step for training the method on a well characterized sample set with a known thickness, and (ii) a prediction step where the prediction of layer thickness is carried out non-invasively on samples of unknown thickness of the same chemical and physical make up as the calibration set. An illustrative example of a practical deployment of this method is the analysis of larger areas of paintings. In this case, first, a calibration would be performed on a fragment of painting of a known thickness (e.g. derived from cross-sectional analysis) and subsequently the analysis of thickness across larger areas of painting could then be carried out non-invasively. The performance of the method is compared with that of the more established optical coherence tomography (OCT) technique on identical sample set. This article is part of the themed issue "Raman spectroscopy in art and archaeology".

Diagnostic Accuracy of Optical Coherence Tomography and Scanning Laser Tomography for Identifying Glaucoma in Myopic Eyes.

PubMed

Malik, Rizwan; Belliveau, Anne C; Sharpe, Glen P; Shuba, Lesya M; Chauhan, Balwantray C; Nicolela, Marcelo T

2016-06-01

Ruling out glaucoma in myopic eyes often poses a diagnostic challenge because of atypical optic disc morphology and visual field defects that can mimic glaucoma. We determined whether neuroretinal rim assessment based on Bruch's membrane opening (BMO), rather than conventional optic disc margin (DM)-based assessment or retinal nerve fiber layer (RNFL) thickness, yielded higher diagnostic accuracy in myopic patients with glaucoma. Case-control, cross-sectional study. Myopic patients with glaucoma (n = 56) and myopic normal controls (n = 74). Myopic subjects with refraction error greater than -2 diopters (D) (spherical equivalent) and typical myopic optic disc morphology, with and without glaucoma, were recruited from a glaucoma clinic and a local optometry practice. The final classification of myopic glaucoma or myopic control was based on consensus assessment by 3 clinicians of visual fields and optic disc photographs. Participants underwent imaging with confocal scanning laser tomography for measurement of DM rim area (DM-RA) and with spectral domain optical coherence tomography (SD OCT) for quantification of a BMO-based neuroretinal rim parameter, minimum rim width (BMO-MRW), and RNFL thickness. Sensitivity of DM-RA, BMO-MRW, and RNFL thickness at a fixed specificity of 90% and partial area under the curves (pAUCs) for global and sectoral parameters for specificities ≥90%. Sensitivities at 90% specificity were 30% for DM-RA and 71% for both BMO-MRW and RNFL thickness. The pAUC was higher for the BMO-MRW compared with DM-RA (P < 0.001), but similar to RNFL thickness (P > 0.5). Sectoral values of BMO-MRW tended to have a higher, but nonsignificant, pAUC across all sectors compared with RNFL thickness. Bruch's membrane opening MRW is more sensitive than DM-RA and similar to RNFL thickness for the identification of glaucoma in myopic eyes and offers a valuable diagnostic tool for patients with glaucoma with myopic optic discs. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamidi, S. M.

2012-01-15

In this paper, the optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals have been investigated. We use transfer matrix method to solve our magnetized coupled resonator plasma photonic crystals consist of dielectric and magnetized plasma layers. The results of the change in the optical and magneto-optical properties of structure as a result of the alteration in the structural properties such as thickness, plasma frequency and collision frequency, plasma filling factor, number of resonators and dielectric constant of dielectric layers and external magnetic field have been reported. The main feature of this structure is a good magneto-opticalmore » rotation that takes place at the defect modes and the edge of photonic band gap of our proposed optical magnetized plasma waveguide. Our outcomes demonstrate the potential applications of the device for tunable and adjustable filters or reflectors and active magneto-optic in microwave devices under structural parameter and external magnetic field.« less

Scattering rings in optically anisotropic porous silicon

NASA Astrophysics Data System (ADS)

Oton, C. J.; Gaburro, Z.; Ghulinyan, M.; Pancheri, L.; Bettotti, P.; Negro, L. Dal; Pavesi, L.

2002-12-01

We report the observation of strongly anisotropic scattering of laser light at oblique incidence on a (100)-oriented porous silicon layer. The scattered light forms cones tangent to the incident and reflected beams. The conical pattern is caused by scattering on the vertical walls of pores, which are straight along the layer thickness. The light cone defines structured light rings onto a screen normal to the cone axis. We explain the various structures by optical anisotropy of porous silicon. For the sample under analysis, we directly measure from the ring patterns a value of Δn/nord=8% of positive birefringence.

Optical properties of marine stratocumulus clouds modified by ship track effluents

NASA Technical Reports Server (NTRS)

King, Michael D.; Nakajima, Teruyuki; Radke, Lawrence F.

1990-01-01

Results are presented from multispectral radiation measurements made within a marine stratocumulus cloud layer modified by ship-track effluents. The measurements showed that, compared with nearby noncontaminated clouds not affected by pollution, the upwelling intensity field of the modified stratocumulus clouds increased at a nonabsorbing wavelength in the visible region and decreased in the NIR, where absorption by liquid water is significant. The observations are consistent with an increased optical thickness, a reduced effective radius of the cloud droplets, and a reduced absorption in the contaminated cloud layer compared to a noncontaminated cloud.

Increased magnetic damping in ultrathin films of Co2FeAl with perpendicular anisotropy

NASA Astrophysics Data System (ADS)

Takahashi, Y. K.; Miura, Y.; Choi, R.; Ohkubo, T.; Wen, Z. C.; Ishioka, K.; Mandal, R.; Medapalli, R.; Sukegawa, H.; Mitani, S.; Fullerton, E. E.; Hono, K.

2017-06-01

We estimated the magnetic damping constant α of Co2FeAl (CFA) Heusler alloy films of different thicknesses with an MgO capping layer by means of time-resolved magneto-optical Kerr effect and ferromagnetic resonance measurements. CFA films with thicknesses of 1.2 nm and below exhibited perpendicular magnetic anisotropy arising from the presence of the interface with MgO. While α increased gradually with decreasing CFA film thickness down to 1.2 nm, it was increased substantially when the thickness was reduced further to 1.0 nm. Based on the microstructure analyses and first-principles calculations, we attributed the origin of the large α in the ultrathin CFA film primarily to the Al deficiency in the CFA layer, which caused an increase in the density of states and thereby in the scatterings of their spins.

Retinal Layers Measurements following Silicone Oil Tamponade for Retinal Detachment Surgery.

PubMed

Jurišić, Darija; Geber, Mia Zorić; Ćavar, Ivan; Utrobičić, Dobrila Karlica

2017-12-19

This study aimed to investigate the influence of silicone oil on the retinal nerve fiber layer (RNFL) thickness in patients with primary rhegmatogenous retinal detachment who underwent vitreoretinal surgery. The study included 47 patients (eyes), who underwent a pars plana vitrectomy with the silicone oil tamponade. The control group included unoperated eye of all participants. Spectral-domain optical coherence tomography (SD-OCT) was used for the measurements of peripapilar and macular RNFL thickness. The average peripapillary RNFL thickness was significantly higher in the silicone oil filled eyes during endotamponade and after its removal. The eyes with elevated IOP had less thickening of the RNFL in comparison to the eyes with normal IOP. Central macular thickness and macular volume were decreased in the silicone oil filled eyes in comparison to the control eyes. In conclusion, silicone oil caused peripapilar RNFL thickening in the vitrectomized eyes during endotamponade and after silicone oil removal.

Retinal Layer Abnormalities as Biomarkers of Schizophrenia.

PubMed

Samani, Niraj N; Proudlock, Frank A; Siram, Vasantha; Suraweera, Chathurie; Hutchinson, Claire; Nelson, Christopher P; Al-Uzri, Mohammed; Gottlob, Irene

2018-06-06

Schizophrenia is associated with several brain deficits, as well as visual processing deficits, but clinically useful biomarkers are elusive. We hypothesized that retinal layer changes, noninvasively visualized using spectral-domain optical coherence tomography (SD-OCT), may represent a possible "window" to these abnormalities. A Leica EnvisuTM SD-OCT device was used to obtain high-resolution central foveal B-scans in both eyes of 35 patients with schizophrenia and 50 demographically matched controls. Manual retinal layer segmentation was performed to acquire individual and combined layer thickness measurements in 3 macular regions. Contrast sensitivity was measured at 3 spatial frequencies in a subgroup of each cohort. Differences were compared using adjusted linear models and significantly different layer measures in patients underwent Spearman Rank correlations with contrast sensitivity, quantified symptoms severity, disease duration, and antipsychotic medication dose. Total retinal and photoreceptor complex thickness was reduced in all regions in patients (P < .0001). Segmentation revealed consistent thinning of the outer nuclear layer (P < .001) and inner segment layer (P < .05), as well as a pattern of parafoveal ganglion cell changes. Low spatial frequency contrast sensitivity was reduced in patients (P = .002) and correlated with temporal parafoveal ganglion cell complex thinning (R = .48, P = .01). Negative symptom severity was inversely correlated with foveal photoreceptor complex thickness (R = -.54, P = .001) and outer nuclear layer thickness (R = -.47, P = .005). Our novel findings demonstrate considerable retinal layer abnormalities in schizophrenia that are related to clinical features and visual function. With time, SD-OCT could provide easily-measurable biomarkers to facilitate clinical assessment and further our understanding of the disease.

Design and fabrication of adjustable x-ray optics using piezoelectric thin films

NASA Astrophysics Data System (ADS)

Walker, J.; Liu, T.; Tendulkar, M.; Burrows, D.; DeRoo, C. T.; Allured, R.; Hertz, E.; Cotroneo, V.; Reid, P.; Schwartz, E. D.; Jackson, T. N.; Trolier-McKinstry, S.

2017-08-01

Piezoelectric adjustable optics are being developed for high throughput, high resolution, low mass Xray mirror assemblies. These optics require robust piezoelectric thin films and reproducible lithographic patterning on curved glass substrates. This work details the cleaning of Corning Eagle XG glass substrates for thin shell X-ray mirrors by a three stage acid and solvent cleaning procedure before a 0.02 μm Ti adhesion layer and a 0.1 μm Pt bottom electrode layer was deposited using DC magnetron sputtering. Piezoelectric Pb(Zr0.52Ti0.48)0.99Nb0.01O3 thin films with a thickness of 1.5 μm were then deposited by radio frequency magnetron sputtering in three 0.5 µm layers with intermittent annealing steps in a rapid thermal annealing furnace at 650°C for 60 seconds. Defects observed in the piezoelectric thin films were linked to residue remaining on the glass after cleaning. 112 piezoelectric cells and 100 μm wide conductive Pt traces were patterned using bilayer photolithography. The photoresist layers were deposited using spin coating at 2000 and 4000 RPM to achieve uniform 1 μm thick layers, resulting in reproducibly resolved features with limiting resolutions of approximately >25 μm. The resulting mirror pieces achieved a 100% yield, with average relative permittivity of 1270, dielectric loss 0.047, coercive field 30 kV/cm and remanent polarization of 20 μC/cm2 . While the defects observed in the films appeared to have not influence on the electrical properties, additional cleaning steps using DI water were proposed to further reduce their presence.

Substrate Oxide Layer Thickness Optimization for a Dual-Width Plasmonic Grating for Surface-Enhanced Raman Spectroscopy (SERS) Biosensor Applications

PubMed Central

Bauman, Stephen J.; Brawley, Zachary T.; Darweesh, Ahmad A.; Herzog, Joseph B.

2017-01-01

This work investigates a new design for a plasmonic SERS biosensor via computational electromagnetic models. It utilizes a dual-width plasmonic grating design, which has two different metallic widths per grating period. These types of plasmonic gratings have shown larger optical enhancement than standard single-width gratings. The new structures have additional increased enhancement when the spacing between the metal decreases to sub-10 nm dimensions. This work integrates an oxide layer to improve the enhancement even further by carefully studying the effects of the substrate oxide thickness on the enhancement and reports ideal substrate parameters. The combined effects of varying the substrate and the grating geometry are studied to fully optimize the device’s enhancement for SERS biosensing and other plasmonic applications. The work reports the ideal widths and substrate thickness for both a standard and a dual-width plasmonic grating SERS biosensor. The ideal geometry, comprising a dual-width grating structure atop an optimal SiO2 layer thickness, improves the enhancement by 800%, as compared to non-optimized structures with a single-width grating and a non-optimal oxide thickness. PMID:28665308

Imaging retinal nerve fiber bundles using optical coherence tomography with adaptive optics.

PubMed

Kocaoglu, Omer P; Cense, Barry; Jonnal, Ravi S; Wang, Qiang; Lee, Sangyeol; Gao, Weihua; Miller, Donald T

2011-08-15

Early detection of axonal tissue loss in retinal nerve fiber layer (RNFL) is critical for effective treatment and management of diseases such as glaucoma. This study aims to evaluate the capability of ultrahigh-resolution optical coherence tomography with adaptive optics (UHR-AO-OCT) for imaging the RNFL axonal bundles (RNFBs) with 3×3×3μm(3) resolution in the eye. We used a research-grade UHR-AO-OCT system to acquire 3°×3° volumes in four normal subjects and one subject with an arcuate retinal nerve fiber layer defect (n=5; 29-62years). Cross section (B-scans) and en face (C-scan) slices extracted from the volumes were used to assess visibility and size distribution of individual RNFBs. In one subject, we reimaged the same RNFBs twice over a 7month interval and compared bundle width and thickness between the two imaging sessions. Lastly we compared images of an arcuate RNFL defect acquired with UHR-AO-OCT and commercial OCT (Heidelberg Spectralis). Individual RNFBs were distinguishable in all subjects at 3° retinal eccentricity in both cross-sectional and en face views (width: 30-50μm, thickness: 10-15μm). At 6° retinal eccentricity, RNFBs were distinguishable in three of the five subjects in both views (width: 30-45μm, thickness: 20-40μm). Width and thickness RNFB measurements taken 7months apart were strongly correlated (p<0.0005). Mean difference and standard deviation of the differences between the two measurement sessions were -0.1±4.0μm (width) and 0.3±1.5μm (thickness). UHR-AO-OCT outperformed commercial OCT in terms of clarity of the microscopic retina. To our knowledge, these are the first measurements of RNFB cross section reported in the living human eye. Copyright © 2011 Elsevier Ltd. All rights reserved.