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1

Full field imaging based instantaneous hyperspectral absolute refractive index measurement  

SciTech Connect

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.

Baba, Justin S [ORNL; Boudreaux, Philip R [ORNL

2012-01-01

2

High Accuracy, Absolute, Cryogenic Refractive Index Measurements of Infrared Lens Materials for JWST NIRCam using CHARMS  

NASA Technical Reports Server (NTRS)

The current refractive optical design of the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam) uses three infrared materials in its lenses: LiF, BaF2, and ZnSe. In order to provide the instrument s optical designers with accurate, heretofore unavailable data for absolute refractive index based on actual cryogenic measurements, two prismatic samples of each material were measured using the cryogenic, high accuracy, refraction measuring system (CHARMS) at NASA GSFC, densely covering the temperature range from 15 to 320 K and wavelength range from 0.4 to 5.6 microns. Measurement methods are discussed and graphical and tabulated data for absolute refractive index, dispersion, and thermo-optic coefficient for these three materials are presented along with estimates of uncertainty. Coefficients for second order polynomial fits of measured index to temperature are provided for many wavelengths to allow accurate interpolation of index to other wavelengths and temperatures.

Leviton, Douglas; Frey, Bradley

2005-01-01

3

Temperature-dependent Absolute Refractive Index Measurements of Synthetic Fused Silica  

NASA Technical Reports Server (NTRS)

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.

Leviton, Douglas B.; Frey, Bradley J.

2006-01-01

4

Absolute calibration of the refractive index in photo-induced photonic lattices  

NASA Astrophysics Data System (ADS)

We demonstrate a method to experimentally calibrate the refractive index modulation in photorefractive lattices, a task rarely addressed that is crucial for quantitative comparisons of theories with experiments. We consider the linear propagation of a normally incident plane wave through simple lattices and its modulation amplitude at crystal output face. Finding no evidence of longitudinal (Talbot-like) oscillations, we discard an ideal propagation theory and construct a simple effective model that includes longitudinal relaxation. We obtain calibrations of 1D and 2D lattices consistent with standard theory in a high saturation regime. For 2D lattices, we find anisotropies $\\chi=1.5- 2.5$, stronger for smaller lattice period, and refractive indexes larger than for 1D lattices, also with more noise.

Armijo, Julien; Allio, Raphaël; Mejía-Cortés, Cristian

2014-08-01

5

The Index of Refraction  

NSDL National Science Digital Library

In this media-rich lesson plan, students explore the refraction of light at the boundary between materials: they learn about the refractive indices of various materials and measure the index of refraction of plastic or gelatin.

Foundation, Wgbh E.

2011-10-25

6

Gradient Refractive Index Lenses.  

ERIC Educational Resources Information Center

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)

Morton, N.

1984-01-01

7

Application of the Monte-Carlo refractive index matching (MCRIM) technique to the determination of the absolute light yield of a calcium molybdate scintillator  

NASA Astrophysics Data System (ADS)

The use of 40Ca100MoO in experimental searches for neutrinoless double beta decay (0?DBD) relies on knowledge of fundamental scintillation properties of the material. In this work we determine the absolute light yield of calcium molybdate using Monte-Carlo refractive index matching technique (MCRIM). The MCRIM technique is a combination of experiment and simulations that allows the absolute light yield of scintillators to be determined by taking into account effects of refraction, scattering and absorption in the material. The light collection efficiency of the scintillator-detector assembly was simulated using the ZEMAX ray-tracing software. By tuning the optical parameters of the scintillation crystal, a model was derived that gives good agreement with the experimental results. It is shown that the light collection efficiency of scintillators increases with transmittance and scattering due to an enhanced probability for photons to escape the crystal volume. Using MCRIM, the absolute light yield for the 40Ca100MoO4 scintillator was found to be 7.5±1.2 ph/keV at room temperature. Comparative measurements using a CaWO4 scintillator as a reference show good agreement with this result. In that way, the study demonstrated the potential of the MCRIM technique as a tool for quantitative characterization of scintillation materials.

Alenkov, V.; Buzanov, O. A.; Khanbekov, N.; Kornoukhov, V. N.; Kraus, H.; Mikhailik, V. B.; Shuvaeva, V. A.

2013-06-01

8

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)

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.

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

2013-03-01

9

Fabrication of gradient refractive index ball lenses  

NASA Astrophysics Data System (ADS)

The theoretical model of the Maxwell fish eye sphere lens has long been regarded as an absolute optical instrument without practical application since it was proposed. But the study on the theory of Maxwell fish eye micro-spherical lens shows that at certain condition it has fine image formation ability and coupling efficiency. Based on the Fick's diffusion equations, the distribution function of refractive index of gradient refractive index (GRIN) ball lenses is derived. Lithium-containing silicate glass is fabricated and GRIN ball lenses whose diameters are from 0.3 to 3.0 mm are made by ion exchange and the sagging method in sodium nitrate. Radial refractive index profiles of these GRIN ball lens are measured by interferometer. Results show that the distribution of the index of refraction is a parabolic curve and in concordance with the computational consequence and its ? n is 0.0002.

Lv, Hao; Shi, Bangren; Wu, Jijiang; Guo, Lijun; Liu, Aimei

2008-03-01

10

Fiber optic refractive index monitor  

DOEpatents

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.

Weiss, Jonathan David (Albuquerque, NM)

2002-01-01

11

Measuring the Index of Refraction.  

ERIC Educational Resources Information Center

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)

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

1980-01-01

12

Negative Index of Refraction Portland State University  

E-print Network

, because I thought a negative index of refraction would simply be a reflection, as it would have a negativeNegative Index of Refraction Portland State University PH 464--Dr. Andres LaRosa Joel Rieger March not only showed that these materials have a negative index of refraction, he also showed

La Rosa, Andres H.

13

Tunable negative refractive index metamaterial phase shifter  

Microsoft Academic Search

A novel waveguiding ferrite phase shifter utilizing negative refractive index metamaterial is demonstrated, which is the first device application of negative refractive index metamaterial of its kind. The negative index metamaterial is positioned at middle of the waveguide along the longitude direction, which is composed by a periodic copper wire pattern sandwiched by two pieces of high quality yttrium iron

Peng He; P. V. Parimi; H. Mosallaei; V. G. Harris; C. Vittoria

2007-01-01

14

Make That Invisible! Refractive Index Matching  

NSDL National Science Digital Library

Students determine the refractive index of a liquid with a simple technique using a semi-circular hollow block. Then they predict the refractive index of a material (a Pyrex glass tube) by matching it with the known refractive index of a liquid using the percent light transmission measurement. The homemade light intensity detector uses an LED and multimeter, which are relatively inexpensive (and readily available) compared to commercially available measurement instruments.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

15

Negative index of refraction in optical metamaterials  

Microsoft Academic Search

A double-periodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range. Such behavior results from the plasmon resonance in the pairs of nanorods for both the electric and the magnetic components of light. The refractive index is retrieved from direct phase and amplitude measurements for transmission and reflection, which are

Vladimir M. Shalaev; Wenshan Cai; Uday K. Chettiar; Hsiao-Kuan Yuan; Andrey K. Sarychev; Vladimir P. Drachev; Alexander V. Kildishev

2005-01-01

16

Refractive index of plant cell walls  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

17

Refractive-index-based optofluidic particle manipulation  

NASA Astrophysics Data System (ADS)

This letter describes optofluidic particle manipulation based on the refractive index contrast between the particle and the surrounding medium. A laser beam propagated along one sidewall of a microfluidic channel will introduce a force that pushes a high-refractive-index particle toward the Gaussian-shaped laser beam center axis. By contrast, a low-refractive-index particle will be pushed away from the beam center axis and toward the other sidewall of the channel because the direction of the gradient forces acting on such a particle is opposite the direction of the forces acting on a high-refractive-index particle. The gradient forces acting on a particle were calculated to predict and interpret the particle behavior. High-refractive-index and low-refractive-index particles, prepared from polystyrene latex (PSL) and hollow glass particles with refractive indices of 1.59 and 1.22, respectively, were employed. The PSL and hollow glass particles could be separated based on their refractive indices. Doubly attached identical particles behaved as a single particle.

Soo Lee, Kang; Heon Lee, Kyung; Bok Kim, Sang; Ho Jung, Jin; Hang Ha, Byung; Jin Sung, Hyung; Soo Kim, Sang

2013-08-01

18

Planar distributed structures with negative refractive index  

Microsoft Academic Search

Planar distributed periodic structures of microstrip-line and stripline types, which support left-handed (LH) waves are presented and their negative refractive index (NRI) properties are shown theoretically, numerically, and experimentally. The supported LH wave is fully characterized based on the composite right\\/left-handed transmission-line theory and the dispersion characteristics, refractive indexes, and Bloch impedance are derived theoretically. In addition, formulas to extract

Atsushi Sanada; Christophe Caloz; Tatsuo Itoh

2004-01-01

19

Negative Refractive Index Metamaterials: Principles and Applications  

Microsoft Academic Search

Abstract – We review structures for ,microwave and optical range,containing 'left-handed' metamaterials ,– artificial composites with simultaneously negative effective permittivity and permeability which achieve negative values of refractive index. Attention has been given to the fundamentals of negative index materials, the main design strategies and proposed applications which includesubw avelength resonant cavities, sub- diffraction limited near-field lenses (superlenses) and ,phase

Zoran Jakši?; Nils Dalarsson; Milan Maksimovi?

2006-01-01

20

Temperature-dependent Refractive Index of Silicon and Germanium  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

21

Cosmology with a dark refraction index  

SciTech Connect

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.

Chen, B.; Kantowski, R. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks, Room 100, Norman, Oklahoma 73019 (United States)

2008-08-15

22

Matched Index of Refraction Flow Facility  

ScienceCinema

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.

Mcllroy, Hugh

2013-05-28

23

Refractive index sensor based on terahertz multimode interference fiber device  

NASA Astrophysics Data System (ADS)

A fiber-optic refractive index sensor based on terahertz multimode interference in a singlemode-multimode-singlemode fiber structure (SMS) is numerically demonstrated for the first time in the literature. The shift of spectral transmission is investigated as function of external refractive index. Moreover, the coupling efficiency between optical modes at singlemode and multimode sections are determined. The proposed sensor reaches average sensitivity of ~5 GHz/RIU (refractive index unit) over a refractive index range of 1.4-1.5.

Cruz, Alice L. S.; Migliano, Antonio C. C.; Franco, Marcos A. R.

2013-05-01

24

Tissue refractive index as marker of disease  

NASA Astrophysics Data System (ADS)

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.

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

2011-11-01

25

Scanning focused refractive-index microscopy.  

PubMed

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

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

26

Scanning focused refractive-index microscopy  

PubMed Central

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

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

27

Light confinement via periodic modulation of the refractive index  

E-print Network

Light confinement via periodic modulation of the refractive index A Alberucci1,4 , L Marrucci2 and numerically, light confine- ment in dielectric structures with a transverse refractive index distribution pe and managing light signals and beams. The periodic modulation of the refractive index in the propagation

Marrucci, Lorenzo

28

Note: Index of refraction measurement using the Fresnel equations  

NASA Astrophysics Data System (ADS)

The real part of the refractive index is measured from 1.30 to above 3.00 without the use of index matching fluids. This approach expands upon the Brewster angle technique as both S and P polarized lights are used and the full Fresnel equations fitted to the data to extract the index of refraction using nonlinear curve fitting.

McClymer, J. P.

2014-08-01

29

Refractive index fiber sensor based on Brillouin fast light  

NASA Astrophysics Data System (ADS)

A new type of refractive index fiber sensor was invented by combining the evanescent-field scattering sensing mechanism with the Brillouin fast light scheme. Superluminal light was realized using Brillouin lasing oscillation in a fiber ring cavity. The refractive index of the solution around the microfiber within the cavity is related to the group velocity of the fast light. This fast light refractive index sensor offers an alternative for high-accuracy sensing applications.

Chen, Jiali; Gan, Jiulin; Zhang, Zhishen; Yang, Tong; Deng, Huaqiu; Yang, Zhongmin

2014-01-01

30

Fiber in-line Michelson Interferometer for refractive index sensing  

NASA Astrophysics Data System (ADS)

A fiber in-line Michelson interferometer based on open micro-cavity is demonstrated, which is fabricated by femtosecond laser micromachining and thin film coating technique. In refractive index sensing, this interferometer operates in a reflection mode of detection, exhibits compact sensor head, good mechanical reliability, wide operation range and high sensitivity of 975nm/RIU (refractive index unit) at the refractive index value of 1.484.

Liao, C. R.; Wang, D. N.; Wang, Min; Yang, Minghong; Wang, Yiping

2013-09-01

31

The refractive index of non-absorbing nanofluids and applications  

NASA Astrophysics Data System (ADS)

We present a brief overview of using the effective refractive index of colloidal suspensions for characterizing nanoparticles. We focus our analysis on the so-called nanofluids consisting of nanoparticles suspended in a homogenous liquid matrix. Particular attention is paid to the role of the real part of the effective refractive index on sizing the nanoparticles. We then discuss possible ways to measure the real part of the effective refractive index of nanofluids and precautions needed.

García-Valenzuela, Augusto; Contreras-Tello, Humberto; Sánchez-Pérez, C.; Márquez-Islas, R.; Barrera, R. G.

2014-08-01

32

Direct measurement of refractive-index dispersion of transparent media by white-light interferometry  

Microsoft Academic Search

We report on a technique for measuring the refractive indices of nonabsorbing media over a broad spectral range from 0.5 to 5 mum. White-light interferometry based on a double-interferometer system consisting of a fixed Mach-Zehnder interferometer and a Fourier-transform spectrometer is used for direct measurement of the absolute rotation-dependent phase shift induced by an optical element. Refractive index n(lambda) over

Matteo Galli; Franco Marabelli; Giorgio Guizzetti

2003-01-01

33

Does a negative refractive index always result in negative refraction? - Effect of loss  

Microsoft Academic Search

The phenomenon of negative refraction has been demonstrated experimentally and by numerical simulation assuming Drude and Lorentz models for the permittivity and permeability. It has been assumed that a negative refractive index results in negative refraction and hence will lead to a variety of exciting applications for metamaterials. Loss cannot be avoided in real metamaterials and in this paper, we

Vasundara V. Varadan; Liming Ji

2009-01-01

34

Index of Refraction and SnellâÂÂs Law  

NSDL National Science Digital Library

In this video from the ICT Center, learn about the index of refraction and SnellâÂÂs law. Review a simple example of refraction, the speed of light in materials, and the formula for calculating the index of refraction. Explore a table of the refractive indices of common media and materials used in fiber optics and semiconductors. Finally, examine Snell's law to understand the relationship between incident and refracted angles.The video runs 4:04 and is accompanied by a background essay, standards alignment, and discussion questions. Users who sign up for a free account can save the resource and download the video as well.

2012-05-30

35

Fresnel or Refractive Index Ellipsoid - Interactive Java Tutorial  

NSDL National Science Digital Library

The refractive index, or the Fresnel, ellipsoid has a radius that yields the refractive index (n) or the squre root of the dielectric constant for waves whose electric displacement vectors lie in the direction of the radius of the ellipsoid within an anisotropic medium.

36

High temperature-gradient refractive index liquid crystals  

E-print Network

High temperature-gradient refractive index liquid crystals Jun Li, Sebastian Gauzia, and Shin of the ordinary refractive index ( dTdno / ) of liquid crystals. To achieve a large dTdno / , high birefringence exemplary liquid crystal mixtures, designated as UCF-1 and UCF-2, and compared their physical properties

Wu, Shin-Tson

37

String and Sticky Tape Experiments: Refractive Index of Liquids.  

ERIC Educational Resources Information Center

Describes a simple method of measuring the refractive index of a liquid using a paper cup, a liquid, a pencil, and a ruler. Uses the ratio between the actual depth and the apparent depth of the cup to calculate the refractive index. (GA)

Edge, R. D., Ed.

1979-01-01

38

Broadband, Volumetric Negative-Refractive-Index Scott M. Rudolph  

E-print Network

Broadband, Volumetric Negative-Refractive-Index Media by Scott M. Rudolph A dissertation submitted.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Motivation of Broadband, Low-Loss, Volumetric NRI Media 12 2.1 The Development of Broadband Negative-Refractive-Index Me

Sarabandi, Kamal

39

On the Refractive Index of Ageing Dispersions of Laponite  

E-print Network

Aqueous dispersion of Laponite at low ionic concentration is of interest since it undergoes structural evolution with respect to time, which is usually termed as ageing. In this work we study the refractive index behavior as a function of ageing time, concentration and temperature. We observed that the extended Lorenz-Lorentz equation fitted the refractive index dependence on concentration and temperature very well. The refractive index did not show any dependence on ageing time. However, the dependence of refractive index on concentration showed a marked change as the system underwent transition from an isotropic to a biphasic state. The slope of the refractive index-density data is remarkably close to that of water at all Laponite concentrations. In the context of transport phenomena, optical measurements such as interferometry can exploit the water-like behavior of Laponite dispersions.

N. V. N. Ravi Kumar; K. Muralidhar; Yogesh M. Joshi

2008-01-10

40

Refractive index matching using a diethyl phthalate/ ethanol solution  

NASA Astrophysics Data System (ADS)

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.

Miller, Paul; Slifka, Andy; Moody, Galan

2005-11-01

41

Determination of the refractive index of paper with clearing agents  

NASA Astrophysics Data System (ADS)

The refractive index of paper was determined by measuring the propagation delay of photons in optically cleared paper boards. The determination was based on the assumption that photon propagation delay achieves minimum value as the paper is optimally cleared. The measured paper sheets was made from elemental chlorine-free market pulp, i.e. fully bleached, unbeaten, softwood kraft pulp. Nine different clearing agents with a refraction index between 1.329 and 1.741 were eLuperimented with. According to the streakmem measurements, the refractive index of the test paper was 1.557.

Fabritius, Tapio; Saarela, Juha; Myllyla, Risto

2006-01-01

42

Refractive index profiling-state of the art  

Microsoft Academic Search

Problems associated with different calibration techniques and some instrumental effects that can determine instrumental accuracy are discussed. It is shown how transmission effects can be observed and used to generate a correction curve for refracted near-field instruments. High-quality fiber slices needed for axial interferometry were used to obtain refractive index differences on suitable fibers to ±1% with the measurements traceable

K. W. Raine; J. G. N. Baines; D. E. Putland

1989-01-01

43

Measurement of the effective refractive index of a turbid colloidal suspension using light refraction  

Microsoft Academic Search

We propose and analyse a simple method to measure simultaneously the real and imaginary parts of the effective refractive index of a turbid suspension of particles. The method is based on measurements of the angle of refraction and transmittance of a laser beam that traverses a hollow glass prism filled with a colloidal suspension. We provide a comprehensive assessment of

A. Reyes-Coronado; A. García-Valenzuela; C. Sánchez-Pérez; R. G. Barrera

2005-01-01

44

Refractive index modulation in photo-thermo-refractive fibers Eugeniu Rotari, Larissa Glebova, and Leonid Glebov  

E-print Network

atomic silver forms colloidal silver containing particle. Negative refractive index change is caused by absorption of the glass matrix, cerium ions, colloidal silver and scattering by crystalline phase photo-thermo-refractive (PTR) glass. PTR glass is a fluorosilicate glass doped with cerium and silver

Glebov, Leon

45

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

ERIC Educational Resources Information Center

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)

Krueger, David A.

1980-01-01

46

Miniature interferometer for refractive index measurement in microfluidic chip  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

47

Temperature dependence of the refractive index of optical fibers  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

48

Refractive index dispersion of lightguide glasses at high temperature  

Microsoft Academic Search

The refractive index of pure and GeO2-doped silica glasses was measured at wavelengths from 0.4 to 2.1 microns over a temperature range from 20 C to 540 C. Values for the thermal coefficient of the refractive index (about 0.000012\\/C at 1.3 microns) were almost identical for both glasses. The data showed that material dispersion for optical fibers increases with increasing

N. Shibata; S. Shibata; T. Edahiro

1981-01-01

49

Refractive index of air: 3. The roles of CO2, H2O, and refractivity virials.  

PubMed

The author's recent studies of the refractive index of air are extended, and several assumptions made therein are further examined. It is shown that the alternative dispersion equations for CO2, which are due to Edlen [Metrologia 2, 71 (1966)] and Old et al. [J. Opt. Soc. Am. 61, 89 (1971)] result in differences of less than 2 x 10(-9) in the phase refractive index and less than 3 x 10(-9) in the group refractive index for current and predicted concentrations of CO2. However, because the dispersion equation given by Old et al. is consistent with experimental data in the near infrared, it is preferable to the equation used by Edlen, which is valid only in the ultraviolet and the visible. The classical measurement by Barrell and Sears [Philos. Trans. R. Soc. London Ser. A 238, 1 (1939)] on the refractivity of moist air is shown to have some procedural errors in addition to the one discussed by Birch and Downs [Metrologia 30, 155 (1993)]. It is shown that for normal atmospheric conditions the higher refractivity virial coefficients related to the Lorentz-Lorenz relation are adequately incorporated into the empirically determined first refractivity virial. As a guide to users the practical limits to the calculation of the refractive index of the atmosphere that result from the uncertainties in the measurement of the various atmospheric parameters are summarized. PMID:12003222

Ciddor, Philip E

2002-04-20

50

Surface plasmon resonance optical cavity enhanced refractive index sensing.  

PubMed

We report on a method for surface plasmon resonance (SPR) refractive index sensing based on direct time-domain measurements. An optical resonator is built around an SPR sensor, and its photon lifetime is measured as a function of loss induced by refractive index variations. The method does not rely on any spectroscopic analysis or direct intensity measurement. Time-domain measurements are practically immune to light intensity fluctuations and thus lead to high resolution. A proof of concept experiment is carried out in which a sensor response to liquid samples of different refractive indices is measured. A refractive index resolution of the current system, extrapolated from the reproducibility of cavity-decay time determinations over 133 s, is found to be about 10(-5) RIU. The possibility of long-term averaging suggests that measurements with a resolution better than 10(-7) RIU/?Hz are within reach. PMID:23722800

Giorgini, A; Avino, S; Malara, P; Gagliardi, G; Casalino, M; Coppola, G; Iodice, M; Adam, P; Chadt, K; Homola, J; De Natale, P

2013-06-01

51

Refractive index sensor based on a polymer fiber directional coupler for low index sensing.  

PubMed

We propose, numerically analyze and experimentally demonstrate a novel refractive index sensor specialized for low index sensing. The device is based on a directional coupler architecture implemented in a single microstructured polymer optical fiber incorporating two waveguides within it: a single-mode core and a satellite waveguide consisting of a hollow high-index ring. This hollow channel is filled with fluid and the refractive index of the fluid is detected through changes to the wavelength at which resonant coupling occurs between the two waveguides. The sensor design was optimized for both higher sensitivity and lower detection limit, with simulations and experiments demonstrating a sensitivity exceeding 1.4 × 10(3) nm per refractive index unit. Simulations indicate a detection limit of ~2 × 10(-6) refractive index units is achievable. We also numerically investigate the performance for refractive index changes localized at the surface of the holes, a case of particular importance for biosensing. PMID:25090565

Lee, Kwang Jo; Liu, Xiaoqi; Vuillemin, Nelly; Lwin, Richard; Leon-Saval, Sergio G; Argyros, Alexander; Kuhlmey, Boris T

2014-07-14

52

Measurement of index of refraction of unknown solution using a microstructure fiber Bragg grating  

NASA Astrophysics Data System (ADS)

We demonstrate an application of fiber Bragg grating to measure the index of refraction of an unknown liquid by using a cladding depleted FBG. The measurements of the index of refraction were calibrated by the index oil with known index of refraction. Samples of liquid with difference percentage of sugar content were prepared and measured the index of refraction using this method. It shows that accuracy of index of refraction measurement as high as 0.01 can be achieved.

Kang, C. J.; Chen, Z. C.; Shih, M. C.

2013-06-01

53

Three-dimensional optical metamaterial with a negative refractive index  

Microsoft Academic Search

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

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

2008-01-01

54

Experimental demonstration of negative index of refraction Jiangfeng Zhou  

E-print Network

Experimental demonstration of negative index of refraction Jiangfeng Zhou Department of Electrical Structure and Laser--FORTH, and Department of Materials Science and Technology, University of Crete, Greece simpler approach in building negative-index materials. Using simulations and microwave experiments, we

55

Experimental demonstration of negative index of refraction Jiangfeng Zhou1  

E-print Network

Experimental demonstration of negative index of refraction Jiangfeng Zhou1 , Thomas Koschny2 Structure and Laser ­ FORTH, and Dept. of Materials Science and Technology, University of Crete, Greece metallic wires that offer a potentially simpler approach in building negative-index materials. Using

56

Comparison of negative refractive index materials with circular, elliptical and  

E-print Network

Comparison of negative refractive index materials with circular, elliptical and rectangular holes Zahyun Ku and S. R. J. Brueck Center for High Technology Materials and Department of Electrical: Negative-index metamaterials (NIMs) at near infrared wavelengths (~2 m) are fabricated with circular

New Mexico, University of

57

Measurement of pressure dependent nonlinear refractive index of inert gases.  

PubMed

The propagation of high intensity laser beams is excessively affected by optical nonlinear effects, thereby the knowledge of the nonlinear refractive indices of the beam guiding media is indispensable in the design of laser systems and experiments. Apart from undesired self-focusing, several areas of modern laser spectroscopy can utilize optical nonlinearity, from LiDAR measurements to filamentation. In this paper we report on a direct measurement of pressure dependent nonlinear refractive index of Ar, N2, Ne, Xe, and air between 0.05 mbar and 1 bar, based on the powerful technique called spectrally and spatially resolved interferometry. In this way the total value of nonlinear refractive index is measured, that is the sum of all elementary phenomena contributing to the intensity dependent refractivity of the gases. PMID:21164930

Börzsönyi, Á; Heiner, Z; Kovács, A P; Kalashnikov, M P; Osvay, K

2010-12-01

58

On the refractive index of sodium iodide solutions for index matching in PIV  

NASA Astrophysics Data System (ADS)

Refractive index matching has become a popular technique for facilitating applications of modern optical diagnostic techniques, such as particle image velocimetry, in complex systems. By matching the refractive index of solid boundaries with that of the liquid, unobstructed optical paths can be achieved for illumination and image acquisition. In this research note, we extend previously provided data for the refractive index of aqueous solutions of sodium iodide (NaI) for concentrations reaching the temperature-dependent solubility limit. Results are fitted onto a quadratic empirical expression relating the concentration to the refractive index. Temperature effects are also measured. The present range of indices, 1.333-1.51, covers that of typical transparent solids, from silicone elastomers to several recently introduced materials that could be manufactured using rapid prototyping. We also review briefly previous measurements of the refractive index, viscosity, and density of NaI solutions, as well as prior research that has utilized this fluid.

Bai, Kunlun; Katz, Joseph

2014-04-01

59

Isotropic spiral plasmonic metamaterial for sensing large refractive index change.  

PubMed

We numerically investigate the optical properties of a spiral G-shaped metamaterial, which exhibits both a sharp resonance with a high-quality factor and a broad resonance with a long linear slope in the near-infrared region. By employing the sharp resonating mode, refractive index sensing with sensitivity up to 410 nm/RIU is demonstrated theoretically. In addition, the metamaterial shows single wavelength sensing ability, which allows fast determination of environmental refractive index changes as large as 0.5 by simply monitoring variations in the transmitted intensity of a certain wavelength, which will be beneficial to the development of refractive index sensors based on monochromatic light sources and detectors. As the resonances are independent of the polarization direction of a linearly polarized wave, the sensor manufacturing process will benefit as a result of the lack of an alignment requirement for the axis of polarizers with the metamaterials' orientation. PMID:24104668

Ren, Mengxin; Pan, Chongpei; Li, Qunqing; Cai, Wei; Zhang, Xinzheng; Wu, Qiang; Fan, Shoushan; Xu, Jingjun

2013-08-15

60

Terahertz refractive index sensors using dielectric pipe waveguides.  

PubMed

A dielectric pipe waveguide is successfully demonstrated as a terahertz refractive index sensor for powder and liquid-vapor sensing. Without additional engineered structures, a simple pipe waveguide can act as a terahertz resonator based on anti-resonant reflecting guidance, forming multiple resonant transmission-dips. Loading various powders in the ring-cladding or inserting different vapors into the hollow core of the pipe waveguide leads to a significant shift of resonant frequency, and the spectral shift is related to the refractive-index change. The proven detection limit of molecular density could be reduced to 1.6nano-mole/mm3 and the highest sensitivity is demonstrated at around 22.2GHz/refractive-index-unit (RIU), which is comparable to the best THz molecular sensor [Appl. Phys. Lett. 95, 171113 (2009)]. PMID:22418463

You, Borwen; Lu, Ja-Yu; Yu, Chin-Ping; Liu, Tze-An; Peng, Jin-Long

2012-03-12

61

Refractive index change and curvature in shock waves by angled beam refraction  

NASA Astrophysics Data System (ADS)

Observations of front geometry and refractive index jump across shock waves in rare gases have been made with a new particularly simple technique. The technique involves determination of the angular deflection of a narrow laser beam intersecting the shock front at a shallow angle. Measured refractive index jumps in rare gases are in excellent agreement with those calculated using Snell's law and ideal shock theory. The apparent shock curvature is in close accord with deBoer's theory for loading pressures below 20 Torr, but above this pressure there is evidence of an indentation near tube center.

Kiefer, J. H.; Manson, A. C.

1981-09-01

62

Measuring the refractive index with precision goniometers: a comparative study  

NASA Astrophysics Data System (ADS)

The accurate knowledge about the refractive index of optical materials is crucial for the production of high performance optical components. It is known that the highest accuracy of refractive index measurements can be achieved with goniometric measurements of prisms prepared from the optical material. The most common approach is the method of minimum deviation of Newton-Fraunhofer. The apex angle is measured with a high precision in reflection with an autocollimator and the angle of refraction is measured in transmission using an additional collimator. There are also other goniometric approaches like the Abbé method employing a purely reflective setup with an autocollimator. In this paper we discuss and compare the two different goniometric approaches.

Krey, Stefan; Off, Dennis; Ruprecht, Aiko

2014-03-01

63

REFRACTIVE INDEX ENHANCEMENT AND ATOMIC STATE LOCALIZATION IN RUBIDIUM  

E-print Network

REFRACTIVE INDEX ENHANCEMENT AND ATOMIC STATE LOCALIZATION IN RUBIDIUM BY NICHOLAS A. PROITE teacher and scientist to work with throughout my graduate career and his research skill is remarkable both in and out of the lab. His amazing ability to break down even the most difficult problems into simple

Yavuz, Deniz

64

Index of refraction of various gases for sodium matter waves  

Microsoft Academic Search

By inserting a gas cell in one arm of an atom interferometer, we have measured both the attenuation and the phase shift of a sodium matter wave that passes through monatomic (He, Ne, Ar, Kr, and Xe) or molecular gases (Nâ, COâ, NHâ, and HâO). This determines the complex index of refraction for Na matter waves and, more accurately, the

Jörg Schmiedmayer; Michael Chapman; Christopher Ekstrom; Troy Hammond; Stefan Wehinger; David Pritchard

1995-01-01

65

Experimental Verification of a Negative Index of Refraction  

Microsoft Academic Search

We present experimental scattering data at microwave frequencies on a structured metamaterial that exhibits a frequency band where the effective index of refraction (n) is negative. The material consists of a two-dimensional array of repeated unit cells of copper strips and split ring resonators on interlocking strips of standard circuit board material. By measuring the scattering angle of the transmitted

R. A. Shelby; D. R. Smith; S. Schultz

2001-01-01

66

Radio refractive index investigations over Bass Strait, Southern Australia  

Microsoft Academic Search

Radio refractive index profile measurements between 500 and 5000 feet were made over Bass Strait (Australia) during January and March 1966, using a microwave refractometer car-tied in a light aircraft. During these flights continuous radio propagation measurements at 173 MHz and 1.9 GHz were made over paths at points along which the profiles were measured. Supporting meteorological observations were also

G. Jenkinson; M. Van Dijk

1969-01-01

67

Magnetic Response and Negative Refractive Index of metamaterials  

E-print Network

Magnetic Response and Negative Refractive Index of metamaterials Th. Koschnya,b, J. Zhoua, and C Heraklion, Crete, Greece. c Dept. of Materials Science and Technology, University of Crete, Heraklion, Crete, Greece. ABSTRACT We study the scaling of negative magnetic response of the SRR from microwave to upper

68

Measurement of transient nonlinear refractive index in gases using xenon  

E-print Network

Measurement of transient nonlinear refractive index in gases using xenon supercontinuum single measurement of ultrafast high field processes using modest energy lasers, with pump and probe pulses totaling) and instrument resolution. The ultrafast nonlinear Kerr effect in glass, and in Ar, N2, and N2O gases is measured

Milchberg, Howard

69

A particle mechanism for the index of refraction Marcel URBAN  

E-print Network

for the slowing down of the photons. The idea is to push the particle model of light as far as possible without using wave's properties. We describe our model of the interaction between a photon and a moleculeLAL 07-79 July 2007 A particle mechanism for the index of refraction Marcel URBAN LAL, Univ Paris

Paris-Sud XI, Université de

70

Amplification without inversion and high refractive index in heterogeneous molecules  

NASA Astrophysics Data System (ADS)

The system of interest is a closed three-level V-type system with two excited near degenerated levels in a weak probe field and a strong coupling field, in the presence of an incoherent pumping field. We investigate analytically the conditions to have amplification without population inversion or high index of refraction without absorption due to spontaneously generated coherence and incoherent pumping. The perturbation solution of the density matrix equation in the steady state case is derived. We find that the refractive index and absorption coefficient have a periodic dependence on the relative phase of the probe and coupling fields. The relative phase values for which the system exhibits a high refractive index without absorption are obtained. The conditions on incoherent pumping rate related to that for the angle between the two transition dipole moments and spontaneous emission rates of the two excited states to obtain the probe field gain without population inversion are derived. We propose a three-level V-type system with spontaneously generated coherence from LiH molecule which can achieve quasi-high index of refraction without absorption and amplification without population inversion.

Budriga, O.

2014-10-01

71

Optical glass: refractive index change with wavelength and temperature  

NASA Astrophysics Data System (ADS)

With the catalog of 1992 SCHOTT introduced two formulae each with six parameters for a better representation of the refractive index of optical glasses. The Sellmeier-equation improved the characterization of dispersion at room temperature and the Hoffmann equation that of its temperature dependence. Better representation had been expected because both formulae were derived from general dispersion theory. The original publication of Hoffmann et al. from 1992 contains first results on the accuracy of the fits. The extended use of the formulae has led to a collection of data allowing reviewing the adequacy of the Sellmeier-equation approach on a much broader basis. We compare fitted refractive index values with measured values for all wavelengths used at our precision refractive index goniometer. Data sets are available for specific melts of the four representative glass types N-BK7, N-FK5, LF5 and IRG2. For some materials, the optical glass N-LAF21, the IR glass IRG2 and the crystal CaF2, several sets of data for the temperature dependence of the refractive index are available thus giving evidence for the variation of these properties among melts of the same material.

Englert, Marion; Hartmann, Peter; Reichel, Steffen

2014-05-01

72

Structures with negative index of refraction  

DOEpatents

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.

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

2011-11-08

73

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

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

74

Refractive index and birefringence of 2H silicon carbide  

NASA Technical Reports Server (NTRS)

The refractive indices of 2H SiC were measured over the wavelength range 435.8 to 650.9 nm by the method of minimum deviation. At the wavelength lambda = 546.1 nm, the ordinary index n sub 0 was 2.6480 and the extraordinary index n sub e was 2.7237. The estimated error (standard deviation) in the measured values is 0.0006 for n sub 0 and 0.0009 for n sub e. The experimental data were curve fitted to the Cauchy equation for the index of refraction as a function of wavelength. The birefringence of 2H SiC was found to vary from 0.0719 at lambda = 650.9 nm to 0.0846 at lambda = 435.8 nm.

Powell, J. A.

1972-01-01

75

Analysis of non-linear refractive index influences on four-wave mixing conversion efficiency in semiconductor optical amplifiers  

NASA Astrophysics Data System (ADS)

In this paper, we have analyzed the influences of non-linear refractive index on the four-wave mixing (FWM) characteristics in semiconductor optical amplifiers (SOAs). It has been shown that the generated FWM signal characteristics can be modified due to the variation of non-linear refractive index of the SOA's medium. The wave propagation in the SOA has been modeled using the nonlinear propagation equation taking into account gain spectrum dynamics, gain saturation, which depends on carrier depletion, carrier heating, spectral hole-burning, group velocity dispersion, self-phase modulation and two photon absorption. Simulation of optical wave evolution in the SOA has been carried out using the finite-difference beam propagation method (FD-BPM) both in time and spectral domains. Our simulation results confirm that higher FWM conversion efficiency and lower time bandwidth product are achieved for higher absolute values of non-linear refractive index. Moreover, non-linear refractive index is more efficacious for high power propagated waves in SOAs. Finally, we have studied the modification of waveguide refractive index due to the propagation of optical pulses. We have also shown that when | n2|=1 cm 2/TW, refractive index variation is in the order of 10 -4 to 10 -7 for high and low power input pulses, respectively.

Hosseini, S. R.; Razaghi, M.; Das, N. K.

2012-04-01

76

INDEX OF REFRACTION OF SHOCK LOADED SODA-LIME GLASS  

SciTech Connect

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.

Alexander, C. S. [Sandia National Laboratories, Albuquerque NM 87185 (United States)

2009-12-28

77

Index of Refraction of Shock Loaded Soda-Lime Glass  

NASA Astrophysics Data System (ADS)

Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to approximately 25 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. App. Physics, 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.

Alexander, Scott

2009-06-01

78

Transition of refractive index contrast in course of grating growth  

PubMed Central

Studies on the dynamics of holographic pattern formation in photosensitive polymers, gaining deeper insight into the specific material transformations, are essential for improvements in holographic recording as well as in integrated optics. Here we investigate the kinetics of volume hologram formation in an organic cationic ring-opening polymerization system. The time evolution of the grating strength and the grating phase is presented. We found two steps of growth, separated by a depletion of the light diffraction. Capable to explore this growing behavior, a transition-theory of the refractive index contrast is established. Accordingly the growth curves appear to be ruled by the interplay of polymerization and diffusion. Hence the grating formation mechanisms can be qualified as competing effects regarding the contribution to the refractive index change. We investigate the influence of the preparation and exposure procedure on the transition and consider the usability for integrated wave guide functions. PMID:23989752

Sabel, Tina; Zschocher, Michael

2013-01-01

79

Refractive Index Compensation in Over-Determined Interferometric Systems  

PubMed Central

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

Lazar, Josef; Hola, Miroslava; Cip, Ondrej; Cizek, Martin; Hrabina, Jan; Buchta, Zdenek

2012-01-01

80

Refractive index compensation in over-determined interferometric systems.  

PubMed

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

Lazar, Josef; Holá, Miroslava; ?íp, Ond?ej; ?ížek, Martin; Hrabina, Jan; Buchta, Zden?k

2012-01-01

81

The whistler mode refractive index as a function of gyrofrequency  

SciTech Connect

The refractive index for a constant-frequency whistler mode wave in an electron-proton plasma is considered as a function of position, through the local gyrofrequencies {Omega}{sub e,i}. The full cold plasma dispersion relation is used. The wave frequency can take any value up to the smaller of {Omega}{sub e} and the plasma frequency {omega}{sub pe}, but {omega}{sub pe} is allowed to take any fixed value, as is the wavenormal angle. It is rigorously established that the refractive index is a decreasing function of {Omega}{sub e}. One application of this is to finding locations of Landau and cyclotron resonances, to evaluate the effects of whistler mode waves on radiation belt electrons.

Albert, J. M. [Air Force Research Laboratory/RVBX, Kirtland AFB, New Mexico 87117 (United States)

2011-08-15

82

Ultrafast refractive index control of a terahertz graphene metamaterial  

PubMed Central

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

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

2013-01-01

83

Fiber Optic-Based Refractive Index Sensing at INESC Porto  

PubMed Central

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

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

2012-01-01

84

Measurement of the Kerr nonlinear refractive index of Cs vapor  

E-print Network

Atomic vapors are systems well suited for nonlinear optics studies but very few direct measurements of their nonlinear refractive index have been reported. Here we use the z-scan technique to measure the Kerr coefficient, $n_2$, for a Cs vapor. Our results are analyzed through a four-level model, and we show that coherence between excited levels as well as cross-population effects contribute to the Kerr-nonlinearity.

Araújo, Michelle O; Oriá, Marcos; Chevrollier, Martine; de Silans, Thierry Passerat; Castro, Romeu; Moretti, Danieverton

2014-01-01

85

X-ray refractive index of laser-dressed atoms  

Microsoft Academic Search

We investigated the complex index of refraction in the x-ray regime of atoms in laser light. The laser (intensity up to 1013W\\/cm2 , wavelength 800nm ) modifies the atomic states but, by assumption, does not excite or ionize the atoms in their electronic ground state. Using quantum electrodynamics, we devise an ab initio theory to calculate the dynamic dipole polarizability

Christian Buth; Robin Santra

2008-01-01

86

Temperature Coefficients of the Refractive Index for Complex Hydrocarbon Mixtures  

NASA Astrophysics Data System (ADS)

Temperature coefficients of the refractive index () in the to temperature interval for hydrocarbon mixtures containing as many as 14 compounds were investigated in this work. The measured of the mixtures were compared with calculations based on the values for each compound and their concentrations. Differences of about 1 % between measured and calculated values were observed for all mixtures. The additivity of for these hydrocarbons enables preparation of surrogate fuels that are formulated to have properties like those of specific diesel fuels.

Wen, Qing; Shen, Jun; Gieleciak, Rafal; Michaelian, Kirk H.; Rohling, Jurandir H.; Astrath, Nelson G. C.; Baesso, Mauro L.

2014-05-01

87

Photonic crystals and microlasers fabricated with low refractive index material  

Microsoft Academic Search

Although the investigation on photonic band gap materials has been done more than two decades, it is still a big challenge\\u000a to fabricate three-dimensional photonic crystal (PC) possessing wide band gaps in visible range. In this article, we have\\u000a reviewed recent progresses on fabricating the PC with low refractive index material in visible range. In contrast to the material\\u000a with

Tian-Rui Zhai; Da-He Liu; Xiang-Dong Zhang

2010-01-01

88

A simple optical probing technique for nonlinearly induced refractive index  

NASA Astrophysics Data System (ADS)

Self phase modulation is a nonlinear effect that is observed when a laser beam is focused on to a high-absorbing thermal medium. A regular tea sample in a plastic cuvette is used as the nonlinear absorbing sample. The change in the refractive index of the medium occurs due to the heat generated by the focused pump beam, which in turn changes the refractive index. In this paper, self phase modulation is investigated in different ways. An Ar-Ion laser of 514 nm is used as the pump beam and a 632 nm He-Ne laser is used as the probe beam. The probe beam is introduced from the opposite side of the pump beam. Ring patterns are observed from the each side of the sample. Regular far field ring patterns are observed from the pump beam, and two sets of rings are observed with the probe beam. The behaviors of these inner and outer rings are monitored for different pump powers. The steady state heat equation is solved to obtain an exact solution for the radial heat distribution and far field ring patterns are simulated using the Fresnel-Kirchhoff diffraction integral. Ring patterns are theoretically explained using simulations results, and compared with experimental observations. Finally, an interferometric setup using the low power He-Ne laser is also used to determine the induced change in refractive index. Results are compared with those obtained directly from self-phase modulation and from the probe beam method.

Banerjee, Partha; Abeywickrema, Ujitha

2013-09-01

89

Laser optical gas sensor by photoexcitation effect on refractive index.  

PubMed

Laser optical gas sensors are fabricated by using the crystalline silicon carbide polytype 6H-SiC, which is a wide-bandgap semiconductor, and tested at high temperatures up to 650 degrees C. The sensor operates on the principle of semiconductor optics involving both the semiconductor and optical properties of the material. It is fabricated by doping 6H-SiC with an appropriate dopant such that the dopant energy level matches the quantum of energy of the characteristic radiation emitted by the combustion gas of interest. This radiation changes the electron density in the semiconductor by photoexcitation and, thereby, alters the refractive index of the sensor. The variation in the refractive index can be determined from an interference pattern. Such patterns are obtained for the reflected power of a He-Ne laser of wavelength 632.8 nm as a function of temperature. SiC sensors have been fabricated by doping two quadrants of a 6H-SiC chip with Ga and Al of dopant energy levels E(V)+0.29 eV and E(V)+0.23 eV, respectively. These doped regions exhibit distinct changes in the refractive index of SiC in the presence of carbon dioxide (CO(2)) and nitrogen monoxide (NO) gases respectively. Therefore Ga- and Al-doped 6H-SiC can be used for sensing CO(2) and NO gases at high temperatures, respectively. PMID:20300151

Lim, Geunsik; DeSilva, Upul P; Quick, Nathaniel R; Kar, Aravinda

2010-03-20

90

Origami with negative refractive index to generate super-lenses.  

PubMed

Negative refractive index materials (NRIM) enable unique effects including superlenses with a high degree of sub-wavelength image resolution, a capability that stems from the ability of NRIM to support a host of surface plasmon states. Using a generalized lens theorem and the powerful tools of transformational optics, a variety of focusing configurations involving complementary positive and negative refractive index media can be generated. A paradigm of such complementary media are checkerboards that consist of alternating cells of positive and negative refractive index, and are associated with very singular electromagnetics. We present here a variety of multi-scale checkerboard lenses that we call origami lenses and investigate their electromagnetic properties both theoretically and computationally. Some of these meta-structures in the plane display thin bridges of complementary media, and this highly enhances their plasmonic response. We demonstrate the design of three-dimensional checkerboard meta-structures of complementary media using transformational optics to map the checkerboard onto three-dimensional corner lenses, the only restriction being that the corresponding unfolded structures in the plane are constrained by the four color-map theorem. PMID:25224380

Guenneau, Fanny; Chakrabarti, Sangeeta; Guenneau, Sebastien; Ramakrishna, S Anantha

2014-10-01

91

Organic Plasmon-Emitting Diodes for Detecting Refractive Index Variation  

PubMed Central

A photo-excited organic layer on a metal thin film with a corrugated substrate was used to generate surface plasmon grating coupled emissions (SPGCEs). Directional emissions corresponded to the resonant condition of surface plasmon modes on the Au/air interface. In experimental comparisons of the effects of different pitch sizes on the plasmonic band-gap, the obtained SPGCEs were highly directional, with intensity increases as large as 10.38-fold. The FWHM emission spectrum was less than 70 nm. This method is easily applicable to detecting refractive index changes by using SP-coupled fluorophores in which wavelength emissions vary by viewing angle. The measurements and calculations in this study confirmed that the color wavelength of the SPGCE changed from 545.3 nm to 615.4 nm at certain viewing angles, while the concentration of contacting glucose increased from 10 to 40 wt%, which corresponded to a refractive index increase from 1.3484 to 1.3968. The organic plasmon-emitting diode exhibits a wider linearity range and a resolution of the experimental is 1.056 × 10?3 RIU. The sensitivity of the detection limit for naked eye of the experimental is 0.6 wt%. At a certain viewing angle, a large spectral shift is clearly distinguishable by the naked eye unaided by optoelectronic devices. These experimental results confirm the potential applications of the organic plasmon-emitting diodes in a low-cost, integrated, and disposable refractive-index sensor. PMID:23812346

Chiu, Nan-Fu; Cheng, Chih-Jen; Huang, Teng-Yi

2013-01-01

92

Origami with negative refractive index to generate super-lenses  

NASA Astrophysics Data System (ADS)

Negative refractive index materials (NRIM) enable unique effects including superlenses with a high degree of sub-wavelength image resolution, a capability that stems from the ability of NRIM to support a host of surface plasmon states. Using a generalized lens theorem and the powerful tools of transformational optics, a variety of focusing configurations involving complementary positive and negative refractive index media can be generated. A paradigm of such complementary media are checkerboards that consist of alternating cells of positive and negative refractive index, and are associated with very singular electromagnetics. We present here a variety of multi-scale checkerboard lenses that we call origami lenses and investigate their electromagnetic properties both theoretically and computationally. Some of these meta-structures in the plane display thin bridges of complementary media, and this highly enhances their plasmonic response. We demonstrate the design of three-dimensional checkerboard meta-structures of complementary media using transformational optics to map the checkerboard onto three-dimensional corner lenses, the only restriction being that the corresponding unfolded structures in the plane are constrained by the four color-map theorem.

Guenneau, Fanny; Chakrabarti, Sangeeta; Guenneau, Sebastien; Ramakrishna, S. Anantha

2014-10-01

93

Side polished fiber Bragg grating sensor for simultaneous measurement of refractive index and temperature  

Microsoft Academic Search

A fiber sensor to achieve simultaneous measurement of refractive index and temperature is proposed by using a side polished fiber Bragg grating. The reflective wavelength of side polished fiber Bragg grating shifts with the ambient refractive index and local temperature. By overlaying half of the polished surface of fiber Bragg grating with liquid material, simultaneous discrimination of liquid refractive index

Zhe Chen; Jieyuan Tang; Ruoyan Fan; Yongchun Zhong; Jun Zhang; Siben Li

2011-01-01

94

High Frequency Limit of the Helmholtz Equation with Variable Refraction Index  

E-print Network

.1) determines the field of a light source in an inhomogeneous medium with refraction index n(x), wave lengthHigh Frequency Limit of the Helmholtz Equation with Variable Refraction Index Xue Ping WANG of the Helmholtz equation with variable refraction index and a source term concentrated near a p­dimensional a

Wang, Xue Ping

95

Influence of the refractive index-mismatch at the boundaries measured in fluorescence-  

E-print Network

Influence of the refractive index-mismatch at the boundaries measured in fluorescence- enhanced. The refractive-index mismatch parameter in the boundary condition of the light propagation model, namely. In this contribution, the influence of refractive-index mismatch parameter between predictions and referenced

Eppstein, Margaret J.

96

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

97

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

PubMed

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

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

2011-03-01

98

Extraction of complex refractive index dispersion from SPR data  

NASA Astrophysics Data System (ADS)

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.

Nakkach, Mohamed; Moreau, Julien; Canva, Michael

2010-02-01

99

Cosmology With A Dark Refraction Index B. Chen 1 , and R. Kantowski 1, y  

E-print Network

caused by an e#11;ective index of refraction, and hence this theory could extend to other speed of light electrodynamics light is altered in both speed and direction (light refraction). The impact of light refraction. An interesting and useful theoretical tool to study light refraction in curved spacetime is Gordon's optical

Kantowski, Ron

100

Multimode interference refractive index sensor based on coreless fiber  

NASA Astrophysics Data System (ADS)

A multimode interference refractive index (RI) sensor based on the coreless fiber was numerically and experimentally demonstrated. Two identical single mode fibers (SMF) are spliced at both ends of a section of the coreless fiber which can be considered as the equivalent weakly guiding multimode fiber (MMF) with a step-index profile when the surrounding refractive index (SRI) is lower than that of the coreless fiber. Thus, it becomes the conventional single-mode multimode single-mode (SMS) fiber structure but with a larger core size. The output spectra will shift along with the changes in the SRI owing to the direct exposure of the coreless fiber. The output spectra under different SRIs were numerically studied, as well as the sensitivities with different lengths and diameters of the coreless fiber. The predication and calculation showed the good agreement with the experimental results. The proposed RI sensor proved to be feasible by verification experiments, and the relative error was merely 0.1% which occupied preferable sensing performance and practicability.

Li, Yang; Liu, Zhibo; Jian, Shuisheng

2014-03-01

101

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

PubMed Central

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.

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

2012-01-01

102

Spacetime geometries and light trapping in travelling refractive index perturbations  

E-print Network

In the framework of transformation optics, we show that the propagation of a locally superluminal refractive index perturbation (RIP) in a Kerr medium can be described, in the eikonal approximation, by means of a stationary metric, which we prove to be of Gordon type. Under suitable hypotheses on the RIP, we obtain a stationary but not static metric, which is characterized by an ergosphere and by a peculiar behaviour of the geodesics, which are studied numerically, also accounting for material dispersion. Finally, the equation to be satisfied by an event horizon is also displayed and briefly discussed.

F. Belgiorno; S. L. Cacciatori; V. Gorini; G. Ortenzi; L. Rizzi; V. G. Sala; D. Faccio

2010-06-06

103

Loop SBS oscillator on a stationary nonlinear refractive index grating  

SciTech Connect

A loop SBS oscillator is studied, in which pump radiation coupled out from a nonlinear medium is directed backward to the medium. To increase the interaction length, a light guide is used. The feedback is obtained on a stationary nonlinear refractive index grating produced by the pump waves. The signal generated at the Stokes frequency in the loop propagates in the direction opposite to the pump and is amplified due to the classical backward SBS. Such an oscillator can be treated as a distributed feedback oscillator produced by the pump waves themselves. (nonlinear optical phenomena)

Bel'dyugin, Igor' M ['Astrofizika' Research and Production Association (Russian Federation); Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I; Sobolev, V B [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2009-12-31

104

Seismic refraction methodology for groundwater level determination: “Water seismic index”  

NASA Astrophysics Data System (ADS)

Recently, there has been increased interest in the use of refraction seismic data for the exploration and development of hydrological reservoirs. The aim of this study is to provide a procedure in order to identify groundwater levels by means of seismic refraction profiles. Assuming that the velocity of shear waves increases much less than the velocity of compressional waves in a saturated soil, seismic refraction surveys were performed for the determination of the water table. In order to have a perfect overlay of the tomography 2D grids, P and S wave seismic profiles were obtained with the same geometrical configuration. Based on the propagation of the P and S waves in the unsaturated and saturated media, a "Water Seismic Index" (WSI) was defined. WSI is related to the local variations of the P and S wave velocities and, in theoretical terms, it is correlated to groundwater level. Preliminary results indicate that there is a good agreement between the depth of the ground water and the WSI parameter.

Grelle, Gerardo; Guadagno, Francesco Maria

2009-07-01

105

Online Submission ID: latebreaking 0055 Refractive Index Dependent Bidirectional Scattering Distribution Functions  

E-print Network

Online Submission ID: latebreaking 0055 Refractive Index Dependent Bidirectional Scattering Distribution Functions Figure 1: We investigate on the reflectance of materials immersed into media of different refractive indices. We therefore use a capturing setup (left image), to place patches

Magnor, Marcus

106

Refractive index of erbium doped GaN thin films  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

107

Dark matter constraints from a cosmic index of refraction  

SciTech Connect

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.

Gardner, Susan [Center for Particle Astrophysics and Theoretical Physics Department, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States); Latimer, David C. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)

2010-09-15

108

Refractive index sensing using fluorescence lifetime imaging (FLIM)  

NASA Astrophysics Data System (ADS)

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.

Tregidgo, Carolyn; Suhling, Klaus

2007-02-01

109

Dark Matter Constraints from a Cosmic Index of Refraction  

SciTech Connect

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.

Gardner, Susan; Latimer, David C.

2009-04-01

110

X-ray refractive index of laser-dressed atoms  

E-print Network

We investigated the complex index of refraction in the x-ray regime of atoms in laser light. The laser (intensity up to 10^13 W/cm^2, 800nm) modifies the atomic states but, by assumption, does not excite or ionize the atoms in their electronic ground state. Using quantum electrodynamics, we devise an ab initio theory to calculate the dynamic dipole polarizability and the photoabsorption cross section, which are subsequently used to determine the real and imaginary part, respectively, of the refractive index. The interaction with the laser is treated nonperturbatively; the x-ray interaction is described in terms of a one-photon process. We numerically solve the resolvents involved using a single-vector Lanczos algorithm. Finally, we formulate rate equations to copropagate a laser and an x-ray pulse through a gas cell. Our theory is applied to argon. We study the x-ray polarizability and absorption near the argon K edge over a large range of dressing-laser intensities. We find electromagnetically induced transp...

Buth, Christian

2008-01-01

111

Dark Matter Constraints from a Cosmic Index of Refraction  

E-print Network

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 |varepsilon|/M < 1 x 10^{-5} eV^{-1} at 95% CL.

S. Gardner; D. C. Latimer

2009-04-10

112

A refractive index sensor based on the leaky radiation of a microfiber  

E-print Network

In this work we present a refractive index sensor based on the leaky radiation of a microfiber. The 5.3um diameter microfiber is fabricated by drawing a commercial optical fiber. When the microfiber is immersed into a liquid with larger refractive index than the effective index of fiber mode, the light will leak out through the leaky radiation process. The variation of refractive index of liquid can be monitored by measuring radiation angle of light. The refractive index sensitivity can be over 400 degree/RIU in theory. In the experiment, the variation value 0.001 of refractive index of liquid around this microfiber can be detected through this technique. This work provides a simple and sensitive method for refractive index sensing application.

Gao, F; Sheng, C; Zhu, C; Zhu, S N

2014-01-01

113

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

SciTech Connect

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.

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

2011-07-01

114

Optical glass with tightest refractive index and dispersion tolerances for high-end optical designs  

NASA Astrophysics Data System (ADS)

In high end optical designs the quality of the optical system not only depends on the chosen optical glasses but also on the available refractive index and Abbe number tolerances. The primary optical design is based on datasheet values of the refractive index and Abbe number. In general the optical position of the delivered glass will deviate from the catalog values by given tolerances due to production tolerances. Therefore in many cases the final optical design needs to be modified based on real glass data. Tighter refractive index and Abbe number tolerances can greatly reduce this additional amount of work. The refractive index and Abbe number of an optical glass is a function of the chemical composition and the annealing process. Tight refractive index tolerances require not only a close control and high reliability of the melting and fine annealing process but also best possible material data. These data rely on high accuracy measurement and accurate control during mass production. Modern melting and annealing procedure do not only enable tight index tolerances but also a high homogeneity of the optical properties. Recently SCHOTT was able to introduce the tightest available refractive index and Abbe number tolerance available in the market: step 0.5 meaning a refractive index tolerance of +/- 0.0001 and an Abbe number tolerance of +/- 0.1%. This presentation describes how the refractive index depends on the glass composition and annealing process and describes the requirements to get to this tightest refractive index and Abbe number tolerance.

Jedamzik, R.; Reichel, S.; Hartmann, P.

2014-03-01

115

Measurement of nonlinear refractive index by time-resolved z-scan technique  

Microsoft Academic Search

A time-resolved z-scan technique using 100 fs laser pulses for measurement of nonlinear refractive indexes is reported. This technique allows us to measure the relaxation times of the nonlinear refractive indexes. Both the magnitude and the relaxation of nonlinear refractive indexes in CS2 and head-to-tail poly(3-alkylthiophene) were measured. We found that there are two decay components. The slow and the

Tadashi Kawazoe; Hitoshi Kawaguchi; Jun Inoue; Osamu Haba; Mitsuru Ueda

1999-01-01

116

Experimental Verification and Simulation of Negative Index of Refraction Using Snell's Law  

Microsoft Academic Search

We report the results of a Snell's law experiment on a negative index of refraction material in free space from 12.6 to 13.2GHz. Numerical simulations using Maxwell's equations solvers show good agreement with the experimental results, confirming the existence of negative index of refraction materials. The index of refraction is a function of frequency. At 12.6GHz we measure and compute

C. G. Parazzoli; R. B. Greegor; K. Li; B. E. Koltenbah; M. Tanielian

2003-01-01

117

Dependence of the Radiation Pressure on the Background Refractive Index  

NASA Astrophysics Data System (ADS)

The 1978 experiments by Jones and Leslie showing that the radiation pressure on a mirror depends on the background medium refractive index have yet to be adequately explained using a force model and have provided a leading challenge to the Abraham form of the electromagnetic momentum. Those experimental results are predicted for the first time using a force representation that incorporates the Abraham momentum by utilizing the power calibration method employed in the Jones and Leslie experiments. With an extension of the same procedure, the polarization and angle independence of the experimental data are also explained by this model. Prospects are good for this general form of the electromagnetic force density to be effective in predicting other experiments with macroscopic materials. Furthermore, the rigorous representation of material dispersion makes the representation important for metamaterials that operate in the vicinity of homogenized material resonances.

Webb, Kevin J.

2013-07-01

118

Imaging Cells and Tissues with Refractive Index Radiology  

PubMed Central

Can individual cells, including live cells, be imaged using hard x rays? Common wisdom until now required sophisticated staining techniques for this task. We show instead that individual cells and cell details can be detected in culture solution and tissues with no staining and no other contrast-enhancing preparation. The sample examined can be much thicker than for many other microscopy techniques without sacrificing the capability to resolve cells. The key factor in our approach is the use of a coherent synchrotron source and of contrast mechanisms based on the refractive index. The first successful tests were conducted on a variety of cell systems including skin and internal leaf cells, mouse neurons, rabbit fibroblast cells, and human tumor cells. PMID:15465870

Hwu, Y.; Tsai, W. L.; Chang, H. M.; Yeh, H. I.; Hsu, P. C.; Yang, Y. C.; Su, Y. T.; Tsai, H. L.; Chow, G. M.; Ho, P. C.; Li, S. C.; Moser, H. O.; Yang, P.; Seol, S. K.; Kim, C. C.; Je, J. H.; Stefanekova, E.; Groso, A.; Margaritondo, G.

2004-01-01

119

Semiconductor laser devices having lateral refractive index tailoring  

DOEpatents

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.

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

1990-01-01

120

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

121

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

DOEpatents

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.

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

2002-01-01

122

Measurement of the refractive index of human teeth by optical coherence tomography  

NASA Astrophysics Data System (ADS)

We describe a novel method based on optical coherence tomography (OCT) for the accurate measurement of the refractive index of in vitro human teeth. We obtain the refractive indices of enamel, dentin, and cementum to be 1.631+/-0.007, 1.540+/-0.013, and 1.582+/-0.010, respectively. The profile of the refractive index is readily obtained via an OCT B scan across a tooth. This method can be used to study the refractive index changes caused by dental decay and therefore has great potential for the clinical diagnosis of early dental caries.

Meng, Zhuo; Yao, X. Steve; Yao, Hui; Liang, Yan; Liu, Tiegen; Li, Yanni; Wang, Guanhua; Lan, Shoufeng

2009-05-01

123

An absolute index (Ab-index) to measure a researcher's useful contributions and productivity.  

PubMed

Bibliographic analysis has been a very powerful tool in evaluating the effective contributions of a researcher and determining his/her future research potential. The lack of an absolute quantification of the author's scientific contributions by the existing measurement system hampers the decision-making process. In this paper, a new metric system, Absolute index (Ab-index), has been proposed that allows a more objective comparison of the contributions of a researcher. The Ab-index takes into account the impact of research findings while keeping in mind the physical and intellectual contributions of the author(s) in accomplishing the task. The Ab-index and h-index were calculated for 10 highly cited geneticists and molecular biologist and 10 young researchers of biological sciences and compared for their relationship to the researchers input as a primary author. This is the first report of a measuring method clarifying the contributions of the first author, corresponding author, and other co-authors and the sharing of credit in a logical ratio. A java application has been developed for the easy calculation of the Ab-index. It can be used as a yardstick for comparing the credibility of different scientists competing for the same resources while the Productivity index (Pr-index), which is the rate of change in the Ab-index per year, can be used for comparing scientists of different age groups. The Ab-index has clear advantage over other popular metric systems in comparing scientific credibility of young scientists. The sum of the Ab-indices earned by individual researchers of an institute per year can be referred to as Pr-index of the institute. PMID:24391941

Biswal, Akshaya Kumar

2013-01-01

124

Sensors and Actuators B 123 (2007) 594605 Fiber optic sensing of liquid refractive index  

E-print Network

using surface plas- mon resonance [28,29] and in-fiber Bragg grating (FBG) [30,31] have been usedSensors and Actuators B 123 (2007) 594­605 Fiber optic sensing of liquid refractive index Argha of the fiber. The sensitivity of the sensor to refractive index change is dependent on cladding thickness

125

Modeling of two core photonic crystal fiber modal interferometer for refractive index measurement by equalization wavelength  

NASA Astrophysics Data System (ADS)

We propose a modification structure model of in-fiber sensor based on intermodal interference in two core photonic crystal fiber for external refractive index measuring. Essential characteristics and influences of the structure are investigated. Formation of an extreme (equalization wavelength) in phase constant spectral dependence is presented and its using for simple external refractive index determination.

Tatar, Peter; Kacik, Daniel

2013-08-01

126

A new phase space method for recovering index of refraction from travel times  

E-print Network

A new phase space method for recovering index of refraction from travel times Eric Chung 1 , Jianliang Qian 2 , Gunther Uhlmann 3 , and Hong­Kai Zhao 4 Abstract We develop a new phase space method for reconstructing the index of refraction of a medium from travel time measurements. The method is based on the so

Uhlmann, Gunther

127

A new phase space method for recovering index of refraction from travel times  

E-print Network

A new phase space method for recovering index of refraction from travel times Eric Chung1 , Jianliang Qian2 , Gunther Uhlmann3 , and Hong-Kai Zhao4 Abstract We develop a new phase space method for reconstructing the index of refraction of a medium from travel time measurements. The method is based on the so

Soatto, Stefano

128

Investigation of the light induced refractive index changes in Fe:PVA  

Microsoft Academic Search

The light induced modifications in thin films of Fe:PVA were studied by optical and Mössbauer spectroscopy. Under the UV exposure both the refractive index and the absorption coefficient are changing. The real part of the refractive index is measured using m-line Spectroscopy. As a function of UV exposure, the optical absorption as well as the Mössbauer spectra were measured. A

V. Kuncser; G. Filoti; A. Avramescu; R. Podgorsek; M. Biebricher; H. Franke

1997-01-01

129

In situ Mapping of Light-Induced Refractive Index Gratings by Digital Holographic Microscopy  

Microsoft Academic Search

This work presents a technique for in situ measurement of light-induced refractive index gratings in epoxy resin using digital holographic microscopy (DHM). The reconstructed phase image derived from a digital hologram can exhibit the grating structure and refractive index profile of an epoxy resin hologram. Reconstruction properties of finite aperture effect in the DHM system are considered and analyzed theoretically.

Yu-Chih Lin; Yi-Ta Lee; Xin-Ji Lai; Chau-Jern Cheng; Han-Yen Tu

2010-01-01

130

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

E-print Network

Interferometric Spectroscopy of Scattered Light Can Quantify the Statistics of Subdiffractional Refractive-Index Fluctuations L. Cherkezyan, I. Capoglu, H. Subramanian, J. D. Rogers, D. Damania, A. Taflove-field, diffraction-limited microscope image can quantify the refractive-index fluctuations of a label-free, weakly

Taflove, Allen

131

Material design for immersion lithography with high refractive index fluid (HIF)  

NASA Astrophysics Data System (ADS)

ArF immersion lithography is considered as the most promising next generation technology which enables to a 45 nm node device manufacturing and below. Not only depth of focus enlargement, immersion lithography enables to use hyper numerical aperture (NA) larger than 1.0 and achieve higher resolution capability. For 193nm lithography, water is an ideal immersion fluid, providing suitable refractive index and transmission properties. Furthermore the higher refractive index fluid is expected to provide a potential extension of optical lithography to the 32 nm node. This paper describes the material design for immersion lithography with high refractive index fluid. We have developed promising high refractive index fluids which satisfy the requirement for immersion fluid by screening wide variety of organic compounds. The physical and chemical properties of this high refractive index fluid are discussed in detail. Also the topcoat material which has good matching with high refractive index fluid is developed. While this topcoat material is soluble into aqueous TMAH developer, it does not dissolve into water or high refractive index fluid and gives suitable contact angle for immersion scan exposure. Immersion exposure experiments using high refractive index fluid with and w/o topcoat material was carried out and its lithographic performance is presented in this paper.

Miyamatsu, Takashi; Wang, Yong; Shima, Motoyuki; Kusumoto, Shiro; Chiba, Takashi; Nakagawa, Hiroki; Hieda, Katsuhiko; Shimokawa, Tsutomu

2005-05-01

132

Location of the Schlieren Image in Premixed Flames: Axially Symmetrical Refractive Index Fields  

Microsoft Academic Search

The deflection of light by the refractive index gradients inherent in flames has long been used for characterizing flame shape and position. For planar premixed flames, the relationship between light deflection and flame structure has been resolved analytically. This paper describes the deflection of light in axially symmetrical refractive index fields, employing numerical integration for structures representative of premixed flames.

Derek Dunn-Rankin; Felix Weinberg

1998-01-01

133

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

134

Optimization of 3D Plasmonic Crystal Structures for Refractive Index Sensing Joana Maria,  

E-print Network

Optimization of 3D Plasmonic Crystal Structures for Refractive Index Sensing Joana Maria, Tu T study the refractive index sensitive transmission of a 3D plasmonic crystal that consists of a square in sensitivity by an order of magnitude when the plasmonic crystal characteristics are optimized. 1. Introduction

Rogers, John A.

135

THz triangulation and stand-off measurement of the refractive index  

E-print Network

THz triangulation and stand-off measurement of the refractive index Christian Wiegand,1, Michael is capable of stand-off measurements, especially of retrieving the refractive index in a non-tactile manner. Keiding, M. van Exter, and Ch. Fattinger, "Far-infrared time-domain spectroscopy with terahertz beams

136

Shape and Refractive Index from Single-View Spectro-Polarimetric Images  

E-print Network

Shape and Refractive Index from Single-View Spectro-Polarimetric Images Cong Phuoc Huynh1 the object surface into the air. The diffuse polarisation of the reflection process is modelled of closed-form solutions for both the zenith angle and the refractive index in each iteration

Robles-Kelly, Antonio

137

Shape and Refractive Index Recovery from Single-View Polarisation Images Cong Phuoc Huynh1  

E-print Network

Shape and Refractive Index Recovery from Single-View Polarisation Images Cong Phuoc Huynh1 Antonio to the problem of simultaneous shape and refractive index recovery from multispectral polarisation imagery of the reflection process is modelled using a Transmitted Radiance Sinusoid curve and the Fresnel transmission

Robles-Kelly, Antonio

138

Three-Dimensional Negative Index of Refraction at Optical Frequencies by Coupling Plasmonic Waveguides  

E-print Network

that a material with a negative index of refraction can be used to construct a perfect lens [1], a quest for media at an inter- face of a positive index medium with the metamaterial. Indefinite materials form another class and the conversion of incident evanescent waves to propagating waves [8­11]. However, negatively refracting

Polman, Albert

139

Determination of the refractive index profile of polymer optical fiber preform by the transverse ray tracing method  

Microsoft Academic Search

In graded-index polymer optical fiber (GI-POF), the refractive index profile is an important parameter in defining its bandwidth. However, direct determination of the refractive index profile of GI-POF is difficult due to its extreme thinness. In this study, the refractive index distribution of the GI-POF is indirectly determined by measuring the refractive index distribution of the GI-POF perform by applying

Eisuke Nihei; Shigehiro Shimizu

2007-01-01

140

Optical polymers with tunable refractive index for nanoimprint technologies.  

PubMed

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

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

141

Refractive index-based detection of biomolecular interactions  

NASA Astrophysics Data System (ADS)

A biosensor was constructed by modifying the optics of a critical angle refractometer to enable it to measure changes in surface plasmon resonance. Initially, the utility of the critical angle refractometry to measure biomolecular interactions was examined using the Leica Automatic Critical Angle Refractometer 600 (AR600). While initial results suggested that the biomolecular interactions could be measured by critical angle refractometry, these proved to be an artifact of protein buildup on the surface. At lower concentrations of target protein, no change in the refractive index was observed. The AR600 was reconfigured from a critical angle refractometer to surface plasmon resonance technology to study molecular interactions between biomolecules. The performance of the SPR biosensor was demonstrated by measuring protein-protein interactions; specifically, avidin:anti-avidin interactions and streptavidin:anti-streptavidin interactions. Equilibrium dissociation constants were obtained by data analysis according to pseudo-first order binding kinetics. Polyclonal anti-streptavidin and monoclonal anti-avidin demonstrated affinity constants of 9.7 x 10-5 M-1 and 4.3 x 10-5 M-1 for their respective ligands.

Campagnolo, Christine; Ryan, Thomas; Atkinson, Robert C.; Batt, Carl A.

2001-03-01

142

Refractive index changes in lithium niobate crystals by high-energy particle radiation  

NASA Astrophysics Data System (ADS)

Irradiation of lithium niobate crystals with 41 MeV 3He ions causes strong changes of the ordinary and extraordinary refractive indexes. We present a detailed study of this effect. Small fluence of irradiation already yields refractive index changes about 5×10-4; the highest values reach 3×10-3. These index modulations are stable up to 100°C and can be erased thermally, for which temperatures up to 500°C are required. A direct correlation between the refractive index changes and the produced lattice vacancies is found.

Peithmann, Konrad; Zamani-Meymian, Mohammad-Reza; Haaks, Matz; Maier, Karl; Andreas, Birk; Breunig, Ingo

2006-10-01

143

Refractive index changes in lithium niobate crystals by high-energy particle radiation  

SciTech Connect

Irradiation of lithium niobate crystals with 41 MeV {sup 3}He ions causes strong changes of the ordinary and extraordinary refractive indexes. We present a detailed study of this effect. Small fluence of irradiation already yields refractive index changes about 5x10{sup -4}; the highest values reach 3x10{sup -3}. These index modulations are stable up to 100 degree sign C and can be erased thermally, for which temperatures up to 500 degree sign C are required. A direct correlation between the refractive index changes and the produced lattice vacancies is found.

Peithmann, Konrad; Zamani-Meymian, Mohammad-Reza; Haaks, Matz; Maier, Karl; Andreas, Birk; Breunig, Ingo [Helmholtz-Institut fuer Strahlen- und Kernphysik, Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany); Physikalisches Institut, Universitaet Bonn, Wegelerstrasse 8, D-53115 Bonn (Germany)

2006-10-15

144

Bent induced refractive index profile variation and mode field distribution of step-index multimode optical fiber  

NASA Astrophysics Data System (ADS)

The effect of bending of step-index optical fiber on its refractive index profile and the mode field distribution were investigated. An enhanced slab model is suggested in this investigation. A qualitative study has been done on a bent step-index optical fiber. A very small radius of bending curvature (R) has been reached, practically R is 9.25 mm. In this case a dramatic change of the refractive index profile has been observed with an induced birefringence. The refractive index profile is recovered from the interferograms which were generated by Mach-Zehnder interferometer. The interferogram has been analyzed using advanced image analyses software. We have proposed another approach to calculate the refractive index profile of bent optical fiber. In this approach the fiber is divided into layers and slabs, simultaneously. The induced refractive index profile variation of the bent optical fiber, for parallel and perpendicular components of the light beam, is calculated considering the refraction of the light beam traversing the fiber. The mode field distribution and mode numbers in these two directions of polarizations are determined for both straight and bent fibers.

Sokkar, T. Z. N.; Ramadan, W. A.; Shams El-Din, M. A.; Wahba, H. H.; Aboleneen, S. S.

2014-02-01

145

Effect of index of refraction on radiation characteristics in a heated absorbing, emitting, and scattering layer  

SciTech Connect

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 blackbody 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 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.

Siegel, R. (Lewis Research Academy, Cleveland, OH (United States)); Spuckler, C.M. (Heat Transfer Branch, Cleveland, OH (United States))

1992-08-01

146

Photonic crystal fiber modal interferometer for refractive index sensing of glycerine solution  

NASA Astrophysics Data System (ADS)

A photonic crystal fiber sensor was prepared for refractive index sensing. Based on modal interferometer theory, the relationships between the refractive index of glycerine solution and resonant wavelength shift of the sensor are analyzed by numerical simulation. A fiber optical device was designed to operate the sensing experiment. The sensing experiment shows that the resonant wavelength blued-shift for the sensor with refractive index in the range of 1.33~1.41 happens when increasing glycerine solution from 0.0% to 50.0% (v/v). The experimental results are approximately consistent with theory.

Huang, Jing; Li, Xueming; Yang, Jianchun

2013-12-01

147

Nonadiabatic fiber taper-based Mach-Zehnder interferometer for refractive index sensing  

NASA Astrophysics Data System (ADS)

A Mach-Zehnder interferometer based on a nonadiabatic fiber taper is proposed for refractive index (RI) sensing. Only the first order cladding guided mode is excited in the down-taper. The radius of the fiber core in the interference region is too thin (<1.64 ?m) to confine the fundamental mode in the fiber core, the fundamental core guided mode is converted to the fundamental cladding guided mode and interference occurs between it and the first order cladding guided mode. The sensitivity of the sensor is 980 nm per refractive index unit for the surrounding refractive index ranging from 1.332 to 1.392.

Xu, Linlin; Li, Ying; Li, Baojun

2012-10-01

148

Simultaneous time-resolved measurement of the reaction rates and the refractive index of photopolymerization processes.  

PubMed

We explore the use of imaging surface plasmon resonance (iSPR) to simultaneously measure the refractive index and reaction rates of the commercially available Ormocore photosensitive resist during photopolymerization. To this end, we adapted a commercially available iSPR device. We demonstrate good accuracy in the measurement of the refractive index determined independently of the thickness of the polymerized film. Furthermore, we demonstrate that the refractive index is proportional to the degree of cure (double bond conversion) of the resist. This allows the determination of the reaction rates of the polymerization processes, which show reasonable agreement with photodifferential scanning calorimetry measurements. PMID:20539350

Bak, Tomasz M; Beusink, J Bianca; Subramaniam, Vinod; Kanger, Johannes S

2010-06-10

149

Mechanisms of the refractive index change in DO11/PMMA due to photodegradation  

E-print Network

Using a white light interferometric microscope (WLIM) we measure the photodamage induced change in the complex index of refraction of disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate. We find that the change in the imaginary part of the refractive index is consistent with previous measurements of photodamage-induced absorbance change. Additionally, we find that the change in the real refractive index can be separated into a component due to damage to the dye molecules and a component due to irreversible damage to the polymer.

Anderson, Benjamin R

2014-01-01

150

Open-access optical microcavities for lab-on-a-chip refractive index sensing.  

PubMed

Open-access optical microcavities provide a novel approach to label-free lab-on-a-chip optofluidic sensing. They offer direct access to a highly confined electromagnetic field, and yield a femtoliter detection volume. This article describes the characteristics of these devices for refractive index sensing. We show that most of the ambient noise can be removed from the refractive index data by simultaneous tracking of resonances across an array of cavities. A sensitivity of 3.5 × 10(-4) RIU is demonstrated which corresponds to detecting the refractive index change caused by the presence of 500?000 glucose molecules in aqueous solution. PMID:25208130

Trichet, A A P; Foster, J; Omori, N E; James, D; Dolan, P R; Hughes, G M; Vallance, C; Smith, J M

2014-09-30

151

Sensitivity Analysis for Aerosol Refractive Index and Size Distribution Estimation Methods Based on Polarized Atmospheric Irradiance Measurements  

Microsoft Academic Search

Aerosol refractive index and size distribution estimations based on polarized atmospheric irradiance measurements are proposed together with its application to reflectance based vicarious calibration. A method for reflectance based vicarious calibration with aerosol refractive index and size distribution estimation using atmospheric polarization irradiance data is proposed. It is possible to estimate aerosol refractive index and size distribution with atmospheric polarization

Kohei Arai

2014-01-01

152

Method of producing optical quality glass having a selected refractive index  

DOEpatents

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.

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

2000-01-01

153

Three-dimensional optical metamaterial with a negative refractive index  

E-print Network

refraction of surface plasmons was recently demonstrated but was confined to a two-dimensional waveguide9 to the engineering and extension of the functionalities of metamaterials at terahertz15­17 and optical frequencies7

Cai, Long

154

Negative refractive index metamaterials supporting 2-D waves  

Microsoft Academic Search

Recent demonstrations of negative refraction utilize three-dimensional collections of discrete periodic scatterers to synthesize artificial dielectrics with simultaneously negative permittivity and permeability. In this paper, it is shown that planar, two-dimensional L-C transmission line networks in a high pass configuration can demonstrate negative refraction as a consequence of the fact that such media support propagating backward waves. Simulations illustrating negative

Ashwin K. Iyer; George V. Eleftheriades

2002-01-01

155

Dynamics and trajectory of nonautonomous rogue wave in a graded-index planar waveguide with oscillating refractive index  

NASA Astrophysics Data System (ADS)

We study rogue waves in a graded-index planar waveguide with oscillating refractive index. We find that an additional refractive index can be used to manipulate the trajectory of the rogue wave without changing its shape evolution characters. The density distribution profile of rogue wave with the highest peak can be kept well through manipulating the graded-index term and nonlinear coefficient. Furthermore, the trajectories of these nonautonomous rogue waves still look like an “X” shape. These results provide possibilities to manipulate rogue wave in nonautonomous nonlinear systems.

Wang, Li; Feng, Xiao-Qiang; Zhao, Li-Chen

2014-10-01

156

Refractive index and dispersion of butterfly chitin and bird keratin measured by polarizing  

E-print Network

the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive nm, 1.572, 1.552 and 1.541, and those of the feather barbules of the white goose Anas anas domestica and evolution of photonic structures in butterflies, incorporating the work of John Huxley (the Natural History

157

Refractive Index Measurement of the Isolated Crystalline Lens Using Optical Coherence Tomography  

PubMed Central

An optical coherence tomography system has been developed that was designed specifically for imaging the isolated crystalline lens. Cross-sectional OCT images were recorded on 40 lenses from 32 human donors with an age range of 6 – 82 years. A method has been developed to measure the axial thickness and average refractive index of the lens from a single recorded image. The measured average group refractive index at the measurement wavelength of 825 nm was converted to the average phase refractive index at 589 nm using lens dispersion data from the literature. The average refractive index for all lenses measured was 1.408 ± 0.005 which agrees well with recent MRI measurements of the lens index gradient. A linear regression of the data resulted in a statistically significant decrease in the average refractive index with age, but a simple linear model was insufficient to explain the age dependence. The results presented here suggest that the peak refractive index in the nucleus is closer to 1.420, rather than the previously accepted value of 1.406. PMID:18824191

Uhlhorn, Stephen R.; Borja, David; Manns, Fabrice; Parel, Jean-Marie

2008-01-01

158

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

NASA Astrophysics Data System (ADS)

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 5-65 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.

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

2014-09-01

159

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

PubMed Central

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

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

160

Mechanisms of the refractive index change in DO11/PMMA due to photodegradation  

NASA Astrophysics Data System (ADS)

Using a white light interferometric microscope (WLIM) we measure the photodamage induced change in the complex index of refraction of disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate. We find that the change in the imaginary part of the refractive index is consistent with previous measurements of photodamage-induced absorbance change. Additionally, we find that the irreversible change in the real refractive index can be separated into a component due to damage to the dye molecules and a component due to irreversible damage to the polymer. From the features of the polymers contribution to the irreversible change in the real refractive index we conclude that photo-thermal induced chain scission and cross linking are the underlying mechanisms of polymer damage.

Anderson, Benjamin R.; Kuzyk, Mark G.

2014-05-01

161

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

NASA Technical Reports Server (NTRS)

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.

Lading, Lars; Saffman, Mark; Edwards, Robert

1996-01-01

162

Study of Compact Tunable Filters Using Negative Refractive Index Transmission Lines  

E-print Network

, and thermal requirements, new filter technologies with different balances between these requirements are always desirable. Negative Refractive Index (NRI) transmission media was discovered 10 years ago with the unique property of negative phase propagation...

Lewis, Brian Patrick

2011-08-08

163

Dual-band tunable negative refractive index metamaterial with F-Shape structure  

NASA Astrophysics Data System (ADS)

This paper presents a negative refractive index tunable metamaterial based on F-Shape structure which is capable of achieving dual-band negative permeability and permittivity, thus dual-band negative refractive index. An electromagnetic simulation was performed and effective media parameters were retrieved. Numerical investigations show clear existence of two frequency bands in which permeability and permittivity both are negative. The two negative refractive index bandwidths are from 23.8 GHz to 24.1 GHz and from 28.3 GHz to 34.9 GHz, respectively. The geometry of the structure is simple so it can easily be fabricated. The proposed structure can be used in multiband and broad band devices, as the band range in second negative refractive index region is 7 GHz, for potential applications instead of using complex geometric structures and easily tuned by varying the separation between the horizontal wires.

Rizwan, Muhammad; Jin, Hai-Bo; Rehman, Fida; Hou, Zhi-Ling; Li, Jing-Bo; Butt, Faheem K.; Ali, Zulfiqar

2014-08-01

164

Refractive-index measurements in the near-IR using an Abbe refractometer  

NASA Astrophysics Data System (ADS)

A novel method to measure the refractive index n in the near-infrared by simple extensions to a standard Abbe refractometer is described. A technique is derived to correct for the dispersion of the glass prism and experimental results of refractive-index measurements at 0957-0233/8/6/003/img6 are compared with published data. These results prove the suitability of the described method, the accuracy being comparable to that of an Abbe refractometer used in the visible range; that is, the refractive index n can be measured to an accuracy of 0957-0233/8/6/003/img7. Finally, new refractive-index data at 830 nm are given for methanol, water, acetone, ethanol, cyclohexane, glycol, di-2-ethyl hexyl-sabacate (DEHS), carbon tetrachloride, glycerol, toluene, ethyl salicylate, methyl salicylate and cinnamaldehyde at 20 and 0957-0233/8/6/003/img8.

Rheims, J.; Köser, J.; Wriedt, T.

1997-06-01

165

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

PubMed Central

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 1.40–1.442, 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

Reyes, Mauricio; Monzón-Hernández, David; Martínez-Ríos, Alejandro; Silvestre, Enrique; Díez, Antonio; Cruz, José Luis; Andrés, Miguel V.

2013-01-01

166

Optical fiber sensor system for remote refractive index measurement based on Fresnel reflection using an OTDR  

NASA Astrophysics Data System (ADS)

In this work, we present an optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method, and investigate the refractive index sensibility of the sensor system in detail. The sensor system operates based on Fresnel reflection at the fiber's end that is cleaved as a vertical planar surface. Surrounding refractive index from a long distance away can be measured easily through utilizing this sensor system. The experimental setup is simple and easy to handle. Experimental results show the feasibility of the remote measurement of refractive index. The range of this measurement can reach ~30km, moreover, to ensure its repeatability and accuracy, we retest the same sample for many times, some of which are artificially applied with disturbance. Lastly we make a comparative analysis to certify that the sensor system has a good potential to remote practical applications.

Yuan, Jianying; Zhao, Chun-Liu; Ye, Manping; Zhang, Zaixuan; Jin, Shangzhong

2013-12-01

167

Peculiar radar cross section properties of metamaterials with zero index of refraction  

Microsoft Academic Search

In this paper, based on peculiar electromagnetic characteristics of metamaterials, peculiar radar cross section properties of metamaterials with zero index of refraction are discussed. These results provide some interested insights for potential applications in radar.

Wanzhao Cui; Jia Chen; Wei Ma; Lede Qiu

2008-01-01

168

Refractive index of a single ZnO microwire at high temperatures  

NASA Astrophysics Data System (ADS)

We report a study of refractive index of a wurtzite ZnO single crystal microwire at a temperature range from room temperature to about 400 K using optical cavity modes. The photoluminescence (PL) spectra of the ZnO microwire at different temperatures were performed using a confocal micro-photoluminescence setup. The whispering gallery modes observed in the PL spectra show a redshift both in the ultraviolet and the visible range as the temperature rises. The redshift is used to extract the refractive index of the ZnO microwire. The dispersion relations are deduced at different temperatures, and the results show that the refractive index increases with raising temperature for both transverse electric and transverse magnetic modes. The refractive index increases faster at a shorter wavelength, which is due to the fact that the shorter wavelength is closer to the resonance frequencies of ZnO microwire according to the Lorentz oscillator model.

Qiu, Kangsheng; Zhao, Yanhui; Gao, Yunan; Liu, Xiangbo; Ji, Xiaofan; Cao, Shuo; Tang, Jing; Sun, Yue; Zhang, Dongxiang; Feng, Baohua; Xu, Xiulai

2014-02-01

169

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

170

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

PubMed

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. PMID:23085920

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

2012-09-01

171

Modeling of gold circular sub-wavelength apertures on a fiber endface for refractive index sensing  

NASA Astrophysics Data System (ADS)

A finite-difference time-domain approach was used to investigate the excitation of surface plasmons of the circular sub-wavelength apertures on an optical fiber endface. This phenomenon provided the basis of a sensitive liquid refractive index sensor. The proposed sensor is compact and has the potential to be used in biomedical applications, having a sensitivity of (373 ± 16) nm per refractive index unit (RIU) as found through the variation of a reflection minimum with the wavelength.

Nguyen, Huy; Baxter, Gregory W.; Collins, Stephen F.; Sidiroglou, Fotios; Roberts, Ann; Davis, Timothy J.

2012-09-01

172

Enhancement and focusing of light in nanostructured quasi-zero-refractive-index films  

NASA Astrophysics Data System (ADS)

We present theoretical and experimental proofs that our synthesized composite material with silver nanoparticles has a quasi-zero refractive index over a wide wavelength range, and the enhanced optical transmission is observed in the material layer. The formulas of the reflectance and transmittance of a layer with a quasi-zero refractive index are consistent with the experimental data. The optical transmission is significantly enhanced by focusing the light that is scattered by the composite film.

Gadomsky, O. N.; Stepin, S. N.; Ushakov, N. M.; Gadomskaya, N. V.; Pereskokov, E. A.

2014-11-01

173

Spatially resolved measurement of femtosecond laser induced refractive index changes in transparent materials.  

PubMed

We present a practical method to determine femtosecond laser induced refractive index changes in transparent materials. Based on an iterative Fourier transform algorithm, this technique spatially resolves the refractive index of complex structures by combining the dimensions of the modified region with the corresponding phase change extracted from far-field intensity measurements. This approach is used to characterize optical waveguides written by a femtosecond laser in borosilicate glass. PMID:22825206

Berlich, René; Choi, Jiyeon; Mazuir, Clarisse; Schoenfeld, Winston V; Nolte, Stefan; Richardson, Martin

2012-07-15

174

Light-induced refractive index changes in singlemode channel waveguides in KTiOPO 4  

Microsoft Academic Search

Light-induced changes of the effective refractive index in Rb ? K ion-exchanged singlemode channel waveguides in KTiOPO4 have been investigated in the visible wavelength region dependent on time, guided optical mode intensity and temperature. A hypothesis for the explanation of the light-induced effects is suggested. Thermooptic and pyroelectric effects are discussed. The light-induced refractive index changes do not restrict the

J.-P Ruske; M. Rottschalk; S. Steinberg

1995-01-01

175

Thermal lens investigation of the temperature dependence of the refractive index of organo–aqueous solutions  

Microsoft Academic Search

The thermal lens technique has been used to experimentally determine the temperature of maximum refractive index (TMRi) of low molarity aqueous methanol solutions. The well-known decrease in the measured TMRi is observed with increasing concentration of methanol. At the TMRi, the temperature dependence of refractive index (dn\\/dT) is zero, resulting in the absence of a thermal lens signal. In this

Simon M Colcombe; Richard D Snook

1999-01-01

176

In situ measurement of refractive index changes induced by gamma radiation in germanosilicate fibers  

Microsoft Academic Search

We propose a technique to measure in situ the refractive index changes induced by ionizing radiation in single-mode optical fibers. This change can be derived from the channel drift appearing in narrow channel wavelength-division-multiplexing couplers exposed to gamma radiation. We measured a radiation-induced refractive index change of about 5 10-6\\/kGy[H2O] at low doses and 5 10-7\\/kGy[H2O] at higher doses. No

A. Fernandez Fernandez; B. Brichard; F. Berghmans

2003-01-01

177

Experimental verification of backward-wave radiation from a negative refractive index metamaterial  

Microsoft Academic Search

A composite medium consisting of an array of fine wires and split-ring resonators has been previously used to experimentally verify a negative index of refraction. We present a negative refractive index (NRI) metamaterial that goes beyond the original split-ring resonator\\/wire medium and is capable of supporting a backward cone of radiation. We report experimental results at microwave frequencies that demonstrate

Anthony Grbic; George V. Eleftheriades

2002-01-01

178

High refractive index without absorption in a rare-earth-ion-doped optical fiber  

NASA Astrophysics Data System (ADS)

We demonstrate a new scheme for realizing the high refractive index with zero absorption in an Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF optical fiber. It is found that the refraction index of the probe laser can easily be controlled via adjusting properly the parameters of the corresponding system. Our scheme may provide some new possibilities for technological applications in optical-fiber communication.

Wang, Zhiping; Yu, Benli

2012-11-01

179

Molecular Expressions: Polarized Light Microscopy - The Fresnel or Refractive Index Ellipsoid  

NSDL National Science Digital Library

This item is an interactive Java simulation for students of introductory physics or optics on the phenomenon known as birefringence. It features a cross-sectional Fresnel ellipsoid which can be rotated in three dimensions. The optic axis and refractive index are adjustable, allowing users to explore how the shape and dimension of the ellipsoid is a function of refractive index. This item is part of a larger collection of materials on introductory optics developed by the National High Magnetic Field Laboratory.

Davidson, Michael; Parry-Hill, Matthew J.; Spring, Kenneth R.

2008-08-23

180

Effect of refractive index-mismatch on laser microfabrication in silica glass  

Microsoft Academic Search

.   We studied the peculiarities of femtosecond laser microfabrication in silica glass with a refractive index that did not exactly\\u000a match the value for which the focusing optics is designed. Spherical aberrations resulting from a small refractive index mismatch\\u000a were found to increase the size and distort the shape of photodamaged regions, thus reducing the spatial resolution of the\\u000a microfabrication.

A. Marcinkevicius; V. Mizeikis; S. Juodkazis; S. Matsuo; H. Misawa

2003-01-01

181

Planar optical waveguides for optical panel having gradient refractive index core  

DOEpatents

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.

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

2001-01-01

182

Spin angular momentum transfer from TEM00 focused Gaussian beams to negative refractive index spherical particles  

PubMed Central

We investigate optical torques over absorbent negative refractive index spherical scatterers under the influence of linear and circularly polarized TEM00 focused Gaussian beams, in the framework of the generalized Lorenz-Mie theory with the integral localized approximation. The fundamental differences between optical torques due to spin angular momentum transfer in positive and negative refractive index optical trapping are outlined, revealing the effect of the Mie scattering coefficients in one of the most fundamental properties in optical trapping systems. PMID:21833372

Ambrosio, Leonardo A.; Hernandez-Figueroa, Hugo E.

2011-01-01

183

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

DOEpatents

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.

Yeung, Edward S. (Ames, IA); Woodruff, Steven D. (Ames, IA)

1984-06-19

184

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

SciTech Connect

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.

Assanto, Gaetano [Department of Electronic Engineering, NooEL-Nonlinear Optics and OptoElectronics Lab, University of Rome 'Roma Tre', Via della Vasca Navale 84, 00146 Rome (Italy); Minzoni, Antonmaria A. [Department of Mathematics and Mechanics, Fenomenos Nonlineales y Mecanica (FENOMEC), Instituto de Investigacion en Matematicas Aplicadas y Sistemas, Universidad Nacional Autonoma de Mexico, 01000 Mexico D.F. (Mexico); Smyth, Noel F. [School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Worthy, Annette L. [School of Mathematics and Applied Statistics, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522 (Australia)

2010-11-15

185

Highly Sensitive Refractive Index Sensor Based on Adiabatically Tapered Microfiber Long Period Gratings  

PubMed Central

We demonstrate a refractive index sensor based on a long period grating (LPG) inscribed in a special photosensitive microfiber with double-clad profile. The fiber is tapered gradually enough to ensure the adiabaticity of the fiber taper. In other words, the resulting insertion loss is sufficiently small. The boron and germanium co-doped inner cladding makes it suitable for inscribing gratings into its tapered form. The manner of wavelength shift for refractive indices (RIs) differs from conventional LPG, and the refractive index detection limit is 1.67 × 10?5. PMID:24141267

Ji, Wen Bin; Tjin, Swee Chuan; Lin, Bo; Ng, Choong Leng

2013-01-01

186

Refractive index profiling of an optical waveguide from the determination of the effective index with measured differential fields.  

PubMed

The evanescent tails of a guiding mode as well as its first and second derivatives were measured by a modified end-fire coupling method. The effective index of the waveguide can be obtained by simultaneously fitting these three fields using single parameter. Combined with an inverse calculation algorithm, the fields with fitted evanescent tails showed great improvement in the refractive index profiling of the optical waveguide, especially at the substrate region. Single-mode optical fibers and planar waveguides of proton-exchanged (PE) and titanium-indiffusion (Ti:LiNbO3) on lithium niobate substrates with different refractive index profiles were measured for the demonstration. PMID:23187531

Tsai, Wan-Shao; Ting, San-Yu; Wei, Pei-Kuen

2012-11-19

187

Refractive index profiling of a GRIN optical fiber using a modulated speckled sheet of light  

NASA Astrophysics Data System (ADS)

A method for calculating the refractive index of GRIN optical fiber from its transverse interference pattern is presented.In this method the transverse interference fringe pattern through an optical fiber using a sheet of light is applied to get the refractive index profile of it. The optical fiber is not immersed in a matching liquid as used in different techniques [Barakat N, El-Hennawi HA, El-Zaiat SY, Hassan R. Pure Appl Opt 1996;5:27]. In this method a sheet of He-Ne laser light is allowed to illuminate the fiber. The light sheet is divided into two parts, the first is refracted through the fiber while the second is used as a reference beam. Interference pattern will be obtained between these two rays displaying the refractive index variation along the fiber radius. The fringe shift of such interference pattern has been measured and used to calculate the deflection angle of light refracted by the fiber and the cladding. An equation is derived to calculate the refractive index profile difference ratio ?n at different positions across the fiber cross section in terms of the corresponding deflection angle and is verified experimentally. The optical path difference between these two rays (refracted and reference beam divided by the fiber) has been derived and the fringe shift obtained has been used to calculate the refractive index profile of the fiber. Introducing a ground glass screen on the passage of the two light beams (refracted and reference beam divided by the fiber), two superimposed identical speckle patterns are formed leading to the formation of a third speckle pattern modulated by a grid structure displaying the optical thickness of the fiber.

El-Ghandoor, H.; El-Ghafar, E. Abd.; Hassan, R.

1999-10-01

188

A novel type of proximity focusing RICH counter with multiple refractive index aerogel radiator  

E-print Network

A proximity focusing ring imaging Cherenkov detector, with the radiator consisting of two or more aerogel layers of different refractive indices, has been tested in 1-4 GeV/c pion beams at KEK. Essentially, a multiple refractive index aerogel radiator allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation in single photon angular resolution associated with the increased uncertainty of the emission point. With the refractive index of consecutive layers suitably increasing in the downstream direction, one may achieve overlapping of the Cherenkov rings from a single charged particle. In the opposite case of decreasing refractive index, one may obtain well separated rings. In the former combination an approximately 40% increase in photon yield is accompanied with just a minor degradation in single photon angular resolution. The impact of this improvement on the pion/kaon separation at the upgraded Belle detector is dis...

Iijima, T; Adachi, I; Fratina, S; Fukushima, T; Gorisek, A; Kawai, H; Konishi, M; Kozakai, Y; Krizan, P; Matsumoto, T; Mazuka, Y; Nishida, S; Ogawa, S; Ohtake, S; Pestotnik, R; Saitoh, S; Seki, T; Sumiyoshi, T; Uchida, Y; Unno, Y; Yamamoto, S

2005-01-01

189

A single-element interferometer for measuring refractive index of transparent liquids  

NASA Astrophysics Data System (ADS)

A simple and stable method based on a single-element interferometer for accurately measuring refractive index of transparent liquids was demonstrated. The refractive index is measured by rotating a rectangular optical glass cell which contains sample liquid and air simultaneously, and by calculating interference fringe shift number which is detected from an interferogram. This method was successfully used to measure the refractive indices of various transparent liquids including distilled water, ethanol and NaCl-water and ethanol-water solutions at various concentrations. The temperature- dependent refractive index of distilled water was also measured. Furthermore, our method is simple to implement, vibration insensitive, and of high accuracy up to 10-4.

Zhang, Tao; Feng, Guoying; Song, Zheyi; Zhou, Shouhuan

2014-12-01

190

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

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

191

High water content hydrogel with super high refractive index.  

PubMed

Transparent, high water content (>65%), and cytocompatible hydrogels, which also possess super high refractive indices (RI?>?1.5), are needed for ophthalmological applications. Most hydrogels can achieve either high RI or high water content but not both in the same system because water is a low RI material. Here, high water content/high RI hydrogels fabricated through elevated-temperature UV polymerization of an aqueous solution of acrylamide (AM) and methacrylamide (MAM) with tri(ethylene glycol) dimethacrylate (TEDA) crosslinker are reported. By varying the AM:MAM ratios (2:8 to 8:2) and crosslinker density (5 to 11?mol %), it is discovered that high water content (66%) AM:MAM copolymer hydrogels exhibiting anomalously high refractive indices (1.53); they are also colorless, transparent (99.4%), and cytocompatible with human keratinocytes. PMID:23881874

Zhou, Chuncai; Heath, Daniel E; Sharif, Abdul Rahim Mohamed; Rayatpisheh, Shahrzad; Oh, Bernice H L; Rong, Xu; Beuerman, Roger; Chan-Park, Mary B

2013-11-01

192

Index of Refraction Measurements Using a Laser Distance Meter  

NASA Astrophysics Data System (ADS)

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 to travel from the laser to a detector. These experiments are relatively costly and use sophisticated equipment not always available in an educational institution. Our method uses a laser distance meter that can be purchased for under 80. The meter uses the accepted value of the speed of light in vacuum to determine distances based on a measured time of flight. The output is distance in meters or feet.

Ochoa, Romulo; Fiorillo, Richard; Ochoa, Cris

2014-03-01

193

Formation of the refractive index profile in the graded index polymer optical fiber for gigabit data transmission  

Microsoft Academic Search

Bandwidth characteristics of the large core graded index polymer optical fiber (GI-POF) are theoretically and experimentally clarified. The refractive index profile of the GI-POF was controlled by interfacial-gel polymerization to investigate the relation between the index profile and the bandwidth characteristics. It was experimentally confirmed that the maximum bandwidth of the poly methyl methacrylate (PMMA) base GI-POF is at most

Takaaki Ishigure; Masataka Satoh; Osamu Takanashi; Eisuke Nihei; Takayuki Nyu; Shuntaro Yamazaki; Yasuhiro Koike

1997-01-01

194

Measurement technique for the refractive-index difference between adjacent layers of a multilayered structure  

NASA Astrophysics Data System (ADS)

A measurement technique is presented for determining simultaneously the refractive-index difference between a multilayered medium and the layer thickness. The technique is simple because it is based on measurement of the standard reflection characteristics of light. Use of this technique to measure the index difference between sputtered fused silica and Pyrex glass is described. The applicable range and advantages are also discussed.

Kishioka, K.; Hashimoto, M.

1980-08-01

195

Light induced refractive index changes in PMMA films doped with styrene  

Microsoft Academic Search

Solutions of poly(methyl methacrylate) in styrene are used to produce thin polymer films (1µm–20µm) saturated with styrene monomer. In the illuminated areas refractive index changes up to 10-2 are achieved by photoinduced polymerisation. The index patterns may be fixed by annealing treatments removing the residual monomer.

H. Franke; H. G. Festl; E. Krätzig

1984-01-01

196

Composite chiral metamaterials with negative refractive index and high values of the figure of  

E-print Network

Composite chiral metamaterials with negative refractive index and high values of the figure and Technology Hellas (FORTH), and Department of Materials Science and Technology, University of Crete, 71110 bands of negative index can be obtained for circularly polarized waves. These bands are all above

197

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

198

Liquid refractive index sensing independent of opacity using an optofluidic sensor based on diffraction  

E-print Network

We have implemented a multi-functional optofluidic sensor that can monitor changes in the refractive index and pressure of biofluid simultaneously and can detect free-solution molecular interaction in-situ. In this paper, we demonstrate two major improvements of this sensor proven by both simulation and experiments. One improvement is the broader measurement range of refractive index by making the diffraction grating with high-index polymer. The other improvement is the separation of refractive index sensing from opacity sensing by using the relative power ratio of diffraction orders. This simple, compact and low-cost multi-functional optofluidic sensor has the potential to be used for in-situ biofluid monitoring.

Xu, Zhida

2014-01-01

199

Reconstruction of fundamental absorption spectra of material by its refractive index spectrum in transparency region  

NASA Astrophysics Data System (ADS)

The method of calculation of the fundamental absorption index spectrum k(E) of crystalline dielectrics on the basis of refractive index spectrum n(E0) in the range of transparency by solving the Kramers-Kronig integral equation has been worked out. Limited experimental precision of refractive index measurements, (delta) n/n equals 10-4, permits us to obtain low-structuralized (smoothed) k(E) spectra. The method was applied to the ferroelectrical triglycine sulphate crystal. The refractive index dispersion of this crystal reveals the interaction of elementary oscillators. The temperature dependence of characteristic parameter of this interaction was studied in the region including the phase transition (Tc equals 49 degrees Celsius).

Andriyevsky, Bohdan V.

1995-11-01

200

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

201

High Refraction Index Polysiloxanes via Organometallic Routes - An Overview  

NASA Astrophysics Data System (ADS)

Processes based on four organometallic routes leading to phenylethenyl substituted siloxanes are reviewed. Such materials, exhibiting high refraction indices, can be made by hydrosilylation of phenylacetylenes with Si-H moieties containing siloxane oligomers and polymers. On the other hand reactions between vinyl containing siloxanes with haloaryls or styrenes lead to the same systems via Heck or metathetic and silylative coupling. The effectiveness of the catalytic processes is analyzed from the point of view of side reactions, required catalyst concentration and reaction conditions. At the current state of knowledge the Heck coupling offers synthesis of the desired phenylethenyl substituted silicone fluids using technologically most attractive pathway.

Sta?zyk, W?odzimierz A.; Czech, Anna; Duczmal, Wojciech; Ganicz, Tomasz; Noskowska, Ma?gorzata; Szel?g, Anna

202

Mapping the refractive index sensing range of the GFP fluorescence decay with FLIM  

NASA Astrophysics Data System (ADS)

The fluorescence decay of the biologically important enhanced green fluorescent protein (GFP) is a function of the refractive index of its environment (Suhling et al, Biophys J 83, 3589-3595, 2002). To address the question whether this effect can be exploited to image the local environment of specific proteins in cell biology, we need to determine the distance over which the GFP fluorescence decay is sensitive to the refractive index. To this end, we employ Fluorescence Lifetime Imaging (FLIM) of GFP in buffer solution at an air and at an oil interface. This approach allows us to map the fluorescence lifetime as a function of distance from the interface. Preliminary data show that the average fluorescence lifetime of GFP increases near a buffer/air interface and decreases near a buffer/oil interface. Similar results showing the same trend are obtained using fluorescein in buffer at an oil and at an air interface. The range over which this fluorescence lifetime change occurs is found to be of the order several micrometers which is consistent with theoretical models. In addition, GFP-tagged MHC proteins in fixed cells were imaged in different refractive index media using FLIM. It appears that the average GFP fluorescence lifetime in cells is also sensitive to different refractive index environments, and is inversely proportional to the square of the refractive index.

Jones, Carolyn; Suhling, Klaus

2006-02-01

203

Novel optical devices based on the tunable refractive index of magnetic fluid and their characteristics  

NASA Astrophysics Data System (ADS)

As a new type of functional material, magnetic fluid (MF) is a stable colloid of magnetic nanoparticles, dressed with surfactant and dispersed in the carrier liquid uniformly. The MF has many unique optical properties, and the most important one is its tunable refractive index property. This paper summarizes the properties of the MF refractive index and the related optical devices. The refractive index can be easily controlled by external magnetic field, temperature, and so on. But the tunable refractive index of MF has a relaxation effect. As a result, the response time is more than milliseconds and the MF is only suitable for low speed environment. Compared with the traditional optical devices, the magnetic fluid based optical devices have the tuning ability. Compared with the tunable optical devices (the electro-optic devices (LiNbO3) of more than 10 GHz modulation speed, acoustic-optic devices (Ge) of more than 20 MHz modulation speed), the speed of the magnetic fluid based optical devices is low. Now there are many applications of magnetic fluid based on the refractive index in the field of optical information communication and sensing technology, such as tunable beam splitter, optical-fiber modulator, tunable optical gratings, tunable optical filter, optical logic device, tunable interferometer, and electromagnetic sensor. With the development of the research and application of magnetic fluid,a new method, structure and material to improve the response time can be found, which will play an important role in the fields of optical information communication and sensing technology.

Zhao, Yong; Zhang, Yuyan; Lv, Riqing; Wang, Qi

2011-12-01

204

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

205

Metrology of undoped double-sided polished silicon wafer: surface, thickness and refractive index profile measurements  

NASA Astrophysics Data System (ADS)

In this investigation, we describe a technique to obtain the 3D profile of surface, thickness and refractive index of an undoped double-side polished Si wafer at once. This technique is based on low coherence scanning interferometry (LCSI) and spectrally-resolved interferometry (SRI) using a NIR light, which is around 1 ?m, for which transmission is non-zero for undoped silicon and also detectable by the typical visible CCD camera. LCSI allows for the measurements of surface, thickness and refractive index profiles of the Si wafer while SRI can determine their nominal values. For group refractive index measurements, the target which consists of a Si wafer segment and a mirror was designed. Consequently, the combination of these two techniques with the target enables to measure surface, thickness and refractive index profiles simultaneously and accurately. In the experiments, an undoped double sided polished (DSP) Si wafer with 475 ?m thickness was measured and the 3D profiles of optical thickness, geometrical thickness, group refractive index were successfully obtained. Because of not using an expensive IR CCD camera and an optical source, the proposed technique is cost-effective.

Lee, Ho-Jae; Joo, Ki-Nam

2014-05-01

206

a Novel Type of Proximity Focusing Rich Counter with Multiple Refractive Index Aerogel Radiator  

Microsoft Academic Search

A proximity focusing ring imaging Cherenkov detector, with the radiator consisting of two or more aerogel layers of different refractive indices, has been tested in 1-4 GeV\\/c pion beams at KEK. Essentially, a multiple refractive index aerogel radiator allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation

P. Krizan; S. Korparbc; I. Adachid; S. Fratinac; T. Fukushimae; A. Goriÿsekc; H. Kawaie; M. Konishie; Y. Kozakaia; P. Kriÿzanfc; T. Matsumotog; Y. Mazukaa; S. Nishidad; S. Ogawah; S. Ohtakeh; R. Pestotnik; S. Saitohd; T. Sekig; T. Sumiyoshig; Y. Uchidad; Y. Unnod; S. Yamamotog

2006-01-01

207

A novel type of proximity focusing RICH counter with multiple refractive index aerogel radiator  

Microsoft Academic Search

A proximity focusing ring imaging Cherenkov detector, with the radiator consisting of two or more aerogel layers of different refractive indices, has been tested in 1–4GeV\\/c pion beams at KEK. Essentially, a multiple refractive index aerogel radiator allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation in

T. Iijima; S. Korpar; I. Adachi; S. Fratina; T. Fukushima; A. Gorisek; H. Kawai; H. Konishi; Y. Kozakai; P. Krizan; T. Matsumoto; Y. Mazuka; S. Nishida; S. Ogawa; S. Ohtake; R. Pestotnik; S. Saitoh; T. Sumiyoshi; Y. Uchida; Y. Unno; S. Yamamoto

2005-01-01

208

A novel type of proximity focusing RICH counter with multiple refractive index aerogel radiator  

Microsoft Academic Search

A proximity focusing ring imaging Cherenkov detector, with the radiator consisting of two or more aerogel layers of different refractive indices, has been tested in 1–4GeV\\/c pion beams at KEK. Essentially, a multiple refractive index aerogel radiator allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation in

S. Korpar; I. Adachi; K. Fujita; T. Fukushima; A. Gorisek; D. Hayashi; T. Iijima; T. Ikado; T. Ishikawa; H. Kawai; Y. Kozakai; P. Krizan; A. Kuratani; Y. Mazuka; T. Nakagawa; S. Nishida; S. Ogawa; R. Pestotnik; T. Seki; T. Sumiyoshi; M. Tabata; Y. Unno

2007-01-01

209

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

SciTech Connect

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.

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

2003-07-24

210

Refractive index profiles of planar optical waveguides in ?-BBO produced by silicon ion implantation  

Microsoft Academic Search

The planar waveguides have been fabricated in z-cut beta barium metaborate crystals by 2.8MeV Si+ ion implantation with doses of 1×1015 and 3×1015ions\\/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

Xue-Lin Wang; Feng Chen; Fei Lu; Gang Fu; Shi-Ling Li; Ke-Ming Wang; Qing-Ming Lu; Ding-Yu Shen; Hong-Ji Ma; Rui Nie

2004-01-01

211

Measurement of the index of refraction of ?m crystals by a confocal laser microscope--potential application for the refractive index mapping of ?m scale.  

PubMed

A conventional laser microscope can be used to derive the index of refractivity by the ratio of geometrical height of the transparent platelet to the apparent height of the normal incident light for very small crystals in the wide size range. We demonstrate that the simple method is effective for the samples from 100 ?m to 16 ?m in size using alkali halide crystals as a model system. The method is also applied for the surface fractured micro-crystals and an inclined crystal with microscopic size regime. Furthermore, we present two-dimensional refractive index mapping as well as two-dimensional height profile for the mixture of three alkali halides, KCl, KI, and NaCl, all are ?m in size. PMID:24880379

Kimura, Keisaku; Sato, Seiichi

2014-05-01

212

Measurement and characteristic analysis of refractive index of biological medium adsorption on two-dimensional photonic crystal surface  

NASA Astrophysics Data System (ADS)

The two-dimensional (2D) SiO2 photonic crystal (PC) is constructed with the substrate of polyester film. The PC period is 800nm, and the duty cycle is 0.5.The high refractive index coating is deposited on the surface of PC. Rigorous coupled-wave (RCWA) theory is used to analyze 2D PC narrowband reflection spectrum characteristic. A relationship model between reflection peak wavelength and medium refractive index adsorption on surface of 2D PC is established. The conclusion shows that there is a linear relationship between reflection wavelength of the PC and the refractive index of adsorption medium, with the refractive index of adsorption medium in the range of 1.3-1.8. The effects of the refractive index of deposited coating on the sensitivity of the PC biosensor are analyzed. With the increase of the refractive index of the deposited coating, the sensitivity of the sensor is increasing.

Tong, Kai; Lu, Jianru; Zhang, Zhenguo; Wang, Hui-bo; Chen, Ying

2014-07-01

213

Design of a compact and high sensitive refractive index sensor base on metal-insulator-metal plasmonic Bragg grating.  

PubMed

A nanometric and high sensitive refractive index sensor based on the metal-insulator-metal plasmonic Bragg grating is proposed. The wavelength encoded sensing characteristics of the refractive index sensor were investigated by analyzing its transmission spectrum. The numerical results show that a good linear relationship between the Bragg wavelength and the refractive index of the sensing material can be obtained, which is in accordance with the analytical results very well. A high refractive index sensitivity of 1488nm/RIU around Bragg resonance wavelength of 1550nm was obtained. Besides, the simulation results show that the sensitivity is depended on the Bragg resonance wavelength and the longer the Bragg resonance wavelength, the higher sensitivity can be obtained. Furthermore, the figure of merit of the refractive index sensor can be greatly increased by introducing a nano-cavity in the proposed plasmonic Bragg grating structure. This work pave the way for high sensitive nanometric refractive index sensor design and application. PMID:25402107

Binfeng, Yun; Guohua, Hu; Ruohu, Zhang; Yiping, Cui

2014-11-17

214

Direct characterization of ultraviolet-light-induced refractive index structures by scanning near-field optical microscopy  

Microsoft Academic Search

We have applied a reflection scanning near-field optical microscope to directly probe ultraviolet (UV)-light-induced refractive index structures in planar glass samples. This technique permits direct comparison between topography and refractive index changes (10-5 -10-3) with submicrometer lateral resolution. The proposed method yields detailed information about the topography and index profiles of UV-written waveguides

M. Svalgaard; S. Madsen; J. M. Hvam; M. Kristensen

1998-01-01

215

Mode transition in complex refractive index coated single-mode-multimode-single-mode structure.  

PubMed

By coating a single-mode-multimode-single-mode (SMS) structure with a high refractive index thin-film it is possible to obtain a transition of modes for specific combinations of thin-film thickness, thin-film refractive index and surrounding medium refractive index, which permits to develop devices with a high sensitivity to specific parameters. In order to gain a better knowledge of the phenomenon the experimental results are corroborated numerically with the Transfer-Matrix-Method. The influence of losses in the thin-film has also been studied. The results obtained prove that a thin-film coated SMS structure is a simple and cost-effective platform for development of sensors and optical filters. PMID:23736487

Socorro, Abian B; Del Villar, Ignacio; Corres, Jesus M; Arregui, Francisco J; Matias, Ignacio R

2013-05-20

216

Optical extinction, refractive index, and multiple scattering for suspensions of interacting colloidal particles  

NASA Astrophysics Data System (ADS)

We provide a general microscopic theory of the scattering cross-section and of the refractive index for a system of interacting colloidal particles, exact at second order in the molecular polarizabilities. In particular: (a) we show that the structural features of the suspension are encoded into the forward scattered field by multiple scattering effects, whose contribution is essential for the so-called "optical theorem" to hold in the presence of interactions; (b) we investigate the role of radiation reaction on light extinction; (c) we discuss our results in the framework of effective medium theories, presenting a general result for the effective refractive index valid, whatever the structural properties of the suspension, in the limit of particles much larger than the wavelength; (d) by discussing strongly-interacting suspensions, we unravel subtle anomalous dispersion effects for the suspension refractive index.

Parola, Alberto; Piazza, Roberto; Degiorgio, Vittorio

2014-09-01

217

Refractive index insensitive temperature sensor based on coaxial waveguide fiber modal interferometer  

NASA Astrophysics Data System (ADS)

A refractive index insensitive temperature sensor based on coaxial dual-waveguide optical fiber was proposed and demonstrated. The coaxial fiber contains a central core along the fiber axis and an annular core between the inner/outer claddings. By inserting the coaxial fiber in between two single mode fibers through core-offset splicing, cladding modes are excited at the splice point and therefore a modal Mach-Zehnder interferometer is achieved. The effective refractive index of the inner cladding mode is independent of the external refractive index due to the existence of the annular core. Owing to the large thermo-optic coefficient difference between the coaxial fiber's core and cladding, the modal interferometer has high temperature sensitivity. Such an interferometer is extremely suitable for temperature measurement in wet or liquid environment.

Zhou, Ai; Xu, Quan; Zheng, Tuo; Yang, Jun; Yang, Yuanyuan; Yuan, Libo

2013-09-01

218

Core-cladding mode recoupling based fiber optic refractive index sensor  

NASA Astrophysics Data System (ADS)

We present a compact and robust fiber optic refractive index sensor based on a tilted fiber Bragg grating (TFBG) inscribed in a thin-core fiber that is spliced to a standard single-mode fiber (SSMF). Due to the core mismatch between the SSMF and the thin-core fiber, cladding modes generated from the TFBG can be back into SSMF for detection. Since the effective refractive index of a cladding mode is dependent on the surrounding refractive index (SRI), the cladding-mode resonances can be used for measurement. We fabricate the sensor probe and test it in a series solution with different SRIs, and the experimental results agree with the theoretical analysis. The repeatability of the sensor is also tested in the same SRI range. We demonstrate its capability and simplicity to use this sensor for a wide range SRI measurement.

Zhang, Xinpu; Peng, Wei; Liu, Yun; Pan, Lujun

2013-05-01

219

Fiber structure based on a depressed inner cladding fiber for bend, refractive index and temperature sensing  

NASA Astrophysics Data System (ADS)

A fiber-optic structure based on a section of a double-clad fiber with depressed inner cladding is investigated for bend, refractive index and temperature sensing. The structure is formed by splicing a section of SM630 fiber between two standard fibers SMF-28. The operation principle relies on the sensitivity of cladding modes that are induced at a splice of fibers having different refractive index profiles. The mode structure of the double cladding fiber and the mechanism of formation of dips in the transmission spectra are discussed. The transmission spectra of the structure are measured for different curvatures of the inserted fiber section. The shift of dips to long wavelengths with increasing curvature of the fiber is observed and its dependence on the fiber section length and the direction of bending is investigated. The sensitivities of the spectral dips to the external refractive index and temperature are also measured.

Ivanov, Oleg V.; Zlodeev, Ivan V.

2014-01-01

220

Methods to calibrate and scale axial distances in confocal microscopy as a function of refractive index  

E-print Network

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 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 theo...

Besseling, Thijs Herman; van Blaaderen, Alfons

2014-01-01

221

Lattice and electronic contributions to the refractive index of CuWO4  

NASA Astrophysics Data System (ADS)

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 ?(?) = 4.5(1) for light polarization parallel to the c-axis and ?(?) = 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.

Ruiz-Fuertes, J.; Pellicer-Porres, J.; Segura, A.; Rodríguez-Hernández, P.; Muñoz, A.

2014-09-01

222

Interferometric technique for measuring the refractive index variation of a liquid with temperature.  

PubMed

A technique for measuring the variation of refractive index of a liquid as a function of temperature or solute concentration using a Mach-Zender interferometer is described. The principal difficulty of obtaining a uniform temperature along the optical path in the sample liquid while simultaneously varying the temperature at a reasonable rate is overcome by heating the liquid in a separate vessel and injecting the heated fluid into the test vessel as a series of jets to encourage turbulent mixing. An equivalent resolution in the refractive index variation of 2x10(-6) was obtained. The above method was used to determine the variation of refractive index in a 0.1% NaCl/H(2)O solution in the temperature range 23 degrees -33 degrees C. PMID:18699208

Boxman, R L; Shlien, D J

1978-06-01

223

RF power dependence of refractive index of room temperature sputtered ZnO:Al thin films  

NASA Astrophysics Data System (ADS)

The deposition power dependence of visible transmittance and refractive index of room temperature-deposited ZnO:Al thin films by RF magnetron sputtering has been studied. All films exhibited high visible transmittance and near-complete UV absorption. The refractive index of the films decreased continuously with an increase in the RF power at all photon energies in the visible and near-IR region, which has been partially attributed to the decreased packing density of the films. For each film, the refractive index exhibited strong frequency dispersion in the weak-absorption region. The origin of optical dispersion at different RF power has been discussed in the light of a single-oscillator model.

Mohanty, Bhaskar Chandra; Yeon, Deuk Ho; Yun, Jae Ho; Cho, Jun Sik; Cho, Yong Soo

2014-04-01

224

Optical extinction, refractive index, and multiple scattering for suspensions of interacting colloidal particles  

E-print Network

We provide a general microscopic theory of the scattering cross-section and of the refractive index for a system of interacting colloidal particles, exact at second order in the molecular polarizabilities. In particular: a) we show that the structural features of the suspension are encoded into the forward scattered field by multiple scattering effects, whose contribution is essential for the so-called "optical theorem" to hold in the presence of interactions; b) we investigate the role of radiation reaction on light extinction; c) we discuss our results in the framework of effective medium theories, presenting a general result for the effective refractive index valid, whatever the structural properties of the suspension, in the limit of particles much larger than the wavelength; d) by discussing strongly-interacting suspensions, we unravel subtle anomalous dispersion effects for the suspension refractive index.

Alberto Parola; Roberto Piazza; Vittorio Degiorgio

2014-07-21

225

High-refractive-index fluids for the next-generation ArF immersion lithography  

NASA Astrophysics Data System (ADS)

ArF immersion lithography using a high-refractive-index fluid (HIF) is considered to be a promising candidate for the 32nm node or below. At SPIE 2005 we introduced a new immersion fluid, JSR HIL-1, which has a refractive index and transmittance of 1.64 and >98%/mm (193.4nm, 23 °C), respectively. With HIL-1 immersion and a two beam interferometric exposure tool, hp32nm L/S imaging has been demonstrated. In this paper, we will report another novel immersion fluid, HIL-2, which has a transmittance of >99%/mm, which is almost as high as that of water, and a refractive index of 1.65 (193.4nm, 23 °C). Furthermore, an ArF laser irradiation study has shown that the degree of photodecomposition for both HIL-1 and HIL-2 is small enough for immersion lithography application. A "fluid puddle" defect study confirmed that HILs have less tendency to form immersion-specific photoresist defects and the refractive indices of HILs were found constant under laser irradiation. Batch-to-batch variation in refractive index during manufacture of HILs was not observed. By refining prism designs, hp30nm L/S patterns have also been successfully imaged with two interferometric exposure tools and HIL immersion.

Wang, Yong; Miyamatsu, Takashi; Furukawa, Taiichi; Yamada, Kinji; Tominaga, Tetsuo; Makita, Yutaka; Nakagawa, Hiroki; Nakamura, Atsushi; Shima, Motoyuki; Kusumoto, Shiro; Shimokawa, Tsutomu; Hieda, Katsuhiko

2006-03-01

226

Tunable Liquid Gradient Refractive Index (L-GRIN) lens with two degrees of freedom.  

PubMed

We report a tunable optofluidic microlens configuration named the Liquid Gradient Refractive Index (L-GRIN) lens for focusing light within a microfluidic device. The focusing of light was achieved through the gradient refractive index (GRIN) within the liquid medium, rather than via curved refractive lens surfaces. The diffusion of solute (CaCl(2)) between side-by-side co-injected microfluidic laminar flows was utilized to establish a hyperbolic secant (HS) refractive index profile to focus light. Tailoring the refractive index profile by adjusting the flow conditions enables not only tuning of the focal distance (translation mode), but also shifting of the output light direction (swing mode), a second degree of freedom that to our knowledge has yet to be accomplished for in-plane tunable microlenses. Advantages of the L-GRIN lens also include a low fluid consumption rate, competitive focusing performance, and high compatibility with existing microfluidic devices. This work provides a new strategy for developing integrative tunable microlenses for a variety of lab-on-a-chip applications. PMID:19568674

Mao, Xiaole; Lin, Sz-Chin Steven; Lapsley, Michael Ian; Shi, Jinjie; Juluri, Bala Krishna; Huang, Tony Jun

2009-07-21

227

Reflection-Based Fibre-Optic Refractive Index Sensor Using Surface Plasmon Resonance  

NASA Astrophysics Data System (ADS)

A reflection-based fibre-optic refractive index sensor using surface plasmon resonance (SPR) in a thin metal film sputtered on a bare core of a multimode optical fibre is presented. The sensing element of the SPR fibre-optic sensor is the core of a step-index optical fibre made of fused silica with a gold film double-sided sputtered on the whole core surface, including the core end face. Consequently, a terminated reflection-based sensing scheme to measure the refractive indices of liquids is realized. The sensing scheme uses a wavelength interrogation method and the refractive index of a liquid is sensed by measuring the position of the dip in the reflected spectral intensity distribution. As an example, the aqueous solutions of ethanol with refractive indices in a range from 1.333 to 1.363 are measured. In addition, the increase in the sensitivity of the SPR fibre-optic refractive index sensor with the decrease of the fibre sensing length is demonstrated.

Hlubina, P.; Kadulova, M.; Ciprian, D.; Sobota, J.

2014-08-01

228

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

NASA Technical Reports Server (NTRS)

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.

Khanna, R. K.; Zhao, Guizhi

1986-01-01

229

Refractive index sensors based on optical fiber hetero-core structures and Fabry-Pérot interferometers  

NASA Astrophysics Data System (ADS)

In this paper, several configurations of optical fiber refractive index sensors based on a hetero-core structure are presented. These sensors are made by splicing short lengths of several specialty fibers with different core and cladding diameters between two standard single-mode fibers. In addition, two fiber bragg gratings are inscribed in single-mode fiber at both sides of the specialty fibers in order to create an in-fiber Fabry-Perot interferometer and the behavior of the transmission spectra is analyzed. The sensitivities and spectral behavior of the sensors are obtained by immersion in solutions of different refractive index.

Bueno, A.; Caucheteur, C.; Kinet, D.; Mégret, P.

2013-05-01

230

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

PubMed

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

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

2014-01-01

231

Observation of asymmetric solitons in waveguide arrays with refractive index gradient  

E-print Network

We study light propagation in waveguide arrays made in Kerr nonlinear media with a transverse refractive index gradient, and we find that the presence of the refractive index gradient leads to the appearance of a number of new soliton families. The effective coupling between the solitons and the localized linear eigenmodes of the lattice induces a drastic asymmetry in the soliton shapes and the appearance of long tails at the soliton wings. Such unusual solitons are found to be completely stable under propagation, and we report their experimental observation in fs-laser written waveguide arrays with focusing Kerr nonlinearity.

Weimann, Steffen; Vysloukh, Victor A; Szameit, Alexander; Torner, Lluis

2014-01-01

232

Broadband and low loss high refractive index metamaterials in the microwave regime  

NASA Astrophysics Data System (ADS)

A broadband, low-loss, isotropic, high refractive index metamaterial comprising an array of close-packed cubic elements of cross-linked square metal plates is demonstrated in the microwave regime. The structuring of the cubic elements reduces the diamagnetic response exhibited by arrays of solid metal cubes, whilst maintaining the strongly enhanced permittivity arising from capacitative coupling between adjacent metal elements. The corresponding increase in refractive index can be tailored through appropriate structuring of the faces and/or spacing of the cubes.

Campbell, T.; Hibbins, A. P.; Sambles, J. R.; Hooper, I. R.

2013-03-01

233

Observation of asymmetric solitons in waveguide arrays with refractive index gradient.  

PubMed

We study light propagation in waveguide arrays made in Kerr nonlinear media with a transverse refractive index gradient, and we find that the presence of the refractive index gradient leads to the appearance of a number of new soliton families. The effective coupling between the solitons and the localized linear eigenmodes of the lattice induces a drastic asymmetry in the soliton shapes and the appearance of long tails at the soliton wings. Such unusual solitons are found to be completely stable under propagation, and we report their experimental observation in fs-laser written waveguide arrays with focusing Kerr nonlinearity. PMID:24978570

Weimann, Steffen; Kartashov, Yaroslav V; Vysloukh, Victor A; Szameit, Alexander; Torner, Lluis

2014-06-15

234

Design of fishnet metamaterials with broadband negative refractive index in the visible spectrum.  

PubMed

We propose a technique capable of designing fishnet metamaterials that have a negative refractive index (NRI) over a broad range in the visible and infrared. The technique relies on optimizing the shape and scale of the fishnet apertures as well as the depth of different layers of the composite. A metamaterial is obtained that exhibits an unbroken 552 nm bandwidth of NRI, covering the entire red and infrared regions. Moreover, two fishnet structures perforated with star-like holes are found to render refractive index negative in the yellow and green spectra. PMID:24979007

Zhou, Shiwei; Townsend, Scott; Xie, Yi Min; Huang, Xiaodong; Shen, Jianhu; Li, Qing

2014-04-15

235

Refractive micro-optical elements for surface plasmons: from classical to gradient index optics.  

PubMed

Controlling the propagation of surface plasmons along a metal-dielectric interface is a key feature for the development of surface plasmon based circuits. We have designed various two-dimensional refractive dielectric optical elements for surface plasmons (SP) and characterized their capacity to route SP, using near- or far-field techniques. We first present basic devices analogous to usual optical components and the associated challenges for SP optics. We then use a metamaterial approach to locally vary the refractive index and fabricate gradient index structures for SP circuitry. PMID:20940955

Devaux, Eloïse; Laluet, Jean-Yves; Stein, Benedikt; Genet, Cyriaque; Ebbesen, Thomas; Weeber, Jean-Claude; Dereux, Alain

2010-09-27

236

Process equipped with a sloped UV lamp for the fabrication of gradient-refractive-index lenses.  

PubMed

In this investigation, a method for the preparation of gradient-refractive-index (GRIN) lenses by UV-energy-controlled polymerization has been developed. A glass reaction tube equipped with a sloped UV lamp was designed. Methyl methacrylate and diphenyl sulfide were used as the reactive monomer and nonreactive dopant, respectively. Ciba IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-ketone) was used as the initiator. The effects of initiator concentration, the addition of acrylic polymers, and the preparation conditions on the optical characteristics of the GRIN lenses produced by this method were also investigated. Refractive index distributions and image transmission properties were estimated for all GRIN lenses prepared. PMID:19412283

Liu, Jui-Hsiang; Chiu, Yi-Hong

2009-05-01

237

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

SciTech Connect

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.

Maria, J.; Truong, T. T.; Yao, J.; Lee, T-W.; Nuzzo, R. G.; Leyffer, S.; Gray, S. K.; Rogers, J. A. (Center for Nanoscale Materials); ( MCS); (Univ. of Illinois); (Louisiana State Univ.)

2009-05-21

238

Nonlinear refractive index on multiwavelength generation through mismatch photonic crystal fibre from transmission wavelength  

NASA Astrophysics Data System (ADS)

This paper proposes a measurement of nonlinear refractive index in the course of multi wavelength technique. We have generated a multi wavelengths formation by utilising a photonic crystal fibre (PCF) which mismatches zero dispersion wavelength from transmission wavelength at 1550 nm. We provide an experimental set-up in generating the multi wavelength phenomenon. A fibre ring laser configuration consists of erbium doped fibre amplifier (EDFA) set up and arrangement of FBGs is described. Encouraging results obtained from the set up proves the relations of signals generated through FBGs and new wavelengths. These findings shows, multi wavelengths able to present valuable inputs in determination of nonlinear refractive index parameter.

Abdullah, Mohd Nizam; Shaari, Sahbudin; Ehsan, Abang Annuar; Menon, Susthitha; Zakaria, Osman; Marzuki, Nazri

2014-05-01

239

Density and refractive index of binary CH4, N2 and CO2 ice mixtures  

NASA Astrophysics Data System (ADS)

In this work we present the results of a series of laboratory experiments performed to obtain the density and the real part of the refractive index of binary mixtures of ices of astrophysical interest. Densities of CO2:CH4 mixtures obey the expected weighted mean and the other binary mixtures have densities up to 20% lower than expected. Refractive index for all the binary mixtures deviates up to 5% from the theoretical, obtaining higher values than expected for CO2:CH4 and lower values than predicted for CO2:N2 and CH4:N2.

Luna, R.; Satorre, M. Á.; Domingo, M.; Millán, C.; Santonja, C.

2012-09-01

240

Broadband focusing and collimation of water waves by zero refractive index  

PubMed Central

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

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

2014-01-01

241

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)

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.

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

242

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)

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

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

243

Effect of substrate index of refraction on the design of antireflection coatings  

NASA Astrophysics Data System (ADS)

Formulae to estimate the average percent reflectance (Rave) of a broadband antireflection (AR) coating as a function of the bandwidth (B), the overall thickness (C), the index of refraction of the last layer (L), and the difference between the indices of the high- and low-index layers (D) were reported in 1991. Various refinements of these formulae and other insights into the underlying behavior of such coating designs have been reported up until the present time. Dobrowolski, et al.6 and Tikhonravov, et al.7 have also added independent viewpoints to this subject over this period. In the previous studies, the effects of the index of refraction of the substrate have mostly been ignored and have appeared to be very minor. This study has investigated the influence of the substrate index on the Rave results. It has been found that there seem to be two classes of designs with respect to the effect of substrate index. In the class of "step down" AR designs, there is a significant effect, in the other class, there is no significant effect. Even in the step-down case, there is no effect of substrate index if any and all indices of refraction for the coating materials are available from that of the index of the substrate to the index of the media.

Willey, Ronald R.

2011-09-01

244

Constant Refractive Index Multi-Core Fiber Laser  

SciTech Connect

A scalable fiber laser approach is described based on phase-locking multiple gain cores in an antiguided structure. The waveguide is comprised of periodic sequences of gain- and no-gain-loaded segments having uniform index, within the cladding region. Initial experimental results are presented.

Beach, R J; Feit, M D; Brasure, L D; Payne, S A; Mead, R W; Hayden, J S; Krashkevich, D; Alunni, D A

2002-03-18

245

Index of refraction engineering in five-level dressed interacting ground states atoms  

NASA Astrophysics Data System (ADS)

We present a five-level atomic system in which the index of refraction of a probe laser can be enhanced or reduced below unity with vanishing absorption in the region between pairs of absorption and gain lines formed by dressing of the atoms with a control laser and rf/microwave fields. By weak incoherent pumping of the population into a single metastable state, one can create several narrow amplifying resonances. At frequencies between these gain lines and additional absorption lines, there exist regions of vanishing absorption but resonantly enhanced index of refraction. In Rb vapors with density N in units of cm-3, we predict an index of refraction up to n?1+1.2×10-14N for the D1 line, which is more than an order of magnitude larger than other proposals for index of refraction enhancement. Furthermore, the index can be readily reduced below 1 by simply changing the sign of the probe or rf field detunings. This enhancement is robust with respect to homogeneous and inhomogeneous broadening.

Sagona-Stophel, Steven A.; Weatherall, James Owen; Search, Christopher P.

2011-08-01

246

Index of refraction engineering in five-level dressed interacting ground states atoms.  

PubMed

We present a five-level atomic system in which the index of refraction of a probe laser can be enhanced or reduced below unity with vanishing absorption in the region between pairs of absorption and gain lines formed by dressing of the atoms with a control laser and rf/microwave fields. By weak incoherent pumping of the population into a single metastable state, one can create several narrow amplifying resonances. At frequencies between these gain lines and additional absorption lines, there exist regions of vanishing absorption but resonantly enhanced index of refraction. In Rb vapors with density N in units of cm(-3), we predict an index of refraction up to n??(1+1.2×10(-14)N) for the D1 line, which is more than an order of magnitude larger than other proposals for index of refraction enhancement. Furthermore, the index can be readily reduced below 1 by simply changing the sign of the probe or rf field detunings. This enhancement is robust with respect to homogeneous and inhomogeneous broadening. PMID:21847183

Sagona-Stophel, Steven A; Weatherall, James Owen; Search, Christopher P

2011-08-15

247

Fiber inline Michelson interferometer fabricated by CO2 laser irradiation for refractive index sensing  

NASA Astrophysics Data System (ADS)

A compact Michelson interferometer (MI) in a single-mode fiber (SMF) is successfully formed by CO2 laser irradiation to measure refractive index (RI) values. The fiber inline MI mainly consists of two parts: one is the waist region in fiber formed by CO2 laser irradiation and the other one is the fiber tip end facet with pure gold sputter coating. Based on the MI theory, the interference signal is generate between the core mode and the cladding mode excited by the core mode at the waist region. Reflective spectra at two different interference lengths of 5mm and 15mm are given and the calculated lengths based on theory are well verified. After the measurements of matching liquids with seven different refractive indices, the RI sensitivity of the MI sample is tested of -197.3+/-19.1nm/RIU (refractive index unit), which suggests well potential application in RI sensing.

Wu, Hongbin; Yuan, Lei; Zhao, Longjiang; Cao, Zhitao; Wang, Peng

2014-03-01

248

Active metamaterials: sign of refraction index and gain-assisted dispersion management  

E-print Network

We derive an approach to define the causal direction of the wavevector of modes in optical metamaterials, which in turn, determines signs of refractive index and impedance as a function of {\\it real and imaginary} parts of dielectric permittivity and magnetic permeability. We use the developed technique to demonstrate that the interplay between resonant response of constituents of metamaterials can be used to achieve efficient dispersion management. Finally we demonstrate broadband dispersion-less index and impedance matching in active nanowire-based negative index materials. Our work opens new practical applications of negative index composites for broadband lensing, imaging, and pulse-routing.

Alexander A. Govyadinov; Mikhail A. Noginov; Viktor A. Podolskiy

2007-04-27

249

Index of refraction and mechanical behavior of soda lime glass under shock and release wave propagations  

Microsoft Academic Search

This article reports a set of experiments designed to measure change in the refractive index of transparent material under both planar shock and release wave propagations. Information about both mechanical and optical properties of transparent material were obtained simultaneously through the measurement of particle velocity at or near the impact surface and the free surface velocity. Data thus obtained is

Dattatraya P. Dandekar

1998-01-01

250

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

E-print Network

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 100 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.

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

2007-01-01

251

Periodically loaded transmission line with effective negative refractive index and negative group velocity  

Microsoft Academic Search

We present the design and implementation of a periodically loaded transmission line, which simultaneously exhibits negative refractive index (NRI) and negative group delay (and, hence, negative group velocity). This is achieved by loading the transmission line in series with capacitors and RLC resonators and in shunt with inductors. We discuss the dispersion characteristics of such a medium and identify the

Omar F. Siddiqui; Mo Mojahedi; G. V. Eleftheriades

2003-01-01

252

Some antenna applications of negative-refractive-index transmission-line (NRI-TL) metamaterials  

Microsoft Academic Search

Metamaterials are artificial structures engineered to exhibit unusual electromagnetic properties. Metamaterials (MTM) that exhibit a simultaneously negative electric permittivity epsi and magnetic permeability mu, and thus a negative refractive index (NRI), have recently attracted considerable attention in the electromagnetic community. This has been motivated by the potential to create new microwave and antenna devices that exhibit superior characteristics compared to

G. V. Eleftheriades; M. A. Antoniades; F. Qureshi

2006-01-01

253

Selected Antenna Applications of Negative-Refractive-Index Transmission-Line (NRI-TL) Metamaterials  

Microsoft Academic Search

Metamaterialls (MM) that exhibit a simultaneously negative electric permittivity ? and magnetic permeability ? and thus a negtive refractive index (NRI), have recently attracted considerable attention inthe electromagnetics community. In this article we present a number of antenna applications using NRI-TL metamaterials. These include broadband phase-shifting lines that can produce either a positive or a negative phase shift while exhibiting

G. V. Eleftheriades; M. A. Antoniades; F. Qureshi

2006-01-01

254

Highly sensitive fiber Bragg grating refractive index sensors Wei Liang, Yanyi Huang,a  

E-print Network

Highly sensitive fiber Bragg grating refractive index sensors Wei Liang, Yanyi Huang,a Yong Xu We combine fiber Bragg grating FBG technology with a wet chemical etch-erosion procedure American Institute of Physics. DOI: 10.1063/1.1904716 Since the early 1990s, fiber Bragg grating FBG

Huang, Yanyi

255

Laser generated Ag and Ag-Au composite nanoparticles for refractive index sensor  

NASA Astrophysics Data System (ADS)

Localized surface plasmon resonance (LSPR) wavelength of metal nanoparticles (NPs) is highly sensitive to size, shape and the surrounding medium. Metal targets were laser ablated in liquid for preparation of spherical Ag and Ag@Au core-shell NP colloidal solution for refractive index sensing. The LSPR peak wavelength and broadening of the NPs were monitored in different refractive index liquid. Quasi-static Mie theory simulation results show that refractive index sensitivity of Ag, Ag-Au alloy and Ag@Au core-shell NPs increases nearly linearly with size and shell thickness. However, the increased broadening of the LSPR peak with size, alloy concentration and Au shell thickness restricts the sensing resolution of these NPs. Figure-of-merit (FOM) was calculated to optimize the size of Ag NPs, concentration of Ag-Au alloy NPs and Au shell thickness of Ag@Au core-shell NPs. The refractive index sensitivity (RIS) and FOM were optimum in the size range 20-40 nm for Ag NPs. Laser generated Ag@Au NPs of Au shell thickness in the range of 1-2 nm showed optimum FOM, where thin layer of Au coating can improve the stability of Ag NPs.

Navas, M. P.; Soni, R. K.

2014-09-01

256

Three-dimensional metamaterials with an ultra-high effective refractive index over broad bandwidth  

E-print Network

The authors introduce a general mechanism, based on electrostatic and magnetostatic considerations, for designing three-dimensional isotopic metamaterials that possess an enhanced refractive index over an extremely large frequency range. The mechanism allows nearly independent control of effective electric permittivity and magnetic permeability without the use of resonant elements.

Jonghwa Shin; Jung-Tsung Shen; Shanhui Fan

2008-04-14

257

Roles of wave impedance and refractive index in photonic crystals with magnetic and dielectric properties  

Microsoft Academic Search

We investigated the roles of wave impedance and refractive index in photonic crystals by means of analytical expressions for edges frequencies of a photonic bandgap (PBG) in a one-dimensional photonic crystal with magnetic and dielectric properties. The analytical expressions were derived when the optical thicknesses of layers are the same. The wave impedance governs the formation of PBG's and the

Chul-Sik Kee; Jae-Eun Kim; Hae Yong Park; H. Lim

1999-01-01

258

Light-induced refractive index changes in LiNbO 3 :Ti waveguides  

Microsoft Academic Search

Holographic measurements of light-induced refractive index changes in LiNbO3:Ti waveguides are reported. The results demonstrate that Fe2+ centers are stabilized against oxidation in the region of large Ti concentration near the surface thus increasing the sensitivity to optical damage considerably. This undesired effect may be largely abolished by additional in-diffusion of protons.

V. Gericke; P. Hertel; E. Krätzig; J. P. Nisius; R. Sommerfeldt

1987-01-01

259

Chiral metamaterials with negative refractive index based on four “U” split ring resonators  

SciTech Connect

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.

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

2010-08-23

260

Effective refractive index for determining ray propagation in an absorbing dielectric particle  

E-print Network

such that the planes of constant phase deviate from those of constant amplitude [13]. In this case, Snell's law (2009) 300­306 #12;Yang and Liou [14] introduced an effective refractive index and formulated Snell's law in such a manner that complex quantities are not required. However, the previous study was limited

Liou, K. N.

261

On the theory of the temperature dependence of the refractive index of homopolar crystals  

Microsoft Academic Search

The temperature dependence of the refractive index and the dielectric constant of homopolar semi-conductors with a diamond structure was derived within the framework of the Kramers-Heisenberg theory. The temperature dependence of the dispersion frequencies was determined by a method analogous to the procedure in the investigation of the temperature dependence of absorption curves. It is shown that this procedure permits

Emil Antoncík

1956-01-01

262

Thermal lens investigation of the temperature dependence of the refractive index of aqueous electrolyte solutions  

Microsoft Academic Search

Thermal lens measurements of different aqueous electrolyte solutions have been recorded over the temperature range ?10°C–25°C which show major shifts in the temperature of maximum refractive index for each solution. A theoretical investigation of the thermal lens signals with respect to the structure of water reveals that the origin of these observed changes is dependent upon the expansion coefficient and

Simon M Colcombe; Roger D Lowe; Richard D Snook

1997-01-01

263

Saharan dust absorption and refractive index from aircraft-based observations during SAMUM 2006  

Microsoft Academic Search

ABSTRACT During the Saharan Mineral Dust Experiment (SAMUM) conducted in summer 2006 in southeast Morocco, the complex refractive index of desert dust was determined from airborne measurements of particle size distributions and aerosol absorption coefficients at three different wavelengths in the blue (467 nm), green (530 nm) and red (660 nm) spectral regions. The vertical structure of the dust layers

Andreas Petzold; Katharina Rasp; Bernadett Weinzierl; Michael Esselborn; Thomas Hamburger; Andreas Dörnbrack; Konrad Kandler; Lothar Schütz; Peter Knippertz; Markus Fiebig; Aki Virkkula

2009-01-01

264

Saharan dust absorption and refractive index from aircraft-based observations during SAMUM 2006  

Microsoft Academic Search

During the Saharan Mineral Dust Experiment (SAMUM) conducted in summer 2006 in southeast Morocco, the complex refractive index of desert dust was determined from airborne measurements of particle size distributions and aerosol absorption coefficients at three different wavelengths in the blue (467 nm), green (530 nm) and red (660 nm) spectral regions. The vertical structure of the dust layers was

ANDREAS P ETZOLD; W E INZIERL; M ICHAEL ESSELBORN; T HOM; B URGER; KONRAD K ANDLER; P ETER K NIPPERTZ; M A RKUS; KI V IRKKULA; Deutsches Zentrum

2009-01-01

265

Optically Induced Refractive Index Changes in BaTiO3  

Microsoft Academic Search

The phenomenon of ``optical damage,'' that is, optically induced changes in the index of refraction, can be used as a form of holographic storage in transparent ferroelectric crystals. In this paper we describe a series of experiments which characterize the optical damage in ferroelectric BaTiO3. This is done by recording in a single crystal of the material a plane wave

R. L. Townsend; J. T. LaMacchia

1970-01-01

266

Photopolymerizable glasses incorporating high refractive index species and ionic liquid: A comparative study  

Microsoft Academic Search

Three different holographic photomaterials belonging to the class of photopolymerizable glasses have been synthesized using sol-gel techniques, and characterized with the purpose of a comparative study. Their behavior is analyzed in terms of achieved refractive index modulation, dark diffusion mechanism, diffraction efficiency and optical quality; in order to determine their suitability for different holographic applications.

A. V. Velasco; M. P. Hernández-Garay; M. L. Calvo; P. Cheben; F. Del Monte

2011-01-01

267

A simple interrogation technique for refractive index measurement using multimode interference structure  

Microsoft Academic Search

A simple interrogation technique for refractive index measurement is proposed, using a multimode interference-based fiber tip structure. The fiber probe is a section of a multimode fiber, spliced to a single-mode fiber and interrogated in reflection. The interrogation technique uses two fiber Bragg gratings as discrete optical sources; by means of relative intensity variation of the reflected signals, those sources

Susana Silva; O. Frazão; J. L. Santos; F. X. Malcata

2011-01-01

268

Interferometric determination of the refractive index of carbon dioxide in the ultraviolet region  

Microsoft Academic Search

We have measured by Fabry-Pérot interferometry the refractive index of carbon dioxide between 1807 and 2537 A and compared our results with those obtained by extrapolation of dispersion formulae proposed by other authors and those calculated from our dispersion formula. We propose a new dispersion formula which corroborates with the oscillator strength values found in the literature.

A. Bideau-Mehu; Y. Guern; R. Abjean; A. Johannin-Gilles

1973-01-01

269

Analytic evaluation of diffuse flux at a refractive index discontinuity in forward-biased scattering media  

Microsoft Academic Search

A simple analytic method of estimating the error involved in using an approximate boundary condition for diffuse radiation in two adjoining scattering media with differing refractive index is presented. The method is based on asymptotic planar fluxes and enables the error to be readily evaluated analytically without recourse to Monte Carlo simulation. The analysis is extended to multi-layer media, for

Adrian C. Selden

2011-01-01

270

Defocusing properties of Gaussian beams for measuring refractive index of thin transparent samples  

NASA Astrophysics Data System (ADS)

We show how the defocusing properties of Gaussian beams can be used to measure the refractive index of solutions in thin transparent samples (less than 2 mm). Additionally, it is possible to predict analytically the shape of the plot for the refractive index as a function of concentration in any range. Our theory is limited for substances whose refractive index increases with concentration. The thin sample is placed between the focusing lens and its back focal plane and the system is adjusted to best focusing conditions. As a result, changes of the refractive index of the sample cause variations of the size of the focused beam. To measure with high accuracy the size of the beam we use the homodyne knife-edge profilometer while profiling a calibrated holographic reflective grating. The recorded vertical heights of the grating provide statistical data for improving even more the accuracy of the measurements. We demonstrate that the sensitivity of the system is a function of the pitch of the grating allowing selecting the range of interest. We apply our method for glucose liquid solutions. We include analytical description of our method and experimental results.

Cervantes-L, Joel; Cywiak, Moisés; Olvera-R, Octavio; Morales, Arquímedes

2013-11-01

271

Polarization-based index of refraction and reflection angle estimation for remote sensing applications  

Microsoft Academic Search

A passive-polarization-based imaging system records the polarization state of light reflected by objects that are illuminated with an unpolarized and generally uncontrolled source. Such systems can be useful in many remote sensing applications including target detection, object segmentation, and material classification. We present a method to jointly estimate the complex index of refraction and the reflection angle (reflected zenith angle)

Vimal Thilak; David G. Voelz; Charles D. Creusere

2007-01-01

272

Refractive index maps and membrane dynamics of human red blood cells parasitized  

E-print Network

Refractive index maps and membrane dynamics of human red blood cells parasitized by Plasmodium to the host red blood cells (RBCs). To study these modifications, we investigate two intrinsic indicators for identifying, through cell membrane dynamics, pathological states that cause or accompany human diseases

Suresh, Subra

273

High-precision diode-laser-based temperature measurement for air refractive index compensation.  

PubMed

We present a laser-based system to measure the refractive index of air over a long path length. In optical distance measurements, it is essential to know the refractive index of air with high accuracy. Commonly, the refractive index of air is calculated from the properties of the ambient air using either Ciddor or Edlén equations, where the dominant uncertainty component is in most cases the air temperature. The method developed in this work utilizes direct absorption spectroscopy of oxygen to measure the average temperature of air and of water vapor to measure relative humidity. The method allows measurement of temperature and humidity over the same beam path as in optical distance measurement, providing spatially well-matching data. Indoor and outdoor measurements demonstrate the effectiveness of the method. In particular, we demonstrate an effective compensation of the refractive index of air in an interferometric length measurement at a time-variant and spatially nonhomogeneous temperature over a long time period. Further, we were able to demonstrate 7 mK RMS noise over a 67 m path length using a 120 s sample time. To our knowledge, this is the best temperature precision reported for a spectroscopic temperature measurement. PMID:22086025

Hieta, Tuomas; Merimaa, Mikko; Vainio, Markku; Seppä, Jeremias; Lassila, Antti

2011-11-01

274

High-precision diode-laser-based temperature measurement for air refractive index compensation  

SciTech Connect

We present a laser-based system to measure the refractive index of air over a long path length. In optical distance measurements, it is essential to know the refractive index of air with high accuracy. Commonly, the refractive index of air is calculated from the properties of the ambient air using either Ciddor or Edlen equations, where the dominant uncertainty component is in most cases the air temperature. The method developed in this work utilizes direct absorption spectroscopy of oxygen to measure the average temperature of air and of water vapor to measure relative humidity. The method allows measurement of temperature and humidity over the same beam path as in optical distance measurement, providing spatially well-matching data. Indoor and outdoor measurements demonstrate the effectiveness of the method. In particular, we demonstrate an effective compensation of the refractive index of air in an interferometric length measurement at a time-variant and spatially nonhomogeneous temperature over a long time period. Further, we were able to demonstrate 7 mK RMS noise over a 67 m path length using a 120 s sample time. To our knowledge, this is the best temperature precision reported for a spectroscopic temperature measurement.

Hieta, Tuomas; Merimaa, Mikko; Vainio, Markku; Seppae, Jeremias; Lassila, Antti

2011-11-01

275

Effect of Scintillometer Height on Structure Parameter of the Refractive Index of Air Measurements  

Microsoft Academic Search

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 (Cn2). Cn2 represents the turbulent strength of the atmosphere and describes the ability of the atmosphere to transport heat and humidity. The main objective of this study was to evaluate the

P. H. Gowda; T. A. Howell; O. Hartogensis; S. Basu; B. R. Scanlon

2009-01-01

276

Visualizations of Light-induced Refractive Index Changes in Photorefractive Crystals Employing Digital Holography  

Microsoft Academic Search

We propose a novel approach to visualize the light-induced refractive index changes in photorefractive crystals employing digital holography. The holograms formed in a Mach-Zehnder interferometer are recorded by a two-dimensional CCD camera. From these holograms, the phase differences, which contain the information of the index changes in photorefractive crystals, are determined by utilizing digital holographic interferometry. Then the two-dimensional visualizations

Jian-Lin Zhao; Peng Zhang; Jian-Bo Zhou; De-Xing Yang; Dong-Sheng Yang; En-Pu Li

2003-01-01

277

Refractive index changes in proton exchange LiNbO 3 by ion implantation  

NASA Astrophysics Data System (ADS)

Ion implantation has been used to change the refractive index profile of proton exchanged LiNbO 3. Details of the index profile were determined by dark mode analysis. Changes induced by electronic and nuclear processes on x-cut crystals were separated. Comparisons are made with ion implantation profiles in pure LiNbO 3. Effects of thermal annealing to 150°C were recorded.

Glavas, E.; Townsend, P. D.; Foad, M. A.

1990-02-01

278

High-refractive-index gratings for spectroscopic and laser applications  

NASA Astrophysics Data System (ADS)

Fabrication of high performance gratings may significantly benefit from the use of high index materials such as Ta2O5, TiO 2 or Al2O3. However, these materials can typically not be patterned with the required quality by common etching processes. To overcome this limitation we developed novel grating fabrication technologies based on a combination of conventional lithography with Atomic-Layer-Deposition. For that the basic structure of the grating is first realized in a fused-silica substrate or a SiO2-layer. This template is then functionalized by an ALD-coating in a specific pre-defined manner. The new approach opens up a huge variety of new options for the realization of gratings whose fabrication would otherwise not be possible.

Zeitner, Uwe D.; Fuchs, Frank; Kley, E.-Bernhard; Tünnermann, Andreas

2014-02-01

279

The role of macromolecular crowding in the evolution of lens crystallins with high molecular refractive index  

PubMed Central

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 ? crystallins in vertebrates and S crystallins in cephalopods. 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 ? 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 crystalline 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 ? crystallins and S crystallins. PMID:21566271

Zhao, Huaying; Magone, M. Teresa; Schuck, Peter

2011-01-01

280

Evanescent field fiber Bragg grating sensors for index of refraction sensing with applications to structural health monitoring  

Microsoft Academic Search

Fiber Bragg grating sensing is a relatively mature fiber optic sensor technology currently being used in structural health monitoring systems. Therefore, there are significant benefits to using this technology as a platform for other sensing modalities. In this work, a side polished fiber Bragg sensor is described for sensing refractive index changes. The effective refractive index of a fiber Bragg

C.-F. Chan; G. A. Ferrier; D. J. Thomson; T. Coroy; P. Lefebvre; A. Vincelette

2006-01-01

281

Acoustic far-field focusing effect for two-dimensional graded negative refractive-index sonic crystals  

Microsoft Academic Search

Focusing effect is experimentally observed for acoustic plane wave normally incident onto a two-dimensional sonic crystal with gradient negative refractive index. The gradual refractive-index is achieved by gradual modification of the lattice spacing both along the transverse and longitudinal directions. It is found that the focal length is controllable by modulation of the lattice spacing. The experiment results are in

Shasha Peng; Zhaojian He; Han Jia; Anqi Zhang; Chunyin Qiu; Manzhu Ke; Zhengyou Liu

2010-01-01

282

Lidar determination of altitude profile of the refraction index in electro-optical monitoring of the Earths atmosphere  

E-print Network

Lidar determination of altitude profile of the refraction index in electro-optical monitoring reserved. Keywords: Electro-optical lidar; Electro-optical Kerr effect; Refraction index; Statistically by the lidar tech- nique has been gaining acceptance in the recent years [16­21]. Aerosole lidar measurements

283

A CCD based approach to size and complex refractive index determination of absorbing droplet using rainbow scattering  

NASA Astrophysics Data System (ADS)

A novel method for measuring droplet size and complex refractive index simultaneously using a CCD camera by rainbow detecting is proposed. A new mathematic model for rainbow pattern of absorbing droplet is built. Based on this model, a series of new formulas to measure droplet imaginary part of refractive index are derived. Then a new method for simultaneously measure droplet size and the complex refractive index is presented, which is verified by simulation experiments under different conditions. The experiment is performed to measure water with different dye concentrations. To avoid the effect of non-sphericity on refractive index detecting, a long and stable water cylinder instead of droplet is measured. Both the diameter and the complex refractive index of the liquid cylinder are detected by measuring the scattering rainbow light which is received by a linear CCD camera placed in the focus of the lens system. The result shows a satisfactory agreement with the theoretical analysis.

Pan, Qi

2013-12-01

284

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

PubMed

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

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

2009-08-01

285

Non-magnetic nano-composites for optical and infrared negative refraction index media  

E-print Network

We develop an approach to use nanostructured plasmonic materials as a non-magnetic negative-refractive index system at optical and near-infrared frequencies. In contrast to conventional negative refraction materials, our design does not require periodicity and thus is highly tolerant to fabrication defects. Moreover, since the proposed materials are intrinsically non-magnetic, their performance is not limited to proximity of a resonance so that the resulting structure has relatively low loss. We develop the analytical description of the relevant electromagnetic phenomena and justify our analytic results via numerical solutions of Maxwell equations.

Robyn Wangberg; Justin Elser; Evgenii E. Narimanov; Viktor A. Podolskiy

2005-06-27

286

High performance low refractive index materials for photonics I: preliminary characterization  

NASA Astrophysics Data System (ADS)

The series of inorganic-organic hybrid materials were prepared from silane precursors by the sol-gel process. The resulted perfluorinated organosilicate liquid oligomers were applied on glass substrates and cured by heat yielding hard, clear and well adhering films. The films porosity, water contact angle, refractive index, and absorption in UV-Vis and IR were measured to characterize optical and physicochemical properties of the prepared films. The perfluorinated organosilicate films exhibited excellent optical transparency, low refractive indices, low porosity as well as non-wetting, hydrophobic behavior.

Wojcik, Anna B.; John, ?ukasz; Szafert, S?awomir

2012-02-01

287

High performance low refractive index materials for photonics I: preliminary characterization  

NASA Astrophysics Data System (ADS)

The series of inorganic-organic hybrid materials were prepared from silane precursors by the sol-gel process. The resulted perfluorinated organosilicate liquid oligomers were applied on glass substrates and cured by heat yielding hard, clear and well adhering films. The films porosity, water contact angle, refractive index, and absorption in UV-Vis and IR were measured to characterize optical and physicochemical properties of the prepared films. The perfluorinated organosilicate films exhibited excellent optical transparency, low refractive indices, low porosity as well as non-wetting, hydrophobic behavior.

Wojcik, Anna B.; John, ?ukasz; Szafert, S?awomir

2011-09-01

288

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

NASA Astrophysics Data System (ADS)

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.

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

2011-07-01

289

Invertebrate superposition eyes-structures that behave like metamaterial with negative refractive index  

NASA Astrophysics Data System (ADS)

The superposition eyes of lobsters and moths are described with the geometrical optics for a refractive surface between two media, where the refractive index of the image space is negative. Consequently, the eye power and the object focal length are negative, whereas the image focal length is positive. The F-number is also negative, but the sign is irrelevant for calculations of the light sensitivity, because that depends on F2. The angular magnifications necessary for perfect focusing calculated for the superposition eyes of dung beetles diverge from measured values, and therefore the focus is distributed.

Stavenga, D. G.

2006-08-01

290

Propagation of hypergeometric laser beams in a medium with a parabolic refractive index  

NASA Astrophysics Data System (ADS)

An expression to describe the complex amplitude of a family of paraxial hypergeometric laser beams propagating in a parabolic-index fiber is proposed. A particular case of a Gaussian optical vortex propagating in a parabolic-index fiber is studied. Under definite parameters, the Gaussian optical vortices become the modes of the medium. This is a new family of paraxial modes derived for the parabolic-index medium. A wide class of solutions of nonparaxial Helmholtz equations that describe modes in a parabolic refractive index medium is derived in the cylindrical coordinate system. As the solutions derived are proportional to Kummer’s functions, only those of them which are coincident with the nonparaxial Laguerre-Gaussian modes possess a finite energy, meaning that they are physically implementable. A definite length of the graded-index fiber is treated as a parabolic lens, and expressions for the numerical aperture and the focal spot size are deduced. An explicit expression for the radii of the rings of a binary lens approximating a parabolic-index lens is derived. Finite-difference time-domain simulation has shown that using a binary parabolic-index microlens with a refractive index of 1.5, a linearly polarized Gaussian beam can be focused into an elliptic focal spot which is almost devoid of side-lobes and has a smaller full width at half maximum diameter of 0.45 of the incident wavelength.

Kotlyar, V. V.; Kovalev, A. A.; Nalimov, A. G.

2013-12-01

291

Characterization of fluids and fluid-fluid interaction by fiber optic refractive index sensor measurements  

NASA Astrophysics Data System (ADS)

A fiber optic refractive index sensor is tested for continuous monitoring of fluid-fluid and fluid-gas interactions within the frame of laboratory investigations of CO2 storage, monitoring and safety technology research (COSMOS project, "Geotechnologien" program). The sensor bases on a Fabry-Perot white light interferometer technique, where the refractive index (RI) of the solution under investigation is measured by variation of the liquid-filled Fabry-Perot optical cavity length. Such sensor system is typically used for measuring and controlling oil composition and also fluid quality. The aim of this study is to test the application of the fiber optic refractive index sensor for monitoring the CO2 dissolution in formation fluids (brine, oil, gas) of CO2 storage sites. Monitoring and knowledge of quantity and especially rate of CO2 dissolution in the formation fluid is important for any assessment of long-term risks of CO2 storage sites. It is also a prerequisite for any precise reservoir modelling. As a first step we performed laboratory experiments in standard autoclaves on a variety of different fluids and fluid mixtures (technical alcohols, pure water, CO2, synthetic brines, natural formation brine from the Ketzin test site). The RI measurements are partly combined with default electrical conductivity and sonic velocity measurements. The fiber optic refractive index sensor system allows for RI measurements within the range 1.0000 to 1.7000 RI with a resolution of approximately 0.0001 RI. For simple binary fluid mixtures first results indicate linear relationships between refractive indices and fluid composition. Within the pressure range investigated (up to 60 bar) the data suggest only minor changes of RI with pressure. Further, planned experiments will focus on the determination of i) the temperature dependency of RI, ii) the combined effects of pressure and temperature on RI, and finally iii) the kinetics of CO2 dissolution in realistic formation fluids.

Schmidt-Hattenberger, C.; Weiner, M.; Liebscher, A.; Spangenberg, E.

2009-04-01

292

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

PubMed

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

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

2013-06-28

293

Polarization-dependent refractometer for discrimination of temperature and ambient refractive index.  

PubMed

Transmission characteristics of polarization-dependent refractometer based on a surface long-period grating (SLPG) inscribed in a D-shaped photonic crystal fiber (PCF) are investigated. The birefringence of SLPG produces the separation of transmission spectra for TE and TM polarization modes. We also measure the sensitivities of PCF-based SLPG to temperature and external refractive index change depending on the input polarization states. The SLPG-based sensor exhibits different temperature and ambient index sensitivities corresponding to TE and TM polarization modes. Therefore, the SLPG inscribed in D-shaped PCFs can effectively discriminate temperature and ambient index sensitivities. PMID:22660034

Kim, H-J; Kwon, O-J; Lee, S B; Han, Y-G

2012-06-01

294

Magnifying absolute instruments for optically homogeneous regions  

NASA Astrophysics Data System (ADS)

We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

Tyc, Tomáš

2011-09-01

295

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

NASA Astrophysics Data System (ADS)

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 ?/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.

Wahba, H. H.

2014-10-01

296

High-refractive index particles in counter-propagating optical tweezers - manipulation and forces  

NASA Astrophysics Data System (ADS)

With a tightly focused single laser beam, also called optical tweezers, particles of a few nanometers up to several micrometers in size can be trapped and manipulated in 3D. The size, shape and refractive index of such colloidal particles are of influence on the optical forces exerted on them in the trap. A higher refractive-index difference between a particle and the surrounding medium will increase the forces. The destabilizing scattering force, however, pushing the particle in the direction of the beam, increases more than the gradient force, directed towards the focus. As a consequence, particles with a certain refractive index cannot be trapped in a single-beam gradient trap, and a limit is set to the force that can be exerted. We developed an experimental setup with two opposing high-numerical objectives. By splitting the laser beam, we created counter-propagating tweezers in which the scattering forces were canceled in the axial direction and high-refractive index and metallic particles could also be trapped. With the use of a separate laser beam combined with a quadrant photodiode, accurate position detection on a trapped particle in the counter-propagating tweezers is possible. We used this to determine trap stiffnesses, and show, with measurements and calculations, an enhancement in trap stiffness of at least 3 times for high-index 1.1-micrometer-diameter titania particles as compared to 1.4-micrometer-diameter silica particles under the same conditions. The ability to exert higher forces with lower laser power finds application in biophysical experiments, where laser damage and heating play a role. The manipulation of high-index and metallic particles also has applications in materials and colloid science, for example to incorporate high-index defects in colloidal photonic crystals. We demonstrate the patterning of high-index particles onto a glass substrate. The sample cell was mounted on a high-accuracy piezo stage combined with a long-range stage with motorized actuators. Because we used image analysis of the patterned structure to accurately find back the starting position and compensate for drift of the sample, we could move far away from the patterning region. This enabled us to select particles from a separate reservoir of a mixture of particles, and, one-by-one, position them at chosen locations. By time-sharing the laser beam using acousto-optic deflectors, we created multiple counter-propagating tweezers. We trapped an array of high-refractive index particles, and were able to move those particles individually. We used such a dynamic array of counter-propagating tweezers to create line-optical tweezers in which we trapped semi-conducting high-refractive index nanorods in three dimensions. We demonstrate full 3D translational and in-plane rotational control over the rods, which could not be held in single-beam line-tweezers. The configuration of two opposing objectives was also used for simultaneous trapping with one objective and confocal imaging of the fluorescently labeled particles using the other objective. By trapping particles with a refractive index contrast in a dispersion of index-matched particles, crystallization could be induced, which was imaged in three dimensions using confocal microscopy.

van der Horst, Astrid

2006-09-01

297

Methods to calibrate and scale axial distances in confocal microscopy as a function of refractive index  

E-print Network

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 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 point-spread-function of a point-scanning confocal microscope and showed that an index-matched, micron-sized spherical object is still significantly elongated due to this PSF, which confirms that single micron-sized spheres are not well suited to determine accurate axial calibration nor axial scaling.

Thijs Herman Besseling; Jissy Jose; Alfons van Blaaderen

2014-04-15

298

A novel acousto-optic modulation-deflection mechanism using refractive index grating as graded index beam router  

NASA Astrophysics Data System (ADS)

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.

Jangjoo, Alireza; Reza Baezzat, Mohammad; Razavizadeh, Ahmad

2014-03-01

299

Determination of the size, concentration, and refractive index of silica nanoparticles from turbidity spectra.  

PubMed

The size and concentration of silica cores determine the size and concentration of silica/gold nanoshells in final preparations. Until now, the concentration of silica/gold nanoshells with Stober's silica core has been evaluated through the material balance assumption. Here, we describe a method for simultaneous determination of the average size and concentration of silica nanospheres from turbidity spectra measured within the 400-600 nm spectral band. As the refractive index of silica nanoparticles is the key input parameter for optical determination of their concentration, we propose an optical method and provide experimental data on a direct determination of the refractive index of silica particles n = 1.475 +/- 0.005. Finally, we exemplify our method by determining the particle size and concentration for 10 samples and compare the results with transmission electron microscopy (TEM), atomic force microscopy (AFM), and dynamic light scattering data. PMID:18590302

Khlebtsov, Boris N; Khanadeev, Vitaly A; Khlebtsov, Nikolai G

2008-08-19

300

Hollow fiber taper with a silver micro-sphere used as refractive index sensor  

NASA Astrophysics Data System (ADS)

We have experimentally studied the plasmon resonance phenomenon of a silver micro-sphere with a diameter of 2.3 ?m in taper-shaped air cavity of a hollow fiber taper. To take insight into the plasmon resonance phenomenon, we move the micro-sphere along the fiber and observe the significant shift of the resonance peak. To explore this configuration as a sensor, we analyze the reflected optical spectrum changes as a function of the external refractive index by finite difference time domain method. The results show that this device can be used for a bio-chemical sensor to monitor the refractive index around it from 1.6 to 2.0. The further study supports that the variation was much more significantly for using the S polarized light as the incident source than P polarized light.

Li, Jin; Li, Hanyang; Zhao, Yong; Hu, Haifeng; Wang, Qi

2014-05-01

301

Exciton effects in the index of refraction of multiple quantum wells and superlattices  

NASA Technical Reports Server (NTRS)

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.

Kahen, K. B.; Leburton, J. P.

1986-01-01

302

Sustainable UV-curable low refractive index resins with novel polymers for polymer cladding materials  

NASA Astrophysics Data System (ADS)

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.

Tokoro, Hiroki; Ishikawa, Takako; Koike, Nobuyuki; Yamashina, Yohzoh

2014-03-01

303

Large refractive index modulation tilted holographic planar structured grating based on dichromated gelatin  

NASA Astrophysics Data System (ADS)

A new type grating, tilted holographic planar structured dichromated gelatin (DCG) grating with large refractive index modulation, is presented in this paper. The grating is inscribed by superposing two coherent laser beams from the front and the thin side surfaces, respectively. The relationship between the tilted angle and the three types of coupling modes is analyzed when coupling with fiber. Besides, the couple mode theory and experimental investigation are applied on major characteristics analysis of the radiation mode DCG grating of tilted angle 45°. Due to the tilted planar structured grating has large refractive index modulation, it not only offers convenience for connecting (or integrating) with other fiber or waveguide-based devices, but also provide some special characteristics such as low wavelength selectivity (which is required for some applications such as multiple spectrum biomedical imaging). Therefore, this unique grating device has a wide application in optical fields such as for the waveguide-based, parallel, multiple spectrum imaging system.

Zheng, Jihong; Yin, Shizhuo; Liu, Zhiwen; Yao, Jimmy; Kim, Jae Hun; Yang, Chia-En

2009-05-01

304

The refractive index and electronic gap of water and ice increase with increasing pressure  

E-print Network

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, e.g. 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 to 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 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 behavior.

Pan, Ding; Galli, Giulia

2014-01-01

305

Temperature-dependent Sellmeier equation for the refractive index of stoichiometric lithium tantalate.  

PubMed

We present a temperature-dependent Sellmeier equation for the refractive index of stoichiometric LiTaO3. The extraordinary refractive index, for the range 0.39-4.1 microm and for temperatures of 30-200 degrees C, are based on previously published data [Jpn. J. Appl. Phys. 41, 465 (2002)] and on measured data derived from quasi-phase-matched (QPM) resonances. We used the new Sellmeier coefficients that we obtained to calculate the QPM wavelengths for an optical parametric oscillator (OPO) based on periodically poled stoichiometric LiTaO3 pumped at 1064 nm. The measured wavelengths of the OPO were in good agreement with our predictions. PMID:12656329

Bruner, Ariel; Eger, David; Oron, Moshe B; Blau, Pinhas; Katz, Moti; Ruschin, Shlomo

2003-02-01

306

Influence of the refractive index on EGFP fluorescence lifetimes in mixtures of water and glycerol  

NASA Astrophysics Data System (ADS)

As a precursor to applying fluorescence lifetime imaging (FLIM) to studies of intercellular communication in molecular immunology, we have investigated the fluorescence lifetime of enhanced green fluorescent protein (EGFP) in mixtures of water and glycerol using time-correlated single photon counting (TCSPC). We find that the EGFP lifetime decreases with increasing glycerol content. This is accounted for quantitatively by the refractive index dependence of the fluorescence lifetime as predicted by the Strickler Berg formula which relates the fluorescence lifetime to the absorption spectrum. The solvent viscosity has no influence on the fluorescence lifetime. We also discuss the refractive index dependence of the GFP fluorescence lifetime in more complex systems. The findings are particularly relevant for the interpretation of FLIM of GFP expressed in environments such as bacteria and cells.

Suhling, Klaus; Davis, Daniel M.; Petrasek, Zdenek; Siegel, Jan; Phillips, David

2001-07-01

307

Refractive-index-matched hydrogel materials for modeling flow-structure interactions  

E-print Network

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.

Margaret L. Byron; Evan A. Variano

2012-12-04

308

Refractive-index-matched hydrogel materials for modeling flow-structure interactions  

E-print Network

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.

Byron, Margaret L

2012-01-01

309

Properties of material in the submillimeter wave region (instrumentation and measurement of index of refraction)  

NASA Technical Reports Server (NTRS)

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.

Lally, J.; Meister, R.

1983-01-01

310

Metal nanoparticles–silica composites: Z-scan determination of non-linear refractive index  

Microsoft Academic Search

Metal quantum-dot composite glasses can exhibit an enhanced optical Kerr susceptibility, ?(3), whose real part is related to the n2I coefficient of the intensity-dependent refractive index. We used the Z-scan technique for measuring the n2I’s of micrometric composites films formed by copper with nanometer sized particles embedded in silica glass by means of radiofrequency magnetron sputtering technique, followed by thermal

R. Polloni; B. F. Scremin; P. Calvelli; E. Cattaruzza; G. Battaglin; G. Mattei

2003-01-01

311

Thin-film thickness profile and its refractive index measurements by dispersive white-light interferometry  

Microsoft Academic Search

As an extension of the authors' previous report of Ref 1, we describe an improved version of dispersive white-light interferometry that enables us to measure the tomographical thickness profile of a thin-film layer through Fourier-transform analysis of spectrally-resolved interference signals. The group refractive index can also be determined without prior knowledge of the geometrical thickness of the film layer. Owing

Young-Sik Ghim; Seung-Woo Kim

2006-01-01

312

Metamaterials with negative permeability and negative refractive index: experiments and simulations  

Microsoft Academic Search

We report the transmission characteristics of split-ring resonator and left-handed metamaterials (LHM) in the microwave frequency regime. A left-handed transmission band is observed at the frequencies where both dielectric permittivity and magnetic permeability are negative. The reflection characteristics of ordered and disordered LHMs are studied. The two-dimensional LHM structure is verified to have a negative refractive index. We employed three

Ekmel Ozbay; Kaan Guven; Koray Aydin

2007-01-01

313

Multidimensional ion-pair HPLC for the purification of aminoglycoside antibiotics with refractive index detection  

Microsoft Academic Search

Summary  Gradient chromatographic conditions with refractive index detection are defined for the ion-pair separation of the non-UV-absorbing\\u000a aminoglycoside antibiotics. The method was applied with an off-line ion-pair prepurification step to the separation and characterization\\u000a of unknown aminoglycoside starting from filtered broths. An on-line prepurification process has also be designed.

D. Samain; P. Dupin; P. Delrieu; G. Inchauspe

1987-01-01

314

High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition  

SciTech Connect

A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs.

Brusasco, R.M.

1989-01-01

315

Aluminum-jointed silicon dioxide octagon nanohelix array with desired complex refractive index.  

PubMed

In this Letter, glancing angle deposition is used to form an aluminum-jointed silicon dioxide octagon nanohelix array as a 3D nanostructured thin film. As a sculptured metal-dielectric composite, the film exhibits a complex refractive index of near unity with a small imaginary part. This structured film is demonstrated as an efficient light absorber to absorb light in a broad band and over a wide range of angles for both polarization states. PMID:24978492

Jen, Yi-Jun; Chen, Chien-Chi; Jheng, Ci-Yao

2014-06-15

316

Evanescent gain for slow and stopped light in negative refractive index heterostructures  

Microsoft Academic Search

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

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

2011-01-01

317

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

Microsoft Academic Search

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

Francis Elek; George V. Eleftheriades

2005-01-01

318

SOLITONS: Nonlinear dynamics of optical pulses in fibres with a travelling refractive-index-change wave  

NASA Astrophysics Data System (ADS)

Dynamics of soliton-like wave packets in fibres with a travelling refractive-index-change wave is studied. It is shown that both a soliton-like propagation regime of a pulse and a self-compression regime in the region of normal group velocity dispersion are possible. It is also shown that in the case of a copropagating or counterpropagating pulse and optically inhomogeneous wave nonreciprocal effects appear.

Adamova, M. S.; Zolotovskii, Igor'O.; Sementsov, Dmitrii I.

2009-03-01

319

Refractive index and birefringence of InxGa1-xN films grown by MOCVD  

Microsoft Academic Search

The refractive index and birefringence of InxGa1-xN films grown on GaN layers were measured by prism coupling used in conjunction with multilayer optical waveguide analysis. Samples with x = 0.036, 0.049, 0.060, and 0.066 were examined at the separate wavelengths of 442, 457.9, 476.5, 488, 514.5, 532, and 632.8 nm. The In fraction x was determined by Rutherford backscattering spectroscopy.

N. A. Sanford; A. Munkholm; M. R. Krames; A. Shapiro; I. Levin; A. V. Davydov; S. Sayan; L. S. Wielunski; T. E. Madey

2005-01-01

320

Design of a refractive index sensor based on surface soliton waveguides  

NASA Astrophysics Data System (ADS)

The design of an innovative integrated sensor based on superficial soliton waveguides is presented. This configuration is called a RISSOR: refractive-index surface-soliton sensor. The hybrid structure combines traditional rib waveguides with a superficial one realized by a superficial photorefractive soliton. Simulations are performed using a BPM numerical code. The sensitivity of the proposed device is based on the solitonic evanescent wave as well as the coupling between the rib and solitonic waveguides.

Fiumara, T.; Fazio, E.

2013-12-01

321

Sagnac interferometric intensity-dependent refractive-index measurements of polymer optical fiber  

NASA Astrophysics Data System (ADS)

We have applied a new modified Sagnac interferometric technique to measure the real part of the intensity-dependent refractive index of a single-mode polymer optical fiber. For a 0.1% by weight squaraine dye in a poly(methyl methacrylate) core, Re[ chi (3)11 11] is 12(+/-7) \\times 10-13 cm 3/erg at lambda =1064 nm. We discuss the effect of these measurements on all-optical devices.

Garvey, D. W.; Li, Q.; Kuzyk, M. G.; Dirk, Carl W.; Martinez, S.

1996-01-01

322

Analytic evaluation of diffuse flux at a refractive index discontinuity in forward-biased scattering media  

E-print Network

A simple analytic method of estimating the error involved in using an approximate boundary condition for diffuse radiation in two adjoining scattering media with differing refractive index is presented. The method is based on asymptotic planar fluxes and enables the error to be readily evaluated analytically without recourse to Monte Carlo simulation. The analysis is extended to multi-layer media, for which the cumulative error can exceed 100% when an approximate boundary condition is used.

Selden, Adrian C

2011-01-01

323

Determining the refractive index of a {lambda}/4 thin film on a thick substrate from a transmittance measurement  

SciTech Connect

The refractive index is a key optical constant required by optical thin film designers. The coater-designer team must constantly verify the refractive indices of the non-absorbing optical thin films since the refractive index of a deposited material can vary by switching coating systems or operators as well as expected changes during the course of a coating run. A transmittance measurement on a spectrophotometer is an easy and accurate (usually to within {+-}0.5% spread) method of determining the refractive index. In one technique, the refractive index is obtained from visually curve-fitting a calculated (using a thin film design program and selecting the refractive index) transmittance spectrum to the measured transmittance spectrum. There are two other techniques which are discussed in this report: A quick, approximate method vs. the exact derivation. What the authors have not been able to find in the literature is the exact transmittance dependence as a function of the refractive indices (layers) through which the light passes and which accounts for the substrate back reflections. There are undocumented approximation methods as well as one in the literature by Cheremukhin and Rozhnox. Otherwise, most texts either derive the transmittances through optical multilayers or just the effect of back reflections on the transmittance for thick substrates. Without correcting for substrate back reflections, the derived refractive indices from the measured transmittances are in error by as much as 10%. In this work, the authors have utilized both an exact and an approximate method of determining the refractive index of the film. It is found that both the exact and approximate methods of determining the refractive index of thin optical coatings are within the measurement errors of commercially available spectrophotometers.

Chow, R.; Loomis, G.E.; Biltoft, P.

1993-06-01

324

Index of refraction and mechanical behavior of soda lime glass under shock and release wave propagations  

NASA Astrophysics Data System (ADS)

This article reports a set of experiments designed to measure change in the refractive index of transparent material under both planar shock and release wave propagations. Information about both mechanical and optical properties of transparent material were obtained simultaneously through the measurement of particle velocity at or near the impact surface and the free surface velocity. Data thus obtained is used to determine shock and release wave velocities and the Hugoniot elastic limit (HEL) of the material. Shock wave velocity in soda lime glass remains unchanged at 5.83±0.04 km/s, i.e., equal to the measured ultrasonic longitudinal wave velocity, when it is shock compressed to less than or equal to 4.3 GPa. The value of shock wave velocity begins to decline when the impact stress in the glass exceeds this value. The release wave velocity, however, remains equal to the measured ultrasonic longitudinal wave velocity to only 3 GPa, it begins to decline at higher stresses. The variation in the refractive index of the glass shows a cusp at 3.04-3.14 GPa. Additionally, up to and including the impact stress of 3.14 GPa, the refractive index after shock compression and release is within 1% of its ambient value, but at higher stresses it differs by larger percentage points. The HEL of the glass is determined to be 3.10±0.06 GPa although it lacks the classic well defined cusp in all the recorded wave profiles of soda lime glass.

Dandekar, Dattatraya P.

1998-12-01

325

Tunable fiber laser based on the refractive index characteristic of MMI effects  

NASA Astrophysics Data System (ADS)

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.

Ma, Lin; Qi, Yanhui; Kang, Zexin; Bai, Yunlong; Jian, Shuisheng

2014-04-01

326

Amplification of the index of refraction of aqueous immersion fluids with crown ethers: a progress report  

NASA Astrophysics Data System (ADS)

There is a current need for high refractive index (RI) materials that can be used in aqueous systems for improving 193 nm immersion photolighography. Although heavy metal salts such as Ca 2+ and Ba 2+ have the potential to substantially increase the RI of aqueous solutions, the water solubility of these salts with common anions is often too low to achieve concentrations that significantly increase the RI to the desired values. We have therefore investigated the use of crown ethers to enhance the solubility of these cations. Most of the crown ethers are soluble in water, environmentally benign and commercial and inexpensive materials. Details of the preliminary studies on the proposed model system are presented in this paper. 15-crown-5-ether and 12-crown-4-ether are liquids at room temperature and therefore can be used as neat liquids as immersion fluids without dilution in water. Saturation of crown ethers with inorganic salts do not lead to any increase of the refractive index due to the low solubility of those in such an apolar media. Thus, the use of inorganic salt as refractive index enhancement agent does not seem to be a desirable proposition in the present case. Instead, the use of crown ethers or their derivates can be alternative system since these compounds have properties, such as density, viscosity and boiling point, similar to aqueous media.

López-Gejo, Juan; Kunjappu, Joy T.; Turro, Nicholas J.; Conley, Will

2006-03-01

327

Indirect transitions of a signal interacting with a moving refractive index front  

NASA Astrophysics Data System (ADS)

The dynamic manipulation of light can be achieved by the interaction of a signal pulse propagating through or reflected from a refractive index front. Both the frequency and the wave vector of the signal are changed in this case, which is generally referred to as an indirect transition. We have developed a theory to describe such transitions in integrated photonic crystal waveguides. Through indirect transitions, the following effects can be envisaged: large frequency shifts and light stopping and order of magnitude pulse compression and broadening without center frequency shift. All effects can be potentially realized with a refractive index modulation as small as 0.001. For the experimental realization, we have used slow light photonic crystal waveguides in silicon. The refractive index front was obtained by free carriers generation with a switching pulse co-propagating with the signal in the same slow light waveguide. The group velocities of the signal and the front could be varied arbitrarily by choosing the right frequencies of the signal and switching pulses. The indirect transition was unambiguously demonstrated by considering two situations: a) the front overtaking the signal and b) the signal overtaking the front. In both cases, a blue shift of the signal frequency was observed. This blue shift can only be explained by the occurrence of the expected indirect transition and not by a direct transition without wave vector variation.

Castellanos Muñoz, Michel; Petrov, Alexander Y.; O'Faolain, Liam; Li, Juntao; Krauss, Thomas F.; Eich, Manfred

2014-05-01

328

Indirect transitions of a signal interacting with a moving refractive index front  

NASA Astrophysics Data System (ADS)

The dynamic manipulation of light can be achieved by the interaction of a signal pulse propagating through or reflected from a refractive index front. Both the frequency and the wave vector of the signal are changed in this case, which is generally referred to as an indirect transition. We have developed a theory to describe such transitions in integrated photonic crystal waveguides. Through indirect transitions, the following effects can be envisaged: large frequency shifts and light stopping and order of magnitude pulse compression and broadening without center frequency shift. All effects can be potentially realized with a refractive index modulation as small as 0.001. For the experimental realization, we have used slow light photonic crystal waveguides in silicon. The refractive index front was obtained by free carriers generation with a switching pulse co-propagating with the signal in the same slow light waveguide. The group velocities of the signal and the front could be varied arbitrarily by choosing the right frequencies of the signal and switching pulses. The indirect transition was unambiguously demonstrated by considering two situations: a) the front overtaking the signal and b) the signal overtaking the front. In both cases, a blue shift of the signal frequency was observed. This blue shift can only be explained by the occurrence of the expected indirect transition and not by a direct transition without wave vector variation.

Castellanos Muñoz, Michel; Petrov, Alexander Yu.; O'Faolain, Liam; Li, Juntao; Krauss, Thomas F.; Eich, Manfred

2014-09-01

329

Blood pH optrode based on evanescent waves and refractive index change  

NASA Astrophysics Data System (ADS)

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.

Hammarling, Krister; Hilborn, Jöns; Nilsson, Hans-Erik; Manuilskiy, Anatoliy

2014-02-01

330

Correction of stain variations in nuclear refractive index of clinical histology specimens  

NASA Astrophysics Data System (ADS)

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.

Uttam, Shikhar; Bista, Rajan K.; Hartman, Douglas J.; Brand, Randall E.; Liu, Yang

2011-11-01

331

3-D holographic refractive index measurement of continuously flowing cells in a microfluidic channel  

PubMed Central

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, RI 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 RI maps of the samples from the measured spectra. Using this method, we demonstrate label-free 3-D 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 3-D refractive index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, promises as a quantitative tool for stain-free characterization of large number of cells.

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

2014-01-01

332

Extremely high-accuracy correction of air refractive index using two-colour optical frequency combs  

PubMed Central

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

Wu, Guanhao; Takahashi, Mayumi; Arai, Kaoru; Inaba, Hajime; Minoshima, Kaoru

2013-01-01

333

Zoned near-zero refractive index fishnet lens antenna: Steering millimeter waves  

NASA Astrophysics Data System (ADS)

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 (?0 = 5.29 mm), the zoned fishnet metamaterial lens, designed to have a focal length FL = 9?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.

Pacheco-Peña, V.; Orazbayev, B.; Beaskoetxea, U.; Beruete, M.; Navarro-Cía, M.

2014-03-01

334

Quantum-interference effects on the index of refraction in an Er{sup 3+}-doped yttrium aluminum garnet crystal  

SciTech Connect

A four-level system is proposed to produce large index of refraction accompanied by vanishing absorption in the Er{sup 3+}-doped yttrium aluminum garnet crystal. It is found that the separation of the two absorption peaks and the maximum value of index of refraction with zero absorption can be adjusted by changing the coherent field and the incoherent pumping. It is shown that a higher index of refraction with zero absorption can be easily obtained when the coherent field is off resonance.

Zhang Huifang; Wu Jinhui; Su Xuemei [College of Physics, Jilin University, Changchun 130023 (China); Key Lab of Coherent Light, Atomic and Molecular Spectroscopy, Educational Ministry of China, Changchun (China); Gao Jinyue [CCAST (World Laboratory), P.O. Box 8730, Beijing 100080 (China); College of Physics, Jilin University, Changchun 130023 (China); Key Lab of Coherent Light, Atomic and Molecular Spectroscopy, Educational Ministry of China, Changchun (China)

2002-11-01

335

Theoretical expression for change of extraordinary refractive index in annealed proton exchanged LiNbO 3 optical waveguides  

NASA Astrophysics Data System (ADS)

A general expression for the change in extraordinary refractive index of the annealed proton exchanged LiNbO 3 waveguide has been deduced. The expression deduced explains the experimental results of decrease in change of extraordinary refractive index with annealing. The effect of annealing time has also been incorporated following Cao's model (Cao, Ramaswamy, Srivastava, J. Lightwave Technol. 10 (1992) 1302-1313). The concentration profile of protons in the annealed waveguide has been deduced theoretically, which is consistent with the previous results. The spontaneous polarization has been considered as the central mechanism for change in extraordinary refractive index due to proton exchange with annealing.

Singh, G. K.; Singh, A. P.; Sharma, V. K.; Kapoor, A.; Tripathi, K. N.

2002-04-01

336

The role of macromolecular crowding in the evolution of lens crystallins with high molecular refractive index  

NASA Astrophysics Data System (ADS)

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 ?-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 ?-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 ?-crystallins and S-crystallins.

Zhao, Huaying; Magone, M. Teresa; Schuck, Peter

2011-08-01

337

Refractive index and strain sensitivities of a long period fiber grating  

NASA Astrophysics Data System (ADS)

A long period fiber grating (LPFG) fabricated upon the all-solid photonic bandgap fiber by CO2 laser irradiation was investigated, and its resonance wavelength was at 1335.76 nm with a modulation depth of 15 dB and a 3-dB bandwidth of 2.6 nm. We studied its strain, temperature, and index sensor characteristics, the strain sensitivity of 0.992 pm/?? was obtained by using linear fit, and the relationship between the refractive index and wavelength obeyed the distribution of quadratic function. Also, we demonstrated its temperature response was relatively insensitive (21.51 pm/°).

Huang, Quandong; Yu, Yongqin; Ou, Zhilong; Chen, Xue; Wang, Jishun; Yan, Peiguang; Du, Chenlin

2014-03-01

338

Refractive index profiling of a few-mode fiber from fundamental mode excitation  

NASA Astrophysics Data System (ADS)

The fundamental mode of a small-core step-index few-mode fiber, originally designed for single-mode operation at 1310/1550 nm, was selectively excited at visible wavelengths from a single-mode fiber by adiabatically tapering the fusion splice. A two-dimensional refractive index profile of the few-mode fiber was reconstructed directly from measured guided mode intensity distribution and its spatial partial derivatives with a modified end-fire coupling method using a differential inverse calculation algorithm, which applies only for single-mode guiding.

Tsai, Wan-Shao; Chang, Che-Kai; Sheu, Fang-Wen; Wang, Yao-Hsuan; Chen, Sy-Hann

2014-07-01

339

All-optical on-chip sensor for high refractive index sensing in photonic crystals  

NASA Astrophysics Data System (ADS)

In this paper we demonstrate an optical sensor designed to detect material infiltrations with relatively high indices, based on a two-dimensional photonic crystal cavity structure. The locations and sizes of the holes surrounding a L3 cavity were modified to increase the Q factor to a value of 1500 with a high refractive index infilling of n= 1.5 . With precise design and simulation, we overcome the difficulty of low index contrast, and observe a very clear wavelength shift of 10.4 nm in simulation and 12.4 nm in experiment between water (n=1.33) and oil (n=1.45) samples at resonance.

Liu, Yazhao; Salemink, H. W. M.

2014-08-01

340

Refractive index gradient measurement across the thickness of a dielectric film by the prism coupling method  

SciTech Connect

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)

Sokolov, Viktor I; Panchenko, Vladislav Ya; Seminogov, V N [Institute of Laser and Information Technologies, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation)

2012-08-31

341

Radial distribution of the refractive index in light-focusing rods: determination using Interphako interference microscopy.  

PubMed

An interferometric technique for the determination of the radial distribution of the refractive index in lightfocusing plastic rods (LFR) has been developed using the shearing method of Interphako interference microscopy. We have derived mathematical expressions for the shape of interference fringes across the rod assuming the index distribution of LFR is described by n(r) n(=) (1 - ar(2) + br(4) + cr(6) + dr(2)) in which a, b, c, and d are distribution constants. The dsitribution constants were determined using a least-squares technique on a computer from the actual shape of fringes. Results for the representative cases are shown. PMID:20168633

Ohtsuka, Y; Shimizu, Y

1977-04-01

342

All-dielectric three-dimensional broadband Eaton lens with large refractive index range  

NASA Astrophysics Data System (ADS)

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 (1-6.32) 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 GHz-18 GHz).

Yin, Ming; Yong Tian, Xiao; Ling Wu, Ling; Chen Li, Di

2014-03-01

343

Continuously tuning effective refractive index based on thermally controllable magnetic metamaterials.  

PubMed

By employing a thermally active magnetic material, we theoretically design a kind of electromagnetic metamaterial with intrinsic magnetic response, termed magnetic metamaterial (MM). The retrieved effective electric permittivity ?(eff) and magnetic permeability ?(eff) exhibit a nearly continuous transition from double negative to double zero, and then to double positive by controlling the temperature, indicating a flexible tunability of the effective refractive index. The beam splitting, collimation, focusing, and total reflection are achieved at different typical temperatures. Most importantly, with the MM implemented under a gradient temperature, a gradient negative-zero-positive index metamaterial (NZPIM) can possibly be realized, thus providing a new platform to study wave features in NZPIM. PMID:25121838

Yu, Xinning; Chen, Huajin; Lin, Haixiao; Zhou, Jialin; Yu, Jingjing; Qian, Chunxiu; Liu, Shiyang

2014-08-15

344

Refractive Index of Light in the Quark-Gluon Plasma with the Hard-Thermal-Loop Perturbation Theory  

E-print Network

The electric permittivity and magnetic permeability for the quark-gluon plasma (QGP) is calculated within the hard-thermal-loop (HTL) perturbation theory. The refractive indices in the magnetizable and non-magnetizable plasmas are calculated. In a magnetizable plasma, there is a frequency pole $\\omega_{mp}$ in the magnetic permeability and the refractive index. The refractive index becomes negative in the range $\\omega\\in[k,\\omega_{mp}]$, where $k$ is the wave number, but no propagating modes are found. In a non-magnetizable plasma, the magnetic permeability and the refractive index are always positive. This marks the main distinction of a weakly coupled plasma from a strongly coupled one, where the negative refraction is shown to exist in a holographic theory.

Juan Liu; M. J. Luo; Qun Wang; Hao-jie Xu

2011-09-19

345

Color generation and refractive index sensing using diffraction from 2D silicon nanowire arrays.  

PubMed

Tunable structural color generation from vertical silicon nanowires arranged in different square lattices is demonstrated. The generated colors are adjustable using well-defined Bragg diffraction theory, and only depend on the lattice spacing and angles of incidence. Vivid colors spanning from bright red to blue are easily achieved. In keeping with this, a single square lattice of silicon nanowires is also able to produce different colors spanning the entire visible range. It is also shown that the 2D gratings also have a third grating direction when rotated 45 degrees. These simple and elegant solutions to color generation from silicon are used to demonstrate a cost-effective refractive index sensor. The sensor works by measuring color changes resulting from changes in the refractive index of the medium surrounding the nanowires using a trichromatic RGB decomposition. Moreover, the sensor produces linear responses in the trichromatic decomposition values versus the surrounding medium index. An index resolution of 10(-4) is achieved by performing basic image processing on the collected images, without the need for a laser or a spectrometer. Spectral analysis enables an increase in the index resolution of the sensor to a value of 10(-6) , with a sensitivity of 400 nm/RIU. PMID:23784866

Walia, Jaspreet; Dhindsa, Navneet; Khorasaninejad, Mohammadreza; Saini, Simarjeet Singh

2014-01-15

346

Zero Phase Delay in Negative-refractive-index Photonic Crystal Superlattices  

SciTech Connect

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.

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

347

The application of the interference microscopy for the refractive index determination of the cell wall and cytoplasm in plant cells.  

PubMed

Interference microscopy method has been used for measuring the refractive indices of cell wall and cytoplasm of two plant species: Funaria hygrometrica and Lemna trisulca. The refractive index of the cytoplasm was determined by measuring the centrifuged cells. The mean values obtained for different wavelengths lie in the range 1.41-1.42. PMID:634148

Gabry?, H

1978-03-01

348

Refractive index and Snell's Law for Dipolar-Exchange Spin-Waves in a Confined Planar Structure  

Microsoft Academic Search

We derived the analytical forms of refractive index and Snell law for dipolar-exchange spin waves of reflection and refraction at a magnetically heterogeneous interface in a geometrically confined planer structure composed of different magnetic thin films from a microscopic scattering approach. A novel behavior, the optical total reflection, was demonstrated for spin waves with a specific interface between Yttrium iron

Dae-Eun Jeong; Dong-Soo Han; Sangkook Choi; Sang-Koog Kim

2009-01-01

349

Refraction of electromagnetic energy for wave packets incident on a negative-index medium is always negative  

E-print Network

Refraction of electromagnetic energy for wave packets incident on a negative-index medium is always February 2004 We analyze refraction of electromagnetic wave packets on passing from an isotropic positive, since all physical sources of electromagnetic waves produce radiation fields of finite spatial

Sridhar, Srinivas

350

Effect of bleaching on color change and refractive index of dental composite resins.  

PubMed

This study investigated the effects of three bleaching agents (Whiteness Perfect, Whiteness Super, and Whiteness HP) on the color change and refractive index of three dental composites (Admira, Durafill VS, and Gradia Direct). Twenty disk-shaped specimens (10 x 2 mm) of each composite were prepared and divided into four subgroups (n=5). An unbleached group was used as a control, while the remaining specimens in the three subgroups were bleached with one of the bleaching agents respectively. Color change was assessed according to CIELAB color system and refractive indices were determined by phase modulated spectroscopic ellipsometry. Color differences between bleaching and baseline value (DeltaE) were less than 3.3 for all groups. However, bleaching with Whiteness HP led to noticeable color changes for Admira and Durafill VS. While this agent had no effect on the refractive indices of these composites, the other two agents containing carbamide peroxide increased their refractive indices. Therefore, results suggested that replacement of such composite restorations may be required after bleaching. PMID:18309619

Hubbezoglu, Ihsan; Akao?lu, Bari?; Dogan, Arife; Keskin, Selda; Bolayir, Giray; Ozçelik, Süleyman; Dogan, Orhan Murat

2008-01-01

351

Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization  

E-print Network

Dispersion engineering in silicon nitride (SiX NY ) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multi-cladding arrangement. Ultra-flat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during the fabrication of the SiX NY waveguides are a limitation for obtaining ultra-flat dispersion profiles. Single- and multi-cladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in both single-cladding waveguides and multi-cladding waveguides with small refractive index contrast (3 %). A flat dispersion profile with 3.2 ps/nm/km variation over 500 nm is obtained ...

Boggio, J M Chavez; Fremberg, T; Haynes, R; Roth, M M; Eisermann, R; Lisker, M; Zimmermann, L; Boehm, M

2014-01-01

352

Infrared Spectra, Index of Refraction, and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere  

NASA Technical Reports Server (NTRS)

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.

Moore, Marla; Ferrante, Robert; Moore, William; Hudson, Reggie

2010-01-01

353

Thickness and refractive index of DPPC and DPPE monolayers by multiple-beam interferometry.  

PubMed

The thickness and refractive index of 1,2-dipalmitoyl-sn-glycero-3-phosphatidyl choline (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) monolayers Langmuir--Blodgett (LB) deposited on mica were measured in dry air and bulk water using multiple-beam interferometry (MBI). Measurements of thickness using atomic force microscopy (AFM) of identical monolayers, and X-ray reflectivity (XRR) of the monolayers on quartz were taken for comparison. The measurement of the properties of solid-supported monolayers in dry air allows lipid optical properties to be determined free from solvent effects. The thickness and refractive index measured by MBI were 25.5?±?0.6 Å and 1.485?±?0.007 for DPPE monolayers, and 23.9?±?0.5 Å and 1.478?±?0.006 for DPPC monolayers in dry air. These thicknesses are consistent with the other techniques used in this work as well as other measurements in the literature. The refractive indices of solid-supported lipid monolayers have not been previously measured. The values are higher than previous measurements on black lipid films done by reflectometry, which is attributed to increased lipid packing density and the absence of hydrocarbon solvents. Applying water to the monolayers had no measurable effect on their properties, indicating that any change in hydration was below detection. PMID:24842403

Kienle, Daniel F; de Souza, João V; Watkins, Erik B; Kuhl, Tonya L

2014-07-01

354

Refractive Index Control of SiO2 Films by Pulsed Laser Deposition with Silicone Targets  

NASA Astrophysics Data System (ADS)

We fabricated layered structures of SiO2 films with different refractive indices by pulsed laser deposition with silicone targets. The refractive index of SiO2 films could be controlled by the deposition rate. Lowering of the deposition rate helped to make a dense film, showing higher refractive index. A 0.4-?m-thick SiO2 cladding film deposited at 0.1 nm/pulse was first formed on the entire surface of a Si wafer, and then a 1-?m-thick SiO2 core film was deposited at 0.05 nm/pulse in a line of 1 mm width on the sample. The deposited films were free of impurities such as H2O and carbon. Transparent, tightly layered structures were obtained. The layered structures could also be fabricated on a flexible substrate consisting of a 100-?m-thick polyester sheet. Both samples functioned as an optical waveguide for a 633-nm He-Ne laser. The single-mode propagations were observed as designed.

Okoshi, Masayuki; Kuramatsu, Masaaki; Inoue, Narumi

2002-09-01

355

Three-Dimensional Velocity Measurement Reconstruction for a Rod Bundle Array using Matched Refractive Index Particle Tracking Velocimetry  

E-print Network

geometry using a novel matched refractive index particle tracking velocimetry (PTV) technique over a 3D volume cross section of a prototypical nuclear fuel rod bundle. Velocimetry tracking will be performed in order to characterize the mechanics...

Reyes, Denny L

2013-08-09

356

A Fresnel reflection-based optical fiber sensor system for remote refractive index measurement using an OTDR  

NASA Astrophysics Data System (ADS)

In this paper, we propose a Fresnel reflection-based optical fiber sensor system for remote refractive index measurement using the optical time domain reflectometry technique as an interrogation method. The surrounding refractive index from a long distance away can be measured easily by using this sensor system, which operates based on testing the Fresnel reflection intensity from the fiber-sample interface. This system is a simple configuration, which is easy to handle. Experimental results showed that the range of this measurement could reach about 100.8 km, and the refractive index sensitivities were from 38.71 dB/RIU to 304.89 dB/RIU in the refractive index (RI) range from 1.3486 to 1.4525.

Yuan, Jianying; Zhao, Chunliu; Ye, Manping; Kang, Juan; Zhang, Zaixuan; Jin, Shangzhong

2014-03-01

357

Direct measurement of the complex refractive index in the extreme ultraviolet spectral region using diffraction from a nanosphere array  

E-print Network

fs pulses centered at 800 nm from a Ti:sapphire laser is focused using a concave dielectric mirror R diffraction image. The measurement of the refractive index of a medium in this spectral region is difficult

Steiner, Ullrich

358

Acoustic far-field focusing effect for two-dimensional graded negative refractive-index sonic crystals  

NASA Astrophysics Data System (ADS)

Focusing effect is experimentally observed for acoustic plane wave normally incident onto a two-dimensional sonic crystal with gradient negative refractive index. The gradual refractive-index is achieved by gradual modification of the lattice spacing both along the transverse and longitudinal directions. It is found that the focal length is controllable by modulation of the lattice spacing. The experiment results are in excellent agreement with theoretical calculation by a multiple scattering theory method.

Peng, Shasha; He, Zhaojian; Jia, Han; Zhang, Anqi; Qiu, Chunyin; Ke, Manzhu; Liu, Zhengyou

2010-06-01

359

Surface plasmon resonance based fiber optic refractive index sensor utilizing silicon layer: Effect of doping  

NASA Astrophysics Data System (ADS)

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.

Bhatia, Priya; Gupta, , Banshi D.

2013-01-01

360

TEACHING PHYSICS: Refractive index determination of materials on thin transparent substrates using ellipsometry  

NASA Astrophysics Data System (ADS)

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.

Lévesque, L.

2000-09-01

361

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)

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.

Frey, Bradley J.; Leviton, Douglas B.

2004-01-01

362

Vertically stacked plasmonic nanoparticles in a circular arrangement: a key to colorimetric refractive index sensing  

NASA Astrophysics Data System (ADS)

True colorimetric sensing produces a linear spectral response of a single peak within the visible light range with various surrounding media refractive indices. We demonstrate how the circular arrangement of hemispheric silver nanoparticles achieves colorimetric properties without modifying the associated full-width-half-maximum values in a broad range of surrounding media refractive indices. We also show that the vertical out-of-plane arrangement of each circular array in nanoholes enhances the signal-to-noise ratio. High electric field confinement at the interface of the nanoparticles and the supporting substrate reveals the effect of the dielectric constant of the substrate and the morphology of the 3D nanoparticle arrays on achieving a single resonance peak in the visible range with a change in the surrounding refractive index. This study opens up the pathway to top-down fabricated nanostructure platform based plasmonic colorimetric sensing with a single resonance peak in the visible range. The studied rich set of tunable geometrical nanostructures enables broadening of the working optical range of the device.True colorimetric sensing produces a linear spectral response of a single peak within the visible light range with various surrounding media refractive indices. We demonstrate how the circular arrangement of hemispheric silver nanoparticles achieves colorimetric properties without modifying the associated full-width-half-maximum values in a broad range of surrounding media refractive indices. We also show that the vertical out-of-plane arrangement of each circular array in nanoholes enhances the signal-to-noise ratio. High electric field confinement at the interface of the nanoparticles and the supporting substrate reveals the effect of the dielectric constant of the substrate and the morphology of the 3D nanoparticle arrays on achieving a single resonance peak in the visible range with a change in the surrounding refractive index. This study opens up the pathway to top-down fabricated nanostructure platform based plasmonic colorimetric sensing with a single resonance peak in the visible range. The studied rich set of tunable geometrical nanostructures enables broadening of the working optical range of the device. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03562c

Seo, Sujin; Gartia, Manas Ranjan; Liu, Gang Logan

2014-09-01

363

Air cavity-based Fabry-Perot interferometer sensor fabricated using a sawing technique for refractive index measurement  

NASA Astrophysics Data System (ADS)

We have demonstrated a refractive index sensor based on a fiber optic Fabry-Perot (FP) interferometer with an open air cavity fabricated using a one-step mechanical sawing technique. The sensor head consists of a short FP cavity near the fiber patch cord tip, which was assembled by joining a ceramic ferrule and a single-mode fiber together. Owing to the open air cavity in the sensor head, various liquid samples with different refractive index can fill in-line air cavity, which makes the device usable as a refractometer. Moreover, due to the sensor head encircled with the robust ceramic ferrule, the device is attractive for sensing measurement in harsh environments. The sensor was tested in different refractive index solutions. The experimental result shows that the attenuation peak wavelength of the sensor is shifted toward a shorter wavelength with increasing refractive index, and the refractive index sensitivity is ˜92.5 nm/refractive index unit (RIU) and 73.75 dB/RIU. The proposed sensor can be used as an in-line refractometer for many potential applications in the sensing field.

Jung, Eun Joo; Lee, Woo-Jin; Kim, Myoung Jin; Hwang, Sung Hwan; Rho, Byung Sup

2014-01-01

364

Thermal and long-term stability of fast-ion-irradiation-induced refractive index changes in lithium niobate crystals  

NASA Astrophysics Data System (ADS)

Irradiation of congruently melting, nominally undoped lithium niobate crystals (LiNbO3) with high-energy, low-mass 3He ions, which are transmitted through the crystal, causes large and stable changes of the refractive index. In the irradiated regions, the extraordinary index is increased whereas the ordinary index is diminished. The decay of these changes upon annealing treatments up to 400°C is investigated, exhibiting a strongly non-monoexponential decay behaviour. Long-term measurements of the refractive index changes yield no pattern erasure on a timescale of four years.

Zamani-Meymian, Mohammad-Reza; Jentjens, Lena; Raeth, Niels L.; Peithmann, Konrad; Maier, Karl

2010-03-01

365

Refractometer for tracking changes in the refractive index of air near 780 nm.  

PubMed

A new system, consisting of a double-channel Fabry-Perot etalon and laser diodes emitting around 780 nm, is described and proposed for use for measuring air-refractive index. The principle of this refractometer is based on frequency measurements between optical laser sources. It permits quasi-instantaneous measurement with a resolution of better than 10(-9) and uncertainty in the 10(-8) range. Some preliminary results on the stability of this system and the measurements of the refractive index of air with this apparatus are presented. The first measurements of the index of air at 780 nm are, within an experimental uncertainty of the order of 2 x 10(-8), in agreement with the predicted values by the so-called revised Edlén equations. This result is, to the best of our knowledge, the first to extend to the near IR the validity of the revised Edlén equation derived for the wavelength range of 350-650 nm. PMID:18268572

Khélifa, N; Fang, H; Xu, J; Juncar, P; Himbert, M

1998-01-01

366

High-refractive index material design for ArF immersion lithography  

NASA Astrophysics Data System (ADS)

High-refractive-index fluids (HIFs) are being considered to replace water as the immersion fluid in next generation 193nm immersion scanner. At SPIE 2006, we have demonstrated the attractive optical properties and good imaging performance for our HIF candidates, HIL-001 and HIL-002. In this paper, we will describe our latest results on the remaining issues for the practical application of HIF candidates, as well as introduce 3 rd generation fluids for the further extension of ArF immersion lithography. In order to improve the fluid transparency, we have tried two approaches. One is the improvement of transparency for HIL-001 based on a refining technology and the other is to develop a novel HIF candidate by using computational chemistry, which is named HIL-203. By passing through a suitable refining unit, HIL-001 can reach a transmittance of >99%/mm, which is as high as water. This new purification method can be applied to an on-site reuse system. It was also found that the refining unit was very effective to eliminate the impurities coming from the photo-degradation of HIL, chemical substances contamination under the air exposure, and leaching of resist components such as photo-acid generator or quencher. We have developed a new fluid for 3 rd generation immersion fluids. It had a higher refractive index than that of HIL-001 or HIL-203; however, it still falls short of our target value. Additionally, by using a novel design concept, we have developed a top-coat with high refractive index for HIL immersion lithography, which gave an appropriate contact angle for scanning exposure.

Furukawa, Taiichi; Kishida, Takanori; Miyamatsu, Takashi; Kawaguchi, Kazuo; Yamada, Kinji; Tominaga, Tetsuo; Slezak, Mark; Hieda, Katsuhiko

2007-03-01

367

Refractive index sensing with Fano resonant plasmonic nanostructures: a symmetry based nonlinear approach.  

PubMed

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. PMID:25381752

Butet, Jérémy; Martin, Olivier J F

2014-12-21

368

Sensitive refractive index sensing with tunable sensing range and good operation angle-polarization-tolerance using graphene concentric ring arrays  

NASA Astrophysics Data System (ADS)

A highly tunable refractive index sensor with excellent performance and good operation angle-polarization-tolerance is proposed and demonstrated numerically by means of the finite element method. The proposed sensor consists of a planar regular array of paired graphene concentric ring resonators sandwiched between a substrate and a sensing medium. Numerical calculation results show that a high sensitivity of 9.59 µm per refractive index unit and figure of merit of 5.82 can be reached for lower sensing medium refractive indices. The introduction of graphene in this sensor can enhance the absorption of biomolecules and make the sensing range actively tunable. Therefore, it can be conveniently used for possible detection of the refractive index variation of gases, liquids or mixed solutions. Also, we predict that a multi-channel sensor can be achieved by introducing several graphene concentric ring resonators into each unit cell of the array.

Li, Kangwen; Ma, Xunpeng; Zhang, Zuyin; Song, Jiakun; Xu, Yun; Song, Guofeng

2014-10-01

369

Determining the unique refractive index properties of solid polystyrene aerosol using broadband Mie scattering from optically trapped beads.  

PubMed

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

Jones, Stephanie H; King, Martin D; Ward, Andrew D

2013-12-21

370

A hybrid LPG/CFBG for highly sensitive refractive index measurements.  

PubMed

A simple and high sensitive method employing a hybrid long period grating (LPG)/chirped fiber Bragg grating (CFBG) for refractive index (RI) measurements is proposed and investigated experimentally. The wide wavelength range of backward cladding modes are excited through the coupling and recoupling between LPG and CFBG. Experimental results indicate that the recoupled cladding modes between LPG and CFBG and core mode are modulated by the surrounding RI and highly sensitive RI measurements can be achieved by simply measuring the reflected intensity changes of the recoupled cladding modes and core mode. PMID:22969347

Sun, An; Wu, Zhishen

2012-01-01

371

Highly sensitive fiber refractive index sensor based on side-core holey structure  

NASA Astrophysics Data System (ADS)

We propose a side-core holey fiber (SCHF)-based surface plasmon resonance (SPR) sensor to achieve high refractive index (RI) sensitivity. The SCHF structure can facilitate analyte filling and enhance the overlapping area of the core mode and surface plasmon polariton (SPP) mode. The coupling properties of the sensor are analyzed by numerical simulation. The maximum sensitivity of 5000 nm/RIU in an RI range of 1.33–1.44, and the average sensitivity of 9295 nm/RIU in an RI range from 1.44 to 1.54 can be obtained.

Han, Ya; Xia, Li; Liu, De-Ming

2014-10-01

372

Temperature insensitive refractive index sensor based on single-mode micro-fiber Sagnac loop interferometer  

NASA Astrophysics Data System (ADS)

A single-mode micro-fiber Sagnac loop interferometer (SMSLI) based on single-mode micro-fiber with a diameter of wavelength scale is demonstrated theoretically and experimentally. The influence of structure parameters in SMSLI on its transmission spectra has been investigated by both experimental and theoretical analysis. The sensor responses to the ambient refractive index (RI) and temperature are also investigated experimentally. Experimental results show that the proposed sensor exhibits quite high sensitivity to the ambient RI, which is found to be ˜12 500 nm/RIU. In addition, the sensitivity of SMSLI to ambient temperature is also demonstrated to be only ˜3 pm/ °C by experiments.

Chunyang, Han; Hui, Ding; Xianli, Li; Shaofei, Dong

2014-05-01

373

Numerical investigation of a refractive index SPR D-type optical fiber sensor using COMSOL multiphysics  

NASA Astrophysics Data System (ADS)

Recently, many programs have been developed for simulation or analysis of the different parameters of light propagation in optical fibers, either for sensing or for communication purposes. In this paper, it is shown the COMSOL Multiphysics as a fairly robust and simple program, due to the existence of a graphical environment, to perform simulations with good accuracy. Results are compared with other simulation analysis, focusing on the surface plasmon resonance (SPR) phenomena for refractive index sensing in a D-type optical fiber, where the characteristics of the material layers, in terms of the type and thickness, and the residual fiber cladding thickness are optimized.

Santos, D. F.; Guerreiro, A.; Baptista, J. M.

2013-03-01

374

Nanowire-based refractive index sensor on the tip of an optical fiber  

NASA Astrophysics Data System (ADS)

This letter presents a refractive index sensor created at the tip of an optical fiber that utilizes silica nanowire within a radius of between 225 nm and 600 nm, as a sensing element. Sensitivity in excess of 800 nm/RIU was demonstrated within an aquatic medium, while the entire sensor structure was shorter than 1 mm with a diameter equal to or less than the standard fiber diameter. The presented sensor structure is made entirely from silica and provides the mechanical protection of sensitive nanowire. The proposed sensor is thus a robust and self-sustained structure, which does not require any complex packing.

Pevec, Simon; Donlagic, Denis

2013-05-01

375

Sensitivity of the Lidar ratio to changes in size distribution and index of refraction  

NASA Technical Reports Server (NTRS)

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.

Evans, B. T. N.

1986-01-01

376

Controlled modification and direct characterization of multimode-fiber refractive-index profiles.  

PubMed

A combination of controlled annealing and characterization by scanning probe microscopy (SPM) is used to demonstrate that the refractive-index proffle of a commercially available silica-based optical fiber can be accurately reconfigured for use as an evanescent field sensor. The process relies on the controlled relocation of the silica glass dopants across the fiber cross section through heat treatment and the accurate measurement of the resulting dopant redistribution with SPM and differential etching techniques. The effect of variable annealing along a length of fiber is to produce a mode transformer to couple light from a laser source into the sensing region of the fiber. PMID:12564481

Gibson, Brant C; Huntington, Shane T; Love, John D; Ryan, Tom G; Cahill, Laurence W; Elton, Darrell M

2003-02-01

377

Negative Index of Refraction Observed in a Single Layer of ClosedRing Magnetic Dipole Resonators  

SciTech Connect

We report the results of a spectroscopic study of a singlelayer of metallic single closed ring resonators on free-standing thinmembrane at near-normal and grazing angles of incidence. When themagnetic component of the light is perpendicular to the ring plane, weobserve a negative index of refraction down to -1 around 150 terahertz(THz), attributed to a strong magnetic dipolar resonance and a broadelectric resonance in this metamaterial. We experimentally identify thedifferent resonance modes and the spectral region of negative refractiveindex on a series of samples with different feature and lattice sizes,comparing to electromagnetic simulations.

Hao, Zhao; Martin, Michael C.; Harteneck, Bruce; Cabrini,Stefano; Anderson, Erik H.

2007-11-27

378

Estimation of refractive index and density of lubricants under high pressure by Brillouin scattering  

NASA Astrophysics Data System (ADS)

Employing a diamond-anvil cell, Brillouin scattering spectra of 90° and 180° angles for synthetic lubricants (paraffinic and naphthenic oils) were measured and sound velocity, density, and refractive index under high pressure were obtained. The density obtained from the thermodynamic relation was compared with that from Lorentz-Lorentz's formula. The density was also compared with Dowson's density-pressure equation of lubricants, and density-pressure characteristics of the paraffinic oil and naphthenic oil were described considering the molecular structure for solidified lubricants. The effect of such physical properties of lubricants on the elastohydrodynamic lubrication of ball bearings, gears and traction drives was considered.

Nakamura, Y.; Fujishiro, I.; Kawakami, H.

1994-07-01

379

Ultrahigh refractive index sensing performance of plasmonic quadrupole resonances in gold nanoparticles  

PubMed Central

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. PMID:24791161

2014-01-01

380

Enhancing the efficiency of slow-wave electron cyclotron masers with the tapered refractive index  

NASA Astrophysics Data System (ADS)

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.

Kong, Ling-Bao; Hou, Zhi-Ling; Jing, Jian; Jin, Hai-Bo; Du, Chao-Hai

2013-04-01

381

Refractive index measured by laser beam displacement at {lambda}=1064 nm for solvents and deuterated solvents  

SciTech Connect

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.

Shelton, David P.

2011-07-20

382

Antireflection-enhanced color by a natural graded refractive index (GRIN) structure.  

PubMed

Nanostructured materials like graded refractive index (GRIN) structures in moth eyes have inspired the design of novel antireflective coatings. Such structures are more flexible than uniform coatings, but applications have been mainly limited to broadband antireflection in solar cells and LEDs. Here we show that cylindrical pigment granules in two bird species (Polyplectron bicalcaratum and Patagioenas fasciata) form a GRIN that suppresses interference and expands the range of colors produced by a multilayer. These results demonstrate that a GRIN structure can function like a pigment (i.e. through selective, independent wavelength blocking) to generate unique colors and may inspire the design of novel antireflective and structurally colored coatings. PMID:24922372

Eliason, Chad M; Shawkey, Matthew D

2014-05-01

383

Corrections to refractive index data of stoichiometric lithium tantalate in the 5-6 microm range.  

PubMed

We propose corrections to the coefficients in the published Sellmeier equation for stoichiometric LiTaO3 [Opt. Lett.28, 194 (2003)] that allow the extension of the wavelength range within the region of midinfrared absorption edge up to 6 microm. The required extraordinary refractive index data for this range were obtained using single-pass optical parametric fluorescence measurements with a pump wavelength of 1064.4 nm. We also observed efficient parasitic second-harmonic generation that could affect some quasi-phase-matching interactions. The corrected Sellmeier equation improves the accuracy of poling period calculations where the idler wavelength is within the region. PMID:16770423

Kolev, V Z; Duering, M W; Luther-Davies, B

2006-07-01

384

Rapid assessment of mid-infrared refractive index anisotropy using a prism coupler: chemical vapor deposited ZnS  

SciTech Connect

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.

Qiao, Hong (Amy) [Amy; Lipschultz, Kristen A.; Anheier, Norman C.; McCloy, John S.

2012-04-01

385

Temperature insensitive refractive index sensor based on concatenated long period fiber gratings  

NASA Astrophysics Data System (ADS)

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.

Tripathi, Saurabh M.; Bock, Wojtek J.; Mikulic, Predrag

2013-10-01

386

Effect of dip in refractive index profile on fiber Raman gain amplifier performance  

NASA Astrophysics Data System (ADS)

We have studied and reported the effect of practically possible linear dips in the inner core of a coaxial fiber Raman gain amplifier having step index inner and outer cores in the structure on the amplifier performance. In this work, we have used single pump wavelength of 1.465 ?m. A variation of dip depth beyond 0.25% of maximum refractive index and that of dip width beyond 25% of the inner core radius deteriorate the gain performance of characteristics of this amplifier significantly along with an appreciable shift of phase matching wavelength. Within these limits, the amplifier resembles closely the behavior of an ideal one. These prescribed limits of dip depth and dip width are also valid limits above which there will be valid ground in their effect to modulate Raman gain performance and dispersion. The present study should find wide attention of system designers.

Pramanik, Sanchita; Sarkar, Somenath

2014-10-01

387

A bio-inspired polymeric gradient refractive index (GRIN) human eye lens.  

PubMed

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

Ji, Shanzuo; Ponting, Michael; Lepkowicz, Richard S; Rosenberg, Armand; Flynn, Richard; Beadie, Guy; Baer, Eric

2012-11-19

388

Corneal imaging and refractive index measurement using a combined multiphoton microscopy and optical coherence tomography system  

NASA Astrophysics Data System (ADS)

Refractive index (RI) is the optical property of a medium that describes its ability to bend incident light. The corneal refractive index is an especially important measurement in corneal and intraocular refractive surgery where its precise estimation is necessary to obtain accurate surgical outcomes. In this study, we calculated the corneal RI using a combined multiphoton microscopy (MPM) and optical coherence tomography (OCT) system. MPM excites and detects nonlinear signals including two photon excitation fluorescence (TPEF) and second harmonic generation (SHG). TPEF signals are observed from NADH in the cytoplasm, allowing MPM to image the cellular structures in the corneal epithelium and endothelium. SHG signals are observed from collagen, an abundant connective tissue found in the stroma. Optical coherence tomography (OCT) produces cross-sectional, structural images based on the interference fringes created by the reflected light from the sample and reference arms. Our system uses a single sub-10 fs Ti: sapphire laser source which is good for both MPM excitation and OCT resolution. The MPM and OCT images are coregistered when they are taken successively because their axial resolutions are similar and the system shares the laser source and the scanning unit. We can calculate the RI by measuring the optical thickness and the optical path length of the cornea from the MPM and OCT images respectively. We have imaged and calculated the RI of murine and piscine corneas. We were able to see the epithelial, stromal, and endothelial layers and compare their relative thicknesses and the organization of the stromal collagen lamellae. Our results showed that our system can provide both functional and structural information about the cornea and measure the RI of multi-layered tissues.

Lai, Tom; Chong, Shau Poh; Zhou, Yifeng; Moloney, Gregory; Tang, Shuo

2013-02-01

389

Detection of refractive index changes in chemical reactions of fluids within micro channels using digital holographic microscopy  

NASA Astrophysics Data System (ADS)

Digital holographic microscopy (DHM) provides a non-destructive measurement technique based on calculation of optical path length changes of the sample under study. If the changes are caused by refractive index variations within a constant physical thickness, the technique results in the precise measurement of the refractive index . In this paper, DHM is utilized to map the refractive index over a wide surface of a T-shaped micro channel. The micro channel is filled up by a solution of two chemical reactant fluids. In some chemical reactions the refractive index of the resultant may be highly different from the refractive indices of the reactants. Using microinjection pumps methane and water as reactants are injected into the channel at the same flow rates. Changes in optical path ways are measured by live recording the digital holograms during the fluids interaction for all the field of view pixels. The holograms are recorded by a detector and post processed by a computer in order to reconstruct the phase profile changes though angular spectrum propagation method. The changes in the refractive indices that take place during the reaction process, are viewed by the detector and are calculated and mapped for the T channel and Y channel.

Nasehi, Adel; Moradi Mehr, Shiva; Moradi, Ali-Reza

2013-11-01

390

Refractive Index and Hygroscopic Stability of Al(x)Ga(1-x)As Native Oxides  

SciTech Connect

The authors present prism coupling measurements on Al{sub x}Ga{sub 1{minus}x}As native oxides showing the dependence of refractive index on composition (0.3 {le} x {le} 0.97), oxidation temperature (400 {le} T {le} 500), and carrier gas purity. Index values range from n = 1.490 (x = 0.9, 400) to 1.707 (x = 0.3, 500 C). The oxides are shown to adsorb moisture, increasing their index by up to 0.10 (7%). Native oxides of Al{sub x}Ga{sub 1{minus}x}As (x {le} 0.5) have index values up to 0.27 higher and are less hygroscopic when prepared with a small amount of O{sub 2} in the N{sub 2} + H{sub 2}O process gas. The higher index values are attributed to a greater degree of oxidation of the Ga in the film.

Blum, O.; Epstein, R.J.; HOu, H.; Hall, D.C.; Kou, L.; Luo, Y.; Wu, H.

1999-07-08

391

Optical emission from a high-refractive-index waveguide excited by a traveling electron beam  

SciTech Connect

An optical emission scheme was demonstrated, in which a high-refractive-index waveguide is excited by a traveling electron beam in a vacuum environment. The waveguide was made of Si-SiO{sub 2} layers. The velocity of light propagating in the waveguide was slowed down to 1/3 of that in free space due to the high refractive index of Si. The light penetrated partly into the vacuum in the form of a surface wave. The electron beam was emitted from an electron gun and propagated along the surface of the waveguide. When the velocity of the electron coincided with that of the light, optical emission was observed. This emission is a type of Cherenkov radiation and is not conventional cathode luminescence from the waveguide materials because Si and SiO{sub 2} are transparent to light at the emitted wavelength. This type of emission was observed in an optical wavelength range from 1.2 to 1.6 {mu}m with an electron acceleration voltage of 32-42 kV. The characteristics of the emitted light, such as the polarization direction and the relation between the acceleration voltage of the electron beam and the optical wavelength, coincided well with the theoretical results. The coherent length of an electron wave in the vacuum was confirmed to be equal to the electron spacing, as found by measuring the spectral profile of the emitted light.

Kuwamura, Yuji; Yamada, Minoru; Okamoto, Ryuichi; Kanai, Takeshi; Fares, Hesham [Division of Electrical Engineering and Computer Science, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192 (Japan)

2008-11-15

392

Core-offset-based fiber Bragg grating sensor for refractive index and temperature measurement  

NASA Astrophysics Data System (ADS)

We present a fiber-optic sensor based on a fiber Bragg grating (FBG) whose core has an offset to that of the lead-in fiber from splicing for simultaneous refractive index (RI) and temperature measurement. Due to the core offset, the core mode in the lead-in fiber is coupled to both the core mode and the cladding modes of the sensing fiber with the FBG. Then the two oppositely propagating code modes, the cladding modes, and the core modes are coupled by the FBG at particular wavelengths determined by the effective indices of the modes and the FBG structure, resulting in two peaks in the FBG reflection spectrum. The peak wavelength corresponding to the core-cladding mode coupling is sensitive to both RI and temperature, while the peak wavelength corresponding to the core-core mode coupling is only sensitive to temperature. Utilizing the difference of two reflection peaks of these coupling modes, both RI and temperature can be detected simultaneously. We fabricate and characterize a sensor. The preliminary experimental results show that it can detect the refractive index in a range of 1.33 to 1.4421, with a temperature sensitivity of 10 pm/°C.

Zhang, Xinpu; Peng, Wei; Liu, Yun; Yu, Qingxu

2013-02-01

393

Refractive index sensing of turbid media by differentiation of the reflectance profile: Analysis of error  

NASA Astrophysics Data System (ADS)

Refractive index detection typically consists of a measurement of the reflectance of light from the sample surface for various angles of incidence, and determining the critical angle for total internal reflection (TIR). A commonly used technique for locating the critical angle is to differentiate the angular reflectance profile with respect to the incidence angle, and look for the point of maximum change of slope. For turbid media this differentiation technique leads to errors in refractive index measurement, which need to be accurately estimated. We show that previous attempts by other workers to calculate the error using traditional Fresnel theory yield an expression that is impossible to physically justify, and hence must be incorrect. We calculate the error using a recent model of TIR in turbid media by Calhoun, et al. (Opt. Lett. 35, 1224 (2010)) which departs from traditional Fresnel theory, and show that this error varies with turbidity in an expected manner. Important differences from previous work relying on traditional Fresnel theory are revealed with regard to the size of error as a function of turbidity, and the choice of polarization for minimizing error.

Dong, Miao; Goyal, Kashika; Kane, Donald; Worth, Bradley; Bali, Lalit; Bali, Samir

2012-06-01

394

Method of time resolved refractive index measurements of x-ray laser heated solids  

NASA Astrophysics Data System (ADS)

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.

Williams, G. O.; Chung, H.-K.; Vinko, S. M.; Künzel, S.; Sardinha, A. B.; Zeitoun, Ph.; Fajardo, M.

2013-04-01

395

Light sheet microscopy of cleared mouse brains: aberrations effects caused by refractive index mismatch  

NASA Astrophysics Data System (ADS)

Fluorescence light sheet microscopy has known a true renaissance in the last years. In fact, since optical sectioning is achieved in a wide-field detection scheme, this technique allows high resolution three-dimensional imaging with high frame rate. Light sheet microscopy is therefore an ideal candidate for reconstructing macroscopic specimens with micron resolution: coupled with clearing protocols based on refractive index matching it has been exploited to image entire mouse brains without physical sectioning. Use of clearing protocols poses several challenges to light sheet microscopy. First of all, residual light scattering inside the tissue expands the excitation light sheet, leading to the excitation of out-of-focus planes, and thus frustrating the very principle of light sheet illumination. To reject out-of-focus contributions we recently coupled light sheet illumination with confocal detection, achieving significant contrast enhancement in real time. Another issue which often arises when working with clearing agents is the refractive index mismatch between the clearing and the medium objective design medium. This introduces severe spherical aberration, which leads to broadening of the point spread function and to a strong reduction in its peak value: When imaging deep (several mm) inside macroscopic specimens, the signal can be reduced by more than an order of magnitude. We investigated the possibility of correcting such spherical aberration by introducing extra optical devices in the detection path.

Silvestri, Ludovico; Sacconi, Leonardo; Pavone, Francesco S.

2013-06-01

396

Vacuum energy and the spacetime index of refraction: A new synthesis  

SciTech Connect

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.

Nouri-Zonoz, M. [Department of Physics, University of Tehran, North Karegar Avenue, Tehran 14395-547 (Iran, Islamic Republic of); School of Astronomy and Astrophysics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531 Tehran (Iran, Islamic Republic of); Nazari, B. [Department of Physics, University of Tehran, North Karegar Avenue, Tehran 14395-547 (Iran, Islamic Republic of)

2010-08-15

397

Negative refractive index and higher-order harmonics in layered metallodielectric optical metamaterials  

E-print Network

We study the propagation of light in a three-dimensional double-periodic Ag/TiO2 multilayer metamaterial composed of coupled plasmonic waveguides operating in the visible and UV spectral range. For these frequencies, light propagation in the plane of the waveguides is described by a negative phase velocity, while for the orthogonal direction light propagation is described by a Bloch wave composed of a large number of harmonics. As a result, the material cannot generally be described by a single phase index: decomposing the Bloch wave into different harmonics we show that for the wavelength range of interest the positive index m=1 harmonic dominates the propagation of light in the orthogonal direction. These results are corroborated by numerical simulations and optical refraction experiments on a double-periodic Ag/TiO2 multilayer metamaterial prism in the 380-600 nm spectral range, which show that positive refraction associated with right-handed harmonics dominates. Studying the isofrequency contours we find ...

Maas, Ruben; Parsons, James; Polman, Albert

2014-01-01

398

Fabrication of Refractive Index Tunable Polydimethylsiloxane Photonic Crystal for Biosensor Application  

NASA Astrophysics Data System (ADS)

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.

Raman, Karthik; Murthy, T. R. Srinivasa; Hegde, G. M.

399

Time variation of adipose tissue refractive index under photodynamic treatment: in vitro study using OCT  

NASA Astrophysics Data System (ADS)

Time variation of the adipose tissue refractive index under photodynamic treatment was studied using OCT. Fat tissue slices 200-500 ?m thick were used in in vitro experiments. To stain the fat tissue we used water-ethanol solutions of indocyanine green (ICG) and brilliant green (BG) with the concentration 1 mg/ml and 6 mg/ml, respectively. The CW laser diode (VD-VII DPSS, 808 nm) and the dental diode irradiator Ultra Lume Led 5 (442 and 597 nm) were used for irradiation of tissue slices. The irradiation time was 5 min for the laser and 15 min for the diode lamp. The experiments were carried out at room temperature. It was discovered the immersion optical clearing of fat tissue slices due to fat cell lipolysis under photodynamic treatment. Released cell content works as an immersion agent, thus the relative refractive index of tissue scatterers decreasing with the time elapsed after the treatment. These data support the hypothesis that photodynamic treatment induces fat cell lipolysis for some period after treatment.

Yanina, Irina Yu.; Trunina, Natalia A.; Tuchin, Valery V.

2012-03-01

400

Structure of the refractive index distribution of the supersonic turbulent boundary layer  

NASA Astrophysics Data System (ADS)

The refractive index field of supersonic turbulent boundary layer with Mach number 3 is measured with the nanoparticle-based planar laser scattering technique, and its structure is investigated from the viewpoints of power spectrum, structure function and correlation function. The power spectrum along streamwise direction shows evident power behavior in a broad region of wavenumber, and the power exponent varies from -1.9 to -1.7 in the logarithmic region. The dominant structures is revealed using the pre-multiplied spectrum, and the length of the largest structure is about 1.2? (? is the thickness of the boundary layer). The structure function of the refractive index along streamwise direction is computed and an analytic expression is suggested to fit the experimental results, which is a modification of the Tatraski model. The power spectrum is computed with the fitting expression and its behavior is analyzed. The characteristic length along normal direction is studied with the linking equation in aero-optics. This length is defined with normal integral of correlation coefficient, and the results with two slightly different definitions of correlation coefficient are compared.

Gao, Qiong; Yi, Shihe; Jiang, Zongfu; He, Lin; Wang, Xiaohu

2013-09-01

401

Extraction of light trapped due to total internal reflection using porous high refractive index nanoparticle films  

NASA Astrophysics Data System (ADS)

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.

Mao, Peng; Sun, Fangfang; Yao, Hanchao; Chen, Jing; Zhao, Bo; Xie, Bo; Han, Min; Wang, Guanghou

2014-06-01

402

Electric field induced optical absorption and refractive index changes in a diluted magnetic quantum well  

NASA Astrophysics Data System (ADS)

Binding energy of a confined exciton is investigated in a CdMnTe/CdMnTe/CdMnTe diluted magnetic quantum well in the influence of electric field. Calculations are performed for various Mn incorporation in Cd1-xMnxTe material within a single band effective mass approximation using variational method. Spin polaronic shifts are estimated using mean field theory for different Mn concentration and the well sizes. A theoretical study of diluted magnetic semiconductors treating local sp-d exchange interaction J between the itinerant carriers and the Mn electrons is treated within a realistic band structure. The optical absorption and the refractive index changes as a function of normalized photon energy in the presence of electric field strength and the Mn ion content are analysed. Our results show that the occurred red shift of the absorption resonant peak due to the electric field gives the information about the variation of two energy levels in the quantum well. The optical absorption coefficients and the refractive index changes strongly depend on the incident optical intensity, the electric field strength and Mn content.

Leonora, J. Merciline; Peter, A. John; Yoo, ChangKyoo

2013-01-01

403

Measurements of the imaginary part of the refractive index between 300 and 700 nanometers for Mount St. Helens ash  

SciTech Connect

The absorption properties, expressed as a wavelength-dependent imaginary index of refraction, of the Mount St. Helens ash from the 18 May 1980 eruption were measured between 300 and 700 nanometers by diffuse reflectance techniques. The measurements were made for both surface and stratospheric samples. The stratospheric samples show imaginary index values that decrease from approximately 0.01 to 0.02 at 300 nanometers to about 0.0015 at 700 nanometers. The surface samples show less wavelength variation in imaginary refractive index over this spectral range.

Patterson, E.M.

1981-01-01

404

Optical coatings of variable refractive index and high laser-resistance from physical-vapor-deposited perfluorinated amorphous polymer  

DOEpatents

Variable index optical single-layers, optical multilayer, and laser-resistant coatings were made from a perfluorinated amorphous polymer material by physical vapor deposition. This was accomplished by physically vapor depositing a polymer material, such as bulk Teflon AF2400, for example, to form thin layers that have a very low refractive index (.about.1.10-1.31) and are highly transparent from the ultra-violet through the near infrared regime, and maintain the low refractive index of the bulk material. The refractive index can be varied by simply varying one process parameter, either the deposition rate or the substrate temperature. The thus forming coatings may be utilized in anti-reflectors and graded anti-reflection coatings, as well as in optical layers for laser-resistant coatings at optical wavelengths of less than about 2000 nm.

Chow, Robert (Livermore, CA); Loomis, Gary E. (Livermore, CA); Thomas, Ian M. (Livermore, CA)

1999-01-01

405

Strong ion migration in high refractive index contrast waveguides formed by femtosecond laser pulses in phosphate glass  

NASA Astrophysics Data System (ADS)

Strong ion migration in shown to enable the production of high refractive index contrast waveguides by fs-laser writing in a commercial (Er,Yb)-doped phosphate based glass. Waveguide writing was performed using a high repetition rate fslaser fibre amplifier operated at 500 kHz and the slit shaping technique. Based on measurements of the NA of waveguides, the positive refractive index change (?n) of the guiding region has been estimated to be ˜1-2 x10-2. The compositional maps of the waveguides cross-sections performed by X-ray microanalysis evidenced a large increase of the La local concentration in the guiding region up to ~25% (relative to the non-irradiated material). This large enrichment in La was accompanied by the cross migration of K to a neighbouring low refractive index zone. The refractive index of the La-phosphate glass increases linearly with the La2O3 content (?n per mole fraction increase of La2O3 ? 5x10-3) mainly because of the relative mass of the La3+ ions. The density increase without substantial modification of the glass network was confirmed by space-resolved micro-Raman spectroscopy measurements showing minor variations in the (PO2)sym vibration Raman band. These results provide evidence for the feasibility of adapting the glass composition for enabling laser-writing of high refractive index contrast structures via spatially selective modification of the glass composition.

Hoyo, J.; Sotillo, Belen; Hernandez, M.; Toney Fernandez, T.; Haro-González, Patricia; Jaque, D.; Fernandez, P.; Domingo, C.; Siegel, J.; Solis, J.

2014-05-01

406

Colossal light-induced refractive-index modulation for neutrons in holographic polymer-dispersed liquid crystals.  

PubMed

We report strong diffraction of cold neutrons from an only 30 micro m thick holographic polymer-dispersed liquid crystal (H-PDLC) transmission grating. The light-induced refractive-index modulation for neutrons is about 10(-6), i.e., nearly 2 orders of magnitude larger than in the best photo-neutron-refractive materials probed up to now. This makes H-PDLCs a promising candidate for fabricating neutron-optical devices. PMID:17155436

Fally, Martin; Drevensek-Olenik, Irena; Ellabban, Mostafa A; Pranzas, Klaus P; Vollbrandt, Jürgen

2006-10-20

407

Colossal Light-Induced Refractive-Index Modulation for Neutrons in Holographic Polymer-Dispersed Liquid Crystals  

Microsoft Academic Search

We report strong diffraction of cold neutrons from an only 30 mum thick holographic polymer-dispersed liquid crystal (H-PDLC) transmission grating. The light-induced refractive-index modulation for neutrons is about 10-6, i.e., nearly 2 orders of magnitude larger than in the best photo-neutron-refractive materials probed up to now. This makes H-PDLCs a promising candidate for fabricating neutron-optical devices.

Martin Fally; Irena Drevensek-Olenik; Mostafa A. Ellabban; Klaus P. Pranzas; Jürgen Vollbrandt

2006-01-01

408

Colossal Light-Induced Refractive-Index Modulation for Neutrons in Holographic Polymer-Dispersed Liquid Crystals  

Microsoft Academic Search

We report strong diffraction of cold neutrons from an only 30 μm thick holographic polymer-dispersed liquid crystal (H-PDLC) transmission grating. The light-induced refractive-index modulation for neutrons is about 10⁻⁶, i.e., nearly 2 orders of magnitude larger than in the best photo-neutron-refractive materials probed up to now. This makes H-PDLCs a promising candidate for fabricating neutron-optical devices.

Martin Fally; Mostafa A. Ellabban; Irena Drevensek-Olenik; Klaus P. Pranzas; Juergen Vollbrandt

2006-01-01

409

On the possibility of quantitative refractive-index tomography of large biomedical samples with hard X-rays  

PubMed Central

One of the most promising applications of the X-ray phase-contrast imaging is the three dimensional tomographic reconstruction of the index of refraction. However, results reported so far are limited to relatively small samples. We present here the tomographic reconstruction of the index of refraction distribution of a large biomedical sample (> 10 cm diameter). A quantitative study comparing the absorption and phase contrast (analyzer-based) tomography images shows that the distribution of the index of refraction obtained with the phase contrast method provides a more accurate depiction (3–10 times larger signal to noise ratio values) of the sample internal structure. Thanks to the higher sensitivity of this method, the improved precision was obtained using an incoming photon fluence on the sample several times smaller than in the case of absorption imaging. PMID:24049673

Gasilov, Sergei; Mittone, Alberto; Brun, Emmanuel; Bravin, Alberto; Grandl, Susanne; Coan, Paola

2013-01-01

410

Design and analysis of a refractive index sensor based on dual-core large-mode-area fiber  

NASA Astrophysics Data System (ADS)

We present a novel co-axial dual core large-mode-area (LMA) fiber design for refractive index sensing. In a dual-core fiber there is resonant coupling between the two cores, which is strongly affected by the refractive index (RI) of the outermost region. The transmittance of the fiber, therefore, varies sharply with the refractive index of surrounding medium. This characteristic of the proposed structure has been utilized to design a RI sensor. We have analyzed the structure by using the transfer matrix method. Our numerical results show that the proposed sensor is highly sensitive with the resolution of 2.0 × 10-6 around nex = 1.44376. Effect of design parameters on sensitivity of the proposed sensor has also been investigated.

Kamakshi, Koppole; Rastogi, Vipul; Kumar, Ajeet

2013-08-01

411

Giant refractive-index modulation by two-photon reduction of fluorescent graphene oxides for multimode optical recording  

PubMed Central

Graphene oxides (GOs) have emerged as precursors offering the potential of a cost-effective and large-scale production of graphene-based materials. Despite that their intrinsic fluorescence property has already brought interest of researchers for optical applications, to date, refractive-index modulation as one of the fundamental aspects of optical properties of GOs has received less attention. Here we reported on a giant refractive-index modulation on the order of 10?2 to 10?1, accompanied by a fluorescence intensity change, through the two-photon reduction of GOs. These features enabled a mechanism for multimode optical recording with the fluorescence contrast and the hologram-encoded refractive-index modulation in GO-dispersed polymers for security-enhanced high-capacity information technologies. Our results show that GO-polymer composites may provide a new material platform enabling flexible micro-/nano-photonic information devices. PMID:24085266

Li, Xiangping; Zhang, Qiming; Chen, Xi; Gu, Min

2013-01-01

412

Elimination of total internal reflection in GaInN light-emitting diodes by graded-refractive-index micropillars  

SciTech Connect

A method for enhancing the light-extraction efficiency of GaInN light-emitting diodes (LEDs) by complete elimination of total internal reflection is reported. Analytical calculations show that GaInN LEDs with multilayer graded-refractive-index pillars, in which the thickness and refractive index of each layer are optimized, have no total internal reflection. This results in a remarkable improvement in light-extraction efficiency. GaInN LEDs with five-layer graded-refractive-index pillars, fabricated by cosputtering TiO{sub 2} and SiO{sub 2}, show a light-output power enhanced by 73% and a strong side emission, consistent with analytical calculations and ray-tracing simulations.

Kim, Jong Kyu; Noemaun, Ahmed N.; Mont, Frank W.; Meyaard, David; Schubert, E. Fred [Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Poxson, David J. [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Kim, Hyunsoo; Sone, Cheolsoo; Park, Yongjo [Central R and D Institute, Samsung Electro-Mechanics, Suwon 443-743 (Korea, Republic of)

2008-12-01

413

Photonic Crystal Fiber Mach-Zehnder Interferometer for Refractive Index Sensing  

PubMed Central

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10?4–8.88 × 10?4 RIU or 1.02 × 10?4–9.04 × 10?4 RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications. PMID:22736988

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

414

Photonic crystal fiber Mach-Zehnder interferometer for refractive index sensing.  

PubMed

We report on a refractive index sensor using a photonic crystal fiber (PCF) interferometer which was realized by fusion splicing a short section of PCF (Blaze Photonics, LMA-10) between two standard single mode fibers. The fully collapsed air holes of the PCF at the spice regions allow the coupling of PCF core and cladding modes that makes a Mach-Zehnder interferometer. The transmission spectrum exhibits sinusoidal interference pattern which shifts differently when the cladding/core surface of the PCF is immersed with different RI of the surrounding medium. Experimental results using wavelength-shift interrogation for sensing different concentrations of sucrose solution show that a resolution of 1.62 × 10(-4)-8.88 × 10(-4) RIU or 1.02 × 10(-4)-9.04 × 10(-4) RIU (sensing length for 3.50 or 5.00 cm, respectively) was achieved for refractive indices in the range of 1.333 to 1.422, suggesting that the PCF interferometer are attractive for chemical, biological, biochemical sensing with aqueous solutions, as well as for civil engineering and environmental monitoring applications. PMID:22736988

Wang, Jian-Neng; Tang, Jaw-Luen

2012-01-01

415

Concentration tuned bandgap and corresponding nonlinear refractive index dispersion in Ga-Ge-Se nanocolloids  

NASA Astrophysics Data System (ADS)

Solution-processing of chalcogenide glass materials has attracted attention for the fabrication of photonic devices. We have carried out linear and nonlinear optical studies on Ga9Ge27Se64 nanocolloidal solutions with varying concentrations and witnessed the opportunity for engineering the optical properties of the material by simply changing the concentration of solute in the solvent. An enhancement of bandgap, deterioration, and blue shift in the band tail states with decrease in concentration were observed from the absorption spectra. Open and closed aperture Z-scan studies reveal tunability of nonlinear absorption coefficient (?) and nonlinear refractive index (n2). As the bandgap approaches the one photon absorption edge, the material shows very large negative nonlinear refraction and also "two step photon absorption" due to the presence of intermediate tail states. The radial phase shift (??0) induced after travelling through the nanocolloidal solution with respect to bandgap is plotted and we predict that the variation of ??0 is governed by a quadratic polynomial of Eg.

Sebastian, Indu; Mathew, S.; Nampoori, V. P. N.; Radhakrishnan, P.; Thomas, Sheenu

2013-08-01

416

Refractive-index based tomosynthesis using dark-field imaging optics  

NASA Astrophysics Data System (ADS)

Tomosynthesis (TS) is a pseudo-3-dimensional image reconstruction method to recover depth-resolved information using restricted number of projections. In this research, refraction index based TS imaging using dark-field imaging (DFI) optics is proposed and biomedical soft tissues were imaged in low dose exposure. By a single exposure of an object, two projected images are obtained from a Laue-case analyzer of DFI. Calculating the both images refraction component is deduced, while two exposures are needed in DEI (diffraction enhanced imaging). Thus the measurement time and the radiation dose in DFI are half of DEI. In addition, the proposed reconstruction algorithm, derived from the quantitative relationship in measurement process, allows high contrast tomographic imaging in spite of one order smaller number of projections for CT (computed tomography). To demonstrate the proposed imaging protocol efficacy, an ex-vivo excised tissue of human lung were imaged using a system constructed at the vertical wiggler beamline at PF-BL14C at KEK. TS image is successfully delineated high quality soft tissue structures comparable to CT.

Sunaguchi, N.; Yuasa, T.; Ichihara, S.; Huo, Q.; Sakai, M.; Wu, Y.; Shimao, D.; Ando, M.

2013-03-01

417

Highly sensitive detection of naphthalene in solvent vapor using a functionalized PBG refractive index sensor.  

PubMed

We report an optical refractive index sensor system based on a planar Bragg grating which is functionalized by substituted ?-cyclodextrin to determine low concentrations of naphthalene in solvent vapor. The sensor system exhibits a quasi-instantaneous shift of the Bragg wavelength and is therefore capable for online detection. The overall shift of the Bragg wavelength reveals a linear relationship to the analyte concentration with a gradient of 12.5 ± 1.5 pm/ppm. Due to the spectral resolution and repeatability of the interrogation system, this corresponds to acquisition steps of 80 ppb. Taking into account the experimentally detected signal noise a minimum detection limit of 0.48 ± 0.05 ppm is deduced. PMID:22438751

Girschikofsky, Maiko; Rosenberger, Manuel; Belle, Stefan; Brutschy, Malte; Waldvogel, Siegfried R; Hellmann, Ralf

2012-01-01

418

Birefringent microfiber-based fiber loop mirrors for tunable filters and refractive index sensors  

NASA Astrophysics Data System (ADS)

Highly birefringent (Hi-Bi) microfiber-based fiber loop mirrors (FLMs) were studied for tunable comb filters and refractive index (RI) sensors. RI sensitivity of up to 15,441 nm/RIU was experimentally demonstrated for the RI sensors and, for the tunable filter a thermal tuning coefficient of ~-2.35nm/°C was obtained for temperature from 20 to 90°C when it was immersed into water. The use of two cascaded Hi-Bi micro-tapers within a Sagnac loop allows more flexibility in controlling the transmission/reflection spectraums of the FLM. The length of the tapered Hi-Bi microfibers is on the order of centimeters, two orders of magnitude shorter than the conventional Hi-Bi fiber-based devices.

Jin, Wa; Xuan, Haifeng; Jin, Wei

2013-05-01

419

Interrogation of in-series double cladding fiber sensor for simultaneous refractive index and temperature measurement  

NASA Astrophysics Data System (ADS)

An interrogation scheme for an in-series double cladding fiber (DCF) sensor is proposed and demonstrated, which can be used for simultaneous refractive index (RI) and temperature measurement. It utilizes two commercial distributed feedback lasers to match two cascade DCF sensors which have two band-rejected filtering spectra at different wavelengths. The two lasers were intensity modulated by different frequencies and demodulated by a lock-in amplifier. Experimental results indicated that a resolution of +/-2×10-5 in RI and +/-1.2°Cin temperature were achieved. Based on the simple and low cost interrogation scheme, the dual parameters sensor system will find potential applications in chemical sensors and biosensors.

Qi, Bo; Pang, Fufei; Wang, Tingyun; Chen, Na; Huang, Sujuan; Chen, Zhenyi

2012-06-01

420

S-tapered photonic crystal fiber interferometers for refractive index sensing  

NASA Astrophysics Data System (ADS)

An experimental investigation on an S-tapered photonic crystal fiber interferometer is presented. The whole fabrication process was carried out using a standard splicing machine. The interferometer shows a compact and stable structure with a waist diameter of 110 ?m, taper length of 280 ?m, and axial offset of 40 ?m. The transmission spectra indicated that it is highly sensitive to the surrounding refractive index (RI) and insensitive to temperature. Resolutions of 3.3×10-4 and 8.0×10-5 RI units were achieved in the 1.33 to 1.38 and 1.38 to 1.44 range, respectively. Furthermore, its temperature dependence was only 4 pm/°C.

Shi, Feifei; Wu, Yun; Wang, Jinzhong; Zhao, Liancheng; Shi, Huizhong

2013-03-01

421

Sensitivity analysis of a photonic crystal waveguide for refraction index sensing  

NASA Astrophysics Data System (ADS)

Photonic crystal (PC) sensors have attracted much attention because of their inherent compactness, high sensitivity and biocompatibility traits. In this paper, we analyze the design of highly sensitive infiltrated liquid sensors based on a two-dimensional PC slab waveguide formed by increasing the radii of air holes localized on each side of the line defect and filling with homogeneous de-ionized water (nc = 1.33). The transmission spectrum of the sensor has been obtained by the finite-difference time domain method, and it has been observed that a 270 nm wavelength position of the upper band edge shift was observed corresponding to a sensitivity of more than 818 nm per refractive index unit. The simulation results on the sensitive PC structure show that the optical properties of PCs can be used to design sensing devices characterized by a high degree of compactness and good resolution.

Bougriou, F.; Boumaza, T.; Bouchemat, M.; Paraire, N.

2012-11-01

422

Topological insulator metamaterials with tunable negative refractive index in the optical region  

PubMed Central

A blueshift tunable metamaterial (MM) exhibiting a double-negative refractive index based on a topological insulator (bismuth selenide, Bi2Se3) has been demonstrated in the near-infrared (NIR) spectral region. The potential of Bi2Se3 as a dielectric interlayer of the multilayer MM is explored. The optical response of elliptical nanohole arrays penetrating through Au/Bi2Se3/Au films is numerically investigated using the finite difference time domain (FDTD) method. The blueshift tuning range of the MM is as high as 370 nm (from 2,140 to 1,770 nm) after switching the Bi2Se3 between its trigonal and orthorhombic states. PMID:24330596

2013-01-01

423

Demonstration of complex refractive index of graphene waveguide by microfiber-based Mach-Zehnder interferometer.  

PubMed

The complex refractive index (CRI) of graphene waveguide (GW) is of great importance for modeling and developing graphene-based photonic or optoelectronic devices. In this paper, the CRI of the GW is investigated theoretically and experimentally, it is found that the CRI of the GW will modulate the intensity and phase of transmitting light. The phase alterations are obtained spectrally by a Microfiber-based Mach-Zehnder interferometer (MMZI), experimental results demonstrate that the CRIs of the GW vary from 2.91-i13.92 to 3.81-i14.64 for transmitting wavelengths ranging from 1510 to 1590 nm. This method cannot only be used to determine the CRI of the GW optically and provide one of the fundamental parameters for designing graphene-based optic devices for communication and sensing applications, but also is adoptable in graphene-based transformation optics for determination of the CRI of the GW at other wavelengths. PMID:24514531

Yao, Baicheng; Wu, Yu; Wang, Zegao; Cheng, Yang; Rao, Yunjiang; Gong, Yuan; Chen, Yuanfu; Li, Yanrong

2013-12-01

424

Flow Measurement in Porous Media Using Particle Tracking Velocimetry and Matching Refractive Index  

NASA Astrophysics Data System (ADS)

In this study, an experiment in a packed bed column is performed to obtain pore-scale full-field velocity components of the flow. Particle tracking velocimetry (PTV) technique is used to obtain instantaneous accurate flow fields and detailed information of the flow patterns. A refractive index matching liquid is used to provide the required transparency, so the measurements could be performed at the middle plane of the packed bed reactor. Immersion optical methods are applied to explore transfer phenomena in multiphase granular beds. In this research, P-Cymene 99% is investigated as the working fluid in a packed bed vertical square channel for the immersed method. P-cymene is chosen because of the close similarity of its physical properties to those of the water.

Dominguez Ontiv, E.; Estrada-Perez, C.; Hassan, Y.; Mendoza-Sanchez, I.

2005-12-01

425

Preparation of inulin-type fructooligosaccharides using fast protein liquid chromatography coupled with refractive index detection.  

PubMed

A fast protein liquid chromatography coupled with refractive index detection (FPLC-RID) method was firstly developed for preparation and purification of fructooligosaccharides with different degree of polymerization from burdock, Arctium lappa. After extraction with 60% ethanol and decolorization with MCI gel CHP20P, total fructooligosaccharides were purified on Bio-Gel P-2 column eluted with water at the flow rate of 0.3 ml/min, which was the optimized conditions. The obtained fructooligosaccharides with degree of polymerization of 3-9 were identified based on their methylation analysis, MS and NMR data. This method has the advantages of high automation, good recovery and easy performance, which could be used for preparation of FOS from other sources, as well as other targeted compounds without UV absorbance. PMID:23962565

Li, J; Cheong, K L; Zhao, J; Hu, D J; Chen, X Q; Qiao, C F; Zhang, Q W; Chen, Y W; Li, S P

2013-09-20

426

Domain reversal properties and refractive index changes of magnesium doped lithium niobate upon ion exposure  

NASA Astrophysics Data System (ADS)

Irradiation of optical damage resistant, magnesium doped lithium niobate crystals with fast, high-energy He2+3 ions changes important material properties. In the interaction region, where the ions transmit through the material, the ferroelectric coercive field EC is diminished from 6.0kVmm-1 down to 5.0-5.4kVmm-1 after transmission of 41MeV He2+3 particles. This enables easier domain reversal in irradiated crystals compared to untreated material. Besides, large changes of the refractive index of the crystals on the order of 6×10-3 are induced by the treatment. Moderate annealing treatments do not diminish ?n, but refresh the coercive field.

Jentjens, L.; Hattermann, H.; Peithmann, K.; Haaks, M.; Maier, K.; Kösters, M.

2008-02-01

427

Seeded growth of titania colloids with refractive index tunability and fluorophore-free luminescence.  

PubMed

Titania is an important material in modern materials science, chemistry, and physics because of its special catalytic, electric, and optical properties. Here, we describe a novel method to synthesize colloidal particles with a crystalline titania, anatase core and an amorphous titania-shell structure. We demonstrate seeded growth of titania onto titania particles with accurate particle size tunability. The monodispersity is improved to such an extent so that colloidal crystallization of the grown microspheres becomes feasible. Furthermore, seeded growth provides separate manipulation of the core and shell. We tuned the refractive index of the amorphous shell between 1.55 and 2.3. In addition, the particles show luminescence when trace amounts of aminopropyl-triethoxysilane are incorporated into the titania matrix and are calcined at 450 °C. Our novel colloids may be useful for optical materials and technologies such as photonic crystals and optical trapping. PMID:21218840

Demirörs, Ahmet Faik; Jannasch, Anita; van Oostrum, Peter D J; Schäffer, Erik; Imhof, Arnout; van Blaaderen, Alfons

2011-03-01

428

Domain reversal properties and refractive index changes of magnesium doped lithium niobate upon ion exposure  

SciTech Connect

Irradiation of optical damage resistant, magnesium doped lithium niobate crystals with fast, high-energy {sup 3}He{sup 2+} ions changes important material properties. In the interaction region, where the ions transmit through the material, the ferroelectric coercive field E{sub C} is diminished from 6.0 kV mm{sup -1} down to 5.0-5.4 kV mm{sup -1} after transmission of 41 MeV {sup 3}He{sup 2+} particles. This enables easier domain reversal in irradiated crystals compared to untreated material. Besides, large changes of the refractive index of the crystals on the order of 6x10{sup -3} are induced by the treatment. Moderate annealing treatments do not diminish {delta}n, but refresh the coercive field.

Jentjens, L.; Hattermann, H.; Peithmann, K.; Haaks, M.; Maier, K.; Koesters, M. [Helmholtz-Institut fuer Strahlen- und Kernphysik, Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany); Physikalisches Institut, Universitaet Bonn, Wegelerstr. 8, D-53115 Bonn (Germany)

2008-02-01

429

Elliptical-core two mode fiber sensors and devices incorporating photoinduced refractive index gratings  

NASA Technical Reports Server (NTRS)

Results of experiments performed using germanium-doped, elliptical core, two-mode optical fibers whose sensitivity to strain was spatially varied through the use of chirped, refractive-index gratings permanently induced into the core using Argon-ion laser light are presented. This type of distributed sensor falls into the class of eighted-fiber sensors which, through a variety of means, weight the strain sensitivity of a fiber according to a specified spatial profile. We describe results of a weighted-fiber vibration mode filter which successfully enhances the particular vibration mode whose spatial profile corresponds to the profile of the grating chirp. We report on the high temperature survivability of such grating-based sensors and discuss the possibility of multiplexing more than one sensor within a single fiber.

Greene, Jonathan A.; Miller, Mark S.; Starr, Suzanne E.; Fogg, Brian R.; Murphy, Kent A.; Claus, Richard O.; Vengsarkar, Ashish M.

1991-01-01

430

Sectional imaging of spatially refractive index distribution using coaxial rotation digital holographic microtomography  

NASA Astrophysics Data System (ADS)

We propose and demonstrate a novel optical section imaging technique to measure the spatially refractive index (RI) distribution inside a sample using coaxial rotation digital holographic microtomography (DH?T). In this method, the illuminated laser source and image sensor are lined up and simultaneously rotated around the sample. The transmitted waves collected from the sample are used to generate a symmetric frequency, coverage as in a sample-rotation approach was discussed and simulated theoretically. We experimentally performed the sectional imaging of the RI inside a silicon micro-bead immersed in a liquid surrounding medium, to confirm the coaxial rotation DH?T as having the phase stability for tomographic recording and the reconstruction process. This sectional imaging technique is applied to measure the spatially RI distribution of a fusion structure between a single mode fiber and a polarization-maintaining fiber.

Lin, Yu-Chih; Cheng, Chau-Jern

2014-06-01

431

Whistler-mode refractive index gradients in the inner magnetosphere: Themis observations  

NASA Astrophysics Data System (ADS)

Whistler-mode waves such as chorus and hiss can have a pronounced effect on the inner magnetosphere and radiation belts. The propagation paths followed by these waves, and hence their geophysical effect, depend on local gradients in the refractive index, and are particularly influenced by gradients in the density. Propagation has typically been considered in one of two idealized cases: either a smooth magnetosphere or a deep duct. Using Themis data, we characterize observed density gradients using simultaneous measurements from multiple closely-spaced satellites under a variety of conditions, and show that the measured gradients are often very different from these ideals. We discuss the consequences of these observed gradients on whistler-mode chorus propagation paths and geoeffectiveness.

Cully, C. M.; Danko, A.

2013-12-01

432

Optical characterization of refractive index sensors based on planar waveguide Fabry-Pérot Bragg grating cavity  

NASA Astrophysics Data System (ADS)

The evanescent field-based polymeric planar waveguide refractive index sensors having a high Q Fabry-Pérot (FP) cavity between identical dual Bragg gratings corrugated on the surface of the planar waveguide were developed. The FP Bragg gratings cavity was fabricated with a cavity size of 5 and 7 mm, respectively. The spectra of light reflected from fabricated Bragg gratings, which were butt joined, were measured and compared with different indices of surrounding media. It was obtained that the FP Bragg gratings cavity is more sensitive than the single Bragg grating. The sensor developed shows much promise in the application of biomedical diagnostics such as a biosensor and/or environmental monitoring systems.

Lee, Sang-Mae; Jeong, Won-Taek; Kim, Kyung-Chun; Kim, Kyung-Jo; Oh, Mincheol; Saini, Simarjeet S.; Dagenais, Mario

2013-01-01

433

Measurement of Organic Chemical Refractive Indexes Using an Optical Time-Domain Reflectometer  

PubMed Central

In this investigation, we propose and experimentally demonstrate a method for measuring the refractive index (RI) of liquid organic chemicals. The scheme is based on a single-mode fiber (SMF) sensor and an optical time-domain reflectometer (OTDR). Here, due to the different reflectance (R) between the SMF and organic liquid chemicals, the reflected power level of the backscattering light (BSL) measured by the OTDR would be different. Therefore, we can measure the RI of chemical under test via the measured BSL level. The proposed RI sensor is simple and easy to manipulate, with stable detected signals, and has the potential to be a valuable tool for use in biological and chemical applications. PMID:22368480

Yeh, Chien-Hung; Chow, Chi-Wai; Sung, Jiun-Yu; Wu, Ping-Chun; Whang, Wha-Tzong; Tseng, Fan-Gang

2012-01-01

434

Highly Sensitive Detection of Naphthalene in Solvent Vapor Using a Functionalized PBG Refractive Index Sensor  

PubMed Central

We report an optical refractive index sensor system based on a planar Bragg grating which is functionalized by substituted ?-cyclodextrin to determine low concentrations of naphthalene in solvent vapor. The sensor system exhibits a quasi-instantaneous shift of the Bragg wavelength and is therefore capable for online detection. The overall shift of the Bragg wavelength reveals a linear relationship to the analyte concentration with a gradient of 12.5 ± 1.5 pm/ppm. Due to the spectral resolution and repeatability of the interrogation system, this corresponds to acquisition steps of 80 ppb. Taking into account the experimentally detected signal noise a minimum detection limit of 0.48 ± 0.05 ppm is deduced. PMID:22438751

Girschikofsky, Maiko; Rosenberger, Manuel; Belle, Stefan; Brutschy, Malte; Waldvogel, Siegfried R.; Hellmann, Ralf

2012-01-01

435

Creating wide-band negative-index-of-refraction metamaterials with fractal-based geometry  

NASA Astrophysics Data System (ADS)

A burgeoning topic of modern research in electrodynamics and antenna design is the design and fabrication of ``left-handed'' metamaterials. This ``left-handedness'' is often created through use of an array of conductive structures with geometry appropriate for coupling on the wavelength scale with incident radiation to produce a phase-shifted reflected wave that cancels out incoming radiation and prevents transmission. This property has been demonstrated in several papers published in the last decade. In every instance, though the ``left-handed'' response is only exhibited in a small bandwidth centered about a specific frequency (bandwidth typically less that 0.1 GHz). I will show that through use of tessellated, fractal-based structures, one can create a repeatable geometry that exhibits a negative index of refraction (NIR) for multiple frequency bands, limited only by fabrication precision, with the ultimate goal being a wide-band absorptive response.

Penney, Keith

2009-11-01

436

Sensitivity of propagation and energy deposition in femtosecond filamentation to the nonlinear refractive index  

E-print Network

The axial dependence of femtosecond filamentation in air is measured under conditions of varying laser pulsewidth, energy, and focusing f-number. Filaments are characterized by the ultrafast z-dependent absorption of energy from the laser pulse and diagnosed by measuring the local single cycle acoustic wave generated. Results are compared to 2D+1 simulations of pulse propagation, whose results are highly sensitive to the instantaneous (electronic) part of the nonlinear response of $N_2$ and $O_2$. We find that recent measurements of the nonlinear refractive index ($n_2$) in [J.K. Wahlstrand et al., Phys. Rev. A. 85, 043820 (2012)] provide the best match and an excellent fit between experiments and simulations.

Rosenthal, E W; Jhajj, N; Zahedpour, S; Wahlstrand, J K; Milchberg, H M

2014-01-01

437

On the feasibility of optical-CT imaging in media of different refractive index  

SciTech Connect

Purpose: Achieving accurate optical-CT 3D dosimetry without the use of viscous refractive index (RI) matching fluids would greatly increase convenience. Methods: Software has been developed to simulate optical-CT 3D dosimetry for a range of scanning configurations including parallel-beam, point, and converging light sources. For each configuration the efficacy of three refractive media was investigated: air, water, a fluid closely matched to PRESAGE{sup Registered-Sign }, and perfect matching (RI = 1.00, 1.33, 1.49, and 1.501 respectively). Reconstructions were performed using both filtered backprojection (FBP) and algebraic reconstruction technique (ART). The efficacy of the three configurations and the two algorithms was evaluated by calculating the usable radius (i.e., the outermost radius where data were accurate to within 2%), and gamma ({Gamma}) analysis. This definition recognizes that for optical-CT imaging, errors are greatest near the edge of the dosimeter, where refraction can be most pronounced. Simulations were performed on three types of dose distribution: uniform, volumetric modulated arc therapy (VMAT), and brachytherapy (Cs-137). Results: For a uniformly irradiated dosimeter the usable radius achieved with filtered backprojection was 68% for water-matching and 31% for dry-scanning in air. Algebraic reconstruction gave usable radii of 99% for both water and air (dry-scanning), indicating greater recovery of useful data for the uniform distribution. FBP and ART performed equally well for a VMAT dose distribution where less dose is delivered near the edge of the dosimeter. In this case, the usable radius was 86% and 53% for scanning in water and air, respectively. For brachytherapy, the usable radius was 99% and 98% for scanning in water and air, respectively using FBP, and a major decrease was seen with ART. Point source geometry provided 1%-2% larger usable radii than parallel geometry. Converging geometry recovered less usable dosimetry data (up to 10% reduced usable radii) than point and parallel geometries. A further disadvantage of converging geometry was an increased requirement on detector size by up to 18 Degree-Sign . Conclusions: For applications where dose information is not required in the periphery of the dosimeter, some dry and low-viscous matching configurations may be feasible. For all three dose distributions (uniform, VMAT, brachytherapy) the point source geometry produced slightly more favorable results (an extra 1%-2% usable radii) than parallel and converging. When dosimetry is required on the periphery, best results were obtained using close refractive matching and ART. A concern for water or dry-scanning is the increase in required detector size, introducing potential cost penalties for manufacturing.

Rankine, Leith [Medical Physics Graduate Program, Duke University, Durham, North Carolina 27710 (United States); Oldham, Mark [Department of Radiation Oncology Physics, Duke University Medical Center, Durham, North Carolina 27710 (United States)

2013-05-15

438

High-sensitivity fiber refractive index sensor formed by sandwiching a thinned taper between two abrupt tapers  

NASA Astrophysics Data System (ADS)

A fiber refractive index (RI) sensor based on a Mach-Zehnder interferometer (MZI) formed by sandwiching a thinned taper between two abrupt tapers. The abrupt tapers and the thinned taper are easily fabricated by a commercial fiber fusion splicer and a homemade tapering machine, respectively. The sensor has been experimentally demonstrated for RI sensing by monitoring its spectral shifts. The experimental results show that the sensor with a thinner taper has higher sensitivity due to the strong evanescent field interaction. A sensitivity of 3808.4 nm/RIU (refractive index unit) is obtained, which is about 100 times higher than that of the conventional taper-based MZI sensors.

Chen, Jinping; Zhou, Jun; Shu, Lei; Ma, Yanan; Zhang, Haopeng

2013-12-01

439

Fiber optic refractive index sensor based on ?-phase shifted fiber Bragg grating fabricated on etched side-hole fiber  

NASA Astrophysics Data System (ADS)

In this paper, we present a temperature-insensitive refractive index sensor based on ?-phase-shifted Bragg gratings fabricated on side-hole fibers processed by wet chemical etching technique. The reflection spectrum of the ?-phase shifted gratings on etched side-hole fiber features two notches with large spectral separation, which was used for refractive index (RI) detection in our application. The relative spectral notch separation exhibited a RI sensitivity of -278.5 pm/RIU (RIU: RI unit). Theoretical simulation obtained the temperature sensitivity of -0.00241 pm/°C, and experimental results also showed little sensitivity to temperature of our RI sensor.

Zhang, Qi; Hu, Lingling; Tian, Jiajun; Ianno, Natale J.; Han, Ming

2013-05-01

440

Photosensitive polymers undergoing photo-Fries reaction for volume holography: understanding the mechanism of refractive index modulation  

NASA Astrophysics Data System (ADS)

Polymers that undergo to photo-Fries reaction show a remarkable modulation of the refractive index that makes them interesting in the field of volume holography. In order to understand the mechanism of the change in the refractive index we performed theoretical calculations (DFT) on model molecules. The results show that the modulation can be ascribed to a change in the polymer density upon photo-reaction whereas the contribution due to a change in molecular polarizability is small. The theoretical conclusions have been supported by experimental results on two polymers: Polyformyloxide styrene (PFS) and polyacetoxystyrene (PAS).

Bianco, A.; Zanutta, A.; Colella, L.; Bertarelli, C.

2014-02-01

441

Active suppression of air refractive index fluctuation using a Fabry-Perot cavity and a piezoelectric volume actuator  

SciTech Connect

Air refractive index fluctuation ({Delta}n{sub air}) is one of the largest uncertainty sources in precision interferometry systems that require a resolution of nanometer order or less. We introduce a method for the active suppression of {Delta}n{sub air} inside a normal air-environment chamber using a Fabry-Perot cavity and a piezoelectric volume actuator. The temporal air refractive index (n{sub air}) at a local point is maintained constant with an expanded uncertainty of {approx}4.2x10{sup -9} (k=2), a sufficiently low uncertainty for precise measurements unaffected by {Delta}n{sub air} to be made inside a chamber.

Banh, Tuan Quoc; Ohkubo, Yuria; Murai, Yoshinosuke; Aketagawa, Masato

2011-01-01

442

Interference color modulation, tunable refractive index, and chiroptical electrochromism in a ?-conjugated polymer with cholesteric liquid crystal order  

NASA Astrophysics Data System (ADS)

A ?-conjugated polymer film prepared by electrolytic polymerization using a cholesteric liquid crystal (CLC) is demonstrated to have a tunable interference function under electrochemical doping and dedoping. The polymer exhibits a CLC-like periodic structure with a potential-dependent refractive index and optical absorption properties. The interference color of the polymer film can thus be modulated dynamically by appropriate application of a voltage in the ±1 V range. This research involves structural chirality and tunable chiroptical properties, doping-dedoping driven tunable refractive index, electrochromism, and interference color modulation for the present polymer. The phenomena demonstrate the possibility of electrochemical photonics.

Goto, Hiromasa

2009-06-01

443

Interfacial refractive index sensing using visible-excited intrinsic zinc oxide photoluminescence coupled to whispering gallery modes  

NASA Astrophysics Data System (ADS)

Whispering gallery modes (WGMs) excited by the intrinsic photoluminescence (PL) in zinc oxide microspherical resonators are investigated in this work. The microspheres were synthesized via a one-pot hydrothermal technique. A polymer was applied after the synthesis to fill remaining pores in the oxide particle. Defect-related ZnO PL was excited in the visible, coupling to WGMs. The observed WGMs red-shift with increasing refractive index of the surrounding medium with a sensitivity of 90-100 nm/refractive index unit. The spherical microresonators may be used to investigate binding to and structure at the particle/solution interface.

Moirangthem, Rakesh Singh; Erbe, Andreas

2013-07-01

444

Diffractionless beam in free space with adiabatic changing refractive index in a single mode tapered slab waveguide  

PubMed Central

We propose a novel design to produce a free space diffractionless beam by adiabatically reducing the difference of the refractive index between the core and the cladding regions of a single mode tapered slab waveguide. To ensure only one propagating eigenmode in the adiabatic transition, the correlation of the waveguide core width and the refractive index is investigated. Under the adiabatic condition, we demonstrate that our waveguide can emit a diffractionless beam in free space up to 500 micrometers maintaining 72% of its original peak intensity. The proposed waveguide could find excellent applications for imaging purposes where an extended depth of field is required. PMID:19997414

Tsai, Chang-Ching; Vinegoni, Claudio; Weissleder, Ralph

2009-01-01

445

A Broadband Optical Ring Resonator for Absorption and Refractive Index Detection  

NASA Astrophysics Data System (ADS)

Optical ring resonators have been studied in recent years as chemical sensors. Conventionally, these devices are operated by means of tracking a single resonance wavelength through use of a finely tunable laser source. This wavelength will shift as a result of changing resonator conditions, such as a refractive index (RI) shift resulting from sample analyte activity. In this work, an alternative approach to the conventional ring resonator methods is presented. This approach utilizes a `broadband' (relative to a monochromatic laser) light source such as a light emitting diode. Results are presented for both absorption and RI detection. While the demonstrated absorbance enhancement for surface-active analytes is theoretically anticipated, the observed RI sensitivity exceeds expectations. Due to multiple optical mechanisms that are simultaneously affected by an RI shift, detection limits on the order of 10-6 RIU (refractive index units) are presented using Fourier-transform based extraction of interference components from output spectra. Additional device characterizations are performed for a number of variables, including wall thickness, fabrication method, detector resolution, and dynamic range. Through study of these new methods, certain advantages become clear. While one is the ability to take absorbance and RI measurements with the same device, perhaps the most significant advantage is the compatibility these methods have with lower quality resonators, such as those which could be mass-produced. With these aspects in mind, potential absorption and RI based applications are probed further. Low-cost and/or portable devices are proposed, as well as improvements on classical analytical methods and biosensing applications.

Oates, Thomas Christopher

446

Sensitive refractive index detection using a broad-band optical ring resonator.  

PubMed

Broad-band operation is investigated as an alternative means of refractive index detection in an optical ring resonator. In this work, a liquid-core (LCORR, capillary-based) design is used. Optical ring resonators have been recently demonstrated for the detection of a wide variety of analytes, including DNA, viruses, proteins, chemical vapors, and pesticides. In the field of analytical chemistry, much of their value is in the ability to provide enhanced detection of surface analytes in small volumes. Conventional analysis methods that employ a single resonant wavelength and propagation mode are highly dependent on resonator quality. By utilizing the complex and variable response of a multiple-mode resonator and the simultaneous data of more than 40 resonance peaks, impressive results exceeding the single-mode prediction are produced from a very modest quality device. The presented methods also become attractive through the use of inexpensive LED light sources and common UV-vis spectrometers, as well as the ability to also take absorbance measurements without any physical configuration changes. Complex interference spectra are produced from the convolution of multiple wavelengths and modes. Two possible methods for analyzing this type of data are presented-one using Fourier transform deconvolution to extract resonance components from interference spectra, and another using chemometrics by constructing a partial least-squares model. Using isopropyl alcohol and water mixtures, detection limits are the order of 10(-6) RIU (refractive index units), comparable to existing ring resonators devices. To study surface detectability and biomolecule detection feasibility, surface adsorption of bovine serum albumin (BSA) is also analyzed. PMID:22924765

Oates, Thomas C; Burgess, Lloyd W

2012-09-18

447

Spatially confined and temporally resolved refractive index and scattering evaluation in human skin performed with optical coherence tomography  

NASA Astrophysics Data System (ADS)

In the present applications of optical coherence tomography (OCT), parameters besides pure morphology are evaluated in skin tissue under in vivo conditions. Spatially mapped refractive indices and scattering coefficients may support tissue characterization for research and diagnostic purposes in cosmetics/pharmacy and medicine, respectively. The sample arm of our OCT setup has been arranged to permit refractive index evaluation with little mechanical adjustment of a lens within the objective. A simple algorithm has been derived. Known from atmospheric work, the Klett algorithm has been applied to the same data set for retrieval of scattering coefficients. Both parameters have been measured in layered structures in skin like stratum corneum, epidermis and dermis. Significant water content in a localized sweat gland duct has been observed by refractive index evaluation. Time studies over 1.5 h permitted a first understanding about physiological changes in skin which are not obtainable by intrusive methods.

Knuettel, Alexander R.; Boehlau-Godau, Martin

2000-01-01

448

Compositional dependence of the nonlinear refractive index of new germanium-based chalcogenide glasses  

SciTech Connect

In this paper, we report results of n{sub 2} measurements of new chalcogenide glasses in the Ge-Sb-S-Se system using a modified Z-Scan technique. Measurements were made with picosecond pulses emitted by a 10 Hz Q-switched mode-locked Nd-YAG laser at 1064 nm under conditions suitable to characterize ultrafast nonlinearities. The nonlinear index increases up to 500 times the n{sub 2} of fused silica with an increase in the Ge/Se ratio and a decrease with an increase of the Ge/Sb ratio. We confirmed, using Raman spectroscopy, that the nonlinear refractive index depends on the number of Ge-S(Se) and Sb-S(Se) bonds in the glass network. Sulfide glasses were shown to have a nonlinear FOM near or <1, at 1064 nm. - Graphical abstract: In this paper, we report results of n{sub 2} measurements of new chalcogenide glasses in the Ge-Sb-S-Se system using a modified Z-Scan technique. n{sub 2} is found to increase with an increase of normalized photon energy, regardless of chalcogen type, but does not depend on the concentration of lone pair electron.

Petit, L., E-mail: lpetit@clemson.ed [School of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States); Carlie, N.; Chen, H.; Gaylord, S.; Massera, J. [School of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States); Boudebs, G. [Laboratoire des Proprietes Optiques des Materiaux et Applications, UMR CNRS 6163, Universite d'Angers, 2 Boulevard Lavoisier, 49045 Angers Cedex 01 (France); Hu, J.; Agarwal, A.; Kimerling, L. [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Richardson, K. [School of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States)

2009-10-15

449

PIV study of flow through porous structure using refractive index matching  

NASA Astrophysics Data System (ADS)

An aqueous solution of sodium iodide and zinc iodide is proposed as a fluid that matches the refractive index of a solid manufactured by rapid prototyping. This enabled optical measurements in single-phase flow through porous structures. Experiments were also done with an organic index-matching fluid (anisole) in porous structures of different dimensions. To compare experiments with different viscosities and dimensions, we employed Reynolds similarity to deduce the scaling laws. One of the target quantities of our investigation was the dissipation rate of turbulent kinetic energy. Different models for the dissipation rate estimation were evaluated by comparing isotropy ratios. As in many other studies also, our experiments were not capable of resolving the velocity field down to the Kolmogorov length scale, and therefore, the dissipation rate has to be considered as underestimated. This is visible in experiments of different relative resolutions. However, being near the Kolmogorov scale allows estimating a reproducible, yet underestimated spatial distribution of dissipation rate inside the porous structure. Based on these results, the model was used to estimate the turbulent diffusivity. Comparing it to the dispersion coefficient obtained in the same porous structure, we conclude that even at the turbulent diffusivity makes up only a small part of mass transfer in axial direction. The main part is therefore attributed to Taylor dispersion.

Häfeli, Richard; Altheimer, Marco; Butscher, Denis; Rudolf von Rohr, Philipp

2014-05-01

450

Terahertz subwavelength ribbon waveguide based plasmonic sensors for refractive index and thickness detection  

NASA Astrophysics Data System (ADS)

A terahertz plasmonic waveguide sensor is experimentally demonstrated to utilize surface waves propagated in a onedimension metal grating that constructed on a plastic ribbon waveguide. The grating conformation couples evanescent waves of a subwavelength terahertz waveguide onto the metal surface and highly confines the extended powers within ?/22-range for the phase-matching condition. The confined terahertz waveguiding waves resemble surface plasmonpolaritons but transmit with almost zero dispersion when the coupled surface waves interfere along the metal grating. Based on the dispersion-free guidance, there is Bragg reflection dominated by grating periods and strongly dependent on the refractive index of surface plasmon-polaritions. We successfully detect different thicknesses of polyethylene layers covered on the metal grating with thickness resolution of 1?m when the effective waveguide indices are modified in the vicinity of the metal grating, corresponding to 0.01-index variation. Potentially, terahertz subwavelength ribbon waveguide based plasmonic sensors could be manipulated to detect molecules with extremely low-density or small thickness in the metal-dielectric interface for probing pollution particles and any label-free detection.

You, Borwen; Lu, Ja-yu; Chang, Wei-Lun; Yu, Chin-Ping; Liu, Tze-An; Peng, Jin-Long

2012-03-01