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Sample records for absolute refractive index

  1. Full field imaging based instantaneous hyperspectral absolute refractive index measurement

    SciTech Connect

    Baba, Justin S; Boudreaux, Philip R

    2012-01-01

    Multispectral refractometers typically measure refractive index (RI) at discrete monochromatic wavelengths via a serial process. We report on the demonstration of a white light full field imaging based refractometer capable of instantaneous multispectral measurement of absolute RI of clear liquid/gel samples across the entire visible light spectrum. The broad optical bandwidth refractometer is capable of hyperspectral measurement of RI in the range 1.30 1.70 between 400nm 700nm with a maximum error of 0.0036 units (0.24% of actual) at 414nm for a = 1.50 sample. We present system design and calibration method details as well as results from a system validation sample.

  2. Temperature-dependent Absolute Refractive Index Measurements of Synthetic Fused Silica

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Frey, Bradley J.

    2006-01-01

    Using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have measured the absolute refractive index of five specimens taken from a very large boule of Corning 7980 fused silica from temperatures ranging from 30 to 310 K at wavelengths from 0.4 to 2.6 microns with an absolute uncertainty of plus or minus 1 x 10 (exp -5). Statistical variations in derived values of the thermo-optic coefficient (dn/dT) are at the plus or minus 2 x 10 (exp -8)/K level. Graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient are presented for selected wavelengths and temperatures along with estimates of uncertainty in index. Coefficients for temperature-dependent Sellmeier fits of measured refractive index are also presented to allow accurate interpolation of index to other wavelengths and temperatures. We compare our results to those from an independent investigation (which used an interferometric technique for measuring index changes as a function of temperature) whose samples were prepared from the same slugs of material from which our prisms were prepared in support of the Kepler mission. We also compare our results with sparse cryogenic index data from measurements of this material from the literature.

  3. Absolute real-time determination of size and refractive index of individual microspheres

    NASA Astrophysics Data System (ADS)

    Maltsev, V. P.; Chernyshev, A. V.; Sem'yanov, K. A.; Soini, E.

    1997-09-01

    The flying light scattering indicatrix (FLSI) method has been improved by employing a set of empirical equations combined with a decision tree which has been used for simultaneous real-time measurements and calculation of the size and refractive index of individual spherical particles. Empirical equations have been developed for determination of particle parameters over the range 0957-0233/8/9/011/img9m to 0957-0233/8/9/011/img10m and 1.37 to 1.60 for size and refractive index respectively. The FLSI method has been used for determination of the precision of a scanning flow cytometer for analysis of individual particles. A two-dimensional map (size X refractive index) was created for polystyrene latex and milk fat particles.

  4. High-accuracy interferometer with a prism pair for measurement of the absolute refractive index of glass

    SciTech Connect

    Hori, Yasuaki; Hirai, Akiko; Minoshima, Kaoru; Matsumoto, Hirokazu

    2009-04-10

    We propose a variable-path interferometric technique for the measurement of the absolute refractive index of optical glasses. We use two interferometers to decide the ratio between changes in the optical path in a prism-shaped sample glass and in air resulting from displacement of the sample. The method allows precise measurements to be made without prior knowledge of the properties of the sample. The combined standard uncertainty of the proposed method is 1.6x10{sup -6}.

  5. Gradient Refractive Index Lenses.

    ERIC Educational Resources Information Center

    Morton, N.

    1984-01-01

    Describes the nature of gradient refractive index (GRIN) lenses, focusing on refraction in these materials, focal length of a thin Wood lens, and on manufacturing of such lenses. Indicates that GRIN lenses of small cross section are in limited production with applications suggested for optical communication and photocopying fields. (JN)

  6. Measurement of absolute cell volume, osmotic membrane water permeability, and refractive index of transmembrane water and solute flux by digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Boss, Daniel; Khn, Jonas; Jourdain, Pascal; Depeursinge, Christian; Magistretti, Pierre J.; Marquet, Pierre

    2013-03-01

    A dual-wavelength digital holographic microscope to measure absolute volume of living cells is proposed. The optical setup allows us to reconstruct two quantitative phase contrast images at two different wavelengths from a single hologram acquisition. When adding the absorbing dye fast green FCF as a dispersive agent to the extracellular medium, cellular thickness can be univocally determined in the full field of view. In addition to the absolute cell volume, the method can be applied to derive important biophysical parameters of living cells including osmotic membrane water permeability coefficient and the integral intracellular refractive index (RI). Further, the RI of transmembrane flux can be determined giving an indication about the nature of transported solutes. The proposed method is applied to cultured human embryonic kidney cells, Chinese hamster ovary cells, human red blood cells, mouse cortical astrocytes, and neurons.

  7. Measurement of absolute cell volume, osmotic membrane water permeability, and refractive index of transmembrane water and solute flux by digital holographic microscopy.

    PubMed

    Boss, Daniel; Khn, Jonas; Jourdain, Pascal; Depeursinge, Christian; Magistretti, Pierre J; Marquet, Pierre

    2013-03-01

    A dual-wavelength digital holographic microscope to measure absolute volume of living cells is proposed. The optical setup allows us to reconstruct two quantitative phase contrast images at two different wavelengths from a single hologram acquisition. When adding the absorbing dye fast green FCF as a dispersive agent to the extracellular medium, cellular thickness can be univocally determined in the full field of view. In addition to the absolute cell volume, the method can be applied to derive important biophysical parameters of living cells including osmotic membrane water permeability coefficient and the integral intracellular refractive index (RI). Further, the RI of transmembrane flux can be determined giving an indication about the nature of transported solutes. The proposed method is applied to cultured human embryonic kidney cells, Chinese hamster ovary cells, human red blood cells, mouse cortical astrocytes, and neurons. PMID:23487181

  8. Quantitative measurement of absolute cell volume and intracellular integral refractive index (RI) with dual-wavelength digital holographic microscopy (DHM)

    NASA Astrophysics Data System (ADS)

    Boss, Daniel; Kühn, Jonas; Depeursinge, Christian; Magistretti, Pierre J.; Marquet, Pierre

    2012-06-01

    Quantitative Phase Imaging techniques including DHM have been applied recently in the field of cell imaging to monitor and quantify non-invasively dynamic cellular processes modifying cell morphology and/or content . Concretely, the DHM phase signal is highly sensitive to cell thickness and intracellular integral RI variations associated with transmembrane water movements. As net water flow across the cell membrane leads at the same time to changes in cell thickness and intracellular RI, the interpretation of phase signal variations remains difficult. To overcome this drawback, we have developed a Dual-wavelength Digital Holographic Microscopy (DHM) setup allowing to separately measure, with a single CCD camera acquisition, thickness and integral RI of living cells. The method is based on the use of an absorbing dye that enhances the refractive index dispersion of the extracellular medium. Practically, two significantly different phase signals can be obtained when measuring at two appropriate wavelengths. From the two phase measurements, both cell RI and thickness can be univocally determined.

  9. Fiber optic refractive index monitor

    DOEpatents

    Weiss, Jonathan David (Albuquerque, NM)

    2002-01-01

    A sensor for measuring the change in refractive index of a liquid uses the lowest critical angle of a normal fiber optic to achieve sensitivity when the index of the liquid is significantly less than the index of the fiber core. Another embodiment uses a liquid filled core to ensure that its index is approximately the same as the liquid being measured.

  10. Measuring the Index of Refraction.

    ERIC Educational Resources Information Center

    Phelps, F. M., III; Jacobson, B. S.

    1980-01-01

    Presents two methods for measuring the index of refraction of glass or lucite. These two methods, used in the freshman laboratory, are based on the fact that a ray of light inside a block will be refracted parallel to the surface. (HM)

  11. Index of Refraction without Geometry

    ERIC Educational Resources Information Center

    Farkas, N.; Henriksen, P. N.; Ramsier, R. D.

    2006-01-01

    This article presents several activities that permit students to determine the index of refraction of transparent solids and liquids using simple equipment without the need for geometrical relationships, special lighting or optical instruments. Graphical analysis of the measured data is shown to be a useful method for determining the index of

  12. Index of Refraction without Geometry

    ERIC Educational Resources Information Center

    Farkas, N.; Henriksen, P. N.; Ramsier, R. D.

    2006-01-01

    This article presents several activities that permit students to determine the index of refraction of transparent solids and liquids using simple equipment without the need for geometrical relationships, special lighting or optical instruments. Graphical analysis of the measured data is shown to be a useful method for determining the index of…

  13. Refractive Index of Sodium Iodide

    SciTech Connect

    Jellison Jr, Gerald Earle; Boatner, Lynn A; Ramey, Joanne Oxendine; Kolopus, James A; Ramey, Lucas A; Singh, David J

    2012-01-01

    The refractive index of sodium iodide, an important scintillator material that is widely used for radiation detection, is based on a single measurement made by Spangenberg at one wavelength using the index-matching liquid immersion method (Z. Kristallogr., 57, 494-534 (1923)). In the present paper, we present new results for the refractive index of sodium iodide as measured by the minimum deviation technique at six wavelengths between 436 nm (n=1.839 0.002) and 633 nm (n=1.786 0.002). These 6 measurements can be fit to a Sellmeier model, resulting in a 2 of 1.02, indicating a good fit to the data. In addition, we report on ellipsometry measurements, which suggest that the near-surface region of the air sensitive NaI crystal seriously degrades, even in a moisture-free environment, resulting in a significantly lower value of the refractive index near the surface. First-principles theoretical calculations of the NaI refractive index that agree with the measured values within 0.025-0.045 are also presented and discussed.

  14. Determination of refractive index by Moir deflectometry

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mohammad; Madanipour, Khosro; Javadianvarjovi, Soheila

    2015-06-01

    Determination of refractive index is an important characteristic of material which is crucial parameter for physicists and engineers. Moir deflectometry technique is convenient, easy-aligning, nondestructive, non-contact and fairly accurate method for refractive index measurement of gas, liquid, solid. In this paper we investigate the theory of the technique and simulate some relations then finally measure refractive index of a glassy lamella, n=1.536.

  15. Photon mass and negative index of refraction

    NASA Astrophysics Data System (ADS)

    Grado-Caffaro, M. A.; Grado-Caffaro, M.

    2007-07-01

    A mathematical expression is established for negative refractive index within the context of non-zero photon rest-mass. From this expression, a key inequality involving the mass in question as a function of wavelength is derived. In addition, an approximate parabolic relationship for the refractive index is obtained.

  16. Refractive index of plant cell walls

    NASA Technical Reports Server (NTRS)

    Gausman, H. W.; Allen, W. A.; Escobar, D. E.

    1974-01-01

    Air was replaced with media of higher refractive indices by vacuum infiltration in leaves of cucumber, blackeye pea, tomato, and string bean plants, and reflectance of noninfiltrated and infiltrated leaves was spectrophotometrically measured. Infiltrated leaves reflected less light than noninfiltrated leaves over the 500-2500-nm wavelength interval because cell wall-air interfaces were partly eliminated. Minimal reflectance should occur when the average refractive index of plant cell walls was matched by the infiltrating fluid. Although refractive indices that resulted in minimal reflectance differed among the four plant genera, an average value of 1.425 approximates the refractive index of plant cell walls for the four plant genera.

  17. Formation of bulk refractive index structures

    DOEpatents

    Potter, Jr., Barrett George; Potter, Kelly Simmons; Wheeler, David R.; Jamison, Gregory M.

    2003-07-15

    A method of making a stacked three-dimensional refractive index structure in photosensitive materials using photo-patterning where first determined is the wavelength at which a photosensitive material film exhibits a change in refractive index upon exposure to optical radiation, a portion of the surfaces of the photosensitive material film is optically irradiated, the film is marked to produce a registry mark. Multiple films are produced and aligned using the registry marks to form a stacked three-dimensional refractive index structure.

  18. Refractive index measurement using comparative interferometry

    NASA Astrophysics Data System (ADS)

    Bojan, Mihaela; Apostol, D.; Damian, V.; Logofatu, P. C.; Garoi, F.; Iordache, Iuliana

    2007-05-01

    The refractive index of a material medium is an important optical parameter since it exhibits the optical properties of the material. The adulteration problem is increasing day by day and hence simple, automatic and accurate measurement of the refractive index of materials is of great importance these days. For solid thin films materials Abeles method was reconsidered. Quick, measurements of refractive index using simple techniques and refractometers can help controlling adulteration of liquids of common use to a greater extent. Very simple interferometric set-up using Fizeau fringe patterns compares the fringe pitch as obtained in a cell with two levels: one down level with the unknown refractive index liquids and the upper level with gas air. A CCD matrix and a PC can handle the data and produce the results up to for digits.

  19. On the effective refractive index of blood

    NASA Astrophysics Data System (ADS)

    Nahmad-Rohen, Alexander; Contreras-Tello, Humberto; Morales-Luna, Gesuri; Garca-Valenzuela, Augusto

    2016-01-01

    We calculated the real and imaginary parts of the effective refractive index {n}{eff} of blood as functions of wavelength from 400 to 800 nm; we employed van de Hulsts theory, together with the anomalous diffraction approximation, for the calculation. We modelled blood as a mixture of plasma and erythrocytes. Our results indicate that erythrocyte orientation has a strong effect on {n}{eff}, making blood an optically anisotropic medium except when the erythrocytes are randomly oriented. In the case in which their symmetry axis is perpendicular to the wave vector, {n}{eff} equals the refractive index of plasma at certain wavelengths. Furthermore, the erythrocytes shape affects their contribution to {n}{eff} in an important way, implying that studies on the effective refractive index of blood should avoid approximating them as spheres or spheroids. Finally, the effective refractive index of blood predicted by van de Hulsts theory is different from what would be obtained by averaging the refractive indices of its constituents weighted by volume; such a volume-weighted average is appropriate only for haemolysed blood. We then measured the real part of the refractive index of various blood solutions using two different experimental setups. One of the most important results of our expriment is that {n}{eff} is measurable to a good degree of precision even for undiluted blood, although not all measuring apparatuses are appropriate. The experimental data is self-consistent and in reasonable agreement with our theoretical calculations.

  20. Fiber optic liquid refractive index sensor

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Vanita; Gangwar, Rahul Kumar; Singh, Vinod Kumar

    2015-08-01

    In this present work we report fabrication of fiber optic liquid refractive index (RI) measurement sensor based on Michelson Interferometer method. This sensor was assembled by using graded index multimode (MM) fiber with core diameter 50 m and the cladding of fiber was removed by simple chemical method. To perform this experiment a 22 3dB coupler is used. The fiber ends are then immersed in solvent and solution to provide reference and refractive index measurements, respectively. This method was successfully used to measure refractive index of Sodium Chloride (NaCl)-Water solution at different concentrations. The fringe contrast sensitivity of device is 92.90 dB/RIU measured in the RI range from 1.34 to 1.42 which is better than Mach-Zehnder Interferometer sensor [1] and Fabry perot based sensor [2]. The fabrication of sensor is simple, low cost and highly sensitive.

  1. Refractive index change in dissociating shocked benzene

    SciTech Connect

    Erskine, D.J.

    1994-06-01

    A calculation is made of the refractive index of a shocked solution of hydrocarbon species and spheroidal carbon particles that would be the dissociation products of benzene. The results is evaluated for benzene shocked to 15 GPa, both for an arbitrary endpoint distribution of products and reactant, and for a specific endpoint distribution suggested by a statistical-mechanical calculation. In the case of diamond particles, the refractive index is predicted to decrease by a small amount (from 1.96 to 1.75) as the dissociation proceeds. In the case of graphite particles of large oblateness, the refractive index could increase significantly through the dissociation (from 1.96 to 2.75 for infinitely oblate platelets). Thus the measurement of the time dependent refractive index through the dissociation of shocked benzene can indicate the morphology of the carbon particulates as well as the time scale for this reaction. We propose using the refractive index as a measure of completion of the dissociation reaction. This would allow a determination of the instantaneous amount of carbon in particulate form, information which is valuable in conjunction with Mie scattering experiments for example.

  2. Thermal Expansion and Temperature Dependence of the Refractive Index in Gradient Refractive Index Glasses.

    NASA Astrophysics Data System (ADS)

    McLaughlin, Paul Oliver

    The thermal expansion and temperature dependence of the refractive index in gradient index glass have been investigated. These two thermal properties have been modeled as functions of local glass composition within the gradient index region. Additive relationships have been developed for gradient index glass from previous work done on homogeneous glass modeling. Computer programs have been written to calculate the expansion and change in refractive index due to thermal changes in the gradient index glass environment. A modified multiple Fabry-Perot interferometer was designed and built into an environmental temperature chamber to measure these thermal properties in gradient index glass in the range from 0-100 degrees Celcius. The interferometer operated under computer control to optically measure the differential expansion and change in refractive index profile in several samples of gradient index glass. The observed changes in thermal expansion and gradient index profile were also evaluated in terms of their effect on the imaging performance of a gradient index lens.

  3. Temperature-dependent Refractive Index of Silicon and Germanium

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.; Madison, Timothy J.

    2006-01-01

    Silicon and germanium are perhaps the two most well-understood semiconductor materials in the context of solid state device technologies and more recently micromachining and nanotechnology. Meanwhile, these two materials are also important in the field of infrared lens design. Optical instruments designed for the wavelength range where these two materials are transmissive achieve best performance when cooled to cryogenic temperatures to enhance signal from the scene over instrument background radiation. In order to enable high quality lens designs using silicon and germanium at cryogenic temperatures, we have measured the absolute refractive index of multiple prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For silicon, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 1.1 to 5.6 pin, while for germanium, we cover temperatures ranging from 20 to 300 K and wavelengths from 1.9 to 5.5 microns. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. Citing the wide variety of values for the refractive indices of these two materials found in the literature, we reiterate the importance of measuring the refractive index of a sample from the same batch of raw material from which final optical components are cut when absolute accuracy greater than k5 x 10" is desired.

  4. Cosmology with a dark refraction index

    SciTech Connect

    Chen, B.; Kantowski, R.

    2008-08-15

    We review Gordon's optical metric and the transport equations for the amplitude and polarization of a geometrical optics wave traveling in a gravity field. We apply the theory to the Friedmann-Lemaitre-Robertson-Walker cosmologies by associating a refraction index with the cosmic fluid. We then derive an expression for the accumulated effect of a refraction index on the distance-redshift relations and fit the Hubble curve of current supernova observations with a nonaccelerating cosmological model. We also show that some observational effects caused by inhomogeneities, e.g., the Sachs-Wolfe effect, can be interpreted as being caused by an effective index of refraction, and hence this theory could extend to other speed of light communications such as gravitational radiation and neutrino fluxes.

  5. Plasmonic crystal enhanced refractive index sensing

    SciTech Connect

    Stein, Benedikt; Devaux, Eloïse; Genet, Cyriaque Ebbesen, Thomas W.

    2014-06-23

    We demonstrate experimentally how the local anisotropy of the dispersion relation of surface plasmon modes propagating over periodic metal gratings can lead to an enhancement of the figure of merit of refractive index sensors. Exploiting the possibility to acquire defocused images of the Fourier space of a highly stable leakage radiation microscope, we report a twofold increase in sensing sensitivity close to the band gap of a one-dimensional plasmonic crystal where the anisotropy of the band structure is the most important. A practical sensing resolution of O(10{sup −6}) refractive index units is demonstrated.

  6. A metamaterial cavity for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Bhattarai, Khagendra; Ku, Zahyun; Zhou, Jiangfeng; Air Force Research Laboratory Collaboration; University of South Florida Team

    2014-03-01

    In this work, we demonstrated a metamaterial cavity consists of plasmonic metasurfaces made of gold nano-disks. We have shown that the Fabry-Perot cavity resonant modes arise around the plasmonic resonance wavelength. Compared to the localized plasmonic resonances, the quality factor of the cavity resonance is significantly increased. The cavity resonances are very sensitive to the refractive index of the surrounding materials. More importantly, the higher order cavity modes can further reduce the losses and improve the sensitivity. Numerical simulations show that the reflection shifts by 80% when the refractive index of the surrounding liquid material changes from 1.312 to 1.352.

  7. Complex refractive index of turbid liquids.

    PubMed

    Niskanen, Ilpo; Rty, Jukka; Peiponen, Kai-Erik

    2007-04-01

    We present a multifunction spectrophotometer for the measurement of light reflection from thick and transmission from very thin turbid liquid samples. Moreover, we present a method to get the complex refractive index of such turbid liquids. As an example of the high performance of the device and the method, we present data on inks that are used in offset printing. PMID:17339962

  8. Matched Index of Refraction Flow Facility

    ScienceCinema

    Mcllroy, Hugh

    2013-05-28

    What's 27 feet long, 10 feet tall and full of mineral oil (3000 gallons' worth)? If you said INL's Matched Index of Refraction facility, give yourself a gold star. Scientists use computers to model the inner workings of nuclear reactors, and MIR helps validate those models. INL's Hugh McIlroy explains in this video. You can learn more about INL energy research at the lab's facebook site http://www.facebook.com/idahonationallaboratory.

  9. Matched Index of Refraction Flow Facility

    SciTech Connect

    Mcllroy, Hugh

    2010-01-01

    What's 27 feet long, 10 feet tall and full of mineral oil (3000 gallons' worth)? If you said INL's Matched Index of Refraction facility, give yourself a gold star. Scientists use computers to model the inner workings of nuclear reactors, and MIR helps validate those models. INL's Hugh McIlroy explains in this video. You can learn more about INL energy research at the lab's facebook site http://www.facebook.com/idahonationallaboratory.

  10. Scanning focused refractive-index microscopy

    PubMed Central

    Sun, Teng-Qian; Ye, Qing; Wang, Xiao-Wan; Wang, Jin; Deng, Zhi-Chao; Mei, Jian-Chun; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

    2014-01-01

    We present a novel scanning focused refractive-index microscopy (SFRIM) technique to obtain the refractive index (RI) profiles of objects. The method uses a focused laser as the light source, and combines the derivative total reflection method (DTRM), projection magnification, and scanning technique together. SFRIM is able to determine RIs with an accuracy of 0.002, and the central spatial resolution achieved is 1 µm, which is smaller than the size of the focal spot. The results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, verifying the accuracy of SFRIM. Furthermore, using SFRIM, to the best of our knowledge we have extracted for the first time the RI profile of a periodically modulated photosensitive gelatin sample. SFRIM is the first RI profile-resolved reflected light microscopy technique that can be applied to scattering and absorbing samples. SFRIM enables the possibility of performing RI profile measurements in a variety of applications, including optical waveguides, photosensitive materials and devices, photorefractive effect studies, and RI imaging in biomedical fields. PMID:25008374

  11. Scanning focused refractive-index microscopy

    NASA Astrophysics Data System (ADS)

    Sun, Teng-Qian; Ye, Qing; Wang, Xiao-Wan; Wang, Jin; Deng, Zhi-Chao; Mei, Jian-Chun; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

    2014-07-01

    We present a novel scanning focused refractive-index microscopy (SFRIM) technique to obtain the refractive index (RI) profiles of objects. The method uses a focused laser as the light source, and combines the derivative total reflection method (DTRM), projection magnification, and scanning technique together. SFRIM is able to determine RIs with an accuracy of 0.002, and the central spatial resolution achieved is 1 m, which is smaller than the size of the focal spot. The results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, verifying the accuracy of SFRIM. Furthermore, using SFRIM, to the best of our knowledge we have extracted for the first time the RI profile of a periodically modulated photosensitive gelatin sample. SFRIM is the first RI profile-resolved reflected light microscopy technique that can be applied to scattering and absorbing samples. SFRIM enables the possibility of performing RI profile measurements in a variety of applications, including optical waveguides, photosensitive materials and devices, photorefractive effect studies, and RI imaging in biomedical fields.

  12. Tissue refractive index as marker of disease

    NASA Astrophysics Data System (ADS)

    Wang, Zhuo; Tangella, Krishnarao; Balla, Andre; Popescu, Gabriel

    2011-11-01

    The gold standard in histopathology relies on manual investigation of stained tissue biopsies. A sensitive and quantitative method for in situ tissue specimen inspection is highly desirable, as it would allow early disease diagnosis and automatic screening. Here we demonstrate that quantitative phase imaging of entire unstained biopsies has the potential to fulfill this requirement. Our data indicates that the refractive index distribution of histopathology slides, which contains information about the molecular scale organization of tissue, reveals prostate tumors and breast calcifications. These optical maps report on subtle, nanoscale morphological properties of tissues and cells that cannot be recovered by common stains, including hematoxylin and eosin. We found that cancer progression significantly alters the tissue organization, as exhibited by consistently higher refractive index variance in prostate tumors versus normal regions. Furthermore, using the quantitative phase information, we obtained the spatially resolved scattering mean free path and anisotropy factor g for entire biopsies and demonstrated their direct correlation with tumor presence. In essence, our results show that the tissue refractive index reports on the nanoscale tissue architecture and, in principle, can be used as an intrinsic marker for cancer diagnosis.

  13. Microwave gain medium with negative refractive index

    NASA Astrophysics Data System (ADS)

    Ye, Dexin; Chang, Kihun; Ran, Lixin; Xin, Hao

    2014-12-01

    Artificial effective media are attractive because of the fantastic applications they may enable, such as super lensing and electromagnetic invisibility. However, the inevitable loss due to their strongly dispersive nature is one of the fundamental challenges preventing such applications from becoming a reality. In this study, we demonstrate an effective gain medium based on negative resistance, to overcompensate the loss of a conventional passive metamaterial, meanwhile keeping its original negative-index property. Energy conservation-based theory, full-wave simulation and experimental measurement show that a fabricated sample consisting of conventional sub-wavelength building blocks with embedded microwave tunnel diodes exhibits a band-limited Lorentzian dispersion simultaneously with a negative refractive index and a net gain. Our work provides experimental evidence to the assertion that a stable net gain in negative-index gain medium is achievable, proposing a potential solution for the critical challenge current metamateiral technology faces in practical applications.

  14. Measurement of refractive index distribution of biotissues by scanning focused refractive index microscopy

    NASA Astrophysics Data System (ADS)

    Sun, Tengqian; Ye, Qing; Wang, Xiao-Wan; Wang, Jin; Deng, Zhi-Chao; Mei, Jian-Chun; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

    2014-11-01

    We adapt the improved scanning focused refractive-index microscopy (SFRIM) technique to the quantitative study of biological tissues. Delicate refractive index (RI) imaging of a porcine muscle tissue is obtained in a reflection mode. Some modifications are made to the SFRIM for better two dimension (2-D) observation of the tissues. The RI accuracy is 0.002. The central spatial resolution of SFRIM achieves 1?m, smaller than the size of the focal spot. Our method is free from signal distortion. The experimental result demonstrates that SFRIM is a potential technique in a wide field of biomedical research.

  15. Measurement of Refractive Index Using a Michelson Interferometer.

    ERIC Educational Resources Information Center

    Fendley, J. J.

    1982-01-01

    Describes a novel and simple method of measuring the refractive index of transparent plates using a Michelson interferometer. Since it is necessary to use a computer program when determining the refractive index, undergraduates could be given the opportunity of writing their own programs. (Author/JN)

  16. Refractive index matching using a diethyl phthalate/ ethanol solution

    NASA Astrophysics Data System (ADS)

    Miller, Paul; Slifka, Andy; Moody, Galan

    2005-11-01

    When studying internal fluid velocity fields of complex geometries such as in vitro cardiovascular models, refractive index matching is critical for undistorted images. A diethyl phthalate (DEP) / ethanol mixture is a good choice of working fluid due to the high index of refraction, low viscosity, safety and low cost. The mixture can be tuned to the refractive index of borosilicate glasses, fused quartz and silicone elastomers. Silicone elastomers do not cloud in DEP/ethanol solutions and also tested negative for change in compliance after DEP exposure. Material compatibility tests showed that only specific formulations of ABS, acrylic, vinyl and PVC plastics are compatible. Measurements were made of index of refraction and viscosity of varied DEP/ ethanol solutions at a range of temperatures, and empirical models for viscosity and refractive index will be presented.

  17. A new method for measuring the refractive index of glass

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Su, Xian-yuan; Yang, Yan-min; Mi, Chao

    2013-12-01

    It is well known in optics that the refractive index is an important optical parameter of material. A novel method to measure refractive index of glass has been reported in this paper. This method can be used to measure the refractive index of the special laboratory prepared glass which is small, irregularly shaped by measuring its absorption spectrum. And we have measured the refractive index of the laboratory prepared germanium-lead glass (1) (70GeO2-10Pb-10BaO -10K2O), germanium-lead glass (2) (60GeO2-20Pb-10BaO-10K2O)?germanium-lead glass (3) (50GeO2-30Pb-10BaO-10K2O) by measuring the absorption spectra of them with the new method. The experiment results show that the peaks position of the absorption shift forward the long wavelength and the refractive indexes increase with the increasing of Pb in germanium lead glasses. The above obtained refractive indexes are similar with the data which measured by the spectroscopic ellipsometry and the error less than 1%. The error analysis indicates that this method has high degree accuracy. We predict that the new method has a potential application in refractive index measurement for glass.

  18. Computed tomography of refractive index by low-coherence interferometry

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Ma, Zhenhe; Zhou, Hongxian

    2015-03-01

    We present a 3D imaging system for simultaneously imaging the distributions of refractive index and optical absorption using a transmission Fourier-domain low-coherence interferometer. The forward-scattering light travelling through a sample interferes with a reference light beam. The projections of refractive index and optical absorption within the sample are calculated from measured interference fringes. We acquire the projections at sufficient angular views and reconstruct the distributions of refractive index and optical absorption using the filter back-projection algorithm. The proposed method is experimentally verified by using a plastic tube phantom.

  19. Metamaterial optical refractive index sensor detected by the naked eye

    NASA Astrophysics Data System (ADS)

    Wang, Xiaonong; Luo, Chunrong; Hong, Gang; Zhao, Xiaopeng

    2013-03-01

    An optical refractive index sensor that can be detected by the naked eye is presented in this paper. The sensor is developed based on the theory that metamaterials can completely absorb incident electric and magnetic field near its resonant frequencies. By inserting different mediums in the sensor or by dropping the mediums on the surface of the sensor, we detect the medium with a different refractive index through qualitative and quantitative analysis. The sensor is convenient for the detection of the liquid refractive index.

  20. Analyzing refractive index changes and differential bending in microcantilever arrays

    NASA Astrophysics Data System (ADS)

    Huber, Franois; Lang, Hans Peter; Hegner, Martin; Despont, Michel; Drechsler, Ute; Gerber, Christoph

    2008-08-01

    A new microcantilever array design is investigated comprising eight flexible microcantilevers introducing two solid bars, enabling to subtract contributions from differences in refractive index in an optical laser read out system. Changes in the refractive index do not contribute undesirably to bending signals at picomolar to micromolar DNA or protein concentrations. However, measurements of samples with high salt concentrations or serum are affected, requiring corrections for refractive index artifacts. Moreover, to obtain a deeper understanding of molecular stress formation, the differential curvature of cantilevers is analyzed by positioning the laser spots along the surface of the levers during pH experiments.

  1. Charged-particle acceleration through decreasing refractive index

    NASA Astrophysics Data System (ADS)

    Kong, Ling-Bao; Chen, Zhaoyang; Liu, Pu-Kun; Yu, Ming Young

    2015-02-01

    We propose a mechanism for electron acceleration in which circularly polarized electromagnetic waves (CPEMW) propagate along a uniform magnetic field in a medium with a tapered refractive index. Results show that with a decreasing refractive index and a moderate CPEMW electric field, e.g., 1.20 108 V/m, the relativistic factor of an electron can go above 14 after it travels 10 cm in the direction of CPEMW propagation. Without tapering of the refractive index, the maximum value of the relativistic factor is less than 2.92 under the same wave and guiding magnetic field conditions. Similar acceleration efficiency is found for electrons with different initial velocities.

  2. Novel methacrylated diamondoid to produce high-refractive index polymer

    NASA Astrophysics Data System (ADS)

    Takano, Tadashi; Lin, Yuan-Chang; Shi, Frank G.; Carlson, Bob; Sciamanna, Steven

    2010-03-01

    A novel, high-refractive index, methacrylic monomer was produced by incorporating 1-diamantane-carboxylic acid (1-D2-CA) and glycidyl methacrylate (GMA). The resulting monomer was gently polymerized with organic peroxide, and was formed transparent polymer thin film. Physicochemical and optical properties were compared with isobornyl methacrylate (IBoMA) homo-polymer film. 1-D2-CA/GMA homo-polymer reveals that the refractive index is 1.56, and the softening temperature is 107.8 C. High thermal stability and high-refractive index of 1-D2-CA/GMA homo-polymer indicate the potential use in optical applications.

  3. Optical tomography for smooth-changing refraction index distribution

    NASA Astrophysics Data System (ADS)

    de la Rosa Miranda, Enrique; Berriel-Valdos, Luis R.; Funes-Gallanzi, Marcelo; Fernandez Orozco, S. A.

    2002-06-01

    We propose an algebraic reconstruction method (ART) based on smooth functions to obtain the refraction index distribution of a radially symmetric phase object. Recovering the refraction index of a transversal section enables us to obtain some other physical variables such as temperature, pressure, etc. Considering phase objects with a radially symmetric distribution allows the recovery of information regarding the volumetric distribution of the refraction index based on a single projection. The proposed method is accurate, faster, and somewhat easier to implement than other currently used ART methods. As a sample application, the proposed method is applied to a burning candle case.

  4. Media with zero refractive index at a preset frequency

    NASA Astrophysics Data System (ADS)

    Averbukh, B. B.

    2015-12-01

    The refraction of a plane s-polarized electromagnetic wave on the vacuum-metamaterial interface is considered. It is established that, under certain conditions, a medium consisting of electric and magnetic dipoles or entirely of electric dipoles can behave as possessing a zero refractive index at a preset frequency.

  5. Determining the Thickness and Refractive Index of a Mirror

    ERIC Educational Resources Information Center

    Uysal, Ahmet

    2010-01-01

    When a laser beam reflects from a back surface glass mirror and falls on a screen, a pattern of discrete bright spots is created by partial reflection and refraction of the light at the air-glass interface and reflection at the mirror surface (Fig. 1). This paper explains how this phenomenon can be used to determine the refractive index and the…

  6. Determining the Thickness and Refractive Index of a Mirror

    ERIC Educational Resources Information Center

    Uysal, Ahmet

    2010-01-01

    When a laser beam reflects from a back surface glass mirror and falls on a screen, a pattern of discrete bright spots is created by partial reflection and refraction of the light at the air-glass interface and reflection at the mirror surface (Fig. 1). This paper explains how this phenomenon can be used to determine the refractive index and the

  7. Automated measurement of the refractive index of fluids

    SciTech Connect

    Pixton, Bruce M.; Greivenkamp, John E

    2008-04-01

    A method for automating refractive-index measurements of fluids has been developed. An encoded rotation stage and position-sensitive detector enable automated reading of angles typically acquired by visual means. Two tunable lasers are used to obtain index measurements at ten discrete wavelengths across the visible spectrum. This method has been implemented on a Hilger-Chance refractometer from which the bulk refractive-index values for various transparent fluids have been measured. An index measurement accuracy of better than one part in the fourth decimal place for distilled water and a few parts in the fourth decimal place for higher index fluids is obtained.

  8. Index of refraction of molecular nitrogen for sodium matter waves

    NASA Astrophysics Data System (ADS)

    Loreau, J.; Kharchenko, V.; Dalgarno, A.

    2013-01-01

    We calculate the index of refraction of sodium matter waves propagating through a gas of nitrogen molecules. We use a recent ab initio potential for the ground state of the NaN2 van der Waals complex to perform quantal close-coupling calculations and compute the index of refraction as a function of the projectile velocity. We obtain good agreement with the available experimental data. We show that the refractive index contains glory oscillations but that they are damped by the averaging over the thermal motion of the N2 molecules. These oscillations appear at lower temperatures and projectile velocity. We also investigate the behavior of the refractive index at low temperature and low projectile velocity to show its dependence on the rotational state of N2 and discuss the advantage of using diatomic molecules as projectiles.

  9. Negative refractive index in ferromagnetic semiconductors: experimental verification

    NASA Astrophysics Data System (ADS)

    Kussow, Adil-Gerai; Ait El Aoud, Yassine; Jaradat, Hamzeh M.; Akyurtlu, Alkim

    In this work, we show that natural crystals, or magnetic semiconductor, Cr-doped indium oxide, has a negative refractive index at ~ 27.8 micron wavelength. The effect was predicted by two of us a few years ago (A.G. Kussow and A. Akyurtlu, Phys. Rev. B, 78, 205202 (2008)). Our result seriously undermines wide-spread opinion that only composite artificial metamaterials can demonstrate negative refractive index. Thin ferromagnetic films of ICO were fabricated by original post-annealing sputtering method. FTIR R and T measurements were processed to extract refractive index within the range of interest. The extracted from combined transmittance and reflectance FTIR data negative refractive index band parameters are found to be close to expected one.

  10. Miniature interferometer for refractive index measurement in microfluidic chip

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Geiser, Martial; Truffer, Frederic; Song, Chengli

    2012-12-01

    The design and development of the miniaturized interferometer for measurement of the refractive index or concentration of sub-microliter volume aqueous solution in microfludic chip is presented. It is manifested by a successful measurement of the refractive index of sugar-water solution, by utilizing a laser diode for light source and the small robust instrumentation for practical implementation. Theoretically, the measurement principle and the feasibility of the system are analyzed. Experimental device is constructed with a diode laser, lens, two optical plate and a complementary metal oxide semiconductor (CMOS). Through measuring the positional changes of the interference fringes, the refractive index change are retrieved. A refractive index change of 10-4 is inferred from the measured image data. The entire system is approximately the size of half and a deck of cards and can operate on battery power for long time.

  11. Spatially Varying Index of Refraction: An Open Ended Undergraduate Topic.

    ERIC Educational Resources Information Center

    Krueger, David A.

    1980-01-01

    Presents an experiment on the bending of light in a medium with a continuously varying index of refraction. Several theoretical approaches for the analysis of this experiment, designed for college physics students, are also presented. (HM)

  12. Refractive-index-profile determinations by using Lloyd's mirage.

    PubMed

    Allman, B E; Klein, A G; Nugent, K A; Opat, G I

    1994-04-01

    A method is presented for the experimental determination of refractive-index profiles for planar media of monotonically decreasing refractive index, such as those used for optical waveguides. The technique is based on a generalization of the classical experiment of Lloyd's mirror, involving the interference pattern formed by a point source and its mirage, i.e., its reflection in such a graded planar medium. PMID:20885511

  13. Temperature dependence of the refractive index of optical fibers

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Yong; Qiu, Qi; Shi, Shuang-Jin

    2014-03-01

    Many experimental investigations on the temperature dependence of the refractive index of optical fibers have been reported previously, however a satisfying theoretical explanation for it is still absent. In this paper, a theoretical model about the temperature dependence of the refractive index of optical fibers is presented and it is in agreement with the previous experimental results. This work is a significant reference for the research and development of temperature sensors based on optical fiber delay lines.

  14. Refractive index profile determinations using a Lloyd's mirage

    NASA Astrophysics Data System (ADS)

    Allman, Brendan E.; Klein, Anthony G.; Nugent, Keith A.; Opat, Geoffrey I.

    1993-11-01

    A novel method is presented for the experimental determination of refractive index profiles for planar media of monotonically decreasing refractive index, such as those used for optical waveguides. The technique is based upon a generalization of the classical experiment of Lloyd's Mirror, involving the interference pattern formed by a point source and its mirage, i.e., its reflection in such a graded planar medium.

  15. Biexciton induced refractive index changes in a semiconductor quantum dot

    NASA Astrophysics Data System (ADS)

    Shojaei, S.

    2015-06-01

    We present a detailed theoretical study of linear and third order nonlinear refractive index changes in a optically driven disk-like GaN quantum dot. In our numerical calculations, we consider the three level system containing biexciton, exciton, and ground states and use the compact density matrix formalism and iterative method to obtain refractive index changes. Variational method through effective mass approximation are employed to calculate the ground state energy of biexciton and exciton states. The evolution of refractive index changes around one, two and three photon resonance is investigated and discussed for different quantum dot sizes and light intensities. Size-dependent three-photon nonlinear refractive index change versus incident photon energy compared to that of two-photon is obtained and analyzed. As main result, we found that around resonance frequency at exciton-biexciton transition the quantum confinement has great influence on the linear change in refractive index so that for very large quantum dots, it decreases. Moreover, it was found that third order refractive index changes for three photon process is strongly dependent on QD size and light intensity. Our study reveals that considering our simple model leads to results which are in good agreement with other rare numerical results. Comparison with experimental results has been done.

  16. Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

    NASA Astrophysics Data System (ADS)

    Hermannsson, Ptur G.; Vannahme, Christoph; Smith, Cameron L. C.; Srensen, Kristian T.; Kristensen, Anders

    2015-08-01

    Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown that by covering the array with a sample liquid and measuring the resonance wavelength associated with transverse electric polarized quasi guided modes as a function of period, the refractive index dispersion of the liquid can be accurately obtained using an analytical expression. This method is compact, can perform measurements at arbitrary number of wavelengths, and requires only a minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications.

  17. Interferometric measurement of the refractive-index distribution in plastic lenses by use of computed tomography

    NASA Astrophysics Data System (ADS)

    Suhara, Hiroyuki

    2002-09-01

    A nondestructive measurement method that makes possible the measurement of a three-dimensional refractive-index distribution of any shape plastic lens is presented. In this method, a Mach-Zehnder interferometer and shearing interferometer are combined into a single optical system and are used selectively. Interference fringes of a test object that is immersed in matching liquid are detected at various rotation angles. And transmitted wave fronts are calculated with these interference fringes. Finally, the refractive-index distribution is obtained by computed tomography analysis. In addition, accurate control of the matching liquid temperature makes it possible to measure the absolute refractive index of the test object. This system has good performance with a measurement accuracy of 10-4 or better peak to valley.

  18. Three-dimensional optical metamaterial with a negative refractive index.

    PubMed

    Valentine, Jason; Zhang, Shuang; Zentgraf, Thomas; Ulin-Avila, Erick; Genov, Dentcho A; Bartal, Guy; Zhang, Xiang

    2008-09-18

    Metamaterials are artificially engineered structures that have properties, such as a negative refractive index, not attainable with naturally occurring materials. Negative-index metamaterials (NIMs) were first demonstrated for microwave frequencies, but it has been challenging to design NIMs for optical frequencies and they have so far been limited to optically thin samples because of significant fabrication challenges and strong energy dissipation in metals. Such thin structures are analogous to a monolayer of atoms, making it difficult to assign bulk properties such as the index of refraction. Negative refraction of surface plasmons was recently demonstrated but was confined to a two-dimensional waveguide. Three-dimensional (3D) optical metamaterials have come into focus recently, including the realization of negative refraction by using layered semiconductor metamaterials and a 3D magnetic metamaterial in the infrared frequencies; however, neither of these had a negative index of refraction. Here we report a 3D optical metamaterial having negative refractive index with a very high figure of merit of 3.5 (that is, low loss). This metamaterial is made of cascaded 'fishnet' structures, with a negative index existing over a broad spectral range. Moreover, it can readily be probed from free space, making it functional for optical devices. We construct a prism made of this optical NIM to demonstrate negative refractive index at optical frequencies, resulting unambiguously from the negative phase evolution of the wave propagating inside the metamaterial. Bulk optical metamaterials open up prospects for studies of 3D optical effects and applications associated with NIMs and zero-index materials such as reversed Doppler effect, superlenses, optical tunnelling devices, compact resonators and highly directional sources. PMID:18690249

  19. Water absorption in a refractive index model for bacterial spores

    NASA Astrophysics Data System (ADS)

    Siegrist, K. M.; Thrush, E.; Airola, M.; Carr, A. K.; Limsui, D. M.; Boggs, N. T.; Thomas, M. E.; Carter, C. C.

    2009-05-01

    The complexity of biological agents can make it difficult to identify the important factors impacting scattering characteristics among variables such as size, shape, internal structure and biochemical composition, particle aggregation, and sample additives. This difficulty is exacerbated by the environmentally interactive nature of biological organisms. In particular, bacterial spores equilibrate with environmental humidity by absorption/desorption of water which can affect both the complex refractive index and the size/shape distributions of particles - two factors upon which scattering characteristics depend critically. Therefore accurate analysis of experimental data for determination of refractive index must take account of particle water content. First, spectral transmission measurements to determine visible refractive index done on suspensions of bacterial spores must account for water (or other solvent) uptake. Second, realistic calculations of aerosol scattering cross sections should consider effects of atmospheric humidity on particle water content, size and shape. In this work we demonstrate a method for determining refractive index of bacterial spores bacillus atropheus (BG), bacillus thuringiensis (BT) and bacillus anthracis Sterne (BAs) which accounts for these effects. Visible index is found from transmission measurements on aqueous and DMSO suspensions of particles, using an anomalous diffraction approximation. A simplified version of the anomalous diffraction theory is used to eliminate the need for knowledge of particle size. Results using this approach indicate the technique can be useful in determining the visible refractive index of particles when size and shape distributions are not well known but fall within the region of validity of anomalous dispersion theory.

  20. Aberration-free negative-refractive-index lens

    NASA Astrophysics Data System (ADS)

    Chen, Jiajun; Radu, Cosmin; Puri, Ashok

    2006-02-01

    The aberrations of a spherical lens composed of left-handed materials are studied in this letter. Five Seidel aberrations (spherical, coma, astigmatism, field curvature, and distortion) as a function of the refractive index n and shape factor q of the lens are considered. Our numerical calculations show that the negative refractive index gives much larger windows of small values of aberrations than the positive index, which will significantly enhance the flexibility for the design of an optical lens. Two possible regions with optimized aberrations are proposed: n =-1, q =-2.2 and n =-0.81 and q =0.83.

  1. Integrated Microfibre Device for Refractive Index and Temperature Sensing

    PubMed Central

    Lim, Kok-Sing; Aryanfar, Iman; Chong, Wu-Yi; Cheong, Yew-Ken; Harun, Sulaiman W.; Ahmad, Harith

    2012-01-01

    A microfibre device integrating a microfibre knot resonator in a Sagnac loop reflector is proposed for refractive index and temperature sensing. The reflective configuration of this optical structure offers the advantages of simple fabrication and ease of sensing. To achieve a balance between responsiveness and robustness, the entire microfibre structure is embedded in low index Teflon, except for the 0.52 mm diameter microfibre knot resonator sensing region. The proposed sensor has exhibited a linear spectral response with temperature and refractive index. A small change in free spectral range is observed when the microfibre device experiences a large refractive index change in the surrounding medium. The change is found to be in agreement with calculated results based on dispersion relationships.

  2. Refractive index measurement in human tissue samples

    NASA Astrophysics Data System (ADS)

    Tsenova, Vesselina; Stoykova, Elena V.

    2003-11-01

    The aim of this study was to apply a laser refractometer based on a total internal reflection for measurement of refractive indices of thin tissue samples. The tissue slices with thickness from 5 to 15 ?m and cross-sectional area of about 1 - 1.5 cm were cut with a freezing microtome and mounted on microscope glass slides. The samples from a liver, kidney, myocardium and skin were taken post mortem from 3 male patients (50, 52 and 75 years old) with some pathological tissue changes as well as from 3 dead fetuses 24-48 hours after the death. To indicate the morphological changes, the samples were stained with hemolown-eosin (HE) and studied microscopically. Using a two-beam UV-Vis-NIR-spectrophotometer Cary-5E (Variant), on-axis transmittance of the samples was measured over the 350 - 2000 nm range and the spectra of the extinction coefficient, in cm-1, were calculated. The measured refractive indices correspond to dehydrated tissue samples.

  3. On the anodic aluminium oxide refractive index of nanoporous templates

    NASA Astrophysics Data System (ADS)

    Hierro-Rodriguez, A.; Rocha-Rodrigues, P.; Valds-Bango, F.; Alameda, J. M.; Jorge, P. A. S.; Santos, J. L.; Araujo, J. P.; Teixeira, J. M.; Guerreiro, A.

    2015-11-01

    In the present study, we have determined the intrinsic refractive index of anodic aluminium oxide, which is originated by the formation of nanoporous alumina templates. Different templates have been fabricated by the conventional two-step anodization procedure in oxalic acid. Their porosities were modified by chemical wet etching allowing the tuning of their effective refractive indexes (air-filled nanopores??+??anodic aluminium oxide). By standard spectroscopic light transmission measurements, the effective refractive index for each different template was extracted in the VIS-NIR region. The determination of the intrinsic anodic aluminium oxide refractive index was performed by using the Maxwell-Garnett homogenization theory. The results are coincident for all the fabricated samples. The obtained refractive index (~1.55) is quite lower (~22%) than the commonly used Al2O3 handbook value (~1.75), showing that the amorphous nature of the anodic oxide structure strongly conditions its optical properties. This difference is critical for the correct design and modeling of optical plasmonic metamaterials based on anodic aluminium oxide nanoporous templates.

  4. Refractive index dependence of Papilio Ulysses butterfly wings reflectance spectra

    NASA Astrophysics Data System (ADS)

    Isnaeni, Muslimin, Ahmad Novi; Birowosuto, Muhammad Danang

    2016-02-01

    We have observed and utilized butterfly wings of Papilio Ulysses for refractive index sensor. We noticed this butterfly wings have photonic crystal structure, which causes blue color appearance on the wings. The photonic crystal structure, which consists of cuticle and air void, is approximated as one dimensional photonic crystal structure. This photonic crystal structure opens potential to several optical devices application, such as refractive index sensor. We have utilized small piece of Papilio Ulysses butterfly wings to characterize refractive index of several liquid base on reflectance spectrum of butterfly wings in the presence of sample liquid. For comparison, we simulated reflectance spectrum of one dimensional photonic crystal structure having material parameter based on real structure of butterfly wings. We found that reflectance spectrum peaks shifted as refractive index of sample changes. Although there is a slight difference in reflectance spectrum peaks between measured spectrum and calculated spectrum, the trend of reflectance spectrum peaks as function of sample's refractive index is the similar. We assume that during the measurement, the air void that filled by sample liquid is expanded due to liquid pressure. This change of void shape causes non-similarity between measured spectrum and calculated spectrum.

  5. Two-dimensional scanning focused refractive-index microscopy and applications to refractive-index profiling of optical fibers

    NASA Astrophysics Data System (ADS)

    Wang, Xiaowan; Ye, Qing; Sun, Tengqian; Wang, Jin; Deng, Zhichao; Mei, Jianchun; Zhou, Wenyuan; Zhang, Chunping; Tian, Jianguo

    2015-01-01

    The refractive-index profile (RIP) of optical fibers is of fundamental significance in determining critical fiber properties. Here, we present the application of a two-dimensional (2-D) scanning focused refractive-index microscopy (SFRIM) to accurately obtain the 2-D RIP of a graded-index optical fiber. Some modifications are made to SFRIM for better 2-D measurement. Quantitative RIP of the fiber is obtained with derivative total reflection method. The refractive-index accuracy is 0.002. The measured result is in good agreement with theoretical expectation. This method is straightforward, simple, repeatable, and free from signal distortion. This technique is suitable for symmetric and asymmetric optical fibers. The results indicate that this technique can be applied to obtain the RIPs of a wide range of materials and has broad application prospect in many fields.

  6. Plasmonic metamaterials for ultrasensitive refractive index sensing at near infrared

    NASA Astrophysics Data System (ADS)

    Gu, Yang; Li, Qiuze; Xiao, Jie; Wu, Kedi; Wang, Guo Ping

    2011-01-01

    We experimentally report a kind of plasmonic metamaterials for high sensitive refractive index sensing. The metamaterials are an X-shaped metal nanohole array fabricated by holographic lithography followed by electron-beam evaporation and lift-off procedure. Transmission spectrum measurements reveal that the localized surface plasmon resonance (LSPR) wavelength of such nanohole array shows ultrasensitive response to refractive index change in the surrounding medium. A sensitivity of 1398 nm per refractive index unit is achieved at near infrared. The high sensitivity is attributed to the well confined and greatly enhanced electric field created by LSPR as well as the increased spatial overlap between the localized electric field and the surrounding medium. The robust fabrication technique and high sensitivity provide the present plasmonic metamaterials great potentials for the development of chip-based high sensitive nanooptical biomedicine sensors and integrated devices.

  7. Exposed core microstructured optical fiber Bragg gratings: refractive index sensing.

    PubMed

    Warren-Smith, Stephen C; Monro, Tanya M

    2014-01-27

    Bragg gratings have been written in exposed-core microstructured optical fibers for the first time using a femtosecond laser. Second and third order gratings have been written and both show strong reflectivity at 1550 nm, with bandwidths as narrow as 60 pm. Due to the penetration of the guided field outside the fiber the Bragg reflections are sensitive to the external refractive index. As different modes have different sensitivities to refractive index but the same temperature sensitivity the sensor can provide temperature-compensated refractive index measurements. Since these Bragg gratings have been formed by physical ablation, these devices can also be used for high temperature sensing, demonstrated here up to 800C. The fibers have been spliced to single mode fiber for improved handling and integration with commercial interrogation units. PMID:24515155

  8. Evidence of Negative-Index Refraction in Nonlinear Chemical Waves

    NASA Astrophysics Data System (ADS)

    Yuan, Xujin; Wang, Hongli; Ouyang, Qi

    2011-05-01

    The negative index of refraction of nonlinear chemical waves has become a recent focus in nonlinear dynamics researches. Theoretical analysis and computer simulations have predicted that the negative index of refraction can occur on the interface between antiwaves and normal waves in a reaction-diffusion (RD) system. However, no experimental evidence has been found so far. In this Letter, we report our experimental design in searching for such a phenomenon in a chlorite-iodide-malonic acid (CIMA) reaction. Our experimental results demonstrate that competition between waves and antiwaves at their interface determines the fate of the wave interaction. The negative index of refraction was only observed when the oscillation frequency of a normal wave is significantly smaller than that of the antiwave. All experimental results were supported by simulations using the Lengyel-Epstein RD model which describes the CIMA reaction-diffusion system.

  9. Empirical modelling to predict the refractive index of human blood.

    PubMed

    Yahya, M; Saghir, M Z

    2016-02-21

    Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient's condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy. PMID:26807785

  10. Empirical modelling to predict the refractive index of human blood

    NASA Astrophysics Data System (ADS)

    Yahya, M.; Saghir, M. Z.

    2016-02-01

    Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient’s condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy.

  11. Dual interferometer system for measuring index of refraction

    NASA Astrophysics Data System (ADS)

    Goodwin, Eric Peter

    The optical power of a lens is determined by the surface curvature and the refractive index, n. Knowledge of the index is required for accurate lens design models and for examining material variations from sample to sample. The refractive index of glass can be accurately measured using a prism spectrometer, but measuring the index of soft contact lens materials presents many challenges. These materials are non-rigid, thin, and must remain hydrated in a saline solution during testing. Clearly an alternative to a prism spectrometer must be used to accurately measure index. A Dual Interferometer System has been designed, built and characterized as a novel method for measuring the refractive index of transparent optical materials, including soft contact lens materials. The first interferometer is a Low Coherence Interferometer in a Twyman-Green configuration with a scanning reference mirror. The contact lens material sample is placed in a measurement cuvette, where it remains hydrated. By measuring the locations of the multiple optical interfaces, the physical thickness t of the material is measured. A new algorithm has been developed for processing the low coherence signals obtained from the reflection at each optical interface. The second interferometer is a Mach-Zehnder interferometer with a tunable HeNe laser light source. This interferometer measures the optical path length (OPL) of the test sample in the cuvette in transmission as a function of five wavelengths in the visible spectrum. This is done using phase-shifting interferometry. Multiple thickness regions are used to solve 2pi phase ambiguities in the OPL. The outputs of the two interferometers are combined to determine the refractive index as a function of wavelength: n(lambda) = OPL(lambda)/t. Since both t and OPL are measured using a detector array, n is measured at hundreds of thousands of data points. A measurement accuracy of 0.0001 in refractive index is achieved with this new instrument, which is verified using custom glass calibration samples.

  12. Integrated photonic structures for parallel fluorescence and refractive index biosensing

    NASA Astrophysics Data System (ADS)

    Lee, Meredith M.; O'Sullivan, Thomas D.; Cerruto, Antonio; Liu, Victor; Zhang, Jingyu; Levi, Ofer; Lee, Heon; Brueck, Steven R. J.; Fan, Shanhui; Harris, James S.

    2011-05-01

    We present a multi-modality optical sensing platform employing integrated Vertical Cavity Surface Emitting Lasers (VCSELs), photodetectors, and filters suitable for portable, real-time analyte detection in aqueous environments. Fluorescence and refractive index sensors designed to utilize visible and near-infrared VCSELs for low background absorption from analyte delivery fluids are described. We demonstrate in vitro fluorescence sensing of Cy5.5 dye with a detection sensitivity of 5 nM and photonic crystal slab refractive index sensing with tunable GaAs-based 670 nm VCSELs. This compact, parallel sensor architecture enables multiplexed, cost-effective on-chip biosensing.

  13. Development of High Refractive Index Conjugated Materials

    NASA Astrophysics Data System (ADS)

    Graham, Matthew; Jin, Shi; Cheng, Stephen Z. D.

    2007-03-01

    The goal of this project is to fabricate a polymeric material with a complete 3-D PBG, to bring the tailorable physical, electrical, and optical properties of polymeric materials to 3-D PBG materials. Because of its conjugated nature and the presence of a heavy sulfur atom in its repeat unit, poly(thiophene) (PT) is predicted to have one of the highest polymeric refractive indices, but the reported n values for PT are 1.4 at 633 nm. This discrepancy is because the potential needed to electrosynthesize PT, the only method available to synthesize thick and high quality PT films, is higher than its degradation potential. It was found that by polymerizing thiophene with an optimized monomer concentration, proton trap concentration, and reaction temperature in a strong aprotic Lewis acid solvent, the polymerization potential could be reduced below the degradation potential of PT. The resultant PT film had a significantly elevated n Photonic templates were then constructed using a combination of Colvin's method^ with monodisperse spheres and mechanical annealing. High n PT was used to infiltrate the templates, and the templates were removed leaving a polymeric inverse opal with the possibility of a complete 3-D PBG.

  14. Slow-light enhanced subwavelength plasmonic waveguide refractive index sensors.

    PubMed

    Huang, Yin; Min, Changjun; Dastmalchi, Pouya; Veronis, Georgios

    2015-06-01

    We introduce slow-light enhanced subwavelength scale refractive index sensors which consist of a plasmonic metal-dielectric-metal (MDM) waveguide based slow-light system sandwiched between two conventional MDM waveguides. We first consider a MDM waveguide with small width structrue for comparison, and then consider two MDM waveguide based slow light systems: a MDM waveguide side-coupled to arrays of stub resonators system and a MDM waveguide side-coupled to arrays of double-stub resonators system. We find that, as the group velocity decreases, the sensitivity of the effective index of the waveguide mode to variations of the refractive index of the fluid filling the sensors as well as the sensitivities of the reflection and transmission coefficients of the waveguide mode increase. The sensing characteristics of the slow-light waveguide based sensor structures are systematically analyzed. We show that the slow-light enhanced sensors lead to not only 3.9 and 3.5 times enhancements in the refractive index sensitivity, and therefore in the minimum detectable refractive index change, but also to 2 and 3 times reductions in the required sensing length, respectively, compared to a sensor using a MDM waveguide with small width structure. PMID:26072849

  15. Superluminal light attenuated by strong dispersion of complex refractive index

    NASA Astrophysics Data System (ADS)

    Abdurahman, Ahmed Yonis; Vadim Nickolaevich, Malnev; Belayneh Mesfin, Ali

    2016-02-01

    The propagation of narrow packets of electromagnetic waves (EMWs) in frequency dispersive medium with the consideration of the complex refractive index is studied. It is shown that counting in the dispersion of the complex refractive index within the context of the conventional expression of the group velocity of narrow wave packets of EMWs propagating in a dispersive medium results in the appearance of additional constraints on the group velocity, which dictates that the physically acceptable group velocity can only be realized in the case of a negligible imaginary part of the group index. In this paper, the conditions that allow one to realize the physically acceptable group velocity are formulated and analyzed numerically for the relevant model of the refractive index of a system of two-level atoms in the optical frequency range. It is shown that in the frequency band where superluminal light propagation is expected, there is a strong dispersion of the refractive index that is accompanied with strong absorption, resulting in a strongly attenuated superluminal light.

  16. Non-Contact Measurements Of Refractive Index And Surface Curvature

    NASA Astrophysics Data System (ADS)

    O'Shea, Donald C.; Tilstra, Shawn A.

    1989-01-01

    A simple system geometry using a low power laser has been designed to measure the surface curvature of a lens or a mirror or the refractive index of a slab of a transparent material by using the Fresnel reflection from its surfaces. By comparing our measurements of the surface curvature to those using a precision spherometer, we found this method accurate to ±0.1 mm for curvatures from 25 to 75 mm. If the thickness of a parallel plate can be measured, this technique can determine the refractive index of the plate without resorting to demounting or cutting a sample to be measured. Measurements of fused and crystalline quartz flats determined the refractive indices of the samples to ±0.001. The application of this technique to in situ measurements of optical systems and its limitations will be discussed.

  17. Absolute refractive indices and thermal coefficients of CaF2, SrF2, BaF2, and LiF near 157 nm.

    PubMed

    Burnett, John H; Gupta, Rajeev; Griesmann, Ulf

    2002-05-01

    We present high-accuracy measurements for wavelengths near 157 nm of the absolute index of refraction, the index dispersion, and the temperature dependence of the index for the ultraviolet optical materials with cubic symmetry: CaF2, SrF2, BaF2, and LiF. Accurate values of these quantities for these materials are needed for designs of the lens systems for F2 excimer-laser-based exposure tools for 157-nm photolithography. These tools are expected to use CaF2 as the primary optical material and possibly one of the others to correct for chromatic aberrations. These optical properties were measured by the minimum deviation method. Absolute refractive indices were obtained with an absolute accuracy of 5 x 10(-6) to 6 x 10(-6). PMID:12009162

  18. Temperature-dependent refractive index of Cleartran ZnS to cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Leviton, Douglas B.; Frey, Bradley J.

    2013-09-01

    Cleartran ZnS is a water clear form of CVD ZnS and a popular material for infrared optical designs. In order to enable the highest quality lens designs with this material at cryogenic temperatures, we have measured the absolute refractive indices of two prisms as a function of both wavelength and temperature using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center (GSFC). While conventional CVD ZnS has received considerable study at cryogenic temperatures, to our knowledge, cryogenic indices of Cleartran have not been measured by other investigators. For our measurements of Cleartran, we report absolute refractive index, spectral dispersion (dn/d?), and spectral thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 0.50 to 5.6 ?m. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate computation of index at any applicable wavelength and temperature. We compare our measured indices with those of the material's manufacturer, Rohm & Haas, at room temperature where we find good agreement to within our measurement uncertainty, and we compare our refractive indices and their aforementioned derivatives to cryogenic temperatures with those for conventional ZnS from the literature

  19. Unidirectional transmission using array of zero-refractive-index metamaterials

    SciTech Connect

    Fu, Yangyang; Xu, Lin; Hong Hang, Zhi; Chen, Huanyang

    2014-05-12

    In this Letter, we find that high efficient unidirectional transmission occurs for an array of prisms made of zero-refractive-index metamaterials. As a specific demonstration, we further design the device using Dirac-cone-like photonic crystals. The device can function for a broadband of spectrum. Numerical simulations are performed to verify the one-way wave functionality.

  20. Refractive index of air for interferometric length measurements

    NASA Astrophysics Data System (ADS)

    Abou-Zeid, A.

    2015-02-01

    The refractive index of air can be directly measured by a refractometer or can be calculated by using updated Edln's formulas by measuring the parameters of the surrounding air or by using the modified two-colour method. In this paper an overview on the three methods is given by taking into account for their features, uncertainties and application fields.

  1. Refractive index determination in axially symmetric oprtically inhomogeneous media

    NASA Astrophysics Data System (ADS)

    Ionescu-Pallas, Nicholas; Vlad, Valentin I.; Bociort, Florian

    The focussing method from transversally light, put forward by Dietrich Marcuse in view of determining the refractive index profile (RIP) in optical fibers and fiber performs, is revised. A more rigorous derivation of the Marcuse formula is given, establishing the conditions of its validity and a simplified version is initially proposed, able to avoid the systematic errors in the processing of light intensity data.

  2. Index of Refraction Profile in a Highway Mirage

    NASA Astrophysics Data System (ADS)

    Nelsen, Bryan; Lobue, James; Edwards, Mark

    2003-11-01

    We have determined the index of refraction of air above the highway on a hot summer's day by measuring the path of a laser beam traveling opposite the path of a mirage ray. A device consisting of a doubled-YAG laser pointer mounted on a tripod on top of a pair of binoculars was used to aim the laser beam into a highway mirage. The path of this ray was measured by obtaining the coordinates of the laser spot at various points along the ray. We used the measured path to determine the index of refraction of the air above the road according to Fermat's Princple of Least Time. We have also developed a model for predicting this index of refraction by assuming that thin horizontal slabs of air act as ideal gases and that the heat conduction law is obeyed. We present a comparison of the measured index of refraction with the predictions of the model. We find that the model gives good agreement with the data.

  3. Giant Kerr nonlinearities using refractive-index enhancement

    SciTech Connect

    Yavuz, D. D.; Sikes, D. E.

    2010-03-15

    By utilizing refractive-index enhancement with vanishing absorption, a scheme is suggested that achieves giant Kerr nonlinearities between two weak laser beams. One application of this scheme is discussed and an all-optical distributed Bragg reflector is proposed that works at very low light levels.

  4. Structures with negative index of refraction

    DOEpatents

    Soukoulis, Costas M. (Ames, IA); Zhou, Jiangfeng (Ames, IA); Koschny, Thomas (Ames, IA); Zhang, Lei (Ames, IA); Tuttle, Gary (Ames, IA)

    2011-11-08

    The invention provides simplified negative index materials (NIMs) using wire-pair structures, 4-gap single ring split-ring resonator (SRR), fishnet structures and overleaf capacitor SRR. In the wire-pair arrangement, a pair of short parallel wires and continuous wires are used. In the 4-gap single-ring SRR, the SRRs are centered on the faces of a cubic unit cell combined with a continuous wire type resonator. Combining both elements creates a frequency band where the metamaterial is transparent with simultaneously negative .di-elect cons. and .mu.. In the fishnet structure, a metallic mesh on both sides of the dielectric spacer is used. The overleaf capacitor SRR changes the gap capacities to small plate capacitors by making the sections of the SRR ring overlap at the gaps separated by a thin dielectric film. This technique is applicable to conventional SRR gaps but it best deploys for the 4-gap single-ring structures.

  5. Cryogenic Temperature-Dependent Refractive Index Measurements of CaF2 and Infrasil 301

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.; Madison, TImothy J.

    2007-01-01

    In order to enable high quality lens design using calcium fluoride (CaF2) and Heraeus Infrasil 30 (Infrasil) at cryogenic temperatures, we have measured the absolute refractive index of prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For CaF2, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 25 to 300 K at wavelengths from 0.4 to 5.6 micrometers; for Infrasil we cover temperatures ranging from 35 to 300K and wavelengths from 0.4 to 3.6 micrometers. We investigate the interspecimen variability between measurements of two unrelated samples of CaF2, and we also compare our results for Infrasil to previous measurements fo Corning 7980 fused silica. Finally, we provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures and compare those results to other data found in the literature.

  6. Gain in negative-refractive-index slow-light waveguides

    NASA Astrophysics Data System (ADS)

    Hess, Ortwin; Tsakmakidis, Kosmas L.; Kirby, Edmund I.; Pickering, Tim; Hamm, Joachim M.

    2011-03-01

    We outline the theory of slow-light propagation in waveguides featuring negative electromagnetic parameters (permittivity, permeability and/or refractive index). We explain the mechanism by which these heterostructures can enable stopping of light even in the presence of disorder and, simultaneously, dissipative losses. Using full-wave numerical simulations and analytical transfer-matrix calculations we show that the incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index waveguide can completely remove dissipative losses - in a slow- or stopped-light regime where the effective index of the guided lightwave remains negative. We also review and compare several 'trapped rainbow' schemes that have recently been proposed for slowing and stopping waves.

  7. INDEX OF REFRACTION OF SHOCK LOADED SODA-LIME GLASS

    SciTech Connect

    Alexander, C. S.

    2009-12-28

    Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to 2430 GPa) where the material remains transparent. In order for SLG to be practical as a VISAR window, the correction factor, which describes the frequency correction related to the strain dependence of the refractive index, and hence the index of refraction itself, must be characterized as a function of pressure. Characterization data are reported in this paper and compared to previous results. The present data show good agreement with those of Dandekar [J. Appl. Phys. 84, 6614 (1998)] and separate study results by Gibbons and Ahrens [J. Geophys. Res. 76, 5489 (1971)] up to 7 GPa. However, at stresses over 7 GPa, marked discrepancies are evident between the present data and that of Gibbons and Ahrens. Differences in test methods may explain these discrepancies.

  8. Perfect conformal invisible device with feasible refractive indexes

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Chen, Huanyang; Tyc, Tomáš; Xie, Yangbo; Cummer, Steven A.

    2016-01-01

    Optical conformal mapping has been used to construct several isotropic devices with novel functionalities. In particular, a conformal cloak could confer omnidirectional invisibility. However, the maximum values of the refractive indexes needed for current designs are too large to implement, even in microwave experiments. Furthermore, most devices designed so far have had imperfect impedance matching and therefore incomplete invisibility functionalities. Here we describe a perfect conformal invisible device with full impedance matching everywhere. The maximum value of refractive index required by our device is just about five, which is feasible for microwave and terahertz experiments using current metamaterial techniques. To construct the device, we use a logarithmic conformal mapping and a Mikaelian lens. Our results should enable a conformal invisible device with almost perfect invisibility to be made soon.

  9. Complex refractive index of Martian dust - Mariner 9 ultraviolet observations

    NASA Technical Reports Server (NTRS)

    Pang, K.; Ajello, J. M.; Hord, C. W.; Egan, W. G.

    1976-01-01

    Mariner 9 ultraviolet spectrometer observations of the 1971 dust clouds obscuring the surface of Mars have been analyzed by matching the observed dust phase function with Mie scattering calculations for size distributions of homogeneous and isotropic material. Preliminary results indicate an effective particle radius of not less than 0.2. The real component of the index of refraction is not less than 1.8 at both 268 and 305 nm; corresponding values for the imagery component are 0.02 and 0.01. These values are consistent with those found by Mead (1970) for the visible and near-visible wavelengths. The refractive index and the absorption coefficient increase rapidly with decreasing wavelength in going from the visible to the ultraviolet, indicating the presence of an ultraviolet absorption band which may shield organisms from ultraviolet irradiation.

  10. Refractive index compensation in over-determined interferometric systems.

    PubMed

    Lazar, Josef; Holá, Miroslava; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Buchta, Zdeněk

    2012-01-01

    We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup. PMID:23202037

  11. Refractive Index Compensation in Over-Determined Interferometric Systems

    PubMed Central

    Lazar, Josef; Holá, Miroslava; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Buchta, Zdeněk

    2012-01-01

    We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup. PMID:23202037

  12. Ultrafast refractive index control of a terahertz graphene metamaterial

    PubMed Central

    Lee, Seung Hoon; Choi, Jeongmook; Kim, Hyeon-Don; Choi, Hyunyong; Min, Bumki

    2013-01-01

    Modulation of the refractive index of materials is elementary, yet it is crucial for the manipulation of electromagnetic waves. Relying on the inherent properties of natural materials, it has been a long-standing challenge in device engineering to increase the index-modulation contrast. Here, we demonstrate a significant amount of ultrafast index modulation by optically exciting non-equilibrium Dirac fermions in the graphene layer integrated onto a high-index metamaterial. Furthermore, an extremely-large electrical modulation of refractive index up to ?n ~ ?3.4 (at 0.69?THz) is achieved by electrical tuning of the density of the equilibrium Dirac fermion in the graphene metamaterial. This manifestation, otherwise remaining elusive in conventional semiconductor devices, fully exploits the characteristic ultrafast charge relaxation in graphene as well as the strong capacitive response of the metamaterial, both of which enable us to drastically increase the light-matter interaction of graphene and the corresponding index contrast in the graphene metamaterials. PMID:23823715

  13. Fiber Optic-Based Refractive Index Sensing at INESC Porto

    PubMed Central

    Jorge, Pedro A. S.; Silva, Susana O.; Gouveia, Carlos; Tafulo, Paula; Coelho, Luis; Caldas, Paulo; Viegas, Diana; Rego, Gaspar; Baptista, Jos M.; Santos, Jos L.; Frazo, Orlando

    2012-01-01

    A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied include those based on Bragg and long period gratings, on micro-interferometers, on plasmonic effects in fibers and on multimode interference in a large spectrum of standard and microstructured optical fibers. PMID:22969405

  14. Enhanced refractive index without absorption in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Chen, Nan; Shui, Tao; Qian, Biqi; Wang, Zhiping; Yu, Benli

    2015-07-01

    We investigate the absorptive-dispersive properties of a weak probe field in a ladder-type quantum dot. It is found that the enhanced refraction index without absorption can be easily controlled via adjusting properly the corresponding parameters of the system. Our scheme may provide some new possibilities for technological applications in dispersion compensation and solid-state quantum communication for quantum information processing.

  15. A new iterative algorithm to reconstruct the refractive index.

    PubMed

    Liu, Y J; Zhu, P P; Chen, B; Wang, J Y; Yuan, Q X; Huang, W X; Shu, H; Li, E R; Liu, X S; Zhang, K; Ming, H; Wu, Z Y

    2007-06-21

    The latest developments in x-ray imaging are associated with techniques based on the phase contrast. However, the image reconstruction procedures demand significant improvements of the traditional methods, and/or new algorithms have to be introduced to take advantage of the high contrast and sensitivity of the new experimental techniques. In this letter, an improved iterative reconstruction algorithm based on the maximum likelihood expectation maximization technique is presented and discussed in order to reconstruct the distribution of the refractive index from data collected by an analyzer-based imaging setup. The technique considered probes the partial derivative of the refractive index with respect to an axis lying in the meridional plane and perpendicular to the propagation direction. Computer simulations confirm the reliability of the proposed algorithm. In addition, the comparison between an analytical reconstruction algorithm and the iterative method has been also discussed together with the convergent characteristic of this latter algorithm. Finally, we will show how the proposed algorithm may be applied to reconstruct the distribution of the refractive index of an epoxy cylinder containing small air bubbles of about 300 micro of diameter. PMID:17664544

  16. Microvolume index of refraction determinations by interferometric backscatter

    NASA Astrophysics Data System (ADS)

    Bornhop, Darryl J.

    1995-06-01

    A new method has been applied to the determination of fluid bulk properties in small detection volumes. Through the use of an unfocused He-Ne laser beam and a cylindrical tube of capillary dimensions, relative refractive-index measurements are possible. The backscattered light from the illumination of a tube of capillary dimensions produces an interference pattern that is spatially defined and that contains information related to the bulk properties of the fluid contained in the tube. Positional changes in the intensity-modulated beam profile (interference fringes) are directly related to the refractive index of the fluid in the tube. The determination of dn/n at the 10-7 level is possible in probe volumes of 350 pL. The technique has been applied to tubes as small as 75 mu m inner diameter and as large as 1.0 mm inner diameter. No modification of the simple optical bench is required for facilitating the determination of refractive index for the complete range of tube diameters.

  17. Determining index of refraction from polarimetric hyperspectral radiance measurements

    NASA Astrophysics Data System (ADS)

    Martin, Jacob A.; Gross, Kevin C.

    2015-09-01

    Polarimetric hyperspectral imaging (P-HSI) combines two of the most common remote sensing modalities. This work leverages the combination of these techniques to improve material classification. Classifying and identifying materials requires parameters which are invariant to changing viewing conditions, and most often a material's reflectivity or emissivity is used. Measuring these most often requires assumptions be made about the material and atmospheric conditions. Combining both polarimetric and hyperspectral imaging, we propose a method to remotely estimate the index of refraction of a material. In general, this is an underdetermined problem because both the real and imaginary components of index of refraction are unknown at every spectral point. By modeling the spectral variation of the index of refraction using a few parameters, however, the problem can be made overdetermined. A number of different functions can be used to describe this spectral variation, and some are discussed here. Reducing the number of spectral parameters to fit allows us to add parameters which estimate atmospheric downwelling radiance and transmittance. Additionally, the object temperature is added as a fit parameter. The set of these parameters that best replicate the measured data is then found using a bounded Nelder-Mead simplex search algorithm. Other search algorithms are also examined and discussed. Results show that this technique has promise but also some limitations, which are the subject of ongoing work.

  18. Refractive index and extinction coefficient of Si at 400 nm between 10 and 300 K

    NASA Astrophysics Data System (ADS)

    Nagakubo, Akira; Ogi, Hirotsugu; Hirao, Masahiko

    2015-12-01

    Optical properties of Si are important and widely studied. However, temperature dependence of the refractive index for visible light at low temperatures has not been measured. In this study, we measured the complex refractive index of Si at 400 nm between 10 and 300 K by picosecond ultrasound spectroscopy. The measured refractive index at room temperature agrees well with reported values, confirming the accuracy of our measurement, and we found that the refractive index at 10 K is smaller than reported values.

  19. Refractive index of glass and its dipersion for visible light.

    SciTech Connect

    Smith, D. Y.; Karstens, W.

    2010-01-01

    The classification of optical glass and empirical relations between the refractive index and its dispersion are discussed in terms of moments of the glass's IR and UV absorption spectra. The observed linear dependence of index on dispersion within glass families is shown to arise primarily from the approximately linear superposition of the electronic absorptions of glass former and glass modifiers. The binary classification into crown and flint glasses is also based primarily on electronic spectra: Crown glasses are 'wide-gap' materials with excitation energies greater than {approx}12.4 eV, while flint glasses are their 'narrow-gap' counterpart.

  20. Polymeric nanolayered gradient refractive index lenses: technology review and introduction of spherical gradient refractive index ball lenses

    NASA Astrophysics Data System (ADS)

    Ji, Shanzuo; Yin, Kezhen; Mackey, Matthew; Brister, Aaron; Ponting, Michael; Baer, Eric

    2013-11-01

    A nanolayered polymer films approach to designing and fabricating gradient refractive index (GRIN) lenses with designer refractive index distribution profiles and an independently prescribed lens surface geometry have been demonstrated to produce a new class of optics. This approach utilized nanolayered polymer materials, constructed with polymethylmethacrylate and a styrene-co-acrylonitrile copolymer with a tailorable refractive index intermediate to bulk materials, to fabricate discrete GRIN profile materials. A process to fabricate nanolayered polymer GRIN optics from these materials through thermoforming and finishing steps is reviewed. A collection of technology-demonstrating previously reported nanolayered GRIN case studies is presented that include: (1) the optical performance of a f/# 2.25 spherical GRIN plano-convex singlet with one quarter (2) the weight of a similar BK7 lens and a bio-inspired aspheric human eye GRIN lens. Original research on the fabrication and characterization of a Luneburg inspired GRIN ball lens is presented as a developing application of the nanolayered polymer technology.

  1. Extraction of complex refractive index dispersion from SPR data

    NASA Astrophysics Data System (ADS)

    Nakkach, Mohamed; Moreau, Julien; Canva, Michael

    2010-02-01

    Surface Plasmon Resonnance (SPR) techniques have been mostly set-up as angular reflectivity interrogation mode using quasi-monochromatic light or as spectral reflectivity interrogation mode at one given wavelength, providing information about variation of effective optical thickness ?n.e above the metal surface. In this communication we present a dual mode sensor working both in angular and spectral interrogation modes. A white light illuminates the sensor surface and the reflectivity spectra in TE and TM polarization are measured with a spectrometer. By changing the angular coupling conditions, a complete reflectivity surface R(?, ?) can be measured. The 2D reflectivity decrease valley is affected by both the real and imaginary part of the optical index of the dielectric medium as well as their spectral dispersion. With such experimental data set, it is possible to back calculate the dispersion of the complex refractive index of the dielectric layer. This is demonstrated using a turquoise dye doped solution. According to the Kramers-Kronig relations, the imaginary part of the refractive index for an absorbing medium is proportional to the absorption while the real part presents a large dispersion around the absorption wavelength. The reflectivity surface R(?, ?) was measured from 500 nm to 750 nm over about 8 angular range. The whole complex refractive optical index of the doped solution, absorbing around 630 nm, was reconstructed from the SPR reflectivity experimental data, using a homemade program based on an extended Rouard method to fit the experimental angular plasmon data for each wavelength. These results show that the classical SPR technique can be extended to acquire precise spectral information about biomolecular interactions occurring on the metallic layer.

  2. Methods comparison to retrieve the refractive index of small scatterers

    NASA Astrophysics Data System (ADS)

    Snchez, A.-M.; Piera, J.

    2015-11-01

    Simulation tools to generate the inherent optical properties of small scatterers are useful to complement data difficult to measure, as for instance their angular scattering features. However, in most cases, shapes are reduced to homogeneous spheres, which is a gross simplification for any particles in water, and the inner complex refractive index is estimated using some approximations. In this paper, several methods for the retrieval of the refractive indices are used in three different examples modelling different shapes and particle size distributions. The error associated with each method is discussed and analysed. It is finally demonstrated that those inverse methods using a genetic algorithm provide optimal estimations relative to other techniques that, although faster, are less accurate. The obtained results suggest that phytoplankton models can be improved using this kind of algorithms and a suitable shape.

  3. Imaging based refractometer for hyperspectral refractive index detection

    SciTech Connect

    Baba, Justin S.; Boudreaux, Philip R.

    2015-11-24

    Refractometers for simultaneously measuring refractive index of a sample over a range of wavelengths of light include dispersive and focusing optical systems. An optical beam including the range of wavelengths is spectrally spread along a first axis and focused along a second axis so as to be incident to an interface between the sample and a prism at a range of angles of incidence including a critical angle for at least one wavelength. An imaging detector is situated to receive the spectrally spread and focused light from the interface and form an image corresponding to angle of incidence as a function of wavelength. One or more critical angles are identified and corresponding refractive indices are determined.

  4. Method for measuring the refractive index distribution of a GRIN lens with heterodyne interferometry

    NASA Astrophysics Data System (ADS)

    Hsieh, H. C.; Chen, Y. L.; Wu, W. T.; Su, D. C.

    2009-06-01

    Based on the Fresnel's equations and the heterodyne interferometry, an alternative method for measuring the refractive index distribution of a GRIN lens is presented. A light coming from the heterodyne light source passes through a quarterwave plate and is incident on the tested GRIN lens. The reflected light passes through an analyzer and an imaging lens; finally it enters a CMOS camera. The interference signals produced by the components of the s- and the p-polarizations are recorded and they are sent to a personal computer to be analyzed. In order to measure the absolute phases of the interference signals accurately, a special condition is chosen. Then, the interference signals become a group of periodic sinusoidal segments, and each segment has an initial phase ψ with the information of the refractive index. Consequently, the estimated data of ψ are substituted into the special equations derived from Fresnel's equations, and the refractive index distribution of the GRIN lens can be obtained. Because of its common-path optical configuration, this method has both merits of the common-path interferometry and the heterodyne interferometry. In addition, the phase can be measured without reference signals.

  5. Kramers-Kronig analysis on the real refractive index of porous media in the terahertz spectral range.

    PubMed

    Silfsten, Pertti; Kontturi, Ville; Ervasti, Tuomas; Ketolainen, Jarkko; Peiponen, Kai-Erik

    2011-03-01

    We present a terahertz time-domain experimental technique for the detection of scattering from porous media. The method for detection of the scattering enables one to make a decision when Fresnel or Kramers-Kronig (K-K) analysis can be applied for a porous medium. In this study the real refractive index of a tablet is calculated using the conventional K-K dispersion relation and also using a singly subtractive K-K relation, which are applied to the extinction coefficient obtained from the Beer-Lambert law. The advantage of the K-K analysis is that one gets estimates both for absolute refractive index and also dispersion of the porous tablet, whereas Fresnel analysis provides only the absolute value of the index. PMID:21368980

  6. Quantum vacuum emission from a moving refractive index front

    NASA Astrophysics Data System (ADS)

    Jacquet, M.; Knig, F.

    2015-09-01

    We investigate the spontaneous emission of light from the quantum vacuum in a dispersive dielectric at a moving Refractive Index Front (RIF). Our aim is to develop further an existing analytical model to fully characterize the emission and calculate its spectrum in different configurations. We show in which conditions the RIF acts as a point of non-return, an artificial black hole event horizon, for modes of the field. We calculate the spectrum of this emission and the number of photons emitted from the vacuum in the unique escaping mode as a function of the RIF height and velocity in the medium.

  7. Tissue Refractive Index Fluctuations Report on Cancer Development

    NASA Astrophysics Data System (ADS)

    Popescu, Gabriel

    2012-02-01

    The gold standard in histopathology relies on manual investigation of stained tissue biopsies. A sensitive and quantitative method for in situ tissue specimen inspection is highly desirable, as it will allow early disease diagnosis and automatic screening. Here we demonstrate that quantitative phase imaging of entire unstained biopsies has the potential to fulfill this requirement. Our data indicates that the refractive index distribution of histopathology slides, which contains information about the molecular scale organization of tissue, reveals prostate tumors. These optical maps report on subtle, nanoscale morphological properties of tissues and cells that cannot be recovered by common stains, including hematoxylin and eosin (H&E). We found that cancer progression significantly alters the tissue organization, as exhibited in our refractive index maps. Furthermore, using the quantitative phase information, we obtained the spatially resolved scattering mean free path and anisotropy factor g for entire biopsies and demonstrated their direct correlation with tumor presence. We found that these scattering parameters are able to distinguish between two adjacent grades, which is a difficult task and relevant for determining patient treatment. In essence, our results show that the tissue refractive index reports on the nanoscale tissue architecture and, in principle, can be used as an intrinsic marker for cancer diagnosis. [4pt] [1] Z. Wang, K. Tangella, A. Balla and G. Popescu, Tissue refractive index as marker of disease, Journal of Biomedical Optics, in press).[0pt] [2] Z. Wang, L. J. Millet, M. Mir, H. Ding, S. Unarunotai, J. A. Rogers, M. U. Gillette and G. Popescu, Spatial light interference microscopy (SLIM), Optics Express, 19, 1016 (2011).[0pt] [3] Z. Wang, D. L. Marks, P. S. Carney, L. J. Millet, M. U. Gillette, A. Mihi, P. V. Braun, Z. Shen, S. G. Prasanth and G. Popescu, Spatial light interference tomography (SLIT), Optics Express, 19, 19907-19918 (2011).[0pt] [4] Z. Wang, H. Ding and G. Popescu, Scattering-phase theorem, Optics Letters, 36, 1215 (2011).[0pt] [5] G. Popescu Quantitative phase imaging of cells and tissues (McGraw-Hill, New York, 2011).[0pt] [6] H. F. Ding, Z. Wang, F. Nguyen, S. A. Boppart and G. Popescu, Fourier Transform Light Scattering of Inhomogeneous and Dynamic Structures, Physical Review Letters, 101, 238102 (2008).

  8. Temperature-Dependent Refractive Index Measurements of L-BBH2 Glass for the Subaru CHARIS Integral Field Spectrograph

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Groff, Tyler D.

    2015-01-01

    Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have made the first cryogenic measurements of absolute refractive index for Ohara L-BBH2 glass to enable the design of a prism for the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) at the Subaru telescope. L-BBH2 is employed in CHARIS's prism design for improving the spectrograph's dispersion uniformity. Index measurements were made at temperatures from 110 to 305 K at wavelengths from 0.46 to 3.16 micron. We report absolute refractive index (n), dispersion (dn/d(lambda), and thermo-optic coefficient (dn/dT) for this material along with estimated single measurement uncertainties as a function of wavelength and temperature. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures within applicable ranges. This paper also speaks of the challenges in measuring index for a material which is not available in sufficient thickness to fabricate a typical prism for measurement in CHARMS, the tailoring of the index prism design that allowed these index measurements to be made, and the remarkable results obtained from that prism for this practical infrared material.

  9. Temperature-dependent refractive index measurements of L-BBH2 glass for the Subaru CHARIS integral field spectrograph

    NASA Astrophysics Data System (ADS)

    Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Groff, Tyler D.

    2015-09-01

    Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have made the first cryogenic measurements of absolute refractive index for Ohara L-BBH2 glass to enable the design of a prism for the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) at the Subaru telescope. L-BBH2 is employed in CHARIS's prism design for improving the spectrograph's dispersion uniformity. Index measurements were made at temperatures from 110 to 305 K at wavelengths from 0.46 to 3.16 μm. We report absolute refractive index (n), dispersion (dn/dλ), and thermo-optic coefficient (dn/dT) for this material along with estimated single measurement uncertainties as a function of wavelength and temperature. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures within applicable ranges. This paper also speaks of the challenges in measuring index for a material which is not available in sufficient thickness to fabricate a typical prism for measurement in CHARMS, the tailoring of the index prism design that allowed these index measurements to be made, and the remarkable results obtained from that prism for this practical infrared material.

  10. Spatial Frequency Multiplexing of Fiber-Optic Interferometric Refractive Index Sensors Based on Graded-Index Multimode Fibers

    PubMed Central

    Liu, Li; Gong, Yuan; Wu, Yu; Zhao, Tian; Wu, Hui-Juan; Rao, Yun-Jiang

    2012-01-01

    Fiber-optic interferometric sensors based on graded-index multimode fibers have very high refractive-index sensitivity, as we previously demonstrated. In this paper, spatial-frequency multiplexing of this type of fiber-optic refractive index sensors is investigated. It is estimated that multiplexing of more than 10 such sensors is possible. In the multiplexing scheme, one of the sensors is used to investigate the refractive index and temperature responses. The fast Fourier transform (FFT) of the combined reflective spectra is analyzed. The intensity of the FFT spectra is linearly related with the refractive index and is not sensitive to the temperature.

  11. Modified Kramers-Kronig relations and sum rules for meromorphic total refractive index

    SciTech Connect

    Peiponen, Kai-Erik; Saarinen, Jarkko J.; Vartiainen, Erik M.

    2003-08-01

    Modified Kramers-Kronig relations and corresponding sum rules are shown to hold for the total refractive index that can be presented as a sum of complex linear and nonlinear refractive indices, respectively. It is suggested that a self-action process, involving the degenerate third-order nonlinear susceptibility, can yield a negative total refractive index at some spectral range.

  12. High-refractive-index measurement with an elastomeric grating coupler.

    PubMed

    Kocabas, Askin; Ay, Feridun; Dna, Aykutlu; Kiyat, Isa; Aydinli, Atilla

    2005-12-01

    An elastomeric grating coupler fabricated by the replica molding technique is used to measure the modal indices of a silicon-on-insulator (SOI) planar waveguide structure. Because of the van der Waals interaction between the grating mold and the waveguide, the elastomeric stamp makes conformal contact with the waveguide surface, inducing a periodic index perturbation at the contact region. The phase of the incident light is changed to match the guided modes of the waveguide. The modal and bulk indices are obtained by measuring the coupling angles. This technique serves to measure the high refractive index with a precision better than 10(-3) and allows the elastomeric stamp to be removed without damaging the surface of the waveguide. PMID:16342705

  13. High refractive index sensitivity sensing in gold nanoslit arrays

    NASA Astrophysics Data System (ADS)

    Yuan, Jun; Kan, Qiang; Geng, Zhao-Xin; Xie, Yi-Yang; Wang, Chun-Xia; Chen, Hong-Da

    2014-08-01

    The extraordinary optical transmission (EOT) phenomenon of nano-periodic aperture array in metallic film has been widely investigated and used in biosensors. The surface plasmon resonance and cavity mode in some periodic nanostructures, such as nanohole and nanoslit, cause EOTs at certain wavelengths. This resonance wavelength is sensitive to the refractive index on the surface of periodic nanostructures. Therefore, the metallic nanostructures are expected to be good sensing elements. The sensing performances of gold nanoslit arrays are experimentally and theoretically investigated. Three-dimensional finite difference time domain (FDTD) simulations are utilized to explore their transmission spectra and steady-state field intensity distributions. The electron beam evaporation, electron beam lithography, and ion milling are applied to the gold nanoslit arrays with different widths and periods. The sensing performances of the gold nanoslit array are characterized via transmission spectra in four kinds of refractive index samples. The highest sensitivity reaches 726 nm/RIU when the width of the gold nanoslit array is 38.5 nm.

  14. Refractive index sensing using fluorescence lifetime imaging (FLIM)

    NASA Astrophysics Data System (ADS)

    Tregidgo, Carolyn; Suhling, Klaus

    2007-02-01

    The average fluorescence lifetime of GFP in solution is a function of the refractive index of its environment. Here, we demonstrate that this also appears to be the case for GFP-tagged proteins in cells. Using TCSPC-based FLIM with a scanning confocal microscope, we image GFP-tagged proteins in fixed cells in different media. We find that the average fluorescence lifetime of GFP in cells is shortened, as glycerol or sucrose are added to the medium. This is the case for GFP-tagged MHC proteins with the GFP located inside the cytoplasm, and also for GPI-anchored GFP which is located outside the cell membrane. We observe a linear relationship between the inverse average lifetime of GFP in fixed cells and the square of the refractive index of the medium. Implications of this phenomenon when using Total Internal Reflection Fluorescence (TIRF) microscopy will also be discussed as a shortening of the lifetime is seen close to the glass prism used to produce the evanescent wave in TRIF.

  15. Refractive index of erbium doped GaN thin films

    SciTech Connect

    Alajlouni, S.; Sun, Z. Y.; Li, J.; Lin, J. Y.; Jiang, H. X.; Zavada, J. M.

    2014-08-25

    GaN is an excellent host for erbium (Er) to provide optical emission in the technologically important as well as eye-safe 1540 nm wavelength window. Er doped GaN (GaN:Er) epilayers were synthesized on c-plane sapphire substrates using metal organic chemical vapor deposition. By employing a pulsed growth scheme, the crystalline quality of GaN:Er epilayers was significantly improved over those obtained by conventional growth method of continuous flow of reaction precursors. X-ray diffraction rocking curve linewidths of less than 300 arc sec were achieved for the GaN (0002) diffraction peak, which is comparable to the typical results of undoped high quality GaN epilayers and represents a major improvement over previously reported results for GaN:Er. Spectroscopic ellipsometry was used to determine the refractive index of the GaN:Er epilayers in the 1540 nm wavelength window and a linear dependence on Er concentration was found. The observed refractive index increase with Er incorporation and the improved crystalline quality of the GaN:Er epilayers indicate that low loss GaN:Er optical waveguiding structures are feasible.

  16. Refractive indexes of aqueous LiBr solutions

    SciTech Connect

    Zaltash, A.; Ally, M.R. )

    1992-01-01

    This paper reports that the refractive indexes of water-lithium bromide solutions were measured in the temperature range from 5.0 to 80.0 {degrees}C and in the range of salt concentrations from 0.00 (deionized water) to 58.90 mass %. An electrolyte solution of LlBr in water was chosen for study because of its wide use as an absorption chiller fluid. The concentration of LlBr aqueous solution was determined by argentimetric titration using tetrabromofluoresceln (Eosin) as an adsorption indicator and was checked at a few discrete concentrations (10.06, 20.30, and 58.90 mass % LlBr) against the values obtained by gravimetric analysis. The deviation between values obtained using these two techniques was found to be less than 0.27 mass %. The refractive indexes are shown to represent a reliable and convenient way of measuring the concentration of salt (or water) in LlBr solutions with accuracies of {plus minus}0.3 mass % salt.

  17. Dark Matter Constraints from a Cosmic Index of Refraction

    SciTech Connect

    Gardner, Susan; Latimer, David C.

    2009-04-01

    The dark-matter candidates of particle physics invariably possess electromagnetic interactions, if only via quantum fluctuations. Taken en masse, dark matter can thus engender an index of refraction which deviates from its vacuum value. Its presence is signaled through frequency-dependent effects: the real part yields dispersive effects in propagation, and the imaginary part yields such in attenuation. We discuss theoretical constraints on the expansion of the index of refraction with frequency, the physical interpretation of the terms, and the particular observations needed to isolate its coefficients. This, with the advent of new opportunities to view gamma-ray bursts at cosmological distance scales, gives us a new probe of dark matter. As a first application we use the time delay determined from radio afterglow observations of gamma-ray bursts to limit the charge-to-mass ratio of dark matter to |{var_epsilon}|/M < 1.8 x 10{sup -5} eV{sup -1} at 95% CL.

  18. Dark matter constraints from a cosmic index of refraction

    SciTech Connect

    Gardner, Susan; Latimer, David C.

    2010-09-15

    The dark matter candidates of particle physics invariably possess electromagnetic interactions, if only via quantum fluctuations. Taken en masse, dark matter can thus engender an index of refraction which deviates from its vacuum value. Its presence is signaled through frequency-dependent effects in the propagation and attenuation of light. We discuss theoretical constraints on the expansion of the index of refraction with frequency, the physical interpretation of the terms, and the particular observations needed to isolate its coefficients. This, with the advent of new opportunities to view gamma-ray bursts at cosmological distance scales, gives us a new probe of dark matter and a new possibility for its direct detection. As a first application we use the time delay determined from radio afterglow observations of distant gamma-ray bursts to realize a direct limit on the electric charge-to-mass ratio of dark matter of |{epsilon}|/M<1x10{sup -5} eV{sup -1} at 95% C.L.

  19. Calibration of the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; Barnes, Robert; Baize, Rosemary; O'Connell, Joseph; Hair, Jason

    2010-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) plans to observe climate change trends over decadal time scales to determine the accuracy of climate projections. The project relies on spaceborne earth observations of SI-traceable variables sensitive to key decadal change parameters. The mission includes a reflected solar instrument retrieving at-sensor reflectance over the 320 to 2300 nm spectral range with 500-m spatial resolution and 100-km swath. Reflectance is obtained from the ratio of measurements of the earth s surface to those while viewing the sun relying on a calibration approach that retrieves reflectance with uncertainties less than 0.3%. The calibration is predicated on heritage hardware, reduction of sensor complexity, adherence to detector-based calibration standards, and an ability to simulate in the laboratory on-orbit sources in both size and brightness to provide the basis of a transfer to orbit of the laboratory calibration including a link to absolute solar irradiance measurements.

  20. Terahertz metasurfaces with a high refractive index enhanced by the strong nearest neighbor coupling.

    PubMed

    Tan, Siyu; Yan, Fengping; Singh, Leena; Cao, Wei; Xu, Ningning; Hu, Xiang; Singh, Ranjan; Wang, Mingwei; Zhang, Weili

    2015-11-01

    The realization of high refractive index is of significant interest in optical imaging with enhanced resolution. Strongly coupled subwavelength resonators were proposed and demonstrated at both optical and terahertz frequencies to enhance the refractive index due to large induced dipole moment in meta-atoms. Here, we report an alternative design for flexible free-standing terahertz metasurface in the strong coupling regime where we experimentally achieve a peak refractive index value of 14.36. We also investigate the impact of the nearest neighbor coupling in the form of frequency tuning and enhancement of the peak refractive index. We provide an analytical circuit model to explain the impact of geometrical parameters and coupling on the effective refractive index of the metasurface. The proposed meta-atom structure enables tailoring of the peak refractive index based on nearest neighbor coupling and this property offers tremendous design flexibility for transformation optics and other index-gradient devices at terahertz frequencies. PMID:26561192

  1. Investigation of negative refractive index in reciprocal chiral materials

    NASA Astrophysics Data System (ADS)

    Chatterjee, Monish R.; Banerjee, Partha P.; Anugula, Pradeep R.

    2006-08-01

    It is well known that there exist both natural materials (such as milk or sugar solution) possessing chiral (or handed) properties, as well as an increasing list of man-made materials (such as sodium bromate) that exhibit chirality. One of the principal properties of chirality is that light of any arbitrary polarization, when propagating through a chiral material, splits up into two circular polarizations propagating in different directions. In the past decade or longer, researchers have investigated electromagnetic transverse (plane) wave propagation across a non-chiral/chiral interface, and determined the electromagnetic Fresnel coefficients for such propagation. Traditionally, such coefficients are derived under the assumption that the transmitted circular polarizations in the chiral material have wave numbers that are numerically positive, and nominally point in the direction of electromagnetic energy flow. However, it turns out that the actual solution for the wavenumbers obtained from applying Maxwell's equations to an unbounded, isotropic chiral material yields four possible values dependent upon the chirality parameter. In this paper, we examine the emergence of these wavenumbers, and thereafter explore the conditions necessary for the resulting field solutions to have counter-propagating energy flow and wave vector. Such conditions, if feasible, represent an environment leading to an effectively negative refractive index being generated within the chiral material. Accordingly, propagation within a chiral medium through the mechanism of negative refractive indices may be studied in order to better understand the corresponding optical properties of such materials vis-a-vis transmission of an electromagnetic wave into and out of such a region. The results obtained may be applied to compare negative index chiral materials with the broader emerging field of negative index metamaterials, and explore possible applications.

  2. Demonstrating the error budget for the Climate Absolute Radiance and Refractivity Observatory through solar irradiance measurements

    NASA Astrophysics Data System (ADS)

    Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

    2015-09-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe highaccuracy, long-term climate change trends and to use decadal change observations as a method to determine the accuracy of climate change. A CLARREO objective is to improve the accuracy of SI-traceable, absolute calibration at infrared and reflected solar wavelengths to reach on-orbit accuracies required to allow climate change observations to survive data gaps and observe climate change at the limit of natural variability. Such an effort will also demonstrate National Institute of Standards and Technology (NIST) approaches for use in future spaceborne instruments. The current work describes the results of laboratory and field measurements with the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. SOLARIS allows testing and evaluation of calibration approaches, alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a testbed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. Results of laboratory calibration measurements are provided to demonstrate key assumptions about instrument behavior that are needed to achieve CLARREO's climate measurement requirements. Absolute radiometric response is determined using laser-based calibration sources and applied to direct solar views for comparison with accepted solar irradiance models to demonstrate accuracy values giving confidence in the error budget for the CLARREO reflectance retrieval.

  3. Gradient Refractive Index Optics IOL: Theoretical Background and Clinical Results

    PubMed Central

    Malyugin, Boris; Morozova, Tatiana; Cherednik, Valentin

    2014-01-01

    Purpose: To present the theoretical optical background and clinical results of a new multifocal intraocular lens (MIOL) concept–gradient refractive index optics (Gradiol). Patients and Methods: Original mathematical modeling software was used to calculate optimal construction of the MIOL optic constructed from two polymer materials with different refractive indices. Gradiol lenses were manufactured from hydrophobic acrylic utilizing original step-by-step polymerization technology with the final power difference of of 3.5 D between optic components. Non-comparative prospective clinical study included 26 patients (29 eyes) who were candidates for MIOL implantation. All surgeries were performed at the S. Fyodorov Eye Microsurgery Complex State Institution, Moscow, Russia. After implantation of the Gradiol lenses, the postoperative evaluations included distance (best corrected visual acuity (BCVA)) and near visual acuity (NVA), contrast sensitivity (CS), and amplitude of pseudoaccommodation. Subjective patient's satisfaction was assessed using a questionnaire (VF-14). Results: The mean age of the patients was 62.5 ± 5.7 years (range 27-82 years). All surgical procedures were uneventful. At 6 months postoperatively, the mean uncorrected distance VA was 0.73 ± 0.18, mean uncorrected near VA was 0.57 ± 0.19, mean corrected distance VA was 0.89 ± 0.15, mean corrected near VA was 0.84 ± 0.07, and amplitude of pseudoaccommodation was 4.75 ± 0.5 D. Eighty-six percent of patients were spectacle independent for daily activities and reading. Optical disturbances that were functionally significant were reported by 10.7% of patients postoperatively. Conclusion: The clinical outcomes of this study confirmed the theoretical calculations of constructing MIOL optics from materials with different refractive indices. PMID:24669143

  4. Refractive-index measurement and inverse correction using optical coherence tomography.

    PubMed

    Stritzel, Jenny; Rahlves, Maik; Roth, Bernhard

    2015-12-01

    We describe a novel technique for determination of the refractive index of hard biological tissue as well as nonopaque technical samples based on optical coherence tomography (OCT). Our method relies on an inverse refractive-index correction (I-RIC), which matches a measured feature geometry distorted due to refractive-index boundaries to its real geometry. For known feature geometry, the refractive index can be determined with high precision from the best match between the distorted and corrected images. We provide experimental data for refractive-index measurements on a polymethylmethacrylate (PMMA) and on an ex vivo porcine cranial-bone, which are compared to reference measurements and previously published data. Our method is potentially capable of in vivo measurements on rigid biological tissue such as bone as, for example, is required to improve guidance in robot-aided surgical interventions and also for retrieving complex refractive-index profiles of compound materials. PMID:26625050

  5. Interferometric investigation and simulation of refractive index in glass matrixes containing nanoparticles of varying sizes

    SciTech Connect

    Feeney, Michael Gerard; Ince, Rabia; Yukselici, Mehmet Hikmet; Allahverdi, Cagdas

    2011-07-01

    The relationship between refractive index and nanoparticle radii of cadmium selenide (CdSe) nanoparticles embedded within glass matrixes was investigated experimentally and by simulations. A homemade automated Michelson interferometer arrangement employing a rotating table and a He-Ne laser source at a wavelength of 632.8 nm determined the refractive index versus nanoparticle radii of embedded cadmium selenide (CdSe) nanoparticles. The refractive index was found to decrease linearly with nanoparticle radius increase. However, one sample showed a step increase in refractive index; on spectroscopic analysis, it was found that its resonant wavelength matched that of the He-Ne source wavelength. The simulations showed that two conditions caused the step increase in refractive index: low plasma frequency and matched sample and source resonances. This simple interferometer setup defines a new method of determining the radii of nanoparticles embedded in substrates and enables refractive index tailoring by modification of exact annealing conditions.

  6. Optical Enhancement in Optoelectronic Devices Using Refractive Index Grading Layers.

    PubMed

    Lee, Illhwan; Park, Jae Yong; Gim, Seungo; Kim, Kisoo; Cho, Sang-Hwan; Choi, Chung Sock; Song, Seung-Yong; Lee, Jong-Lam

    2016-02-10

    We enhanced the optical transmittance of a multilayer barrier film by inserting a refractive index grading layer (RIGL). The result indicates that the Fresnel reflection, induced by the difference of refractive indices between SixNy and SiO2, is reduced by the RIGL. To eliminate the Fresnel reflection while maintaining high transmittance, the optimized design of grading structures with the RIGL was conducted using an optical simulator. With the RIGL, we achieved averaged transmittance in the visible wavelength region by 89.6%. It is found that the optimized grading structure inserting the multilayer barrier film has a higher optical transmittance (89.6%) in the visible region than that of a no grading sample (82.6%). Furthermore, luminance is enhanced by 14.5% (from 10 190 to 11 670 cd m(-2) at 30 mA cm(-2)) when the grading structure is applied to organic light-emitting diodes. Finally, the results offer new opportunities in development of multilayer barrier films, which assist industrialization of very cost-effective flexible organic electronic devices. PMID:26800204

  7. Beam propagation in gradient refractive-index media.

    PubMed

    Lawrence, G N; Hwang, S H

    1992-09-01

    A generalized beam propagation method is described that uses the ABCD matrices to treat optical systems that have modest amounts of aberrations including gradient refractive-index elements. We can make calculations from any point in the near or far field to any other point by using appropriate numerical algorithms. The variation of the reduced length is discussed as a limitation to accuracy. The diffraction properties of a complex stigmatic system may be represented by those of an equivalent elementary system. This facilitates calculations using the standard diffraction operations for homogeneous media. The modified propagation technique replaces the large number of diffraction steps commonly used for the split-step solution of inhomogeneous media with one step for stigmatic media and in general no more than a few steps for aberrated media. Maxwell's fisheye lens is discussed in detail to show application of the method. PMID:20733694

  8. Controlling a microdisk laser by local refractive index perturbation

    NASA Astrophysics Data System (ADS)

    Liew, Seng Fatt; Ge, Li; Redding, Brandon; Solomon, Glenn S.; Cao, Hui

    2016-02-01

    We demonstrate a simple yet effective approach of controlling lasing in a semiconductor microdisk by photo-thermal effect. A continuous wave green laser beam, focused onto the microdisk perimeter, can enhance or suppress lasing in different cavity modes, depending on the position of the focused beam. Its main effect is a local modification of the refractive index of the disk, which results in an increase in the power slope of some lasing modes and a decrease of others. The boundary roughness breaks the rotational symmetry of a circular disk, allowing the lasing process to be tuned by varying the green beam position. Using the same approach, we can also fine tune the relative intensity of a quasi-degenerate pair of lasing modes. Such post-fabrication control, enabled by an additional laser beam, is flexible and reversible, thus enhancing the functionality of semiconductor microdisk lasers.

  9. Textile inspired flexible metamaterial with negative refractive index

    NASA Astrophysics Data System (ADS)

    Burgnies, L.; Lheurette, .; Lippens, D.

    2015-04-01

    This work introduces metallo-dielectric woven fabric as a metamaterial for phase-front manipulation. Dispersion diagram as well as effective medium parameters retrieved from reflection and transmission coefficients point out negative values of refractive index. By numerical simulations, it is evidenced that a pair of meandered metallic wires, arranged in a top to bottom configuration, can yield to a textile metamaterial with simultaneously negative permittivity and permeability. While the effective negative permittivity stems from the metallic grid arrangement, resonating current loop resulting from the top to bottom configuration of two meandered metallic wires in near proximity produces magnetic activity with negative permeability. By adjusting the distance between pairs of metallic wires, the electric plasma frequency can be shifted to overlap the magnetic resonance. Finally, it is shown that the woven metamaterial is insensitive to the incident angle up to around 60.

  10. High refractive index chalcogenide glass for photonic crystal applications.

    PubMed

    Paivasaari, Kimmo; Tikhomirov, Victor K; Turunen, Jari

    2007-03-01

    A high refractive index Te-enriched bulk chalcogenide glass Ge(20)As(20)Se(14)Te(46) (n approximately 3.3) has been patterned by ablation using four- and two-beam interference femto-second laser setups operating at 800 nm. The regular arrays of 0.8 mum diameter and more than 0.8 mum depth holes and/or grooves of typical size of 1x1 mm(2) have been written on the surface of the glass in a time-scale of 1 second with 50 femtosecond pulses. The high photosensitivity of this narrow-gap semiconductor glass to the femtosecond irradiation is ascribed to a free electron absorption typical of metals, which is caused by laser-induced heating of the glass. PMID:19532468

  11. Semiconductor laser devices having lateral refractive index tailoring

    DOEpatents

    Ashby, Carol I. H. (Edgewood, NM); Hadley, G. Ronald (Alburquerque, NM); Hohimer, John P. (Albuquerque, NM); Owyoung, Adelbert (Albuquerque, NM)

    1990-01-01

    A broad-area semiconductor laser diode includes an active lasing region interposed between an upper and a lower cladding layer, the laser diode further comprising structure for controllably varying a lateral refractive index profile of the diode to substantially compensate for an effect of junction heating during operation. In embodiments disclosed the controlling structure comprises resistive heating strips or non-radiative linear junctions disposed parallel to the active region. Another embodiment discloses a multi-layered upper cladding region selectively disordered by implanted or diffused dopant impurities. Still another embodiment discloses an upper cladding layer of variable thickness that is convex in shape and symmetrically disposed about a central axis of the active region. The teaching of the invention is also shown to be applicable to arrays of semiconductor laser diodes.

  12. Printable planar lightwave circuits with a high refractive index

    NASA Astrophysics Data System (ADS)

    Pina-Hernandez, Carlos; Koshelev, Alexander; Digianantonio, Lucas; Dhuey, Scott; Polyakov, Aleksandr; Calafiore, Giuseppe; Goltsov, Alexander; Yankov, Vladimir; Babin, Sergey; Cabrini, Stefano; Peroz, Christophe

    2014-08-01

    We report a novel nanofabrication method to fabricate printable integrated circuits with a high refractive index working in the visible wavelength range. The printable planar ligthwave circuits are directly imprinted by ultra-violet nanoimprinting into functional TiO2-based resist on the top of planar waveguide core films. The printed photonic circuits are composed of several elementary components including ridge waveguides, light splitters and digital planar holograms. Multi-mode ridge waveguides with propagation losses around 40 dB cm-1 at 660 nm wavelength, and, on-chip demultiplexers operated in the visible range with 100 channels and a spectral channel spacing around 0.35 nm are successfully demonstrated.

  13. Measurement of the refractive index of highly turbid media

    NASA Astrophysics Data System (ADS)

    Bali, Samir; Williams, Eric; Makkar, Sarabjot; Dong, Miao; Bali, Lalit

    2010-03-01

    We demonstrate a first simultaneous measurement of the real and imaginary parts of the refractive index of a highly turbid medium (scattering coefficient > 200cm-1; by comparison, milk's scattering coefficient in the visible and near-infrared frequencies lies between 40cm-1 and 125cm-1 depending on fat content). We achieve this by observing the real-time reflectance profile of a divergent laser beam made incident on the surface of the turbid medium. We find that the reflectance data is well described, for the first time without any empirical fit-parameters, by Fresnel theory that correctly includes the effect on total internal reflection of angle-dependent penetration into the turbid medium.

  14. Inline fiber interference-based refractive-index sensor

    NASA Astrophysics Data System (ADS)

    Gong, Zhenfeng; Zhang, Xinpu; Liu, Yun; Liu, Zigeng; Yu, Qingxu; Peng, Wei

    2014-11-01

    We report two fiber multiple-mode interferometers formed in photonic crystal fiber (PCF). The interference between the core and the cladding modes of a PCF is utilized. We use two methods to form a coupling point, and the cladding modes are excited from the fundamental core mode. One method is blowing compressed gas into the air holes and discharging at the coupling point; the air holes will expand due to gas expansion in the discharge process. Similarly, the other is discharging at the coupling point after the air is exhausted from the air holes, and the holes will contract during the process. By making another coupling point at a different location along the fiber, the proposed PCF interferometers are implemented. Experimental results show that the sensitivities of the two devices can achieve 1.54 and 1.45 nm for a 0.01 refractive index change.

  15. An alternative method to determine the refractive index of AlxGa1-xN

    NASA Astrophysics Data System (ADS)

    Engelbrecht, J. A. A.; Sephton, B.; Minnaar, E.; Wagener, M. C.

    2016-01-01

    Certain characterizations of AlxGa1-xN epilayers require knowledge of the refractive index. Four theoretical models are reviewed, and a simple method to obtain the refractive index n of AlxGa1-xN is proposed. Values of the refractive index obtained at various wavelengths and Al concentrations are compared to the theoretical models, as well as to previously obtained experimental results. Acceptable agreement with both theoretical and experimental values are obtained.

  16. Integrated refractive index optical ring resonator detector for capillary electrophoresis.

    PubMed

    Zhu, Hongying; White, Ian M; Suter, Jonathan D; Zourob, Mohammed; Fan, Xudong

    2007-02-01

    We developed a novel miniaturized and multiplexed, on-capillary, refractive index (RI) detector using liquid core optical ring resonators (LCORRs) for future development of capillary electrophoresis (CE) devices. The LCORR employs a glass capillary with a diameter of approximately 100 mum and a wall thickness of a few micrometers. The circular cross section of the capillary forms a ring resonator along which the light circulates in the form of the whispering gallery modes (WGMs). The WGM has an evanescent field extending into the capillary core and responds to the RI change due to the analyte conducted in the capillary, thus permitting label-free measurement. The resonating nature of the WGM enables repetitive light-analyte interaction, significantly enhancing the LCORR sensitivity. This LCORR architecture achieves dual use of the capillary as a sensor head and a CE fluidic channel, allowing for integrated, multiplexed, and noninvasive on-capillary detection at any location along the capillary. In this work, we used electro-osmotic flow and glycerol as a model system to demonstrate the fluid transport capability of the LCORRs. In addition, we performed flow speed measurement on the LCORR to demonstrate its flow analysis capability. Finally, using the LCORR's label-free sensing mechanism, we accurately deduced the analyte concentration in real time at a given point on the capillary. A sensitivity of 20 nm/RIU (refractive index units) was observed, leading to an RI detection limit of 10-6 RIU. The LCORR marries photonic technology with microfluidics and enables rapid on-capillary sample analysis and flow profile monitoring. The investigation in this regard will open a door to novel high-throughput CE devices and lab-on-a-chip sensors in the future. PMID:17263318

  17. Fractal anisotropy in tissue refractive index fluctuations: potential role in precancer detection

    NASA Astrophysics Data System (ADS)

    Das, Nandan Kumar; Chatterjee, Subhasri; Chakraborty, Semanti; Panigrahi, P. K.; Pradhan, A.; Ghosh, N.

    2014-05-01

    Differential interference contrast images (DIC) are the direct representation of the refractive index fluctuations of human cervical tissues. These refractive index fluctuations are known to follow self-similar behaviour and in general are multifractal in nature. In this present study, multifractal detrended fluctuation analysis (MFDFA) on refractive index fluctuations from DIC images has been performed by unfolding the tissue-images horizontally and vertically. Our analysis clearly shows that refractive index fluctuations of human cervical tissues are anisotropic-fractal in nature and anisotropy reduced as cancer progress.

  18. Quantitative phase and refractive index analysis of optical fibers using differential interference contrast microscopy.

    PubMed

    Kouskousis, Betty; Kitcher, Daniel J; Collins, Stephen; Roberts, Ann; Baxter, Greg W

    2008-10-01

    A systematic and straightforward image processing method to extract quantitative phase and refractive index data from weak phase objects is presented, obtained using differential interference contrast (DIC) microscopy. The method is demonstrated on DIC images of optical fibers where a directional integration routine is applied to the DIC images to extract phase and refractive index information using the data obtained across the whole DIC image. By applying the inverse Abel transform to the resultant phase images, an accurate refractive index profile is obtained. The method presented here is compared to the refracted near-field technique, typically used to obtain the refractive index profile of optical fibers, and shows excellent agreement. It is concluded that through careful image processing procedures, DIC microscopy can be successfully implemented to obtain quantitative phase and refractive index information of optical fibers. PMID:18830309

  19. 3-D photo-patterning of refractive index structures in photosensitive thin film materials

    DOEpatents

    Potter, Jr., Barrett George (Albuquerque, NM); Potter, Kelly Simmons (Albuquerque, NM)

    2002-01-01

    A method of making a three-dimensional refractive index structure in a photosensitive material using photo-patterning. The wavelengths at which a photosensitive material exhibits a change in refractive index upon exposure to optical radiation is first determined and then a portion of the surface of the photosensitive material is optically irradiated at a wavelength at which the photosensitive material exhibits a change in refractive index using a designed illumination system to produce a three-dimensional refractive index structure. The illumination system can be a micro-lenslet array, a macroscopic refractive lens array, or a binary optic phase mask. The method is a single-step, direct-write procedure to produce a designed refractive index structure.

  20. Fabrication of refractive index distributions in polymer using a photochemical reaction

    NASA Astrophysics Data System (ADS)

    Kada, Takeshi; Obara, Atsushi; Watanabe, Toshiyuki; Miyata, Seizo; Liang, Chuan Xin; Machida, Hideaki; Kiso, Koichi

    2000-01-01

    We demonstrate that a photochemical reaction can create various distributions of refractive index in polymer. When the polymer containing a photochemically active material is irradiated by UV light, the photochemical reaction which breaks the π-conjugated system in the material and decreases its linear polarizability can reduce refractive index of the polymer. We prepared a PMMA film added DMAPN ((4-N,N-dimethylaminophenyl)-N'-phenylnitrone) with a rate of 23 wt % by use of spin coating. Electronic structural change of DMAPN and refractive indices of the film before and after UV irradiation were evaluated by UV absorption spectra and m-line method, respectively. The UV irradiation decreased λmax at 380 nm in the absorption spectra, which is attributed to nitrone, and the refractive indices exponentially with irradiation time. The change of refractive indices reached 0.028. The refractive index profile upon depth of the film was investigated by measuring refractive indices of stacked DMAPN/PMMA films. When UV with a power of 10.7 mW/cm2 irradiated upon three stacked DMAPN/PMMA films for 35 s, variation of the refractive index change showed a quadratic profile. The refractive index profile with various irradiation time can be accounted with the combination of the chemical kinetics with the steady state approximation and Lambert-Beer's law. Thus, the photochemical reaction can be used to control the refractive index distribution in polymer.

  1. Review and assessment of measured values of the nonlinear refractive-index coefficient of fused silica

    SciTech Connect

    Milam, D.

    1998-01-01

    The literature describes more than 30 measurements, at wavelengths between 249 and 1550 nm, of the absolute value of the nonlinear refractive-index coefficient of fused silica. Results of these experiments were assessed and best currently available values were selected for the wavelengths of 351, 527, and 1053 nm. The best values are (3.6{plus_minus}0.64){times}10{sup {minus}16} cm{sup 2}/W at 351 nm, (3.0{plus_minus}0.35){times}10{sup {minus}16} cm{sup 2}/W at 527 nm, and (2.74{plus_minus}0.17){times}10{sup {minus}16} cm{sup 2}/W at 1053 nm. {copyright} 1998 Optical Society of America

  2. Exploiting the image of the surface reflectivity to measure refractive index profiling for various optical fibers.

    PubMed

    Weng, Chun-Jen; Hsu, Ken-Yuh; Chen, Yung-Fu

    2015-05-01

    A direct image method of surface reflectivities on a cleaved fiber end with a filtered halogen lamp and a TE-cooled CCD with high dynamic range is proposed to measure the multi-wavelength refractive index profiling (RIP). A polished black glass is used to be a reference standard for measuring the absolute reflectivity of the fiber end. With the developed calibration procedures, both the spatially dependent sensitivity and spectral responsivity of the CCD pixels can be eliminated to achieve the high spatial accuracy. Tested fiber is connected with a fiber terminator to prevent errors from the backside return light. With the present method, the RIP can be precisely measured for not only multi-mode fibers but also single-mode fibers. PMID:25969266

  3. Refractive Index Measurement within a Photonic Crystal Fibre Based on Short Wavelength Diffraction

    PubMed Central

    Martelli, Cicero; Canning, John; Kristensen, Martin; Groothoff, Nathaniel

    2007-01-01

    A new class of refractive index sensors using solid core photonic crystal fibres is demonstrated. Coherent scattering at the cladding lattice is used to optically characterize materials inserted into the fibre holes. The liquid to solid phase transition of water upon freezing to ice 1h is characterized by determining the refractive index.

  4. Determination of the complex refractive index of cell cultures by reflectance spectrometry

    NASA Astrophysics Data System (ADS)

    Calin, Mihaela Antonina; Calin, Marian Romeo; Munteanu, Constantin

    2014-06-01

    In this paper we propose a new approach to using reflectance spectrometry in connection with the Kramers-Kronig analysis for the determination of the complex refractive index of biological cells. Applying this procedure, the real and imaginary parts of the refractive index (refractive index and extinction coefficient) can be simultaneously determined. The accuracy of this procedure in the determination of the refractive index and extinction coefficient of culture media proved to be comparable with spectroscopic ellipsometry. Applying this procedure on the human umbilical vein endothelial cells (HUVEC), the results obtained from time-series measurements showed significant changes in the complex refractive index of cell cultures within 72h, the most important increases for both real and imaginary parts of the refractive index being recorded in the first 24h, when synthesis processes are happening. Thus, the analysis of the time-dependent changes in the complex refractive index provides information about the frequencies of the modifications that occur on both organizational structure and cells composition during the cell cycle. In conclusion, the combination of reflectance spectrometry with the Kramers-Kronig analysis is a feasible way to determine the complex refractive index of biological cells and to assess the events taking place during the cell cycle.

  5. RELATIONSHIP OF FLY ASH COMPOSITION, REFRACTIVE INDEX, AND DENSITY TO IN-STACK OPACITY

    EPA Science Inventory

    The report gives results of an investigation of the refractive index, density, and composition of fly ash from coal-fired boilers, aimed at determining: (1) the interrelationship of refractive index and composition, and (2) the significance of ash properties on in-stack plume opa...

  6. VizieR Online Data Catalog: Refractive index of hydrocarbon solids (Jones, 2012)

    NASA Astrophysics Data System (ADS)

    Jones, A.

    2012-02-01

    The imaginary part of the complex refractive index m(n,k), k, for a-C:H materials, from 50eV to cm wavelengths, is derived and the real part, n, of the complex refractive index m(n,k) is then calculated using the Kramers-Kronig relations. (2 data files).

  7. New infrared transmitting material via inverse vulcanization of elemental sulfur to prepare high refractive index polymers.

    PubMed

    Griebel, Jared J; Namnabat, Soha; Kim, Eui Tae; Himmelhuber, Roland; Moronta, Dominic H; Chung, Woo Jin; Simmonds, Adam G; Kim, Kyung-Jo; van der Laan, John; Nguyen, Ngoc A; Dereniak, Eustace L; Mackay, Michael E; Char, Kookheon; Glass, Richard S; Norwood, Robert A; Pyun, Jeffrey

    2014-05-21

    Polymers for IR imaging: The preparation of high refractive index polymers (n = 1.75 to 1.86) via the inverse vulcanization of elemental sulfur is reported. High quality imaging in the near (1.5 ?m) and mid-IR (3-5 ?m) regions using high refractive index polymeric lenses from these sulfur materials was demonstrated. PMID:24659231

  8. Refractive index variation in compression molding of precision glass optical components.

    PubMed

    Su, Lijuan; Chen, Yang; Yi, Allen Y; Klocke, Fritz; Pongs, Guido

    2008-04-01

    Compression molding of glass optical components is a high volume near net-shape precision fabrication method. In a compression molding process, a variation of the refractive index occurs along the radial direction of the glass component due to thermal treatment. The variation of refractive index is an important parameter that can affect the performance of optical lenses, especially lenses used for high precision optical systems. Refractive index variations in molded glass lenses under different cooling conditions were investigated using both an experimental approach and a numerical simulation. Specifically, refractive index variations inside molded glass lenses were evaluated by measuring optical wavefront variations with a Shack-Hartmann sensor system. The measured refractive index variations of the molded glass lenses were compared with the numerical simulation as a validation of the modeling approach. PMID:18382598

  9. Reflection based Extraordinary Optical Transmission Fiber Optic Probe for Refractive Index Sensing

    PubMed Central

    Lan, Xinwei; Cheng, Baokai; Yang, Qingbo; Huang, Jie; Wang, Hanzheng; Ma, Yinfa; Shi, Honglan; Xiao, Hai

    2014-01-01

    Fiber optic probes for chemical sensing based on the extraordinary optical transmission (EOT) phenomenon are designed and fabricated by perforating subwavelength hole arrays on the gold film coated optical fiber endface. The device exhibits a red shift in response to the surrounding refractive index increases with high sensitivity, enabling a reflection-based refractive index sensor with a compact and simple configuration. By choosing the period of hole arrays, the sensor can be designed to operate in the near infrared telecommunication wavelength range, where the abundant source and detectors are available for easy instrumentation. The new sensor probe is demonstrated for refractive index measurement using refractive index matching fluids. The sensitivity reaches 573 nm/RIU in the 1.333~1.430 refractive index range. PMID:24574579

  10. Behavior of 157 nm excimer-laser-induced refractive index changes in silica

    SciTech Connect

    Smith, Charlene M.; Borrelli, Nicholas F.

    2006-09-15

    This study describes the observation of large induced refractive index changes produced by 157 nm excimer laser exposure in high-purity synthetic silica glasses. With 157 nm exposure, large induced changes are observed within a few hundred thousand pulses of exposure. Similar to 193 nm exposures, exposure with polarized 157 nm light yields polarization-induced birefringence (PIB). However, the 157 nm exposure also exhibits a behavior not observed with 193 nm exposures; namely, the initial response of the glass is a decrease in refractive index, followed by an increase with continued exposure. An explanation of the behaviors for both wavelength results is proposed where the induced refractive index is considered to arise from two different concurrent phenomena. One produces a decreased refractive index and also accounts for the PIB. The other, which accounts for the increased refractive index, is associated with an isotropic laser-induced volume change.

  11. Silica Bottle Resonator Sensor for Refractive Index and Temperature Measurements

    PubMed Central

    Nemova, Galina; Kashyap, Raman

    2016-01-01

    We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity ~150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 μm. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be ~10 pm/K. The temperature sensitivity can decrease ~10% for a fiber with a radius rco = 10 μm instead of a fiber with a radius rco = 100 μm. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme. PMID:26761011

  12. Double high refractive-index contrast grating VCSEL

    NASA Astrophysics Data System (ADS)

    Gebski, Marcin; Dems, Maciej; Wasiak, Micha?; Sarza?a, Robert P.; Lott, J. A.; Czyszanowski, Tomasz

    2015-03-01

    Distributed Bragg reflectors (DBRs) are typically used as the highly reflecting mirrors of vertical-cavity surface-emitting lasers (VCSELs). In order to provide optical field confinement, oxide apertures are often incorporated in the process of the selective wet oxidation of high aluminum-content DBR layers. This technology has some potential drawbacks such as difficulty in controlling the uniformity of the oxide aperture diameters across a large-diameter (? 6 inch) production wafers, high DBR series resistance especially for small diameters below about 5 ?m despite elaborate grading and doping schemes, free carrier absorption at longer emission wavelengths in the p-doped DBRs, reduced reliability for oxide apertures placed close to the quantum wells, and low thermal conductivity for transporting heat away from the active region. A prospective alternative mirror is a high refractive index contrast grating (HCG) monolithically integrated with the VCSEL cavity. Two HCG mirrors potentially offer a very compact and simplified VCSEL design although the problems of resistance, heat dissipation, and reliability are not completely solved. We present an analysis of a double HCG 980 nm GaAs-based ultra-thin VCSEL. We analyze the optical confinement of such a structure with a total optical thickness is ~1.0? including the optical cavity and the two opposing and parallel HCG mirrors.

  13. Optical polymers with tunable refractive index for nanoimprint technologies

    NASA Astrophysics Data System (ADS)

    Landwehr, J.; Fader, R.; Rumler, M.; Rommel, M.; Bauer, A. J.; Frey, L.; Simon, B.; Fodor, B.; Petrik, P.; Schiener, A.; Winter, B.; Spiecker, E.

    2014-12-01

    In order to realize a versatile high throughput production of micro-optical elements, UV-curable polymer composites containing titanium dioxide nanoparticles were prepared and characterized. The composites are based on an industrial prototype epoxy polymer. Titanium dioxide nanoparticles smaller than 10 nm were synthesized by the nonaqueous sol method and in situ sterically stabilized by three different organic surfactants. The composites exhibit high transparency. Distinct alteration of optical transmission properties for visible light and near IR wavelength range could be avoided by adaption of the stabilizing organic surfactant. Most importantly, the refractive index (RI) of the composites that depends on the fraction of incorporated inorganic nanoparticles could be directly tuned. E.g. the RI at a wavelength of 635 nm of a composite containing 23 wt% titanium dioxide nanoparticles is increased to 1.626, with respect to a value of 1.542 for the pure polymer. Furthermore, it could be demonstrated that the prepared inorganic-organic nanocomposites are well suited for the direct fabrication of low-cost micro-optical elements by nanoimprint lithography. A low response of the optical composite properties to temperature treatment up to 220 °C with a shrinkage of only about 4% ensures its application for integrated micro-optical elements in industrial production.

  14. Refractive index matching improves optical object detection in paper

    NASA Astrophysics Data System (ADS)

    Saarela, J. M. S.; Heikkinen, S. M.; Fabritius, T. E. J.; Haapala, A. T.; Myllyl, R. A.

    2008-05-01

    The demand for high-quality recycled pulp products has increased the need for an efficient deinking process. Assessing process efficiency via residual ink on test sheets has so far been limited to the sheet surface due to the poor transparency of paper. A refractive index matching method was studied to obtain a quantitative measure of particles within the volume of a paper sheet. In actual measurements a glass plate with etched lines from 8.5 m to 281.1 m wide was placed beneath the layers of cleared paper, and visible lines were counted with a microscope. Three different paper grades were tested with transparentizing agents. A diffusion theory-based regression model was used to find a correlation between transparency, paper grammage and paper thickness. These equations enable the determination of the size of an object detectable from a paper with a certain transparentizing agent or the parameters of a test sheet needed to detect objects of a known size. Anise oil was found to be the better of the two agents used, and they both had better transparentizing ability than air or water. The transparent paper grammage of the paper grades was determined for all the tested media. Paper's transparency was found to depend more on paper's thickness than grammage.

  15. Silica Bottle Resonator Sensor for Refractive Index and Temperature Measurements.

    PubMed

    Nemova, Galina; Kashyap, Raman

    2016-01-01

    We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity ~150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 ?m. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be ~10 pm/K. The temperature sensitivity can decrease ~10% for a fiber with a radius rco = 10 ?m instead of a fiber with a radius rco = 100 ?m. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme. PMID:26761011

  16. Optical polymers with tunable refractive index for nanoimprint technologies.

    PubMed

    Landwehr, J; Fader, R; Rumler, M; Rommel, M; Bauer, A J; Frey, L; Simon, B; Fodor, B; Petrik, P; Schiener, A; Winter, B; Spiecker, E

    2014-12-19

    In order to realize a versatile high throughput production of micro-optical elements, UV-curable polymer composites containing titanium dioxide nanoparticles were prepared and characterized. The composites are based on an industrial prototype epoxy polymer. Titanium dioxide nanoparticles smaller than 10 nm were synthesized by the nonaqueous sol method and in situ sterically stabilized by three different organic surfactants. The composites exhibit high transparency. Distinct alteration of optical transmission properties for visible light and near IR wavelength range could be avoided by adaption of the stabilizing organic surfactant. Most importantly, the refractive index (RI) of the composites that depends on the fraction of incorporated inorganic nanoparticles could be directly tuned. E.g. the RI at a wavelength of 635 nm of a composite containing 23 wt% titanium dioxide nanoparticles is increased to 1.626, with respect to a value of 1.542 for the pure polymer. Furthermore, it could be demonstrated that the prepared inorganic-organic nanocomposites are well suited for the direct fabrication of low-cost micro-optical elements by nanoimprint lithography. A low response of the optical composite properties to temperature treatment up to 220 C with a shrinkage of only about 4% ensures its application for integrated micro-optical elements in industrial production. PMID:25427225

  17. Plasmonic circular resonators for refractive index sensors and filters.

    PubMed

    Wei, Wei; Zhang, Xia; Ren, Xiaomin

    2015-01-01

    A plasmonic refractive index sensor based on a circular resonator is proposed. With all three dimensions below 1?m, the sensor has a compact and simple structure granting it ease-of-fabrication and ease-of-use. It is capable of sensing trace amounts of liquid or gas samples. The sensing properties are investigated using finite elements method. The results demonstrate that the plasmonic sensor has a relatively high sensitivity of 1,010nm/RIU, and the corresponding sensing resolution is 9.9??10(-5) RIU. The sensor has a relatively high quality factor of 35, which is beneficial for identifying each transmission spectrum. More importantly, the sensitivity is not sensitive to changes of structure parameters, which means that the sensitivity of the sensor is immune to the fabrication deviation. In addition, with a transmittance of 5% at the resonant wavelength, this plasmonic structure can also be employed as a filter. In addition, by filling material like LiNbO3 or liquid crystal in the circular resonator, this filter can realize an adjustable wavelength-selective characteristic in a wide band. PMID:25991915

  18. Determination of average refractive index of spin coated DCG films for HOE fabrication

    NASA Technical Reports Server (NTRS)

    Kim, T. J.; Campbell, Eugene W.; Kostuk, Raymond K.

    1993-01-01

    The refractive index of holographic emulsions is an important parameter needed for designing holographic optical elements (HOE's). Theoretical calculations of the accuracy required for the refractive index and thickness of emulsions needed to meet predetermined Bragg angle conditions are presented. A modified interferometric method is used to find average refractive index of the unexposed and the developed dichromated gelatin holographic films. Slanted transmission HOE's are designed considering the index and thickness variations, and used to verify the index measurement results. The Brewster angle method is used to measure surface index of the unexposed and the developed films. The differences between average index and surface index are discussed. Theoretical calculation of the effects of index variation on diffraction efficiency, and experimental results for index modulation variation caused by process changes are also presented.

  19. A method to diagnose and combat index of refraction non-uniformity in evaporative optical coatings

    NASA Astrophysics Data System (ADS)

    Bagwell, Joel; Cook, Chris; Ament, Craig

    2015-10-01

    In an optical coating, the thin film engineer must control film thickness and index of refraction to achieve high optical coating performance. While film thickness can generally be controlled with sweeps, sources, and distribution shields, index can be a tougher problem to solve. Often times, contaminants affect the index of refraction of a thin film and cause variations within different portions of the coating chamber leading to poor yield. Presented here is a methodology and case study used to diagnose index of refraction non-uniformity as well as identify the potential sources of contaminants in the system using a combination of Residual Gas Analysis and Secondary Ion Mass Spectrometry.

  20. Index of Refraction Measurements Using a Laser Distance Meter

    ERIC Educational Resources Information Center

    Ochoa, Romulo; Fiorillo, Richard; Ochoa, Cris

    2014-01-01

    We present a simple method to determine the refractive indices of transparent media using a laser distance meter. Indices of refraction have been obtained by measuring the speed of light in materials. Some speed of light techniques use time-of-flight measurements in which pulses are emitted by lasers and the time interval is measured for the pulse

  1. Index of Refraction Measurements Using a Laser Distance Meter

    ERIC Educational Resources Information Center

    Ochoa, Romulo; Fiorillo, Richard; Ochoa, Cris

    2014-01-01

    We present a simple method to determine the refractive indices of transparent media using a laser distance meter. Indices of refraction have been obtained by measuring the speed of light in materials. Some speed of light techniques use time-of-flight measurements in which pulses are emitted by lasers and the time interval is measured for the pulse…

  2. Spatial variation of stratospheric aerosol acidity and model refractive index - Implications of recent results

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Hamill, P.

    1984-01-01

    Recent experimental results indicate that little or no solid ammonium sulfate is present in background stratospheric aerosols. Other results allow straightforward calculation of sulfuric acid/water droplet properties (acidity, specific gravity, refractive index) as functions of stratospheric temperature and humidity. These results are combined with a variety of latitudinal and seasonal temperature and humidity profiles to obtain corresponding profiles of droplet properties. These profiles are used to update a previous model of stratospheric aerosol refractive index. The new model retains the simplifying approximation of vertically constant refractive index in the inner stratosphere, but has sulfuric acid/water refractive index values that significantly exceed the previously used room temperature values. Mean conversion ratios (e.g., extinction-to-number, backscatter-to-volume) obtained using Mie scattering calculations with the new refractive indices are very similar to those obtained for the old indices, because the effects of deleting ammonium sulfate and increasing acid indices tend to cancel each other.

  3. Preliminary Error Budget for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; Gubbels, Timothy; Barnes, Robert

    2011-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) plans to observe climate change trends over decadal time scales to determine the accuracy of climate projections. The project relies on spaceborne earth observations of SI-traceable variables sensitive to key decadal change parameters. The mission includes a reflected solar instrument retrieving at-sensor reflectance over the 320 to 2300 nm spectral range with 500-m spatial resolution and 100-km swath. Reflectance is obtained from the ratio of measurements of the earth s surface to those while viewing the sun relying on a calibration approach that retrieves reflectance with uncertainties less than 0.3%. The calibration is predicated on heritage hardware, reduction of sensor complexity, adherence to detector-based calibration standards, and an ability to simulate in the laboratory on-orbit sources in both size and brightness to provide the basis of a transfer to orbit of the laboratory calibration including a link to absolute solar irradiance measurements. The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe high-accuracy, long-term climate change trends and to use decadal change observations as the most critical method to determine the accuracy of climate change projections such as those in the IPCC Report. A rigorously known accuracy of both decadal change observations as well as climate projections is critical in order to enable sound policy decisions. The CLARREO Project will implement a spaceborne earth observation mission designed to provide rigorous SI traceable observations (i.e., radiance, reflectance, and refractivity) that are sensitive to a wide range of key decadal change variables, including: 1) Surface temperature and atmospheric temperature profile 2) Atmospheric water vapor profile 3) Far infrared water vapor greenhouse 4) Aerosol properties and anthropogenic aerosol direct radiative forcing 5) Total and spectral solar irradiance 6) Broadband reflected and emitted radiative fluxes 7) Cloud properties 8) Surface albedo There are two methods the CLARREO mission will rely on to achieve these critical decadal change benchmarks: direct and reference inter-calibration. A quantitative analysis of the strengths and weaknesses of the two methods has led to the recommended CLARREO mission approach. The project consists of two satellites launched into 90-degree, precessing orbits separated by 90 degrees. The instrument suite receiver on each spacecraft includes one emitted infrared spectrometer, two reflected solar spectrometers: dividing the spectrum from ultraviolet through near infrared, and one global navigation receiver for radio occultation. The measurements will be acquired for a period of three years minimum, with a five-year lifetime goal, enabling follow-on missions to extend the climate record over the decades needed to understand climate change. The current work concentrates on the reflected solar instrument giving an overview of its design and calibration approach. The calibration description includes the approach to achieving an SI-traceable system on orbit. The calibration overview is followed by a preliminary error budget based on techniques currently in place at the National Institute of Standards and Technology (NIST).

  4. Terahertz multi-metal-wire hybrid-cladding hollow waveguide for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Ying-Ying, Yu; Xu-You, Li; Kun-Peng, He; Bo, Sun

    2016-02-01

    We propose a design of terahertz refractive index sensing based on the multi-metal-wire (MMW) hybrid-cladding hollow waveguide. The proposed terahertz hybrid-cladding hollow waveguide comprises one air core in the center surrounding MMW surrounded dielectric. The central air core is used for filling lossless measurands and transmitting terahertz light. In particular, the refractive index sensing is realized by measuring the mode field area (MFA) variation of radially polarized mode. The modal effective refractive index, mode field intensity distribution, and mode field area properties responding to the measurand refractive indexes for different operating frequencies and structure dimensions are investigated, respectively. Simulations show that the proposed terahertz refractive index sensor can realize easily the measurement of the measurand refractive index. Meanwhile, the effects of operating frequency and structure parameters on sensitivity and measurement accuracy are also studied. In view of the trade-off between sensitivity and measurement accuracy, the reasonable choice of the operating frequency and structure parameters can optimize appropriately the sensitivity and measurement accuracy, and the sensitivity can reach approximately 0.585 mm2/RIU (RIU is short for refraction index units) with the proper frequency and structure parameter. Project supported by the National Natural Science Foundation of China (Grant No. 51309059).

  5. Cell refractive index for cell biology and disease diagnosis: past, present and future.

    PubMed

    Liu, P Y; Chin, L K; Ser, W; Chen, H F; Hsieh, C-M; Lee, C-H; Sung, K-B; Ayi, T C; Yap, P H; Liedberg, B; Wang, K; Bourouina, T; Leprince-Wang, Y

    2016-02-21

    Cell refractive index is a key biophysical parameter, which has been extensively studied. It is correlated with other cell biophysical properties including mechanical, electrical and optical properties, and not only represents the intracellular mass and concentration of a cell, but also provides important insight for various biological models. Measurement techniques developed earlier only measure the effective refractive index of a cell or a cell suspension, providing only limited information on cell refractive index and hence hindering its in-depth analysis and correlation. Recently, the emergence of microfluidic, photonic and imaging technologies has enabled the manipulation of a single cell and the 3D refractive index of a single cell down to sub-micron resolution, providing powerful tools to study cells based on refractive index. In this review, we provide an overview of cell refractive index models and measurement techniques including microfluidic chip-based techniques for the last 50 years, present the applications and significance of cell refractive index in cell biology, hematology, and pathology, and discuss future research trends in the field, including 3D imaging methods, integration with microfluidics and potential applications in new and breakthrough research areas. PMID:26732872

  6. Fresnel reflectance in refractive index estimation of light scattering solid particles in immersion liquid

    NASA Astrophysics Data System (ADS)

    Rty, J.; Niskanen, I.; Peiponen, K.-E.

    2010-06-01

    The refractive index of homogenous particle population can be determined by the so-called immersion liquid method. The idea is to find a known liquid whose refractive index matches the index of the particles. We report on a method that simultaneously obtains the refractive index of particles and that of the immersion liquid. It is based on a system using internal light reflection and Fresnel's theory. The method includes a series of straightforward reflection measurements and a fitting procedure. The validity of the method was tested with CaF2 particles. The method has applications within scientific studies of microparticles and nanoparticles or micro-organism in suspensions. It can be also be utilized in industry for the detection of the refractive index of products involving particles for the purpose of improvement of product quality.

  7. The effects of refractive index heterogeneity within kidney tissue on multiphoton fluorescence excitation microscopy.

    PubMed

    Young, P A; Clendenon, S G; Byars, J M; Dunn, K W

    2011-05-01

    Although multiphoton fluorescence excitation microscopy has improved the depth at which useful fluorescence images can be collected in biological tissues, the reach of multiphoton fluorescence excitation microscopy is nonetheless limited by tissue scattering and spherical aberration. Scattering can be reduced in fixed samples by mounting in a medium whose refractive index closely matches that of the fixed material. Using optical 'clearing', the effects of refractive index heterogeneity on signal attenuation with depth are investigated. Quantitative measurements show that by mounting kidney tissue in a high refractive index medium, less than 50% of signal attenuates in 100 μm of depth. PMID:21118239

  8. Reflectivity of a disordered monolayer estimated by graded refractive index and scattering models.

    PubMed

    Diamant, Ruth; Garcí-Valenzuela, Augusto; Fernández-Guasti, Manuel

    2012-09-01

    Reflectivity of a random monolayer, consisting of transparent spherical particles, is estimated using a graded refractive index model, an effective medium approach, and two scattering models. Two cases, a self-standing film and one with a substrate, are considered. Neither the surrounding medium nor the substrate are absorbing materials. Results at normal incidence, with different particle sizes, covering ratios and refractive indexes, are compared. The purpose of this work is to find under which circumstances, for reflectivity at normal incidence, a particle monolayer behaves as a graded refractive index film. PMID:23201948

  9. Refractive index of Al3C2B48 aluminum borocarbide crystals

    NASA Astrophysics Data System (ADS)

    Shelykh, A. I.; Gurin, V. N.; Nikanorov, S. P.

    2008-07-01

    Aluminum borocarbide single crystals have been grown from an Al-based solution melt. The crystal lattice parameters have been determined, the dispersion of the refractive index in a 0.55 1.3 ?m wavelength interval has been studied, and the temperature coefficient of the refractive index in a 300 600 K range has been measured. The crystals are characterized by a high refractive index in the visible spectral range in combination with at a high hardness, which makes them of interest for jewelry, as well as for both traditional and X-ray optics.

  10. Spoof plasmon resonance with 1D periodic grooves for terahertz refractive index sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Yusheng; Hong, Zhi; Han, Zhanghua

    2015-04-01

    We analyze the use of spoof plasmon resonance due to the excitation of spoof surface plasmons in a 1D array of rectangular grooves for terahertz refractive index sensing in an Otto configuration. The dependence of the resonant angle on the change of the refractive index is numerically investigated and a high angular sensitivity about S=320/RIU is demonstrated, which leads to a high resolution of 310-7 RIU assuming 110-4 degree for angular resolution. We further show that by using a slanted geometry an even higher sensitivity up to 452/RIU can be achieved. These results provide a novel method for terahertz refractive index sensing.

  11. Extrinsic fiber-optic Fabry-Perot interferometer sensor for refractive index measurement of optical glass

    SciTech Connect

    Chen Jihuan; Zhao Jiarong; Huang Xuguang; Huang Zhenjian

    2010-10-10

    A simple fiber-optic sensor based on Fabry-Perot interference for refractive index measurement of optical glass is investigated both theoretically and experimentally. A broadband light source is coupled into an extrinsic fiber Fabry-Perot cavity formed by the surfaces of a sensing fiber end and the measured sample. The interference signals from the cavity are reflected back into the same fiber. The refractive index of the sample can be obtained by measuring the contrast of the interference fringes. The experimental data meet with the theoretical values very well. The proposed technique is a new method for glass refractive index measurement with a simple, solid, and compact structure.

  12. Effect of Index of Refraction on Radiation Characteristics in a Heated Absorbing, Emitting, and Scattering Layer

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1992-01-01

    The effect of the index of refraction on the temperature distribution and radiative heat flux in semitransparent materials, such as some ceramics, is investigated analytically. In the case considered here, a plane layer of a ceramic material is subjected to external radiative heating incident on each of its surfaces; the material emits, absorbs, and isotropically scatters radiation. It is shown that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained in a simple manner from the results for an index of refraction of unity.

  13. X-ray refractive index: A tool to determine the average composition in multilayer structures

    SciTech Connect

    Miceli, P.F.; Neumann, D.A.; Zabel, H.

    1986-01-06

    We present a novel and simple method to determine the average composition of multilayers and superlattices by measuring the x-ray refractive index. Since these modulated structures exhibit Bragg reflections at small angles, by using a triple axis x-ray spectrometer we have accurately determined the peak shifts due to refraction in GaAs/Al/sub x/Ga/sub 1-x/As and Nb/Ta superlattices. Knowledge of the refractive index provides the average fractional composition of the periodic structure since the refractive index is a superposition of the refractive indices of the atomic constituents. We also present a critical discussion of the method and compare the values of the average fractional composition obtained in this manner to the values obtained from the lattice parameter change in the GaAs/Al/sub x/Ga/sub 1-x/As superlattices due to the Al.

  14. Correction of image artifacts caused by refractive index gradients in scanning laser optical tomography

    NASA Astrophysics Data System (ADS)

    Antonopoulos, Georgios Christian; Pscheniza, Dimitri; Lorbeer, Raoul-Amadeus; Heidrich, Marko; Schwanke, Kristin; Zweigerdt, Robert; Ripken, Tammo; Meyer, Heiko

    2014-03-01

    We present a technique for correcting image artifacts caused by refractive index distributions in Scanning Laser Optical Tomography (SLOT) and Optical Projection Tomography (OPT). Projection images can be distorted due to the presence of a refractive index distribution around the sample. We consider the special case of a refractive index distribution given by a capillary around a sample. The particular application we are interested in is in vitro imaging of cell spheroids in a glass capillary. Numerical simulations and experimental results are used to illustrate the connection between the Radon transform and the refracted projection. Thereupon we will describe a technique that transforms refracted projections to parallel ray Radon projections and thus allows artifact free reconstruction within the sample volume.

  15. Method of producing optical quality glass having a selected refractive index

    DOEpatents

    Poco, John F. (Livermore, CA); Hrubesh, Lawrence W. (Livermore, CA)

    2000-01-01

    Optical quality glass having a selected refractive index is produced by a two stage drying process. A gel is produced using sol-gel chemistry techniques and first dried by controlled evaporation until the gel volume reaches a pre-selected value. This pre-selected volume determines the density and refractive index of the finally dried gel. The gel is refilled with solvent in a saturated vapor environment, and then dried again by supercritical extraction of the solvent to form a glass. The glass has a refractive index less than the full density of glass, and the range of achievable refractive indices depends on the composition of the glass. Glasses having different refractive indices chosen from an uninterrupted range of values can be produced from a single precursor solution.

  16. Vacuum birefringence in strong magnetic fields: (II) Complex refractive index from the lowest Landau level

    SciTech Connect

    Hattori, Koichi; Itakura, Kazunori; Department of Particle and Nuclear Studies, Graduate University for Advanced Studies , 1-1 Oho, Tsukuba, Ibaraki 305-0801

    2013-07-15

    We compute the refractive indices of a photon propagating in strong magnetic fields on the basis of the analytic representation of the vacuum polarization tensor obtained in our previous paper. When the external magnetic field is strong enough for the fermion one-loop diagram of the polarization tensor to be approximated by the lowest Landau level, the propagating mode in parallel to the magnetic field is subject to modification: The refractive index deviates from unity and can be very large, and when the photon energy is large enough, the refractive index acquires an imaginary part indicating decay of a photon into a fermion–antifermion pair. We study dependences of the refractive index on the propagating angle and the magnetic-field strength. It is also emphasized that a self-consistent treatment of the equation which defines the refractive index is indispensable for accurate description of the refractive index. This self-consistent treatment physically corresponds to consistently including the effects of back reactions of the distorted Dirac sea in response to the incident photon. -- Highlights: •Vacuum birefringence and photon decay are described by the complex refractive index. •Resummed photon vacuum polarization tensor in the lowest Landau level is used. •Back reactions from the distorted Dirac sea are self-consistently taken into account. •Self-consistent treatment drastically changes structure in photon energy dependence. •Dependences on photon propagation angle and magnetic-field strength are presented.

  17. Measuring the refractive index of thin transparent films using an extended cavity diode laser

    NASA Astrophysics Data System (ADS)

    Luetjen, Christopher; Hallsted, Jonathan; Kleinert, Michaela

    2013-12-01

    We report on a novel method for determining refractive indices of thin layers of liquids or gases, based on the use of extended cavity diode lasers. Measurements for air, water, and vegetable oil show excellent agreement with accepted values. Applications in determining the refractive index of thin optical coatings and biological cells are discussed.

  18. Temperature-Dependent Refractive Index of Cleartran® ZnS to Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Leviton, Doug; Frey, Brad

    2013-01-01

    First, let's talk about the CHARMS facility at NASA's Goddard Space Flight Center: Cryogenic, High-Accuracy Refraction Measuring System (CHARMS); design features for highest accuracy and precision; technologies we rely on; data products and examples; optical materials for which we've measured cryogenic refractive index.

  19. On-Column Refractive-Index Detection Based on Retroreflected Beam Interference for Capillary Electrophoresis

    NASA Astrophysics Data System (ADS)

    Deng, Yanzhuo; Li, Bincheng

    1998-02-01

    A novel refractive-index detection scheme used for capillary electrophoresis detection, based on the interference of two retroreflected beams from the outer surface of a capillary tube illuminated by a focused laser beam, is described. A theoretical description and experimental measurement of the intensity profile of the interference fringe pattern in the detection plane are presented. The factors that limit the sensitivity of the proposed refractive-index detection scheme are discussed and compared with the transmitted beam interference and backscatter-based refractive-index detection configurations. The proposed refractive-index detector was used successfully for detection of capillary electrophoresis separations of saccharose, maltose, and lactose with a capillary tube of 50- m inner diameter and a simple experimental setup.

  20. On-chip integrated optofluidic complex refractive index sensing using silicon photonic crystal nanobeam cavities.

    PubMed

    Zhang, Xingwang; Zhou, Guangya; Shi, Peng; Du, Han; Lin, Tong; Teng, Jinghua; Chau, Fook Siong

    2016-03-15

    Complex refractive index sensing is proposed and experimentally demonstrated in optofluidic sensors based on silicon photonic crystal nanobeam cavities. The sensitivities are 58 and 139 nm/RIU, respectively, for the real part (n) and the imaginary part (κ) of the complex refractive index, and the corresponding detection limits are 1.8×10-5 RIU for n and 4.1×10-6 RIU for κ. Moreover, the capability of the complex refractive index sensing method to detect the concentration composition of the ternary mixture is demonstrated without the surface immobilization of functional groups, which is impossible to realize with the conventional refractive index sensing scheme. PMID:26977668

  1. Sensitive Real-Time Monitoring of Refractive Indexes Using a Novel Graphene-Based Optical Sensor

    PubMed Central

    Xing, Fei; Liu, Zhi-Bo; Deng, Zhi-Chao; Kong, Xiang-Tian; Yan, Xiao-Qing; Chen, Xu-Dong; Ye, Qing; Zhang, Chun-Ping; Chen, Yong-Sheng; Tian, Jian-Guo

    2012-01-01

    Based on the polarization-sensitive absorption of graphene under conditions of total internal reflection, a novel optical sensor combining graphene and a microfluidic structure was constructed to achieve the sensitive real-time monitoring of refractive indexes. The atomic thickness and strong broadband absorption of graphene cause it to exhibit very different reflectivity for transverse electric and transverse magnetic modes in the context of a total internal reflection structure, which is sensitive to the media in contact with the graphene. A graphene refractive index sensor can quickly and sensitively monitor changes in the local refractive index with a fast response time and broad dynamic range. These results indicate that graphene, used in a simple and efficient total internal reflection structure and combined with microfluidic techniques, is an ideal material for fabricating refractive index sensors and biosensor devices, which are in high demand. PMID:23205270

  2. Velocity Measurement by Scattering from Index of Refraction Fluctuations Induced in Turbulent Flows

    NASA Technical Reports Server (NTRS)

    Lading, Lars; Saffman, Mark; Edwards, Robert

    1996-01-01

    Induced phase screen scattering is defined as scatter light from a weak index of refraction fluctuations induced by turbulence. The basic assumptions and requirements for induced phase screen scattering, including scale requirements, are presented.

  3. Two novel methods for liquid refractive index or concentration measurement using reflex fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Peng, Bao-jin; Wan, Xu; Wang, Hui; Jin, Hong-zhen; Zhao, Yong

    2006-01-01

    Two novel content meters for liquid refractive index or concentration measurement are proposed based on the simple reflex fiber optic sensor configurations. One sensor exploits a reflex and concentrically arranged fiber probe structure which is very similar to the traditional intensity-modulated fiber optic displacement sensors, but the light captured by receiving fibers is modulated by the varied solute concentration, being in proportion to the liquid refractive index, instead of displacement. The other sensor works based on detecting the edge shift of the reflected light spot, which is modulated by the refractive index variation of the liquid. Theoretical analysis and simulations are carried out with the measurement range of refractive index from 1.0 to 1.5.

  4. Study of Refractive Index Change in Ge-Doped Fibers with Vacuum Ultraviolet Light Irradiation

    NASA Astrophysics Data System (ADS)

    Maezono, Yoshinari; Iwasa, Yousuke; Wasamoto, Makoto; Yamamoto, Ikuo; Katto, Masahito; Yokotani, Atsushi

    2008-09-01

    We determined that refractive index change of Ge-doped silica can be induced by vacuum ultraviolet (VUV) light irradiation from Xe2*, Kr2*, and Ar2* excimer lamps using fabricated fiber Bragg grating (FBG) in the core of the hydrogen-loaded fiber as the material. It was found that irradiation with light from Xe2* and Kr2* excimer lamps can change the refractive index in the core and irradiation with light from Ar2* excimer lamps cannot. The change in refractive index under 146 nm light irradiation was greater than that under 172 nm light irradiation. The change in refractive index induced by irradiation with VUV light can be maintained up to approximately 130 C.

  5. Refractive index of r-cut sapphire under shock pressure range 5 to 65?GPa

    SciTech Connect

    Cao, Xiuxia; Li, Jiabo; Li, Jun; Li, Xuhai; Xu, Liang; Wang, Yuan; Zhu, Wenjun; Meng, Chuanmin; Zhou, Xianming

    2014-09-07

    High-pressure refractive index of optical window materials not only can provide information on electronic polarizability and band-gap structure, but also is important for velocity correction in particle-velocity measurement with laser interferometers. In this work, the refractive index of r-cut sapphire window at 1550?nm wavelength was measured under shock pressures of 565?GPa. The refractive index (n) decreases linearly with increasing shock density (?) for shock stress above the Hugoniot elastic limit (HEL): n?=?2.0485 ( 0.0197)???0.0729 ( 0.0043)?, while n remains nearly a constant for elastic shocks. This behavior is attributed to the transition from elastic (below HEL) to heterogeneous plastic deformation (above HEL). Based on the obtained refractive index-density relationship, polarizability of the shocked sapphire was also obtained.

  6. A Refractive Index Sensor Based on the Resonant Coupling to Cladding Modes in a Fiber Loop

    PubMed Central

    Reyes, Mauricio; Monzn-Hernndez, David; Martnez-Ros, Alejandro; Silvestre, Enrique; Dez, Antonio; Cruz, Jos Luis; Andrs, Miguel V.

    2013-01-01

    We report an easy-to-build, compact, and low-cost optical fiber refractive index sensor. It consists of a single fiber loop whose transmission spectra exhibit a series of notches produced by the resonant coupling between the fundamental mode and the cladding modes in a uniformly bent fiber. The wavelength of the notches, distributed in a wavelength span from 1,400 to 1,700 nm, can be tuned by adjusting the diameter of the fiber loop and are sensitive to refractive index changes of the external medium. Sensitivities of 170 and 800 nm per refractive index unit for water solutions and for the refractive index interval 1.401.442, respectively, are demonstrated. We estimate a long range resolution of 3 10?4 and a short range resolution of 2 10?5 for water solutions. PMID:23979478

  7. Sensitive real-time monitoring of refractive indexes using a novel graphene-based optical sensor.

    PubMed

    Xing, Fei; Liu, Zhi-Bo; Deng, Zhi-Chao; Kong, Xiang-Tian; Yan, Xiao-Qing; Chen, Xu-Dong; Ye, Qing; Zhang, Chun-Ping; Chen, Yong-Sheng; Tian, Jian-Guo

    2012-01-01

    Based on the polarization-sensitive absorption of graphene under conditions of total internal reflection, a novel optical sensor combining graphene and a microfluidic structure was constructed to achieve the sensitive real-time monitoring of refractive indexes. The atomic thickness and strong broadband absorption of graphene cause it to exhibit very different reflectivity for transverse electric and transverse magnetic modes in the context of a total internal reflection structure, which is sensitive to the media in contact with the graphene. A graphene refractive index sensor can quickly and sensitively monitor changes in the local refractive index with a fast response time and broad dynamic range. These results indicate that graphene, used in a simple and efficient total internal reflection structure and combined with microfluidic techniques, is an ideal material for fabricating refractive index sensors and biosensor devices, which are in high demand. PMID:23205270

  8. Determining the size and refractive index of microspheres using the mode assignments from Mie resonances.

    PubMed

    Preston, Thomas C; Reid, Jonathan P

    2015-11-01

    A new method for determining the radius and refractive index of microspheres using Mie resonances is presented. Previous methods have relied on searching multidimensional space to find the radius and refractive index that minimize the difference between observed and calculated Mie resonances. For anything but simple refractive index functions, this process can be very time consuming. Here, we demonstrate that once the mode assignment for the observed Mie resonances is known, no search is necessary, and the radius and refractive index of best-fit can be found immediately. This superior and faster way to characterize microspheres using Mie resonances should supplant previous fitting algorithms. The derivation and implementation of the equations that give the parameters of best-fit are shown and discussed. Testing is performed on systems of physical interest, and the effect of noise on measured peak positions is investigated. PMID:26560936

  9. Simultaneous measurements of radar reflectivity and refractive index spectra in clear air convection.

    NASA Technical Reports Server (NTRS)

    Konrad, T. G.; Robison, F. L.

    1972-01-01

    Simultaneous measurements of radar reflectivity and radio refractive index at several altitudes in clear air convection have been made. The experimental data were compared with the theoretical relationship which relates the reflectivity to the refractivity spectrum. The agreement between the measurements and the theory is excellent and shows that the radar returns in clear air are the result of, and can be quantitatively described as being from, fine-scale refractivity fluctuations due to turbulent mixing. Further, the data give strong support to the -5/3 spectral decay of the refractivity spectrum in the inertial subrange.

  10. Refraction of nonlinear beams by localized refractive index changes in nematic liquid crystals

    SciTech Connect

    Assanto, Gaetano; Minzoni, Antonmaria A.; Smyth, Noel F.; Worthy, Annette L.

    2010-11-15

    The propagation of solitary waves in nematic liquid crystals in the presence of localized nonuniformities is studied. These nonuniformities can be caused by external electric fields, other light beams, or any other mechanism which results in a modified director orientation in a localized region of the liquid-crystal cell. The net effect is that the solitary wave undergoes refraction and trajectory bending. A general modulation theory for this refraction is developed, and particular cases of circular, elliptical, and rectangular perturbations are considered. The results are found to be in excellent agreement with numerical solutions.

  11. The eye lens: age-related trends and individual variations in refractive index and shape parameters

    PubMed Central

    Pierscionek, Barbara; Bahrami, Mehdi; Hoshino, Masato; Uesugi, Kentaro; Regini, Justyn; Yagi, Naoto

    2015-01-01

    The eye lens grows throughout life by cell accrual on its surface and can change shape to adjust the focussing power of the eye. Varying concentrations of proteins in successive cell layers create a refractive index gradient. The continued growth of the lens and age-related changes in proteins render it less able to alter shape with loss of capacity by the end of the sixth decade of life. Growth and protein ageing alter the refractive index but as accurate measurement of this parameter is difficult, the nature of such alterations remains uncertain. The most accurate method to date for measuring refractive index in intact lenses has been developed at the SPring-8 synchrotron. The technique, based on Talbot interferometry, has an X-ray source and was used to measure refractive index in sixty-six human lenses, aged from 16 to 91 years. Height and width were measured for forty-five lenses. Refractive index contours show decentration in some older lenses but individual variations mask age-related trends. Refractive index profiles along the optic axis have relatively flat central sections with distinct micro-fluctuations and a steep gradient in the cortex but do not exhibit an age-related trend. The refractive index profiles in the equatorial aspect show statistical significance with age, particularly for lenses below the age of sixty that had capacity to alter shape in vivo. The maximum refractive index in the lens centre decreases slightly with age with considerable scatter in the data and there are age-related variations in sagittal thickness and equatorial height. PMID:26416418

  12. Quantitative investigation of the refractive-index modulation within the core of a fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Kouskousis, Betty P.; Rollinson, Claire M.; Kitcher, Daniel J.; Collins, Stephen F.; Baxter, Greg W.; Wade, Scott A.; Dragomir, Nicoleta M.; Roberts, Ann

    2006-10-01

    A comparison is made between the modeled and experimentally determined microscopic images of a type I Bragg grating produced in the core of an optical fiber using the ultraviolet irradiation of a phase mask. The simulated image of the refractive-index distribution, which assumes a linear relationship between the irradiation intensity and the refractive-index change, is in good agreement with the measured image.

  13. Quantitative investigation of the refractive-index modulation within the core of a fiber Bragg grating.

    PubMed

    Kouskousis, Betty P; Rollinson, Claire M; Kitcher, Daniel J; Collins, Stephen F; Baxter, Greg W; Wade, Scott A; Dragomir, Nicoleta M; Roberts, Ann

    2006-10-30

    A comparison is made between the modeled and experimentally determined microscopic images of a type I Bragg grating produced in the core of an optical fiber using the ultraviolet irradiation of a phase mask. The simulated image of the refractive-index distribution, which assumes a linear relationship between the irradiation intensity and the refractive-index change, is in good agreement with the measured image. PMID:19529430

  14. Planar optical waveguides for optical panel having gradient refractive index core

    DOEpatents

    Veligdan, James T.

    2004-08-24

    An optical panel is disclosed. A plurality of stacked planar optical waveguides are used to guide light from an inlet face to an outlet face of an optical panel. Each of the optical waveguides comprises a planar sheet of core material having a central plane. The core material has an index of refraction which decreases as the distance from the central plane increases. The decrease in the index of refraction occurs gradually and continuously.

  15. Simple and precise measurement of the complex refractive index and thickness for thin films

    NASA Astrophysics Data System (ADS)

    Peng, Yu; Li, Wei

    2014-07-01

    We demonstrate applications of a novel scheme which is used for measuring refractive index and thickness of thin film by analyzing the relative phase difference and reflected ratio at reflection point of a monolithic folded Fabry-Perot cavity (MFC). The complex refractive index and the thickness are calculated according to the Fresnel formula. Results show that the proposed method has an improvement in accuracy with simple and clear operating process compared with the conventional Ellipsometry.

  16. Planar optical waveguides for optical panel having gradient refractive index core

    DOEpatents

    Veligdan, James T. (6 Stephanie La., Manorville, NY 11949)

    2001-01-01

    An optical panel is disclosed. A plurality of stacked planar optical waveguides are used to guide light from an inlet face to an outlet face of an optical panel. Each of the optical waveguides comprises a planar sheet of core material having a central plane. The core material has an index of refraction which decreases as the distance from the central plane increases. The decrease in the index of refraction occurs gradually and continuously.

  17. Sensing dynamic cytoplasm refractive index changes of adherent cells with quantitative phase microscopy using incorporated microspheres as optical probes

    NASA Astrophysics Data System (ADS)

    Przibilla, Sabine; Dartmann, Sebastian; Vollmer, Angelika; Ketelhut, Steffi; Greve, Burkhard; von Bally, Gert; Kemper, Bjrn

    2012-09-01

    The intracellular refractive index is an important parameter that describes the optical density of the cytoplasm and the concentration of the intracellular solutes. The refractive index of adherently grown cells is difficult to access. We present a method in which silica microspheres in living cells are used to determine the cytoplasm refractive index with quantitative phase microscopy. The reliability of our approach for refractive index retrieval is shown by data from a comparative study on osmotically stimulated adherent and suspended human pancreatic tumor cells. Results from adherent human fibro sarcoma cells demonstrate the capability of the method for sensing of dynamic refractive index changes and its usage with microfluidics.

  18. Refractive index and absorption detector for liquid chromatography based on Fabry-Perot interferometry

    DOEpatents

    Yeung, Edward S.; Woodruff, Steven D.

    1984-06-19

    A refractive index and absorption detector for liquid chromatography. It is based in part on a Fabry-Perot interferometer and is used for the improved detection of refractive index and absorption. It includes a Fabry-Perot interferometer having a normally fixed first partially reflecting mirror and a movable second partially reflecting mirror. A chromatographic flow-cell is positioned between the mirrors along the optical axis of a monochromatic laser beam passing through the interferometer. A means for deriving information about the interference fringes coming out of the interferometer is used with a mini-computer to compute the refractive index of the specimen injected into the flow cell. The minicomputer continuously scans the interferometer for continuous refractive index readings and outputs the continuous results of the scans on a chart recorder. The absorption of the specimen can concurrently be scanned by including a second optical path for an excitation laser which will not interfere with the first laser, but will affect the specimen so that absorption properties can be detected. By first scanning for the refractive index of the specimen, and then immediately adding the excitation laser and subsequently scanning for the refractive index again, the absorption of the specimen can be computed and recorded.

  19. Refractive index and absorption detector for liquid chromatography based on Fabry-Perot interferometry

    DOEpatents

    Yeung, E.S.; Woodruff, S.D.

    1984-06-19

    A refractive index and absorption detector are disclosed for liquid chromatography. It is based in part on a Fabry-Perot interferometer and is used for the improved detection of refractive index and absorption. It includes a Fabry-Perot interferometer having a normally fixed first partially reflecting mirror and a movable second partially reflecting mirror. A chromatographic flow-cell is positioned between the mirrors along the optical axis of a monochromatic laser beam passing through the interferometer. A means for deriving information about the interference fringes coming out of the interferometer is used with a mini-computer to compute the refractive index of the specimen injected into the flow cell. The minicomputer continuously scans the interferometer for continuous refractive index readings and outputs the continuous results of the scans on a chart recorder. The absorption of the specimen can concurrently be scanned by including a second optical path for an excitation laser which will not interfere with the first laser, but will affect the specimen so that absorption properties can be detected. By first scanning for the refractive index of the specimen, and then immediately adding the excitation laser and subsequently scanning for the refractive index again, the absorption of the specimen can be computed and recorded. 10 figs.

  20. Method of determining effects of heat-induced irregular refractive index on an optical system.

    PubMed

    Song, Xifa; Li, Lin; Huang, Yifan

    2015-09-01

    The effects of an irregular refractive index on optical performance are examined. A method was developed to express a lens's irregular refractive index distribution. An optical system and its mountings were modeled by a thermomechanical finite element (FE) program in the predicted operating temperature range, -45°C-50°C. FE outputs were elaborated using a MATLAB optimization routine; a nonlinear least squares algorithm was adopted to determine which gradient equation best fit each lens's refractive index distribution. The obtained gradient data were imported into Zemax for sequential ray-tracing analysis. The root mean square spot diameter, modulation transfer function, and diffraction ensquared energy were computed for an optical system under an irregular refractive index and under thermoelastic deformation. These properties are greatly reduced by the irregular refractive index effect, which is one-third to five-sevenths the size of the thermoelastic deformation effect. Thus, thermal analyses of optical systems should consider not only thermoelastic deformation but also refractive index irregularities caused by inhomogeneous temperature. PMID:26368895

  1. Refractive index measurements of single, spherical cells using digital holographic microscopy.

    PubMed

    Schrmann, Mirjam; Scholze, Jana; Mller, Paul; Chan, Chii J; Ekpenyong, Andrew E; Chalut, Kevin J; Guck, Jochen

    2015-01-01

    In this chapter, we introduce digital holographic microscopy (DHM) as a marker-free method to determine the refractive index of single, spherical cells in suspension. The refractive index is a conclusive measure in a biological context. Cell conditions, such as differentiation or infection, are known to yield significant changes in the refractive index. Furthermore, the refractive index of biological tissue determines the way it interacts with light. Besides the biological relevance of this interaction in the retina, a lot of methods used in biology, including microscopy, rely on light-tissue or light-cell interactions. Hence, determining the refractive index of cells using DHM is valuable in many biological applications. This chapter covers the main topics that are important for the implementation of DHM: setup, sample preparation, and analysis. First, the optical setup is described in detail including notes and suggestions for the implementation. Following that, a protocol for the sample and measurement preparation is explained. In the analysis section, an algorithm for the determination of quantitative phase maps is described. Subsequently, all intermediate steps for the calculation of the refractive index of suspended cells are presented, exploiting their spherical shape. In the last section, a discussion of possible extensions to the setup, further measurement configurations, and additional analysis methods are given. Throughout this chapter, we describe a simple, robust, and thus easily reproducible implementation of DHM. The different possibilities for extensions show the diverse fields of application for this technique. PMID:25640428

  2. Polarimetry of moonlight: A new method for determining the refractive index of the lunar regolith

    NASA Astrophysics Data System (ADS)

    Fearnside, Andrew; Masding, Philip; Hooker, Chris

    2016-04-01

    We present a new method for remotely measuring the refractive index of the lunar regolith, using polarised moonlight. Umov's Law correlates the polarisation (Pmax) of scattered moonlight and the albedo (A) of the scattering lunar regolith. We discuss how deviations from this correlation have previously been linked to the so-called 'Polarimetric Anomaly Parameter', (Pmax)aA, which was proposed by Shkuratov and others as being related to variations in regolith grain size. We propose a reinterpretation of that parameter. We develop models of light scattering by regolith grains which predict that variation in the refractive index of regolith grains causes deviations from Umov's Law. Variations in other grain parameters such as grain size and degree of space weathering do not produce this deviation. The models are supported by polarimetric measurements on powdered terrestrial materials of differing refractive index. We derive a simple formula to express the relationship between refractive index and the deviation from Umov's Law and apply it to telescopic measurements of regions of the lunar surface. We show that the Aristarchus Plateau and the Marius Hills regions both comprise materials of unusually low refractive index. These results are consistent with recent estimates of the mineralogy of those areas. Picard and Peirce craters, in Mare Crisium, are shown to contain material of low refractive index similar to highland regions, as has been suggested by earlier studies of these craters.

  3. Quantification of nanoscale nuclear refractive index changes during the cell cycle

    NASA Astrophysics Data System (ADS)

    Bista, Rajan K.; Uttam, Shikhar; Wang, Pin; Staton, Kevin; Choi, Serah; Bakkenist, Christopher J.; Hartman, Douglas J.; Brand, Randall E.; Liu, Yang

    2011-07-01

    Intrigued by our recent finding that the nuclear refractive index is significantly increased in malignant cells and histologically normal cells in clinical histology specimens derived from cancer patients, we sought to identify potential biological mechanisms underlying the observed phenomena. The cell cycle is an ordered series of events that describes the intervals of cell growth, DNA replication, and mitosis that precede cell division. Since abnormal cell cycles and increased proliferation are characteristic of many human cancer cells, we hypothesized that the observed increase in nuclear refractive index could be related to an abundance or accumulation of cells derived from cancer patients at a specific point or phase(s) of the cell cycle. Here we show that changes in nuclear refractive index of fixed cells are seen as synchronized populations of cells that proceed through the cell cycle, and that increased nuclear refractive index is strongly correlated with increased DNA content. We therefore propose that an abundance of cells undergoing DNA replication and mitosis may explain the increase in nuclear refractive index observed in both malignant and histologically normal cells from cancer patients. Our findings suggest that nuclear refractive index may be a novel physical parameter for early cancer detection and risk stratification.

  4. NOTE: Refractive index measurement for biomaterial samples by total internal reflection

    NASA Astrophysics Data System (ADS)

    Jin, Y. L.; Chen, J. Y.; Xu, L.; Wang, P. N.

    2006-10-01

    The refractive index of biological tissue is a fundamental parameter in applications of optical diagnosis and laser treatments. In the present work, the refractive indices and thermo-optic coefficients of some basic biomaterials, such as blood plasma, haemoglobin solution and lipid membrane, were studied by the method of total internal reflection at the wavelengths of 532 and 632.8 nm that are the most frequently used laser wavelengths in the biomedical field. The effects of the sample concentration and the temperature on refractive index were measured, and empirical relationships were summarized, accompanied by a theoretical explanation based on molecular polarization theory. The results provide some fundamental data for the refractive indices of these biomaterials under variant conditions, and also demonstrate that the total internal reflection method is a feasible and reliable way to measure the refractive indices of biological samples.

  5. Targeted alteration of real and imaginary refractive index of biological cells by histological staining.

    PubMed

    Cherkezyan, L; Subramanian, H; Stoyneva, V; Rogers, J D; Yang, S; Damania, D; Taflove, A; Backman, V

    2012-05-15

    Various staining techniques are commonly used in biomedical research to investigate cellular morphology. By inducing absorption of light, staining dyes change the intracellular refractive index due to the Kramers-Kronig relationship. We present a method for creating 2D maps of real and imaginary refractive indices of stained biological cells using their thickness and absorptance. We validate our technique on dyed polystyrene microspheres and quantify the alteration in refractive index of stained biological cells. We reveal that specific staining of individual organelles can increase their scattering cross-section by orders of magnitudes, implying a major impact in the field of biophotonics. PMID:22627509

  6. A point radiator parallel to a plane layer with negative refractive index

    SciTech Connect

    Petrin, A. B.

    2008-09-15

    Focusing of an electromagnetic wave radiated by a point source and transmitted through a plane layer filled with a medium with negative refractive index is considered. An elementary electric Hertzian dipole located in the air (or vacuum) parallel to the boundaries of the layer is considered as a point source of radiation. It is rigorously shown that, after transmitting through a layer with negative refractive index, the electromagnetic wave of the dipole is focused into a certain domain. The dimensions of the focusing region are investigated. The results of the investigation show that the use of homogeneous materials with negative refraction does not allow one to overcome the diffraction limit.

  7. Effects of refractive index mismatch in optical CT imaging of polymer gel dosimeters

    SciTech Connect

    Manjappa, Rakesh; Makki S, Sharath; Kanhirodan, Rajan; Kumar, Rajesh

    2015-02-15

    Purpose: Proposing an image reconstruction technique, algebraic reconstruction technique-refraction correction (ART-rc). The proposed method takes care of refractive index mismatches present in gel dosimeter scanner at the boundary, and also corrects for the interior ray refraction. Polymer gel dosimeters with high dose regions have higher refractive index and optical density compared to the background medium, these changes in refractive index at high dose results in interior ray bending. Methods: The inclusion of the effects of refraction is an important step in reconstruction of optical density in gel dosimeters. The proposed ray tracing algorithm models the interior multiple refraction at the inhomogeneities. Jacob’s ray tracing algorithm has been modified to calculate the pathlengths of the ray that traverses through the higher dose regions. The algorithm computes the length of the ray in each pixel along its path and is used as the weight matrix. Algebraic reconstruction technique and pixel based reconstruction algorithms are used for solving the reconstruction problem. The proposed method is tested with numerical phantoms for various noise levels. The experimental dosimetric results are also presented. Results: The results show that the proposed scheme ART-rc is able to reconstruct optical density inside the dosimeter better than the results obtained using filtered backprojection and conventional algebraic reconstruction approaches. The quantitative improvement using ART-rc is evaluated using gamma-index. The refraction errors due to regions of different refractive indices are discussed. The effects of modeling of interior refraction in the dose region are presented. Conclusions: The errors propagated due to multiple refraction effects have been modeled and the improvements in reconstruction using proposed model is presented. The refractive index of the dosimeter has a mismatch with the surrounding medium (for dry air or water scanning). The algorithm reconstructs the dose profiles by estimating refractive indices of multiple inhomogeneities having different refractive indices and optical densities embedded in the dosimeter. This is achieved by tracking the path of the ray that traverses through the dosimeter. Extensive simulation studies have been carried out and results are found to be matching that of experimental results.

  8. Experimental determination of refractive index of condensed reflectin in squid iridocytes

    PubMed Central

    Ghoshal, Amitabh; DeMartini, Daniel G.; Eck, Elizabeth; Morse, Daniel E.

    2014-01-01

    Loliginid squid dynamically tune the structural iridescence of cells in their skin for active camouflage and communication. Bragg reflectors in these cells consist of membrane-bound lamellae periodically alternating with low refractive index extracellular spaces; neuronal signalling induces condensation of the reflectin proteins that fill the lamellae, consequently triggering the expulsion of water. This causes an increase in refractive index within the lamellae, activating reflectance, with the change in lamellar thickness and spacing progressively shifting the wavelength of reflected light. We used micro-spectrophotometry to measure the functionally relevant refractive index of the high-index lamellae of the Bragg reflectors containing the condensed reflectins in chemically fixed dermal iridocytes of the squid, Doryteuthis opalescens. Our high-magnification imaging spectrometer allowed us to obtain normalized spectra of optically distinct sections of the individual, subcellular, multi-layer Bragg stacks. Replacement of the extracellular fluid with liquids of increasing refractive index allowed us to measure the reflectivity of the Bragg stacks as it decreased progressively to 0 when the refractive index of the extracellular medium exactly matched that of the reflectin-filled lamellae, thus allowing us to directly measure the refractive index of the reflectin-filled lamellae as ncondensed lamellae ? 1.44. The measured value of the physiologically relevant ncondensed lamellae from these bright iridocytes falls within the range of values that we recently determined by an independent optical method and is significantly lower than values previously reported for dehydrated and air-dried reflectin films. We propose that this directly measured value for the refractive index of the squid's Bragg lamellae containing the condensed reflectins is most appropriate for calculations of reflectivity in similar reflectin-based high-index layers in other molluscs. PMID:24694894

  9. Cryogenic Temperature-dependent Refractive Index Measurements of N-BK7, BaLKN3, and SF15 for NOTES PDI

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas F.; Madison, Timothy J.

    2007-01-01

    In order to enable high quality lens designs using N-BK7, BaLKN3, and SF15 at cryogenic temperatures, we have measured the absolute refractive index of prisms of these three materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For N-BK7, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 50 to 300 K at wavelengths from 0.45 to 2.7 micrometers; for BaLKN3 we cover temperatures ranging from 40 to 300 K and wavelengths from 0.4 to 2.6 micrometers; for SF15 we cover temperatures ranging from 50 to 300 K and wavelengths from 0.45 to 2.6 micrometers. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. While we generally find good agreement (plus or minus 2 x 10(exp -4) for N-BK7, less than 1 x 10(exp -4) for the other materials) at room temperature between our measured values and those provided by the vendor, there is some variation between the datasheets provided with the prisms we measured and the catalog values published by the vendor. This underlines the importance of measuring the absolute refractive index of the material when precise knowledge of the refractive index is required.

  10. Refractive index detection with self-mixing interferometry for biosensing applications

    NASA Astrophysics Data System (ADS)

    Mttl, Miia; Wang, Meng; Krehut, Leszek; Hast, Jukka; Myllyl, Risto

    2007-02-01

    This paper presents a novel method for detecting a change in the refractive index of samples. One of its major applications is sensing molecular interaction in biological samples. In our study a self-mixing interferometer (SMI) was chosen as the instrument for measuring the refractive index in free -space. A GaN blue laser diode was used as a light-emitting source. Compared with traditional interferometric configurations, self-mixing interferometry combined with the laser diode package has the advantage of a compact setup and high sensitivity. Long-term stability issue was first concerned in our research. The results showed that in 15 minutes the movement of the fringe pattern formed by the self-interfered laser beam is 13.6 nm. The measurement of the refractive index was performed by adding a heating element to the external cavity of the SMI. The refractive index of the air in the external cavity was varied by the atmospheric temperature. The change in the refractive index of the air was calculated using both a modified Edln equation and the recorded self-interfered signals. The results showed that the change in the refractive index observed from the shift in the fringe pattern is compatible with that calculated with the modified Edln equation, or about 110 -6/C with optical path length of 5 cm. Theoretically, the smallest movement of the fringe pattern that can be detected with our measurement setup is 1.6 nm, corresponding to a 10 -8 change in the refractive index in the external cavity.

  11. [The arctic sea ice refractive index retrieval based on satellite AMSR-E observations].

    PubMed

    Chen, Han-Yue; Bi, Hai-Bo; Niu, Zheng

    2012-11-01

    The refractive index of sea ice in the polar region is an important geophysical parameter. It is needed as a vital input for some numerical climate models and is helpful to classifying sea ice types. In the present study, according to Hong Approximation (HA), we retrieved the arctic sea ice refractive index at 6.9, 10.7, 23, 37, and 89 GHz in different arctic climatological conditions. The refractive indices of wintertime first year (FY) sea ice and summertime ice were derived with average values of 1.78 - 1.75 and 1.724 - 1.70 at different frequencies respectively, which are consistent with previous studies. However, for multiyear (MY) ice, the results indicated relatively large bias between modeled results since 10.7 GHz. At a higher frequency, there is larger MY ice refractive index difference. This bias is mainly attributed to the volume scattering effect on MY microwave radiation due to emergence of massive small empty cavities after the brine water in MY ice is discharged into sea. In addition, the retrieved sea ice refractive indices can be utilized to classify ice types (for example, the winter derivation at 89 GHz), to identify coastal polynyas (winter retrieval at 6.9 GHz), and to outline the areal extent of significantly melting marginal sea ice zone (MIZ) (summer result at 6.9 GHz). The investigation of this study suggests an effective tool of passive microwave remote sensing in monitoring sea ice refractive index variability. PMID:23387184

  12. Electro-optic properties of high-refractive-index glasses

    NASA Astrophysics Data System (ADS)

    Borrelli, Nicholas F.; Aitken, B. G.; Newhouse, Mark A.; Hall, Douglas W.

    1989-12-01

    The electrooptic Kerr effect and its wavelength dispersion have been measured in glasses representing several compositional systems. The measured Kerr effect was large for glasses having large refractive indices, including 1) glasses containing high concentrations of the heavy metals Pb, Bi, and Tl; 2) glasses with high Nb, Ta, and Ti content; and 3) tellurite glasses. Comparison of Xeff(w=w+0+0), obtained from the measured electrooptic data, to values computed from literature values of Xeff(w=w+w-w) suggest an opposition of the electronic and nuclear contributions to the DC effect.

  13. Refractive index sensing using V-shaped polymer optical fibers

    NASA Astrophysics Data System (ADS)

    Lee, Heeyoung; Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro

    2015-11-01

    Although polymer optical fiber (POF) tapers with high flexibility have been used to measure the refractive indices (RIs) of liquids, their fabrication have caused some inconvenience including the need to use external heat sources or chemicals. Here, as an alternative, we develop a simple, secure, and low-cost method of measuring RIs of liquids using V-shaped bent POFs. When the bending angle is 120 (experimentally optimized), with increasing RI, the transmitted power increases almost linearly with a dependence coefficient of approximately 210 dB/RI unit.

  14. Long period grating inscribed in multimode fibre interferometer and its application in refractive index sensing

    NASA Astrophysics Data System (ADS)

    Wang, Pengfei; Zhao, Haoyu; Brambilla, Gilberto; Farrell, Gerald; Yuan, Libo

    2015-09-01

    A long period grating (LPG) is inscribed by a femtosecond laser in the multimode region of a singlemode-multimode-singlemode fibre device to provide a compact refractive index sensor. An average sensitivity of 39 nm/RIU and a resolvable index change of 2.5610-4 are obtained experimentally with a 44.4 mm long multimode fibre over a measured refractive index range of 1.33-1.35. Because of its compactness, ease of fabrication, linear response, high sensitivity, easy connectivity to other fiberized optical components and low cost, this refractometer could find various applications in chemical and biological sensing.

  15. Refractive Index of a Transparent Liquid Measured with a Concave Mirror

    ERIC Educational Resources Information Center

    Joshi, Amitabh; Serna, Juan D.

    2012-01-01

    Measuring the refractive index "n" of a substance or medium is part of every introductory physics course. Various approaches to determine this index have been developed over the years based on the different ways light reflects and transmits in the medium. In this paper, the authors would like to present a simple geometrical derivation of the

  16. Refractive Index of a Transparent Liquid Measured with a Concave Mirror

    ERIC Educational Resources Information Center

    Joshi, Amitabh; Serna, Juan D.

    2012-01-01

    Measuring the refractive index "n" of a substance or medium is part of every introductory physics course. Various approaches to determine this index have been developed over the years based on the different ways light reflects and transmits in the medium. In this paper, the authors would like to present a simple geometrical derivation of the…

  17. Nonlinear refractive index of a rare-earth-doped fiber laser.

    PubMed

    Bochove, Erik

    2004-10-15

    An expression is derived for the intensity-dependent index of refraction of a rare-earth-doped fiber laser by use of a Kramers-Kronig relation and simple rate equations. The solution is applied to examine the properties of the nonlinear index of an ytterbium-doped silicate fiber laser at 975-nm pump and 1080-nm laser wavelengths. PMID:15532284

  18. A Soft 3D Acoustic Metafluid with Dual-Band Negative Refractive Index.

    PubMed

    Raffy, Simon; Mascaro, Benoit; Brunet, Thomas; Mondain-Monval, Olivier; Leng, Jacques

    2016-03-01

    Spherical silica xerogels are efficient acoustic Mie resonators. When these sub-wavelength inclusions are dispersed in a matrix, the final metafluid may display a negative acoustic refractive index upon a set of precise constraints concerning material properties, concentration, size, and dispersity of the inclusions. Because xerogels may sustain both pressure and shear waves, several bands with negative index can be tailored. PMID:26671783

  19. High refractive index composite for broadband antireflection in terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Wang, Xuecheng; Li, Yunzhou; Cai, Bin; Zhu, YiMing

    2015-06-01

    In this study, titania-polymer composites with a very high refractive-index tenability and high transparency in the terahertz region were prepared. By controlling the blending ratio of the titania particle, a broad refractive-index tuning range from 1.5 to 3.1 was realized. Then, the composites were used to fabricate antireflective (AR) layers of high-resistivity silicon (HR-Si). By utilizing the thermoplasticity of the titania-polymer composite, a graded-index structure was fabricated via a hot-embossing method. Because of the good refractive-index matching between the composite and the HR-Si substrate, a broadband (0.2-1.6 THz, 7% reflection) AR layer was fabricated.

  20. Simultaneous measurement of refractive-index and thickness for optical materials by laser feedback interferometry.

    PubMed

    Xu, Ling; Zhang, Shulian; Tan, Yidong; Sun, Liqun

    2014-08-01

    The refractive index measurement by ordinary interferometers cannot avoid the air disturbances in the optical path. A novel approach is presented in this paper based on the Nd:YAG microchip laser feedback interferometry (MLFI) with 1064 nm wavelength. For eliminating the air flow and electric-heating influence the heterodyne modulation and quasi-common path in the MLFI are used. The simultaneous measurement with high accuracy of the refractive index and thickness is realized. The measurement results for three kinds of materials are presented including N-SF57 glass with high index up to 1.81057. The measurement uncertainty of refractive index is better than 0.00002 and of thickness is better than 0.0006 mm. PMID:25173250

  1. Complex Refractive Index of Ammonium Nitrate in the 2-20 micron Spectral Range

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Norman, Mark L.; Fuller, Kirk A.; Srivastava, Vandana; Cutten, Dean R.

    2002-01-01

    Using high resolution Fourier Transform Infrared Spectroscopy (FTIR) absorbance/transmittance spectral data for ammonium sulfate (AMS), calcium carbonate (CAC) and ammonium nitrate (AMN), comparisons were made with previously published complex refractive indices data for AMS and CAC to infer experimental parameters to determine the imaginary refractive index for AMN in the infrared wavelength range from 2 to 20 microns. Kramers-Kronig mathematical relations were applied to calculate the real refractive index for the three compositions. Excellent agreement for AMS and CAC with the published values was found, validating the complex refractive indices obtained for AMN. Backscatter calculations using a lognormal size distribution for AMS, AMN, and CAC aerosols were performed to show differences in their backscattered spectra.

  2. Three-Dimensional Holographic Refractive-Index Measurement of Continuously Flowing Cells in a Microfluidic Channel

    NASA Astrophysics Data System (ADS)

    Sung, Yongjin; Lue, Niyom; Hamza, Bashar; Martel, Joseph; Irimia, Daniel; Dasari, Ramachandra R.; Choi, Wonshik; Yaqoob, Zahid; So, Peter

    2014-02-01

    The refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, the refractive index contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving-parts approach that provides three-dimensional refractive-index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate refractive-index maps of the samples from the measured spectra. Using this method, we demonstrate label-free three-dimensional imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass, and density of these cells from the measured three-dimensional refractive-index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, shows promise as a quantitative tool for stain-free characterization of a large number of cells.

  3. Acoustic method for the determination of the effective temperature and refractive index of air

    NASA Astrophysics Data System (ADS)

    Lassila, Antti; Korpelainen, Virpi

    2003-11-01

    An acoustic method for measurement of the effective temperature and refractive index of air along a laser beam path is described. The method can be used to improve the accuracy of interferometric length measurements outside the best laboratories, and even in severe environmental conditions. The method is based on the measurement of the speed of ultrasound over the same distance measured with a laser interferometer. The effectiveness of the method derives from the fact that the relative effect of a change in air temperature is about two thousand times greater on the speed of sound than on the refractive index of air. Experimental equations for the effective temperature or refractive index of air as a function of the speed of sound, pressure, humidity and CO2 concentration are fitted using the measured speed of sound, the Cramer equation, the dispersion correction and Edln equations. The standard uncertainties of the effective temperature and the refractive index of air equations are estimated to be 15 mK and 1.710-8, respectively. The uncertainties of the effective temperature and refractive index of air measured with the test setup were 25 mK and 2.610-8 (for L = ~5 m), respectively.

  4. Infrared non-planar plasmonic perfect absorber for enhanced sensitive refractive index sensing

    NASA Astrophysics Data System (ADS)

    Cheng, Yongzhi; Mao, Xue Song; Wu, Chenjun; Wu, Lin; Gong, RongZhou

    2016-03-01

    We present a non-planar all-metal plasmonic perfect absorber (PA) with response polarization independent in infrared region, which can be served as a sensor for enhanced refractive index sensing. Distinct from previous designs, the proposed PA consisted of all metal structured film constructed with an assembly of four-tined rod resonators (FRRs). The PA with a high quality-factor (Q-factor) of 41.2 and an absorbance of 99.9% at 142.6 THz has been demonstrated numerically. The resonance behavior occurs in the space between the rods of the FRRs, which is remarkable different conventional sandwiched structural PAs. Based on equivalent LC circuit theory, the absorption peak can be finely tuned by varying the geometrical dimensions of the FRRs. Furthermore, the resonance frequency shows highly sensitive response to the change of refractive index in the surrounding medium. A careful design for refractive index sensor can yield a sensitivity of 1445 nm/refractive index unit (RIU) and a figure of merit (FOM) of 28.8. The demonstrated design of the plasmonic PA for sensing provides great potential application in enhancing refractive index sensors and the enhanced infrared spectroscopy.

  5. Analysis of interferograms of refractive index inhomogeneities produced in optical materials

    NASA Astrophysics Data System (ADS)

    Tarjnyi, N.

    2014-12-01

    Optical homogeneity of materials intended for optical applications is one of the criterions which decide on an appropriate application method for the material. The existence of a refractive index inhomogeneity inside a material may disqualify it from utilization or by contrary, provide an advantage. For observation of a refractive index inhomogeneity, even a weak one, it is convenient to use any of interferometric methods. They are very sensitive and provide information on spatial distribution of the refractive index, immediately. One can use them also in case when the inhomogeneity evolves in time, usually due to action of some external fields. Then, the stream of interferograms provides a dynamic evolution of a spatial distribution of the inhomogeneity. In the contribution, there are presented results of the analysis of interferograms obtained by observing the creation of a refractive index inhomogeneity due to illumination of thin layers of a polyvinyl-alcohol/acrylamide photopolymer and a plate of photorefractive crystal, lithium niobate, by light and a refractive index inhomogeneity originated at the boundary of two layers of polydimethylsiloxane. The obtained dependences can be used for studying of the mechanisms responsible for the inhomogeneity creation, designing various technical applications or for diagnostics of fabricated components.

  6. The use of a conical lens to find the refractive index of liquids

    NASA Astrophysics Data System (ADS)

    Anguiano-Morales, Marcelino; Salas Peimbert, Didia P.; Trujillo-Schiaffino, Gerardo

    2011-01-01

    In this work, the basic idea is to determine the refractive index of liquids unknown using a conical lens. The measurement of the refractive index of liquids is an important work in engineering and science since is one of the most important optical parameter. The adulteration problem is increasing day by day; therefore it is necessary to implement new and simple devices for measure the refractive index of several materials. There is a great variety of interferometric methods that may be used for determining the refractive index. However, these methods either need sophisticated equipment or have low accuracy. Our system consists of a conical lens coupled to a cylindrical container with a liquid whose composition can be changed easily or adulterated. The diameter of the emergent beam of the container is associated to the specific index of refraction of each substance. Any adulteration of the liquid will be reflected in the diameter of the beam, which will be detected by a charge-coupled device (CCD). Our hypothesis is supported by developed mathematical calculations and numerical simulations.

  7. Control of Refractive Index of Fluorinated Polyimide by Proton Beam Irradiation

    NASA Astrophysics Data System (ADS)

    Arai, Yukitaka; Ohki, Yoshimichi; Saito, Keisuke; Nishikawa, Hiroyuki

    2013-01-01

    To clarify the feasibility of controlling the refractive index of a polymer by proton beam irradiation, we irradiated 1.0 MeV protons to a fluorinated polyimide film. Before and after the proton irradiation at a fluence between 11014 and 71016 cm-2, the film surface was scanned by a profilometer. It was found that the depth of a dent, which increases with fluence, was induced by the irradiation. The refractive index of the ion-irradiated region was calculated using the Lorentz-Lorenz equation, substituting the depth of the dent and the projected range of the protons. When the fluorinated polyimide was irradiated at a fluence of 71016 cm-2, the refractive index increased by about 3.3%, which agrees with the increment in refractive index measured by spectroscopic ellipsometry. The increment in refractive index (0.21%) induced by the irradiation of protons at the fluence of 11015 cm-2 is comparable to the value (0.35%) observed when protons were irradiated to SiO2 glass at a similar fluence. Therefore, it is reasonable to assume that the ion irradiation to a polymer can be a good method for fabricating a high-performance polymer-based optical waveguide.

  8. Determination of Diameter and Index of Refraction of Textile Fibers by Laser Backscattering

    SciTech Connect

    H. Okuda; B. Stratton; L. Meixler; P. Efthimion; D.Mansfield

    2003-07-24

    A new method was developed to determine both diameters and indices of refraction and hence the birefringence of cylindrical textile and industrial fibers and bundles by measuring intensity patterns of the scattered light over an interval of scattering angles. The measured intensity patterns are compared with theoretical predictions (Mie theory) to determine fiber diameter and index of refraction. It is shown that the method is simple and accurate and may be useful as an on-line, noncontact diagnostic tool in real time.

  9. Determination of the complex refractive index of highly concentrated hemoglobin solutions using transmittance and reflectance measurements.

    PubMed

    Friebel, Moritz; Meinke, Martina

    2005-01-01

    The complex refractive index of highly concentrated hemoglobin solutions as they appear in red blood cells are determined in the wavelength range of 250 to 1100 nm using transmittance and Fresnel reflectance measurements. The determined real parts of the refractive indices are on average 0.02 units higher than the values found in the literature. The wavelength dependence of the measured data in the UV region differs from the calculated data using the Kramers-Kronig relation. PMID:16409084

  10. Diffraction grating-based sensing optofluidic device for measuring the refractive index of liquids.

    PubMed

    Calixto, Sergio; Bruce, Neil C; Rosete-Aguilar, Martha

    2016-01-11

    We describe a simple and versatile optical sensing device for measuring refractive index of liquids. The sensor consists of a sinusoidal relief grating in a glass cell. Device calibration is done by pouring in the cell different liquids of known refractive indices. Each time a liquid is poured first order intensity is measured. The fabrication process and testing of the prototype device is described. An application in the measurement of temperature is also presented. PMID:26832249

  11. Changes in the refractive index of the stroma and its extrafibrillar matrix when the cornea swells.

    PubMed

    Meek, Keith M; Dennis, Sally; Khan, Shukria

    2003-10-01

    The transparency of the corneal stroma is critically dependent on the hydration of the tissue; if the cornea swells, light scattering increases. Although this scattering has been ascribed to the disruption caused to the arrangement of the collagen fibrils, theory predicts that light scattering could increase if there is an increased mismatch in the refractive indices of the collagen fibrils and the material between them. The purpose of this article is to use Gladstone and Dale's law of mixtures to calculate volume fractions for a number of different constituents in the stroma, and use these to show how the refractive indices of the stroma and its constituent extrafibrillar material would be expected to change as more solvent enters the tissue. Our calculations predict that solvent entering the extrafibrillar space causes a reduction in its refractive index, and hence a reduction in the overall refractive index of the bovine stroma according to the equation n'(s) = 1.335 + 0.04/(0.22 + 0.24 H'), where n'(s) is the refractive index and H' is the hydration of the swollen stroma. This expression is in reasonable agreement with our experimental measurements of refractive index versus hydration in bovine corneas. When the hydration of the stroma increases from H = 3.2 to H = 8.0, we predict that the ratio of the refractive index of the collagen fibrils to that of the material between them increases from 1.041 to 1.052. This change would be expected to make only a small contribution to the large increase in light scattering observed when the cornea swells to H = 8. PMID:14507686

  12. Retrieval of refractive index fields in two-dimensional gradient-index elements from external deflectometry data.

    PubMed

    Lin, Di; Leger, James R

    2016-03-01

    In a previous work, we presented a numerical method for retrieving inhomogeneous refractive index fields in rectangular gradient-index elements from boundary positions and internal boundary slopes associated with a set of interrogating probe beams that transit the medium. The present work extends this method to external boundary beam slopes without knowledge of the refractive index along the surface of the optical element, requiring minimal additional information (outside of beam position and slope data) such as a single known index point inside the medium. The inverse problem is cast as a linear algebraic system describing the deflection of probe beams inside the optical material, and an iterative inversion algorithm is used to generate an index field that produces the boundary value data. By incorporating Snell's law into the system equation through surface values derived from tentative reconstructions of the refractive index, we show in simulation that a series of inversion cycles applied to the system equation accurately recovers the index profile used to generate the test data. PMID:26974909

  13. A naked eye refractive index sensor with a visible multiple peak metamaterial absorber.

    PubMed

    Ma, Heli; Song, Kun; Zhou, Liang; Zhao, Xiaopeng

    2015-01-01

    We report a naked eye refractive index sensor with a visible metamaterial absorber. The visible metamaterial absorber consisting of a silver dendritic/dielectric/metal structure shows multiple absorption peaks. By incorporating a gain material (rhodamine B) into the dielectric layer, the maximal magnitude of the absorption peak can be improved by about 30%. As the metamaterial absorber is sensitive to the refractive index of glucose solutions, it can function as a sensor that quickly responds to variations of the refractive index of the liquid. Meanwhile, since the response is presented via color changes, it can be clearly observed by the naked eyes. Further experiments have confirmed that the sensor can be used repeatedly. PMID:25822141

  14. Suppression of Air Refractive Index Variations in High-Resolution Interferometry

    PubMed Central

    Lazar, Josef; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Buchta, Zdeněk

    2011-01-01

    The influence of the refractive index of air has proven to be a major problem on the road to improvement of the uncertainty in interferometric displacement measurements. We propose an approach with two counter-measuring interferometers acting as a combination of tracking refractometer and a displacement interferometer referencing the wavelength of the laser source to a mechanical standard made of a material with ultra-low thermal expansion. This technique combines length measurement within a specified range with measurement of the refractive index fluctuations in one axis. Errors caused by different position of the interferometer laser beam and air sensors are thus eliminated. The method has been experimentally tested in comparison with the indirect measurement of the refractive index of air in a thermal controlled environment. Over a 1 K temperature range an agreement on the level of 5 × 10−8 has been achieved. PMID:22164036

  15. Measurement of the refractive index of hemoglobin solutions for a continuous spectral region.

    PubMed

    Wang, Jin; Deng, Zhichao; Wang, Xiaowan; Ye, Qing; Zhou, Wenyuan; Mei, Jianchun; Zhang, Chunping; Tian, Jianguo

    2015-07-01

    Determination of the refractive index of hemoglobin solutions over a wide wavelength range remains challenging. A famous detour approach is the Kramers-Kronig (KK) analysis which can resolve the real part of complex refractive index from the imaginary part. However, KK analysis is limited by the contradiction between the requirement of semi-infinite frequency range and limited measured range. In this paper, based on the Multi-curve fitting method (MFM), continuous refractive index dispersion (CRID) of oxygenated and deoxygenated hemoglobin solutions are measured using a homemade symmetrical arm-linked apparatus in the continuous wavelength range with spectral resolution of about 0.259nm. A novel method to obtain the CRID is proposed. PMID:26203379

  16. High-refractive-index transparent coatings enhance the optical fiber cladding modes refractometric sensitivity.

    PubMed

    Renoirt, Jean-Michel; Zhang, Chao; Debliquy, Marc; Olivier, Marie-Georges; Mgret, Patrice; Caucheteur, Christophe

    2013-11-18

    The high order cladding modes of standard single mode optical fiber appear in quasi-degenerate pairs corresponding to mostly radially or mostly azimuthally polarized light. In this work, we demonstrate that, in the presence of a high-refractive-index coating surrounding the fiber outer surface, the wavelength spacing between the orthogonally polarized cladding modes families can be drastically enhanced. This behavior can be advantageously exploited for refractometric sensing purposes. For this, we make use of tilted fiber Bragg gratings (TFBGs) as spectral combs to excite the orthogonally polarized cladding modes families separately. TFBGs were coated with a nanometer-scale transparent thin film characterized by a refractive index value close to 1.9, well higher than the one of pure silica. This coating brings two important assets: an ~8-fold increase in refractometric sensitivity is obtained in comparison to bare TFBGs while the sensitivity is extended to surrounding refractive index (SRI) values above 1.45. PMID:24514423

  17. Negative refractive index designed in a periodic composite of lossy microplasmas and microresonators

    SciTech Connect

    Sakai, Osamu; Shimomura, Takuya; Tachibana, Kunihide

    2010-12-15

    A novel metamaterial with negative refractive index was designed using a spatially periodic composite of microplasmas and microresonators. Microresonators, which are double-helix metal wires in this report, work as an origin of macroscopic negative permeability material, as well as discharge electrodes. If a resonance frequency of the resonators is well below electron plasma frequency of the microplasmas where their permittivity is negative in the real part with a certain imaginary part, the macroscopic refractive index becomes negative just above the resonance frequency where the macroscopic permeability is negative, even if microplasmas are fairly lossy; due to such a loss or conductive component in permittivity, electromagnetic waves are not evanescent but propagating. This result indicates that plasmas can play important roles in parameter control of a metamaterial with a complex refractive index.

  18. Laser-induced refractive index gratings formed in Pr3+-doped sodium-magnesium-aluminosilicate glasses

    NASA Astrophysics Data System (ADS)

    Hamad, Abdulatif Y.; Wicksted, James P.

    2005-03-01

    We report a systematic study of grating formation in which the Pr2O3 concentration [Pr2O3] in sodium-magnesium-aluminosilicate glasses is varied from 0.5to5mol%. The grating kinetics is reported as functions of the [Pr2O3] and the write-beam irradiance. The maximum persistent change in the index of refraction was 1×10-5. The persistent change in the index of refraction initially decreased linearly as a function of the [Pr2O3] and showed a limiting behavior at the highest [Pr2O3]. No appreciable transient change in the index of refraction, Δntran, was measured. This was attributed to the low probability of the multiphonon relaxation of the P03 level of the Pr3+ ions as determined through fluorescence measurements. The results of this study are consistent with a recently developed small modifier diffusion model.

  19. Printable photonic crystals with high refractive index for applications in visible light.

    PubMed

    Calafiore, Giuseppe; Fillot, Quentin; Dhuey, Scott; Sassolini, Simone; Salvadori, Filippo; Mejia, Camilo A; Munechika, Keiko; Peroz, Christophe; Cabrini, Stefano; Piña-Hernandez, Carlos

    2016-03-18

    Nanoimprint lithography (NIL) of functional high-refractive index materials has proved to be a powerful candidate for the inexpensive manufacturing of high-resolution photonic devices. In this paper, we demonstrate the fabrication of printable photonic crystals (PhCs) with high refractive index working in the visible wavelengths. The PhCs are replicated on a titanium dioxide-based high-refractive index hybrid material by reverse NIL with almost zero shrinkage and high-fidelity reproducibility between mold and printed devices. The optical responses of the imprinted PhCs compare very well with those fabricated by conventional nanofabrication methods. This study opens the road for a low-cost manufacturing of PhCs and other nanophotonic devices for applications in visible light. PMID:26875825

  20. Printable photonic crystals with high refractive index for applications in visible light

    NASA Astrophysics Data System (ADS)

    Calafiore, Giuseppe; Fillot, Quentin; Dhuey, Scott; Sassolini, Simone; Salvadori, Filippo; Mejia, Camilo A.; Munechika, Keiko; Peroz, Christophe; Cabrini, Stefano; Piña-Hernandez, Carlos

    2016-03-01

    Nanoimprint lithography (NIL) of functional high-refractive index materials has proved to be a powerful candidate for the inexpensive manufacturing of high-resolution photonic devices. In this paper, we demonstrate the fabrication of printable photonic crystals (PhCs) with high refractive index working in the visible wavelengths. The PhCs are replicated on a titanium dioxide-based high-refractive index hybrid material by reverse NIL with almost zero shrinkage and high-fidelity reproducibility between mold and printed devices. The optical responses of the imprinted PhCs compare very well with those fabricated by conventional nanofabrication methods. This study opens the road for a low-cost manufacturing of PhCs and other nanophotonic devices for applications in visible light.

  1. Refractive index measurement based on fiber Bragg grating connected with a multimode fiber core

    NASA Astrophysics Data System (ADS)

    Shao, Min; Qiao, Xueguang; Jiasurname, Zhenan; Fusurname, Haiwei; Liu, Yinggang; Li, Huidong; Zhao, Xue

    2015-09-01

    A novel fiber refractive index sensor based on a fiber-Bragg grating (FBG) connected with a section of multimode fiber core (MMFC) is proposed and demonstrated. The MMFC excites high-order modes to form modal interference, and the core mode reflected by the FBG is sensitive to the surrounding refractive index (SRI) for the power of the core mode within MMFC is dependent on SRI. Measuring the reflective power variation of the core mode could realize the refractive index (RI) detection. Experimental results show that the core mode of FBG has a linear response to RI with enhanced sensitivity of 193.55 dB/RIU in the RI range of 1.3350-1.4042 RIU. The temperature effect of the sensor is also discussed.

  2. Measurement of the refractive index of hemoglobin solutions for a continuous spectral region

    PubMed Central

    Wang, Jin; Deng, Zhichao; Wang, Xiaowan; Ye, Qing; Zhou, Wenyuan; Mei, Jianchun; Zhang, Chunping; Tian, Jianguo

    2015-01-01

    Determination of the refractive index of hemoglobin solutions over a wide wavelength range remains challenging. A famous detour approach is the Kramers-Kronig (KK) analysis which can resolve the real part of complex refractive index from the imaginary part. However, KK analysis is limited by the contradiction between the requirement of semi-infinite frequency range and limited measured range. In this paper, based on the Multi-curve fitting method (MFM), continuous refractive index dispersion (CRID) of oxygenated and deoxygenated hemoglobin solutions are measured using a homemade symmetrical arm-linked apparatus in the continuous wavelength range with spectral resolution of about 0.259nm. A novel method to obtain the CRID is proposed. PMID:26203379

  3. Femtosecond pulse shaping by modulating the refractive index modulation of volume holographic grating.

    PubMed

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

    2013-03-25

    Based on the modified Kogelnik's coupled-wave theory, time- and frequency-domain diffractions of a femtosecond pulse from transmitted volume holographic gratings (VHGs) are theoretically studied. Results show that when the refractive index modulation of the VHG changes in a certain range, the number of temporal diffracted pulse will evolve from one to two, then to three, and this pulse number evolution is periodic. This particular phenomenon can be explained by diffraction intensity spectrum and the overmodulation effect of refractive index modulation of transmitted VHG. Moreover, we find centers of all temporal diffracted pulses translate along the negative time axis, and the translation is irrelevant to the refractive index modulations. We will use time delay of volume grating to give a reasonable explanation. PMID:23546138

  4. A polarization maintaining evanescent field sensor for measuring liquid refractive index change

    NASA Astrophysics Data System (ADS)

    Cherif, Rim; Ben Salem, Amine; Zghal, Mourad

    2013-05-01

    A modified Mach-Zehnder interferometer (MZI) design based on elliptical silica photonic nanowires is proposed and demonstrated numerically. The MZI is used as a highly sensitive evanescent field based refractive index sensor. By applying a full vectorial finite element method, single-mode operation, polarization maintaining and very high sensitivity are achieved by simply using 800 nm-elliptical silica nanowires. Using the highly-sensitive versatile interferometry technique, the phase shift from both arms is determined and consequently the specimen's information can be retrieved. The proposed sensor is used to determine the refractive index (RI) of NaCl solutions with different concentrations. The sensor is capable of detecting a refractive index variation of the order of 10-6 RI unit with a high sensitivity of 4.2 rad/?m.

  5. Gamma radiation-induced refractive index change in Ge- and N-doped silica

    SciTech Connect

    Brichard, Benoit; Butov, Oleg V.; Golant, Konstantin M.; Fernandez Fernandez, Alberto

    2008-03-01

    We measured the change of the refractive index over a wide wavelength range in Ge- and N-doped high purity (fiber optics grade) silica glasses subjected to gamma irradiation. The radiation-induced change of the refractive index tends to be greater in the infrared part of the spectrum compare to the values measured in the UV-visible part of the spectrum. By means of the Kramers-Kronig relations, we estimate that a weak broadening of the optical vibration band of the silica network adds to this effect. The paper also discusses the difference observed in the spectral behavior of the induced refractive index change for both types of doped glass.

  6. Interferometric Spectroscopy of Scattered Light Can Quantify the Statistics of Subdiffractional Refractive-Index Fluctuations

    NASA Astrophysics Data System (ADS)

    Cherkezyan, L.; Capoglu, I.; Subramanian, H.; Rogers, J. D.; Damania, D.; Taflove, A.; Backman, V.

    2013-07-01

    Despite major importance in physics, biology, and other sciences, the optical sensing of nanoscale structures in the far zone remains an open problem due to the fundamental diffraction limit of resolution. We establish that the expected value of spectral variance (?2) of a far-field, diffraction-limited microscope image can quantify the refractive-index fluctuations of a label-free, weakly scattering sample at subdiffraction length scales. We report the general expression of ? for an arbitrary refractive-index distribution. For an exponential refractive-index spatial correlation, we obtain a closed-form solution of ? that is in excellent agreement with three-dimensional finite-difference time-domain solutions of Maxwells equations. Sensing complex inhomogeneous media at the nanoscale can benefit fields from material science to medical diagnostics.

  7. A Naked Eye Refractive Index Sensor with a Visible Multiple Peak Metamaterial Absorber

    PubMed Central

    Ma, Heli; Song, Kun; Zhou, Liang; Zhao, Xiaopeng

    2015-01-01

    We report a naked eye refractive index sensor with a visible metamaterial absorber. The visible metamaterial absorber consisting of a silver dendritic/dielectric/metal structure shows multiple absorption peaks. By incorporating a gain material (rhodamine B) into the dielectric layer, the maximal magnitude of the absorption peak can be improved by about 30%. As the metamaterial absorber is sensitive to the refractive index of glucose solutions, it can function as a sensor that quickly responds to variations of the refractive index of the liquid. Meanwhile, since the response is presented via color changes, it can be clearly observed by the naked eyes. Further experiments have confirmed that the sensor can be used repeatedly. PMID:25822141

  8. Refractive index measurements of films with biaxial symmetry. 1. Determination of complex refractive indices using polarized reflectance/transmittance ratio.

    PubMed

    Diao, Jie; Hess, Dennis W

    2005-07-01

    A new method to extract complex refractive indices of films with biaxial symmetry from polarized transmission and reflection spectra is described. Theoretical analysis demonstrates that the reflectance/transmittance ratio (R/T ratio) of two films of different thicknesses but with the same optical anisotropy is a simple function of the refractive index (n) and extinction coefficient (k). For films with biaxial symmetry, components of n and k on symmetric axes can be extracted from either s- or p-polarized R/T ratios if the film thickness values are known. The R/T ratio method can generate n and k spectra within a particular wavelength range without assuming a specific relationship among n, k, and wavelength, which is an advantage over many currently available techniques. The R/T ratio method is used to extract the anisotropic complex refractive indices of a polyimide film with known uniaxial symmetry. The resultant n and k spectra compare well with simulations based on known n and k values. The accuracy of n and k spectra is affected mostly by data error in reflection and transmission spectra collection, thickness variation across sample films, and error in sample alignment. PMID:16852588

  9. Two-dimensional refractive index and stresses profiles of a homogenous bent optical fiber.

    PubMed

    Ramadan, W A; Wahba, H H; Shams El-Din, M A

    2014-11-01

    We present a significant contribution to the theory of determining the refractive index profile of a bent homogenous optical fiber. In this theory we consider two different processes controlling the index profile variations. The first is the linear index variation due to stress along the bent radius, and the second is the release of this stress on the fiber surface. This release process is considered to have radial dependence on the fiber radius. These considerations enable us to construct the index profile in two dimensions normal to the optical axis, considering the refraction of light rays traversing the fiber. This theory is applied to optical homogenous bent fiber with two bending radii when they are located orthogonal to the light path of the object arm in the holographic setup (like the Mach-Zehnder interferometer). Digital holographic phase shifting interferometry is employed in this study. The recorded phase shifted holograms have been combined, reconstructed, and processed to extract the phase map of the bent optical fiber. A comparison between the extracted optical phase differences and the calculated one indicates that the refractive index profile variation should include the above mentioned two processes, which are considered as a response for stress distribution across the fiber's cross section. The experimentally obtained refractive index profiles provide the stress induced birefringence profile. Thus we are able to present a realistic induced stress profile due to bending. PMID:25402912

  10. Negative refractive index, perfect lenses and checkerboards: Trapping and imaging effects in folded optical spaces

    NASA Astrophysics Data System (ADS)

    Guenneau, Sbastien; Ramakrishna, S. Anantha

    2009-06-01

    Newly discovered metamaterials have opened new vistas for better control of light via negative refraction, whereby light refracts in the "wrong" manner. These are dielectric and metallic composite materials structured at subwavelength lengthscales. Their building blocks consist of local resonators such as conducting thin bars and split rings driving the material parameters such as the dielectric permittivity and magnetic permeability to negative (complex) values. Combined together, these structural elements can bring about a (complex valued) negative effective refractive index for the Snell-Descartes law and result in negative refraction of radiation. Negative refractive index materials can support a host of surface plasmon states for both polarizations of light. This makes possible unique effects such as imaging with subwavelength image resolution through the Pendry-Veselago slab lens. Other geometries have also been investigated, such as cylindrical or spherical lenses that enable a magnification of images with subwavelength resolution. Superlenses of three-fold (equilateral triangle), four-fold (square) and six-fold (hexagonal) geometry allow for multiple images, respectively two, three, and five. Generalization to rectangular and triangular checkerboards consisting of alternating cells of positive and negative refractive index represents a very singular situation in which the density of modes diverges at the corners, with an infinity of images. Sine-cosecant anisotropic heterogeneous square and triangular checkerboards can be respectively mapped onto three-dimensional cubic and icosahedral corner lenses consisting of alternating positive and negative refractive regions. All such systems with corners between negative and positive refractive media display very singular behavior with the local density of states becoming infinitely large at the corner, in the limit of no dissipation. We investigate all of these, using the unifying viewpoint of transformation optics. To cite this article: S. Guenneau, S.A. Ramakrishna, C. R. Physique 10 (2009).

  11. TECHNICAL DESIGN NOTE: Determining the refractive index of liquids using a cylindrical cuvette

    NASA Astrophysics Data System (ADS)

    Vilitis, O.; Shipkovs, P.; Merkulov, D.

    2009-11-01

    The refractive index of a liquid carries important information about its physical properties, including concentration and density, thus making it possible to determine and monitor the composition of the solution. This is important in fundamental research, chemical analysis and medical diagnostics, as well as in the processing and manufacturing of various substances. The authors have developed a compact and adaptable device of high sensitivity for measuring the refractive indices of both stationary liquids and continuous liquid flows. This device can be used in various technological processes requiring real-time analysis of flowing liquid substances, including aggressive compounds. The refractive index is determined by measuring the deviation of a laser beam passed through a cylindrical cuvette containing the test liquid. The magnitude of the deviation, which depends on the RI, is measured as the displacement of the transmitted beam's projection on a linear measuring element, such as a linear CMOS or CCD image sensor. In order to significantly improve the resolution and stability of RI measurements, an efficient solution has been developed, based on repeated reflection and refraction of the light beam travelling through the cylindrical cuvette with liquid. By this, deviation of the rays exiting the cuvette increases several times in respect to refractive index of the liquid. Additionally, a new method for detecting the position of the projected laser beam on a linear optical sensor is employed. Also, an increase in the intensity of the exiting rays has been achieved. By applying the techniques developed, it is possible to achieve high resolution and stability of refractive index measurements even when the distance between the image sensor and the cuvette is short. Hence, a basis for the construction of accurate and compact devices for determining the refractive indices of liquids is provided, suitable for a broad spectrum of applications.

  12. Meshless method for solving coupled radiative and conductive heat transfer in refractive index medium

    NASA Astrophysics Data System (ADS)

    Wang, Cheng-An; Sadat, Hamou; Tan, Jian-Yu

    2016-01-01

    A diffuse approximation meshless method (DAM) is employed as a means of solving the coupled radiative and conductive heat transfer problems in semi-transparent refractive index media contained in 1D and 2D geometries. The meshless approach for radiative transfer is based on the discrete ordinates equation. Cases of combined conduction- radiation are presented, including plane parallel slab, square enclosure, and semicircular enclosure with an inner circle. The influence of the refractive index on the temperature distributions and heat fluxes is investigated. Results obtained using the proposed meshless method are compared with those reported in the literature to demonstrate the flexibility and accuracy of the method.

  13. Mechanisms of the refractive index change in femtosecond laser-irradiated Au3+-doped silicate glasses

    NASA Astrophysics Data System (ADS)

    Zhao, Quan-Zhong; Qiu, Jian-Rong; Jiang, Xiong-Wei; Zhao, Chong-Jun; Zhu, Cong-Shan

    2004-12-01

    We report on the refractive index change in Au3+-doped silicate glasses irradiated by a femtosecond laser and successive heat treatment. The refractive index of the irradiated area increased after the femtosecond laser irradiation and decreased with increasing annealing temperature up to 450C and then increased again with increasing annealing temperature. Absorption spectra of the glass samples before and after femtosecond laser irradiation and after further annealing manifested the formation of color centers after laser irradiation, disappearance of color centers after annealing at 300C, and precipitation of gold nanoparticles after annealing at high temperature. The mechanisms of the observed phenomena are discussed.

  14. Refraction index measurement using long period grating fabricated by symmetrical-hole fiber

    NASA Astrophysics Data System (ADS)

    Kang, Juan; Dong, Xinyong; Li, Mengchao; Zhang, Zaixuan; Jin, Shangzhong

    2010-12-01

    A Long-Period Fiber Grating (LPFG) fabricated by CO2 laser in a symmetrical two-hole single-mode fiber (STHSMF) for refraction index (RI) measurement is demonstrated. The solved sugar liquid of different concentration was filled into the holes by capillary force and its RI was experimentally measured. The results show that resonant peak shifts toward shorter wavelengths with its resonance peak intensity changes a little when the external refractive index increases. RI sensitivity of 141.67 nm/RIU have been achieved with R2 of 0.975.The temperature sensitivity of the STHSMF is also investigated.

  15. Refraction index measurement using long period grating fabricated by symmetrical-hole fiber

    NASA Astrophysics Data System (ADS)

    Kang, Juan; Dong, Xinyong; Li, Mengchao; Zhang, Zaixuan; Jin, Shangzhong

    2011-01-01

    A Long-Period Fiber Grating (LPFG) fabricated by CO2 laser in a symmetrical two-hole single-mode fiber (STHSMF) for refraction index (RI) measurement is demonstrated. The solved sugar liquid of different concentration was filled into the holes by capillary force and its RI was experimentally measured. The results show that resonant peak shifts toward shorter wavelengths with its resonance peak intensity changes a little when the external refractive index increases. RI sensitivity of 141.67 nm/RIU have been achieved with R2 of 0.975.The temperature sensitivity of the STHSMF is also investigated.

  16. Large photoinduced refractive index changes of a polymer containing photochromic norbornadiene groups

    SciTech Connect

    Kinoshita, K.; Horie, K.; Morino, S.; Nishikubo, T.

    1997-06-01

    We prepared a polymer containing pendant norbornadiene (NBD) moieties, P(MMA{sub 0.43}-co-GMA{sub 0.57}-PNCA), and measured absorbance and refractive index spectra before and after photoisomerization of norbornadiene moieties. Large photoinduced refractive index changes of {approximately}0.01 were obtained at 632.8 nm, the region far from the absorption band. A quantum yield of 0.50 was obtained for the photoisomerization of NBD moieties in this polymer. These values are sufficient to make efficient channel waveguides by photoisomerization. {copyright} {ital 1997 American Institute of Physics.}

  17. Broadband focusing and collimation of water waves by zero refractive index

    PubMed Central

    Zhang, Chi; Chan, C. T.; Hu, Xinhua

    2014-01-01

    It is always a challenge to realize extreme and unusual values of refractive index for a broad range of frequencies. We show that when water is covered by a thick, rigid and unmovable plate, it behaves like a medium with zero refractive index for water waves at any frequency. Hence, by covering water with a plate of a concave or rectangular shape, water waves can be focused or collimated in a broad range of frequencies. Experiments were conducted to demonstrate these effects and results are in excellent agreement with numerical simulations. PMID:25381845

  18. Optimization of 3D plasmonic crystal structures for refractive index sensing.

    SciTech Connect

    Maria, J.; Truong, T. T.; Yao, J.; Lee, T-W.; Nuzzo, R. G.; Leyffer, S.; Gray, S. K.; Rogers, J. A.

    2009-05-21

    We study the refractive index sensitive transmission of a 3D plasmonic crystal that consists of a square array of subwavelength cylindrical nanowells in a polymer conformally coated with a gold film. Using extensive 3D finite-difference time-domain simulations, we investigate the effect of system parameters such as periodicity, well diameter and depth, and metal thickness on its refractive index sensitivity. These theoretical results are also confirmed experimentally in some cases. Our calculations predict an enhancement in sensitivity by an order of magnitude when the plasmonic crystal characteristics are optimized.

  19. Matching index of refraction using a diethyl phthalate/ethanol solution for in vitro cardiovascular models

    NASA Astrophysics Data System (ADS)

    Miller, P.; Danielson, K.; Moody, G.; Slifka, A.; Drexler, E.; Hertzberg, J.

    2006-09-01

    Experiments studying cardiovascular geometries require a working fluid that matches the high index of refraction of glass and silicone, has a low viscosity, and is safe and inexpensive. A good candidate working fluid is diethyl phthalate (DEP), diluted with ethanol. Measurements were made of index of refraction and viscosity of varied dilutions at a range of temperatures, and empirical models are proposed. Material compatibility tests showed that only specific formulations of ABS, acrylic, vinyl and PVC are compatible. A silicone elastomer additionally tested negative for change in compliance with DEP exposure.

  20. Three-dimensional negative index of refraction at optical frequencies by coupling plasmonic waveguides.

    PubMed

    Verhagen, Ewold; de Waele, Ren; Kuipers, L; Polman, Albert

    2010-11-26

    We identify a route towards achieving a negative index of refraction at optical frequencies based on coupling between plasmonic waveguides that support backwards waves. We show how modal symmetry can be exploited in metal-dielectric waveguide pairs to achieve negative refraction of both phase and energy. Control of waveguide coupling yields a metamaterial consisting of a one-dimensional multilayer stack that exhibits an isotropic index of -1 at a free-space wavelength of 400nm. The concepts developed here may inspire new low-loss metamaterial designs operating close to the metal plasma frequency. PMID:21231386

  1. High-precision confocal reflection measurement for two dimensional refractive index mapping of optical fibers

    NASA Astrophysics Data System (ADS)

    Raisin, Philippe; Scheuner, Jonas; Romano, Valerio; Ryser, Manuel

    2015-05-01

    We introduce a new fiber-optical approach for reflection based refractive index mapping. Our approach leads to improved stability and reliability over existing free-space confocal instruments and significantly cuts alignment efforts and reduces the number of components needed. Other than properly cleaved fiber end-faces, this setup requires no additional sample preparation. The instrument is calibrated by means of a set of samples with known refractive indices. The index steps of commercially available fibers are measured accurately down to < 10-3. The precision limit of the instrument is currently of the order of 10-4.

  2. Observation of a multiply ionized plasma with index of refraction greater than one

    SciTech Connect

    Filevich, J; Rocca, J J; Marconi, M C; Moon, S J; Nilsen, J; Scofield, J H; Dunn, J; Smith, R F; Keenan, R; Hunter, J R; Shlyaptsev, V N

    2004-10-14

    We present clear experimental evidence showing that the contribution of bound electrons can dominate the index of refraction of laser created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms show that this results from the dominant contribution of low charge ions to the index of refraction. This usually neglected bound electron contribution can a.ect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.

  3. Determination of refraction nonlinear index, for effect thermal, of solutions with nanoparticles of gold

    NASA Astrophysics Data System (ADS)

    Olivares-Vargas, A.; Trejo-Durn, M.; Alvarado-Mndez, E.; Cornejo-Monroy, D.; Mata-Chvez, R. I.; Estudillo-Ayala, J. M.; Castao-Meneses, V.

    2013-09-01

    Research of nonlinear optical properties of materials for manufacturing opto-electronic devices, had a great growth in the last years. The solutions with nanoparticle metals present nonlinear optical properties. In this work we present the results of characterizing, analyzing and determining the magnitude and sign of the nonlinear refractive index, using the z-scan technique in solutions with nanoparticles of gold, lipoic acid and sodium chloride. We used a continuous Argon laser at 514 nm with variable power, an 18 cms lens, and a chopper. We determined the nonlinear refractive index in the order of 10-9. These materials have potential applications mainly as optical limiters.

  4. Measuring a refractive index at high pressure in a diamond anvil cell

    SciTech Connect

    Kuryaeva, R.G.; Kirkinskii, V.A.

    1995-06-01

    A technique is suggested for measuring the refractive index of isotropic materials in an apparatus with diamond anvils using an interference-polarization microscope. The refraction index of a methanol-ethanol mixture versus pressure has been measured for pressures from 0 to 5.0 GPa with an error {delta}n-{+-}0.0035 at P=2.5 GPa, and of a basalt glass at a pressure of up to 2.5 GPa with an error less than {delta}n=0.045 at the maximum pressure.

  5. Real-time compensation of the refractive index of air in distance measurement.

    PubMed

    Kang, Hyun Jay; Chun, Byung Jae; Jang, Yoon-Soo; Kim, Young-Jin; Kim, Seung-Woo

    2015-10-01

    A two-color scheme of heterodyne laser interferometer is devised for distance measurements with the capability of real-time compensation of the refractive index of the ambient air. A fundamental wavelength of 1555 nm and its second harmonic wavelength of 777.5 nm are generated, with stabilization to the frequency comb of a femtosecond laser, to provide fractional stability of the order of 3.0 × 10(-12) at 1 s averaging. Achieved uncertainty is of the order of 10(-8) in measuring distances of 2.5 m without sensing the refractive index of air in adverse environmental conditions. PMID:26480151

  6. Optical fiber Fabry-Perot refractive index sensor based on porous Al2O3 film

    NASA Astrophysics Data System (ADS)

    Huang, Chujia; Yang, Minghong; Xie, Weijing; Dai, Jixiang

    2015-08-01

    A fiber refractive index sensor based on porous alumina is fabricated by pasting porous alumina film with 42.36?m on single mode fiber tip using the UV-cured adhesive. Experimental results show that the proposed sensor has a very high correlation with glycerine concentration (0.0%~80.0%) with correlation coefficient of 99.771%. Its sensitivity and resolution was measure to be 99.771%, 154 nm/RIU and 110-4 respectively when the refractive index changes from 1.333 to 1.443.

  7. Effect of Index of Refraction on Radiation Characteristics in a Heated Absorbing, Emitting, and Scattering Layer

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1992-01-01

    The index of refraction can considerably influence the temperature distribution and radiative heat flow in semitransparent materials such as some ceramics. For external radiant heating, the refractive index influences the amount of energy transmitted into the interior of the material. Emission within a material depends on the square of its refractive index, and hence this emission can be many times that for a biackbody radiating into a vacuum. Since radiation exiting through an interface into a vacuum cannot exceed that of a blackbody, there is extensive reflection at the internal surface of an interface, mostly by total internal reflection. This redistributes energy within the layer and tends to make its temperature distribution more uniform. The purpose of the present analysis is to show that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained very simply from the results for an index of refraction of unity. For the situation studied here, the layer is subjected to external radiative heating incident on each of its surfaces. The material emits, absorbs, and isotropically scatters radiation. For simplicity the index of refraction is unity in the medium surrounding the layer. The surfaces of the layer are assumed diffuse. This is probably a reasonable approximation for a ceramic layer that has not been polished. When transmitted radiation or radiation emitted from the interior reaches the inner surface of an interface, the radiation is diffused and some of it thereby placed into angular directions for which there is total internal reflection. This provides a trapping effect for retaining energy within the layer and tends to equalize its temperature distribution. An analysis of temperature distributions in absorbing-emitting layers, including index of refraction effects, was developed by Gardon (1958) to predict cooling and heat treating of glass plates. The interfaces were optically smooth; the resulting specular reflections were computed from the Fresnel reflection laws. This provides a somewhat different behavior than for diffuse interfaces. A similar application was for heating that occurs in a window of a re-entry vehicle (Fowle et al., 1969). A number of recent papers (Rokhsaz and Dougherty, 1989; Ping and Lallemand, 1989; Crosbie and Shieh, 1990) further examined the effects of Fresnel boundary reflections and nonunity refractive index. Other examples of analyses of both steady and transient heat transfer to single or multiple plane layers (Amlin and Korpela, 1979; Tarshis et al., 1969) have used diffuse assumptions at the interfaces as in the present study

  8. Crystalline sulfur dioxide: Crystal field splittings, absolute band intensities and complex refractive indices derived from infrared spectra

    NASA Technical Reports Server (NTRS)

    Khanna, R. K.; Zhao, Guizhi

    1986-01-01

    The infrared absorption spectra of thin crystalline films of sulfur dioxide at 90 K are reported in the 2700 to 450/cm region. The observed multiplicity of the spectral features in the regions of fundamentals is attributed to factor group splittings of the modes in a biaxial crystal lattice and the naturally present minor S-34, S-36, and O-18 isotopic species. Complex refractive indices determined by an iterative Kramers-Kronig analysis of the extinction data, and absolute band strengths derived from them, are also reported in this region.

  9. Highly sensitive refractive index fiber inline Mach-Zehnder interferometer fabricated by femtosecond laser micromachining and chemical etching

    NASA Astrophysics Data System (ADS)

    Sun, Xiao-Yan; Chu, Dong-Kai; Dong, Xin-Ran; Zhou, Chu; Li, Hai-Tao; Luo-Zhi; Hu, You-Wang; Zhou, Jian-Ying; Cong-Wang; Duan, Ji-An

    2016-03-01

    A High sensitive refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed, which is fabricated by femtosecond laser transversal-scanning inscription method and chemical etching. A rectangular cavity structure is formed in part of fiber core and cladding interface. The MZI sensor shows excellent refractive index sensitivity and linearity, which exhibits an extremely high RI sensitivity of -17197 nm/RIU (refractive index unit) with the linearity of 0.9996 within the refractive index range of 1.3371-1.3407. The experimental results are consistent with theoretical analysis.

  10. The Paul wavelet algorithm: an alternative approach to calculate the refractive index dispersion of a dielectric film from transmittance spectrum

    NASA Astrophysics Data System (ADS)

    Co?kun, Emre; zder, Serhat; Tiryaki, Erhan

    2013-11-01

    A new application of the Paul wavelet algorithm was presented to determine the refractive index dispersion of a dielectric film from transmittance spectrum in the visible and near infrared region. The developed algorithm was tested by simulated data and experimentally applied to a sample of mica. The obtained refractive index dispersion determined by the Paul wavelet algorithm was compared with the refractive index values determined by the envelope and fringe counting methods, and also with the established result. It was shown that the degree of the Paul wavelet has a major effect on the outcome of a refractive index determination. The noise immunity of the presented method was shown by the simulation study.

  11. Retrieving the Vertical Structure of the Effective Aerosol Complex Index of Refraction from a Combination of Aerosol in Situ and Remote Sensing Measurements During TARFOX

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Turco, R. P.; Liou, K. N.; Russell, P. B.; Bergstrom, R. W.; Schmid, B.; Livingston, J. M.; Hobbs, P. V.; Hartley, W. S.; Ismail, S.; Ferrare, R. A.; Browell, E. V.

    2000-01-01

    The largest uncertainty in estimates of the effects of atmospheric aerosols on climate stems from uncertainties in the determination of their microphysical properties, including the aerosol complex index of refraction, which in turn determines their optical properties. A novel technique is used to estimate the aerosol complex index of refraction in distinct vertical layers from a combination of aerosol in situ size distribution and remote sensing measurements during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX). In particular, aerosol backscatter measurements using the NASA Langley LASE (Lidar Atmospheric Sensing Experiment) instrument and in situ aerosol size distribution data are utilized to derive vertical profiles of the "effective" aerosol complex index of refraction at 815 nm (i.e., the refractive index that would provide the same backscatter signal in a forward calculation on the basis of the measured in situ particle size distributions for homogeneous, spherical aerosols). A sensitivity study shows that this method yields small errors in the retrieved aerosol refractive indices, provided the errors in the lidar-derived aerosol backscatter are less than 30% and random in nature. Absolute errors in the estimated aerosol refractive indices are generally less than 0.04 for the real part and can be as much as 0.042 for the imaginary part in the case of a 30% error in the lidar-derived aerosol backscatter. The measurements of aerosol optical depth from the NASA Ames Airborne Tracking Sunphotometer (AATS-6) are successfully incorporated into the new technique and help constrain the retrieved aerosol refractive indices. An application of the technique to two TARFOX case studies yields the occurrence of vertical layers of distinct aerosol refractive indices. Values of the estimated complex aerosol refractive index range from 1.33 to 1.45 for the real part and 0.001 to 0.008 for the imaginary part. The methodology devised in this study provides, for the first time, a complete set of vertically resolved aerosol size distribution and refractive index data. yielding the vertical distribution of aerosol optical properties required for the determination of aerosol-induced radiative flux changes.

  12. Retrieving the Vertical Structure of the Effective Aerosol Complex Index of Refraction from a Combination of Aerosol in Situ and Remote Sensing Measurements During TARFOX

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Turco, R. P.; Liou, K. N.; Russell, P. B.; Bergstrom, R. W.; Schmid, B.; Livingston, J. M.; Hobbs, P. V.; Hartley, W. S.; Ismail, S.

    2000-01-01

    The largest uncertainty in estimates of the effects of atmospheric aerosols on climate stems from uncertainties in the determination of their microphysical properties, including the aerosol complex index of refraction, which in turn determines their optical properties. A novel technique is used to estimate the aerosol complex index of refraction in distinct vertical layers from a combination of aerosol in situ size distribution and remote sensing measurements during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX). In particular, aerosol backscatter measurements using the NASA Langley LASE (Lidar Atmospheric Sensing Experiment) instrument and in situ aerosol size distribution data are utilized to derive vertical profiles of the 'effective' aerosol complex index of refraction at 815 nm (i.e., the refractive index that would provide the same backscatter signal in a forward calculation on the basis of the measured in situ particle size distributions for homogeneous, spherical aerosols). A sensitivity study shows that this method yields small errors in the retrieved aerosol refractive indices, provided the errors in the lidar derived aerosol backscatter are less than 30% and random in nature. Absolute errors in the estimated aerosol refractive indices are generally less than 0.04 for the real part and can be as much as 0.042 for the imaginary part in the case of a 30% error in the lidar-derived aerosol backscatter. The measurements of aerosol optical depth from the NASA Ames Airborne Tracking Sunphotometer (AATS-6) are successfully incorporated into the new technique and help constrain the retrieved aerosol refractive indices. An application of the technique to two TARFOX case studies yields the occurrence of vertical layers of distinct aerosol refractive indices. Values of the estimated complex aerosol refractive index range from 1.33 to 1.45 for the real part and 0.001 to 0.008 for the imaginary part. The methodology devised in this study provides, for the first time a complete set of vertically resolved aerosol size distribution and refractive index data, yielding the vertical distribution of aerosol optical properties required for the determination of aersol-induced radiative flux changes

  13. Retrieving the vertical structure of the effective aerosol complex index of refraction from a combination of aerosol in situ and remote sensing measurements during TARFOX

    NASA Astrophysics Data System (ADS)

    Redemann, J.; Turco, R. P.; Liou, K. N.; Russell, P. B.; Bergstrom, R. W.; Schmid, B.; Livingston, J. M.; Hobbs, P. V.; Hartley, W. S.; Ismail, S.; Ferrare, R. A.; Browell, E. V.

    2000-04-01

    The largest uncertainty in estimates of the effects of atmospheric aerosols on climate stems from uncertainties in the determination of their microphysical properties, including the aerosol complex index of refraction, which in turn determines their optical properties. A novel technique is used to estimate the aerosol complex index of refraction in distinct vertical layers from a combination of aerosol in situ size distribution and remote sensing measurements during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX). In particular, aerosol backscatter measurements using the NASA Langley LASE (Lidar Atmospheric Sensing Experiment) instrument and in situ aerosol size distribution data are utilized to derive vertical profiles of the "effective" aerosol complex index of refraction at 815 nm (i.e., the refractive index that would provide the same backscatter signal in a forward calculation on the basis of the measured in situ particle size distributions for homogeneous, spherical aerosols). A sensitivity study shows that this method yields small errors in the retrieved aerosol refractive indices, provided the errors in the lidar-derived aerosol backscatter are less than 30% and random in nature. Absolute errors in the estimated aerosol refractive indices are generally less than 0.04 for the real part and can be as much as 0.042 for the imaginary part in the case of a 30% error in the lidar-derived aerosol backscatter. The measurements of aerosol optical depth from the NASA Ames Airborne Tracking Sunphotometer (AATS-6) are successfully incorporated into the new technique and help constrain the retrieved aerosol refractive indices. An application of the technique to two TARFOX case studies yields the occurrence of vertical layers of distinct aerosol refractive indices. Values of the estimated complex aerosol refractive index range from 1.33 to 1.45 for the real part and 0.001 to 0.008 for the imaginary part. The methodology devised in this study provides, for the first time, a complete set of vertically resolved aerosol size distribution and refractive index data, yielding the vertical distribution of aerosol optical properties required for the determination of aerosol-induced radiative flux changes.

  14. Refractive index and solubility control of para-cymene solutions for index-matched fluid-structure interaction studies

    NASA Astrophysics Data System (ADS)

    Fort, Charles; Fu, Christopher D.; Weichselbaum, Noah A.; Bardet, Philippe M.

    2015-12-01

    To deploy optical diagnostics such as particle image velocimetry or planar laser-induced fluorescence (PLIF) in complex geometries, it is beneficial to use index-matched facilities. A binary mixture of para-cymene and cinnamaldehyde provides a viable option for matching the refractive index of acrylic, a common material for scaled models and test sections. This fluid is particularly appropriate for large-scale facilities and when a low-density and low-viscosity fluid is sought, such as in fluid-structure interaction studies. This binary solution has relatively low kinematic viscosity and density; its use enables the experimentalist to select operating temperature and to increase fluorescence signal in PLIF experiments. Measurements of spectral and temperature dependence of refractive index, density, and kinematic viscosity are reported. The effect of the binary mixture on solubility control of Rhodamine 6G is also characterized.

  15. A simple reflection-type two-dimensional refractive index profile measurement technique for optical waveguides

    NASA Astrophysics Data System (ADS)

    Youk, Youngchun; Kim, Dug Young

    2006-06-01

    We report a new configuration of a reflection-type confocal scanning optical microscope system for measuring the refractive index profile of an optical waveguide. Several improvements on the earlier design are proposed; a light emitting diode at 650 nm wavelength instead of a laser diode or He-Ne laser is used as a light source for better index precision, and a simple longitudinal linear scanning and a curve fitting techniques are adapted instead of a servo control for maintaining an optical confocal arrangement. We have obtained spatial resolution of 800 nm and an index precision of 2 × 10-4. To verify the system's capability, the refractive index profiles of a conventional multimode fiber and a home-made four-mode fiber were examined with our proposed measurement method.

  16. Phase Manipulating Refractive Index form Positive to Negative in a Four-level Atomic System

    NASA Astrophysics Data System (ADS)

    Zhang, Hongjun

    2012-10-01

    We propose a four-level loop atomic scheme based on quantum coherence. Electric and magnetic responses of the medium to the probe field are discussed by taking into account the relative phase of the applied fields. It is shown that a change of the refractive index from positive to negative can occur by modulating the relative phase of the applied fields under suitable conditions. Then the medium can be switched from positive-index material to negative-index material or vice verse. In addition, a negative index material can be realized in different frequency regions by adjusting the relative phase.

  17. Extraordinary refractive-index increase in lithium niobate caused by low-dose ion implantation.

    PubMed

    Hu, H; Lu, F; Chen, F; Shi, B R; Wang, K M; Shen, D Y

    2001-08-01

    Multienergy Cu(+) ions with total dose of ~10(14) ions/cm(2) were implanted into LiNbO(3) crystals to form a nearly homogenous damage profile from the sample surface to the end of the ions' track. The extraordinary refractive-index enhancement was found in the damage region by observation of the dark mode. The extraordinary index showed an increasing trend until the ion dose reached a critical value. The largest index enhancement was ~0.0132. By use of low-dose ion implantation, we determined that the decreased spontaneous polarization caused the extraordinary index increase. PMID:18360410

  18. Relationship between the Kramers-Kronig relations and negative index of refraction

    SciTech Connect

    Akyurtlu, Alkim; Kussow, Adil-Gerai

    2010-11-15

    The condition for a negative index of refraction with respect to the vacuum index is established in terms of permittivity and permeability susceptibilities. It is found that the imposition of analyticity to satisfy the Kramers-Kronig relations is a sufficiently general criterion for a physical negative index. The satisfaction of the Kramers-Kronig relations is a manifestation of the principle of causality and the predicted frequency region of negative index agrees with the Depine-Lakhtakia condition for the phase velocity being antidirected to the Poynting vector, although the conditions presented here do not assume a priori a negative solution branch for n.

  19. Refractive index sensor based on etched D-fibres with wavelength adjustable operating point and resolution

    NASA Astrophysics Data System (ADS)

    Chandani, Sameer M.; Jaeger, Nicolas A. F.

    2008-06-01

    Silica based fibre-optic refractive index sensors are gaining acceptance over conventional refractometers and finding applications in chemical/biological sensing due to many of their desirable properties. Here we present an optical fibre-based refractive index sensor that uses the power transmission through etched D-shaped fibres. The sensor's operating point and resolution can be tailored for a specific application by selecting the correct combination of the operating wavelength and the cladding thickness of the etched fibre. The sensor's power transmission depends on the surrounding refractive index in which the sensor head is immersed. The sensor presented has a maximum resolution on the order of 10-6 in its "high resolution" region and on the order of 10-4 in its "low resolution" region. The refractive index at which the maximum resolution occurs in the high resolution region can be shifted by ~0.012 and by ~0.027 in the low resolution region. To date, such high resolutions have been reported over narrow ranges and/or for fibre Bragg grating based sensors, which require optical spectral analysis which typically, is costly.

  20. Enhanced refractive index without absorption via both coherent and incoherent fields in a semiconductor quantum well

    NASA Astrophysics Data System (ADS)

    Qian, Biqi; Wang, Zhiping; Shui, Tao; Yu, Benli

    2015-06-01

    We investigate the absorptive-dispersive properties of a weak probe field in a ladder-type semiconductor quantum well. It is found that the enhanced positive or negative refraction index without absorption can be easily obtained in this solid-state system. Our scheme may provide some new possibilities for technological applications in solid-state optical communication.

  1. Optical coherence tomography imaging of microfluidic pattern with different refractive index contrast

    NASA Astrophysics Data System (ADS)

    Hu, Zhixiong; Hao, Bingtao; Liu, Wenli; Hong, Baoyu

    2014-11-01

    Optical coherence tomography (OCT) technology is analogous to ultrasound imaging, except that OCT employs light instead of sound. The non-invasive imaging method works by projecting light on test target and detecting the backscattering from the underlying layers. As the OCT technology is based on optical interference, the internal structural features and inhomogeneities induced by different refractive index contrast could be detected and displayed in the form of a gray scale or false color image. In this paper, a typical microfluidic device was produced and measured by a spectral domain OCT instrument. The internal dimensions of the lab-on-chip device were determined using the OCT imaging technology and were in agreement with results obtained with conventional confocal microscope. In order to study the effect of different refractive index contrast on OCT imaging, fluid with various refractive indexes was injected into the microfluidic channel respectively, and the acquired OCT images of the internal microfluidic channel were compared. The results demonstrate that optical coherence tomography could be used as a new metrology tool to determine the internal channel dimensions of lab-on-chip devices. Furthermore, the experiment results reveal the relations between the refractive index contrast and OCT image quality.

  2. Effect of scintillometer height on structure parameter of the refractive index of air measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Scintillometers measure amount of scintillations by emitting a beam of light over a horizontal path and expresses as the atmospheric turbulence structure parameter as the refractive index of air (Cn**2). Cn**2 represents the turbulent strength of the atmosphere and describes the ability of the atmos...

  3. Variable Refractive Index Effects on Radiation in Semitransparent Scattering Multilayered Regions

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1993-01-01

    A simple set of equations is derived for predicting the temperature distribution and radiative energy flow in a semitransparent layer consisting of an arbitrary number of laminated sublayers that absorb, emit, and scatter radiation. Each sublayer can have a different refractive index and optical thickness. The plane composite region is heated on each exterior side by a different amount of incident radiation. The results are for the limiting case where heat conduction within the layers is very small relative to radiative transfer, and is neglected. The interfaces are assumed diffuse, and all interface reflections are included in the analysis. The thermal behavior is readily calculated from the analytical expressions that are obtained. By using many sublayers, the analytical expressions provide the temperature distribution and heat flow for a diffusing medium with a continuously varying refractive index, including internal reflection effects caused by refractive index gradients. Temperature and heat flux results are given to show the effect of variations in refractive index and optical thickness through the multilayer laminate.

  4. Single tapered fiber tip for simultaneous measurements of thickness, refractive index and distance to a sample.

    PubMed

    Moreno-Hernández, Carlos; Monzón-Hernández, David; Hernández-Romano, Iván; Villatoro, Joel

    2015-08-24

    We demonstrate the capability of an air cavity Fabry-Perot interferometer (FPI), built with a tapered lead-in fiber tip, to measure three parameters simultaneously, distance, group refractive index and thickness of transparent samples introduced in the cavity. Tapering the lead-in fiber enhances the light coupling back efficiency, therefore is possible to enlarge the air cavity without a significant deterioration of the fringe visibility. Fourier transformation, used to analyze the reflected optical spectrum of our FPI, simplify the calculus to determine the position, thickness and refractive index. Samples made of 7 different glasses; fused silica, BK7, BalF5, SF2, BaF51, SF15, and glass slides were used to test our FPI. Each sample was measured nine times and the results for position, thickness and refractive index showed differences of ± 0.7%, ± 0.1%, and ± 0.16% respectively. The evolution of thickness and refractive index of a block of polydimethylsiloxane (PDMS) elastomer due to temperature changes in the range of 25°C to 90°C were also measured. The coefficients of the thermal expansion and thermo-optic estimated were α = 4.71x10(-4)/°C and dn/dT = -4.66 x10(-4) RIU/°C, respectively. PMID:26368188

  5. Low-cost refractive index and strain sensor based on tapered fibers

    NASA Astrophysics Data System (ADS)

    Mas, Sara; Mart, Javier; Monzn-Hernndez, David; Palac, Jess

    2016-02-01

    In this paper, biconical tapered fibers are used to carry out sensing in a simple and effective way by using an incoherent source and a power meter. This approach reduces the cost and complexity of traditional schemes based on tunable lasers while providing similar performance. Refractive index and strain sensing measurements are presented and their performance discussed.

  6. Manipulating intracellular refractive index for contrast-enhanced digital holographic imaging of subcellular structures

    NASA Astrophysics Data System (ADS)

    Rommel, Christina E.; Dierker, Christian; Schmidt, Lisa; Przibilla, Sabine; von Bally, Gert; Kemper, Björn; Schnekenburger, Jürgen

    2011-02-01

    The online analysis of rapid cellular processes by morphological alterations strongly depends on the ability to rapidly visualize and to quantify cell shape and intracellular structures. Digital holographic microscopy (DHM) enables quantitative phase contrast imaging for high resolution and minimal invasive live cell analysis without the need of labeling or complex sample preparation. However, due to the rather homogenous intracellular refractive index, the phase contrast of subcellular structures is limited and often low. We analyzed the impact of specific intracellular refractive index manipulation by microinjection of refractive index changing agents on the DHM phase contrast. Glycerol was chosen as osmolyte, which combines high solubility in aqueous solutions and cellular compatibility. We present data showing that the intracellular injection of glycerol causes a contrast enhancement that can be explained by a decrease of the cytosolic refractive index due to a water influx. The underlying principle was proven by experiments inducing cell shrinkage and protein concentration. The integrity of cell membranes is considered as a prerequisite and allows a reversible cell swelling and shrinking within a certain limit. The presented approach to control the intracellular phase contrast demonstrated for DHM opens also prospects for application with other quantitative phase contrast imaging technologies.

  7. Glasses having a low non-linear refractive index for laser applications

    DOEpatents

    Faulstich, Marga (Mainz, DE); Jahn, Walter (Ingelheim, DE); Krolla, Georg (Mainz, DE); Neuroth, Norbert (Mainz-Mombach, DE)

    1980-01-01

    Glass composition ranges are described which permit the introduction of laser activators into fluorphosphate glass with exceptionally high fluorine content while forming glasses of high crystallization stability and permitting the realization of large melt volumes. The high fluorine content imparts to the glasses an exceptionally low nonlinear refractive index n.sub.2 down to O,4 .times.10.sup.-13 esu.

  8. Integrating Whispering Gallery Mode Refractive Index Sensing with Capillary Electrophoresis Separations Using Phase Sensitive Detection.

    PubMed

    Kim, Daniel C; Dunn, Robert C

    2016-01-19

    Whispering gallery mode (WGM) resonators are small, radially symmetric dielectrics that recirculate light through continuous total internal reflection. High-Q resonances are observed that shift in response to changes in surrounding refractive index, leading to many applications in label-free sensing. Surface binding measurements with WGM resonators have demonstrated competitive analytical detection metrics compared to other sensing schemes. Similar figures of merit for detecting bulk refractive index changes, however, have proven more challenging. This has limited their use in applications such as capillary electrophoresis (CE), where their compact footprint and refractive index sensitivity offers advantages in nondestructive, universal detection. Here we couple WGM detection with CE by introducing a modulation scheme to improve detection limits. Phase sensitive WGM (PS-WGM) detection is developed to monitor real-time shifts in the WGM spectrum due to changes in surrounding refractive index. We directly compare phase sensitive detection with spectral measurements normally used to track WGM shifts. We report an improvement in detection limits by almost 300-fold using the PS-WGM method. The integrated CE with PS-WGM approach is demonstrated by detecting the separation of a three-component mixture of cations (Na(+), Li(+), and K(+)). PMID:26651379

  9. Measuring the Refractive Index of Highly Crystalline Monolayer MoS2 with High Confidence

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Ma, Yaoguang; Wan, Yi; Rong, Xin; Xie, Ziang; Wang, Wei; Dai, Lun

    2015-02-01

    Monolayer molybdenum disulphide (MoS2) has attracted much attention, due to its attractive properties, such as two-dimensional properties, direct bandgap, valley-selective circular dichroism, and valley Hall effect. However, some of its fundamental physical parameters, e.g. refractive index, have not been studied in detail because of measurement difficulties. In this work, we have synthesized highly crystalline monolayer MoS2 on SiO2/Si substrates via chemical vapor deposition (CVD) method and devised a method to measure their optical contrast spectra. Using these contrast spectra, we extracted the complex refractive index spectrum of monolayer MoS2 in the wavelength range of 400 nm to 750 nm. We have analyzed the pronounced difference between the obtained complex refractive index spectrum and that of bulk MoS2. The method presented here is effective for two-dimensional materials of small size. Furthermore, we have calculated the color contour plots of the contrast as a function of both SiO2 thickness and incident light wavelength for monolayer MoS2 using the obtained refractive index spectrum. These plots are useful for both fundamental study and device application.

  10. Measuring the refractive index of highly crystalline monolayer MoS2 with high confidence.

    PubMed

    Zhang, Hui; Ma, Yaoguang; Wan, Yi; Rong, Xin; Xie, Ziang; Wang, Wei; Dai, Lun

    2015-01-01

    Monolayer molybdenum disulphide (MoS2) has attracted much attention, due to its attractive properties, such as two-dimensional properties, direct bandgap, valley-selective circular dichroism, and valley Hall effect. However, some of its fundamental physical parameters, e.g. refractive index, have not been studied in detail because of measurement difficulties. In this work, we have synthesized highly crystalline monolayer MoS2 on SiO2/Si substrates via chemical vapor deposition (CVD) method and devised a method to measure their optical contrast spectra. Using these contrast spectra, we extracted the complex refractive index spectrum of monolayer MoS2 in the wavelength range of 400 nm to 750 nm. We have analyzed the pronounced difference between the obtained complex refractive index spectrum and that of bulk MoS2. The method presented here is effective for two-dimensional materials of small size. Furthermore, we have calculated the color contour plots of the contrast as a function of both SiO2 thickness and incident light wavelength for monolayer MoS2 using the obtained refractive index spectrum. These plots are useful for both fundamental study and device application. PMID:25676089

  11. Measuring the Refractive Index of Highly Crystalline Monolayer MoS2 with High Confidence

    PubMed Central

    Zhang, Hui; Ma, Yaoguang; Wan, Yi; Rong, Xin; Xie, Ziang; Wang, Wei; Dai, Lun

    2015-01-01

    Monolayer molybdenum disulphide (MoS2) has attracted much attention, due to its attractive properties, such as two-dimensional properties, direct bandgap, valley-selective circular dichroism, and valley Hall effect. However, some of its fundamental physical parameters, e.g. refractive index, have not been studied in detail because of measurement difficulties. In this work, we have synthesized highly crystalline monolayer MoS2 on SiO2/Si substrates via chemical vapor deposition (CVD) method and devised a method to measure their optical contrast spectra. Using these contrast spectra, we extracted the complex refractive index spectrum of monolayer MoS2 in the wavelength range of 400?nm to 750?nm. We have analyzed the pronounced difference between the obtained complex refractive index spectrum and that of bulk MoS2. The method presented here is effective for two-dimensional materials of small size. Furthermore, we have calculated the color contour plots of the contrast as a function of both SiO2 thickness and incident light wavelength for monolayer MoS2 using the obtained refractive index spectrum. These plots are useful for both fundamental study and device application. PMID:25676089

  12. Ultraviolet complex refractive index of Martian dust Laboratory measurements of terrestrial analogs

    NASA Technical Reports Server (NTRS)

    Egan, W. G.; Hilgeman, T.; Pang, K.

    1975-01-01

    The optical complex index of refraction of four candidate Martian surface materials has been determined between 0.185 and 0.4 microns using a modified Kubelka-Munk scattering theory. The cadidate materials were limonite, andesite, montmorillonite, and basalt. The effect of scattering has been removed from the results. Also presented are diffuse reflection and transmission data on these samples.

  13. Time-resolved refractive index and absorption mapping of light-plasma filaments in water.

    PubMed

    Minardi, Stefano; Gopal, Amrutha; Tatarakis, Michael; Couairon, Arnaud; Tamosauskas, Gintaras; Piskarskas, Rimtautas; Dubietis, Audrius; Di Trapani, Paolo

    2008-01-01

    By means of a quantitative shadowgraphic method, we performed a space-time characterization of the refractive index variation and transient absorption induced by a light-plasma filament generated by a 120 fs laser pulse in water. The formation and evolution of the plasma channel in the proximity of the nonlinear focus were observed with a 23 fs time resolution. PMID:18157267

  14. Analytical Modelling of a Refractive Index Sensor Based on an Intrinsic Micro Fabry-Perot Interferometer

    PubMed Central

    Vargas-Rodriguez, Everardo; Guzman-Chavez, Ana D.; Cano-Contreras, Martin; Gallegos-Arellano, Eloisa; Jauregui-Vazquez, Daniel; Hernández-García, Juan C.; Estudillo-Ayala, Julian M.; Rojas-Laguna, Roberto

    2015-01-01

    In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10−4 RIU can be implemented by using a couple of standard and low cost photodetectors. PMID:26501277

  15. Unusual fault detection and loss analysis in optical fiber connections with refractive index matching material

    NASA Astrophysics Data System (ADS)

    Kihara, Mitsuru; Nagano, Ryuichiro; Izumita, Hisashi; Toyonaga, Masanobu

    2012-05-01

    We investigated and analyzed an unusual fault that occurs in optical access fiber networks, which is caused by a defective fiber connection. We developed a fault-detection system to locate such a fault by using both optical power level and optical pulse measurement methods. We investigated a defective mechanical splice in three laboratory tests: outward appearance, non-destructive, and dismantled. As a result, we confirmed that the defective mechanical splice had large gaps of more than 10 ?m. We also analyzed the unusual fault that occurs from such a defective mechanical splice in mechanically transferrable (MT) connector experiments. The experimental results revealed that the optical performance of fiber connections with a mixture of refractive index matching material and air-filled gaps was extremely unstable and varied widely. In the worst case, the insertion loss worsened to more than 30 dB. The case of the fault caused by a mixture of refractive index matching material and air-filled gaps between the ends of optical fibers is thought to occur independently of the sorts or structures of optical fiber connectors and could be a characteristic peculiar to optical fiber connections using refractive index matching material. These findings can be applied to optical fiber connections that use refractive index matching material, such as MT connectors in outside underground facilities, mechanical splices, or field assembly connectors at aerial and home sites in optical access networks. These findings also support the practical construction and operation of optical network systems.

  16. Chiral metamaterials with negative refractive index based on four U split ring resonators

    SciTech Connect

    Li, Zhaofeng; Zhao, Rongkuo; Koschny, Thomas; Kafesaki, Maria; Alici, Kamil Boratay; Colak, Evrim; Caglayan, Humeyra; Ozbay, Ekmel; Soukoulis, C.M.

    2010-08-23

    A uniaxial chiral metamaterial is constructed by double-layered four 'U' split ring resonators mutually twisted by 90{sup o}. It shows a giant optical activity and circular dichroism. The retrieval results reveal that a negative refractive index is realized for circularly polarized waves due to the large chirality. The experimental results are in good agreement with the numerical results.

  17. The refractive index of krypton for lambda in the closed interval 168-288 nm

    NASA Technical Reports Server (NTRS)

    Smith, P. L.; Parkinson, W. H.; Huber, M. C. E.

    1975-01-01

    The index of refraction of krypton has been measured at 27 wavelengths between and including 168 and 288 nm. The probable error of each measurement is plus or minus 0.1%. Our results are compared with other measurements. Our data are about 3.8% smaller than those of Abjean et al.

  18. Analytical modelling of a refractive index sensor based on an intrinsic micro Fabry-Perot interferometer.

    PubMed

    Vargas-Rodriguez, Everardo; Guzman-Chavez, Ana D; Cano-Contreras, Martin; Gallegos-Arellano, Eloisa; Jauregui-Vazquez, Daniel; Hernández-García, Juan C; Estudillo-Ayala, Julian M; Rojas-Laguna, Roberto

    2015-01-01

    In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10(-4) RIU can be implemented by using a couple of standard and low cost photodetectors. PMID:26501277

  19. Anisotropic refractive-index change in silica glass induced by self-trapped filament of linearly polarized femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Yamada, Kazuhiro; Watanabe, Wataru; Nishii, Junji; Itoh, Kazuyoshi

    2003-02-01

    Permanent refractive-index change can be induced by a self-trapped filament of intense ultrashort laser pulses in silica glass. We investigated the dependence of refractive-index change on polarization of incident laser pulses. As the region of refractive-index change can be selectively etched by hydrofluoric acid (HF), we first polished the sample and etched the cross section of the regions. The HF-etched cross section of refractive-index change that was induced by linearly polarized pulses was seen to be elliptical when observed with a scanning-electron microscope. By polarimetric analysis of diffraction from gratings fabricated by polarized ultrashort laser pulses, the index ellipsoid of refractive-index change was confirmed to be uniaxial and negative.

  20. Monitoring of high refractive index edible oils using coated long period fiber grating sensors

    NASA Astrophysics Data System (ADS)

    Coelho, Luís.; Viegas, Diana; Santos, José Luís.; de Almeida, Jose Manuel M. M.

    2015-05-01

    Monitoring the quality of high refractive index edible oils is of great importance for the human health. Uncooked edible oils in general are healthy foodstuff, olive oil in particular, however, they are frequently used for baking and cooking. High quality edible oils are made from seeds, nuts or fruits by mechanical processes. Nevertheless, once the mechanical extraction is complete, up to 15% of the oil remains in oil pomace and in the mill wastewater, which can be extracted using organic solvents, often hexane. Optical fiber sensors based on long period fiber gratings (LPFG) have very low wavelength sensitivity when the surround refractive index is higher than the refractive index of the cladding. Titanium dioxide (TiO2) coated LPFG could lead to the realization of high sensitivity chemical sensor for the food industry. In this work LPFG coated with a TiO2 thin film were successfully used for to detect small levels of hexane diluted in edible oils and for real time monitoring the thermal deterioration of edible oils. For a TiO2 coating of 30 nm a wavelength sensitivity of 1361.7 nm/RIU (or 0.97 nm / % V/V) in the 1.4610-1.4670 refractive index range was achieved, corresponding to 0 to 12 % V/V of hexane in olive oil. A sensitivity higher than 638 nm/RIU at 225 ºC was calculated, in the 1.4670-1.4735 refractive index range with a detection limit of thermal deterioration of about 1 minute.

  1. Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection.

    PubMed

    Zhang, Jiwei; Di, Jianglei; Li, Ying; Xi, Teli; Zhao, Jianlin

    2015-10-19

    We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes. PMID:26480394

  2. Error Budget for a Calibration Demonstration System for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

    2013-01-01

    A goal of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission is to observe highaccuracy, long-term climate change trends over decadal time scales. The key to such a goal is to improving the accuracy of SI traceable absolute calibration across infrared and reflected solar wavelengths allowing climate change to be separated from the limit of natural variability. The advances required to reach on-orbit absolute accuracy to allow climate change observations to survive data gaps exist at NIST in the laboratory, but still need demonstration that the advances can move successfully from to NASA and/or instrument vendor capabilities for spaceborne instruments. The current work describes the radiometric calibration error budget for the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. The goal of the CDS is to allow the testing and evaluation of calibration approaches, alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. The resulting SI-traceable error budget for reflectance retrieval using solar irradiance as a reference and methods for laboratory-based, absolute calibration suitable for climatequality data collections is given. Key components in the error budget are geometry differences between the solar and earth views, knowledge of attenuator behavior when viewing the sun, and sensor behavior such as detector linearity and noise behavior. Methods for demonstrating this error budget are also presented.

  3. Natural media with negative index of refraction: Perspectives of complex transition metal oxides (Review Article)

    NASA Astrophysics Data System (ADS)

    Fertman, E. L.; Beznosov, A. B.

    2011-07-01

    The capabilities of perovskite-like compounds with the effect of colossal magnetoresistance (CMR) and some other complex oxides to have a negative index of refraction (NIR) are considered. Physical properties of these compounds are also analyzed from the standpoint of designing tunable metamaterials on their base. Of particular interest are temperature and magnetic field driven first-order transformations in oxides with perovskite structure and in spinels. These transformations give rise to nanophase separated states, using which the properties of negative refraction can be affected. The magnetic-field controlled metamaterials with CMR oxides as a boundary NIR media for a photonic crystal are discussed.

  4. The structure of the QL and QT approximations to the plasma refractive index

    NASA Astrophysics Data System (ADS)

    Heading, J.

    1989-10-01

    The quasi-longitudinal and quasi-transverse approximations to the Appleton-Lassen refractive index formula for a homogeneous magnetoionic medium have been known and used for over half a century. An investigation is made so as to discover why these formulas take their particular forms. To this end, the basic propagation equations are generalized to n dimensions, and the corresponding refractive indices and their various aproximations are examined in their generality. A ladder of such formulas is produced, with the three-dimensional case sitting at its lowest rung.

  5. Raman spectroscopic investigation on high refractive index glasses prepared from local quartz sand.

    PubMed

    Dararutana, P; Pongkrapan, S; Sirikulrat, N; Thawornmongkolkij, M; Wathanakul, P

    2009-08-01

    High refractive index (RI) glasses prepared from local quartz sand and compounds of heavy elements, such as, barium carbonate, lead oxide, and bismuth oxide as major ingredients were investigated using Raman spectroscopy. The results showed changes in glass structures of different doping elements, namely, Ba, Pb, and Bi. Refractive indices, densities, and UV-vis-NIR spectra of the glass samples were also measured. The Raman spectroscopy can be used to investigate and/or identify heavy glasses, local ancient glasses as well as glass jewelry. PMID:19081291

  6. Raman spectroscopic investigation on high refractive index glasses prepared from local quartz sand

    NASA Astrophysics Data System (ADS)

    Dararutana, P.; Pongkrapan, S.; Sirikulrat, N.; Thawornmongkolkij, M.; Wathanakul, P.

    2009-08-01

    High refractive index (RI) glasses prepared from local quartz sand and compounds of heavy elements, such as, barium carbonate, lead oxide, and bismuth oxide as major ingredients were investigated using Raman spectroscopy. The results showed changes in glass structures of different doping elements, namely, Ba, Pb, and Bi. Refractive indices, densities, and UV-vis-NIR spectra of the glass samples were also measured. The Raman spectroscopy can be used to investigate and/or identify heavy glasses, local ancient glasses as well as glass jewelry.

  7. Lens-free inline holographic microscopy with numerical correction of layers with different refractive index.

    PubMed

    Kanka, Mario; Riesenberg, Rainer

    2015-03-01

    Digital inline holographic microscopy is applied for lens-free imaging with high lateral resolution. Microfluidic chambers for the imaging of cells in water-like or native solutions, e.g., thick layers of glass and other materials with different refractive index, cause aberrations that limit the spatial resolution and change the magnification scale. In this Letter, a fast reconstruction technique considering parallel layer systems of different refractive indices is presented. In the experiments, properly scaled images of microbeads and red human blood cells with an optical resolution corresponding to a numerical aperture of about 0.62 were reconstructed. PMID:25723424

  8. Effective refractive index of a quasi-two-dimensional polydomain film of a conjugated polymer

    NASA Astrophysics Data System (ADS)

    Aver'yanov, E. M.

    2016-01-01

    The relation between the effective ordinary refractive index n* = ( n o n e )1/2 of a quasi-two-dimensional polydomain uniaxial film of a conjugated polymer F8BT in the visible transparency region and the refractive indices ( n o,e ) of uniaxial domains with the optical axes randomly oriented in the plane of the film has been confirmed experimentally. The permissible interval of variations in n* has been established and a strong spectral dispersion of this interval near the long-wavelength electronic absorption band of the film has been demonstrated.

  9. An ultracompact refractive index gas-sensor based on photonic crystal microcavity

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoling; Lu, Naiguang; Zhu, Jun; Jin, Guofan

    2008-03-01

    An ultracompact gas-sensor based on the two-dimensional photonic crystal microcavity is presented. The sensor is formed by a point-defect resonant cavity. The transmission spectrums of the sensor with different ambient refractive indices ranging from 1.0 n = to 1.01 n = are calculated. The calculation results show that a change in ambient refractive index of ?n=110 -4is apparent, the sensitivity of the sensor (??/?n) is achieved with 433nm/RIU(when lattice constant 520 a=520nm), where RIU means refractive index unit . The properties of the sensor are analyzed and calculated using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method. Using the fabry-Perot cavity mode, the performances of the refractive index sensor are analyzed theoretically. The sensor is optimized using the photonic crystal waveguide structure and simulated using the FDTD method. As the small sensing area (~10?m2) of the device would require only ~1fL sample analyte, these ultracompact gas sensors would be widely used in little sample analyte in gas measurement.

  10. A two-dimensional uniplanar transmission-line metamaterial with a negative index of refraction

    NASA Astrophysics Data System (ADS)

    Elek, Francis; Eleftheriades, George V.

    2005-08-01

    A uniplanar transmission-line (TL) network has been loaded with lumped elements (chip or printed), enabling one to achieve a two-dimensional (2D) uniplanar negative-refractive-index (NRI) metamaterial. The metamaterial consists of a 2D array of unit cells, composed of TL sections connected in series and loaded in a specified manner. The unit cell dimensions can be designed to be much smaller than the operating wavelength, enabling one to identify the structure as an effective medium, with a negative index of refraction. This NRI metamaterial supports transverse electric (TE) waves, as opposed to related previous work on NRI-TL media that supported transverse magnetic (TM) waves. The dispersion characteristics are calculated using a simple, fast 2D loaded TL model with periodic (Bloch) boundary conditions. Subsequently the dispersion relation is simplified in the homogeneous limit, thus allowing one to identify effective permittivities and permeabilities, which are shown to be simultaneously negative. Simulations demonstrating the negative refraction of a plane wave on an interface between such a NRI uniplanar metamaterial and a commensurate positive-refractive-index (PRI) metamaterial verify the validity of the proposed concept and theory. A fully printed unit cell is presented at microwave frequencies (~10 GHz) along with a prescription for synthesizing an isotropic 3D transmission line NRI metamaterial based on this unit cell.

  11. A Multi-D-Shaped Optical Fiber for Refractive Index Sensing

    PubMed Central

    Chen, Chien-Hsing; Tsao, Tzu-Chein; Tang, Jaw-Luen; Wu, Wei-Te

    2010-01-01

    A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated could range from three to seven. Each D-shaped zone covered a sensor volume of 100 ?m depth, 250 ?m width, and 1 mm length. The mean roughness of the core surface obtained by the AFM images was 231.7 nm, which is relatively smooth. Results of the tensile test indicated that the fibers have sufficient mechanical strength to resist damage from further processing. The multi-D-shaped optical fiber as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results for different concentrations of sucrose solution show that a resolution of 1.27 10?33.13 10?4 RIU is achieved for refractive indices in the range of 1.333 to 1.403, suggesting that the multi-D-shaped fibers are attractive for chemical, biological, and biochemical sensing with aqueous solutions. PMID:22399908

  12. Temperature-Dependent Refractive Index Measurements of Caf2, Suprasil 3001, and S-FTM16 for the Euclid Near Infrared Spectrometer and Photometer

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Grupp, Frank D.

    2015-01-01

    Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we measured absolute refractive indices at temperatures from 100 to 310 K at wavelengths from 0.42 to 3.6 microns for CaF2, Suprasil 3001 fused silica, and S-FTM16 glass in support of lens designs for the Near Infrared Spectrometer and Photometer (NISP) for ESA's Euclid dark energy mission. We report absolute refractive index, dispersion (dn/d?), and thermo-optic coefficient (dn/dT) for these materials. In this study, materials from different melts were procured to understand index variability in each material. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. For calcium fluoride (CaF2) and S-FTM16, we compare our current measurements with CHARMS measurements of these materials made in the recent past for other programs. We also compare Suprasil 3001's indices to those of other forms of fused silica we have measured in CHARMS.

  13. Temperature-dependent refractive index measurements of CaF2, Suprasil 3001, and S-FTM16 for the Euclid near-infrared spectrometer and photometer

    NASA Astrophysics Data System (ADS)

    Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Grupp, Frank U.

    2015-09-01

    Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we measured absolute refractive indices at temperatures from 100 to 310 K at wavelengths from 0.42 to 3.6 microns for CaF2, Suprasil 3001 fused silica, and S-FTM16 glass in support of lens designs for the Near Infrared Spectrometer and Photometer (NISP) for ESA's Euclid dark energy mission. We report absolute refractive index, dispersion (dn/d?), and thermo-optic coefficient (dn/dT) for these materials. In this study, materials from different melts were procured to understand index variability in each material. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. For calcium fluoride (CaF2) and S-FTM16, we compare our current measurements with CHARMS measurements of these materials made in the recent past for other programs. We also compare Suprasil 3001's indices to those of other forms of fused silica we have measured in CHARMS.

  14. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals.

    PubMed

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-01-01

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals. PMID:26956377

  15. Extended IWKB method for determination of the refractive=index profile in optical waveguides.

    PubMed

    Shi, L P; Pun, E Y; Chung, P S

    1995-08-01

    A simple method is outlined for the calculation of the refractive-index profiles of both multimode and monomode planar optical waveguides. The method is an extension of the well-established IWKB method. The parameters required are the dispersion relation of the surface index changes and the effective indices at different wavelengths. As an example, the refractive-index profile of a monomode z-cut KTiOPO(4) planar waveguide fabricated by Rb(+):K(+) exchange is computed. Close agreement is obtained, indicating the practicality of this method. The method is also applicable to optical waveguides in other materials, such as LiNbO(3), LiTaO(3), and glass. PMID:19862103

  16. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals

    PubMed Central

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-01-01

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals. PMID:26956377

  17. 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.

  18. Prism-pair interferometer for precise measurement of the refractive index of optical glass by using a spectrum lamp.

    PubMed

    Hori, Yasuaki; Hirai, Akiko; Minoshima, Kaoru

    2014-05-01

    A prism-pair interferometer for a spectrum lamp was developed for precise measurement of the refractive index of a prism of optical glass. Previously we reported the prism-pair interferometer with a He-Ne laser light source, resulting in a measurement uncertainty of 1.110??. However, most of the refractive-index values managed by optical glass manufacturers are conventionally measured with spectrum lamps. We have optimized the prism-pair interferometer for spectrum lamps and implemented a signal-processing technique from Fourier-transform spectroscopy. When the refractive index is measured, the wavelength of the spectrum lamp is simultaneously calibrated by part of the interferometer, so that the resulting refractive index is traceable to a national standard of length. The combined standard uncertainty for a refractive index measured with the e-line (546 nm) of a Hg lamp is 6.910??. PMID:24921862

  19. Instrumentation and First Results of the Reflected Solar Demonstration System for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    McCorkel, Joel; Thome, Kurtis; Hair, Jason; McAndrew, Brendan; Jennings, Don; Rabin, Douglas; Daw, Adrian; Lundsford, Allen

    2012-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission key goals include enabling observation of high accuracy long-term climate change trends, use of these observations to test and improve climate forecasts, and calibration of operational and research sensors. The spaceborne instrument suites include a reflected solar spectroradiometer, emitted infrared spectroradiometer, and radio occultation receivers. The requirement for the RS instrument is that derived reflectance must be traceable to Sl standards with an absolute uncertainty of <0.3% and the error budget that achieves this requirement is described in previo1L5 work. This work describes the Solar/Lunar Absolute Reflectance Imaging Spectroradiometer (SOLARIS), a calibration demonstration system for RS instrument, and presents initial calibration and characterization methods and results. SOLARIS is an Offner spectrometer with two separate focal planes each with its own entrance aperture and grating covering spectral ranges of 320-640, 600-2300 nm over a full field-of-view of 10 degrees with 0.27 milliradian sampling. Results from laboratory measurements including use of integrating spheres, transfer radiometers and spectral standards combined with field-based solar and lunar acquisitions are presented. These results will be used to assess the accuracy and repeatability of the radiometric and spectral characteristics of SOLARIS, which will be presented against the sensor-level requirements addressed in the CLARREO RS instrument error budget.

  20. Nondestructive measurement of two-dimensional refractive index profiles by deflectometry

    NASA Astrophysics Data System (ADS)

    Lin, Di; Leger, James R.

    2015-06-01

    We present a method for calculating a two-dimensional refractive index field from measured boundary values of beam position and slope. By initially ignoring the dependence of beam trajectories on the index field and using cubic polynomials to approximate these trajectories, we show that the inverse problem can be reduced to set of linear algebraic equations and solved using a numerical algorithm suited for inverting sparse, ill-conditioned linear systems. The beam trajectories are subsequently corrected using an iterative ray trace procedure so that they are consistent with the ray equation inside the calculated index field. We demonstrate the efficacy of our method through computer simulation, where a hypothetical test index field is reconstructed on a 15 × 15 discrete grid using 800 interrogating rays and refractive index errors (RMS) less than 0.5% of the total index range (nmax-nmin) are achieved. In the subsequent error analysis, we identify three primary sources of error contributing to the reconstruction of the index field and assess the importance of data redundancy. The principles developed in our approach are fully extendable to three-dimensional index fields as well as more complex geometries.

  1. Improving Axial Resolution in Confocal Microscopy with New High Refractive Index Mounting Media

    PubMed Central

    Fouquet, Coralie; Gilles, Jean-François; Heck, Nicolas; Dos Santos, Marc; Schwartzmann, Richard; Cannaya, Vidjeacoumary; Morel, Marie-Pierre; Davidson, Robert Stephen; Trembleau, Alain; Bolte, Susanne

    2015-01-01

    Resolution, high signal intensity and elevated signal to noise ratio (SNR) are key issues for biologists who aim at studying the localisation of biological structures at the cellular and subcellular levels using confocal microscopy. The resolution required to separate sub-cellular biological structures is often near to the resolving power of the microscope. When optimally used, confocal microscopes may reach resolutions of 180 nm laterally and 500 nm axially, however, axial resolution in depth is often impaired by spherical aberration that may occur due to refractive index mismatches. Spherical aberration results in broadening of the point-spread function (PSF), a decrease in peak signal intensity when imaging in depth and a focal shift that leads to the distortion of the image along the z-axis and thus in a scaling error. In this study, we use the novel mounting medium CFM3 (Citifluor Ltd., UK) with a refractive index of 1.518 to minimize the effects of spherical aberration. This mounting medium is compatible with most common fluorochromes and fluorescent proteins. We compare its performance with established mounting media, harbouring refractive indices below 1.500, by estimating lateral and axial resolution with sub-resolution fluorescent beads. We show furthermore that the use of the high refractive index media renders the tissue transparent and improves considerably the axial resolution and imaging depth in immuno-labelled or fluorescent protein labelled fixed mouse brain tissue. We thus propose to use those novel high refractive index mounting media, whenever optimal axial resolution is required. PMID:25822785

  2. Refractive index of water and steam as function of wavelength, temperature and density

    NASA Astrophysics Data System (ADS)

    Schiebener, P.; Straub, J.; Levelt Sengers, J. M. H.; Gallagher, J. S.

    1990-05-01

    Based on a comprehensive collection of data previously obtained by Thormählen et al. on the experimental refractive index of water and steam from the 1870s to the present, a new formulation is presented for the range of 0.2 to 2.5 μm in wave-length, -10 to +500 °C in temperature and 0 to 1045 kg m-3 in density. The Lorentz-Lorentz function or molar refraction, a strong function of wavelength but only weakly dependent on density and temperature, is fitted to a selected set of accurate refractive index data. The NBS/NRC equation of state for water and steam, the new international standard, is used to convert the experimental pressures to density. The deviations of all experimental data from the formulation are shown. A detailed assessment of the accuracy of the formulation is presented. Although the formulation does not represent to within their accuracy the data from the best sets in the visible range for liquid water below the boiling point, we show that inconsistencies between data sets, and minor deficiencies of the equation of state, prevent further improvement of a formulation based on data over as wide a range as considered here. It is shown that the best refractive index data can be used to discriminate between the various formulations of the equation of state of water and steam. It is demonstrated that several recent formulations of optical properties of liquid water over large ranges of wavelength need improvement in the range covered here. The new formulation is used to generate tables of the refractive index of water and steam at six wavelengths in the visible, near-infrared and near-ultraviolet, from 0 to 500 °C and up to 100 MPa in pressure.

  3. Contribution of the gradient refractive index and shape to the crystalline lens spherical aberration and astigmatism.

    PubMed

    Birkenfeld, Judith; de Castro, Alberto; Ortiz, Sergio; Pascual, Daniel; Marcos, Susana

    2013-06-28

    The optical properties of the crystalline lens are determined by its shape and refractive index distribution. However, to date, those properties have not been measured together in the same lens, and therefore their relative contributions to optical aberrations are not fully understood. The shape, the optical path difference, and the focal length of ten porcine lenses (age around 6 months) were measured in vitro using Optical Coherence Tomography and laser ray tracing. The 3D Gradient Refractive Index distribution (GRIN) was reconstructed by means of an optimization method based on genetic algorithms. The optimization method searched for the parameters of a 4-variable GRIN model that best fits the distorted posterior surface of the lens in 18 different meridians. Spherical aberration and astigmatism of the lenses were estimated using computational ray tracing, with the reconstructed GRIN lens and an equivalent homogeneous refractive index. For all lenses the posterior radius of curvature was systematically steeper than the anterior one, and the conic constant of both the anterior and posterior positive surfaces was positive. In average, the measured focal length increased with increasing pupil diameter, consistent with a crystalline lens negative spherical aberration. The refractive index of nucleus and surface was reconstructed to an average value of 1.427 and 1.364, respectively, for 633 nm. The results of the GRIN reconstruction showed a wide distribution of the index in all lens samples. The GRIN shifted spherical aberration towards negative values when compared to a homogeneous index. A negative spherical aberration with GRIN was found in 8 of the 10 lenses. The presence of GRIN also produced a decrease in the total amount of lens astigmatism in most lenses, while the axis of astigmatism was only little influenced by the presence of GRIN. To our knowledge, this study is the first systematic experimental study of the relative contribution of geometry and GRIN to the aberrations in a mammal lens. PMID:23597582

  4. Single-Mode Refractive Index Reconstruction Using an NM-Line Technique

    NASA Astrophysics Data System (ADS)

    Monir, Michael; El-Refaei, Hatem; Khalil, Diaa

    A new technique for the measurement of single-mode planar waveguide refractive index profile is developed. This technique, based on the successive etching and effective index measurement, is applied on planar guides fabricated on a glass substrate using K+-Na+ ion exchange where the guide is etched using diluted HF acid and the mode effective index is measured by the well-known M-lines technique. The profile measured by this technique is assisted by modal calculations using a numerical mode solver and a strong agreement is obtained.

  5. Test Plan for a Calibration Demonstration System for the Reflected Solar Instrument for the Climate Absolute Radiance and Refractivity Observatory

    NASA Technical Reports Server (NTRS)

    Thome, Kurtis; McCorkel, Joel; Hair, Jason; McAndrew, Brendan; Daw, Adrian; Jennings, Donald; Rabin, Douglas

    2012-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission addresses the need to observe high-accuracy, long-term climate change trends and to use decadal change observations as the most critical method to determine the accuracy of climate change. One of the major objectives of CLARREO is to advance the accuracy of SI traceable absolute calibration at infrared and reflected solar wavelengths. This advance is required to reach the on-orbit absolute accuracy required to allow climate change observations to survive data gaps while remaining sufficiently accurate to observe climate change to within the uncertainty of the limit of natural variability. While these capabilities exist at NIST in the laboratory, there is a need to demonstrate that it can move successfully from NIST to NASA and/or instrument vendor capabilities for future spaceborne instruments. The current work describes the test plan for the Solar, Lunar for Absolute Reflectance Imaging Spectroradiometer (SOLARIS) which is the calibration demonstration system (CDS) for the reflected solar portion of CLARREO. The goal of the CDS is to allow the testing and evaluation of calibration approaches , alternate design and/or implementation approaches and components for the CLARREO mission. SOLARIS also provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. The end result of efforts with the SOLARIS CDS will be an SI-traceable error budget for reflectance retrieval using solar irradiance as a reference and methods for laboratory-based, absolute calibration suitable for climate-quality data collections. The CLARREO mission addresses the need to observe high-accuracy, long-term climate change trends and advance the accuracy of SI traceable absolute calibration. The current work describes the test plan for the SOLARIS which is the calibration demonstration system for the reflected solar portion of CLARREO. SOLARIS provides a test-bed for detector technologies, non-linearity determination and uncertainties, and application of future technology developments and suggested spacecraft instrument design modifications. The end result will be an SI-traceable error budget for reflectance retrieval using solar irradiance as a reference and methods for laboratory-based, absolute calibration suitable for climate-quality data collections.

  6. Reconstruction of 3D refractive index profiles of PM PANDA optical fiber using digital holographic method

    NASA Astrophysics Data System (ADS)

    Wahba, H. H.

    2014-10-01

    In this paper, the refractive indices distributions on the two birefringent axes of polarization maintaining (PM) PANDA type optical fiber are reconstructed. The local refraction of the incident rays crossing the PM optical fiber is considered. Off-axis digital holographic interferometric phase shifting arrangement is employed in this investigation. The recorded mutual phase shifted holograms, starts with 0° with steps of π/4, are combined and numerically reconstructed in the image plane to obtain the optical interference phase map. Consequently, the optical phase differences due to the PM optical fiber are extracted after unwrapping and background subtraction of the enhanced optical interference phase map. The birefringence and the beat length in the two directions, fast and slow axes of PM optical fiber, of polarizations in the core region are calculated. This holographic technique and the advanced analysis of the phase shifting permit the calculation of the 3D refractive index distributions for PM PANDA optical fiber.

  7. Refractive index profiles of planar optical waveguides in ?-BBO produced by silicon ion implantation

    NASA Astrophysics Data System (ADS)

    Wang, Xue-Lin; Chen, Feng; Lu, Fei; Fu, Gang; Li, Shi-Ling; Wang, Ke-Ming; Lu, Qing-Ming; Shen, Ding-Yu; Ma, Hong-Ji; Nie, Rui

    2004-12-01

    The planar waveguides have been fabricated in z-cut beta barium metaborate crystals by 2.8 MeV Si+ ion implantation with doses of 1 1015 and 3 1015 ions/cm2 at room temperature. The waveguides were characterized by the prism-coupling method. The refractive index profiles were reconstructed using reflectivity calculation method. It is found that relatively large positive changes of extraordinary refractive indices happen in the guiding regions, and the negative changes of ordinary refractive indices happen at the end of the track. TRIM'98 (transport of ions in matter) code was used to simulate the damage profile in ?-BBO by 2.8 MeV Si+ ion implantation.

  8. Finite frequency f-sum rule for assessment of number density of gold nanoparticles (AuNPs) and Kramers-Kronig relation for refractive index of colloidal gold.

    PubMed

    Kontturi, Ville; Silfsten, Pertti; Peiponen, Kai-Erik

    2011-07-01

    Absorption spectra from colloids containing different concentrations of spherical gold nanoparticles in water were measured with a spectrophotometer. The absorption spectra were used to calculate the number density of nanoparticles (NPs) with the aid of an unconventional finite spectral band f-sum rule applied for gold colloid. Good correlation between the number density of dispersion electrons, obtained from the f-sum rule, and the number density of nanoparticles was found. The effective absolute refractive index of the gold colloid was obtained with the aid of a singly subtractive Kramers-Kronig relation, and in addition the refractive index change due to the nanoparticles was obtained with the aid of a conventional Kramers-Kronig relation. Such optical properties are valuable in studies of light interaction with nanoparticles. PMID:21740635

  9. Cryogenic Refractive Index and Coefficient of Thermal Expansion for the S-TIH1 Glass

    NASA Technical Reports Server (NTRS)

    Quijada, Manuel A.; Leviton, Douglas; Content, David

    2013-01-01

    Using the CHARMS facility at NASA GSFC, we have measured the cryogenic refractive index of the Ohara S-TIH1 glass from 0.40 to 2.53 micrometers and from 120 to 300 K. We have also examined the spectral dispersion and thermo-optic coefficients (dn/dT). We also derived temperature-dependent Sellmeier models from which refractive index may be calculated for any wavelength and temperature within the stated ranges of each model. The S-TIH1 glass we tested exhibited unusual behavior in the thermo-optic coefficient. We found that for delta < 0.5 micrometers, the index of refraction decrease with a decrease in temperature (positive dn/dT). However, the situation was reversed for delta larger than 0.63 micrometers, where the index will increase with a decrease in temperature (negative dn/dT). We also measured the coefficient of thermal expansion (CTE) for the similar batch of S-TIH1 glass in order to understand its thermal properties. The CTE showed a monotonic change with a decrease in temperature.

  10. Complex index of refraction estimation from degree of polarization with diffuse scattering consideration.

    PubMed

    Zhan, Hanyu; Voelz, David G; Cho, Sang-Yeon; Xiao, Xifeng

    2015-11-20

    The estimation of the refractive index from optical scattering off a target's surface is an important task for remote sensing applications. Optical polarimetry is an approach that shows promise for refractive index estimation. However, this estimation often relies on polarimetric models that are limited to specular targets involving single surface scattering. Here, an analytic model is developed for the degree of polarization (DOP) associated with reflection from a rough surface that includes the effect of diffuse scattering. A multiplicative factor is derived to account for the diffuse component and evaluation of the model indicates that diffuse scattering can significantly affect the DOP values. The scattering model is used in a new approach for refractive index estimation from a series of DOP values that involves jointly estimating n, k, and ρd with a nonlinear equation solver. The approach is shown to work well with simulation data and additive noise. When applied to laboratory-measured DOP values, the approach produces significantly improved index estimation results relative to reference values. PMID:26836553

  11. Methods to calibrate and scale axial distances in confocal microscopy as a function of refractive index

    PubMed Central

    BESSELING, TH; JOSE, J; BLAADEREN, A VAN

    2015-01-01

    Accurate distance measurement in 3D confocal microscopy is important for quantitative analysis, volume visualization and image restoration. However, axial distances can be distorted by both the point spread function (PSF) and by a refractive-index mismatch between the sample and immersion liquid, which are difficult to separate. Additionally, accurate calibration of the axial distances in confocal microscopy remains cumbersome, although several high-end methods exist. In this paper we present two methods to calibrate axial distances in 3D confocal microscopy that are both accurate and easily implemented. With these methods, we measured axial scaling factors as a function of refractive-index mismatch for high-aperture confocal microscopy imaging. We found that our scaling factors are almost completely linearly dependent on refractive index and that they were in good agreement with theoretical predictions that take the full vectorial properties of light into account. There was however a strong deviation with the theoretical predictions using (high-angle) geometrical optics, which predict much lower scaling factors. As an illustration, we measured the PSF of a correctly calibrated point-scanning confocal microscope and showed that a nearly index-matched, micron-sized spherical object is still significantly elongated due to this PSF, which signifies that care has to be taken when determining axial calibration or axial scaling using such particles. PMID:25444358

  12. Infrared intensities of liquids. XVII. Infrared refractive indices from 8000 to 350 cm - 1, absolute integrated absorption intensities, transition moments, and dipole moment derivatives of methan-d3-ol and methanol-d4 at 25 C

    NASA Astrophysics Data System (ADS)

    Bertie, John E.; Zhang, Shuliang L.

    1994-11-01

    This paper reports absolute infrared absorption intensities of liquids methan-d3-ol (CD3OH) and methanol-d4 (CD3OD) at 25 C between 8000 and 350 cm-1. Measurements were made by multiple attenuated total reflection spectroscopy with the CIRCLE cell, and by transmission spectroscopy with transmission cells fitted with calcium fluoride windows. In both cases, the spectra were converted to infrared real and imaginary refractive index spectra. The refractive indices obtained by these two methods agreed excellently and were combined to yield an imaginary refractive index spectrum k(?) between 7244 and 350 cm-1 for CD3OH and between 5585 and 350 cm-1 for CD3OD. The imaginary refractive index spectrum was arbitrarily set to zero from 8000 to 7244 cm-1 (CD3OH) or 5585 cm-1 (CD3OD), where k is always less than 410-6, in order that the real refractive index can be calculated below 8000 cm-1 by Kramers-Krnig transformation. The results are reported as graphs and tables of the refractive indices between 8000 and 350 cm-1, from which all other infrared properties of the two liquids can be calculated. The estimated accuracy, not precision, of the imaginary refractive index is 3%, except for 10%, where k is less than 410-5. The estimated accuracy of the real refractive index is better than 0.5%. In order to obtain molecular information from the measurements, the spectra of the imaginary polarizability multiplied by wave number ??m` were calculated under the assumption of the Lorentz local field. The area under these ??m` spectra was separated into the integrated intensities of different vibrations. The magnitudes of the transition moments were calculated from the integrated intensities, and the double harmonic approximation was used to calculate the magnitudes of the dipole moment derivatives of the liquid-state molecules with respect to the normal coordinates. Dipole moment derivatives with respect to internal coordinates were calculated under the simplest approximations, the validity of which is demonstrated by the experimental data in many cases. The consistency of the dipole moment derivatives with respect to internal coordinates obtained for different isotopomers is shown through their relative rotational corrections. Results are presented for the O-H, O-D, C-H, and C-D stretches; the C-O-H in-plane bending; and the D-C-O-H and D-C-O-D torsion vibrations.

  13. Simultaneous measurement of refractive index and thickness of birefringent wave plates

    SciTech Connect

    Yeh, Y.-L

    2008-04-01

    A nondestructive measurement system based on a position sensing detector (PSD) and a laser interferometer for determining the thickness and refractive indices of birefringent optical wave plates has been developed. Unlike previous methods presented in the literature, the proposed metrology system allows the refractive index and thickness properties of the optical plate to be measured simultaneously. The experimental results obtained for the e-light and o-light refractive indices of a commercially available birefringent optical wave plate with refractive indices of no=1.542972 and ne=1.552033 are found to be accurate to within 0.004132 and 0.000229, respectively. Furthermore, the experimentally derived value of the wave plate thickness deviates by no more than 0.9 {mu}m from the analytically derived value of 453.95 {mu}m. Overall, the experimental results confirm that the proposed metrology system provides a simple yet highly accurate means of obtaining simultaneous measurements of the refractive indices and thickness of birefringent optical wave plates.

  14. Block copolymer assisted refractive index engineering of metal oxides for applications in optical sensing

    NASA Astrophysics Data System (ADS)

    Poole, Zsolt L.; Ohodnicki, Paul; Buric, Michael; Yan, Aidong; Riyadh, Shaymaa; Lin, Yuankun; Chen, Kevin P.

    2014-09-01

    We demonstrate that the refractive indices of important functional metal oxides (TiO2, SnO2, and ZnO) can be engineered "at will" for applications in photonics engineering. The tailoring of the refractive indices is accomplished by 3D nanostructuring in the sub-wavelength regime (50nm or less) using the method of block-copolymer templating combined with a low cost solution processing approach. Using this method, the index of refraction of the demonstrated metal oxides and their doped variants can be engineered to be as low as 1.25. We will present both numerical simulations and experimental data demonstrating the unrestricted integration of functional metal oxides with a D-shaped optical fiber for applications in chemical and biological sensing. Using the developed refractive index engineering scheme, we introduce a novel hydrogen sensor by integrating a palladium doped TiO2 nanomaterial with D-shaped optical fiber and provide sensor characterization up to 700°C for applications in the energy sector.

  15. Measuring the Refractive Index of Bovine Corneal Stromal Cells Using Quantitative Phase Imaging

    PubMed Central

    Gardner, Steven J.; White, Nick; Albon, Julie; Knupp, Carlo; Kamma-Lorger, Christina S.; Meek, Keith M.

    2015-01-01

    The cornea is the primary refractive lens in the eye and transmits >90% of incident visible light. It has been suggested that the development of postoperative corneal haze could be due to an increase in light scattering from activated corneal stromal cells. Quiescent keratocytes are thought to produce crystallins that match the refractive index of their cytoplasm to the surrounding extracellular material, reducing the amount of light scattering. To test this, we measured the refractive index (RI) of bovine corneal stromal cells, using quantitative phase imaging of live cells in vitro, together with confocal microscopy. The RI of quiescent keratocytes (RI = 1.381 ± 0.004) matched the surrounding matrix, thus supporting the hypothesis that keratocyte cytoplasm does not scatter light in the normal cornea. We also observed that the RI drops after keratocyte activation (RI = 1.365 ± 0.003), leading to a mismatch with the surrounding intercellular matrix. Theoretical scattering models showed that this mismatch would reduce light transmission in the cornea. We conclude that corneal transparency depends on the matching of refractive indices between quiescent keratocytes and the surrounding tissue, and that after surgery or wounding, the resulting RI mismatch between the activated cells and their surrounds significantly contributes to light scattering. PMID:26488650

  16. Index of Refraction and Absorption Coefficient Spectra of Paratellurite in the Terahertz Region

    NASA Astrophysics Data System (ADS)

    Unferdorben, Márta; Buzády, Andrea; Hebling, János; Kiss, Krisztián; Hajdara, Ivett; Kovács, László; Péter, Ágnes; Pálfalvi, László

    2016-03-01

    Index of refraction and absorption coefficient spectra of pure paratellurite (α-TeO2) crystal as a potential material for terahertz (THz) applications were determined in the 0.25-2 THz frequency range at room temperature by THz time domain spectroscopy (THz-TDS). The investigation was performed with beam polarization both parallel (extraordinary polarization) and perpendicular (ordinary polarization) to the optical axis [001] of the crystal. Similarly to the visible spectral range, positive birefringence was observed in the THz range as well. It was shown that the values of the refractive index for extraordinary polarization are higher and show significantly larger dispersion than for the ordinary one. The absorption coefficient values are also larger for extraordinary polarization. The measured values were fitted by theoretical curves derived from the complex dielectric function containing independent terms of Lorentz oscillators due to phonon-polariton resonances. The results are compared with earlier publications, and the observed significant discrepancies are discussed.

  17. Design of reflective optical fiber sensor for determining refractive index and sugar concentration of aqueous solutions

    NASA Astrophysics Data System (ADS)

    Marzuki, Ahmad; Wulan Sari, Nila; Riatun

    2016-02-01

    A reflective optical fiber sensor designed for measuring refractive index and sugar concentration of aqueous solutions is described. Two strains of parallel polymer optical fibers (POF) were wrapped in a bundle such that one of their fiber's end cross-sections had the same distance to the mirror surface. The light coming out from one strain of the fiber was reflected by the mirror to the second fiber. Sugar concentration of the aqueous solution filling the space between the fiber ends and the mirror was varied (1.0 M, 1.5 M, 2.0 M, 2.5 M, 3.0 M, 4.0 M, and 5.0 M). It was shown from the experiment that light intensity detected by photo-detector is linearly related to the percentage of the dissolved sugar in the solution as well as the variation of the sugar solution refractive index (R2 = 0.987).

  18. Femtosecond laser fabrication of long period fiber gratings and applications in refractive index sensing

    NASA Astrophysics Data System (ADS)

    Li, Benye; Jiang, Lan; Wang, Sumei; Tsai, Hai-Lung; Xiao, Hai

    2011-11-01

    An improved point-by-point inscription method is proposed to fabricate long period fiber gratings (LPFGs) by using a laser operating at 800 nm with 35 fs duration pulses. The sensitivity to misalignment between the core and the focus is reduced by scanning a rectangular part on the fiber. LPFGs with an attenuation depth of 20 dB are achieved within the wavelength range of 1465-1575 nm. Characterization of the temperature sensitivity and thermal stability of the LPFGs is presented. A 5.6 nm wavelength shift and a 1.2 dB decrease in the attenuation peak are observed following heat treatment at 600 °C for 4 h. The fabricated LPFGs are used as refractive index sensors. The effect of heat treatment on the response of the LPFGs to refractive index changes is also studied.

  19. New SPR PCF D-type optical fiber sensor configuration for refractive index measurement

    NASA Astrophysics Data System (ADS)

    Santos, D. F.; Guerreiro, A.; Baptista, J. M.

    2015-09-01

    This paper presents the performance analysis of a new geometry sensing configuration for refractive index, based on surface plasmon resonance (SPR) in photonic crystal fiber (PCF) D-type optical fiber with a thin gold layer, using the finite element method (FEM). The configuration is analyzed in terms of the loss. The results are compared with a conventional SPR D-type and with a PCF D-type optical fiber sensor for refractive index measurement. The simulation results show an improvement of the sensitivity and resolution (3.70103nm/RIU and 2.7210-5RIU, respectively, when considering an accurately spectral variation detection of 0.1nm).

  20. Measurement of nonlinear refractive index based on multiple configuration of FBG in generating multi wavelength

    NASA Astrophysics Data System (ADS)

    Abdullah, Mohd Nizam; Shaari, Sahbudin; Ehsan, Abang Annuar; Menon, Susthitha; Zakaria, Osman

    2015-06-01

    A reliable method for measurement of the nonlinear refractive index through application of multi wavelength phenomenon. Multi wavelength realisation based on Erbium doped fibre laser (EDFL) is proposed and experimentally demonstrated. A combination of 15 m high efficiency Erbium doped fibre (EDF) and a 20 m Photonic Crystal Fibre (PCF) as main catalyst to suppress the homogenous broadening of EDF and to obtain highly stability of multi wavelength through insertion of a set of fibre Bragg gratings (FBGs) in the cavity. This PCF has zero dispersion of 1040 nm which mismatch from transmission window of 1550 nm. A reliable repeatability of multi wavelength based on multiple configuration of FBGs less than 0.2% obtained. This consistent results influence in determination of nonlinear refractive index by relation of four wave mixing (FWM).

  1. Contribution of the Refractive Index Fluctuations to the Length Noise in Displacement Interferometry

    NASA Astrophysics Data System (ADS)

    Hol, Miroslava; Hrabina, Jan; Sarbort, Martin; Oulehla, Jindrich; Cp, Ondrej; Lazar, Josef

    2015-10-01

    We report on investigations of how fast changes of the refractive index influence the uncertainty of interferometric displacement measurements. Measurement of position within a limited range is typical for precise positioning of coordinate measuring systems, such as nanometrology standards combined with scanning probe microscopy (SPM). The varying refractive index of air contributes significantly to the overall uncertainty; it plays a role especially in case of longer-range systems. In our experiments we have observed that its fast variations, seen as length noise, are not linearly proportional to the measuring beam path and play a significant role only over distances longer than 50 mm. Thus, we found that over longer distances the length noise rises proportionally. The measurements were performed under conditions typical for metrology SPM systems

  2. Interferometric measurement of the resonant absorption and refractive index in rubidium gas

    NASA Astrophysics Data System (ADS)

    Libbrecht, K. G.; Libbrecht, M. W.

    2006-12-01

    We present a laboratory demonstration of the Kramers-Kronig relation between the resonant absorption and refractive index in rubidium gas. Our experiment uses a rubidium vapor cell in one arm of a simple Mach-Zehnder interferometer. As the laser frequency is scanned over an atomic resonance, the interferometer output is affected by variations of both the absorption and refractive index of the gas with frequency, all of which can be calculated in a straightforward manner. Changing the vapor density and interferometer phase produces a family of different output signals. The experiment was performed using a commercially available tunable diode laser system that was designed specifically for the undergraduate physics laboratory. As a teaching tool this experiment is reliable, fun, and instructive, while it also introduces the student to some sophisticated and fundamental physical concepts.

  3. Possible effects of clear-air refractive-index perturbations on SAR images.

    SciTech Connect

    Dickey, Fred McCartney; Muschinski, Andreas; Doerry, Armin Walter

    2005-03-01

    Airborne synthetic aperture radar (SAR) imaging systems have reached a degree of accuracy and sophistication that requires the validity of the free-space approximation for radio-wave propagation to be questioned. Based on the thin-lens approximation, a closed-form model for the focal length of a gravity wave-modulated refractive-index interface in the lower troposphere is developed. The model corroborates the suggestion that mesoscale, quasi-deterministic variations of the clear-air radio refractive-index field can cause diffraction patterns on the ground that are consistent with reflectivity artifacts occasionally seen in SAR images, particularly in those collected at long ranges, short wavelengths, and small grazing angles.

  4. Diffractive Optical Analysis for Refractive Index Sensing using Transparent Phase Gratings.

    PubMed

    Kumawat, Nityanand; Pal, Parama; Varma, Manoj

    2015-01-01

    We report the implementation of a micro-patterned, glass-based photonic sensing element that is capable of label-free biosensing. The diffractive optical analyzer is based on the differential response of diffracted orders to bulk as well as surface refractive index changes. The differential read-out suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6??10(-7) was achieved with this technique with scope for further improvement. PMID:26578408

  5. The refractive index and electronic gap of water and ice increase with increasing pressure

    PubMed Central

    Pan, Ding; Wan, Quan; Galli, Giulia

    2014-01-01

    Determining the electronic and dielectric properties of water at high pressure and temperature is an essential prerequisite to understand the physical and chemical properties of aqueous environments under supercritical conditions, for example, in the Earth interior. However, optical measurements of compressed ice and water remain challenging, and it has been common practice to assume that their band gap is inversely correlated with the measured refractive index, consistent with observations reported for hundreds of materials. Here we report ab initio molecular dynamics and electronic structure calculations showing that both the refractive index and the electronic gap of water and ice increase with increasing pressure, at least up to 30?GPa. Subtle electronic effects, related to the nature of interband transitions and band edge localization under pressure, are responsible for this apparently anomalous behaviour. PMID:24861665

  6. Refractive Index Sensor Based on a 1D Photonic Crystal in a Microfluidic Channel

    PubMed Central

    Nunes, Pedro S.; Mortensen, Niels Asger; Kutter, Jrg P.; Mogensen, Klaus B.

    2010-01-01

    A refractive index sensor has been fabricated in silicon oxynitride by standard UV lithography and dry etching processes. The refractive index sensor consists of a 1D photonic crystal (PhC) embedded in a microfluidic channel addressed by fiber-terminated planar waveguides. Experimental demonstrations performed with several ethanol solutions ranging from a purity of 96.00% (n = 1.36356) to 95.04% (n = 1.36377) yielded a sensitivity (??/?n) of 836 nm/RIU and a limit of detection (LOD) of 6 10?5 RIU, which is, however, still one order of magnitude higher than the theoretical lower limit of the limit of detection 1.3 10?6 RIU. PMID:22294930

  7. Determining the complex index of refraction of an unknown object using turbulence-degraded polarimetric imagery

    NASA Astrophysics Data System (ADS)

    Hyde, Milo W., IV

    2010-12-01

    A novel index-of-refraction material-characterization technique using passive polarimetric imagery degraded by atmospheric turbulence is presented. The method uses a variant of the LeMaster and Cain [J. Opt. Soc. Am. A 25(9), 2170-2176 (2008)] blind-deconvolution algorithm to recover the true object (i.e., the first Stokes parameter), the degree of linear polarization, and the polarimetric-image point spread functions. Nonlinear least squares is then used to find the value of the complex index of refraction that best fits the theoretical degree of linear polarization, derived using a polarimetric bidirectional reflectance distribution function, to the turbulence-corrected degree of linear polarization. To verify the proposed material-characterization technique, experimental results of two painted metal samples are provided and analyzed.

  8. Measurement of air refractive index based on surface plasmon resonance and phase detection.

    PubMed

    Chen, Qianghua; Luo, Huifu; Wang, Sumei; Wang, Feng

    2012-07-15

    A method for refractive index of air measurement is presented based on surface plasmon resonance (SPR) and phase detection using a dual-frequency laser interferometer. Theoretical analyses indicate that the phase-difference variation of the measurement signal versus the reference signal is linear with refractive index of air (RIA) fluctuation, and the calculation formula of RIA is derived. The structure design of the self-adaptive SPR sensor greatly reduces the measurement error resulting from the incident angle shift and improves the sensitivity. The experiments show that measurement uncertainty of 10(-6) order has been achieved when phase detection precision is 0.1. The phenomenon of sudden phase variation during air pumping and air filling, which is caused by temperature fluctuation, is discussed. PMID:22825177

  9. Diffractive Optical Analysis for Refractive Index Sensing using Transparent Phase Gratings

    NASA Astrophysics Data System (ADS)

    Kumawat, Nityanand; Pal, Parama; Varma, Manoj

    2015-11-01

    We report the implementation of a micro-patterned, glass-based photonic sensing element that is capable of label-free biosensing. The diffractive optical analyzer is based on the differential response of diffracted orders to bulk as well as surface refractive index changes. The differential read-out suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6 × 10‑7 was achieved with this technique with scope for further improvement.

  10. Analysis of thermo-optic effect-based refractive index dynamic modulation in microspherical resonator.

    PubMed

    Wang, Yue; Wang, Quan-Long; Zhou, Song; Wu, Jun-Feng; Wu, Yi-Hui

    2015-10-01

    The thermo-optic effect has been utilized to modulate the refractive index dynamically within a whispering gallery mode resonator. Modulation with a large tuning range is mostly performed for mode locking and dynamic control of the optical path at a modulation frequency as low as several hertz, while high-frequency modulation up to megahertz is mainly exploited in optical switching devices with small tuning range. Here, we introduce the response functions theoretically to describe the dynamic response of temperature changes in the mode volume and the resonator body, respectively. This result is verified experimentally in silica microspherical resonators. The dependence of the tuning range on the modulation frequency is achieved. This knowledge could pave the way toward more practical control of refractive index in microresonators. PMID:26479610

  11. Determination of refractive index and concentration of iodine solutions using opals

    NASA Astrophysics Data System (ADS)

    K?pi?ska, Miros?awa; Starczewska, Anna; Szala, Janusz

    2014-03-01

    The determination of refractive index of iodine-ethanol solutions using SiO2 opals has been presented. For the first time concentration of solution iodine in ethanol has been determined by applying a simple method of using opal and de Feijter's relation. Basing on wavelength of diffraction peaks the appropriate formula describing concentration of iodine ethanol solution has been evolved. The uncertainty of the determined concentration has been established, too. The coefficient dnc/dC = 0.0201(4) (% w/w-1) of the linear dependence between refractive index and the concentration of iodine solution has been determined. The procedure of calibration of the used opal sensor is described. The opal sensor is not distracted by the measurement and can be used repeatedly.

  12. Dual-wavelength diffraction phase microscopy for simultaneous measurement of refractive index and thickness.

    PubMed

    Jafarfard, Mohammad Reza; Moon, Sucbei; Tayebi, Behnam; Kim, Dug Young

    2014-05-15

    We present a quantitative phase microscopy scheme that simultaneously acquires two phase images at different wavelengths. The simultaneous dual-wavelength measurement was performed with a diffraction phase microscope (DPM) based on a transmission grating and a spatial filter that form a common-path imaging interferometer. With a combined laser source that generates two-color light continuously, a different diffraction order of the grating was utilized for each wavelength component so that the dual-wavelength interference pattern could be distinguished by the distinct fringe frequencies. Our dual-wavelength phase imaging allowed us to extract information on the physical thickness and the refractive index for a specimen immersed in a highly dispersive surrounding medium. We found that our dual-wavelength DPM (DW-DPM) provides an accurate measurement of the volume and the refractive index of a microscopy sample with good measurement stability that results from the common-path geometry. PMID:24978234

  13. Pressure dependence of the refractive index in wurtzite and rocksalt indium nitride

    SciTech Connect

    Oliva, R.; Yamaguchi, T.; Nanishi, Y.

    2014-12-08

    We have performed high-pressure Fourier transform infrared reflectance measurements on a freestanding InN thin film to determine the refractive index of wurtzite InN and its high-pressure rocksalt phase as a function of hydrostatic pressure. From a fit to the experimental refractive-index curves including the effect of the high-energy optical gaps, phonons, free carriers, and the direct (fundamental) band-gap in the case of wurtzite InN, we obtain pressure coefficients for the low-frequency (electronic) dielectric constant ε{sub ∞}. Negative pressure coefficients of −8.8 × 10{sup −2 }GPa{sup −1} and −14.8 × 10{sup −2 }GPa{sup −1} are obtained for the wurtzite and rocksalt phases, respectively. The results are discussed in terms of the electronic band structure and the compressibility of both phases.

  14. Band gap and refractive index tunability in thallium based layered mixed crystals

    NASA Astrophysics Data System (ADS)

    Gasanly, N. M.

    2015-07-01

    Compositional variation of the band gap energy and refractive index of TlMeX2-type (Me = Ga or In and X = S or Se) layered mixed crystals have been studied by the transmission and reflection measurements in the wavelength range of 400-1100 nm. The analysis of absorption data of TlGa1-xInxSe2, TlGa(S1-xSex)2, TlGa1-xInxS2, and TlIn(Se1-xSx)2 mixed crystals revealed the presence of both optical indirect and direct transitions. It was found that the energy band gaps of mixed crystals decrease at the replacing of gallium atoms by indium and of sulfur atoms by selenium ones. Through the similar replacing of atoms (smaller atoms by larger ones) in the studied mixed crystals, the refractive index shows the quite opposite behavior.

  15. Three-dimensional shape measurement based on dual-refractive-index digital holography

    NASA Astrophysics Data System (ADS)

    Cai, Xiao-ou; Hu, Feng-jun; Wang, Hui

    2015-09-01

    A novel phase-imaging method based on dual-refractive-index digital holography has been presented, which in principle can be arbitrarily large compared to the wavelength and does not involve the usual phase unwrapping by detection of phase discontinuity. The method consists of the generation and combination of two phase maps in a digital holography system by use of two separate refractive indexes which varies with the air density in an air chamber where a recorded 3D object is in. For example, we have reconstructed the surface of a remote control keypad of size 5 mm×5 mm and maximum axial depth 0.631 mm, and the experimental result shows that the proposed approach is feasible and effective.

  16. Exciton effects in the index of refraction of multiple quantum wells and superlattices

    NASA Technical Reports Server (NTRS)

    Kahen, K. B.; Leburton, J. P.

    1986-01-01

    Theoretical calculations of the index of refraction of multiple quantum wells and superlattices are presented. The model incorporates both the bound and continuum exciton contributions for the gamma region transitions. In addition, the electronic band structure model has both superlattice and bulk alloy properties. The results indicate that large light-hole masses, i.e., of about 0.23, produced by band mixing effects, are required to account for the experimental data. Furthermore, it is shown that superlattice effects rapidly decrease for energies greater than the confining potential barriers. Overall, the theoretical results are in very good agreement with the experimental data and show the importance of including exciton effects in the index of refraction.

  17. Simultaneous measurements of refractive index and density in a microemulsion near a critical end point

    NASA Astrophysics Data System (ADS)

    Rebbouh, N.; Beysens, D.; Lalanne, J. R.

    1990-12-01

    The behavior of the density and the refractive index of a microemulsion of sodium dodecyl sulfate, water, n-pentanol, and n-dodecane is investigated near its critical end point. Measurements are made simultaneously and both are to an accuracy of a few ppm. In contrast to the density data which can be fitted to a regular, linear behavior in the whole temperature range (28.3-30.5 C), the refractive index exhibits a pronounced anomaly near the critical point. The temperature dependence of such an anomaly cannot be described by a power law behavior. However, it can be understood as a chemical change connected to morphological modifications in the dispersed phase, a phenomenon connected to the close vicinity of sponge-like phases. This approach accounts well for the data.

  18. Sustainable UV-curable low refractive index resins with novel polymers for polymer cladding materials

    NASA Astrophysics Data System (ADS)

    Tokoro, Hiroki; Ishikawa, Takako; Koike, Nobuyuki; Yamashina, Yohzoh

    2014-03-01

    Low refractive index polymers are used as cladding materials for high numerical aperture (NA) fibers. Since transparent fluoro polymers are ideal for this application, they have been used over many years. However, some fluoro chemicals face an issue related to perfluoro octanoic acid (PFOA) which is caused by its longtime persistence in the environment and human body. In this research, non-PFOA type UV curable fluoro resins suitable for cladding were developed with novel materials. The cured films showed high transparency, good adhesion to glass and low refractive index of 1.359 and 1.386 at 850 nm. Optical fibers prepared with those cladding showed almost equivalent attenuation to a fiber with commercially available material.

  19. Diffractive Optical Analysis for Refractive Index Sensing using Transparent Phase Gratings

    PubMed Central

    Kumawat, Nityanand; Pal, Parama; Varma, Manoj

    2015-01-01

    We report the implementation of a micro-patterned, glass-based photonic sensing element that is capable of label-free biosensing. The diffractive optical analyzer is based on the differential response of diffracted orders to bulk as well as surface refractive index changes. The differential read-out suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6 × 10−7 was achieved with this technique with scope for further improvement. PMID:26578408

  20. A novel laser gain medium: Micro-sphere array cooled by refractive index-matched coolant

    NASA Astrophysics Data System (ADS)

    Gui, Luo; Ding, Jianyong; She, Jiangbo; Peng, Bo; Wei, Wei; Fan, Dianyuan

    2013-09-01

    A micro-sphere array laser gain medium cooled by refractive index-matched coolant was demonstrated for the first time to our knowledge. The new concept is possessed of potential to improve thermal management, to increase the thermal load capacity and to build large scale laser medium with small-sized solid laser materials. The feasibility was experimentally proved with an oscillator experiment in which reliable laser output was observed: the maximum output was 113.3 mJ for the pump energy of 765.8 mJ, the threshold was 131.7 mJ and the slope efficiency was 19%. Promising improvement could be achieved by employing methods for maintaining accurate refractive index matching during the lasing process.

  1. Densities and refractive indexes of aqueous (Li,K,Na) NO[sub 3] mixtures

    SciTech Connect

    Ally, M.R.; Zaltash, A.; Linkous, R.L. . Energy Div.); Klatt, L.N. . Analytical Chemistry Div.)

    1991-04-01

    This paper describes experimental procedures and techniques for measuring densities and/or refractive indexes of aqueous salt solutions between 25 and 200 [degrees]C and with 18.90-90.50 wt % mixed salt (LINO[sub 3], KNO[sub 3], and NaNO[sub 3]). An electrolyte solution of (LI, K, Na) NO[sub 3] slats in water was chosen for study because of its recent development as a potential high-temperature heat pump fluid, but any other appropriate fluid may be accommodated for study in the apparatus. The densities and refractive indexes are shown to represent a convenient way to measuring the concentration of salt (or water), and accuracies of [plus minus]0.8 and [plus minus]0.3 wt % total mixed salt were achieved by using the above two methods, respectively.

  2. Refractive-index-matched hydrogel materials for measuring flow-structure interactions

    NASA Astrophysics Data System (ADS)

    Byron, Margaret L.; Variano, Evan A.

    2013-02-01

    In imaging-based studies of flow around solid objects, it is useful to have materials that are refractive-index-matched to the surrounding fluid. However, materials currently in use are usually rigid and matched to liquids that are either expensive or highly viscous. This does not allow for measurements at high Reynolds number, nor accurate modeling of flexible structures. This work explores the use of two hydrogels (agarose and polyacrylamide) as refractive-index-matched models in water. These hydrogels are inexpensive, can be cast into desired shapes, and have flexibility that can be tuned to match biological materials. The use of water as the fluid phase allows this method to be implemented immediately in many experimental facilities and permits investigation of high-Reynolds-number phenomena. We explain fabrication methods and present a summary of the physical and optical properties of both gels, and then show measurements demonstrating the use of hydrogel models in quantitative imaging.

  3. Properties of material in the submillimeter wave region (instrumentation and measurement of index of refraction)

    NASA Technical Reports Server (NTRS)

    Lally, J.; Meister, R.

    1983-01-01

    The Properties of Materials in the Submillimeter Wave Region study was initiated to instrument a system and to make measurements of the complex index of refraction in the wavelength region between 0.1 to 1.0 millimeters. While refractive index data is available for a number of solids and liquids there still exists a need for an additional systematic study of dielectric properties to add to the existing data, to consider the accuracy of the existing data, and to extend measurements in this wavelength region for other selected mateials. The materials chosen for consideration would be those with useful thermal, mechanical, and electrical characteristics. The data is necessary for development of optical components which, for example, include beamsplitters, attenuators, lenses, grids, all useful for development of instrumentation in this relatively unexploited portion of the spectrum.

  4. Uncertainty in length conversion due to change of sensitivity coefficients of refractive index

    NASA Astrophysics Data System (ADS)

    Wei, Dong; Aketagawa, Masato

    2015-06-01

    A value of length measured in air should be converted to the value in vacuum for the purpose of comparison. The typical values of the sensitivity coefficients for a particular wavelength (e.g. 632.99 nm) under standard environmental conditions are widely available. Because all measurements are not performed under standard environmental conditions and the sensitivity coefficient is affected by atmospheric pressure, temperature, and humidity, one question arises naturally: how does a measurement change with environmental conditions? This study investigates the uncertainty in length conversion due to the change of sensitivity coefficients of refractive index. We also clarify that there is no significant difference in conversion uncertainties via sensitivity coefficients of phase and group refractive indexes.

  5. A novel acousto-optic modulation-deflection mechanism using refractive index grating as graded index beam router

    NASA Astrophysics Data System (ADS)

    Jangjoo, Alireza; Reza Baezzat, Mohammad; Razavizadeh, Ahmad

    2014-03-01

    A novel acousto-optic modulation mechanism will be addressed in this paper. Focused Gaussian beam passing through acousto-optic media experiences different refractive index regions arising from acoustic waves generated by ultrasonic source. In this way according to the snell's law of refraction the beam propagation path will be altered when these periodic traveling waves reach the incoming radiation where a typical p-n junction photodiode located inside the rising or falling lobe of the undiffracted Gaussian beam senses these small lateral deflections. Due to small variations of the refractive index the magnitude of deflection will be up to tens of micron outside the modulator. Hence, sharp intensity gradient is required for detecting such small beam movements by appropriate lens configuration to focus the Gaussian profile on the detector junction area. In the other words intensity profile of zero order beam oscillates proportional to the time dependent amplitude of the acoustic waves versus previous methods that intensity of diffracted beam changes with applied ultrasonic intensity. The extracted signal properties depend on the beam collimation, quality of beam profile and depth of focus inside the modulator. The first experimental approach was proceeded using a collimated 532 nm diode laser source (TEM00), distilled water as interaction media and 10 MHz transducer as ultrasonic generator where a cylindrical glass column with input-output flat windows was used for liquid support. The present method has advantages over common acoustooptical techniques as low cost, simplicity of operation, direct modulation of the signal and minimum alignment requirement.

  6. Refractive index degeneration in older lenses: A potential functional correlate to structural changes that underlie cataract formation.

    PubMed

    Bahrami, Mehdi; Hoshino, Masato; Pierscionek, Barbara; Yagi, Naoto; Regini, Justyn; Uesugi, Kentaro

    2015-11-01

    A major structure/function relationship in the eye lens is that between the constituent proteins, the crystallins and the optical property of refractive index. Structural breakdown that leads to cataract has been investigated in a number of studies; the concomitant changes in the optics, namely increases in light attenuation have also been well documented. Specific changes in the refractive index gradient that cause such attenuation, however, are not well studied because previous methods of measuring refractive index require transparent samples. The X-ray Talbot interferometric method using synchrotron radiation allows for measurement of fine changes in refractive index through lenses with opacities. The findings of this study on older human lenses show disruptions to the refractive index gradient and in the refractive index contours. These disruptions are linked to location in the lens and occur in polar regions, along or close to the equatorial plane or in lamellar-like formations. The disruptions that are seen in the polar regions manifest branching formations that alter with progression through the lens with some similarity to lens sutures. This study shows how the refractive index gradient, which is needed to maintain image quality of the eye, may be disturbed and that this can occur in a number of distinct ways. These findings offer insight into functional changes to a major optical parameter in older lenses. Further studies are needed to elicit how these may be related to structural degenerations reported in the literature. PMID:26297613

  7. Measurement of the nonlinear refractive index of air constituents at mid-infrared wavelengths.

    PubMed

    Zahedpour, S; Wahlstrand, J K; Milchberg, H M

    2015-12-15

    We measure the nonlinear refractive index coefficients in N2, O2, and Ar from visible through mid-infrared wavelengths (?=0.4-2.4???m). The wavelengths investigated correspond to transparency windows in the atmosphere. Good agreement is found with theoretical models of ?(3). Our results are essential for accurately simulating the propagation of ultrashort mid-infrared pulses in the atmosphere. PMID:26670514

  8. Simultaneous determination of size and refractive index of red blood cells by light scattering measurements

    SciTech Connect

    Ghosh, N.; Buddhiwant, P.; Uppal, A.; Majumder, S.K.; Patel, H.S.; Gupta, P.K.

    2006-02-20

    We present a fast and accurate approach for simultaneous determination of both the mean diameter and refractive index of a collection of red blood cells (RBCs). The approach uses the peak frequency of the power spectrum and the corresponding phase angle obtained by performing Fourier transform on the measured angular distribution of scattered light to determine these parameters. Results on the measurement of two important clinical parameters, the mean cell volume and mean cell hemoglobin concentration of a collection of RBCs, are presented.

  9. The optimal design of photonic crystal optical devices with step-wise linear refractive index

    NASA Astrophysics Data System (ADS)

    Ma, Ji; Wu, Xiang-Yao; Li, Hai-Bo; Li, Hong; Liu, Xiao-Jing; Zhang, Si-Qi; Chen, Wan-Jin; Wu, Yi-Heng

    2015-10-01

    In the paper, we have studied one-dimensional step-wise linear photonic crystal with and without defect layer, and analyzed the effect of defect layer position, thickness, refractive index real part and imaginary part on the transmissivity, electric field distribution and output electric field intensity. By calculation, we have obtained a set of optimal parameters, which can be optimally designed optical device, such as optical amplifier, attenuator, optical diode by the step-wise linear photonic crystal.

  10. Refractive index dynamics of InAs/GaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Crowley, M. T.; Houlihan, J.; Piwonski, T.; O'Driscoll, I.; Williams, D. P.; O'Reilly, E. P.; Uskov, A. V.; Huyet, G.

    2013-07-01

    The refractive index dynamics of an InAs/InGaAs/GaAs dots-in-a-well semiconductor optical amplifier is calculated and compared with experimental results. The fast and slow recovery timescales together with the behaviour with increasing injection are reproduced and explained in terms of the density of carriers available in upper quantum dot and continuum states. Also, a Coulomb-mediated shift of the dot susceptibility is suggested as responsible for the fast recovery of the phase.

  11. Light-bullet modes in self-induced-transparency media with refractive-index modulation

    NASA Astrophysics Data System (ADS)

    Blaauboer, Miriam; Kurizki, Gershon; Malomed, Boris A.

    2002-06-01

    We predict the existence of a new type of spatiotemporal soliton (so-called light bullets) in two-dimensional self-induced-transparency media with refractive-index modulation in the direction transverse to that of pulse propagation. These self-localized guided modes are found in an approximate analytical form. Their existence and stability are confirmed by numerical simulations, and they may have advantageous properties for signal transmission.

  12. A Refractive INdex Gradient (RING) diagnostic for transient discharges or expansions of vapor or plasmas

    SciTech Connect

    Cuneo, M.E.; Lockner, T.R.; Tisone, G.S.; Bieg, K.W.; Stinnett, R.W. ); Chavez, J.R. )

    1990-01-01

    The use of lasers to measure plasma properties is well known. Common methods include interferometry (density), Schlieren (gradient of density), and shadowgraphy (derivative of gradient). The diagnostic described in this paper uses a fast silicon photodiode quadrant detector with a differential amplifier to temporally detect the refraction of a CW laser by transient discharges or expansions of vapor, gas or plasma. The laser beam is refracted by the gradient of the total index of refraction due to neutral and ionized atoms (positive index) and electrons (negative index) in those discharges. The output of the circuit is a voltage proportional to the deflection angle of the laser beam through the discharge. The method is a time-resolved, quantitative, species discriminating (i.e. atoms or electrons) Schlieren technique. The diagnostic is easy to field, sensitive (1.3 {plus minus} 0.1 to 3.3 {plus minus} 0.1 mv/{mu}rad depending on laser power, divergence, moment arm and circuit gain) and fast (rise time = 11 {plus minus} 1 to 24 {plus minus} 1 ns depending on various circuit parameters). Diagnostic theory, and circuit design and performance will be discussed. This refractive INdex Gradient (RING) diagnostic has been applied to measurements on several ion sources under development at Sandia for use on intense applied-B ion diodes in the light ion fusion program. Sources studied include different types of flashboards, a thermal evaporation lithium ion source, and a laser produced ion source. To illustrate the utility of this technique, examples of measurements on LEVIS (Laser EVaporation Ion Source), a laser produced active lithium ion source will be given. Measured properties include vapor/plasma production thresholds, expansion velocities, some species information, gradient profiles, and estimates of density profiles. 27 refs., 8 figs.

  13. Block Copolymer Nanocomposites with High Refractive Index Contrast for One-Step Photonics.

    PubMed

    Song, Dong-Po; Li, Cheng; Li, Wenhao; Watkins, James J

    2016-01-26

    Photonic crystals (PhCs) prepared using the self-assembly of block copolymers (BCPs) offer the potential for simple and rapid device fabrication but typically suffer from low refractive index contrast (Δn ≤ 0.1) between the phase-segregated domains. Here, we report the simple fabrication of BCP-based photonic nanocomposites with large differences in refractive index (Δn > 0.27). Zirconium oxide (ZrO2) nanoparticles coated with gallic acid are used to tune the optical constants of the target domains of self-assembled (polynorbornene-graft-poly(tert-butyl acrylate))-block-(polynorbornene-graft-poly(ethylene oxide)) (PtBA-b-PEO) brush block copolymers (BBCPs). Strong hydrogen-bonding interactions between the ligands on ZrO2 and PEO brushes of the BBCPs enable selective incorporation and high loading of up to 70 wt % (42 vol %) of the ZrO2 nanoparticles within the PEO domain, resulting in a significant increase of refractive index from 1.45 to up to 1.70. Consequently, greatly enhanced reflection at approximately 398 nm (increases of ∼250%) was observed for the photonic nanocomposites (domain spacing = 137 nm) relative to that of the unmodified BBCPs, which is consistent with numeric modeling results using transfer matrix methods. This work provides a simple strategy for a wide range tuning of optical constants of BCP domains, thereby enabling the design and creation of high-performance photonic coatings for various applications. The large refractive index contrast enables high reflectivity while simultaneously reducing the coating thickness necessary, compared to pure BCP systems. PMID:26713452

  14. Experimental determination of the effective refractive index in strongly scattering media

    NASA Astrophysics Data System (ADS)

    Gmez Rivas, J.; Dau, D. H.; Imhof, A.; Sprik, R.; Bret, B. P. J.; Johnson, P. M.; Hijmans, T. W.; Lagendijk, A.

    2003-05-01

    Measurements of the angular-resolved-optical transmission through strongly scattering samples of porous gallium phosphide are described. Currently porous GaP is the strongest-scattering material for visible light. From these measurements the effective refractive index and the average reflectivity at the sample interface can be obtained. These parameters are of great importance for an accurate interpretation of optical experiments, and are for the first time determined in strongly scattering samples.

  15. Enhanced refractive index without absorption in four-level asymmetrical double semiconductor quantum well

    NASA Astrophysics Data System (ADS)

    Kang, Chengxian; Wang, Zhiping; Yu, Benli

    2016-03-01

    We investigate the absorptive-dispersive properties of a weak probe field in a four-level asymmetrical double semiconductor quantum well. It is found that the enhanced refraction index without absorption can be easily controlled via adjusting properly the corresponding parameters of the system. Our scheme may provide some new possibilities for technological applications in dispersion compensation and solid-state quantum communication for quantum information processing.

  16. Retrieving the real refractive index of mono- and polydisperse colloids from reflectance near the critical angle.

    PubMed

    Reed, Benjamin E; Grainger, Roy G; Peters, Daniel M; Smith, Andrew J A

    2016-02-01

    We investigate the accuracy in retrieving the real refractive index of submicron aerosol particles, at a visible wavelength, from near critical angle reflectance measurements of a dilute suspension of the aerosol. A coherent scattering model (CSM) is used to model the coherent reflectance from the colloidal suspension. We use an extension of the model for polydisperse particles to properly account for the modified size distribution close to the incident medium to colloid interface. We perform a rigorous sensitivity analysis, for both the monodisperse and polydisperse models, to determine how experimental uncertainties propagate into uncertainty in the retrieval of real refractive index. The effect of non-spherical scattering was included in the sensitivity analysis by using T-matrix methods. Experimental reflectance data, at a wavelength of 635 nm, were obtained for monodisperse spherical latex particles, a polydisperse sand sample and a polydisperse volcanic ash sample. We show that the retrieved real refractive index for these particles is consistent with values obtained using other techniques. PMID:26906772

  17. On a quasi-wavelet model of refractive index fluctuations due to atmospheric turbulence.

    PubMed

    Prez, Daro G; Funes, Gustavo

    2015-12-14

    When studying light propagation through the atmosphere, it is usual to rely on widely used spectra such as the modified von Krmn or Andrews-Hill. These are relatively tractable models for the fluctuations of the refractive index, and are primarily used because of their mathematical convenience. They correctly describe the fluctuations behaviour at the inertial range yet lack any physical basis outside this range. In recent years, deviations from the Obukhov-Kolmogorov theory (e. g. interminttency, partially developed turbulence, etc.) have been built upon these models through the introduction of arbitrary spectral power laws. Here we introduce a quasi-wavelet model for the refractive index fluctuations which is based on a phenomenological representation of the Richardson cascade. Under this model, the atmospheric refractive index has a correct spectral representation for the inertial range, behaves as expected outside it, and even accounts for non-Kolmogorov behaviour; moreover, it has non-Gaussian statistics. Finally, we are able to produce second order moments under the Rytov approximation for the complex phase; we estimate the angle-of-arrival as an example of application. PMID:26698956

  18. Velocimetry with refractive index matching for complex flow configurations, phase 1

    NASA Technical Reports Server (NTRS)

    Thompson, B. E.; Vafidis, C.; Whitelaw, J. H.

    1987-01-01

    The feasibility of obtaining detailed velocity field measurements in large Reynolds number flow of the Space Shuttle Main Engine (SSME) main injector bowl was demonstrated using laser velocimetry and the developed refractive-index-matching technique. An experimental system to provide appropriate flow rates and temperature control of refractive-index-matching fluid was designed and tested. Test results are presented to establish the feasibility of obtaining accurate velocity measurements that map the entire field including the flow through the LOX post bundles: sample mean velocity, turbulence intensity, and spectral results are presented. The results indicate that a suitable fluid and control system is feasible for the representation of complex rocket-engine configurations and that measurements of velocity characteristics can be obtained without the optical access restrictions normally associated with laser velocimetry. The refractive-index-matching technique considered needs to be further developed and extended to represent other rocket-engine flows where current methods either cannot measure with adequate accuracy or they fail.

  19. Lattice and electronic contributions to the refractive index of CuWO4

    NASA Astrophysics Data System (ADS)

    Ruiz-Fuertes, J.; Pellicer-Porres, J.; Segura, A.; Rodríguez-Hernández, P.; Muñoz, A.

    2014-09-01

    We report an investigation of the refractive index dispersion and anisotropy in CuWO4 by means of interference measurements in two extinction directions from mid infrared to the visible region of the energy spectrum. The analysis of the refractive index dispersion yields ɛ(∞) = 4.5(1) for light polarization parallel to the c-axis and ɛ(∞) = 5.3(1) with respect to the other extinction axis. In addition, we report reflectance measurements carried out from the far infrared to the near ultraviolet to study the lattice and electronic contributions to the refractive index of CuWO4. We have determined the wavenumbers of nine infrared active lattice modes and compared them with previous ab initio calculations. The value of the Penn gap, 7 eV, as well as the origin of a structure observed at 4.4 eV in the reflectance spectrum, is discussed in the context of the CuWO4 electronic structure.

  20. Influence of the refractive index of liquids in the speckle pattern of multimode fibers

    NASA Astrophysics Data System (ADS)

    Galindez, Carlos; Lomer, Mauro; Rodriguez-Cobo, Luis; Lopez-Higuera, J. M.

    2012-10-01

    The distribution of the intensity of each speckle depends on the relative phases of modes in the multimode fiber, so they are extremely sensitive to external perturbations of the fiber. These perturbations can locally appear in the fiber without disrupting the entire optical assembly. If the refractive index of the outside medium of the fiber is changed, it can cause variations in the speckle pattern at the fiber output. Thus, by changing the refractive index of the outside medium the speckle pattern at the output fiber varies and its influence can be observed. In this paper we demonstrate the influence of the refractive index of liquids in the speckle pattern obtained by a multimode fiber. In order to obtain greater sensitivity of the experimental measurement, the fiber is bent in a U-shape and immersed in a liquid. The core and cladding are 240 microns and 250 microns, respectively. The intensity speckle field is then captured by a CCD camera in digital image format and processed by the computer with a Matlab program. The portion of fiber exposed to the disturbance of the liquid is located 2 meters before the exit of the fiber. The portion of the fiber in contact with the liquid is curved with a radius of 2 mm.

  1. Measurement of air refractive index fluctuation based on interferometry with two different reference cavity lengths.

    PubMed

    Chen, Qianghua; Luo, Huifu; Wang, Sumei; Wang, Feng; Chen, Xinhua

    2012-09-01

    A measurement method based on interferometry with two different reference cavity lengths is presented and applied in air refractive index measurement in which the two cavity lengths and a laser wavelength are combined to generate two wavelength equivalents of cavity. Corresponding calculation equations are derived, and the optical path configuration is designed, which is inspired by the traditional synthetic wavelength method. Theoretical analyses indicate that the measurement uncertainty of the determined index of refraction is about 2.310(-8), which is mainly affected by the length precision of the long vacuum cavity and the ellipticity of polarization components of the dual-frequency laser, and the range of nonambiguity is 3.010(-5), which is decided by the length difference of the two cavities. Experiment results show that the accuracy of air refractive index measurement is better than 5.010(-8) when the laboratory conditions changes slowly. The merit of the presented method is that the classical refractometry can be also used without evacuation of the gas cavity during the experiment. Furthermore, the application of the traditional synthetic wavelength method may be extended by using the wavelength equivalents of cavity, any value of which can be easily acquired by changing cavity length rather than using actual wavelengths whose number is limited. PMID:22945157

  2. Extremely high-accuracy correction of air refractive index using two-colour optical frequency combs.

    PubMed

    Wu, Guanhao; Takahashi, Mayumi; Arai, Kaoru; Inaba, Hajime; Minoshima, Kaoru

    2013-01-01

    Optical frequency combs have become an essential tool for distance metrology, showing great advantages compared with traditional laser interferometry. However, there is not yet an appropriate method for air refractive index correction to ensure the high performance of such techniques when they are applied in air. In this study, we developed a novel heterodyne interferometry technique based on two-colour frequency combs for air refractive index correction. In continuous 500-second tests, a stability of 1.0 10(-11) was achieved in the measurement of the difference in the optical distance between two wavelengths. Furthermore, the measurement results and the calculations are in nearly perfect agreement, with a standard deviation of 3.8 10(-11) throughout the 10-hour period. The final two-colour correction of the refractive index of air over a path length of 61 m was demonstrated to exhibit an uncertainty better than 1.4 10(-8), which is the best result ever reported without precise knowledge of environmental parameters. PMID:23719387

  3. Development of High Refractive Index Poly(thiophene) for 3-D Organic Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Stephen; Jin, Shi; Graham, Matthew; Bunning, Timothy

    2005-03-01

    Currently, no polymers have a sufficiently high refractive index to open a complete photonic band gap (PBG) in the commonly used inverse opal structure. Poly(thiophene) (PT) is predicted to have a high enough refractive index, but experimental values have been significantly less then those predicted. To reconcile this discrepancy, the electro-polymerization of thiophene has been optimized. The resulting poly(thiophene) (PT) films had improved structural regularity, and conjugation length. This translated into an elevated refractive index, as measured by Variable Angle Spectrographic Ellipsometry, which was sufficient to open a complete PBG. The next step to realizing an organic 3-D PC was to create high quality opal templates through which the PT could be polymerized. Colloidal crystallization of monodisperse spheres was used to fabricate the templates, while a novel nano-mechnical annealing technique was used to perfect the crystal structure. Taken together these developments offer the opportunity for the first time to make an organic 3-D PC with a complete PBG.

  4. Lattice and electronic contributions to the refractive index of CuWO₄

    SciTech Connect

    Ruiz-Fuertes, J.; Pellicer-Porres, J.; Segura, A.; Rodríguez-Hernández, P.; Muñoz, A.

    2014-09-14

    We report an investigation of the refractive index dispersion and anisotropy in CuWO₄ by means of interference measurements in two extinction directions from mid infrared to the visible region of the energy spectrum. The analysis of the refractive index dispersion yields ϵ(∞)=4.5(1) for light polarization parallel to the c-axis and ϵ(∞)=5.3(1) with respect to the other extinction axis. In addition, we report reflectance measurements carried out from the far infrared to the near ultraviolet to study the lattice and electronic contributions to the refractive index of CuWO₄. We have determined the wavenumbers of nine infrared active lattice modes and compared them with previous ab initio calculations. The value of the Penn gap, 7eV, as well as the origin of a structure observed at 4.4 eV in the reflectance spectrum, is discussed in the context of the CuWO₄ electronic structure.

  5. Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range.

    PubMed

    Wu, Xiaojun; Zhou, Chun; Huang, Wenqian Ronny; Ahr, Frederike; Krtner, Franz X

    2015-11-16

    Optical rectification with tilted pulse fronts in lithium niobate crystals is one of the most promising methods to generate terahertz (THz) radiation. In order to achieve higher optical-to-THz energy efficiency, it is necessary to cryogenically cool the crystal not only to decrease the linear phonon absorption for the generated THz wave but also to lengthen the effective interaction length between infrared pump pulses and THz waves. However, the refractive index of lithium niobate crystal at lower temperature is not the same as that at room temperature, resulting in the necessity to re-optimize or even re-build the tilted pulse front setup. Here, we performed a temperature dependent measurement of refractive index and absorption coefficient on a 6.0 mol% MgO-doped congruent lithium niobate wafer by using a THz time-domain spectrometer (THz-TDS). When the crystal temperature was decreased from 300 K to 50 K, the refractive index of the crystal in the extraordinary polarization decreased from 5.05 to 4.88 at 0.4 THz, resulting in ~1 change for the tilt angle inside the lithium niobate crystal. The angle of incidence on the grating for the tilted pulse front setup at 1030 nm with demagnification factor of -0.5 needs to be changed by 3. The absorption coefficient decreased by 60% at 0.4 THz. These results are crucial for designing an optimum tilted pulse front setup based on lithium niobate crystals. PMID:26698455

  6. Performance limits to the operation of nanoplasmonic chemical sensors: noise-equivalent refractive index and detectivity

    NASA Astrophysics Data System (ADS)

    Jaksic, Zoran; Jaksic, Olga; Matovic, Jovan

    2009-04-01

    We considered figures of merit for chemical and biological sensors based on plasmonic structures and utilizing adsorption/desorption mechanism. The operation of these devices in general is limited by noise determining the minimum detectable refractive-index change. We dedicated our work to the intrinsic noise mechanisms connected with the plasmonic process itself. In contrast, most of the available literature is almost exclusively dedicated to the external noise sources (illumination source and photodetector). Reviewing the refractive-index fluctuations caused by thermal, adsorption-desorption and 1/f noise, we observed a striking analogy between the qualitative behavior of noise in (nano)plasmonic devices and that in semiconductor infrared detectors. The power spectral densities for noise in both of these have an almost identical shape; the adsorption-desorption noise corresponds to generation-recombination processes in detectors, while the other two mechanisms exist in the both types of the devices. Thus the large and mature existing apparatus for infrared detector noise analysis may be applied to the plasmonic sensors. Based on the observed analogy, we formulated the noise-equivalent refractive-index and the specific detectivity as the figures of merit to analyze the ultimate performance of plasmon sensors. The approach is valid for conventional surface plasmon resonance sensors, but also for nanoplasmonic and metamaterial-based devices.

  7. Accurate in situ measurement of complex refractive index and particle size in intralipid emulsions

    NASA Astrophysics Data System (ADS)

    Dong, Miao L.; Goyal, Kashika G.; Worth, Bradley W.; Makkar, Sorab S.; Calhoun, William R.; Bali, Lalit M.; Bali, Samir

    2013-08-01

    A first accurate measurement of the complex refractive index in an intralipid emulsion is demonstrated, and thereby the average scatterer particle size using standard Mie scattering calculations is extracted. Our method is based on measurement and modeling of the reflectance of a divergent laser beam from the sample surface. In the absence of any definitive reference data for the complex refractive index or particle size in highly turbid intralipid emulsions, we base our claim of accuracy on the fact that our work offers several critically important advantages over previously reported attempts. First, our measurements are in situ in the sense that they do not require any sample dilution, thus eliminating dilution errors. Second, our theoretical model does not employ any fitting parameters other than the two quantities we seek to determine, i.e., the real and imaginary parts of the refractive index, thus eliminating ambiguities arising from multiple extraneous fitting parameters. Third, we fit the entire reflectance-versus-incident-angle data curve instead of focusing on only the critical angle region, which is just a small subset of the data. Finally, despite our use of highly scattering opaque samples, our experiment uniquely satisfies a key assumption behind the Mie scattering formalism, namely, no multiple scattering occurs. Further proof of our method's validity is given by the fact that our measured particle size finds good agreement with the value obtained by dynamic light scattering.

  8. Blood pH optrode based on evanescent waves and refractive index change

    NASA Astrophysics Data System (ADS)

    Hammarling, Krister; Hilborn, Jns; Nilsson, Hans-Erik; Manuilskiy, Anatoliy

    2014-02-01

    Sensing pH in blood with an silica multimode optical fiber. This sensor is based on evanescent wave absorption and measures the change of the refractive index and absorption in a cladding made of a biocompatible Polymer. In contrast to many existing fiber optical sensors which are based upon different dyes or florescent material to sense the pH, here presents a solution where a part of the cladding is replaced with a Poly (?-amino ester) made of 1.4-Butanediol diacrylate, Piperazine, and Trimethylolpropane Triacrylate. Piperazine has the feature of changing its volume by swelling or shrinking in response to the pH level. This paper utilizes this dimension effect and measure the refractive index and the absorption of the cladding in respect to different pH-levels. The alteration of refractive index also causes a change in the absorption and therefore the output power changes as a function of the pH level. The sensor is sensitive to pH in a wide spectral range and light absorbency can be observed for wavelengths ranging from UV to far IR.

  9. Zoned near-zero refractive index fishnet lens antenna: Steering millimeter waves

    SciTech Connect

    Pacheco-Peña, V. Orazbayev, B. Beaskoetxea, U. Beruete, M.; Navarro-Cía, M.

    2014-03-28

    A zoned fishnet metamaterial lens is designed, fabricated, and experimentally demonstrated at millimeter wavelengths to work as a negative near-zero refractive index lens suitable for compact lens antenna configurations. At the design frequency f = 56.7 GHz (λ{sub 0} = 5.29 mm), the zoned fishnet metamaterial lens, designed to have a focal length FL = 9λ{sub 0}, exhibits a refractive index n = −0.25. The focusing performance of the diffractive optical element is briefly compared with that of a non-zoned fishnet metamaterial lens and an isotropic homogeneous zoned lens made of a material with the same refractive index. Experimental and numerically-computed radiation diagrams of the fabricated zoned lens are presented and compared in detail with that of a simulated non-zoned lens. Simulation and experimental results are in good agreement, demonstrating an enhancement generated by the zoned lens of 10.7 dB, corresponding to a gain of 12.26 dB. Moreover, beam steering capability of the structure by shifting the feeder on the xz-plane is demonstrated.

  10. Refractive index sensing performance analysis of photonic crystal containing graphene based on optical Tamm state

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Dong, Jing; Liu, Teng; Zhu, Qiguang; Chen, Weidong

    2016-01-01

    A photonic crystal’s refractive index sensor is proposed based on the photonic crystal (PC) optical properties and the surface wave resonance principle. The optical Tamm state existing at the interface between one-dimensional (1D) PCs and the metal layer can overcome the disadvantage of the surface plasmon resonance (SPR) sensor in which the incident light can only be TM polarized light. The resonant wavelength can be changed by adjusting the optical parameters of the PC. Through coating the metal surface with graphene, the resolution and sensitivity of the sensor can be improved obviously. The relationship model between the graphene parameters and the reflectivity is established by analyzing the reflective properties of the graphene. In the numerical simulation, the graphene layer is optimized to improve the refractive index sensing properties. The numerical simulation results show that the quality factor (Q value) can attain to 1418.2 and the sensitivity is about 1178.6 nm RIU‑1, which can demonstrate the effectiveness of the senor structure and provide some theoretical references for the design of the refractive index sensors with high Q value and sensitivity.

  11. Prediction of an extremely large nonlinear refractive index for crystals at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Dolgaleva, Ksenia; Materikina, Daria V.; Boyd, Robert W.; Kozlov, Sergei A.

    2015-08-01

    We develop a simple analytical model for calculating the vibrational contribution to the nonlinear refractive index n2 (Kerr coefficient) of a crystal in terms of known crystalline parameters such as the linear refractive index, the coefficient of thermal expansion, the atomic density, and the reduced mass and the natural oscillation frequency of the vibrational modes of the crystal lattice. We show that the value of this contribution in the terahertz spectral region can exceed the value of the nonlinear refractive index n2 in the visible and near-IR spectral ranges (which is largely electronic in origin) by several orders of magnitude. For example, for crystal quartz the value of the Kerr coefficient in the low-frequency limit is n2=2.2 ×10-9 esu or, equivalently, 4.4 ×10-16m2 /W, which is very much larger than its value of 3 ×10-20m2 /W in the visible range. Furthermore, we present an analysis of the dispersion of n2 in the terahertz spectral range and show that even larger values of n2 occur at frequencies close to the vibrational resonances.

  12. Determining the refractive index of shocked [100] lithium fluoride to the limit of transmissibility

    SciTech Connect

    Rigg, P. A. Scharff, R. J.; Hixson, R. S.; Knudson, M. D.

    2014-07-21

    Lithium fluoride (LiF) is a common window material used in shock- and ramp-compression experiments because it displays a host of positive attributes in these applications. Most commonly, it is used to maintain stress at an interface and velocimetry techniques are used to record the particle velocity at that interface. In this application, LiF remains transparent to stresses up to 200?GPa. In this stress range, LiF has an elastic-plastic response with a very low (<0.5?GPa) elastic precursor and exhibits no known solid-solid phase transformations. However, because the density dependence of the refractive index of LiF does not follow the Gladstone-Dale relation, the measured particle velocity at this interface is not the true particle velocity and must be corrected. For that reason, the measured velocity is often referred to as the apparent velocity in these types of experiments. In this article, we describe a series of shock-compression experiments that have been performed to determine the refractive index of LiF at the two most commonly used wavelengths (532?nm and 1550?nm) between 35 and 200?GPa to high precision. A modified form of the Gladstone-Dale relation was found to work best to fit the determined values of refractive index. In addition, we provide a direct relationship between the apparent and true particle velocity to correct experimentally obtained wave profiles by others using these velocimetry techniques.

  13. Experimental study of liquid refractive index sensing based on a U-shaped optical fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi; Yan, Haitao; Li, Liben; Wang, Ming

    2013-12-01

    A U-shaped optical fiber sensing system designed to measure the refractive index of liquid had been proposed. The sensing mechanism of U-shaped optical fiber was discussed. A general single-mode fiber was bent into U-shaped and partially cladding of U-shaped fiber was corroded by HF acid buffer solution. Powers of different diameters of U-shaped fibers had been measured by many experiments. The results showed that the diameter of U-shaped fiber cladding 40 ?m and the diameter of U-shaped was 1 cm were suitable to measure liquid refractive index. Then, this U-shaped optical fiber was immersed in liquid, such as pure water, ethanol, acetone and isopropanol, respectively. The evanescent field of the U-shaped fiber should be modulated by the liquid. The optical signal in the U-shaped fiber was measured with the optical spectrum analyzers(OSA). Finally, the experimental results were analyzed, and the spectra in the air was selected as a reference. The relative intensity was obtained for the different liquid. These results showed that the relative intensity of the liquid had a good linear relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low cost, and it can also be applied in measuring the level of liquid.

  14. Correction of stain variations in nuclear refractive index of clinical histology specimens.

    PubMed

    Uttam, Shikhar; Bista, Rajan K; Hartman, Douglas J; Brand, Randall E; Liu, Yang

    2011-11-01

    For any technique to be adopted into a clinical setting, it is imperative that it seamlessly integrates with well-established clinical diagnostic workflow. We recently developed an optical microscopy technique-spatial-domain low-coherence quantitative phase microscopy (SL-QPM) that can extract the refractive index of the cell nucleus from the standard histology specimens on glass slides prepared via standard clinical protocols. This technique has shown great potential in detecting cancer with a better sensitivity than conventional pathology. A major hurdle in the clinical translation of this technique is the intrinsic variation among staining agents used in histology specimens, which limits the accuracy of refractive index measurements of clinical samples. In this paper, we present a simple and easily generalizable method to remove the effect of variations in staining levels on nuclear refractive index obtained with SL-QPM. We illustrate the efficacy of our correction method by applying it to variously stained histology samples from animal model and clinical specimens. PMID:22112118

  15. Tunable fiber laser based on the refractive index characteristic of MMI effects

    NASA Astrophysics Data System (ADS)

    Ma, Lin; Qi, Yanhui; Kang, Zexin; Bai, Yunlong; Jian, Shuisheng

    2014-04-01

    A tunable erbium-doped all-fiber laser has been demonstrated. This tunable laser is based on a tunable fiber filter using the refractive index characteristics of multimode interference effects. A thinner no-core fiber with a diameter of 104 ?m is used to fabricate the tunable fiber filter. The joint point of the thinner no-core fiber with SMF is a taper, which improves its sensitivity for refractive index changes. The filter exhibits a very sensitive response to the change of the environmental refractive index, which is about 1000 nm/RIU in the RI range from 1.418 to 1.427. The tunable fiber laser based on the filter achieved a tunability of 32 nm, with the wavelength tuned from 1532 nm to 1564 nm covering the full C-band. The 3 dB bandwidth of the tunable laser is less than 0.02 nm with the signal-to-noise ratio of about 40 dB.

  16. The role of macromolecular crowding in the evolution of lens crystallins with high molecular refractive index

    NASA Astrophysics Data System (ADS)

    Zhao, Huaying; Magone, M. Teresa; Schuck, Peter

    2011-08-01

    Crystallins are present in the lens at extremely high concentrations in order to provide transparency and generate a high refractive power of the lens. The crystallin families prevalent in the highest density lens tissues are γ-crystallins in vertebrates and S-crystallins in cephalopods. As shown elsewhere, in parallel evolution, both have evolved molecular refractive index increments 5-10% above those of most proteins. Although this is a small increase, it is statistically very significant and can be achieved only by very unusual amino acid compositions. In contrast, such a molecular adaptation to aid in the refractive function of the lens did not occur in crystallins that are preferentially located in lower density lens tissues, such as vertebrate α-crystallin and taxon-specific crystallins. In the current work, we apply a model of non-interacting hard spheres to examine the thermodynamic contributions of volume exclusion at lenticular protein concentrations. We show that the small concentration decrease afforded by the higher molecular refractive index increment of crystallins can amplify nonlinearly to produce order of magnitude differences in chemical activities, and lead to reduced osmotic pressure and the reduced propensity for protein aggregation. Quantitatively, this amplification sets in only at protein concentrations as high as those found in hard lenses or the nucleus of soft lenses, in good correspondence to the observed crystallin properties in different tissues and different species. This suggests that volume exclusion effects provide the evolutionary driving force for the unusual refractive properties and the unusual amino acid compositions of γ-crystallins and S-crystallins.

  17. Refractive index gradient measurement across the thickness of a dielectric film by the prism coupling method

    SciTech Connect

    Sokolov, Viktor I; Panchenko, Vladislav Ya; Seminogov, V N

    2012-08-31

    A method is proposed for measuring the refractive index gradient n(z) in nonuniformly thick dielectric films. The method is based on the excitation of waveguide modes in a film using the prism coupling technique and on the calculation of n(z) and film thickness H{sub f} with the help of the angular positions of the TE or TM modes. The method can be used for an arbitrary shape of the index modulation over the film thickness in the limit of a small gradient [{Delta} n(z)/n(z) || 1]. (laser applications and other topics in quantum electronics)

  18. All-dielectric three-dimensional broadband Eaton lens with large refractive index range

    SciTech Connect

    Yin, Ming; Yong Tian, Xiao Ling Wu, Ling; Chen Li, Di

    2014-03-03

    We proposed a method to realize three-dimensional (3D) gradient index (GRIN) devices requiring large refractive index (RI) range with broadband performance. By combining non-resonant GRIN woodpile photonic crystals structure in the metamaterial regime with a compound liquid medium, a wide RI range (16.32) was fulfilled flexibly. As a proof-of-principle for the low-loss and non-dispersive method, a 3D Eaton lens was designed and fabricated based on 3D printing process. Full-wave simulation and experiment validated its omnidirectional wave bending effects in a broad bandwidth covering Ku band (12?GHz18?GHz)

  19. Investigation of the errors of thickness and refractive index in manufacturing Gires-Tournois interferometer negative-dispersion mirrors

    NASA Astrophysics Data System (ADS)

    Wang, Yan-zhi; Shao, Jian-da; Zhang, Wei-li; Wei, Chao-yang; Huang, Jian-bin; Jin, Yun-xia; Fan, Zheng-xiu

    2009-10-01

    Gires-Tournois interferometer mirrors are designed and deposited. Because of deviation between the measured group-delay dispersion and the designed character, based on the measured layers' thickness, we fit group-delay dispersion measured values to analyse the errors produced during the deposition. When considering thickness deviation and the refractive index inhomogeneity, the fitted curve has a good agreement with the measurement result. Therefore, thickness errors and refractive index inhomogeneity are the main factors in manufacturing the Gires-Tournois interferometer mirrors. At the same time, the fitted actual manufactured thickness of every layer and the degree of refractive index inhomogeneity are obtained from the fitted curve.

  20. Multiple scattering of matter waves: An analytic model of the refractive index for atomic and molecular gases

    SciTech Connect

    Lemeshko, Mikhail; Friedrich, Bretislav

    2010-08-15

    We present an analytic model of the refractive index for matter waves propagating through atomic or molecular gases. The model, which combines the Wentzel-Kramers-Brillouin (WKB) treatment of the long-range attraction with the Fraunhofer model treatment of the short-range repulsion, furnishes a refractive index in compelling agreement with recent experiments of Jacquey et al. [Phys. Rev. Lett. 98, 240405 (2007)] on Li atom matter waves passing through dilute noble gases. We show that the diffractive contribution, which arises from scattering by a two-dimensional 'hard core' of the potential, is essential for obtaining a correct imaginary part of the refractive index.

  1. Enhanced light extraction of Bi3Ge4O12 scintillator by graded-refractive-index antireflection coatings

    NASA Astrophysics Data System (ADS)

    Tong, Fei; Liu, Bo; Chen, Hong; Zhu, Zhichao; Gu, Mu

    2013-08-01

    A three-layer graded-refractive-index antireflection coating is designed and prepared on the one surface of the Bi3Ge4O12 scintillator by sol-gel technology. The emission intensity of the Bi3Ge4O12 with a graded-refractive-index antireflection coating exhibits a broadband and omnidirectional enhancement of 15.9% compared with the reference sample without coating. This significant enhancement is attributed to the decrease of Fresnel reflection, which is consistent with the measurement of transmission spectra. Additionally, it is evident that the graded-refractive-index coating is superior to the conventional quarter-wave coating due to the omnidirectionality advantage.

  2. Frequency modulation and compression of optical pulses in an optical fibre with a travelling refractive-index wave

    NASA Astrophysics Data System (ADS)

    Zolotovskii, I. O.; Lapin, V. A.; Sementsov, D. I.

    2016-01-01

    We have studied the conditions for spectral broadening, frequency modulation and compression (both temporal and spectral) of Gaussian pulses propagating in a fibre with a travelling refractive-index wave. Analytical expressions have been derived for the dependences of pulse duration, chirp and spectral width on the distance travelled through the fibre, parameters of the fibre and radiation launched into it. Based on the numerical analysis we have studied the behaviour of these characteristics by changing the coefficient of the refractive-index modulation and other parameters of the travelling refractive-index wave.

  3. Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing.

    PubMed

    Liao, C R; Hu, T Y; Wang, D N

    2012-09-24

    We demonstrate a fiber in-line Fabry-Perot interferometer cavity sensor for refractive index measurement. The interferometer cavity is formed by drilling a micro-hole at the cleaved fiber end facet, followed by fusion splicing. A micro-channel is inscribed by femtosecond laser micromachining to vertically cross the cavity to allow liquid to flow in. The refractive index sensitivity obtained is ~994 nm/RIU (refractive index unit). Such a device is simple in configuration, easy for fabrication and reliable in operation due to extremely low temperature cross sensitivity of ~4.8 10(-6) RIU/C. PMID:23037431

  4. Refractive index sensor based on combination of tilted fiber Bragg grating and waist-enlarged fusion bitaper

    NASA Astrophysics Data System (ADS)

    Liu, Xiaohang; Zheng, Jie; Yang, Jingyi; Li, Yi; Dong, Xinyong

    2015-12-01

    Refractive index measurement by using the combination of a tilted fiber Bragg grating (TFBG) and a waist-enlarged fusion bitaper (WEFBT) is proposed and demonstrated. The both devices can couple light between core and cladding modes with coupling coefficients depending on ambient refractive index. It is found that the proposed refractive index sensor offers two measurement ranges respectively from 1.333 to 1.428 and from 1.383 to 1.453 when different sensing segment is used, in addition to advantages of reflection operation mode and intensity-modulated measurement.

  5. Engineering of parallel plasmonic-photonic interactions for on-chip refractive index sensors

    NASA Astrophysics Data System (ADS)

    Lin, Linhan; Zheng, Yuebing

    2015-07-01

    Ultra-narrow linewidth in the extinction spectrum of noble metal nanoparticle arrays induced by the lattice plasmon resonances (LPRs) is of great significance for applications in plasmonic lasers and plasmonic sensors. However, the challenge of sustaining LPRs in an asymmetric environment greatly restricts their practical applications, especially for high-performance on-chip plasmonic sensors. Herein, we fully study the parallel plasmonic-photonic interactions in both the Au nanodisk arrays (NDAs) and the core/shell SiO2/Au nanocylinder arrays (NCAs). Different from the dipolar interactions in the conventionally studied orthogonal coupling, the horizontal propagating electric field introduces the out-of-plane ``hot spots'' and results in electric field delocalization. Through controlling the aspect ratio to manipulate the ``hot spot'' distributions of the localized surface plasmon resonances (LSPRs) in the NCAs, we demonstrate a high-performance refractive index sensor with a wide dynamic range of refractive indexes ranging from 1.0 to 1.5. Both high figure of merit (FOM) and high signal-to-noise ratio (SNR) can be maintained under these detectable refractive indices. Furthermore, the electromagnetic field distributions confirm that the high FOM in the wide dynamic range is attributed to the parallel coupling between the superstrate diffraction orders and the height-induced LSPR modes. Our study on the near-field ``hot-spot'' engineering and far-field parallel coupling paves the way towards improved understanding of the parallel LPRs and the design of high-performance on-chip refractive index sensors.Ultra-narrow linewidth in the extinction spectrum of noble metal nanoparticle arrays induced by the lattice plasmon resonances (LPRs) is of great significance for applications in plasmonic lasers and plasmonic sensors. However, the challenge of sustaining LPRs in an asymmetric environment greatly restricts their practical applications, especially for high-performance on-chip plasmonic sensors. Herein, we fully study the parallel plasmonic-photonic interactions in both the Au nanodisk arrays (NDAs) and the core/shell SiO2/Au nanocylinder arrays (NCAs). Different from the dipolar interactions in the conventionally studied orthogonal coupling, the horizontal propagating electric field introduces the out-of-plane ``hot spots'' and results in electric field delocalization. Through controlling the aspect ratio to manipulate the ``hot spot'' distributions of the localized surface plasmon resonances (LSPRs) in the NCAs, we demonstrate a high-performance refractive index sensor with a wide dynamic range of refractive indexes ranging from 1.0 to 1.5. Both high figure of merit (FOM) and high signal-to-noise ratio (SNR) can be maintained under these detectable refractive indices. Furthermore, the electromagnetic field distributions confirm that the high FOM in the wide dynamic range is attributed to the parallel coupling between the superstrate diffraction orders and the height-induced LSPR modes. Our study on the near-field ``hot-spot'' engineering and far-field parallel coupling paves the way towards improved understanding of the parallel LPRs and the design of high-performance on-chip refractive index sensors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03159a

  6. Zero Phase Delay in Negative-refractive-index Photonic Crystal Superlattices

    SciTech Connect

    Stein, A.; Kocaman, S.; Aras, M.S.; Hsieh, P.-C. McMillan, J.F.; Biris, C.G.; Panoiu, N.C.; Yu, M.B.; Kwong, D.L.; Wong, C.W.

    2011-08-01

    We show that optical beams propagating in path-averaged zero-index photonic crystal superlattices can have zero phase delay. The nanofabricated superlattices consist of alternating stacks of negative index photonic crystals and positive index homogeneous dielectric media, where the phase differences corresponding to consecutive primary unit cells are measured with integrated Mach-Zehnder interferometers. These measurements demonstrate that at path-averaged zero-index frequencies the phase accumulation remains constant and equal to zero despite the increase in the physical path length. We further demonstrate experimentally that these superlattice zero- bandgaps remain invariant to geometrical changes of the photonic structure and have a center frequency which is deterministically tunable. The properties of the zero- gap frequencies, optical phase, and effective refractive indices are well described by detailed experimental measurements, rigorous theoretical analysis, and comprehensive numerical simulations.

  7. Engineering of parallel plasmonic-photonic interactions for on-chip refractive index sensors.

    PubMed

    Lin, Linhan; Zheng, Yuebing

    2015-07-28

    Ultra-narrow linewidth in the extinction spectrum of noble metal nanoparticle arrays induced by the lattice plasmon resonances (LPRs) is of great significance for applications in plasmonic lasers and plasmonic sensors. However, the challenge of sustaining LPRs in an asymmetric environment greatly restricts their practical applications, especially for high-performance on-chip plasmonic sensors. Herein, we fully study the parallel plasmonic-photonic interactions in both the Au nanodisk arrays (NDAs) and the core/shell SiO2/Au nanocylinder arrays (NCAs). Different from the dipolar interactions in the conventionally studied orthogonal coupling, the horizontal propagating electric field introduces the out-of-plane "hot spots" and results in electric field delocalization. Through controlling the aspect ratio to manipulate the "hot spot" distributions of the localized surface plasmon resonances (LSPRs) in the NCAs, we demonstrate a high-performance refractive index sensor with a wide dynamic range of refractive indexes ranging from 1.0 to 1.5. Both high figure of merit (FOM) and high signal-to-noise ratio (SNR) can be maintained under these detectable refractive indices. Furthermore, the electromagnetic field distributions confirm that the high FOM in the wide dynamic range is attributed to the parallel coupling between the superstrate diffraction orders and the height-induced LSPR modes. Our study on the near-field "hot-spot" engineering and far-field parallel coupling paves the way towards improved understanding of the parallel LPRs and the design of high-performance on-chip refractive index sensors. PMID:26133011

  8. Physicochemical and catalytic properties of Au nanorods micro-assembled in solvents of varying dipole moment and refractive index

    SciTech Connect

    Kaur, Rupinder; Pal, Bonamali

    2015-02-15

    Highlights: • Physicochemical activities of Au nanorods in water largely differ from organic solvents. • Au nanorods agglomeration increased with dipole moments of different polar solvents. • Refractive indexes of Au nanorods dispersion in various polar solvents are enhanced. • Electrokinetics significantly altered depending on agglomerated size of Au nanorods. • Catalysis or co-catalysis activity is varied as per the extent of Au nanorods coagulation. - Abstract: This paper deals with the impact of dipole moment (1.66–3.96 D) and refractive index (1.333–1.422) of the dispersion solvent on the plasmon absorption, surface charge, zeta potential, and adsorption properties of Au nanorods (AuNRs). AuNRs (length ≈ 53 nm and width ≈ 20 nm) undergo agglomeration (size 50–180 nm) with increase in the dipole moment of solvent (iPrOH < MeOH < DMF < DMSO). Whereas, no such coagulation occurs in H{sub 2}O and CCl{sub 4} suspension as confirmed by DLS and TEM size distribution. The electrostatic interaction of AuNRs with its surface adsorbed solvent dipoles leads to alteration of the their ionic state, absolute electronic charge and zeta potential (+49.79 mV in H{sub 2}O, +8.99 mV in DMF and −4.65 mV in MeOH dispersion) to a greater extent. This interaction distinctly modifies the adsorption behavior of polar molecules like p-nitrophenol and salicylic acid on AuNRs surface, as evidenced by the measured changes in their electro-kinetic parameters. As a result, we observe a substantial difference in catalytic and co-catalytic activities of AuNRs dispersed in various solvents as mentioned above because the catalytic properties of AuNRs are strongly dependent on the type of solvent in which they are dispersed.

  9. Asymmetric Mach-Zehnder interferometers without an interaction window in polymer foils for refractive index sensing.

    PubMed

    Hofmann, Meike; Xiao, Yanfen; Sherman, Stanislav; Gleissner, Uwe; Schmidt, Thomas; Zappe, Hans

    2016-02-10

    We report on the fabrication and characterization of integrated Mach-Zehnder interferometers in polymer foil without an interaction window. The interferometers are based on inverted rib waveguides, which allow single mode behavior even for waveguide widths larger than a few micrometers. The phase change between the two interferometer arms upon a refractive index change of the analyte that serves as the upper cladding is generated by the asymmetricity of the two interferometer arms. A difference of the waveguide width in the straight part of the interferometer leads to different effective refractive indices and thus to a change in the interference signal. We show in small scale the process chain, which is compatible with a cost-effective roll-to-roll fabrication process. For a proof of principle we apply deionized water and a glucose solution as analytes to the sensor foils and detect the transmitted intensity as a measure of the induced phase change. A detection limit of 310-3 refractive index units is reached for homogeneous sensing at a total system length of 9.3 mm and a total waveguide core thickness of 3 ?m. PMID:26906387

  10. High Refractive Index Poly(thiophene) for 3-D Organic Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Graham, Matthew; Cheng, Stephen; Jin, Shi; Bunning, Timothy

    2005-03-01

    Traditional polymers have refractive indices too low to be used in high dimensional photonic crystals (PC). Poly(thiophene) (PT) is predicted to have a high enough refractive index to open a complete photonic band gap (PBG) in the commonly used inverse opal structure for 3-D PC, but experimental values have been significantly less than the prediction. To reconcile this discrepancy, the electro-polymerization of thiophene has been optimized with respect to reactant concentration, additives, and temperature. The resulting PT films had a significantly elevated refractive index, as measured by Variable Angle Spectrographic Ellipsometry, which was sufficient to open a complete PBG. The next step in fabricating an organic 3-D PC is to create high quality opal templates through which the PT could be polymerized. Colloidal crystallization of monodisperse polystyrene spheres was used to fabricate the templates, while a novel nano-mechnical annealing technique was used to perfect the crystal structure. Taken together these developments offer the opportunity to make a completely organic 3-D PC with a complete PBG.

  11. Infrared Spectra, Index of Refraction, and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere

    NASA Technical Reports Server (NTRS)

    Moore, Marla; Ferrante, Robert; Moore, William; Hudson, Reggie

    2010-01-01

    Spectra and optical constants of nitrite ices known or suspected to be in Titan's atmosphere are presented from 2.5 to 200 microns (4000 to 50 per cm ). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan's winter pole. Ices studied include: HCN, hydrogen cyanide; C2N2, cyanogen; CH3CN, acetonitrile; C 2H5CN, propionitrile; and HC3N, cyanoacetylene. For each of these molecules we report new measurements of the index of refraction, n, determined in both the amorphous- and crystallinephase at 670 nm. Spectra were measured and optical constants were calculated for each nitrite at a variety of temperatures including 20, 35, 50, 75, 95, and 110 K, in the amorphous- and crystalline-phase. This laboratory effort uses a dedicated FTIR spectrometer to record transmission spectra of thin-film ice samples. Laser interference is used to measure film thickness during condensation onto a transparent cold window attached to the tail section of a closed-cycle helium cryostat. Optical constants, real (n) and imaginary (k) refractive indices, are determined using Kramers-Kronig (K-K) analysis. Our calculation reproduces the complete spectrum, including all interference effects. Index of refraction measurements are made in a separate dedicated FTIR spectrometer where interference deposit fringes are measured using two 670 nm lasers at different angles to the ice substrate. A survey of these new measurements will be presented along with a discussion of their validation, errors, and application to Titan data.

  12. Spatial Resolution and Refractive Index Contrast of Resonant Photonic Crystal Surfaces for Biosensing

    PubMed Central

    Triggs, G. J.; Fischer, M.; Stellinga, D.; Scullion, M. G.; Evans, G. J. O.; Krauss, T. F.

    2015-01-01

    By depositing a resolution test pattern on top of a Si3N4 photonic crystal resonant surface, we have measured the dependence of spatial resolution on refractive index contrast ?n. Our experimental results and finite-difference time-domain (FDTD) simulations at different refractive index contrasts show that the spatial resolution of our device reduces with reduced contrast, which is an important consideration in biosensing, where the contrast may be of order 10?2. We also compare 1-D and 2-D gratings, taking into account different incidence polarizations, leading to a better understanding of the excitation and propagation of the resonant modes in these structures, as well as how this contributes to the spatial resolution. At ?n = 0.077, we observe resolutions of 2 and 6 ?m parallel to and perpendicular to the grooves of a 1-D grating, respectively, and show that for polarized illumination of a 2-D grating, resolution remains asymmetrical. Illumination of a 2-D grating at 45 results in symmetric resolution. At very low index contrast, the resolution worsens dramatically, particularly for ?n < 0.01, where we observe a resolution exceeding 10 ?m for our device. In addition, we measure a reduction in the resonance linewidth as the index contrast becomes lower, corresponding to a longer resonant mode propagation length in the structure and contributing to the change in spatial resolution. PMID:26356353

  13. Design of acid-lead battery stage-of-charge detection system based on refractive index detection technology

    NASA Astrophysics Data System (ADS)

    Chen, Junyao; Yang, Kecheng; Xia, Min; Li, Lei; Zeng, Xianjiang

    2015-10-01

    Based on optical total reflection critical Angle method, we have designed a refractive index measurement system. It adopted a divergent light source and a CCD camera as the occurrence and receiver of the signal. The divergent light source sent out a bunch of tapered beam, exposure to the interface of optical medium and sulfuric acid solution. Light intensity reflected from the interface could be detected by the CCD camera and then sent to the embedded system. In the DSP embedded system, we could obtain the critical edge position through the light intensity distribution curve and converted it to critical angle. Through experiment, we concluded the relation between liquid refractive index and the critical angle edge position. In this system, the detecting precision of the refractive index of sulfuric acid solution reached 10-4. Finally, through the conversion of the refractive index and density, we achieved high accuracy online measurement of electrolyte density in lead-acid battery.

  14. Temperature field inside an absorbing-emitting semi-transparent slab at radiative equilibrium with variable spatial refractive index.

    NASA Astrophysics Data System (ADS)

    Abdallah, P. B.; Le Dez, V.

    2000-05-01

    The temperature field inside an absorbing-emitting slab of semi-transparent grey medium at radiative equilibrium has been determined with the help of a curved ray-tracing technique when the spatial variation of the refractive index in the medium is assumed to be linear. The integration of the radiative transfer equation has been carried out on the trajectories on which radiation propagates inside the medium, leading to the absorbed radiative energy at an internal point. For a linear refractive index, existence of totally reflected internal trajectories producing mirage effects have to be taken into account in the resolution of the radiative problem. Results obtained for different optical depths with low and strong gradients of refractive index display significant differences from the case of a constant refractive index.

  15. Surface plasmon resonance based fiber optic refractive index sensor utilizing silicon layer: Effect of doping

    NASA Astrophysics Data System (ADS)

    Bhatia, Priya; Gupta, , Banshi D.

    2013-01-01

    We present an experimental study on the surface plasmon resonance (SPR) based fiber optic refractive index sensor utilizing a high index silicon layer between a metal layer and sensing medium using the wavelength interrogation mode of operation. Both n- and p-type silicon have been used. For the metal layer, silver and gold have been used. For a given metal, experimental results predict higher sensitivity of the sensor for the n-type silicon than for the p-type silicon layer. Further, for a given type of silicon, the sensitivity for the gold coated probe is higher than that of the silver coated probe. Numerically, the sensitivity of the n-type silicon with silver as the metal layer is approximately 1.39 times higher than that of the p-type silicon. In the case of gold as the metal layer, the sensitivity of the n-type silicon is approximately 1.50 times that of the p-type silicon. Since the refractive index of both p-type and n-type silicon is the same it appears that the majority charge carriers in silicon play an important role in the sensitivity of the surface plasmon resonance based sensor. The charge carriers are either affecting the field in the analyte region or may be somehow affecting the propagation constant of the surface plasmon wave which is solely due to oscillation of free electrons in the metal layer. In addition, the sensitivity of only the metal coated probes is found to lie between their p-type and n-type silicon coated probes. This suggests that the effect of charge carriers on sensitivity is more than the refractive index of the silicon layer. The effects of charge carriers in silicon, electrons and holes appears to be opposite.

  16. TEACHING PHYSICS: Refractive index determination of materials on thin transparent substrates using ellipsometry

    NASA Astrophysics Data System (ADS)

    Lvesque, L.

    2000-09-01

    Ellipsometry techniques are often used in the microelectronics industry to monitor substrate cleanliness. The principle of ellipsometry is introduced briefly by describing what is involved when measuring transparent materials. This exercise helps in understanding why absorbing substrates are often used in the ellipsometry technique, without having to derive complicated equations. Moreover, the technique is presented in a simple way with a view to applying and reviewing the concepts of internal reflections occurring in a thin piece of material (substrate). Refractive index measurements of thin transparent substrates such as glass slides can be inaccurate when using ellipsometry because of multiple reflections occurring on both the top and bottom surfaces. Some measurements of the refractive indices of transparent substrates (glass slides) are presented and discussed.

  17. Direct measurement of the x-ray refractive index by Fresnel diffraction at a transparent edge.

    PubMed

    Gayer, C W; Hemmers, D; Stelzmann, C; Pretzler, G

    2013-05-01

    We demonstrate the feasibility of measuring x-ray refractive indices by transparent edge diffraction without recourse to the Kramers-Kronig relations. The method requires a coherent x-ray source, a transparent sample with a straight edge, and a high resolution x-ray detector. Here, we use the aluminum K? radiation originating from a laser-produced plasma to coherently illuminate the edge of thin aluminum and beryllium foils. The resulting diffraction patterns are recorded with an x-ray CCD camera. From least-squares fits of Fresnel diffraction modeling to the measured data we determine the refractive index of Al and Be at the wavelength of the Al K? radiation (0.834 nm, 1.49 keV). PMID:23632552

  18. A Highly Sensitive Fiber Optic Sensor Based on Two-Core Fiber for Refractive Index Measurement

    PubMed Central

    Guzmán-Sepúlveda, José Rafael; Guzmán-Cabrera, Rafael; Torres-Cisneros, Miguel; Sánchez-Mondragón, José Javier; May-Arrioja, Daniel Alberto

    2013-01-01

    A simple and compact fiber optic sensor based on a two-core fiber is demonstrated for high-performance measurements of refractive indices (RI) of liquids. In order to demonstrate the suitability of the proposed sensor to perform high-sensitivity sensing in a variety of applications, the sensor has been used to measure the RI of binary liquid mixtures. Such measurements can accurately determine the salinity of salt water solutions, and detect the water content of adulterated alcoholic beverages. The largest sensitivity of the RI sensor that has been experimentally demonstrated is 3,119 nm per Refractive Index Units (RIU) for the RI range from 1.3160 to 1.3943. On the other hand, our results suggest that the sensitivity can be enhanced up to 3485.67 nm/RIU approximately for the same RI range. PMID:24152878

  19. The Cryogenic, High-Accuracy, Refraction Measuring System (CHARMS): A New Facility for Cryogenic Infrared through Vacuum Far-Ultraviolet Refractive Index Measurements

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.

    2004-01-01

    The optical designs of future NASA infrared (IR) missions and instruments, such as the James Webb Space Telescope's (JWST) Near-Mixed Camera (NIRCam), will rely on accurate knowledge of the index of refraction of various IR optical materials at cryogenic temperatures. To meet this need, we have developed a Cryogenic, High-Accuracy Refraction Measuring System (CHARMS). In this paper we discuss the completion of the design and construction of CHARMS as well as the engineering details that constrained the final design and hardware implementation. In addition, we will present our first light, cryogenic, IR index of refraction data for LiF, BaF2, and CaF2, and compare our results to previously published data for these materials.

  20. SnO{sub 2} nanoparticles in silica: Nanosized tools for femtosecond-laser machining of refractive index patterns

    SciTech Connect

    Paleari, A.; Franchina, E.; Chiodini, N.; Lauria, A.; Bricchi, E.; Kazansky, P.G.

    2006-03-27

    We show that SnO{sub 2} nanoclusters in silica interact with ultrashort infrared laser pulses focused inside the material generating a hydrostatic compression and photoelastic response of the surrounding glass. This effect, together with the laser-induced nanocluster amorphization, gives rise to positive or negative refractive-index changes, up to 10{sup -2}, depending on the beam-power density. This result points out a wide tuning of the refractive index patterns obtainable in silica-based optical technology.

  1. An SPR-based sensor with an extremely large dynamic range of refractive index measurements in the visible region

    NASA Astrophysics Data System (ADS)

    Mishra, Akhilesh K.; Mishra, Satyendra K.; Verma, Rajneesh K.

    2015-11-01

    A promising GaP prism-based surface plasmon resonance sensor in the Kretschmann configuration with an extremely large dynamic range of refractive index detection is proposed. The prism base is coated with a gold layer and then a thin layer of silicon. The sensor is studied theoretically in terms of sensitivity and detection accuracy. The proposed sensor shows the potential of sensing media with a refractive index varying from gaseous to very dense liquid with appreciably high sensitivity.

  2. Fabrication quality analysis of a fiber optic refractive index sensor created by CO2 laser machining.

    PubMed

    Chen, Chien-Hsing; Yeh, Bo-Kuan; Tang, Jaw-Luen; Wu, Wei-Te

    2013-01-01

    This study investigates the CO2 laser-stripped partial cladding of silica-based optic fibers with a core diameter of 400 ?m, which enables them to sense the refractive index of the surrounding environment. However, inappropriate treatments during the machining process can generate a number of defects in the optic fiber sensors. Therefore, the quality of optic fiber sensors fabricated using CO2 laser machining must be analyzed. The results show that analysis of the fiber core size after machining can provide preliminary defect detection, and qualitative analysis of the optical transmission defects can be used to identify imperfections that are difficult to observe through size analysis. To more precisely and quantitatively detect fabrication defects, we included a tensile test and numerical aperture measurements in this study. After a series of quality inspections, we proposed improvements to the existing CO2 laser machining parameters, namely, a vertical scanning pathway, 4 W of power, and a feed rate of 9.45 cm/s. Using these improved parameters, we created optical fiber sensors with a core diameter of approximately 400 ?m, no obvious optical transmission defects, a numerical aperture of 0.52 0.019, a 0.886 Weibull modulus, and a 1.186 Weibull-shaped parameter. Finally, we used the optical fiber sensor fabricated using the improved parameters to measure the refractive indices of various solutions. The results show that a refractive-index resolution of 1.8 10(-4) RIU (linear fitting R2 = 0.954) was achieved for sucrose solutions with refractive indices ranging between 1.333 and 1.383. We also adopted the particle plasmon resonance sensing scheme using the fabricated optical fibers. The results provided additional information, specifically, a superior sensor resolution of 5.73 10(-5) RIU, and greater linearity at R2 = 0.999. PMID:23535636

  3. Fabrication Quality Analysis of a Fiber Optic Refractive Index Sensor Created by CO2 Laser Machining

    PubMed Central

    Chen, Chien-Hsing; Yeh, Bo-Kuan; Tang, Jaw-Luen; Wu, Wei-Te

    2013-01-01

    This study investigates the CO2 laser-stripped partial cladding of silica-based optic fibers with a core diameter of 400 ?m, which enables them to sense the refractive index of the surrounding environment. However, inappropriate treatments during the machining process can generate a number of defects in the optic fiber sensors. Therefore, the quality of optic fiber sensors fabricated using CO2 laser machining must be analyzed. The results show that analysis of the fiber core size after machining can provide preliminary defect detection, and qualitative analysis of the optical transmission defects can be used to identify imperfections that are difficult to observe through size analysis. To more precisely and quantitatively detect fabrication defects, we included a tensile test and numerical aperture measurements in this study. After a series of quality inspections, we proposed improvements to the existing CO2 laser machining parameters, namely, a vertical scanning pathway, 4 W of power, and a feed rate of 9.45 cm/s. Using these improved parameters, we created optical fiber sensors with a core diameter of approximately 400 ?m, no obvious optical transmission defects, a numerical aperture of 0.52 0.019, a 0.886 Weibull modulus, and a 1.186 Weibull-shaped parameter. Finally, we used the optical fiber sensor fabricated using the improved parameters to measure the refractive indices of various solutions. The results show that a refractive-index resolution of 1.8 10?4 RIU (linear fitting R2 = 0.954) was achieved for sucrose solutions with refractive indices ranging between 1.333 and 1.383. We also adopted the particle plasmon resonance sensing scheme using the fabricated optical fibers. The results provided additional information, specifically, a superior sensor resolution of 5.73 10?5 RIU, and greater linearity at R2 = 0.999. PMID:23535636

  4. An integrated solution for mold shape modification in precision glass molding to compensate refractive index change and geometric deviation

    NASA Astrophysics Data System (ADS)

    Su, Lijuan; Wang, Fei; He, Peng; Dambon, Olaf; Klocke, Fritz; Yi, Allen Y.

    2014-02-01

    In precision glass molding, refractive index change and geometric deviation (or curve change as often referred to in industry) occurred during molding process can result in substantial amount of aberrations. Previously, refractive index change and geometric deviation were investigated in separate studies by the authors. However, optical performance of a molded glass lens depends on both refractive index and geometry. In order to mold lenses with optimal performance, both refractive index change and geometric deviation have to be taken into consideration simultaneously and compensated. This paper presented an integrated compensation procedure for modifying molds to compensate both refractive index change and geometric deviation. Group refractive index change predicted by the finite element method simulation was used to provide a modified geometry design for a desired lens. Geometric deviations of molded glass lenses with the modified design were analyzed with a previously developed numerical simulation approach, which is used to modify the mold shape. This procedure was validated by molding a generic aspherical glass lens. Both geometry and optical measurement results confirmed that the molded lens performed as specified by the original design. It also demonstrated that finite element method assisted compensation procedure can be used to predict the final optical performance of compression molded glass components. This research provided an opportunity for optics manufacturers to achieve better performance lens while maintaining lower cost and a shorter cycle time.

  5. Analysis of the refractive index change of optical waveguide in LiNbO3 using a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Yang, Shi-han; Zhang, Liang; Lin, Xue-song; Feng, Jie; Zhou, Zi-gang; Chen, Jang-jun

    2014-11-01

    We used a commercially available 75 MHz regeneratively amplified laser system emitting 50 femtosecond pulses of energies up to 3nJ at a wavelength of 800 nm. All waveguides were fabricated by focussing the femotsecond pulse train polarised parallel to the x-axis to a distance of approximately 125 ?m below the sample surface using a 0.65 NA, 40 microscope objective and translating the sample along the y axis. To find the optimum waveguide fabrication parameters the translation speed was varied from 2 to 100 ?m/s. We introduces a method of measuring the refractive index of optical waveguide in ten micrometer. Useing CCD to measure the two-dimensional near-field light intensity distribution of the output cross-section of the waveguide, by measuring the two-dimensional near-field light intensity distribution of the output cross-section of the waveguide can be calculated the two-dimensional distribution of refractive index of waveguides. The context detailedly gives measurement results about femtosecond laser inducing the near-field intensity of lithium niobate optical waveguide cross-section and calculations of refractive index of optical waveguide. The results show that the refractive index of waveguides showed a large central, gradually reduce and the change of refractive index in the range of 0.001. This method is of great significance to measure the optical waveguide refractive index distribution.

  6. Pressure sensing in high-refractive-index liquids using long-period gratings nanocoated with silicon nitride.

    PubMed

    Smietana, Mateusz; Bock, Wojtek J; Mikulic, Predrag; Chen, Jiahua

    2010-01-01

    The paper presents a novel pressure sensor based on a silicon nitride (SiNx) nanocoated long-period grating (LPG). The high-temperature, radio-frequency plasma-enhanced chemical-vapor-deposited (RF PECVD) SiNx nanocoating was applied to tune the sensitivity of the LPG to the external refractive index. The technique allows for deposition of good quality, hard and wear-resistant nanofilms as required for optical sensors. Thanks to the SiNx nanocoating it is possible to overcome a limitation of working in the external-refractive-index range, which for a bare fiber cannot be close to that of the cladding. The nanocoated LPG-based sensing structure we developed is functional in high-refractive-index liquids (nD>1.46) such as oil or gasoline, with pressure sensitivity as high as when water is used as a working liquid. The nanocoating developed for this experiment not only has the highest refractive index ever achieved in LPGs (n>2.2 at ?=1,550 nm), but is also the thinnest (<100 nm) able to tune the external-refractive-index sensitivity of the gratings. To the best of our knowledge, this is the first time a nanocoating has been applied on LPGs that is able to simultaneously tune the refractive-index sensitivity and to enable measurements of other parameters. PMID:22163527

  7. Pressure Sensing in High-Refractive-Index Liquids Using Long-Period Gratings Nanocoated with Silicon Nitride

    PubMed Central

    Smietana, Mateusz; Bock, Wojtek J.; Mikulic, Predrag; Chen, Jiahua

    2010-01-01

    The paper presents a novel pressure sensor based on a silicon nitride (SiNx) nanocoated long-period grating (LPG). The high-temperature, radio-frequency plasma-enhanced chemical-vapor-deposited (RF PECVD) SiNx nanocoating was applied to tune the sensitivity of the LPG to the external refractive index. The technique allows for deposition of good quality, hard and wear-resistant nanofilms as required for optical sensors. Thanks to the SiNx nanocoating it is possible to overcome a limitation of working in the external-refractive-index range, which for a bare fiber cannot be close to that of the cladding. The nanocoated LPG-based sensing structure we developed is functional in high-refractive-index liquids (nd > 1.46) such as oil or gasoline, with pressure sensitivity as high as when water is used as a working liquid. The nanocoating developed for this experiment not only has the highest refractive index ever achieved in LPGs (n > 2.2 at ? = 1,550 nm), but is also the thinnest (<100 nm) able to tune the external-refractive-index sensitivity of the gratings. To the best of our knowledge, this is the first time a nanocoating has been applied on LPGs that is able to simultaneously tune the refractive-index sensitivity and to enable measurements of other parameters. PMID:22163527

  8. Effect of TiCl4 treatment on the refractive index of nanoporous TiO2 films

    NASA Astrophysics Data System (ADS)

    Lee, Jeeyoung; Lee, Myeongkyu

    2015-12-01

    We investigate the effect of TiCl4 treatment on the refractive index of a nanoporous TiO2 film. A nanoparticulate TiO2 film prepared on a glass substrate was immersed in a TiCl4 aqueous solution. The subsequent reaction of TiCl4 with H2O produces TiO2 and thus modifies the density and the refractive index of the film. With increasing TiCl4 concentration, the refractive index initially increased and then declined after being maximized (n = 2.02 at 633 nm) at 0.08 M concentration. A refractive index change as large as 0.45 could be obtained with the TiCl4 treatment, making it possible to achieve diffraction efficiency exceeding 80% in a diffraction grating-embedded TiO2 film. For high TiCl4 concentrations of 0.32 M and 0.64 M, the refractive index remained nearly unchanged. This was attributed to the limited permeability of high-viscosity TiCl4 solutions into the nanoporous films. The measured pore size distributions were in good agreement with the results of a diffraction analysis and refractive index measurement.

  9. Novel high refractive index, thermally conductive additives for high brightness white LEDs

    NASA Astrophysics Data System (ADS)

    Hutchison, Richard Stephen

    In prior works the inclusion of nanoparticle fillers has typically been shown to increase the thermal conductivity or refractive index of polymer nanocomposites separately. High refractive index zirconia nanoparticles have already proved their merit in increasing the optical efficiency of encapsulated light emitting diodes. However, the thermal properties of zirconia-silicone nanocomposites have yet to be investigated. While phosphor-converted light emitting diodes are at the forefront of solid-state lighting technologies for producing white light, they are plagued by efficiency losses due to excessive heating at the semiconductor die and in and around the phosphor particles, as well as photon scattering losses in the phosphor layer. It would then be of great interest if the high refractive index nanoparticles were found to both be capable of increasing the refractive index, thus reducing the optical scattering, and also the thermal conductivity, channeling more heat away from the LED die and phosphors, mitigating efficiency losses from heat. Thermal conductance measurements on unfilled and nanoparticle loaded silicone samples were conducted to quantify the effect of the zirconia nanoparticle loading on silicone nanocomposite thermal conductivity. An increase in thermal conductivity from 0.27 W/mK to 0.49 W/mK from base silicone to silicone with 33.5 wt% zirconia nanoparticles was observed. This trend closely mirrored a basic rule of mixtures prediction, implying a further enhancement in thermal conductivity could be achieved at higher nanoparticle loadings. The optical properties of transparency and light extraction efficiency of these composites were also investigated. While overall the zirconia nanocomposite showed good transparency, there was a slight decrease at the shorter wavelengths with increasing zirconia content. For longer wavelength LEDs, such as green or red, this might not matter, but phosphor-converted white LEDs use a blue LED as the photon source making this decrease in transparency important to note. This decrease in transparency may be partially or wholly why a decrease in light extraction efficiency is observed at the 33.5 wt% zirconia loading fraction used for the LED samples. Preliminary aging studies under full and enhanced power conditions were conducted over 500 and 1000 hours to observe any changes in the spectral output power and phosphor conversion efficiency of the LEDs due to inclusion of the zirconia nanoparticles. It was found that the nanoparticles have no negative effect on the aging properties but also show no enhancement in relative output power over a preliminary aging study. However, their inclusion did result in increased phosphor conversion efficiency over the use of an unfilled silicone. This increase was seen as around a 10% or greater enhancement for the nanocomposite over that for the base Sylgard silicone. These experiments were originally conducted on the commercially available methylated Sylgard 184 silicone and then again on a higher refractive index methyl-phenyl silicone from Momentive. While some of the results from the Momentive silicone were perplexing, it was seen that, even without the inclusion of nanoparticles, the Momentive silicone had a higher refractive index, better aging properties, and a higher phosphor conversion efficiency over 500 hours under enhanced power conditions, warranting further studies into methyl-phenyl silicone nanocomposites.

  10. Refractive index sensing with Fano resonant plasmonic nanostructures: a symmetry based nonlinear approach

    NASA Astrophysics Data System (ADS)

    Butet, Jrmy; Martin, Olivier J. F.

    2014-11-01

    Sensing using surface plasmon resonances is one of the most promising practical applications of plasmonic nanostructures and Fano resonances allow achieving a lower detection limit thanks to their narrow spectral features. However, a narrow spectral width of the subradiant mode in a plasmonic system, as observed in the weak coupling regime, is in general associated with a low modulation of the complete spectral response. In this article, we show that this limitation can be overcome by a nonlinear approach based on second harmonic generation and its dependence on symmetry at the nanoscale. The Fano resonant systems considered in this work are gold nanodolmens. Their linear and nonlinear responses are evaluated using a surface integral equation method. The numerical results demonstrate that a variation of the refractive index of the surrounding medium modifies the coupling between the dark and bright modes, resulting in a modification of the electromagnetic wave scattered at the second harmonic wavelength, especially the symmetry of the nonlinear emission. Reciprocally, we show that evaluating the asymmetry of the nonlinear emission provides a direct measurement of the gold nanodolmens dielectric environment. Interestingly, the influence of the refractive index of the surrounding medium on the nonlinear asymmetry parameter is approximately 10 times stronger than on the spectral position of the surface plasmon resonance: hence, smaller refractive index changes can be detected with this new approach. Practical details for an experimental realization of this sensing scheme are discussed and the resolution is estimated to be as low as ?n = 1.5 10-3, respectively 1.5 10-5, for an acquisition time of 60 s for an isolated gold nanodolmen, respectively an array of 10 10 nanodolmens.Sensing using surface plasmon resonances is one of the most promising practical applications of plasmonic nanostructures and Fano resonances allow achieving a lower detection limit thanks to their narrow spectral features. However, a narrow spectral width of the subradiant mode in a plasmonic system, as observed in the weak coupling regime, is in general associated with a low modulation of the complete spectral response. In this article, we show that this limitation can be overcome by a nonlinear approach based on second harmonic generation and its dependence on symmetry at the nanoscale. The Fano resonant systems considered in this work are gold nanodolmens. Their linear and nonlinear responses are evaluated using a surface integral equation method. The numerical results demonstrate that a variation of the refractive index of the surrounding medium modifies the coupling between the dark and bright modes, resulting in a modification of the electromagnetic wave scattered at the second harmonic wavelength, especially the symmetry of the nonlinear emission. Reciprocally, we show that evaluating the asymmetry of the nonlinear emission provides a direct measurement of the gold nanodolmens dielectric environment. Interestingly, the influence of the refractive index of the surrounding medium on the nonlinear asymmetry parameter is approximately 10 times stronger than on the spectral position of the surface plasmon resonance: hence, smaller refractive index changes can be detected with this new approach. Practical details for an experimental realization of this sensing scheme are discussed and the resolution is estimated to be as low as ?n = 1.5 10-3, respectively 1.5 10-5, for an acquisition time of 60 s for an isolated gold nanodolmen, respectively an array of 10 10 nanodolmens. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05623j

  11. Determination of index of refraction and size of supermicrometer particles from light scattering measurements at two angles

    NASA Astrophysics Data System (ADS)

    Eidhammer, Trude; Montague, Derek C.; Deshler, Terry

    2008-08-01

    A twin angle optical particle counter (TAOPC) that measures forward scattering at 40° and 74° was developed to determine the index of refraction of atmospheric particles. An error analysis indicates that measurement uncertainties for size at 40° are between 4 and 10% for particles >1.5 μm and between 5 and 15% at 74°. For the index of refraction determination, the measurement uncertainties lead to index of refraction uncertainties between 1 and 2.5%. The instrument was tested on nonabsorbing spherical particles of known composition and size in the laboratory. The majority of the estimated indices of refraction were within ±1% of the expected indices, and size determination was within acceptable error. The instrument was also tested on non-spherical absorbing particles to determine the complex index of refraction of ambient mineral dust particles collected in Laramie, Wyoming, in February 2006. The index of refraction was determined with the particle number ratio approach and was estimated to be in the range 1.60-1.67 for the real part and 0.009-0.0104 for the imaginary part. Simultaneously with the TAOPC measurements, particles were collected on polycarbonate filters for computer-controlled scanning electron microscopy (CCSEM) analysis. Index of refraction calculated from this analysis was in the range 1.61-1.66 for the real part and 0.008-0.012 for the imaginary part. Particles were also collected for longer periods on two different filter pack systems in February 2006. Estimates of index of refraction from these measurements compared well with the CCSEM analysis.

  12. All-optical on-chip sensor for high refractive index sensing

    SciTech Connect

    Liu, Yazhao; Salemink, H. W. M.

    2015-01-19

    A highly sensitive sensor design based on two-dimensional photonic crystal cavity is demonstrated. The geometric structure of the cavity is modified to gain a high quality factor, which enables a sensitive refractive index sensing. A group of slots with optimized parameters is created in the cavity. The existence of the slots enhances the light-matter interactions between confined photons and analytes. The interactions result in large wavelength shifts in the transmission spectra and are denoted by high sensitivities. Experiments show that a change in refractive index of Δn ∼ 0.12 between water and oil sample 1 causes a spectral shift of 23.5 nm, and the spectral shift between two oil samples is 5.1 nm for Δn ∼ 0.039. These results are in good agreement with simulations, which are 21.3 and 7.39 nm for the same index changes.

  13. Dynamic two-dimensional refractive index modulation for high performance acousto-optic deflector.

    PubMed

    Wang, Tiansi; Zhang, Chong; Aleksov, Aleksandar; Salama, Islam A; Kar, Aravinda

    2015-12-28

    The performance of an acousto-optic deflector is studied for two-dimensional refractive index that varies as periodic and sinc functions in the transverse and longitudinal directions, respectively, with respect to the direction of light propagation. Phased array piezoelectric transducers can be operated at different phase shifts to produce a two-dimensionally inhomogeneous domain of phase grating in the acousto-optic media. Also this domain can be steered at different angles by selecting the phase shift appropriately. This mechanism of dynamically tilting the refractive index-modulated domain enables adjusting the incident angle of light on the phase grating plane without moving the light source. So the Bragg angle of incidence can be always achieved at any acoustic frequency, and consequently, the deflector can operate under the Bragg diffraction condition at the optimum diffraction efficiency. Analytic solutions are obtained for the Bragg diffraction of plane waves based on the second order coupled mode theory, and the diffraction efficiency is found to be unity for optimal index modulations at certain acoustic parameters. PMID:26832030

  14. Validation of refractive index structure parameter estimation for certain infrared bands.

    PubMed

    Sivasl?gil, Mustafa; Erol, Cemil Berin; Polat, zgr Murat; Sar?, Hseyin

    2013-05-10

    Variation of the atmospheric refraction index due to turbulent fluctuations is one of the key factors that affect the performance of electro-optical and infrared systems and sensors. Therefore, any prior knowledge about the degree of variation in the refractive index is critical in the success of field studies such as search and rescue missions, military applications, and remote sensing studies where these systems are used frequently. There are many studies in the literature in which the optical turbulence effects are modeled by estimation of the refractive index structure parameter, C(n)(2), from meteorological data for all levels of the atmosphere. This paper presents a modified approach for bulk-method-based C(n)(2) estimation. According to this approach, conventional wind speed, humidity, and temperature values above the surface by at least two levels are used as input data for Monin-Obukhov similarity theory in the estimation of similarity scaling constants with a finite difference approximation and a bulk-method-based C(n)(2) estimation. Compared with the bulk method, this approach provides the potential for using more than two levels of standard meteorological data, application of the scintillation effects of estimated C(n)(2) on the images, and a much simpler solution than traditional ones due to elimination of the roughness parameters, which are difficult to obtain and which increase the complexity, the execution time, and the number of additional input parameters of the algorithm. As a result of these studies, Atmospheric Turbulence Model Software is developed and the results are validated in comparison to the C(n)(2) model presented by Tunick. PMID:23669824

  15. Higher-order nonlinearity of refractive index: the case of argon.

    PubMed

    Tarazkar, Maryam; Romanov, Dmitri A; Levis, Robert J

    2014-06-01

    The nonlinear coefficients, n4, of the time-dependent refractive index for argon are calculated in the non-resonant optical regime. Second-order polynomial fitting of DC-Kerr, ?((2))(-?; ?, 0, 0), electric field induced second harmonic generation (ESHG), ?((2))(-2?; ?, ?, 0), and static second-order hyperpolarizability, ?((2))(0; 0, 0, 0), is performed using an auxiliary electric field approach to obtain the corresponding fourth-order optical properties. A number of basis sets are investigated for the fourth-order hyperpolarizability processes at 800 nm at coupled cluster singles and doubles level of theory, starting with the t-aug-cc-pV5Z basis set and expanding that basis set by adding diffuse functions and polarization functions. Comparison shows that the results obtained with the t-aug-cc-pV5Z basis are in very good agreement with the results obtained using the q-aug-cc-pV5Z, t-aug-cc-pV6Z, and q-aug-cc-pV6Z basis sets. To calculate the nonlinear refractive index n4, an approximate formula is suggested which expresses the related degenerate six-wave mixing coefficient, ?((4))(-?; ?, -?, ?, -?, ?), in terms of the DC-Kerr, ?((4))(-?; ?, 0, 0, 0, 0), ESHG, ?((4))(-2?; ?, ?, 0, 0, 0), and the static fourth-order hyperpolarizability coefficients. The higher-order nonlinear refractive index n4 is found to be positive over the wavelengths 300 nm-2000 nm. In the infrared spectral range, the obtained values of n4 are in qualitative agreement with the results of Kramers-Kronig-based calculations. PMID:24908017

  16. Refractive index of thin films realized by Satisloh SP reactive sputtering system

    NASA Astrophysics Data System (ADS)

    Monaco, Gianni; Colautti, Arturo; Allegro, Cristina; Godin, Tom; Gold, Steffan; Witzany, Michael

    2013-09-01

    Pulsed DC reactive sputtering is a very interesting technique for coating applications. Reactive sputtering can give very dense layers, low stress of the deposited multilayer film, high reproducibility, very high hardness (up to 1200 Vickers hardness) with unbeatable high rates ideal for industrial applications. SP-100 is Satisloh reactive sputtering systems with only one target material but can deposit various film materials simply by using different gases such as argon, as well as the reactive gases nitrogen and oxygen. Silicon-oxides, silicon-nitrides and all kinds of silicon-oxy-nitrides (SiOx-SixOyNz-SixNy) with a refractive index range of 1.44-2.05 in the visible range can be obtained. In the reactive sputtering the material it is usually deposited in the so called "transition mode" where it must be found the correct equilibrium point between the target voltage and the reactive gas flow. The transition mode assures a dense film with a stable rate. Condition to find such equilibrium point is given by the so called "material hysteresis" in which the target voltage is depicted in function of the reactive gas voltage. The hysteresis and the consequent equilibrium point are strongly depended by the power supplied to the target and the inert gas (argon) flow which could affect the optical characteristics and the deposition rate. We checked the refractive indexes of the SiOx and SixNy of very thin (1 QW Optical thickness at 520 nm) and thicker (3, 5 and 9 QW @520 nm) reporting how the different conditions can affect the refractive index and the deposition rate of the different materials.

  17. Long period fiber grating based refractive index sensor with enhanced sensitivity using Michelson interferometric arrangement

    NASA Astrophysics Data System (ADS)

    Singh, Amit

    2015-06-01

    The long period fiber grating (LPFG) is widely used as a sensor due to its high sensitivity and resolution. However, the broad bandwidth of the attenuation bands formed by the mode coupling between the fundamental core mode and the cladding modes constitutes a difficulty when the device is used as a conventional sensor. To overcome this limitation, a Michelson interferometer-type sensor configuration has been developed, using an LPFG grating pair formed by coating a mirror at the distal end of the LPFG. This sensor configuration is more convenient to use and is able to overcome the limitations of the single LPFG based sensor as the shifts in the attenuation bands being more easily detectable due to the formation of the sharp spectral fringe pattern in the LPFG based Michelson interferometer. In this work, I studied the LPFG based Michelson interferometer as the refractive index sensor and discussed the sensitivity enhancement of the LPFG based Michelson interferometer as a refractive index sensor by employing higher order cladding modes and by reducing the cladding radius. The results demonstrated the HE17 mode with a cladding radius of 62.5 ?m, in the range of surrounding refractive index (SRI) of 1-1.45, and its resonant peak showed a wavelength shift of 26.99 nm/RIU. When the cladding region was further reduced to 24 ?m, the resonant peak showed a wavelength shift of 569.88 nm/RIU, resulting in a sensitivity enhancement of nearly 21 times. However, as the cladding region was etched further, then the HE17 order cladding mode and higher mode would be cut off. Therefore, the implementation of high sensitivity for SRI sensing with the reduced cladding in the LPFG based Michelson interferometer is dependent on the proper combination of the cladding radius and cladding mode order.

  18. Higher-order nonlinearity of refractive index: The case of argon

    NASA Astrophysics Data System (ADS)

    Tarazkar, Maryam; Romanov, Dmitri A.; Levis, Robert J.

    2014-06-01

    The nonlinear coefficients, n4, of the time-dependent refractive index for argon are calculated in the non-resonant optical regime. Second-order polynomial fitting of DC-Kerr, ?(2)(-?; ?, 0, 0), electric field induced second harmonic generation (ESHG), ?(2)(-2?; ?, ?, 0), and static second-order hyperpolarizability, ?(2)(0; 0, 0, 0), is performed using an auxiliary electric field approach to obtain the corresponding fourth-order optical properties. A number of basis sets are investigated for the fourth-order hyperpolarizability processes at 800 nm at coupled cluster singles and doubles level of theory, starting with the t-aug-cc-pV5Z basis set and expanding that basis set by adding diffuse functions and polarization functions. Comparison shows that the results obtained with the t-aug-cc-pV5Z basis are in very good agreement with the results obtained using the q-aug-cc-pV5Z, t-aug-cc-pV6Z, and q-aug-cc-pV6Z basis sets. To calculate the nonlinear refractive index n4, an approximate formula is suggested which expresses the related degenerate six-wave mixing coefficient, ?(4)(-?; ?, -?, ?, -?, ?), in terms of the DC-Kerr, ?(4)(-?; ?, 0, 0, 0, 0), ESHG, ?(4)(-2?; ?, ?, 0, 0, 0), and the static fourth-order hyperpolarizability coefficients. The higher-order nonlinear refractive index n4 is found to be positive over the wavelengths 300 nm-2000 nm. In the infrared spectral range, the obtained values of n4 are in qualitative agreement with the results of Kramers-Kronig-based calculations.

  19. Dopant-dependent reflectivity and refractive index of microcrystalline molybdenum-bronze thin films

    NASA Astrophysics Data System (ADS)

    Hussain, Zahid

    2002-05-01

    Reflectivity spectra of HxMoO3 and LixMoO3 thin films were measured over the photon energy range from 0.4 to 4.2 eV. It was found that microcrystalline molybdenum bronzes have reflectances between 6% and 30% over the concentration x, range 0?x?0.64. Values for the real part of the refractive index n were also determined from the refined reflectivity data using different numerical techniques depending upon the dispersive and nondispersive regions in the data. The values of high-frequency dielectric constant ?hf of ZxMoO3 (Z=H+,Li+) bronzes were determined from the refractive index data to estimate the effective electronic masses involved in the optical and/or polaronic transitions. We interpret the optical data using the modified Drude-Zener model together with a single-oscillator model to differentiate between bound and free electronic states. Using a single-oscillator model, the oscillator energy Ea and the dispersion energy Ed were found to increase and decrease, respectively, with increasing x values, opposite to what occurs in crystalline molybdenum bronzes. These findings support the fact that Bloch electrons are almost absent in the investigated microcrystalline bronzes. The small reflectivity crests and the observed shift of the minimum reflectivity (or minimum refractive index) toward higher frequency with increasing x value in ZxMoO3 appear to be consistent with polaronic hopping, which arises from the excitation of electrons from localized in-gap states of Mo5+ ions into higher impurity states of Mo6+ (or Mo4+) ions within the optical band gap.

  20. Triangular lattice of carbon nanotube arrays for negative index of refraction and subwavelength lensing effect

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Wang, X.; Rybczynski, J.; Wang, D. Z.; Kempa, K.; Ren, Z. F.

    2005-04-01

    Self-assembly of polystyrene microspheres has been utilized in a two-step masking technique to prepare triangular lattices of catalytic nanodots at low cost. Subsequent triangular lattices of aligned carbon nanotubes on a silicon substrate are achieved by plasma-enhanced chemical vapor deposition. Nickel is used both in the nanodots and in the secondary mask. The triangular lattices of carbon nanotube arrays as two-dimensional photonic crystals show higher geometrical symmetry than the hexagonal lattices previously reported, enabling broader applications including negative index of refraction and subwavelength lensing effect.

  1. Photonic crystal nanoslotted parallel quadrabeam integrated cavity for refractive index sensing with high figure of merit

    NASA Astrophysics Data System (ADS)

    Yang, Daquan; Tian, Huiping; Ji, Yuefeng

    2015-06-01

    Sensitivities (S) and quality factors (Q) have been trade-offs in optical resonator sensors, and optimal geometry that maximizes both factors is under active development. In this paper, we experimentally demonstrate an optical sensor based on photonic crystal (PhC) nanoslotted parallel quadrabeam integrated cavity (NPQIC) with high figure of merit (FOM). Both high sensitivity (S) of 451 nm/RIU (refractive index unit) and Q-factor >7000 in water at telecom wavelength range have been achieved simultaneously, which features a sensor figure of merit (FOM) >2000, an order of magnitude improvement over previous photonic crystal sensors.

  2. Swift and heavy ion implanted chalcogenide laser glass waveguides and their different refractive index distributions

    SciTech Connect

    Qiu Feng; Narusawa, Tadashi; Zheng Jie

    2011-02-10

    Planar waveguides have been fabricated in Nd- or Ho-doped gallium lanthanum sulfide laser glasses by 60 MeV Ar or 20 MeV N ion implantation. The refractive index profiles were reconstructed based on the results of prism coupling. The Ar implanted waveguides exhibit an approximate steplike distribution, while the N implanted ones show a ''well + barrier'' type. This difference can be attributed to the much lower dose of Ar ions. After annealing, the N implanted waveguides can support two modes at 1539 nm and have low propagation loss, which makes them candidates for novel waveguide lasers.

  3. Determining the refractive index and thickness of thin films from prism coupler measurements

    NASA Technical Reports Server (NTRS)

    Kirsch, S. T.

    1981-01-01

    A simple method of determining thin film parameters from mode indices measured using a prism coupler is described. The problem is reduced to doing two least squares straight line fits through measured mode indices vs effective mode number. The slope and y intercept of the line are simply related to the thickness and refractive index of film, respectively. The approach takes into account the correlation between as well as the uncertainty in the individual measurements from all sources of error to give precise error tolerances on the best fit values. Due to the precision of the tolerances, anisotropic films can be identified and characterized.

  4. A Refractive Index Sensor Based on a Metal-Insulator-Metal Waveguide-Coupled Ring Resonator

    PubMed Central

    Yan, Shu-Bin; Luo, Liang; Xue, Chen-Yang; Zhang, Zhi-Dong

    2015-01-01

    A refractive index sensor composed of two straight metal-insulator-metal waveguides and a ring resonator is presented. One end of each straight waveguide is sealed and the other end acts as port. The transmission spectrum and magnetic field distribution of this sensor structure are simulated using finite-difference time-domain method (FDTD). The results show that an asymmetric line shape is observed in the transmission spectrum, and that the transmission spectrum shows a filter-like behavior. The quality factor and sensitivity are taken to characterize its sensing performance and filter properties. How structural parameters affect the sensing performance and filter properties is also studied. PMID:26610491

  5. Refractive index measured by laser beam displacement at {lambda}=1064 nm for solvents and deuterated solvents

    SciTech Connect

    Shelton, David P.

    2011-07-20

    The refractive index of a liquid is determined with 0.0003 accuracy from measurements of laser beam displacement by a liquid-filled standard 10 mm spectrophotometer cell. The apparatus and methods are described and the results of measurements at {lambda}=1064 nm and T=25.0 deg. C for 30 solvents and deuterated solvents are presented. Several sources of potential systematic errors as large as 0.003 are identified, the most important being the curvature of the liquid cell windows. The measurements are analyzed accounting for the significant imperfections of the apparatus.

  6. Ultrahigh refractive index sensing performance of plasmonic quadrupole resonances in gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Yong, Zehui; Lei, Dang Yuan; Lam, Chi Hang; Wang, Yu

    2014-04-01

    The refractive index sensing properties of plasmonic resonances in gold nanoparticles (nanorods and nanobipyramids) are investigated through numerical simulations. We find that the quadruple resonance in both nanoparticles shows much higher sensing figure of merit (FOM) than its dipolar counterpart, which is attributed mainly to the reduction in resonance linewidth. More importantly, our results predict that at the same sensing wavelength, the sensing FOM of the quadrupole mode can be significantly boosted from 3.9 for gold nanorods to 7.4 for gold nanobipyramids due to the geometry-dependent resonance linewidth, revealing a useful strategy for optimizing the sensing performance of metal nanoparticles.

  7. Nonlocal nonlinear refractive index of gold nanoparticles synthesized by ascorbic acid reduction: comparison of fitting models

    PubMed Central

    Balbuena Ortega, A.; Arroyo Carrasco, M.L.; Méndez Otero, M.M.; Gayou, V.L.; Delgado Macuil, R.; Martínez Gutiérrez, H.; Iturbe Castillo, M.D.

    2014-01-01

    In this paper, the nonlinear refractive index of colloidal gold nanoparticles under continuous wave illumination is investigated with the z-scan technique. Gold nanoparticles were synthesized using ascorbic acid as reductant, phosphates as stabilizer and cetyltrimethylammonium chloride (CTAC) as surfactant agent. The nanoparticle size was controlled with the CTAC concentration. Experiments changing incident power and sample concentration were done. The experimental z-scan results were fitted with three models: thermal lens, aberrant thermal lens and the nonlocal model. It is shown that the nonlocal model reproduces with exceptionally good agreement; the obtained experimental behaviour. PMID:25705090

  8. Fabrication of elliptic microfibers with CO2 laser for high-sensitivity refractive index sensing.

    PubMed

    Sun, Li-Peng; Li, Jie; Gao, Shuai; Jin, Long; Ran, Yang; Guan, Bai-Ou

    2014-06-15

    We propose a convenient method for achieving highly birefringent (HiBi) elliptic microfibers by use of the CO2-laser machining and the flame-brushing techniques. With optimization of fabrication process, a high birefringence of up to 2.1010(-2) is experimentally obtained. Especially, within a polarization Sagnac interferometer acting as a refractive index (RI) sensor, both positive and abnormal negative sensitivity is measured, dependent on the geometrical variables of the HiBi microfiber. The maximum RI sensitivity is ?195,348??nm/RI-unit around RI=1.35887, which is the highest among the microfiber devices as reported, to our knowledge. PMID:24978529

  9. Highly birefringent suspended-core photonic microcells for refractive-index sensing

    SciTech Connect

    Wang, Chao; Jin, Wa; Ma, Jun; Jin, Wei Yang, Fan; Ho, Hoi Lut; Liao, Changrui; Wang, Yiping

    2014-08-11

    An in-line photonic microcell with a highly birefringent suspended microfiber core is fabricated by locally heating and pressurizing selected air-holes of an endless single mode photonic crystal fiber. The microfiber core has rhombus-like cross-sectional geometry and could achieve a high birefringence of up to 10{sup −2}. The microfiber core is fixed at the center of the microcell by thin struts attached to an outer jacket tube, which protects and isolates the microfiber from environmental contaminations. Highly sensitive and robust refractive index sensors based on such microcells are experimentally demonstrated.

  10. A Refractive Index Sensor Based on a Metal-Insulator-Metal Waveguide-Coupled Ring Resonator.

    PubMed

    Yan, Shu-Bin; Luo, Liang; Xue, Chen-Yang; Zhang, Zhi-Dong

    2015-01-01

    A refractive index sensor composed of two straight metal-insulator-metal waveguides and a ring resonator is presented. One end of each straight waveguide is sealed and the other end acts as port. The transmission spectrum and magnetic field distribution of this sensor structure are simulated using finite-difference time-domain method (FDTD). The results show that an asymmetric line shape is observed in the transmission spectrum, and that the transmission spectrum shows a filter-like behavior. The quality factor and sensitivity are taken to characterize its sensing performance and filter properties. How structural parameters affect the sensing performance and filter properties is also studied. PMID:26610491

  11. Pulsed laser deposition and refractive index measurement of fully substituted bismuth iron garnet films

    NASA Astrophysics Data System (ADS)

    Tepper, T.; Ross, C. A.

    2003-08-01

    A systematic study of the pulsed-laser deposition of fully substituted bismuth iron garnet (BIG, or Bi 3Fe 5O 12) has been carried out. Garnet-structure BIG films grow epitaxially onto gallium gadolinium garnet substrates under deposition conditions that lead to a stoichiometric film. The variation of stoichiometry with deposition conditions is discussed. The refractive index, n, of BIG decreases from 2.819 at 633 nm to 2.584 at 1550 nm, with an imaginary part, k, less than 0.05.

  12. Effect of the charges of impurity on the refractive index changes in parabolic quantum dot

    NASA Astrophysics Data System (ADS)

    Huang, Jinsheng

    2013-01-01

    The linear and nonlinear refractive index changes (RICs) in a disc-like parabolic quantum dot (QD) with impurity between the ground (L=0) and the first excited state (L=1) have been examined based on the computed energies and wave functions. The parabolic QD without impurity was taken into account for comparison. We found that the linear and total RIC of impurity QD decrease as the charge of the impurity is increased and increase with characteristic dot radius decreasing. The maximum of linear RIC of parabolic QD without impurity remains constant for different confinement strengths.

  13. Polaron effects on the refractive index changes in cylindrical quantum dots with parabolic potential

    NASA Astrophysics Data System (ADS)

    Li, Ning; Guo, Kang-Xian; Shao, Shuai

    2011-12-01

    The effect of electron-LO-phonon interaction on refractive index changes (RICs) for cylindrical quantum dots (CQDs) with an applied electric field is theoretically investigated. Analytic forms of the linear and third-order nonlinear the RICs are obtained for a cylindrical QD by using compact-density-matrix approach and iterative method, and the numerical results are presented for a GaAs cylinder quantum dot. The results show that the RICs coefficient is greatly enhanced and the peak shift to the aspect of high energy when considering the influence of electron-LO-phonon interaction.

  14. Evanescent gain for slow and stopped light in negative refractive index heterostructures

    NASA Astrophysics Data System (ADS)

    Kirby, Edmund I.; Hamm, Joachim M.; Pickering, Tim W.; Tsakmakidis, Kosmas L.; Hess, Ortwin

    2011-07-01

    We theoretically and numerically analyze a five-layer trapped rainbow waveguide made of a passive negative refractive index (NRI) core layer and gain strips in the cladding. Analytic transfer-matrix calculations and full-wave time-domain simulations are deployed to calculate, both in the frequency and in the time domain, the losses or gain experienced by complex-wave-vector and complex-frequency modes. We find excellent agreement between five distinct sets of results, showing that the use of evanescent pumping (gain) can compensate the losses in the NRI slow- and stopped-light regimes.

  15. Significant correlation between refractive index and activity of mitochondria: single mitochondrion study

    PubMed Central

    Haseda, Keisuke; Kanematsu, Keita; Noguchi, Keiichi; Saito, Hiromu; Umeda, Norihiro; Ohta, Yoshihiro

    2015-01-01

    Measurements of refractive indices (RIs) of intracellular components can provide useful information on the structure and function of cells. The present study reports, for the first time, determination of the RI of an isolated mitochondrion in isotonic solution using retardation-modulated differential interference contrast microscopy. The value was 1.41 0.01, indicating that mitochondria are densely packed with molecules having high RIs. Further, the RIs of each mitochondrion were significantly correlated with the mitochondrial membrane potential, an index of mitochondrial activity. These results will provide useful information on the structures and functions of cells based on the intracellular distribution of RIs. PMID:25798310

  16. Simultaneous detection of refractive index and surface charges in nanolaser biosensors

    SciTech Connect

    Watanabe, Keisuke; Kishi, Yoji; Hachuda, Shoji; Watanabe, Takumi; Sakemoto, Mai; Nishijima, Yoshiaki; Baba, Toshihiko

    2015-01-12

    The emission intensity of a GaInAsP photonic crystal nanolaser is affected by the pH of the solution, in which the nanolaser is immersed. This phenomenon can be explained by the change in the redox potential, which modifies the filling of electrons at surface states of the semiconductor and hence the nonradiative surface recombination. This phenomenon allows the nanolaser to simultaneously and independently detect the refractive index and electric charges near the surface on the basis of the variation in emission wavelength and intensity, respectively. This paper demonstrates this function through alternate deposition of charged polyelectrolytes and hybridization of deoxyribonucleic acids.

  17. All-silicon integrated Fabry-Prot cavity for volume refractive index measurement in microfluidic systems

    NASA Astrophysics Data System (ADS)

    St-Gelais, R.; Masson, J.; Peter, Y.-A.

    2009-06-01

    We report a refractive index (RI) sensor based on the use of vertically etched silicon Bragg reflectors. The device is robust and performs measurements through tens of micrometers of liquid. A sensitivity of 907 nm/RIU (RI units) and a resolution of 1.710-5 RIU are obtained and are in good agreement with optical simulations. This resolution is the highest reported for a volume RI sensor integrated with a microfluidic system. Expected applications for the sensor in the fields of single cell characterization and chip based liquid chromatography are discussed.

  18. Spatially resolved refractive index profiles of electrically switchable computer-generated holographic gratings.

    PubMed

    Zito, Gianluigi; Finizio, Andrea; De Nicola, Sergio

    2009-10-12

    We describe a spatially resolved interferometric technique combined with a phase reconstruction method that provides a quantitative two-dimensional profile of the refractive index and spatial distribution of the optical contrast between the on-off states of electrically switchable diffraction gratings as a function of the external electric field. The studied structures are holographic gratings optically written into polymer/liquid crystal composites through single-beam spatial light modulation by means of computer-generated holograms. The electro-optical response of the gratings is also discussed. The diffraction efficiency results to be dependent on the incident light polarization suggesting the possibility to develop polarization dependent switching devices. PMID:20372618

  19. Triangular lattice of carbon nanotube arrays for negative index of refraction and subwavelength lensing effect

    SciTech Connect

    Wang, Y.; Wang, X.; Rybczynski, J.; Wang, D.Z.; Kempa, K.; Ren, Z.F.

    2005-04-11

    Self-assembly of polystyrene microspheres has been utilized in a two-step masking technique to prepare triangular lattices of catalytic nanodots at low cost. Subsequent triangular lattices of aligned carbon nanotubes on a silicon substrate are achieved by plasma-enhanced chemical vapor deposition. Nickel is used both in the nanodots and in the secondary mask. The triangular lattices of carbon nanotube arrays as two-dimensional photonic crystals show higher geometrical symmetry than the hexagonal lattices previously reported, enabling broader applications including negative index of refraction and subwavelength lensing effect.

  20. Enhancing the efficiency of slow-wave electron cyclotron masers with the tapered refractive index

    SciTech Connect

    Kong Lingbao; Hou Zhiling; Jing Jian; Jin Haibo; Du Chaohai

    2013-04-15

    The nonlinear analysis of slow-wave electron cyclotron masers (ECM) based on anomalous Doppler effect in a slab waveguide is presented. A method of tapered refractive index (TRI) is proposed to enhance the efficiency of slow-wave ECM. The numerical calculations show that the TRI method can significantly enhance the efficiency of slow-wave ECM with the frequency ranging from the microwave to terahertz band. The effect of beam velocity spread on the efficiency has also been studied. Although the velocity spread suppresses the efficiency significantly, a great enhancement of efficiency can still be introduced by the TRI method.

  1. CdSe/ZnS quantum dots as sensors for the local refractive index

    NASA Astrophysics Data System (ADS)

    Aubret, Antoine; Pillonnet, Anne; Houel, Julien; Dujardin, Christophe; Kulzer, Florian

    2016-01-01

    We explore the potential of CdSe/ZnS colloidal quantum dots (QDs) as probes for their immediate dielectric environment, based on the influence of the local refractive index on the fluorescence dynamics of these nanoemitters. We first compare ensembles of quantum dots in homogeneous solutions with single quantum dots dispersed on various dielectric substrates, which allows us to test the viability of a conceptual framework based on a hard-sphere region-of-influence and the Bruggeman effective-medium approach. We find that all our measurements can be integrated into a coherent description, provided that the conceptualized point-dipole emitter is positioned at a distance from the substrate that corresponds to the geometry of the QD. Three theoretical models for the evolution of the fluorescence decay rate as a function of the local refractive index are compared, showing that the classical Lorentz approach (virtual cavity) is the most appropriate for describing the data. Finally, we use the observed sensitivity of the QDs to their environment to estimate the detection limit, expressed as the minimum number of traceable streptavidin molecules, of a potential QD-nanosensor based on fluorescence lifetime.We explore the potential of CdSe/ZnS colloidal quantum dots (QDs) as probes for their immediate dielectric environment, based on the influence of the local refractive index on the fluorescence dynamics of these nanoemitters. We first compare ensembles of quantum dots in homogeneous solutions with single quantum dots dispersed on various dielectric substrates, which allows us to test the viability of a conceptual framework based on a hard-sphere region-of-influence and the Bruggeman effective-medium approach. We find that all our measurements can be integrated into a coherent description, provided that the conceptualized point-dipole emitter is positioned at a distance from the substrate that corresponds to the geometry of the QD. Three theoretical models for the evolution of the fluorescence decay rate as a function of the local refractive index are compared, showing that the classical Lorentz approach (virtual cavity) is the most appropriate for describing the data. Finally, we use the observed sensitivity of the QDs to their environment to estimate the detection limit, expressed as the minimum number of traceable streptavidin molecules, of a potential QD-nanosensor based on fluorescence lifetime. Electronic supplementary information (ESI) available: Experimental techniques, further results and analysis. See DOI: 10.1039/C5NR06998J

  2. Quantitative phase and refractive index measurements with point-source digital in-line holographic microscopy.

    PubMed

    Jericho, M H; Kreuzer, H J; Kanka, M; Riesenberg, R

    2012-04-01

    Point-source digital in-line holographic microscopy with numerical reconstruction is ideally suited for quantitative phase measurements to determine optical path lengths and to extract changes in refractive index within accuracy close to 0.001 on the submicrometer length scale. This is demonstrated with simulated holograms and with detailed measurements on a number of different micrometer-sized samples such as suspended drops, optical fibers, as well as organisms of biological interest such as E. coli bacteria, HeLa cells, and fibroblast cells. PMID:22505068

  3. Spatiotemporal collapse in a nonlinear waveguide with a randomly fluctuating refractive index.

    PubMed

    Gaididei, Y B; Christiansen, P L

    1998-07-15

    Analytical results, based on the virial theorem and the Furutsu-Novikov theorem, of the spatiotemporal evolution of a pulse in a nonlinear waveguide with a randomly fluctuating refractive index are presented. For initial conditions in which total collapse occurs in a homogeneous waveguide, random fluctuations postpone the collapse. Sufficiently large-amplitude and short-wavelength fluctuations can cause an initially localized pulse to spread instead of contracting. We show that the disorder can be applied to induce a high degree of controllability of the spatiotemporal extent of the pulses in the nonlinear waveguide. PMID:18087437

  4. Refractive index measurement for planar photonic crystal using a microscopy-spectrometry method

    NASA Astrophysics Data System (ADS)

    Ouyang, Mike X.; Onyiriuka, Emmanuel C.; Kinney, L. D.

    2000-11-01

    We report a unique technique to measure the refractive index (n), extinction coefficient (k), and thickness of thin films based on either the reflection or transmission spectra. The method combines a spectrometer, an optical microscope and a video camera. It is inexpensive, versatile and fast (< a few sec). Using this technology, n&k of 1.68 and 0.376, respectively, at 1500 nm was measured on a planar photonic crystal. The photonic crystal with a dimension of 117 X 90 micrometers 2 mm has a periodic cermet structure on Si substrate made by Deutsch Telekom using the electron induced deposition.

  5. Estimation of the refractive index structure characteristic of air from coherent Doppler wind lidar data.

    PubMed

    Banakh, V A; Smalikho, I N; Rahm, S

    2014-08-01

    A technique is proposed for estimating the refractive index structure characteristic of air from data of a coherent Doppler wind lidar. The proposed technique is tested in atmospheric experiments. Time profiles of the structure characteristic in the atmospheric surface layer are obtained and compared with the time profiles of the dissipation rate of the kinetic energy of turbulence obtained from the same lidar data. It is shown in this way that coherent lidars can be used for investigating not only wind turbulence, but also temperature turbulence. PMID:25078167

  6. Sensitivity of the Lidar ratio to changes in size distribution and index of refraction

    NASA Technical Reports Server (NTRS)

    Evans, B. T. N.

    1986-01-01

    In order to invert lidar signals to obtain reliable extinction coefficients, sigma, a relationship between sigma and the backscatter coefficient, beta, must be given. These two coefficients are linearly related if the complex index of refraction, m, particle shape size distribution, N, does not change along the path illuminated by the laser beam. This, however, is generally not the case. An extensive Mie computation of the lidar ratio R = beta/sigma and the sensitivity of R to the changes in a parametric space defined by N and m were examined.

  7. Effect of the imaginary part of the refractive index on light scattering by spheres.

    PubMed

    Wang, George; Chakrabarti, Amitabha; Sorensen, Christopher M

    2015-07-01

    For spheres of arbitrary radius R and complex index of refraction n+i?, we identify a new parameter that indicates when the imaginary part ? seriously affects the scattering by a sphere. The parameter is ?kR, where k is the wave vector magnitude, such that when ?kR grows larger than one, the scattering is affected and, when ?kR>3, the effects saturate. The effects are uncovered and demonstrated with Q-space analysis. The physical basis for ?kR lies in the fact that it is the ratio of the radius to the optical skin depth. PMID:26367149

  8. Infrared Refractive Index of Silicon: Parity and Sum-Rule Tests

    NASA Astrophysics Data System (ADS)

    Karstens, William; Inokuti, Mitio; Smith, David Y.

    2012-02-01

    We have resolved conflicting reports for the IR refractive index of silicon using general considerations of linear response theory. We find that use of unphysical series expansions in the analysis of channel spectra has been a significant source of systematic error. Recognition that the index is an even function of photon energy is crucial for analysis of these measurements and clarifies data presentation. In the region of high IR transparency of elemental semiconductors, the index may be expanded in a rapidly convergent Taylor series. Coefficients of terms in the (2n)^th power of energy are proportional to the (2n+1)^th inverse moment of the electronic absorption spectrum. In the favorable case of intrinsic Si, the electronic absorption is sufficiently well known that independent values of the intercept, slope and curvature of plots of index vs. the square of photon energy may be calculated. Index data sets with parameters significantly different from these suffer from systematic errors or refer to impure samples. Using these parity and sum-rule tests we have prepared a composite index data set for intrinsic silicon that represents a best fit to reliable measurements from microwaves to the visible. Applications to germanium and diamond will be discussed.

  9. Development of Negative Index of Refraction Metamaterials with Split Ring Resonators and Wires for RF Lens Applications

    NASA Astrophysics Data System (ADS)

    Parazzoli, Claudio G.; Greegor, Robert B.; Tanielian, M. H.

    Metamaterials are engineered ring and wire composites whose response to an incident electromagnetic wave can be described by an effective negative dielectric permittivity ɛ and magnetic permeability μ. Simultaneous negative ɛ and μ within a given frequency band of a metamaterial gives rise to a negative index of refraction n. This has been demonstrated via a Snell's law experiment. The electromagnetic properties of many metamaterial structures in the microwave region are investigated through numerical simulations and experiments. A negative index of refraction, n, allows lenses with reduced primary (Seidel) aberrations compared to equivalent positive index lens. This is demonstrated both for cylindrical lenses and spherical lenses, as well as for the gradient index lenses. Detailed field maps of the focal region of the metamaterials lenses are made and compared to a comparable positive index of refraction lens.

  10. Determining the unique refractive index properties of solid polystyrene aerosol using broadband Mie scattering from optically trapped beads.

    PubMed

    Jones, Stephanie H; King, Martin D; Ward, Andrew D

    2013-12-21

    A method is described to measure the refractive index dispersion with wavelength of optically trapped solid particles in air. Knowledge of the refraction properties of solid particles is critical for the study of aerosol; both in the laboratory and in the atmosphere for climate studies. Single micron-sized polystyrene beads were optically trapped in air using a vertically aligned counter-propagating configuration of focussed laser beams. Each bead was illuminated using white light from a broadband light emitting diode (LED) and elastic scattering within the bead was collected onto a spectrograph. The resulting Mie spectra were analysed to accurately determine polystyrene bead radii to 0.4 nm and values of the refractive index to 0.0005 over a wavelength range of 480-700 nm. We demonstrate that optical trapping combined with elastic scattering can be used to both accurately size polystyrene beads suspended in air and determine their wavelength dependent refractive index. The refractive index dispersions are in close agreement with reported values for polystyrene beads in aqueous dispersion. Our results also demonstrate a variation in the refractive index of polystyrene, from bead to bead, in a commercial sample. The measured variation highlights that care must be taken when using polystyrene beads as a calibration aerosol. PMID:24196002

  11. Finite element approximation of the radiative transport equation in a medium with piece-wise constant refractive index

    SciTech Connect

    Lehtikangas, O.; Tarvainen, T.; Kim, A.D.; Arridge, S.R.

    2015-02-01

    The radiative transport equation can be used as a light transport model in a medium with scattering particles, such as biological tissues. In the radiative transport equation, the refractive index is assumed to be constant within the medium. However, in biomedical media, changes in the refractive index can occur between different tissue types. In this work, light propagation in a medium with piece-wise constant refractive index is considered. Light propagation in each sub-domain with a constant refractive index is modeled using the radiative transport equation and the equations are coupled using boundary conditions describing Fresnel reflection and refraction phenomena on the interfaces between the sub-domains. The resulting coupled system of radiative transport equations is numerically solved using a finite element method. The approach is tested with simulations. The results show that this coupled system describes light propagation accurately through comparison with the Monte Carlo method. It is also shown that neglecting the internal changes of the refractive index can lead to erroneous boundary measurements of scattered light.

  12. Rapid assessment of mid-infrared refractive index anisotropy using a prism coupler: chemical vapor deposited ZnS.

    PubMed

    Qiao, H A; Lipschultz, Kristen A; Anheier, N C; McCloy, J S

    2012-05-01

    A state-of-the-art mid-infrared prism coupler was used to study suspected anisotropy in the refractive index of forward-looking-infrared grade chemical vapor deposited (CVD) zinc sulfide. Samples were prepared with columnar grain structure in and perpendicular to the sample plane, as well as from different depths in the CVD growth body. This study was motivated by the growing industry concern among optical design engineers, as well as developers of mid-infrared systems, over the reliability of historically accepted index data. Prior photoluminescence and x-ray diffraction measurements have suggested that refractive index may vary according to sample orientation with respect to the grain structure. Measurements were conducted to provide optical dispersion and thermal index (dn/dT) data at discrete laser wavelengths between 0.633 and 10.591 ?m at two temperature set points (30 C and 90 C). Refractive index measurements between samples exhibited an average standard deviation comparable to the uncertainty of the prism coupler measurement (0.0004 refractive index units), suggesting that the variation in refractive index as a function of sample orientation and CVD deposition time is negligible and should have no impact on subsequent optical designs. Measured dispersion data at mid-infrared wavelengths were also found to agree well with prior published measurements. PMID:22555685

  13. Exceptionally efficient organic light emitting devices using high refractive index substrates.

    PubMed

    Mladenovski, Saso; Neyts, Kristiaan; Pavicic, Domagoj; Werner, Ansgar; Rothe, Carsten

    2009-04-27

    Organic light emitting devices (OLEDs) are now used in commercial cell phones and flat screen displays, but may become even more successful in lighting applications, in which large area, high efficiency, long lifetime and low cost are essential. Due to the relatively high refractive index of the organic layers, conventional planar bottom emitting OLEDs have a low outcoupling efficiency. Various approaches for enhancing the optical outcoupling efficiency of bottom emitting OLEDs have been introduced in the literature. In this paper we demonstrate a green bottom emitting OLED with a record external quantum efficiency (42%) and luminous efficacy (183 lm/W). This OLED is based on a high index substrate and a thick electron transport layer (ETL) which uses electrical doping. The efficient light outcoupling is modeled by optical simulations. PMID:19399135

  14. Temperature insensitive refractive index sensor based on concatenated long period fiber gratings

    NASA Astrophysics Data System (ADS)

    Tripathi, Saurabh M.; Bock, Wojtek J.; Mikulic, Predrag

    2013-10-01

    We propose and demonstrate a temperature immune biosensor based on two concatenated LPGs incorporating a suitable inter-grating-space (IGS). Compensating the thermal induced phase changes in the grating region by use of an appropriate length of the IGS the temperature insensitivity has been achieved. Using standard telecommunication grade single-mode fibers we show that a length ratio of ~8.2 is sufficient to realize the proposed temperature insensitivity. The resulting sensor shows a refractive index sensitivity of 423.28 nm/RIU displaying the capability of detecting an index variation of 2.36 10-6 RIU in the bio-samples. The sensor can also be applied as a temperature insensitive WMD channel isolation filter in the optical communication systems, removing the necessity of any external thermal insulation packaging.

  15. Nonlinear index of refraction of Cu- and Pb-implanted fused silica

    SciTech Connect

    Haglund, R.F. Jr.; Magruder, R.H.; Weller, R.A.; Yang, L. ); Morgan, S.H.; Henderson, D.O. . Dept. of Physics); Zuhr, R.A. )

    1991-09-01

    We have measured the nonlinear index of refraction in high-purity fused silica implanted with Pb and Cu ions, using 100-ps pulses from a cw, mode-locked, frequency-doubled Nd:YAG laser ({lambda} = 532 nm). The nonlinear index measured for the Pb-implanted silica is an order of magnitude larger than that for Cu:silica. Qualitative evidence from infrared reflectance spectra suggests that these differences may result from distinctive ways in which these implanted ions are incorporated into the glass network: the Cu appears to form of nm-size colloids, while the Pb may be incorporated into a Pb-O-Si glassy phase. 13 refs., 4 figs.

  16. Nonlinear refractive index measurements and self-action effects in Roselle-Hibiscus Sabdariffa solutions

    NASA Astrophysics Data System (ADS)

    Henari, F. Z.; Al-Saie, A.

    2006-12-01

    We report the observation of self-action phenomena, such as self-focusing, self-defocusing, self-phase modulation and beam fanning in Roselle-Hibiscus Sabdariffa solutions. This material is found to be a new type of natural nonlinear media, and the nonlinear reflective index coefficient has been determined using a Z-scan technique and by measuring the critical power for the self-trapping effect. Z-scan measurements show that this material has a large negative nonlinear refractive index, n 2 = 1 10-4 esu. A comparison between the experimental n 2 values and the calculated thermal value for n 2 suggests that the major contribution to nonlinear response is of thermal origin.

  17. Conical photonic crystals for enhancing light extraction efficiency from high refractive index materials.

    PubMed

    Kim, Jeong-Gil; Hsieh, Chih-Hung; Choi, Hyungryul J; Gardener, Jules; Singh, Bipin; Knapitsch, Arno; Lecoq, Paul; Barbastathis, George

    2015-08-24

    We propose, analyze and optimize a two-dimensional conical photonic crystal geometry to enhance light extraction from a high refractive index material, such as an inorganic scintillator. The conical geometry suppresses Fresnel reflections at an optical interface due to adiabatic impedance matching from a gradient index effect. The periodic array of cone structures with a pitch larger than the wavelength of light diffracts light into higher-order modes with different propagating angles, enabling certain photons to overcome total internal reflection (TIR). The numerical simulation shows simultaneous light yield gains relative to a flat surface both below and above the critical angle and how key parameters affect the light extraction efficiency. Our optimized design provides a 46% gain in light yield when the conical photonic crystals are coated on an LSO (cerium-doped lutetium oxyorthosilicate) scintillator. PMID:26368241

  18. A bio-inspired polymeric gradient refractive index (GRIN) human eye lens.

    PubMed

    Ji, Shanzuo; Ponting, Michael; Lepkowicz, Richard S; Rosenberg, Armand; Flynn, Richard; Beadie, Guy; Baer, Eric

    2012-11-19

    A synthetic polymeric lens was designed and fabricated based on a bio-inspired, "Age=5" human eye lens design by utilizing a nanolayered polymer film-based technique. The internal refractive index distribution of an anterior and posterior GRIN lens were characterized and confirmed against design by µATR-FTIR. 3D surface topography of the fabricated aspheric anterior and posterior lenses was measured by placido-cone topography and exhibited confirmation of the desired aspheric surface shape. Furthermore, the wavefronts of aspheric posterior GRIN and PMMA lenses were measured and simulated by interferometry and Zemax software, respectively. Their results show that the gradient index distribution reduces the overall wavefront error as compared a homogenous PMMA lens of an identical geometry. Finally, the anterior and posterior GRIN lenses were assembled into a bio-inspired GRIN human eye lens through which a clear imaging was possible. PMID:23187529

  19. Measurements of the complex refractive index of volcanic ash at 450, 546.7, and 650 nm

    NASA Astrophysics Data System (ADS)

    Ball, J. G. C.; Reed, B. E.; Grainger, R. G.; Peters, D. M.; Mather, T. A.; Pyle, D. M.

    2015-08-01

    The detection and quantification of volcanic ash is extremely important to the aviation industry, civil defense organizations, and those in peril from volcanic ashfall. To exploit the remote sensing techniques that are used to monitor a volcanic cloud and return information on its properties, the effective complex refractive index of the volcanic ash is required. This paper presents the complex refractive index determined in the laboratory at 450.0 nm, 546.7 nm, and 650.0 nm for volcanic ash samples from eruptions of Aso (Japan), Grímsvötn (Iceland), Chaitén (Chile), Etna (Italy), Eyjafjallajökull (Iceland), Tongariro (New Zealand), Askja (Iceland), Nisyros (Greece), Okmok (Alaska), Augustine (Alaska), and Spurr (Alaska). The Becke line method was used to measure the real part of the refractive index with an accuracy of 0.01. The values measured differed between eruptions and were in the range 1.51-1.63 at 450.0 nm, 1.50-1.61 at 546.7 nm, and 1.50-1.59 at 650.0 nm. A novel method is introduced to derive the imaginary part of the refractive index from the attenuation of light by ash. The method has a precision in the range 10-3-10-4. The values for the ash imaginary refractive index ranged 0.22-1.70 × 10-3 at 450.0 nm, 0.16-1.93 × 10-3 at 546.7 nm, and 0.15-2.08 × 10-3 at 650.0 nm. The accuracy of Becke and attenuation methods was assessed by measuring the complex refractive index of Hoya neutral density glass and found to have an accuracy of <0.01 and <2 × 10-5 for the real and imaginary parts of the refractive index, respectively.

  20. Rapid assessment of mid-infrared refractive index anisotropy using a prism coupler: chemical vapor deposited ZnS

    SciTech Connect

    Qiao, Hong; Lipschultz, Kristen A.; Anheier, Norman C.; McCloy, John S.

    2012-04-01

    A state-of-the-art mid-infrared prism coupler was used to study the refractive index properties of forward-looking-infrared (FLIR) grade zinc sulfide samples prepared with unique planar grain orientations and locations with respect to the CVD growth axis. This study was motivated by prior photoluminescence and x-ray diffraction measurements that suggested refractive index may vary according to grain orientation. Measurements were conducted to provide optical dispersion and thermal index (dn/dT) data at discrete laser wavelengths between 0.633 and 10.591 {mu}m at two temperature set points (30 C and 90 C). Refractive index measurements between samples exhibited an average standard deviation comparable to the uncertainty of the prism coupler measurement (0.0004 refractive index units), suggesting that the variation in refractive index as a function of planar grain orientation and CVD deposition time is negligible, and should have no impact on subsequent optical designs. Measured dispersion data at mid-infrared wavelengths was found to agree well with prior published measurements.

  1. Alteration in refractive index profile during accommodation based on mechanical modelling.

    PubMed

    Bahrami, Mehdi; Heidari, Ali; Pierscionek, Barbara K

    2016-01-01

    The lens of the eye has a gradient refractive index (GRIN). Ocular accommodation, which alters the shape of the lens in response to visual demand, causes a redistribution of the internal structure of the lens leading to a change in the GRIN profile. The nature of this redistribution and the consequence of change in the GRIN profile are not understood. A modelling approach that considers how the GRIN profile may change with accommodation needs to take into account optical and mechanical parameters and be cognisant of individual variability in the shape and size of lenses. This study models the normalised axial GRIN profile during accommodation using reduced modelling and incorporating finite element analysis to connect inhomogenous mechanical characteristics of the lens to optical performance. The results show that simulated stretching changes the length of the plateau but does not alter the cortical gradient, which supports clinical findings. There is a very small change to the accommodated and non-accommodated profiles when normalised, yet this yields measurable changes in aberrations with around 11% and almost 13% difference in spherical aberration and astigmatism respectively. The results can be used in reconstruction of the refractive index and for investigating gradual changes with age. PMID:26819821

  2. Effect of binders on the damage threshold and refractive index of coatings prepared from colloidal suspensions

    SciTech Connect

    Thomas, I.M.

    1992-10-01

    Addition of polyvinyl alcohol (PVA) to aqueous suspensions of AlOOH, ZrO2 and HfO[sub 2] has been found to increase the damage threshold and refractive index of coatings prepared from these suspensions. The increase in damage threshold may be due to the increase in coating strength brought about by the enhanced particle-to-particle bond strength due to the polymer binder. The binder also increases the refractive index by decreasing the porosity. This leads to a reduction in the number of layer pairs required for high reflection in a typical HR coating. A mirror consisting of only ten layer pairs of HfO[sub 2]-SiO[sub 2] with PVA binder in the HfO[sub 2] had a reflectivity of over 99% at 1.06 [mu]m and a damage threshold of 25-28 J/cm[sup 2]at 1.06 [mu]m with a 10 ns pulse. 6 refs, 5 figs, 4 tabs.

  3. Effect of binders on the damage threshold and refractive index of coatings prepared from colloidal suspensions

    SciTech Connect

    Thomas, I.M.

    1992-10-01

    Addition of polyvinyl alcohol (PVA) to aqueous suspensions of AlOOH, ZrO2 and HfO{sub 2} has been found to increase the damage threshold and refractive index of coatings prepared from these suspensions. The increase in damage threshold may be due to the increase in coating strength brought about by the enhanced particle-to-particle bond strength due to the polymer binder. The binder also increases the refractive index by decreasing the porosity. This leads to a reduction in the number of layer pairs required for high reflection in a typical HR coating. A mirror consisting of only ten layer pairs of HfO{sub 2}-SiO{sub 2} with PVA binder in the HfO{sub 2} had a reflectivity of over 99% at 1.06 {mu}m and a damage threshold of 25-28 J/cm{sup 2}at 1.06 {mu}m with a 10 ns pulse. 6 refs, 5 figs, 4 tabs.

  4. Measurement of nonlinear refractive index of organic materials by z-scan

    NASA Astrophysics Data System (ADS)

    Fontalvo, M.; Garcia, A.; Valbuena, S.; Racedo, F.

    2016-02-01

    The nonlinear effects characterization by using the Z-Scan transmission technique in many materials has generated great in forest according to the technological necessities. The majority part of the nonlinear effects can be described by the classic electromagnetic theory, with the electrical susceptibility in the constitutive equation that relates the electrical polarization with the electrical field. In this work the sign and refractive index magnitude and the nonlinear absorption coefficient of the following organic substance were determined: methylene-blue, rodamine LD, vegetable powder and gentian violet a hundred percent pure dissolved in isopropyl alcohol, a laser Nd: YAG was used as a source excitation. The bunch of laser was focused with a lens of ten centimeters of focal length; by using a displacement system the sweeping of twenty centimeters was realized. The following results of the normalized curves of the transmittance in function of the z position were obtained applying the Sheik- Bahae theory: The nonlinear refractive index of the dye shows an increase in function of its concentration and the power of exciting of the laser with negative nonlinear sign in the majority of the sample.

  5. Fabrication of Refractive Index Tunable Polydimethylsiloxane Photonic Crystal for Biosensor Application

    NASA Astrophysics Data System (ADS)

    Raman, Karthik; Murthy, T. R. Srinivasa; Hegde, G. M.

    Photonic crystal based nanostructures are expected to play a significant role in next generation nanophotonic devices. Recent developments in two-dimensional (2D) photonic crystal based devices have created widespread interest as such planar photonic structures are compatible with conventional microelectronic and photonic devices. Various optical components such as waveguides, resonators, modulators and demultiplexers have been designed and fabricated based on 2D photonic crystal geometry. This paper presents the fabrication of refractive index tunable Polydimethylsiloxane (PDMS) polymer based photonic crystals. The advantages of using PDMS are mainly its chemical stability, bio-compatibility and the stack reduces sidewall roughness scattering. The PDMS structure with square lattice was fabricated by using silicon substrate patterned with SU8-2002 resist. The 600 nm period grating of PDMS is then fabricated using Nano-imprinting. In addition, the refractive index of PDMS is modified using certain additive materials. The resulting photonic crystals are suitable for application in photonic integrated circuits and biological applications such as filters, cavities or microlaser waveguides.

  6. Liposomes with High Refractive Index Encapsulants as Tunable Signal Amplification Tools in Surface Plasmon Resonance Spectroscopy.

    PubMed

    Fenzl, Christoph; Hirsch, Thomas; Baeumner, Antje J

    2015-11-01

    One major goal in the surface plasmon resonance (SPR) technique is the reliable detection of small molecules as well as low analyte concentrations. This can be achieved by a viable signal amplification strategy. We therefore investigated optimal liposome characteristics for use as a signal enhancement system for SPR sensors, as liposomes excel not only at versatility but also at colloidal stability and ease of functionalization. These characteristics include the encapsulation of high refractive index markers, lipid composition, liposome size, and surface modifications to best match the requirements of the SPR system. Our studies of the binding of biotinylated liposomes to surface-immobilized streptavidin show that the refractive index of the encapsulant has a major influence on the SPR signal and outweighs the influence of the thin lipid bilayer. Thus, the signal amplification properties of liposomes can be adjusted to the respective needs of any analytical task by simply exchanging the encapsulant solution. In this work, a maximum enhancement factor of 23 was achieved by encapsulating a 500 mM sucrose solution. Dose-response studies with and without liposome enhancement revealed an improvement of the limit of detection from 10 nmol L(-1) to 320 pmol L(-1) streptavidin concentration with a much higher sensitivity of 3 mRIU per logarithmic unit of the concentration between 500 pmol L(-1) and 10 nmol L(-1). PMID:26455696

  7. PIV Measurements of Turbulent Flow Over a Permeable Wall using a Refractive-Index Matching Approach

    NASA Astrophysics Data System (ADS)

    Kim, T.; Blois, G.; Best, J. L.; Christensen, K. T.

    2013-11-01

    Turbulent flows over permeable walls occur in a variety of natural environments and engineering applications. Unlike classical and widely-studied flows over impermeable walls, the peculiar dynamics of flow generated by permeable walls are poorly understood. Early studies suggest that the well-known higher energy dissipation induced by permeability (as compared to impermeable walls with similar roughness) can be explained by unveiling the flow interactions within the transition layer that forms at the interface between the overlying flow and the permeable wall. To overcome the challenges associated with quantifying the flow character both above and within a permeable wall, a Refractive-Index-Matching (RIM) approach was employed. Doing so facilitated optical access to the fluid flowing through the permeable wall, thus yielding direct PIV pore-space flow measurements within the transition layer. The permeable wall was formed by packing acrylic spheres in a cubic arrangement and was then immersed in an aqueous solution of sodium iodide at a concentration and temperature that ensured accurate refractive index match with the wall. Measurements were focused on the flow across the wall interface and the turbulent attributes of these surface-subsurface interactions were detailed.

  8. Effective group index of refraction in non-thermal plasma photonic crystals

    NASA Astrophysics Data System (ADS)

    Mousavi, A.; Sadegzadeh, S.

    2015-11-01

    Plasma photonic crystals (PPCs) are periodic arrays that consist of alternate layers of micro-plasma and dielectric. These structures are used to control the propagation of electromagnetic waves. This paper presents a survey of research on the effect of non-thermal plasma with bi-Maxwellian distribution function on one dimensional PPC. A plasma with temperature anisotropy is not in thermodynamic equilibrium and can be described by the bi-Maxwellian distribution function. By using Kronig-Penny's model, the dispersion relation of electromagnetic modes in one dimensional non-thermal PPC (NPPC) is derived. The band structure, group velocity vg, and effective group index of refraction neff(g) of such NPPC structure with TeO2 as the material of dielectric layers have been studied. The concept of negative group velocity and negative neff(g), which indicates an anomalous behaviour of the PPCs, are also observed in the NPPC structures. Our numerical results provide confirmatory evidence that unlike PPCs there are finite group velocity and non-zero effective group indexes of refraction in photonic band gaps (PBGs) that lie in certain ranges of normalized frequency. In other words, inside the PBGs of NPPCs, neff(g) becomes non-zero and photons travel with a finite group velocity. In this special case, this velocity varies alternately between 20c and negative values of the order 103c (c is the speed of light in vacuum).

  9. Fabry-Perot interferometer based on etched side-hole fiber for microfluidic refractive index sensing

    NASA Astrophysics Data System (ADS)

    Wu, Shengnan; Yan, Guofeng; Zhou, Bin; He, Sailing

    2015-08-01

    In this paper, we present a novel fiber-optic open-cavity Fabry-Perot interferometer (FPI), which is specially designed for microfluidic refractive index (RI) sensing. An etching Side-hole fiber (SHF) was sandwiched between in two single-mode-fibers (SMF) and then a cavity was opened up by chemical etching method in the SHF. The minute order of the etching process endow such FPIs with low cost and ease of fabrication. For further microfluidic sensing test, the FPI was integrated with a cross microfluidic slit that was fabricated through photolithography. The refractive index response of the FPI was characterized using sodium hydroxide solution with RI range from 1.3400 to 1.3470. Experimental results show that FPIs with different length of open-cavity have the similar liner RI response with different RI sensitivities. The optimal RI sensitivity of more than 1138 nm/RI can be achieved with open-cavity length of 56 μm. The temperature response was also investigated, which shows that FPIs exhibit a very low temperature cross-sensitivities of 4.00 pm/ °C and 1.95 pm/ °C corresponding FPIs with cavity length of 123 μm and 56 μm, respectively. Such good performance renders the FPI a promising in-line microfluidic sensor for temperature-insensitive RI sensing.

  10. CMOS image sensor-based immunodetection by refractive-index change.

    PubMed

    Devadhasan, Jasmine P; Kim, Sanghyo

    2012-01-01

    A complementary metal oxide semiconductor (CMOS) image sensor is an intriguing technology for the development of a novel biosensor. Indeed, the CMOS image sensor mechanism concerning the detection of the antigen-antibody (Ag-Ab) interaction at the nanoscale has been ambiguous so far. To understand the mechanism, more extensive research has been necessary to achieve point-of-care diagnostic devices. This research has demonstrated a CMOS image sensor-based analysis of cardiovascular disease markers, such as C-reactive protein (CRP) and troponin I, Ag-Ab interactions on indium nanoparticle (InNP) substrates by simple photon count variation. The developed sensor is feasible to detect proteins even at a fg/mL concentration under ordinary room light. Possible mechanisms, such as dielectric constant and refractive-index changes, have been studied and proposed. A dramatic change in the refractive index after protein adsorption on an InNP substrate was observed to be a predominant factor involved in CMOS image sensor-based immunoassay. PMID:22975915

  11. Method of time resolved refractive index measurements of x-ray laser heated solids

    SciTech Connect

    Williams, G. O.; Kuenzel, S.; Fajardo, M.; Vinko, S. M.; Sardinha, A. B.; Zeitoun, Ph.

    2013-04-15

    With the advent of new x-ray light-sources worldwide, the creation of dense, uniformly heated plasma states arising from intense x-ray irradiation of solids has been made possible. In the early stages of x-ray solid heating, before significant hydrodynamic motion occurs, the matter exists in a highly non-equilibrium state. A method based on wavefront sensing is proposed to probe some of the fundamental properties of these states. The deflection and absorption of a high harmonic probe beam propagated through the plasma can be measured with a wavefront sensor, and allow for the determination of the complex refractive index (RI) of the plasma, giving a 2D map of the optical properties as function of time in a pump-probe arrangement. A solid heating model has been used to estimate the expected temperatures of x-ray heated thin foils, and these temperatures are used in three separate models to estimate the changes in the refractive index. The calculations show the changes induced on an extreme ultra-violet (XUV) probe beam by a solid density thin foil plasma are significant, in terms of deflection angle and absorption, to be measured by already existing XUV Hartmann wavefront sensors. The method is applicable to a wide range of photon energies in the XUV (10 s to several 100 s of eV) and plasma parameters, and can add much needed experimental data to the fundamental properties of such dense plasma states.

  12. Vacuum energy and the spacetime index of refraction: A new synthesis

    SciTech Connect

    Nouri-Zonoz, M.; Nazari, B.

    2010-08-15

    In 1+3 (threading) formulation of general relativity spacetime behaves analogous to a medium with a specific index of refraction with respect to the light propagation. Accepting the reality of zero-point energy, through the equivalence principle, we elevate this analogy to the case of virtual photon propagation in a quantum vacuum in a curved background spacetime. Employing this new idea (conjecture) one could examine the response of vacuum energy to the presence of a weak stationary gravitational field in its different quantum field theoretic manifestations such as Casimir effect and Lamb shift. As an evidence in favor of the proposed conjecture, employing quantum field theory in curved spacetime, we explicitly calculate the effect of a weak static gravitational field on virtual massless scalar particles in a Casimir apparatus. It is shown that, as expected from the proposed conjecture, both the frequency and renormalized energy of the virtual scalar field are affected by the gravitational field through its index of refraction. Generalizations to weak stationary spacetimes and virtual photons are also discussed.

  13. TCF-MMF-TCF fiber structure based interferometer for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Fu, Haiwei; Li, Huidong; Shao, Min; Zhao, Na; Liu, Yinggang; Li, Yan; Yan, Xu; Liu, Qinpeng

    2015-06-01

    A liquid refractive index (RI) sensor based on in-fiber Mach-Zehnder interferometer (MZI) by sandwiching multi-mode fiber (MMF) between two short sections of thinned core fiber (TCF) is proposed in this paper. The first section of TCF excites the high-order modes and the second section TCF couples the core mode and high-order modes into lead-out SMF to form intermodal interference. The sensor with MMF length of 20 mm and TCFs length of 1 mm was fabricated. The transmission spectrum variation of the sensor with respect to surrounding refractive index (SRI) has been studied by experiment. The results show that the central wavelength of dips/peaks shifting had a good linearity with SRI. The RI sensitivity of the sensor is 130.00 nm/RIU over the RI range of 1.3333-1.4182. The RI sensitivity increase to 433.60 nm/RIU after etching the MMF cladding of the sensor. The sensor keeps low dependence on temperature before and after etching.

  14. Index of refraction and its temperature dependence of calcium fluoride near 157 nm

    NASA Astrophysics Data System (ADS)

    Burnett, John H.; Gupta, Rajeev; Griesmann, Ulf; Jou, Ted E.

    1999-07-01

    We have made accurate measurement near 157 nm of the relative index of refraction, its dispersion, and its temperature dependence for two grades of calcium fluoride in N2 gas. Accurate measurements of these quantities are needed for the design of lens system for 157 nm F2 excimer-laser-based exposure tools for photolithography. These optical properties were measured with precision goniometer on prisms of the materials in a N2 atmosphere using the minimum deviation method. The dispersion was determined using line emission radiation from a deuterium lamp at several wavelengths near 157 nm. Values of the relative refractive index for two grades of calcium fluoride in N2 gas corrected to a temperature of 20 degrees C and a pressure of one standard atmosphere are well within our 7 ppm estimated uncertainty forth measurements. The temperature of the samples and the surrounding medium were controlled to 0.05 degrees C, which enabled accurate measurements of the temperature dependencies of the indices around room temperature near 157 nm.

  15. Alteration in refractive index profile during accommodation based on mechanical modelling

    PubMed Central

    Bahrami, Mehdi; Heidari, Ali; Pierscionek, Barbara K.

    2015-01-01

    The lens of the eye has a gradient refractive index (GRIN). Ocular accommodation, which alters the shape of the lens in response to visual demand, causes a redistribution of the internal structure of the lens leading to a change in the GRIN profile. The nature of this redistribution and the consequence of change in the GRIN profile are not understood. A modelling approach that considers how the GRIN profile may change with accommodation needs to take into account optical and mechanical parameters and be cognisant of individual variability in the shape and size of lenses. This study models the normalised axial GRIN profile during accommodation using reduced modelling and incorporating finite element analysis to connect inhomogenous mechanical characteristics of the lens to optical performance. The results show that simulated stretching changes the length of the plateau but does not alter the cortical gradient, which supports clinical findings. There is a very small change to the accommodated and non-accommodated profiles when normalised, yet this yields measurable changes in aberrations with around 11% and almost 13% difference in spherical aberration and astigmatism respectively. The results can be used in reconstruction of the refractive index and for investigating gradual changes with age. PMID:26819821

  16. Extraction of light trapped due to total internal reflection using porous high refractive index nanoparticle films

    NASA Astrophysics Data System (ADS)

    Mao, Peng; Sun, Fangfang; Yao, Hanchao; Chen, Jing; Zhao, Bo; Xie, Bo; Han, Min; Wang, Guanghou

    2014-06-01

    TiO2 nanoparticle layers composed of columnar TiO2 nanoparticle piles separated with nanoscale pores were fabricated on the bottom surface of the hemispherical glass prism by performing gas phase cluster beam deposition at glancing incidence. The porosity as well as the refractive index of the nanoparticle layer was precisely tuned by the incident angle. Effective extraction of the light trapped in the substrate due to total internal reflection with the TiO2 nanoparticle layers was demonstrated and the extraction efficiency was found to increase with the porosity. An enhanced Rayleigh scattering mechanism, which results from the columnar aggregation of the nanoparticles as well as the strong contrast in the refractive index between pores and TiO2 nanoparticles in the nanoporous structures, was proposed. The porous TiO2 nanoparticle coatings were fabricated on the surface of GaN LEDs to enhance their light output. A nearly 92% PL enhancement as well as a 30% EL enhancement was observed. For LED applications, the enhanced light extraction with the TiO2 nanoparticle porous layers can be a supplement to the microscale texturing process for light extraction enhancement.

  17. Coherent control of refractive index in far-detuned {Lambda} systems

    SciTech Connect

    O'Brien, Chris; Anisimov, Petr M.; Rostovtsev, Yuri; Kocharovskaya, Olga

    2011-12-15

    Enhancement and control of the index of refraction in a mixture of two three-level atomic species that form a pair of far-detuned {Lambda} schemes under two-photon resonance has been studied. We employ the density-matrix approach to properly take population relaxation into account and to describe the interaction of each {Lambda} system with the electromagnetic fields. Both {Lambda} systems are driven by a corresponding far-detuned coherent field at one atomic transition and are probed by the same weak field. In the dressed-state basis, it represents a superposition of effective two-level subsystems with the positions, widths, and amplitudes of the resonances controlled by the driving fields and allows for efficient control of the susceptibility of the total system; leading to refractive index (RI) enhancement with vanishing absorption in the absence of amplification. We analyze the experimental implementation of such a system in a cell of Rb atoms with a natural abundance of isotopes. An upper limit estimate of the RI enhancement is obtained.

  18. CdSe/ZnS quantum dots as sensors for the local refractive index.

    PubMed

    Aubret, Antoine; Pillonnet, Anne; Houel, Julien; Dujardin, Christophe; Kulzer, Florian

    2016-01-21

    We explore the potential of CdSe/ZnS colloidal quantum dots (QDs) as probes for their immediate dielectric environment, based on the influence of the local refractive index on the fluorescence dynamics of these nanoemitters. We first compare ensembles of quantum dots in homogeneous solutions with single quantum dots dispersed on various dielectric substrates, which allows us to test the viability of a conceptual framework based on a hard-sphere region-of-influence and the Bruggeman effective-medium approach. We find that all our measurements can be integrated into a coherent description, provided that the conceptualized point-dipole emitter is positioned at a distance from the substrate that corresponds to the geometry of the QD. Three theoretical models for the evolution of the fluorescence decay rate as a function of the local refractive index are compared, showing that the classical Lorentz approach (virtual cavity) is the most appropriate for describing the data. Finally, we use the observed sensitivity of the QDs to their environment to estimate the detection limit, expressed as the minimum number of traceable streptavidin molecules, of a potential QD-nanosensor based on fluorescence lifetime. PMID:26750539

  19. Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing

    PubMed Central

    Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M.

    2015-01-01

    Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33–1.37) suitable for biosensing applications. PMID:26426022

  20. Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

    PubMed

    Klantsataya, Elizaveta; Franois, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

    2015-01-01

    Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 ?m diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 ?m core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications. PMID:26426022