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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

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

SciTech Connect

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

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

2009-04-10

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.

2011-05-02

6

The Refractive Index of Air  

Microsoft Academic Search

Present knowledge of the refractive index of air is reviewed. Regarding the absolute values there are as yet no definite indications that the standard adopted in 1953 on the basis of Barrell and Sears' measurements should be changed, but new experiments aiming at reducing the present uncertainty of about +\\/- 5 × 10-8 would be desirable. Several recent investigations have

Bengt Edlén

1966-01-01

7

Index of Refraction  

NSDL National Science Digital Library

Refraction is an important behavior of light that can be used to explain the operation of lenses, prisms, and optical fiber, as well as natural phenomena such as rainbows and mirages. The index of refraction, or refractive index, is defined as the ratio of the speed of light in a vacuum to the speed of light in a material. The index of refraction is an important property of optical materials and one that can be easily measured in the laboratory.This lesson begins with a video that introduces the concept of refraction. Students learn firsthand how when a wave of light travels from one medium to another, the change in the wave's speed leads to a change in its wavelength and the bending of the wave. Next, students investigate index of refraction through an interactive media asset, research, and a class discussion. Following a video about the index of refraction and Snell's law, students work in groups to conduct their own laboratory experiment to measure the index of refraction of gelatin (or plastic).Note: This is the first of two optics lesson plans. You may want to follow this lesson with the Fiber Optics Lesson Plan.

2012-05-24

8

Uniform Refraction in Negative Refractive Index Materials  

E-print Network

We study the problem of constructing an optical surface separating two homogeneous, isotropic media, one of which has a negative refractive index. In doing so, we develop a vector form of Snell's law, which is used to study surfaces possessing a certain uniform refraction property, both in the near and far field cases. In the near field problem, unlike the case when both materials have positive refractive index, we show that the resulting surfaces can be neither convex nor concave.

Gutierrez, Cristian E

2015-01-01

9

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

10

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

PubMed

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

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

2013-03-01

11

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

12

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

13

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

14

Index of Refraction without Geometry  

ERIC Educational Resources Information Center

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

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

2006-01-01

15

Negative Index of Refraction Mary (Betsey) Mathew  

E-print Network

Negative Index of Refraction Mary (Betsey) Mathew La Rosa, Winter 2006 #12;1 ABSTRACT In recent index of refraction materials. Negative index of refraction was an idea first theorized by Victor of refraction because I was amazed that such an apparently simple discovery could have been made only so lately

La Rosa, Andres H.

16

Refractive index of sodium iodide  

NASA Astrophysics Data System (ADS)

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

Jellison, G. E.; Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Ramey, L. A.; Singh, D. J.

2012-02-01

17

Negative Index of Refraction Portland State University  

E-print Network

Negative 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 which have a negative index of refraction, and this confused me. This was rather confusing to me

La Rosa, Andres H.

18

Simulation of refraction focusing using negative-refractive-index metamaterials  

Microsoft Academic Search

A realization of a negative-refractive-index (NRI) metamaterial uses a periodic structure with a unit cell composed of a capacitively loaded loop (CLL) and a conducting pole. This realization can lead to a lens mechanism with refraction focusing. This paper presents the results of a simulation of such refraction focusing using Ansoftpsilas HFSS. The simulation shows the return loss of a

Amir I. Zaghloul; Youn Lee

2008-01-01

19

THEORETICAL SCHEMES FOR NEGATIVE REFRACTION AND ENHANCED REFRACTIVE INDEX IN ATOMIC SYSTEMS  

E-print Network

THEORETICAL SCHEMES FOR NEGATIVE REFRACTION AND ENHANCED REFRACTIVE INDEX IN ATOMIC SYSTEMS and background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Origin of refractive index of refractive index enhancement . . . . . . . . . . . . . . . . . . . . . 10 2.1 Introduction

Yavuz, Deniz

20

Physics of negative refractive index materials  

Microsoft Academic Search

In the past few years, new developments in structured electromagnetic materials have given rise to negative refractive index materials which have both negative dielectric permittivity and negative magnetic permeability in some frequency ranges. The idea of a negative refractive index opens up new conceptual frontiers in photonics. One much-debated example is the concept of a perfect lens that enables imaging

S Anantha Ramakrishna

2005-01-01

21

Nonlinear refractive index of optical crystals  

Microsoft Academic Search

The nonlinear refractive indices (n2) of a large number of optical crystals have been measured at a wavelength near one micrometer with use of nearly degenerate three-wave mixing. The measurements are compared with the predictions of an empirical formula derived by Boling, Glass, and Owyoung. This formula, which relates n2 to the linear refractive index and its dispersion, is shown

Robert Adair; L. L. Chase; Stephen A. Payne

1989-01-01

22

Variation of corneal refractive index with hydration  

NASA Astrophysics Data System (ADS)

We report the effect of changes in the corneal hydration on the refractive index of the cornea. Using optical coherence tomography (OCT), the geometrical thickness and the group refractive index of the bovine cornea were derived simultaneously as the corneal hydration was varied. The corneal hydration was then calculated from the corneal thickness. The group refractive index of the cornea increased non-linearly as the cornea dehydrated. In addition, a simple mathematical model was developed, based on the assumption that changes in corneal hydration occur only in the interfibrilar space with constant water content within the collagen fibrils. Good agreement between the experimental results and the mathematical model supports the assumption. The results also demonstrate that the measurement of refractive index is a quantitative indicator of corneal hydration.

Kim, Young L.; Walsh, Joseph T., Jr.; Goldstick, Thomas K.; Glucksberg, Matthew R.

2004-03-01

23

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

24

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

25

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

26

Cosmology With A Dark Refraction Index  

E-print Network

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 FLRW 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 non-accelerating 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.

B. Chen; R. Kantowski

2009-02-23

27

A Liquid Prism for Refractive Index Studies  

NASA Astrophysics Data System (ADS)

A hollow glass prism filled with liquid becomes a "liquid prism". A simple method for constructing hollow glass prisms is presented. A method is given for a demonstration that uses the liquid prism with a laser or laser pointer so the audience can observe differences in refractive index for various liquids. The demonstration provides a quick and easy determination of the sugar content of soft drinks and juices. The prism makes it easy to determine a numerical value for the refractive index of a liquid.

Edmiston, Michael D.

2001-11-01

28

Measurement of corneal surface refractive index  

NASA Astrophysics Data System (ADS)

A technique has been devised for the measurement of surface refractive index of the cornea in human eyes. It has been shown to be effective in laboratory studies of refractive index in optical components of the eye. A modified approach is proposed, in which a much more accurate measurement may be achieved, with the added advantage of reduced patient discomfort. This is achieved by a non-contact method, and frequency-domain analysis of the optical signals used in the characterisation, which are optimised for best signal to noise ratio.

Pierscionek, Barbara K.; Green, Roger

2005-06-01

29

Plasmonic crystal enhanced refractive index sensing  

SciTech Connect

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

Stein, Benedikt; Devaux, Eloïse; Genet, Cyriaque, E-mail: genet@unistra.fr; Ebbesen, Thomas W. [ISIS and icRFC, University of Strasbourg and CNRS, 8 allée Gaspard Monge, 67000 Strasbourg (France)

2014-06-23

30

Nanofabrication of negative refractive index metasurfaces  

Microsoft Academic Search

We designed and fabricated planar metamaterial ‘particles’ (metasurfaces) intended to achieve negative effective refractive index in mid-infrared. We considered double split ring resonators (negative permeability particles) with additional capacitive gaps to compensate for the inertial inductance, as well as complementary double split rings (negative permittivity). We calculated dispersion relations and considered scaling conditions for our structures. For the fabrication of

Zoran Jakši?; Dana Vasiljevi?-Radovi?; Milan Maksimovi?; Milija Sarajli?; Aleksandar Vujani?; Zoran Djuri?

2006-01-01

31

Refractive index detector using Zeeman interferometry  

Microsoft Academic Search

We discuss the theory and error analysis for an ultrasensitive refractive index detector based on the two-frequency Zeeman effect laser. Experimental measurements on gases agree fairly well with predictions. With a 5-cm pathlength, the typical interferometry stability is Î{ital n}=8Ã10⁻⁹\\/h. Resolution is Î{ital n}=1Ã10⁻⁹.

Roger G. Johnston; W. Kevin Grace

1990-01-01

32

Dynamics of causal beam refraction in negative refractive index materials Steven A. Cummera)  

E-print Network

Dynamics of causal beam refraction in negative refractive index materials Steven A. Cummera on an interface between free space and a physically realizable negative refractive index material shows that negative refraction of finite beams does occur. A discontinuity in the phase normal direction

Cummer, Steven A.

33

Refraction in Media with a Negative Refractive Index S. Foteinopoulou,1  

E-print Network

Refraction in Media with a Negative Refractive Index S. Foteinopoulou,1 E. N. Economou,2 and C. M; published 13 March 2003) We show that an electromagnetic (EM) wave undergoes negative refraction at the interface between a positive and negative refractive index material, the latter being a properly chosen

34

Interferometric atmospheric refractive-index environmental monitor.  

PubMed

Long, open-path, outdoor interferometric measurement of the index of refraction as a function of wavelength (spectral refractivity) requires a number of innovations. These include active compensation for vibration and turbulence. The use of electronic compensation produces an electronic signal that is ideal for extracting data. This allows the appropriate interpretation of those data and the systematic and fast scanning of the spectrum by the use of bandwidths that are intermediate between lasers (narrow bandwidth) and white light (broad bandwidth). An Environmental Interferometer that incorporates these features should be extremely valuable in both pollutant detection and pollutant identification. Spectral refractivity measurements complement the information available from spectral absorption instruments (e.g., a Fourier-transform infrared spectrometer). The Environmental Interferometer currently uses an electronic compensating device with a 1-kHz response time, and therefore rapid spectral scans are feasibe so that it is possible to monitor the time evolution of pollutant events. PMID:21052132

Ludman, J E; Ludman, J J; Callahan, H; Caulfield, H J; Watt, D; Sampson, J L; Robinson, J; Davis, S; Hunt, A

1995-06-20

35

Integrated Refractive Index Optical Ring Resonator Detector for Capillary Electrophoresis  

E-print Network

Integrated Refractive Index Optical Ring Resonator Detector for Capillary Electrophoresis Hongying Engineering, 240D Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri 65211 a novel miniaturized and multiplexed, on- capillary, refractive index (RI) detector using liquid core

Fan, Xudong "Sherman"

36

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

37

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

38

Matched Index of Refraction Flow Facility  

SciTech Connect

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

2010-01-01

39

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

40

Scanning focused refractive-index microscopy  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

41

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

42

A spatial refractive index sensor using whispering gallery modes in an optically trapped microsphere  

E-print Network

We propose the use of an optically trapped, dye doped polystyrene microsphere for spatial probing of the refractive index at any position in a fluid. We demonstrate the use of the dye embedded in the microsphere as an internal broadband excitation source, thus eliminating the need for a tunable excitation source. We measured the full width at half maximum of the TE and TM resonances, and their frequency spacing as a function of the refractive index of the immersion fluid. From these relations we obtained an absolute sensitivity of 5e-4 in local refractive index, even when the exact size of the microsphere was not a priori known.

Zijlstra, P; Van der Molen, K L

2006-01-01

43

Microwave gain medium with negative refractive index  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

44

Microwave gain medium with negative refractive index.  

PubMed

Artificial effective media are attractive because of the fantastic applications they may enable, such as super lensing and electromagnetic invisibility. However, the inevitable loss due to their strongly dispersive nature is one of the fundamental challenges preventing such applications from becoming a reality. In this study, we demonstrate an effective gain medium based on negative resistance, to overcompensate the loss of a conventional passive metamaterial, meanwhile keeping its original negative-index property. Energy conservation-based theory, full-wave simulation and experimental measurement show that a fabricated sample consisting of conventional sub-wavelength building blocks with embedded microwave tunnel diodes exhibits a band-limited Lorentzian dispersion simultaneously with a negative refractive index and a net gain. Our work provides experimental evidence to the assertion that a stable net gain in negative-index gain medium is achievable, proposing a potential solution for the critical challenge current metamateiral technology faces in practical applications. PMID:25524752

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

2014-01-01

45

Extremely high refractive index terahertz metamaterials Muhan Choi1  

E-print Network

Extremely high refractive index terahertz metamaterials Muhan Choi1 , Seung Hoon Lee1 , Yushin Kim1 of refraction from large-area, freestanding, flexible terahertz metamaterials. In addition, two different types of high index metamaterials are proposed for polarization-insensitive effective refractive indices

Park, Namkyoo

46

Extremely High Refractive Index Terahertz Metamaterial Seung Hoon Lee1  

E-print Network

Extremely High Refractive Index Terahertz Metamaterial Seung Hoon Lee1 , Muhan Choi1 , Yushin Kim1 of refraction from large-area, freestanding, flexible terahertz metamaterials. The highest index of refraction of 33.22 is obtained from a multilayer metamaterial at a frequency of 0.851 THz. © 2011 Optical Society

Park, Namkyoo

47

Three-dimensional optical metamaterial with a negative refractive index  

E-print Network

LETTERS Three-dimensional optical metamaterial with a negative refractive index Jason Valentine1,2 Metamaterials are artificially engineered structures that have prop- erties, such as a negative refractive index1­4 , not attainable with naturally occurring materials. Negative-index metamaterials (NIMs) were

Cai, Long

48

Nonlinear refractive index coefficient for Nd phosphate laser glasses  

Microsoft Academic Search

Intensity-dependent changes in the refractive index of three low-index Nd phosphate laser glasses (LHG-5, LHG-6, EV-1) and one Nd fluorophosphate laser glass were measured at 1064 nm using time-resolved interferometry. The nonlinear refractive index coefficients of these phosphate glasses are all smaller than for Nd silicate laser glass (ED-2).

D. Milam; M. J. Weber

1976-01-01

49

Jamin interferometer for precise measurement of refractive index of gases  

NASA Astrophysics Data System (ADS)

Modified folded Jamin interferometer for on-line measurement of refractive index of gases was designed, constructed and tested. The accuracy of this interferometer is better than 10-6 and can be still approved about two orders by appropriate mathematical method. Interferometer is almost vibration insensitive with vibration noise equivalent to refractive index variation 2•10-9. The interferometer qualities were tested by air refractive index monitoring.

Sulc, Miroslav

2015-01-01

50

The Constants in the Equation for Atmospheric Refractive Index at Radio Frequencies  

Microsoft Academic Search

Recent improvements in microwave techniques have resulted in precise measurements which indicate that the conventional constants K1 = 79°K\\/mb and K22¿=4,800°K in the expression for the refractivity of air, N=(n-1) 106=[K1\\/T](p+ K2'e\\/T) should be revised. Various laboratories appear to have arrived at this conclusion independently. In much of radio propagation work the absolute value of the refractive index of the

ERNEST K. SMITH; Stanley Weintraub

1953-01-01

51

A particle mechanism for the index of refraction Marcel URBAN  

E-print Network

LAL 07-79 July 2007 A particle mechanism for the index of refraction Marcel URBAN LAL, Univ Paris experimental refractive indices. In our framework the optical Kerr phenomenon finds a very natural of refraction n, which is the ratio of the velocity of light in vacuum to its velocity in the medium. Molecules

Paris-Sud XI, Université de

52

Negative refraction without negative index in metallic photonic crystals  

E-print Network

Negative refraction without negative index in metallic photonic crystals Chiyan Luo, Steven G: It is shown that certain metallic photonic crystals can enable negative refraction and subwavelength imaging negative values of and µ," Sov. Phys. Usp. 10, 509-514 (1968). 5. J. B. Pendry, "Negative refraction makes

53

Index of Refraction and Snellâ??s Law  

NSDL National Science Digital Library

In this video from the ICT Center, learn about the index of refraction and Snellâ??s 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.

54

Refractive index investigations of nanoparticles dispersed in water  

NASA Astrophysics Data System (ADS)

The refractive index of nanoparticles dispersed in water is measured, using the total internal reflection method. The critical angle is determined by the disappearance of diffraction orders from a metal grating. The investigated nanoparticles are titanium dioxide (anatase phase), (35 nm diameter), zinc oxide, (<50 nm diameter), zirconium dioxide, (<100 nm diameter). The refractive index is measured with the experimental uncertainty of 1%. The Lorentz-Lorenz, Maxwell Garnett and Bruggeman relations are applied in the nanoparticle's refractive indices calculations.

Bodurov, I.; Yovcheva, T.; Sainov, S.

2014-12-01

55

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.

56

Strain induced bandgap and refractive index variation of silicon.  

PubMed

We present a study of the influence of high strain on the bandgap and the refractive index of silicon. The results of photoluminescence show that with the strain applied, the silicon bandgap can be adjusted to 0.84 eV and the refractive index of silicon increases significantly. 1.4% change of refractive index of silicon was observed. The strain-induced bandgap shrinkage and absorption coefficient change of silicon are considered as the main cause of the significant refractive index change. The present work indicates that the application of strain is promising to control the refractive index of silicon in devices so that applications such as compensation of thermal effect in optical devices can be achieved. PMID:23546100

Cai, Jingnan; Ishikawa, Yasuhiko; Wada, Kazumi

2013-03-25

57

Goniometer-spectrometer for index of refraction measurements from the near UV through the near IR  

NASA Astrophysics Data System (ADS)

The Ml I erWede Goni ometer-Spectrometer Model 2 is a medi urn-high accuracy instrument for the determination of prism angles and index of refraction in the visible wavelength range (400-700nrn) With its automatic Heidenhain rotary encoder the instrument is capab''e of absolute accuracy to I O arcsec for prism angle measurements and i x I 05 for index of refraction measurements. Recently we have developed a modified version of this instrument to provide absolute index of refraction measurements in the wavelength range from the UV through the near IR (254nm-2325 nm). The absolute accuracy for index of refraction measurements in the range is j INIRQDILTIQt4 The classical methods of Rudberg and Franhoer are still the most accurate means of determining the absolute index oT refraction or bulk optical materials. Both methods utilize a collimator and telescope pair which are both focused at inflnity. The former is normally flxed and the latter is mounted on a goniometer arm equipped with a precision graduated circle to provide absolute angular position of the telescope. The collimator is used to project the slit image o various spectral lines through a prism made from the material to be tested Usually spectral lamps are used for the light sources but lasers have also been used. The telescope and the sample prism are each rotated about the vertical axis of the goniometer so that each is set at proper angle to produce a minimum angle of deflection of the projected slit image with the desired wavelength. The goniometer arm and telescope are then fine-adjusted so that the slit image 32 / SPIE Vol. 1327 Properties and Characteristics of Optical Glass II (1990)

Ulbrich, Gerd J.; Trede, Jens

1990-10-01

58

Ultrasmall volume refractive index detection using microinterferometry  

NASA Astrophysics Data System (ADS)

A microinterferometric backscatter detector (MIBD) has been developed to perform subnanoliter volume refractive index measurements using a simple, folded optical train based on the interaction of a laser beam and a fused silica capillary tube. Positional changes of the interference pattern extrema (fringes) allow for the determination of ?n at the 10-7 level, corresponding to 5.3 pmole or 0.48 ng of solute, when thermal noise is controlled at 8×10-3 °C. MIBD is relatively path-length insensitive for capillaries ranging in inner diameter from 75 to 775 ?m, allowing a large range of detection volumes, from 350 pL to 40 nL, to be produced. A theoretical model of the microinterferometric backscatter detector has also been developed and evaluated and has been found to be in agreement with experimental data. This model indicates increased sensitivity of the instrument as the wavelength of the probe beam and the wall thickness of the capillary tube are reduced.

Swinney, Kelly; Markov, Dmitry; Bornhop, Darryl J.

2000-07-01

59

A new method for measuring the refractive index of glass  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

60

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

61

Novel methacrylated diamondoid to produce high-refractive index polymer  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

62

Charged-particle acceleration through decreasing refractive index  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

63

Transparent nanocomposites based on refractive index matched nanoparticles  

E-print Network

Transparent nanocomposites based on refractive index matched nanoparticles Katja Fröhlich1,2, Eleni-1015 Lausanne Objective: Transparent, scratch resistant nanocomposites Conclusion and Acknowledgement: Dispersed particles in a matched system. Nanocomposites The better the match of the refractive indices

Candea, George

64

Nondestructive Determination of Thickness and Refractive Index of Transparent Films  

Microsoft Academic Search

d, is given by d = (ANX)\\/(2p(cos r, - cos r,)), where X is the wavelength of the filtered light, ,.L is the refractive index, and AN is the number of fringes observed be- tween the angles of refraction r, and r,. This technique is especially suited for films thicker than one micron. Techniques are also described for obtaining accurate

W. A. Pliskin; E. E. Conrad

1964-01-01

65

Evolution of graded refractive index in squid lenses  

E-print Network

Evolution of graded refractive index in squid lenses Alison M. Sweeney1,*, David L. Des Marais1 be minimized. Squid lens S-crystallin proteins are evolution- arily derived from the glutathione S underlying the production and maintenance of camera-like optics in squid lenses. Keywords: graded refractive

Johnsen, Sönke

66

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

67

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

68

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

69

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

70

Interferometric atmospheric refractive index environmental monitor  

NASA Astrophysics Data System (ADS)

Conventional methods for detecting the release of foreign substances into the atmosphere are often slow, expensive, and only give an actual reading for a small section of the area of interest. The Environmental Interferometer can allow inexpensive, real time monitoring of a large area. The principle behind the Environmental Interferometer is the use of a fringe locked Michelson Interferometer scanning throughout a continuous range of colors at an intermediate bandwidth (50-100 nm). The fringe locking allows a the beam in a test arm to be reflected through a test area for about 1 kilometer of distance, while a reference arm is kept in a controlled environment (perhaps fiber optics or a multiple reflected air path) and retain a suitable interference pattern. The use of intermediate bandwidth light allows the central fringe to be located, and thus allows fast scanning through a continuous range of colors. Sampling at n different colors allows the discrimination of n different sources of optical pathlength change. This allows easy discrimination against moisture content change, air turbulence, ground vibrations, and the like, because of their characteristic pathlength change frequencies. The fringe locking allows for the electronic interpretation of a signal and enhances the accuracy of the instrumentation so that small optical pathlength changes can be easily measured and interpreted. A demonstration unit has been created using a 670 nm laser instead of a filtered white light source. Absolute index measurements of test gases injected into a 3 cm pollution chamber were made with the demonstration unit with errors of less than 1%. The fringe locker used in the demonstration unit was able to keep the fringe pattern stable during table oscillations, moderately fast introduction of test gases, and simulated air turbulence.

Ludman, Jacques E.; Ludman, Jacques J.; Callahan, Heidi; Caulfield, H. John; Watt, David W.

1995-09-01

71

Water absorption in a refractive index model for bacterial spores  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

72

Negative light refraction in a gradient medium with ultrasound-modulated refractive index  

NASA Astrophysics Data System (ADS)

The conditions of the formation of a spatially ordered optical structure with an ultrasound-modulated refractive index in a gradient medium have been considered. It has been shown that the excitation of a standing ultrasonic wave in the medium creates a structure consisting of trajectories of separate light beams, which is a superlattice of the "dynamic 4D photonic crystal." Regions corresponding to negative light refraction have been revealed in beam trajectories. Possible fields of application of such structures have been discussed.

Naimi, E. K.; Vekilov, Yu. Kh.

2015-01-01

73

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

74

Dual interferometer system for measuring index of refraction  

NASA Astrophysics Data System (ADS)

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

Goodwin, Eric Peter

75

Refractive index measurements by adaptive techniques (RIMDAPT: Phases 1 and 1A)  

Microsoft Academic Search

A method for the adaptive computation of ray traces directly without going through the intermediate step of determining refractive indices or refractive index gradients is demonstrated. The basis of the new method of direct ray tracing is presented together with an exposition of the inherent difficulty of using measured or computed refractive index or refractive index gradients for ray tracing

F. W. Vanstraten; R. L. Barron; R. F. Snyder

1974-01-01

76

Evaluation of the Refractive Index of Thin Transparent Polyethylene Terephthalatefilms  

NASA Astrophysics Data System (ADS)

The properties of refractive index and thickness in thin transparent films were evaluated many years ago utilizing various optical techniques. Many of the more modern techniques involved the measurement of various film properties using interferometry. Until the early 1980s, interferometers were generally prohibited from routinely operating in the visible light region due to the requirements for exacting alignment of many of the optical components. Despite the wealth of literature, the alignment of films with the dielectric axes for measurements of the refractive index and also polarized vibrational analysis, have not been considered. Additionally, most of these publications assume either a film thickness or a refractive index referenced from others work. The work presented herein details several methods that can be used to determine both the film thickness and the refractive indices of polyethylene terephthalate films. Results indicate that the polarization axes only coincidentally lie along the draw axis; no film studied in this work had an axis along the draw axis. The refractive indices for the minor and major axes were found to be 1.61 and 1.63, respectively.

Brangan, James R.

77

Non-Contact Measurements Of Refractive Index And Surface Curvature  

NASA Astrophysics Data System (ADS)

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

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

1989-01-01

78

Evaluation of the Refractive Index of Thin Transparent Polyethylene Terephthalatefilms  

Microsoft Academic Search

The properties of refractive index and thickness in thin transparent films were evaluated many years ago utilizing various optical techniques. Many of the more modern techniques involved the measurement of various film properties using interferometry. Until the early 1980s, interferometers were generally prohibited from routinely operating in the visible light region due to the requirements for exacting alignment of many

James R. Brangan

1991-01-01

79

ORIGINAL ARTICLE Quantifying the refractive index dispersion of a pigmented  

E-print Network

ORIGINAL ARTICLE Quantifying the refractive index dispersion of a pigmented biological tissue using of transparent tissues. Here, we extend the application of this method to pigmented, absorbing biological tissues's wings, with a thickness of 2.5 mm, contain a pigment with maximal absorption at 490 nm and a peak

80

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

81

Unidirectional transmission using array of zero-refractive-index metamaterials  

SciTech Connect

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

Fu, Yangyang; Xu, Lin; Hong Hang, Zhi; Chen, Huanyang, E-mail: chy@suda.edu.cn [School of Physical Science and Technology, Soochow University, Suzhou 215006 (China)

2014-05-12

82

Refractive index modification of polymers using nanosized dopants  

NASA Astrophysics Data System (ADS)

The addition of nanosized inorganic or organic dopants to polymers allows the modification of the polymers physical properties enabling the realization of functionalized polymers with new application fields e.g. in microoptics. Exemplarily electron rich organic dopants, solved in polymers, cause a pronounced increase of the refractive index. Polymer based reactive resins like PMMA, solved in MMA, or unsaturated polyester, solved in styrene, can be cured to thermoplastic polymers. The resin's low viscous flow behaviour enables an easy composite formation by solving the organic dopants in the liquid up to a dopant content of 50 wt%, followed by solidification to a thermoplastic. The addition of simple organic molecules like phenanthrene or benzochinoline allows a refractive index elevation at 633 nm from 1.56 up to 1.60 retaining the good transmission properties. In comparison the refractive index of PMMA can be increased from the initial value of 1.49 up to values around 1.58 (@633 nm). All composites show an almost linear correlation between dopant content and refractive index. Using these composites devices like 3dB-couplers or an electrooptical modulator applying injection molded or hot embossed substrates have been realized.

Hanemann, Thomas; Boehm, Johannes; Müller, Claas; Ritzhaupt-Kleissl, Eberhard

2008-04-01

83

Refractive index determination using an orthogonalized dispersion equation  

Microsoft Academic Search

An orthogonal form of a general three-term dispersion equation is presented which is useful for determination of the refractive index of transparent optical materials from measured spectral data. The orthogonal basis functions are dependent on the spectral range of the data and whether the spacing of the data is uniform with respect to wavelength or wavenumber. The application of the

C. K. Carniglia; K. N. Schrader; P. A. OConnell; S. R. Tuenge

1989-01-01

84

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

85

An updated equation for the refractive index of air  

NASA Astrophysics Data System (ADS)

Laser has been widely used in spectroscopic and metrological measurement. High-precision laser metrology is affected by the refractive index of air. In order to apply the algorithm for the refractive index of air in some situation where low calculation complexity and high-precision are needed, the algorithm of the refractive index of Rueger is updated. As the errors of Rueger's algorithm are mainly affected by temperature, humidity, and the concentration of carbon dioxide in the atmosphere as well as laser wavelength, we do some revisions about these effects of the factors of atmosphere in Rueger's algorithm. The conditions of standard air is redefined in this paper because of the average concentration of carbon dioxide in the atmosphere has been changed in the past few decades. As the concentration of carbon dioxide in the air is not constant, the effect of carbon dioxide on the refractive index of air is taken into consideration in the updated algorithm. The updated algorithm adapts to the real atmosphere well. The effects of dry air and humid air on the algorithm are also corrected, and the refractive index of air calculated by the updated algorithm is much closer to that of Philip E.Ciddor's algorithm defined as reference algorithm in the paper because of its high-precision. The performance of the updated algorithm is also analyzed in this paper. It is compared to that of the reference algorithm and the real measured data. Comparing results show that the performance of the algorithm has been improved after the correction. Comparing to the reference algorithm, the performance of the updated algorithm is a little bit lower, but the updated algorithm is much simpler and easier to be applied. Comparing to Rueger's algorithm, the performance of the updated algorithm is much higher and the complexity of the updated algorithm increases very small. The updated algorithm meets low calculation complexity and high-precision requirements.

Li, Wenchen; Dai, Zuoxiao; Dai, Ning; Chen, Ren; Sun, Xiaojie; Xia, Xiang; Li, Tao; Ma, Bei; Sheng, Hao

2014-12-01

86

hal-00186413,version1-9Nov2007 Index of refraction of gases for matter waves  

E-print Network

hal-00186413,version1-9Nov2007 Index of refraction of gases for matter waves: effect of the motion different formulae relating the index of refraction n of gases for atom waves to the scattering amplitude such an index was first introduced. We finally evaluate the index of refraction as a function of well known

Paris-Sud XI, Université de

87

Construction of refractive-index profiles of planar dielectric waveguides from the distribution of effective indexes  

Microsoft Academic Search

From a set of effective indexes, a continuous effective-index function is defined, which is then used to construct a refractive-index profile by numerically solving a WKB equation. The method applies to synthesis of profiles from prescribed propagation constants. Profiles for spatial image transmission are presented as an example. The method can also be applied to recovery of Smooth profiles from

K. Chiang

1985-01-01

88

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

89

Refractive index tensors in connection with problems of photon scattering  

NASA Astrophysics Data System (ADS)

In terms of the refractive index tensors N, the operator solving a problem of reflection and refraction of electromagnetic waves on plane boundary between isotropic dielectrics is given. Separately, the behaviour of Beltrami fields on the boundary is considered. They are described by infinite sets of branches of the traceless indefinite tensors N which are generators of involutive Maxwell groups for photon-antiphoton meeting pairs. The connections of the traceless tensors N with Fresnel reflection and transmission coefficients, Stokes relations, Beltrami fields and reflectional Coxeter's groups are established.

Barkovsky, L. M.; Furs, A. N.

1999-03-01

90

Calculation of three-dimensional refractive-index field using phase integrals  

Microsoft Academic Search

A simple method is proposed for the determination of three-dimensional refractive-index distributions of phase objects from interferograms. A given refractive index field has been treated to illustrate the method.

H.-G. Junginger; W. van Haeringen

1972-01-01

91

Refractive index of cubic zirconia stabilized with yttria.  

PubMed

The optical transmission and indices of refraction for the cubic isomorph of ZrO(2) stabilized with 12.0-mol % Y(2)O(3) were measured at various temperatures and for a range of wavelengths from 0.36 to 5.1 microm. Index data to +/-5 x 10(-5) were fitted to a three-term Sellmeier equation. The value of N(D) = 2.15847. The dispersion N(G) - N(B) = 0.06044, while that for N(c) - N(f) = 0.03455. The temperature coefficient of the refractive index between 20 and 130 degrees C varies from 1.6 x 10(-5)/K for 0.36-microm radiation to 0.62 x 10(-5)/K for 1.6-microm radiation. PMID:20396160

Wood, D L; Nassau, K

1982-08-15

92

Refractive index measurement of biological particles in visible region  

NASA Astrophysics Data System (ADS)

Optical cross-sections of biological warfare simulants, killed agents, and live agents are needed to assess the standoff detection performance of active lidar and passive FTIR systems. To aid in this investigation, Johns Hopkins University Applied Physics Laboratory (JHU/APL) has developed a technique to determine the index of refraction of biological materials in the visible region using a combination of transmission measurements and anomalous diffraction theory (ADT). The spectral measurements using a dual beam grating spectrometer provide a basis for calculating the optical cross section of suspended particles. ADT is then used to convert the cross section result into index of refraction. A summary of this procedure is described along with the results for silica microspheres and Bacillus globijii (BG). A comparison of these results to published data is also presented.

Limsui, D.; Carr, A. K.; Thomas, M. E.; Boggs, N. T.; Joseph, R. I.

2008-04-01

93

Transparent and colourless room temperature ionic liquids having high refractive index over 1.60.  

PubMed

Transparent and colourless ionic liquids with refractive index over 1.60 were synthesised by combining 1-benzyl-3-methylimidazolium or hexyltriphenylphosphonium cations with suitable anions. There is a positive relation between their refractive index and Kamlet-Taft parameters, especially dipolarity/polarisability, suggested as a potential parameter to design ionic liquids with high refractive index. PMID:25319716

Kayama, Yoko; Ichikawa, Takahiro; Ohno, Hiroyuki

2014-12-01

94

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

E-print Network

Sensors and Actuators B 123 (2007) 594­605 Fiber optic sensing of liquid refractive index Argha is immersed, to a high degree of precision and over a wide range of refractive index. The slope of sensor of the fiber. The sensitivity of the sensor to refractive index change is dependent on cladding thickness

95

Wave fields measured inside a negative refractive index metamaterial Steven A. Cummera)  

E-print Network

Wave fields measured inside a negative refractive index metamaterial Steven A. Cummera) and Bogdan versus position inside a wire/split ring resonator negative refractive index metamaterial are presented index metamaterial. © 2004 American Institute of Physics. [DOI: 10.1063/1.1823595] Negative refractive

Cummer, Steven A.

96

Investigation of holographic AgBr-films: optical density, Ag-concentration and index of refraction  

Microsoft Academic Search

In this note, measurements are presented on optical density, silver concentration, and index of refraction within uniformly exposed and processed holographic film. These data are important because they determine the diffraction efficiency of holograms. The silver analysis was performed by X-ray diffraction. The index of refraction was measured by a Brewster-angle method. The data show that the refractive index variation

J. Eichler; G. K. Ackermann; S. D. de Magalhães; O. D. Gonçalves; P. Rizzo

1995-01-01

97

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

E-print Network

Cosmology With A Dark Refraction Index B. Chen 1 , #3; and R. Kantowski 1, y 1 Homer L. Dodge Dept cosmologies by associating a refraction index with the cosmic uid. We then derive an expression for the accumulated e#11;ect of a refraction index on the distance redshift relations and #12;t the Hub- ble curve

Kantowski, Ron

98

High Frequency Limit of the Helmholtz Equation with Variable Refraction Index  

E-print Network

High 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 d , (1.1) where n(x) is the refraction index, # is a small parameter, and # # is a positive

Wang, Xue Ping

99

Optical Tomography for media with variable index of refraction STEPHEN MCDOWALL  

E-print Network

Optical Tomography for media with variable index of refraction STEPHEN MCDOWALL Abstract Optical of a medium M Rn . If the refractive index is constant throughout the medium, the steady-state case of variable refractive index where the dynamics are modeled by writing the transport equation in terms

McDowall, Stephen

100

Multiply ionized carbon plasmas with index of refraction greater than one  

E-print Network

Multiply ionized carbon plasmas with index of refraction greater than one J. FILEVICH,1 J. GRAVA,1 on the approximation that the index of refraction in plasmas is due solely to the free electrons. This general assumption makes the index of refraction always less than one. However, recent soft x-ray laser

Johnson, Walter R.

101

APS/123-PRL Observation of a multiply ionized plasma with index of refraction  

E-print Network

plasma with index of refraction greater than one J. Filevich, J.J. Rocca, and M.C. Marconi NSF ERC can dominate the index of refraction of laser-created plasmas at soft x-ray wavelengths. We report ions to the index of refraction. This usually neglected bound electron contribution can affect

Rocca, Jorge J.

102

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 for reconstructing the index of refraction of a medium from travel time measurements. The method is based on the so into account multiple arrival times naturally, while the Eulerian formulation for the index of refraction

Zhao, Hongkai

103

Negative Refractive Index in Left-Handed Materials  

Microsoft Academic Search

The real part of the refractive index n\\\\(omega\\\\) of a nearly transparent and passive medium is usually taken to have only positive values. Through an analysis of a current source radiating into a 1D ``left-handed'' material (LHM)-where the permittivity and permeability are simultaneously less than zero-we determine the analytic structure of n\\\\(omega\\\\), demonstrating frequency regions where the sign of Re[n\\\\(omega\\\\)

David R. Smith; Norman Kroll

2000-01-01

104

Light localization induced by a random imaginary refractive index  

NASA Astrophysics Data System (ADS)

We show the emergence of light localization in arrays of coupled optical waveguides with randomness only in the imaginary part of their refractive index and develop a one-parameter scaling theory for the normalized participation number of Floquet-Bloch modes. This localization introduces a different length scale in the decay of the autocorrelation function of a paraxial beam propagation. Our results are relevant to a vast family of systems with randomness in the dissipative part of their impedance spatial profile.

Basiri, A.; Bromberg, Y.; Yamilov, A.; Cao, H.; Kottos, T.

2014-10-01

105

Diffusion process effect on gradient refraction index of phosphate glasses  

NASA Astrophysics Data System (ADS)

For a few years, the Institute of Applied Optics have been conducting research leading to the development of GRIN lenses made of phosphate glass. Such lenses were obtained with the use of diffusion of sodium and lithium ions into phosphase glass including the silver ions, but the diameter of lenses was limited to few millimeters. Refractive index of lenses of 3-7 mm dia is expanded to the fourther exponent of the radius.

Kolacz, K.; Staronski, Leszek R.; Wychowaniec, Marek

2003-11-01

106

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, José M.; Santos, José L.; Frazão, Orlando

2012-01-01

107

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

108

Surface plasmon resonance based fiber optic refractive index sensors  

NASA Astrophysics Data System (ADS)

Refractive index sensors based on surface plasmon resonance (SPR) in a thin metal film deposited on an unclad core of a multimode fiber are presented. The sensing element of the fiber optic SPR sensors is a bare core of a step-index optical fiber made of fused silica with a double-sided sputtered gold film. First, an in-line transmissionbased sensing scheme with the fiber optic SPR probe is used. Second, a reflection-based sensing scheme with a terminated fiber optic SPR probe is employed. The fiber optic SPR probes have different lengths and the thickness of the sputtered gold film is about 50 nm. Both sensing schemes utilize a wavelength interrogation method so that the refractive index of a liquid is sensed by measuring the position of the dip in the transmitted or reflected spectral intensity distribution. As an example, the aqueous solutions of ethanol with refractive indices in a range from 1.333 to 1.364 are measured. For the transmission-based sensing scheme a polarization-dependent response is revealed.

Hlubina, Petr; Kadulova, Miroslava; Ciprian, Dalibor

2014-12-01

109

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

110

Analyzing refractive index profiles of confined fluids by interferometry.  

PubMed

This work describes an interferometry data analysis method for determining the optical thickness of thin films or any variation in the refractive index of a fluid or film near a surface. In particular, the method described is applied to the analysis of interferometry data taken with a surface force apparatus (SFA). The technique does not require contacting or confining the fluid or film. By analyzing interferometry data taken at many intersurface separation distances out to at least 300 nm, the properties of a film can be quantitatively determined. The film can consist of material deposited on the surface, like a polymer brush, or variation in a fluid's refractive index near a surface resulting from, for example, a concentration gradient, depletion in density, or surface roughness. The method is demonstrated with aqueous polyethylenimine (PEI) adsorbed onto mica substrates, which has a large concentration and therefore refractive index gradient near the mica surface. The PEI layer thickness determined by the proposed method is consistent with the thickness measured by conventional SFA methods. Additionally, a thorough investigation of the effects of random and systematic error in SFA data analysis and modeling via simulations of interferometry is described in detail. PMID:25365770

Kienle, Daniel F; Kuhl, Tonya L

2014-12-01

111

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

112

Refractive index in the viscous quark-gluon plasma  

NASA Astrophysics Data System (ADS)

Under the framework of the viscous chromohydrodynamics, the gluon self-energy is derived for the quark-gluon plasma with shear viscosity. The viscous chromoelectric permittivity and chromomagnetic permeability are evaluated from the gluon self-energy, through which the chromorefraction index is investigated. The numerical analysis indicates that the chromorefractive index becomes negative in some frequency range. The starting point for that frequency range is around the chromoelectric permittivity pole, and the chromomagnetic permeability pole determines the endpoint. As ?/s increases, the frequency range for the negative refraction becomes wider.

Jiang, Bing-feng; Hou, De-fu; Li, Jia-rong; Gao, Yan-jun

2013-08-01

113

Refractive index of glass and its dipersion for visible light.  

SciTech Connect

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

Smith, D. Y.; Karstens, W. (Physics); (Univ. of Vermont); (Saint Michael's Coll.)

2010-01-01

114

Improving retinal imaging by corneal refractive index matching.  

PubMed

Imaging the retina at high resolution requires a dilated pupil, which in turn exposes more corneal irregularities. We diminish the optical errors of the cornea by refractive index matching. Lens-fitted goggles were used for corneal immersion, to reduce its aberrations, while keeping the ocular power. An additional aspheric plate reduced the residual ocular spherical aberration. A comparison of the index-matching-based retinal images with those acquired directly shows resolution improvement for subjects with normal extent of ocular aberrations. A simulation of the point spread function, obtained from an averaged ocular and corneal wavefront error, also reveals substantial improvement when using corneal index matching. The demonstrated improvement using index matching may enable further improvement of current retinal imaging techniques or relaxing requirements for active ocular aberration correction. PMID:23455285

Meitav, N; Ribak, E N; Goncharov, A V

2013-03-01

115

Plasmonic nanoshell functionalized etched fiber Bragg gratings for highly sensitive refractive index measurements.  

PubMed

A novel fiber optical refractive index sensor based on gold nanoshells immobilized on the surface of an etched single-mode fiber including a Bragg grating is demonstrated. The nanoparticle coating induces refractive index dependent waveguide losses, because of the variation of the evanescently guided part of the light. Hence the amplitude of the Bragg reflection is highly sensitive to refractive index changes of the surrounding medium. The nanoshell functionalized fiber optical refractive index sensor works in reflectance mode, is suitable for chemical and biochemical sensing, and shows an intensity dependency of 4400% per refractive index unit in the refractive index range between 1.333 and 1.346. Furthermore, the physical length of the sensor is smaller than 3 mm with a diameter of 6 ?m, and therefore offers the possibility of a localized refractive index measurement. PMID:25680146

Burgmeier, Jörg; Feizpour, Amin; Schade, Wolfgang; Reinhard, Björn M

2015-02-15

116

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

117

CO2 laser induced refractive index changes in optical polymers.  

PubMed

We study the infrared photosensitivity properties of two optical polymer materials, benzocyclobutene (BCB) and epoxy OPTOCAST 3505, with a 10.6 ?m CO2 laser. We discover that the CO2 laser radiation can lower the refractive index of BCB by as much as 5.5 × 10(-3), while inducing no measurable index change in the epoxy. As confirmed by Fourier transform infrared spectroscopy, the observed index change in BCB can be attributed to photothermal modification of chemical bonds in the material by the CO2 laser radiation. Our findings open up a new possibility of processing polymer materials with a CO2 laser, which could be further developed for application in the areas of post-processing and direct-writing of polymer waveguide devices. PMID:22274379

Liu, Qing; Chiang, Kin Seng; Reekie, Laurence; Chow, Yuk Tak

2012-01-01

118

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

119

Tunable Metallic Photonic Crystals with an Effective Negative Index of Refraction  

E-print Network

Tunable Metallic Photonic Crystals with an Effective Negative Index of Refraction Mark S. Wheeler The design of negative refractive index (NRI) metamaterials is an exciting field of research, even though metamaterials [2-4]. Although in general PCs can produce "negative refraction" with and without BW behavior

Mojahedi, Mohammad

120

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 for reconstructing the index of refraction of a medium from travel time measurements. The method is based on the so of refraction allows us to compute the solution in physical space. Numerical examples including isotropic

Soatto, Stefano

121

Using plasma experiments to illustrate a complex index of refraction W. Gekelman and P. Pribyl  

E-print Network

Using plasma experiments to illustrate a complex index of refraction W. Gekelman and P. Pribyl of refraction for the propagation of a wave in a plasma depends on the plasma density, background magnetic field the subtleties involved in a complex media rather than in glass or water where the index of refraction is close

California at Los Angles, University of

122

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 for reconstructing the index of refraction of a medium from travel time measurements. The method is based on the so of refraction allows us to compute the solution in physical space. Numerical examples including isotropic

Uhlmann, Gunther

123

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

E-print Network

. Giraldo, and H. L. Leertouwer, "Butterfly wing colors: glass scales of Graphium sarpedon cause polarizedRefractive index and dispersion of butterfly chitin and bird keratin measured by polarizing the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive

124

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

125

Imprinting the nanostructures on the high refractive index semiconductor glass  

NASA Astrophysics Data System (ADS)

The centimeter range one- and two-dimensional nanostructures of 70 nm pitch have been imprinted by hot pressing with a quartz, silicon or nickel mold, at 240 °C, onto the surface of Ge 20As 20Se 14Te 46 semiconductor glass. Excellent glass stability of this glass allows multiple re-pressing of the nano-structures. With increasing the Te/Se ratio in the glass formula, the refractive index reaches a value of 3.5 with an option of free electron absorption at elevated temperatures pointing out the use of such nanostructures in submicron and micron scale electronic devices/chips, moth eye structures and photonic crystals.

Silvennoinen, M.; Paivasaari, K.; Kaakkunen, J. J. J.; Tikhomirov, V. K.; Lehmuskero, A.; Vahimaa, P.; Moshchalkov, V. V.

2011-05-01

126

Index of refraction of various gases for sodium matter waves  

SciTech Connect

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 (N{sub 2}, CO{sub 2}, NH{sub 3}, and H{sub 2}O). This determines the complex index of refraction for Na matter waves and, more accurately, the ratio of the real to the imaginary part of the forward scattering amplitude. These measurements are compared with several semiclassical scattering models.

Schmiedmayer, J.; Chapman, M.S.; Ekstrom, C.R.; Hammond, T.D.; Wehinger, S.; Pritchard, D.E. [Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); [Institut fuer Experimentalphysik, Universitaet Innsbruck, A-6020 Innsbruck (Austria)

1995-02-13

127

Tissue Refractive Index Fluctuations Report on Cancer Development  

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

Popescu, Gabriel

2012-02-01

128

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

2010-06-08

129

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

130

High refractive index sensitivity sensing in gold nanoslit arrays  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

131

X-ray refractive index of laser-dressed atoms  

NASA Astrophysics Data System (ADS)

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 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 transparency (EIT) for x rays on the Ar 1s?4p pre-edge resonance. We demonstrate that EIT in Ar allows one to imprint the shape of an ultrafast laser pulse on a broader x-ray pulse (duration 100ps , photon energy 3.2keV ). Our work thus opens new opportunities for research with hard x-ray sources.

Buth, Christian; Santra, Robin

2008-10-01

132

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

133

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

134

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

135

Investigation of negative refractive index in reciprocal chiral materials  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

136

Gas sensors for refractive index detection using surface plasmon resonance on nanosystem  

NASA Astrophysics Data System (ADS)

A plasmonic device for gas sensor is investigated for refractive index detection using surface plasmon resonance (SPR). The sensor device consists of nano-cavity antennas formed by metallic rectangular nanostrip array over a metal film, which monitors the changes of the refractive index by measuring the spectral shift of the resonance angle dip. The average detection sensitivity of the gas sensor is about 136 ° / RIU (refractive index units) for SPR excitation at 1550 nm telecommunication wavelength.

Zhao, Hua-Jun; Tian, Yong-You; Lei, Ju-Hua

2014-07-01

137

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

138

Gradient Refractive Index Optics IOL: Theoretical Background and Clinical Results  

PubMed Central

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

Malyugin, Boris; Morozova, Tatiana; Cherednik, Valentin

2014-01-01

139

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

140

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

141

Anal. Chem. 1995, 67,3767-3774 Variable Index of Refraction Ultrathin Films  

E-print Network

Anal. Chem. 1995, 67,3767-3774 Variable Index of Refraction Ultrathin Films Formedfrom Self[(p-phenylene)methylenelbis(phosphonate)(AZO). Byvaryingthe ratio of DBP toAZO monolayersin the ZP multilayer film,the indexof refraction canbe controlled of refraction of the ZP multilayerson transparent substrates. ZPfilmsconsistingof 100%DBP and 100% AZO

142

Photonic bandgap engineering with inverse opal multistacks of different refractive index contrasts  

E-print Network

Photonic bandgap engineering with inverse opal multistacks of different refractive index contrasts but from materials with different refractive indices. Al2O3, ZnO, and TiO2 are infiltrated into opal templates by atomic layer deposition. Stacking multiple inverse opal structures with different refractive

Cao, Hui

143

Spatially varying index of refraction: An open ended undergraduate topic  

SciTech Connect

There are many commonplace examples of waves moving along a curved path in an inhomogeneous media. There are reports of a simple lecture demonstration of light bending in a sugar solution being used to motivate students in physics, geophysics, and acoustics courses. For those students who wish to pursue this topic we discuss many avenues of additional research. With relatively simple equipment one can measure the index of refraction n (y,t) and its first and second spatial derivatives as well as the time dependence. The analysis can be approached from a generalization of Snell's law, the equations for the eikonal, Fermat's principle, and the classical approximation and analogies with trajectories of particles.

Krueger, D.A.

1980-03-01

144

Scattering and refractive index properties of skin obtained with OCT  

NASA Astrophysics Data System (ADS)

Optical Coherence Tomography (OCT) provides more parameters than pure morphology does. In a recent paper we have shown that the refractive index (RI) can be evaluated in a localized manner in skin tissue under in vivo conditions. Further evaluation provides scattering parameters (scatter width) of turbid materials down to penetration depths of some 100 ?m. Measurements have been done in vitro in pig skin and in vivo in human skin with our OCT scanner SkinDex 300. The parameters RI and scatter width may have a viable impact on skin research and clinical diagnoses. In addition, we demonstrate the breakdown of the ballistic light propagation in turbid material and tissue due to multiple forward scattering.

Knuettel, Alexander R.; Bonev, Slavtcho M.; Knaak, W.

2003-10-01

145

Inline fiber interference-based refractive-index sensor  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

146

Aerodynamically efficient gradient refractive index missile seeker lens  

NASA Astrophysics Data System (ADS)

This thesis explores the use of a pointed seeker lens designed using a spherically symmetric gradient refractive index (GRIN). The design helps to solve the current design conflict between optical quality and aerodynamic drag inherent in hemispherical seeker lenses. Equations for lens design and the evaluation of off-axis lens performance have been developed for both a homogeneous version an d a GRIN version of the pointed seeker lens. The homogeneous lens is used as a comparison and a check for the GRIN lens. A FORTRAN program (GISL) has been written and employed to evaluate and compare both the homogeneous lens and many different configurations of possible GRIN lens designs. Results indicate that the GRIN lens has highly superior off-axis imaging performance as compared to the homogeneous lens. The best results were obtained for the GRIN lens with a fifty percent, positive, spherically symmetric gradient index with center of symmetry interior to the lens. Only very slightly inferior performance was observed with a five percent version of the same lens; such a lens possible can be manufactured today.

Carr, H. M., III

1982-10-01

147

High-negative effective refractive index of silver nanoparticles system in nanocomposite films  

NASA Astrophysics Data System (ADS)

We have proved on the basis of the experimental optical reflection and transmission spectra of the nanocomposite film of poly(methyl methacrylate) with silver nanoparticles that (PMMA + Ag) nanocomposite films have quasi-zero refractive indices in the optical wavelength range. We show that to achieve quasi-zero values of the complex index of refraction of composite materials is necessary to achieve high-negative effective refractive index in the system of spherical silver nanoparticles.

Altunin, Konstantin K.; Gadomsky, Oleg N.

2012-03-01

148

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

PubMed

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

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

2014-05-21

149

Refractive index and density in F- and Cl-doped silica glasses  

SciTech Connect

The refractive index and density of fluorine- and chlorine-doped silica glasses were measured as functions of fictive temperature. The halogen concentrations were observed to have a refractive index or density that is independent of the fictive temperature were found. This implies that these properties are not affected by any heat-treatment conditions.

Kakiuchida, Hiroshi; Shimodaira, Noriaki; Sekiya, Edson H.; Saito, Kazuya; Ikushima, Akira J. [Research Center for Advanced Photon Technology, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya, Aichi 468-8511 (Japan); Research Center for Advanced Photon Technology, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya, Aichi 468-8511, Japan and Research Center, Asahi Glass Co., Ltd., 1150 Hazawa-cho, Kanagawa, Yokohama, Kanagawa 221-8755 (Japan); Research Center for Advanced Photon Technology, Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya, Aichi 468-8511 (Japan)

2005-04-18

150

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

151

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

152

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

153

Dependence of tissue optical properties on solute-induced changes in refractive index and osmolarity  

Microsoft Academic Search

Additions of a solute\\/carbohydrate in tissue affect the size of tissue cells and the refractive indexes of the extra- and intracellular fluids, and thus the overall tissue scattering properties. We use both the Rayleigh-Gans and Mie theory approximation in calculating effects of the osmolarity and refractive indexes on the reduced scattering coefficient of tissue, and employ photon diffusion theory to

Hanli Liu; Bertrand Beauvoit; Mika Kimura; Britton Chance

1996-01-01

154

Dynamics of the refraction index in a water-lecithin mixture  

NASA Astrophysics Data System (ADS)

The effect of lecithin concentration on behavior of refractive index of perturbed water-lecithin system is investigated using a polarization interferometer. It is found that the time variations of the refractive index for different lecithin concentrations can be sued to assess the state of the lecithin in water, i.e. detect micelles, single and double molecular layers, etc.

Maksimyak, Peter P.

1997-12-01

155

Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating  

Microsoft Academic Search

In this paper, we present a novel fiber optic sensor for the simultaneous measurement of liquid level and surrounding refractive index based on tilted fiber Bragg grating (TFBG). The transmission loss and the bandwidth of cladding modes are two measures of the liquid level, while their resonance wavelengths are employed to determine the surrounding refractive index. A liquid level sensitivity

Qi Jiang; Debo Hu; Meng Yang

2011-01-01

156

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

157

Simultaneous temperature and refractive index measurements using a 3° slanted multimode fiber Bragg grating  

Microsoft Academic Search

A novel and simple sensor based on a 3° slanted multimode fiber Bragg grating (MFBG) for simultaneous temperature and refractive index measurement is demonstrated. The 3° slanted MFBG shows two wavelength groups in its transmission spectrum: One group, due to the coupling from one core mode to cladding modes, is sensitive to both surrounding refractive index (SRI) and temperature and

Chun-Liu Zhao; Xiufeng Yang; M. S. Demokan; W. Jin

2006-01-01

158

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

Microsoft Academic Search

Experiments studying cardiovascular geometries require a working fluid that matches the high index of refraction of glass and silicone, has a low viscosity, and is safe and inexpensive. A good candidate working fluid is diethyl phthalate (DEP), diluted with ethanol. Measurements were made of index of refraction and viscosity of varied dilutions at a range of temperatures, and empirical models

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

2006-01-01

159

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

PubMed

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

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

2014-03-31

160

Theoretical study of polarization insensitivity of carrier-induced refractive index change of multiple quantum well.  

PubMed

Characteristics of polarization insensitivity of carrier-induced refractive index change of 1.55 ?m tensile-strained multiple quantum well (MQW) are theoretically investigated. A comprehensive MQW model is proposed to effectively extend the application range of previous models. The model considers the temperature variation as well as the nonuniform distribution of injected carrier in MQW. Tensile-strained MQW is expected to achieve polarization insensitivity of carrier-induced refractive index change over a wide wavelength range as temperature varies from 0°C to 40°C, while the magnitude of refractive index change keeps a large value (more than 3 × 10-3). And that the polarization insensitivity of refractive index change can maintain for a wide range of carrier concentration. Multiple quantum well with different material and structure parameters is anticipated to have the similar polarization insensitivity of refractive index change, which shows the design flexibility. PMID:25607157

Miao, Qingyuan; Zhou, Qunjie; Cui, Jun; He, Ping-An; Huang, Dexiu

2014-12-29

161

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

162

Sensing of refractive index based on mode interference in a five-layer slab waveguide  

NASA Astrophysics Data System (ADS)

We propose a refractive index sensor based on the mode interference in a five-layer waveguide. The propagation properties are analyzed by the coupled mode theory, and the function of the waveguide as a refractive index sensor is also explored based on simulation results. Taking into consideration a trade-off between the sensitivity and the size of the proposed sensor, we can get a very compact device of 10.8 ?m×1 ?m, and the sensing resolution of the proposed refractive index can reach 2.25×10-5 RIU for index change at around 1.455.

Tang, Tingting; Ma, Wenying; Liu, Wenli; He, Xiujun

2015-01-01

163

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

164

On the Distribution of Protein Refractive Index Increments  

PubMed Central

The protein refractive index increment, dn/dc, is an important parameter underlying the concentration determination and the biophysical characterization of proteins and protein complexes in many techniques. In this study, we examine the widely used assumption that most proteins have dn/dc values in a very narrow range, and reappraise the prediction of dn/dc of unmodified proteins based on their amino acid composition. Applying this approach in large scale to the entire set of known and predicted human proteins, we obtain, for the first time, to our knowledge, an estimate of the full distribution of protein dn/dc values. The distribution is close to Gaussian with a mean of 0.190 ml/g (for unmodified proteins at 589 nm) and a standard deviation of 0.003 ml/g. However, small proteins <10 kDa exhibit a larger spread, and almost 3000 proteins have values deviating by more than two standard deviations from the mean. Due to the widespread availability of protein sequences and the potential for outliers, the compositional prediction should be convenient and provide greater accuracy than an average consensus value for all proteins. We discuss how this approach should be particularly valuable for certain protein classes where a high dn/dc is coincidental to structural features, or may be functionally relevant such as in proteins of the eye. PMID:21539801

Zhao, Huaying; Brown, Patrick H.; Schuck, Peter

2011-01-01

165

Optical polymers with tunable refractive index for nanoimprint technologies  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

166

Index of Refraction Measurements Using a Laser Distance Meter  

ERIC Educational Resources Information Center

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…

Ochoa, Romulo; Fiorillo, Richard; Ochoa, Cris

2014-01-01

167

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 of the reconstruction of the individual contributions and the overall altitude pro- file of the refraction index of air reserved. Keywords: Electro-optical lidar; Electro-optical Kerr effect; Refraction index; Statistically

168

EXACT EXPRESSIONS AND ACCURATE APPROXIMATIONS FOR THE DEPENDENCES OF RADIUS AND INDEX OF REFRACTION OF SOLUTIONS OF  

E-print Network

EXACT EXPRESSIONS AND ACCURATE APPROXIMATIONS FOR THE DEPENDENCES OF RADIUS AND INDEX OF REFRACTION and index of refraction, and for aerosol particles that are hygroscopic, both of these quantities vary to the volume-equivalent dry radius) and index of refraction on RH for aqueous solutions of single solutes. Both

169

Pilon's Lab UCLA www.seas.ucla.edu/~pilon/ Refraction and absorption index of Chlamydomonas reinhardtii and its mutants  

E-print Network

Pilon's Lab ­ UCLA www.seas.ucla.edu/~pilon/ Refraction and absorption index of Chlamydomonas,k Wavelength, (nm) #12;Pilon's Lab ­ UCLA www.seas.ucla.edu/~pilon/ Refraction and absorption index.040 0.045 0.050 Numberfrequency Equivalent diameter, ds (m) CC125 (nm) Refraction index, n Absorption

Pilon, Laurent

170

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

171

Self-organization of dissipationless solitons in positive- and negative-refractive-index materials  

NASA Astrophysics Data System (ADS)

A generalized Ginzburg-Landau equation describing dissipative solitons dynamics in negative-refractive-index materials is derived from Maxwell equations. This equation having only real terms with opposite sign differs from the usual Ginzburg-Landau equation for positive-refractive-index media. A cross-compensation between the saturating nonlinearity excess, losses, and gain makes obtained self-organized solitons dissipationless and exceptionally robust. In the presence of such solitons medium becomes effectively dissipationless. The compensation of losses is of particular interest for media with resonant character of interactions like negative-refractive-index materials.

Skarka, V.; Aleksi?, N. B.; Berezhiani, V. I.

2010-04-01

172

A microfluidic refractive index sensor based on an integrated three-dimensional photonic crystal  

NASA Astrophysics Data System (ADS)

We present the concept of using three-dimensional photonic crystals for refractive index sensing in a microfluidic channel. The sensors are based on a three-dimensional void channel photonic crystal fabricated by femtosecond laser writing in a polymer substrate. It is demonstrated that a change in the refractive index of the fluid in the microchannel results in a shift in the band gap or band gap defect position of the photonic crystal. According to Fourier transform infared spectroscopy of the photonic crystal sensor, a change of 6×10-3 in the refractive index of the fluid can be detected.

Wu, Jing; Day, Daniel; Gu, Min

2008-02-01

173

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

174

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

SciTech Connect

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

Chen Jihuan; Zhao Jiarong; Huang Xuguang; Huang Zhenjian

2010-10-10

175

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

NASA Technical Reports Server (NTRS)

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

Siegel, R.; Spuckler, C. M.

1992-01-01

176

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

177

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

NASA Astrophysics Data System (ADS)

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

Luetjen, Christopher; Hallsted, Jonathan; Kleinert, Michaela

2013-12-01

178

Refractive index measurements of double-cylinder structures found in natural spider silks  

NASA Astrophysics Data System (ADS)

The silks of Orb-Weaver spiders (family Araneidae) are emerging as fascinating optical materials due to their biocompatibility, ecological sustainability and mechanical robustness. Natural spider silks are mainly spun as double cylinders, with diameters ranging from 0.05 to 10 ?m, depending on the species and maturity of the spider. This small size makes the silks difficult to characterize optically with traditional techniques. Here, we present a technique that is capable of measuring both the real and imaginary refractive index components of spider silks. This technique is also a new capability for characterizing micro-optics more generally. It is based on the measurement and analysis of refracted light through the spider silk, or micro-optic, while it is immersed in a liquid of known refractive index. It can be applied at any visible wavelength. Results at 540 nm are reported. Real refractive indices in the range of 1.54-1.58 were measured, consistent with previous studies of spider silks. Large silk-to-silk variability of the p-polarized refractive index was observed of around 0.015, while variability in the s-polarized refractive index was negligible. No discernible difference in the refractive indices of the two cylinders making up the double cylinder silk structure were observed. Measured imaginary refractive indices corresponded to an optical loss of around 14 dB/mm at 540 nm.

Little, Douglas J.; Kane, Deb M.

2014-05-01

179

Removing index of refraction constraints in the optical measurement of liquid level  

Microsoft Academic Search

Continuous and discrete liquid level measurements made with fiber optic sensors generally depend on refraction of light in the liquid to be measured. Problems, including erratic or incorrect readings, arise when the index of refraction of the liquid is near that of the outer surface of the optical probe. This is often the case for common optical probe materials and

Lee A. Danisch

1993-01-01

180

Direction dependency of extraordinary refraction index in uniaxial nematic liquid crystals  

E-print Network

The article presents a straightforward experiment that directly and illustratively demonstrates double refraction. For this purpose, two liquid crystalline cells were designed, which enable qualitative and quantitative measurements of the extraordinary refractive index direction dependency in a uniaxial nematic liquid crystal.

Jerneja Pavlin; Natasa Vaupotic; Mojca Cepic

2012-11-06

181

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

Microsoft Academic Search

We identify a route towards achieving a negative index of refraction at optical frequencies based on coupling between plasmonic waveguides that support backwards waves. We show how modal symmetry can be exploited in metal-dielectric waveguide pairs to achieve negative refraction of both phase and energy. Control of waveguide coupling yields a metamaterial consisting of a one-dimensional multilayer stack that exhibits

Ewold Verhagen; René de Waele; L. Kuipers; Albert Polman

2010-01-01

182

Refractive index of sapphire at 532 nm under shock compression and release  

NASA Astrophysics Data System (ADS)

The refractive index of sapphire at 532 nm has been determined along the Z axis over a range of conditions produced in shock compression and release experiments. In these experiments, a laser interferometer is used to measure particle velocity at an interface with a sapphire window. Values for refractive index are found from velocity corrections that must be made to account for refractive-index changes in the window due to shock wave motion. Early studies found that Z-cut sapphire windows resulted in much larger corrections than other window materials. These studies examined refractive-index changes at a wavelength of 633 nm, corresponding to the helium-neon lasers typically used in interferometers at that time. Because of the high shock impedance of sapphire, its use as an interferometer window since the early studies has been limited. Recent interest in the shock response of high-impedance ceramics, however, has resulted in considerable use of sapphire windows in experiments using laser interferometers operating at a wavelength of 532 nm. The current study is a careful re-examination of the refractive index of Z-cut sapphire under shock compression and release at this wavelength. As in the earlier work, symmetric-impact experiments were conducted on a gas gun facility using sapphire discs cut with their faces normal to the Z axis of the crystal. Laser interferometer measurements were made under known conditions to find the necessary velocity corrections as a function of the shocked state. A method used previously for analyzing refractive-index effects was used to determine refractive index as a function of the shocked state during single-shock motion, then extended to later events involving additional wave motions within the window. The current refractive-index measurements show a simple, linear dependence on density in the shocked state, in contrast to a more complicated dependence found previously. This difference is shown to be a consequence of small changes in the measured velocity corrections. The polarizability behavior is also examined using the present results, indicating a near balance between refractive-index changes due strictly to increasing density and those resulting from polarizability changes in the shocked state. An analysis using available sapphire data on refractive-index changes during hydrostatic compression and isobaric heating indicates that the temperature dependence of the polarizability has a relatively small effect on the changes in refractive index during shock compression. Together with the linear index-density relation, this indicates that a simple velocity correction found for single-shock motion can be accurately applied to arbitrary wave motions within sapphire windows.

Setchell, Robert E.

2002-03-01

183

Photoacoustic measurement of refractive index of dye solutions and myoglobin for biosensing applications  

PubMed Central

Current methods of determining the refractive index of chemicals and materials, such as ellipsometry and reflectometry, are limited by their inability to analyze highly absorbing or highly transparent materials, as well as the required prior knowledge of the sample thickness and estimated refractive index. Here, we present a method of determining the refractive index of solutions using the photoacoustic effect. We show that a photoacoustic refractometer can analyze highly absorbing dye samples to within 0.006 refractive index units of a handheld optical refractometer. Further, we use myoglobin, an early non-invasive biomarker for malignant hyperthermia, as a proof of concept that this technique is applicable for use as a medical diagnostic. Comparison of the speed, cost, simplicity, and accuracy of the techniques shows that this photoacoustic method is well-suited for optically complex systems. PMID:24298407

Goldschmidt, Benjamin S.; Mehta, Smit; Mosley, Jeff; Walter, Chris; Whiteside, Paul J. D.; Hunt, Heather K.; Viator, John A.

2013-01-01

184

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

E-print Network

Targeted alteration of real and imaginary refractive index of biological cells by histological of epithe- lial cells caused by histological stains such as hematox- ylin and eosin-containing cytostain. We

Ottino, Julio M.

185

Precision interferometric measurements of refractive index of polymers in air and liquid  

NASA Astrophysics Data System (ADS)

We have developed a procedure for precise measurement of the group refractive index for materials in air and liquid environments, using a low coherence interferometer. For example, in manufacturing of soft contact lenses, the lenses are always kept hydrated in a saline solution. Knowing accurate refractive index of the lens is important to metrology and quality control purposes. The small refractive index difference between the liquid and the lens makes such tasks especially challenging. The developed procedure allows us to obtain measurement repeatability for group refractive index less than 1 x 10-3 for materials with thicknesses on the order of 100 microns, when measured in liquid. The measurement repeatability further improves for measurements in air, or for thicker materials.

Marcus, Michael A.; Hadcock, Kyle J.; Gibson, Donald S.; Herbrand, Matthew E.; Ignatovich, Filipp V.

2013-09-01

186

Measurement of the refractive index of liquid xenon for intrinsic scintillation light  

Microsoft Academic Search

Measurement of the refractive index of liquid xenon (LXe) for intrinsic scintillation light was carried out. The value obtained at ? = 180 nm is equal to 1.5655 ± 0.0024 ± 0.0078 for the xenon triple point.

L. M Barkov; A. A Grebenuk; N. M Ryskulov; P. Yu Stepanov; S. G Zverev

1996-01-01

187

Intersubband optical absorption coefficients and refractive index changes in modulation-doped asymmetric double quantum well  

NASA Astrophysics Data System (ADS)

The linear and the third-order nonlinear optical absorption coefficients and refractive index changes in a modulation-doped asymmetric double quantum well are studied theoretically. The electron energy levels and the envelope wave functions in this structure are calculated by the Schrödinger and Poisson equations self-consistently in the effective mass approximation. The analytical expressions of optical properties are obtained by using the compact density-matrix approach. In this regard, the linear, nonlinear and total intersubband absorption coefficients and refractive index changes are investigated as a function of right-well width ( Lw2) of asymmetric double quantum well. Our results show that the total absorption coefficients and refractive index changes shift toward higher energies as the right-well width decreases. In addition, the total optical absorption coefficients and refractive index changes is strongly dependent on the incident optical intensity.

Ungan, F.; Kasapoglu, E.; Sokmen, I.

2011-10-01

188

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

189

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

190

Bistability of the refractive index due to parametric resonance in crystals  

Microsoft Academic Search

It is shown that the nonlinear refractive index of a crystal interacting with a biharmonic optical field exhibits bistability due to the process of parametric resonant generation of the coherent overtone vibration.

B. Ratajska-Gadomska; W. Gadomski

1986-01-01

191

Origin of the refractive-index increase in laser-written waveguides in glasses  

SciTech Connect

We present firm evidence that the mechanism for the refractive-index increase in fused silica caused by irradiation with ultrafast intense laser pulses is the densification of glass. This conclusion is based on the correlation observed between the refractive-index values in waveguides in silica produced by focused femtosecond laser pulses and the shift of the central frequency of {omega}{sub 4} (TO) band (Si-O stretching mode) in micro-Raman spectra. These data were compared with the relation of the Raman shift to density and to refractive index changes in glasses modified by high pressure or irradiation. We conclude that the measured refractive-index increase in silica waveguides can be explained by densification of glass and exclude other hypothesis such as fictive-temperature effect, color center formation, etc.

Ponader, Carl W.; Schroeder, Joseph F.; Streltsov, Alexander M. [Corning Inc., Corning, New York 14831 (United States)

2008-03-15

192

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

193

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

194

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

195

Surface antireflection properties of GaN nanostructures with various effective refractive index profiles.  

PubMed

GaN nanostructures with various effective refractive index profiles (Linear, Cubic, and Quintic functions) were numerically studied as broadband omnidirectional antireflection structures for concentrator photovoltaics by using three-dimensional finite difference time domain (3D-FDTD) method. Effective medium theory was used to design the surface structures corresponding to different refractive index profiles. Surface antireflection properties were calculated and analyzed for incident light with wavelength, polarization and angle dependences. The surface antireflection properties of GaN nanostructures based on six-sided pyramid with both uniform and non-uniform patterns were also investigated. Results indicate a significant dependence of the surface antireflection on the refractive index profiles of surface nanostructures as well as their pattern uniformity. The GaN nanostructures with linear refractive index profile show the best performance to be used as broadband omnidirectional antireflection structures. PMID:25607159

Han, Lu; Zhao, Hongping

2014-12-29

196

A band-to-band Coulomb interaction model for refractive index spectra of ternary semiconductors  

NASA Astrophysics Data System (ADS)

A band-to-band Coulomb interaction model for the refractive index spectra is presented of AlxGa1-xAs for 0refractive index near band-edge region through a complete closed-form Kramers-Kronig transform. In addition, a Sellmeier-type single-oscillator representation provides all the additional absorption at higher energies due to nonparabolicity and higher-energy bands. The refractive index spectra are extended beyond the band-gap energy and are in excellent agreement with the available experimental data. The refractive index spectra of ternary compounds are fully parametrized by interpolation of the fitting parameters. The results will be important for the detailed design of photonic devices, such as electroabsorption modulators and semiconductor optical amplifiers.

Lin, E. Y.; Lay, T. S.

2009-01-01

197

Manipulation of light beam propagation in one-dimensional photonic lattices with linear refractive index profile  

NASA Astrophysics Data System (ADS)

We use Bloch oscillations to demonstrate potential light beam propagation control in photonic lattices with linear refractive index change in transverse direction. It is qualitatively investigated how composite photonic lattice systems with varied values of refractive index gradient and nonlinearity strength along the propagation direction can be used to perform different functions, such as beam splitting and switching, in future components of all-optical networks. Additionally, we demonstrate the robustness of Bloch oscillations to nonlinearity and disorder in the proposed setup.

Radosavljevi?, Ana; Gligori?, Goran; Maluckov, Aleksandra; Stepi?, Milutin

2015-01-01

198

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

199

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.; Hernández-Figueroa, Hugo E.

2011-01-01

200

Broadband Anti-Reflective Structure with Mesoporous Silica of Low Refractive Index in Si Solar Panels  

Microsoft Academic Search

Mesoporus silica dielectrics, which revealed low refractive index (n~1.26), were introduced together with Si3N4 layers to be double-layer-based graded-refractive-index anti- reflectors for silicon solar-cells. Enhanced solar-light transmission increased conversion efficiency of Si solar panels by 4%. The degradation in photovoltaic efficiency of solar panels that were covered with Si3N4\\/MS anti-reflectors was as small as 0.54 % after 60 hours of

Jia-Min Shieh; Li-Jung Liu; Jui-Chung Shiao; Chao-Kei Wang; Shich-Chuan Wu; Wen-Chien Yu; Hao-Chung Kuo; Shia-Chia Liu; Yi-Fan Lai; Kuo-Chen Hsiang; Yen-Chang Chen

2008-01-01

201

Photoinduced changes in refractive index of nanostructured shungite-containing polyimide systems  

NASA Astrophysics Data System (ADS)

Photoinduced changes in the refractive index of a conjugate polyimide (PI) matrix sensitized by shungite carbon nanoparticles have been studied for the first time. The results are compared to the data of previous investigations of the photorefractive properties of PI matrices doped with fullerenes, carbon nanotubes, and quantum dots. The nonlinear refractive index of the proposed material has been determined using the dynamic holography techniques. The position of conjugate polymer materials of this type among the other nonlinear optical systems is considered.

Kamanina, N. V.; Serov, S. V.; Shurpo, N. A.; Rozhkova, N. N.

2011-10-01

202

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

203

Enhanced refractive index without absorption in optical fibers via an indirect incoherent pump field  

NASA Astrophysics Data System (ADS)

We demonstrate a scheme for realizing the 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 be easily controlled via adjusting properly the parameters of the corresponding system. Our scheme may provide some new possibilities for technological applications in optical-fiber communication.

Ge, Qiang

2014-12-01

204

In situ refraction index of liquid measurement using polymer optical fibers  

NASA Astrophysics Data System (ADS)

A device for the measure of index of refraction of liquids in situ based on polymer optical fibers (POFs) was demonstrated. It consists in a sensor head of three passive POFs where two are coupled to two detectors and an electronic unit for the differential measure of signals. A differential operating principle is utilized to reduce noise such as light intensity fluctuation. The device was successfully checked measuring refraction index changes of the water with different concentrations of sugar, salt and alcohol.

Lomer, Mauro; Zubia, Joseba; Conde, Olga M.; Mirapeix, Jesus M.; Cubillas, A. M.; Lopez-Higuera, Jose M.

2004-06-01

205

Real and imaginary index-of-refraction measurements for RP1 rocket fuel  

Microsoft Academic Search

Complex index of refraction values of RP-1 liquid rocket fuel are reported at laser wavelengths of 0.193 micrometers (ArF excimer), 0.5145 micrometers (argon-ion), 0.532 micrometers (Nd-YAG, frequency doubled), 1.064 micrometers (Nd-YAG), and 10.5915 micrometers (CO2). The imaginary part of the index of refraction (k) was determined by the traditional transmission method. The real part (n-r)) is determined by reflectance measurements,

Dennis R. Alexander; Robert D. Kubik; Ramu Kalwala; John P. Barton

1994-01-01

206

Quantification of nanoscale nuclear refractive index changes during the cell cycle  

PubMed Central

Intrigued by our recent finding that the nuclear refractive index is significantly increased in malignant cells and histologically normal cells in clinical histology specimens derived from cancer patients, we sought to identify potential biological mechanisms underlying the observed phenomena. The cell cycle is an ordered series of events that describes the intervals of cell growth, DNA replication, and mitosis that precede cell division. Since abnormal cell cycles and increased proliferation are characteristic of many human cancer cells, we hypothesized that the observed increase in nuclear refractive index could be related to an abundance or accumulation of cells derived from cancer patients at a specific point or phase(s) of the cell cycle. Here we show that changes in nuclear refractive index of fixed cells are seen as synchronized populations of cells that proceed through the cell cycle, and that increased nuclear refractive index is strongly correlated with increased DNA content. We therefore propose that an abundance of cells undergoing DNA replication and mitosis may explain the increase in nuclear refractive index observed in both malignant and histologically normal cells from cancer patients. Our findings suggest that nuclear refractive index may be a novel physical parameter for early cancer detection and risk stratification. PMID:21806245

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

2011-01-01

207

Inversion method and experiment to determine the soot refractive index: application to turbulent diffusion flames  

NASA Astrophysics Data System (ADS)

Experimental and numerical studies have been performed to determine the soot refractive index in methane turbulent diffusion flames with two oxidizers: air and oxygen. In the flame zone, soot particles were sampled with a cooled probe. Measurements of optical soot properties have been carried out to obtain extinction and vertical-vertical (90°) scattering coefficients. The size distributions were obtained by electrical mobility analysis. Using these distributions, the optical properties have been computed with the Rayleigh-Debye-Gans theory for fractal aggregates by considering the morphology of soot aggregates and using morphological parameter values based on literature reports for other similar systems. Then, the refractive index has been obtained from a numerical inversion method by matching the measured and computed optical coefficients. This refractive index determination method is new to our knowledge. In turbulent diffusion methane oxygen flames the soot refractive index averaged value found is m = 1.95(±0.13)-0.51i(±0.12), and in the air flame m = 2.10(±0.12)-0.48i(±0.06). In view of the uncertainties, the refractive index is independent of the oxidizer type, the aerodynamic conditions and the flame zone location for the sampling. A sensitivity analysis has been carried out to study the influence of some morphological and experimental parameters on the refractive index value.

Van-Hulle, P.; Talbaut, M.; Weill, M.; Coppalle, A.

2002-03-01

208

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

DOEpatents

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

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

1984-06-19

209

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

210

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

211

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

PubMed

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

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

2014-06-01

212

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

213

All-angle negative refraction without negative effective index Chiyan Luo, Steven G. Johnson, and J. D. Joannopoulos*  

E-print Network

All-angle negative refraction without negative effective index Chiyan Luo, Steven G. Johnson, and J 13 May 2002 We describe an all-angle negative refraction effect that does not employ a negative effective index of refraction and involves photonic crystals. A few simple criteria sufficient to achieve

214

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 to an isotropic negative-refractive-index medium. We definitively show that in all cases the energy is always

Sridhar, Srinivas

215

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

216

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

217

Experimental demonstration of guiding and confining light in nanometer-size low-refractive-index material  

Microsoft Academic Search

We experimentally demonstrate a novel silicon waveguide structure for guiding and confining light in nanometer-wide low-refractive-index material. The optical field in the low-index material is enhanced because of the discontinuity of the electric field at high-index-contrast interfaces. We measure a 30% reduction of the effective index of light propagating in the novel structure due to the presence of the nanometer-wide

Qianfan Xu; Vilson R. Almeida; Roberto R. Panepucci; Michal Lipson

2004-01-01

218

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

PubMed

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

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

2012-11-01

219

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

220

Nonlinear refractive index of fs-laser-written waveguides in fused silica  

NASA Astrophysics Data System (ADS)

We report on the measurement of the nonlinear refractive index of fs-laser written waveguides in fused silica by analyzing self-phase modulation of the propagating light. The nonlinear index is reduced considerably compared to the bulk material by the writing process and is furthermore highly dependant on processing parameters.

Blömer, Dominik; Szameit, Alexander; Dreisow, Felix; Schreiber, Thomas; Nolte, Stefan; Tünnermann, Andreas

2006-03-01

221

Analysis of the response of long period fiber gratings to external index of refraction  

Microsoft Academic Search

This paper demonstrates that the change in wavelength of a long period fiber grating attenuation band with changes in external index of refraction can be enhanced by proper selection of the grating period. We calculate and experimentally verify that the wavelength shift caused by changing the external index from n=1 to n=1.44 of the attenuation band which appears in the

Heather J. Patrick; Alan D. Kersey; Frank Bucholtz

1998-01-01

222

Modification of the refractive-index contrast in polymer opal films P. Spahn,*a  

E-print Network

Modification of the refractive-index contrast in polymer opal films P. Spahn,*a C. E. Finlayson, Accepted 15th April 2011 DOI: 10.1039/c1jm00063b Synthetic opals, based on self-assembled arrays of core for the appearance of structural colour in polymer opal films. We report how the index contrast can be modified

Steiner, Ullrich

223

Refractive-index changes in fused silica produced by heavy-ion implantation followed by photobleaching.  

PubMed

The changes in refractive index, optical absorption, and volume of synthetic fused silica resulting from the implantation of germanium and silicon ions at energies of 3 and 5 MeV are reported. Implantation changes the density and generates ultraviolet color centers in the silica, which increases the refractive index at visible wavelengths by ~1%. Irradiation of the implanted samples with 249-nm light from a KrF excimer laser photobleaches the color centers and reduces the index by more than 0.1%. Photobleaching is used to write a 4.3-microm pitch diffraction grating in the implanted silica. PMID:19798273

Albert, J; Malo, B; Hill, K O; Johnson, D C; Brebner, J L; Leonelli, R

1992-12-01

224

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

225

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

226

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

227

Analysis of interferograms of refractive index inhomogeneities produced in optical materials  

NASA Astrophysics Data System (ADS)

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

Tarjányi, N.

2014-12-01

228

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

229

Dependence of tissue optical properties on solute-induced changes in refractive index and osmolarity  

NASA Astrophysics Data System (ADS)

Additions of a solute/carbohydrate in tissue affect the size of tissue cells and the refractive indexes of the extra- and intracellular fluids, and thus the overall tissue scattering properties. We use both the Rayleigh-Gans and Mie theory approximation in calculating effects of the osmolarity and refractive indexes on the reduced scattering coefficient of tissue, and employ photon diffusion theory to associate the reduced scattering coefficient to the mean optical path length. The calculations show that changes of scattering in tissue depend not only on the change in extracellular refractive index but also on the change in osmolarity, and thus on the change in cell size and volume fraction. Experimentally, we have utilized time-domain and frequency- domain NIR techniques to measure the changes of optical properties caused by an addition of a solute in tissue models and in perfused rat livers. The temperature-dependent path length measurement of the perfused liver confirms the dependence of tissue scattering on the tissue cell size. The results obtained from the liver with three kinds of carbohydrate perfusion display different scattering aspects and can be well explained by changes in cell size and in extracellular as well as intracellular refractive indexes. The consistency between the theoretical and experimental results confirms the dependence of optical properties in (liver) tissue on both tissue osmolarity and relative refractive indexes between the extracellular and intracellular compartments. This study suggests that the NIR technique is a novel and useful tool for noninvasive, physiological monitoring.

Liu, Hanli; Beauvoit, Bertrand; Kimura, Mika; Chance, Britton

1996-04-01

230

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

231

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

232

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

233

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

Microsoft Academic Search

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

Michael Monir; Hatem El-Refaei; Diaa Khalil

2006-01-01

234

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

235

Pilon's Lab UCLA www.seas.ucla.edu/~pilon/ Refraction and absorption index of Botryococcus braunii, Chlorella sp. and  

E-print Network

Pilon's Lab ­ UCLA www.seas.ucla.edu/~pilon/ Refraction and absorption index of Botryococcus.seas.ucla.edu/~pilon/ Refraction and absorption index of Botryococcus braunii 8 9 10 11 12 13 14 15 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 Numberfrequency Equivalent diameter, ds (m) (nm) Refraction index, n

Pilon, Laurent

236

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

237

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

238

The refractive index of curved spacetime II: QED, Penrose limits and black holes  

NASA Astrophysics Data System (ADS)

This work considers the way that quantum loop effects modify the propagation of light in curved space. The calculation of the refractive index for scalar QED is reviewed and then extended for the first time to QED with spinor particles in the loop. It is shown how, in both cases, the low frequency phase velocity can be greater than c, as found originally by Drummond and Hathrell, but causality is respected in the sense that retarded Green functions vanish outside the lightcone. A ``phenomenology'' of the refractive index is then presented for black holes, FRW universes and gravitational waves. In some cases, some of the polarization states propagate with a refractive index having a negative imaginary part indicating a potential breakdown of the optical theorem in curved space and possible instabilities.

Hollowood, Timothy J.; Shore, Graham M.; Stanley, Ross J.

2009-08-01

239

Interferometric spectroscopy of scattered light can quantify the statistics of subdiffractional refractive-index fluctuations  

PubMed Central

Despite major importance in physics, biology, and other sciences, optical sensing of nanoscale structures in the far-zone remains an open problem due to the fundamental diffraction limit of resolution. We establish that the expected value of spectral variance (??2) of a far-field, diffraction-limited microscope image can quantify the refractive-index fluctuations of a label-free, weakly scattering sample at subdiffraction length scales. We report the general expression of ?? for an arbitrary refractive-index distribution. For an exponential refractive-index spatial correlation, we obtain a closed-form solution of ?? which is in excellent agreement with three-dimensional finite-difference time-domain solutions of Maxwell's equations. Sensing complex inhomogeneous media at the nanoscale can benefit fields from material science to medical diagnostics. PMID:23909326

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

2014-01-01

240

Interferometric spectroscopy of scattered light can quantify the statistics of subdiffractional refractive-index fluctuations.  

PubMed

Despite major importance in physics, biology, and other sciences, the optical sensing of nanoscale structures in the far zone remains an open problem due to the fundamental diffraction limit of resolution. We establish that the expected value of spectral variance (?[over ˜](2)) of a far-field, diffraction-limited microscope image can quantify the refractive-index fluctuations of a label-free, weakly scattering sample at subdiffraction length scales. We report the general expression of ?[over ˜] for an arbitrary refractive-index distribution. For an exponential refractive-index spatial correlation, we obtain a closed-form solution of ?[over ˜] that is in excellent agreement with three-dimensional finite-difference time-domain solutions of Maxwell's equations. Sensing complex inhomogeneous media at the nanoscale can benefit fields from material science to medical diagnostics. PMID:23909326

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

2013-07-19

241

Index of refraction, Rayleigh scattering length, and Sellmeier coefficients in solid and liquid argon and xenon  

E-print Network

Like all the noble elements, argon and xenon are scintillators, \\emph{i.e.} they produce light when exposed to radiation. Large liquid argon detectors have become widely used in low background experiments, including dark matter and neutrino research. However, the index of refraction of liquid argon at the scintillation wavelength has not been measured and current Rayleigh scattering length calculations disagree with measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce a new calculation using previously measured data in liquid and solid argon and xenon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship. As a point of validation, we compare our extrapolated index of refraction for liquid xenon against the measured value and find agreement within the uncertainties. This method results in a Rayle...

Grace, Emily

2015-01-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

243

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

244

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

245

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

246

Refractive index of Y(2)O(3) stabilized cubic zirconia: variation with composition and wavelength.  

PubMed

Previous measurements of refractive index vs wavelength for cubic zirconia were extended to include the variation of index with Y(2)O(3) stabilizer concentration. It was found that a three-term Sellmeier formula fits the index data for each concentration to within ~1 x 10(-4) and that the Sellmeier constants have a nonlinear dependence on concentration but do follow the density. Fitting each of the six Sellmeier constants to a threeterm polynomial provides a set of eighteen coefficients sufficient to calculate the index at any wavelength, for any concentration. Conversely, the Y(2)O(3) concentration can be determined from the refractive index with greater accuracy than by chemical analysis. PMID:20563194

Wood, D L; Nassau, K; Kometani, T Y

1990-06-01

247

Z-scan study on the nonlinear refractive index of copper nanocluster composite silica glass  

SciTech Connect

We used the Z-scan technique for measuring the nonlinear refractive index n{sub 2} of a thin composite film formed by copper nanoparticles embedded in silica glass. By varying the number of pulses of the laser shot, we evidenced heating effects induced by the laser during measurements. We were able to estimate the nonthermal refractive-index value, n{sub 2}=(3.0{+-}0.3){times}10{sup {minus}12}cm{sup 2}/W. {copyright} 2001 American Institute of Physics.

Battaglin, G.; Calvelli, P.; Cattaruzza, E.; Gonella, F.; Polloni, R.; Mattei, G.; Mazzoldi, P.

2001-06-18

248

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

249

Index of refraction for sodium matter waves traveling in a cold noble-gas medium  

SciTech Connect

The index of refraction for sodium matter waves traveling in a cold noble-gas medium is calculated as a function of temperature and beam velocity. Resonances and glory oscillations are present in the center-of-mass scattering amplitude and may be seen in the refractive index at very low temperatures. The sensitivity of the calculations to the molecular potential is investigated for the case of argon, and results at 300 K are compared to a recent experiment. Effective range parameters are computed and the attenuation and phase of the matter waves are analyzed as a function of temperature and beam velocity.

Blanchard, Shannon; Civello, Dave; Forrey, Robert C. [Pennsylvania State University, Berks-Lehigh Valley College, Reading, Pennsylvania 19610 (United States)

2003-01-01

250

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

251

Refractive index measurement based on the wavefront difference method by a Fizeau interferometer  

NASA Astrophysics Data System (ADS)

We present a refractive index measurement method by measuring the longitudinal displacement of the converging rays after passing through a plane-parallel-plate sample. Using the wavefront difference method, the error source from the divergence angle of the beams is eliminated, and an analytical formula for refractive index calculation is derived. With a Fizeau interferometer, an experimental system for plane-parallel-plate sample testing is proposed to verify the principle. Experimental results indicate that the order of its accuracy is 10-4.

Yang, Zhongming; Gao, Zhishan; Yuan, Qun; Ye, Jingfei; Tian, Xue

2013-12-01

252

Retrieval of dust-particle refractive index using the phenomenon of negative polarization  

NASA Astrophysics Data System (ADS)

We study the phenomenon of negative polarization in irregularly shaped agglomerated debris particles. We find that the location of the negative polarization minimum is unambiguously governed by Re(m). Furthermore, the amplitude of the negative polarization puts a strong constraint on the material absorption in target particles regardless of their real part of refractive index Re(m). The interrelation can be parameterized with a simple formula and it can be utilized in remote sensing. We apply our finding to laboratory optical measurements of Allende meteorite at ?=0.633 ?m and estimate its complex refractive index to be m?(1.68-1.83)+(0.01-0.02)i.

Zubko, Evgenij; Videen, Gorden; Shkuratov, Yuriy

2015-01-01

253

Simultaneous measurement of refractive index and thickness with a convergent beam  

NASA Astrophysics Data System (ADS)

A new approach to the simultaneous measurement of refractive index and thickness based on the focus shifts of a convergent beam intercepted by a test plate is proposed. By using ray optics, a defined focus shift can be derived as a function of the refractive index and thickness as well as the angular position of the test plate with respect to the optical axis. From a pair of focus shifts obtained at two different angular positions, it is shown that the desired measurands can be simultaneously determined without prior knowledge of either parameter. A simulation result for the proposed concept based on graphically solving the equations of their respective focus shifts is presented.

Hii, King Ung; Kwek, Kuan Hiang

2014-09-01

254

Broadband focusing and collimation of water waves by zero refractive index  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

255

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

256

Needle-based refractive index measurement using low-coherence interferometry  

NASA Astrophysics Data System (ADS)

We present a novel needle-based device for the measurement of refractive index and scattering using low-coherence interferometry. Coupled to the sample arm of an optical coherence tomography system, the device detects the scattering response of, and optical path length through, a sample residing in a fixed-width channel. We report use of the device to make near-infrared measurements of tissues and materials with known optical properties. The device could be used to exploit the refractive index variations of tissue for medical and biological diagnostics accessible by needle insertion.

Zysk, Adam M.; Adie, Steven G.; Armstrong, Julian J.; Leigh, Matthew S.; Paduch, Alexandre; Sampson, David D.; Nguyen, Freddy T.; Boppart, Stephen A.

2007-02-01

257

Monitoring of temperature-mediated adipose tissue phase transitions by refractive-index measurements  

NASA Astrophysics Data System (ADS)

Monitoring of temperature-mediated adipose tissue phase transitions were studied in vitro using an Abbe refractometer. The 1-2-mm thick porcine fat tissues slices were used in the experiments. The observed change in the tissue was associated with several phase transitions of lipid components of the adipose tissue. It was found that overall heating of a sample from the room to higher temperature led to more pronounced and tissue changes in refractive index if other experimental conditions were kept constant. We observed an abrupt change in the refractive index in the temperature range of 37-60 °C.

Yanina, I. Yu.; Popov, A. P.; Bykov, A. V.; Tuchin, V. V.

2014-10-01

258

Simulation of simultaneous measurement for red blood cell thickness and refractive index  

NASA Astrophysics Data System (ADS)

Red blood cell (RBC) parameters are of great importance for diagnostic purposes. Using the simulation method, the variations of both the thickness and the refractive index of a RBC were investigated in a dual-medium quantitative measurement (DMQ), which is realized via phase-shifting digital holography with two types of cell media. Results show that both the calculated thickness and the calculated refractive index agree well with the original ones with an average relative deviation of 2.13% and of 0.12% in valid regions, respectively. The simulation for RBC will provide some guidance for experimental parameter setting and data processing in DMQ.

Jin, Weifeng; Wang, Yawei; Ren, Naifei; Bu, Min; Shang, Xuefu; Xu, Yuanyuan; Chen, Yujiao

2012-02-01

259

First measurements of the index of refraction of gases for lithium atomic waves  

E-print Network

We report here the first measurements of the index of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary part of the index of refraction $n$ for argon, krypton and xenon, as a function of the gas density for several velocities of the lithium beam. The linear dependence of $(n-1)$ with the gas density is well verified. The total collision cross-section deduced from the imaginary part is in very good agreement with traditional measurements of this quantity. Finally, as predicted by theory, the real and imaginary parts of $(n-1)$ and their ratio $\\rho$ exhibit glory oscillations.

Marion Jacquey; Matthias Büchner; Gérard Trénec; Jacques Vigué

2007-05-15

260

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

261

Complex index-of-refraction measurements for RP1 liquid rocket fuel  

Microsoft Academic Search

Complex index-of-refraction values of RP-1 liquid rocket fuel are reported at laser wavelengths of 0.193 micrometers (ArF excimer), 0.4765 micrometers (argon ion), 0.488 micrometers (argon ion), 0.5145 micrometers (argon ion), 0.532 micrometers (Nd-YAG, frequency doubled), 0.6328 micrometers (He-Ne), 1.064 micrometers (Nd-YAG), and 10.5915 micrometers (CO2). The imaginary part of the index of refraction (k) is determined by traditional transmission methods.

Dennis R. Alexander; Ramu Kalwala; Robert D. Kubik; Scott A. Schaub

1995-01-01

262

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

263

W-band Pancharatnam half-wave plate based on negative refractive index metamaterials.  

PubMed

Electromagnetic metamaterials, made from arrangements of subwavelength-sized structures, can be used to manipulate radiation. Designing metamaterials that have a positive refractive index along one axis and a negative refractive index along the orthogonal axis can result in birefringences, ?n>1. The effect can be used to create wave plates with subwavelength thicknesses. Previous attempts at making wave plates in this way have resulted in very narrow usable bandwidths. In this paper, we use the Pancharatnam method to increase the usable bandwidth. A combination of finite element method and transmission line models was used to optimize the final design. Experimental results are compared with the modeled data. PMID:24787153

Mohamed, Imran; Pisano, Giampaolo; Ng, Ming Wah

2014-04-01

264

Refractive index profile of fused-fiber couplers cross-section.  

PubMed

We investigate the refractive index profile of the cross-section of fused type fiber-optic couplers by solving the convective diffusion equation. We assume the refractive index to be a linear function of the dopant concentration. The viscous sintering of the optical fibers is considered as the motion of an incompressible Newtonian fluid which is driven by the surface tension acting at the free boundary. The internal velocity field is obtained using conformal mapping methods. We present numerical solutions of the resulting equations and compare them with experimental observations. PMID:19474919

Pone, Elio; Daxhelet, Xavier; Lacroix, Suzanne

2004-03-22

265

Electromagnetic Casimir effect and the spacetime index of refraction  

E-print Network

In [5] we investigated the response of vacuum energy to a gravitational field by considering a Casimir apparatus in a weak gravitational field. Our approach was based on a conjecture involving the interpretation of spacetime as a refractive medium and its effect on vacuum energy composed of virtual massless scalar particles. There it was shown how the case of virtual photons as the constituents of vacuum could be inferred from that of the massless scalar field. Here we explicitly show how the same conjecture applies to the electromagnetic vacuum composed of virtual photons. Specifically we show that the boundary conditions imposed on the components of the vector field, decomposed into two scalar fields, result in the same frequency shift for photons. Using the same decomposition and employing our conjecture, we also calculate the electromagnetic energy density for the Casimir apparatus in a weak gravitational field.

B. Nazari; M. Nouri-Zonoz

2012-02-29

266

a New Mechanism for Optical Nonlinearity: Light - Refractive Index Changes in Amorphous Arsenic Sulfide  

NASA Astrophysics Data System (ADS)

Amorphous semiconductors have been little studied from the point of view of nonlinear optics. However, certain aspects of their physical properties indicate that they would be useful for applications in optical communications. Broadening of the optical absorption edge suggests that resonant nonlinearities such as are observed in crystalline materials would occur over a much broader range in wavelength. Furthermore, because of structural disorder, an amorphous material can be deposited on a variety of substrates, opening the possibility for integration with other material technologies. We have measured transient refractive index changes in thin films of amorphous arsenic sulfide using a pump -probe spectroscopic technique. Calculations and experimental results indicate that the change in refractive index is not thermal in origin. We show that the dependences of this effect on excitation intensity and on excitation wavelength are consistent with the photoinduced absorption model for transient absorption changes in amorphous semiconductors. The magnitude of the measured refractive index change is quite large relative to other materials, with a nonlinear refractive index, n_2, comparable to those measured for resonant nonlinearities in crystalline semiconductors. However, we demonstrate that this mechanism for refractive nonlinearity exhibits characteristics that make it very different from those observed in crystalline materials. This effect is a hybrid nonlinearity; light which is strongly absorbed, and thus has a large effect on the material, produces a change in the refractive index at longer wavelengths where the absorption is very small. Thus the change is large, as are resonant nonlinearities in crystalline semiconductors, but it occurs in regions of low absorption, as do the nonresonant effects present in all materials. These wavelength characteristics, and the ability to deposit the material on a variety of substrates, suggest novel device applications for which amorphous semiconductors are uniquely suited. We have demonstrated the principle of such a device, making use of the already well-developed technology for fabricating waveguides in lithium niobate. Numerical calculations indicate that a practical device could be fabricated.

True, Emily Martin

1991-02-01

267

Computed tomography of x-ray index of refraction using the diffraction enhanced imaging method.  

PubMed

Diffraction enhanced imaging (DEI) is a new, synchrotron-based, x-ray radiography method that uses monochromatic, fan-shaped beams, with an analyser crystal positioned between the subject and the detector. The analyser allows the detection of only those x-rays transmitted by the subject that fall into the acceptance angle (central part of the rocking curve) of the monochromator/analyser system. As shown by Chapman et al, in addition to the x-ray attenuation, the method provides information on the out-of-plane angular deviation of x-rays. New images result in which the image contrast depends on the x-ray index of refraction and on the yield of small-angle scattering, respectively. We implemented DEI in the tomography mode at the National Synchrotron Light Source using 22 keV x-rays, and imaged a cylindrical acrylic phantom that included oil-filled, slanted channels. The resulting 'refraction CT image' shows the pure image of the out-of-plane gradient of the x-ray index of refraction. No image artefacts were present, indicating that the CT projection data were a consistent set. The 'refraction CT image' signal is linear with the gradient of the refractive index, and its value is equal to that expected. The method, at the energy used or higher, has the potential for use in clinical radiography and in industry. PMID:10795982

Dilmanian, F A; Zhong, Z; Ren, B; Wu, X Y; Chapman, L D; Orion, I; Thomlinson, W C

2000-04-01

268

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

269

Optical forces in lossless arbitrary refractive index optical trapping and micromanipulation  

NASA Astrophysics Data System (ADS)

This paper shows, using both a ray optics approach and in the framework of the generalized Lorenz-Mie theory (GLMT), what happens to the optical forces exerted on a lossless spherical particle with an arbitrary (positive or negative) relative refractive index, allowing the external medium also to be metamaterial. It is shown that the anti-parallelism between the linear momentum p of each photon and the Poynting vector S associated with the propagating wave, observed in negative refractive index media, leads to shifts in the direction of the optical force of a single ray and, consequently, to the total optical force exerted by an arbitrary-shaped laser beam. This extends the possible realizable traps and reveals how arbitrary-shaped laser beams can be used to trap particles with arbitrary refractive indices.

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

2012-11-01

270

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

271

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

272

Rigorous analysis of negative refractive index metamaterials using FDTD with embedded lumped elements  

Microsoft Academic Search

A methodology for the time-domain analysis of negative refractive index (NRI) media is proposed in this paper. Based on circuit models of NRI meta-materials and associated planar implementations that have been recently demonstrated, an extended FDTD approach is formulated, combining Maxwell's equations with lumped element voltage-current characteristics. Compared to previous FDTD modelling of NRI materials as negative dispersive index media,

Titos Kokkinos; Rubaiyat Islam; Costas D. Sarris; George V. Eleftheriades

2004-01-01

273

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

274

Refractive Index Enhancement in a Far-Off Resonant Atomic System D. D. Yavuz  

E-print Network

November 2005) We demonstrate a scheme where a laser beam which is very far detuned from an atomic show that the refractive index of a weak probe beam which is very far detuned from an optical resonance, and j2i, and an excited upper state jei. The probe beam, Ep, is weak and is largely detuned from any one

Yavuz, Deniz

275

Refractive index enhancement in a far-off resonant atomic system.  

PubMed

We demonstrate a scheme where a laser beam which is very far detuned from an atomic resonance experiences a large index of refraction with vanishing absorption. The essential idea is to excite two Raman resonances with appropriately chosen strong control lasers. PMID:16384218

Yavuz, D D

2005-11-25

276

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

277

Design and characteristics of refractive index sensor based on thinned and microstructure fiber Bragg grating  

NASA Astrophysics Data System (ADS)

A refractive index sensor based on the thinned and microstructure fiber Bragg grating (ThMs-FBG) was proposed and realized as a chemical sensing. The numerical simulation for the reflectance spectrum of the ThMs-FBG was calculated and the phase shift down-peak could be observed from the reflectance spectrum. Many factors influencing the reflectance spectrum were considered in detail for simulation, including the etched depth, length, and position. The sandwich-solution etching method was utilized to realize the microstructure of the ThMs-FBG, and the photographs of the microstructure were obtained. Experimental results demonstrated that the reflectance spectrum, phase shift down-peak wavelength, and reflected optical intensity of the ThMs-FBG all depended on the surrounding refractive index. However, only the down-peak wavelength of the ThMs-FBG changed with the surrounding temperature. Under the condition that the length and cladding diameter of the ThMs-FBG microstructure were 800 and 14 ?m, respectively, and the position of the microstructure of the ThMs-FBG is in the middle of grating region, the refractive index sensitivity of the ThMs-FBG was 0.79 nm/refractive index unit with the wide range of 1.33-1.457 and a high resolution of 1.2×10-3. The temperature sensitivity was 0.0103 nm/°C, which was approximately equal to that of common FBG.

Huang, Xue-Feng; Chen, Zhe-Min; Shao, Li-Yang; Cen, Ke-Fa; Sheng, De-Ren; Chen, Jun; Zhou, Hao

2008-02-01

278

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 to host red blood cells (RBCs). Major struc- tural changes include the formation of parasitophorus

Suresh, Subra

279

Low loss, high index of refraction metamaterials based on multiple enhancement mechanisms  

Microsoft Academic Search

A new metallo-dielectric metamaterial is described in this paper that is comprised of a lattice of so-called dumbbell particles. Low loss with potentially large index of refraction is possible with these artificial electromagnetic materials using multiple enhancement effects including thin layers of high dielectric constant, low loss composite films printed between layers of dumbbell particles. Spray deposition of these composite

Keith W. Whites; Tony Amert; Lori Groven; Brian Glover

2010-01-01

280

Rapid Inversion of Angular Deflection Data for Certain Axisymmetric Refractive Index Distributions  

NASA Technical Reports Server (NTRS)

Certain functions useful for representing axisymmetric refractive-index distributions are shown to have exact solutions for Abel transformation of the resulting angular deflection data. An advantage of this procedure over direct numerical Abel inversion is that least-squares curve fitting is a smoothing process that reduces the noise sensitivity of the computation

Rubinstein, R.; Greenberg, P. S.

1994-01-01

281

Nonlinear absorption and refractive index of a Brillouin-scattered mode in magnetoactive centrosymmetric semiconductor plasmas  

Microsoft Academic Search

An analytical investigation has been made for the nonlinear refractive index and absorption coefficient of the Brillouin-scattered Stoke's mode resulting from the nonlinear interaction of an intense pumping light beam with acoustic perturbations internally generated due to the electrostrictive property of the doped semiconductor plasma. The origin of this nonlinear interaction lies in the third-order optical susceptibility arising from the

Swati Dubey; S. Ghosh

1994-01-01

282

Inversion method and experiment to determine the soot refractive index: application to turbulent diffusion flames  

Microsoft Academic Search

Experimental and numerical studies have been performed to determine the soot refractive index in methane turbulent diffusion flames with two oxidizers: air and oxygen. In the flame zone, soot particles were sampled with a cooled probe. Measurements of optical soot properties have been carried out to obtain extinction and vertical-vertical (90°) scattering coefficients. The size distributions were obtained by electrical

P. Van-Hulle; M. Talbaut; M. Weill; A. Coppalle

2002-01-01

283

Fibre Laser Using a Microchannel Based Loss Tuning Element for Refractive Index Sensing  

E-print Network

Fibre Laser Using a Microchannel Based Loss Tuning Element for Refractive Index Sensing Chengbo Mou, Birmingham, UK, B4 7ET ABSTRACT We have proposed and demonstrated a fibre laser system using a microchannel microchannel was created by femtosecond (fs) laser inscription assisted chemical etching in the cavity fibre

Neirotti, Juan Pablo

284

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

285

PROGRESS IN PHYSICS Local Doppler effect, index of refraction through the Earth crust,  

E-print Network

PROGRESS IN PHYSICS Local Doppler effect, index of refraction through the Earth crust, PDF to the local Doppler effect between a local clock attached to a given detector at Gran Sasso, say CG, x, y, z) with velocity given by Eq. (1). Since CG crosses CC, the Doppler effect between the proper

Boyer, Edmond

286

Estimation of the optimum refractive index by the laser diffraction and scattering method  

Microsoft Academic Search

In the field of ceramics, the particle size distribution of submicron powders has been measured by using many different types of equipment, which are based on different measuring principles. However, at present, the laser diffraction and scattering method is the most popular method in particle size analysis. Although this method is good for operation, the refractive index of the particles

Osamu Hayakawa; Kenji Nakahira; Jun Ichiro Tsubaki

1995-01-01

287

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

288

Tomographic reconstruction for arbitrary refractive index distribution of optical fibre preforms  

Microsoft Academic Search

We demonstrate a tomographic method to measure arbitrary refractive index profiles of silica and polymer optical preforms. The preform is rotated through 180 degrees and the deflection angle data collected, then the back projection technique and spline interpolation algorithm are used in the computed tomographic two-dimensional profile distribution. An improved formula for calculating the optical path length from the deflection

Y. C. Zhao; S. Fleming; K. Lyytikainen; M. A. van Eijkelenborg

2004-01-01

289

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

290

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

PubMed Central

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

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

2015-01-01

291

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

292

Refractive index of planktonic cells as a measure of cellular carbon and chlorophyll a content  

Microsoft Academic Search

Current methods for determining carbon content in individual planktonic cells from particle volume alone may involve large errors, and no routine technique exists for determining chlorophyll a content in individual phytoplankters. In this study the concept of using the refractive index of cells as a measure of intracellular concentrations of carbon and chlorophyll a is discussed. Specifically, the real part

Dariusz Stramski

1999-01-01

293

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

DOEpatents

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

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

1980-01-01

294

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

295

A backward-wave antenna based on negative refractive index LC networks  

Microsoft Academic Search

Recently, there has been significant interest in materials with simultaneously negative permeability and permittivity, also referred to as negative refractive index metamaterials. Metamaterials comprised of straight metal wires and split ring resonators operating in the long wavelength regime exhibit a microwave frequency range with simultaneously negative values of effective permeability and permittivity. We use a 1D L-C loaded transmission line

Anthony Grbic; George V. Eleftheriades

2002-01-01

296

Tomographic investigation of the refractive index profiling using speckle photography technique  

Microsoft Academic Search

A multiple-exposure speckle photography technique has been applied to record the deflection angle of light travelling through hot air around a candle flame for different viewing angles (projections) along a line for each of eight specklegrams. The obtained data has been used to provide input data for the tomographic reconstruction program to construct a three-dimensional refractive index distribution.

H. El-Ghandoor

1997-01-01

297

Continuous index of refraction measurements to 20 GPa in Z-cut sapphire  

NASA Astrophysics Data System (ADS)

Isentropic compression experiments (ICE) on Sandia National Laboratories' Z Accelerator are used to make continuous measurements of the index of refraction in single crystal Z-cut sapphire as the longitudinal stress is gradually increased to 20 GPa (uniaxial strain of about ˜3.9%). A planar, ramp compression wave, generated by a large magnetic field, propagates through a planar copper base plate. Part of the rear surface of the base plate is a free surface and part is covered with a sapphire window. Comparisons are made of velocity histories measured simultaneously at the free surface and at the copper/sapphire interface using a velocity interferometer system for any reflector (VISAR). This is sufficient to determine the index of refraction of the sapphire continuously as a function of density. Perturbations to the compression waves caused by interactions with the free surface and with the sapphire are accounted for by backward or forward solutions to the equations of motion. The effect of the unsteady nature of the compression wave in sapphire on the interferometry measurements is also taken into account. Results validate the interpretation of VISAR measurements on continuous loading experiments performed with optical windows. The measured index of refraction of sapphire agrees with previous studies validating this experimental technique and showing that it is useful for studying other materials for which index of refraction data do not exist. In addition, measured compression isentropes for copper and sapphire compare favorably with existing theoretical models.

Hayes, D. B.; Hall, C. A.; Asay, J. R.; Knudson, M. D.

2003-08-01

298

Composites with Negative Refractive Index, Thermal, Self-healing and Self-sensing Functionality  

E-print Network

138 Composites with Negative Refractive Index, Thermal, Self-healing and Self-sensing Functionality-NASSER ABSTRACT Here, we outline recent achievements in creating structural composite materials with controlled render the composite information-based, so that it can monitor and report on the local structural

Nemat-Nasser, Sia

299

Refractive index sensing for online monitoring water and ethanol content in bio fuels  

Microsoft Academic Search

We report on a refractive index sensor based on a planar Bragg grating (PBG) capable to online monitor the water content in Biodiesel and the amount of ethanol admixture to conventional fuels, respectively. Our results demonstrate the capability of the sensor to distinguish the transition between about 190 and 500 ppm water in Biodiesel, enabling to monitor the production process

S. Belle; S. Scheurich; R. Hellmann; S. So; I. J. G. Sparrow; G. D. Emmerson

2010-01-01

300

An efficient method for computing optical waveguides with discontinuous refractive index profiles using spectral collocation method with domain decomposition  

Microsoft Academic Search

An accurate and efficient solution method using spectral collocation method with domain decomposition is proposed for computing optical waveguides with discontinuous refractive index profiles. The use of domain decomposition divides the usual single domain into a few subdomains at the interfaces of discontinuous refractive index profiles. Each subdomain can be expanded by a suitable set of orthogonal basis functions and

Chia-Chien Huang; Chia-Chih Huang; Jaw-Yen Yang

2003-01-01

301

Modeling of metamaterials with negative refractive index using 2-D shunt and 3-D SCN TLM networks  

Microsoft Academic Search

We present two novel techniques for modeling two- and three-dimensional metamaterials with negative refractive index by transmission-line matrix (TLM) networks. The TLM networks are numerical models of reactively loaded periodic networks that support backward waves and constitute artificial media with negative refractive index. The TLM models, their implementations, and results computed with the models will be presented.

Poman P. M. So; Huilian Du; W. J. R. Hoefer

2005-01-01

302

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

303

We have learned that the index of refraction is not just a simple number, but a quantity that varies with the frequency of the light.  

E-print Network

Dispersion )(n = 1 + )(2 22 0 b/mi /mqNq o o (20) We have learned that the index of refraction). We find then that the index of refraction n is approximately constant. It turns out this is also in (20) decreases making the index of refraction to increase. That is, n increases with . The index

304

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

305

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

PubMed Central

A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated could range from three to seven. Each D-shaped zone covered a sensor volume of 100 ?m depth, 250 ?m width, and 1 mm length. The mean roughness of the core surface obtained by the AFM images was 231.7 nm, which is relatively smooth. Results of the tensile test indicated that the fibers have sufficient mechanical strength to resist damage from further processing. The multi-D-shaped optical fiber as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results for different concentrations of sucrose solution show that a resolution of 1.27 × 10?3–3.13 × 10?4 RIU is achieved for refractive indices in the range of 1.333 to 1.403, suggesting that the multi-D-shaped fibers are attractive for chemical, biological, and biochemical sensing with aqueous solutions. PMID:22399908

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

2010-01-01

306

Fiber-optic refractive index sensor based on surface plasmon resonance  

NASA Astrophysics Data System (ADS)

A fiber-optic refractive index sensor based on surface plasmon resonance (SPR) in a thin metal film deposited on an unclad core of a multimode fiber is presented. The sensing element of the SPR fiber-optic sensor is a bare core of a step-index optical fiber made of fused silica with a deposited gold film. First, a model of the SPR fiber-optic sensor based on the theory of attenuated total internal reflection is presented. The analysis is carried out in the frame of optics of multilayered media. The sensing scheme uses a wavelength interrogation method and the calculations are performed over a broad spectral range. Second, in a practical realization of the sensor with a double-sided sputtered gold film, a reflection-based sensing scheme to measure the refractive indices of liquids is considered. 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 1.364 are measured.

Hlubina, Petr; Ciprian, Dalibor; Kadulova, Miroslava

2015-01-01

307

Sensitive hydrogen peroxide content measurement technology using refractive-index-based optical device  

NASA Astrophysics Data System (ADS)

Monitoring of water quality is essential to modern life. Not only is it a major factor in safeguarding public health, high quality freshwater is also a key input in agriculture and many industrial process. A preliminary prototype for hydrogen peroxide content in water is setup and introduced. Based on the detection of beam deviation due to the refractive index changes of the aqueous hydrogen peroxide solution, hydrogen peroxide content can be measured by a position-sensitive detector. Measurement principle is theoretically described. Experimental results indicate the feasibility of the developed system. Not like intensity-modulated refractive index sensor which necessitates a stable light source, this sensor exploits the beam deviation due to optical refraction at the receiving end face of the measurement cell, which is caused by changes in refractive index with different hydrogen peroxide content in water. Hydrogen peroxide content measurement resolution can reach about 0.01% within the measurement range from distilled water to hydrogen peroxide content of 30%.

Peng, Bao-jin; Ying, Chao-Fu; Ye, Hui-qun; Zhao, Yong; Liu, Yun-Tao

2005-01-01

308

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

309

Measuring the refractive index of crude oil using a capillary tube interferometer  

NASA Astrophysics Data System (ADS)

A method for measuring the refractive index of low-transparent crude oils using a capillary tube interferometer is described. The method is based on analyzing the resulting transverse interference fringe patterns in terms of their positions with respect to the lens/capillary tube interferometer. The refractive indices of seven blended crude oils of low transparency were measured with accuracy of up to six decimal digits and were related to the API gravity of the oils. The ray tracing inside the capillary tube is explained and the transverse bell-shaped interference fringes are interpreted.

El Ghandoor, H.; Hegazi, E.; Nasser, Ibraheem; Behery, G. M.

2003-07-01

310

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

311

Optically transparent bionanofiber composites with low sensitivity to refractive index of the polymer matrix  

NASA Astrophysics Data System (ADS)

Transparent polymers were reinforced by bacterial cellulose (BC) nanofibers, which are 10×50nm ribbon-shaped fibers. They exhibited high luminous transmittance at a fiber content as high as 60 wt %, and low sensitivity to a variety of refractive indices of matrix resins. Due to the nanofiber size effect, high transparency was obtained against a wider distribution of refractive index of resins from 1.492 to 1.636 at 20 °C. The optical transparency was also surprisingly insensitive to temperature increases up to 80 °C. As such, BC nanofibers appear to be viable candidates for optically transparent reinforcement.

Nogi, Masaya; Handa, Keishin; Nakagaito, Antonio Norio; Yano, Hiroyuki

2005-12-01

312

All-optical on-chip sensor for high refractive index sensing  

NASA Astrophysics Data System (ADS)

A highly sensitive sensor design based on two-dimensional photonic crystal cavity is demonstrated. The geometric structure of the cavity is modified to gain a high quality factor, which enables a sensitive refractive index sensing. A group of slots with optimized parameters is created in the cavity. The existence of the slots enhances the light-matter interactions between confined photons and analytes. The interactions result in large wavelength shifts in the transmission spectra and are denoted by high sensitivities. Experiments show that a change in refractive index of ?n ˜ 0.12 between water and oil sample 1 causes a spectral shift of 23.5 nm, and the spectral shift between two oil samples is 5.1 nm for ?n ˜ 0.039. These results are in good agreement with simulations, which are 21.3 and 7.39 nm for the same index changes.

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

2015-01-01

313

Magnifying absolute instruments for optically homogeneous regions  

SciTech Connect

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, Tomas [Institute of Theoretical Physics and Astrophysics, Masaryk University, Kotlarska 2, CZ-61 137 Brno (Czech Republic)

2011-09-15

314

Refractive index profile in ion-implanted neodymium-doped yttrium vanadate waveguide: the relation between index change and lattice damage  

NASA Astrophysics Data System (ADS)

A model is presented to explain the refractive index changes in the ion-implanted neodymium-doped yttrium vanadate waveguide region, which is helpful for characterizing index profile dependence on implantation parameters. It indicates that the lattice damage is the main factor for the refractive index changes. Waveguide structure is formed mainly due to an increase of ordinary refractive index in the ion-implanted region. The theoretical results based on this model are in good agreement with the experimental data from 500 keV Si+ ion implantations and keV He+ ion implantations.

Ma, Yu-Jie; Lu, Fei; Yin, Jiao-Jian; Liu, Xiu-Hong

2013-09-01

315

Error budget for a calibration demonstration system for the reflected solar instrument for the climate absolute radiance and refractivity observatory  

NASA Astrophysics Data System (ADS)

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

Thome, Kurtis; McCorkel, Joel; McAndrew, Brendan

2013-09-01

316

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

317

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

318

Optimizing the resolution of nanohole arrays in metal films for refractive-index sensing  

NASA Astrophysics Data System (ADS)

We optimized the resolution of nanohole arrays in metal films for refractive-index sensing by increasing the sensitivity with modifications to the hole-array parameters and by increasing the signal to noise ratio of the sensor system. The nanohole-array parameters (including film thickness, periodicity and diameter) were first optimized by finite-difference time-domain simulations, and then the arrays were fabricated and tested, showing good agreement between the two cases (theory and experiment) in terms of optimal parameters. To improve the sensitivity and to reduce the noise, the laser source wavelength was optimized (including the efficiency of the camera for detection) and the intensity was increased. A bulk resolution of 6×10-7 refractive-index units was demonstrated. Due to the collinear microscope geometry and potential for multiplexing of nanohole arrays, these results are encouraging for future biosensing applications.

Cervantes Tellez, Gabriela Andrea; Ahmed, Aftab; Gordon, Reuven

2012-12-01

319

Pressure dependence of the refractive index in wurtzite and rocksalt indium nitride  

NASA Astrophysics Data System (ADS)

We have performed high-pressure Fourier transform infrared reflectance measurements on a freestanding InN thin film to determine the refractive index of wurtzite InN and its high-pressure rocksalt phase as a function of hydrostatic pressure. From a fit to the experimental refractive-index curves including the effect of the high-energy optical gaps, phonons, free carriers, and the direct (fundamental) band-gap in the case of wurtzite InN, we obtain pressure coefficients for the low-frequency (electronic) dielectric constant ??. Negative pressure coefficients of -8.8 × 10-2 GPa-1 and -14.8 × 10-2 GPa-1 are obtained for the wurtzite and rocksalt phases, respectively. The results are discussed in terms of the electronic band structure and the compressibility of both phases.

Oliva, R.; Segura, A.; Ibáñez, J.; Yamaguchi, T.; Nanishi, Y.; Artús, L.

2014-12-01

320

Structure and refractive index dispersive behavior of potassium niobate tantalate films prepared by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Pure perovskite phase and crack-free KTa 0.5Nb 0.5O 3 thin films were prepared on Pt/Ti/SiO 2/Si substrates by pulsed laser deposition. The structure and orientation were analyzed by X-ray diffraction. The optical properties were investigated by an ellipsometer. The relationship between the refractive index dispersive behavior and internal structure was analyzed by Sellmeier dispersion model and single electronic oscillator approximation. The parameters of room temperature monomial Sellmeier oscillator were calculated. And the refractive index dispersive parameter E0/ S0 of KTa 0.5Nb 0.5O 3 thin films on Pt/Ti/SiO 2/Si substrates is (6.72 ± 0.04) × 10 -14 eV m 2, which is consistent with those of KTN crystals and compounds with ABO 3 perovskite type structure.

Yang, Wenlong; Zhou, Zhongxiang; Yang, Bin; Jiang, Yongyuan; Tian, Hao; Gong, Dewei; Sun, Hongguo; Chen, Wen

2011-06-01

321

Determination of refractive index and concentration of iodine solutions using opals  

NASA Astrophysics Data System (ADS)

The determination of refractive index of iodine-ethanol solutions using SiO2 opals has been presented. For the first time concentration of solution iodine in ethanol has been determined by applying a simple method of using opal and de Feijter's relation. Basing on wavelength of diffraction peaks the appropriate formula describing concentration of iodine ethanol solution has been evolved. The uncertainty of the determined concentration has been established, too. The coefficient dnc/dC = 0.0201(4) (% w/w-1) of the linear dependence between refractive index and the concentration of iodine solution has been determined. The procedure of calibration of the used opal sensor is described. The opal sensor is not distracted by the measurement and can be used repeatedly.

K?pi?ska, Miros?awa; Starczewska, Anna; Szala, Janusz

2014-03-01

322

Refractive Index Sensor Based on a 1D Photonic Crystal in a Microfluidic Channel  

PubMed Central

A refractive index sensor has been fabricated in silicon oxynitride by standard UV lithography and dry etching processes. The refractive index sensor consists of a 1D photonic crystal (PhC) embedded in a microfluidic channel addressed by fiber-terminated planar waveguides. Experimental demonstrations performed with several ethanol solutions ranging from a purity of 96.00% (n = 1.36356) to 95.04% (n = 1.36377) yielded a sensitivity (??/?n) of 836 nm/RIU and a limit of detection (LOD) of 6 × 10?5 RIU, which is, however, still one order of magnitude higher than the theoretical lower limit of the limit of detection 1.3 × 10?6 RIU. PMID:22294930

Nunes, Pedro S.; Mortensen, Niels Asger; Kutter, Jörg P.; Mogensen, Klaus B.

2010-01-01

323

Application of simulated annealing for simultaneous retrieval of particle size distribution and refractive index  

SciTech Connect

This paper describes the application of the simulated annealing technique for the simultaneous retrieval of particle size distribution and refractive index based on polarization modulated scattering (PMS) measurements. The PMS technique is a well-established method to measure multiple elements of the Mueller scattering matrix. However, the inference of the scatterers' properties (e.g., the size distribution function and refractive index) from such measurements involves solving an ill-conditioned inverse problem. In this paper, a new inversion technique was demonstrated to infer particle properties from PMS measurements. The new technique formulated the inverse problem into a minimization problem, which is then solved by the simulated annealing technique. Both numerical and experimental investigation on the new inversion technique was presented in the paper. The results obtained demonstrated the robustness and reliability of the new algorithm, and supported its expanded applications in scientific and technological areas involving particulates/aerosols.

Ma, Lin [Clemson University; Kranendonk, Laura [ORNL; Cai, Weiwei [Clemson University; Zhao, Yan [Clemson University; Baba, Justin S [ORNL

2009-01-01

324

A kinematical approach to gravitational lensing using new formulae for refractive index and acceleration  

E-print Network

This paper uses the Schwarzschild metric to derive an effective refractive index and acceleration vector that account for relativistic deflection of light rays, in an otherwise classical kinematic framework. The new refractive index and the known path equation are integrated to give accurate results for travel time and deflection angle, respectively. A new formula for coordinate acceleration is derived which describes the path of a massless test particle in the vicinity of a spherically symmetric mass density distribution. A standard ray-shooting technique is used to compare the deflection angle and time delay predicted by this new formula with the previously calculated values, and with standard first order approximations. Finally, the ray shooting method is used in theoretical examples of strong and weak lensing, reproducing known observer-plane caustic patterns for multiple masses.

S. J. Walters; L. K. Forbes; P. D. Jarvis

2010-08-17

325

Measurement of air refractive index based on surface plasmon resonance and phase detection.  

PubMed

A method for refractive index of air measurement is presented based on surface plasmon resonance (SPR) and phase detection using a dual-frequency laser interferometer. Theoretical analyses indicate that the phase-difference variation of the measurement signal versus the reference signal is linear with refractive index of air (RIA) fluctuation, and the calculation formula of RIA is derived. The structure design of the self-adaptive SPR sensor greatly reduces the measurement error resulting from the incident angle shift and improves the sensitivity. The experiments show that measurement uncertainty of 10(-6) order has been achieved when phase detection precision is 0.1°. The phenomenon of sudden phase variation during air pumping and air filling, which is caused by temperature fluctuation, is discussed. PMID:22825177

Chen, Qianghua; Luo, Huifu; Wang, Sumei; Wang, Feng

2012-07-15

326

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

327

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

328

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

329

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

330

Numerical simulations of negative-index refraction in wedge-shaped metamaterials Z. G. Dong, S. N. Zhu,* and H. Liu  

E-print Network

Numerical simulations of negative-index refraction in wedge-shaped metamaterials Z. G. Dong, S. N to evalu- ate its refraction behavior. Four frequency bands, namely, the stop band, left-handed band, ultralow-index band, and positive-index band, are distinguished according to the refracted field

Cao, Wenwu

331

Direct measurements of the nonlinear index of refraction of water at 815 and 407 nm using single-shot supercontinuum spectral interferometry  

E-print Network

Direct measurements of the nonlinear index of refraction of water at 815 and 407 nm using single-shot supercontinuum spectral interferometry was used to measure the nonlinear index of refraction due to the optical index of refraction of water is a key physi- cal parameter for any underwater use of high-powered lasers

Milchberg, Howard

332

Prediction and observation of tin and silver plasmas with index of refraction greater than one in the soft x-ray range  

E-print Network

temperature and density. We have used the code to predict plasmas that will have an index of refractionPrediction and observation of tin and silver plasmas with index of refraction greater than one and the experimental confirmation that doubly ionized Ag and Sn plasmas can have an index of refraction greater than

Rocca, Jorge J.

333

Refractive index determination of nanoparticles in suspension using nanoparticle tracking analysis.  

PubMed

The refractive index (RI) dictates interaction between light and nanoparticles and therefore is important to health, environmental, and materials sciences. Using nanoparticle tracking analysis, we have determined the RI of heterogeneous particles <500 nm in suspension. We demonstrate feasibility of distinguishing silica and polystyrene beads based on their RI. The hitherto unknown RI of extracellular vesicles from human urine was determined at 1.37 (mean). This method enables differentiation of single nanoparticles based on their RI. PMID:25256919

van der Pol, Edwin; Coumans, Frank A W; Sturk, Auguste; Nieuwland, Rienk; van Leeuwen, Ton G

2014-11-12

334

Photoinduced refractive-index changes in two-mode, elliptical-core fibers: sensing applications.  

PubMed

Photoinduced refractive-index changes in two-mode, elliptical-core optical fibers are shown to affect the differential phase modulation between the LP(01) and the LP(11)(even) modes. This change in beat length is dependent on the amount of strain induced in the fiber while the grating is being formed. We present experimental results that agree with conventional coupled-mode theory and propose the use of such sensors for weighted and distributed applications. PMID:19777027

Vengsarkar, A M; Greene, J A; Murphy, K A

1991-10-01

335

Switching management in couplers with biharmonic longitudinal modulation of refractive index  

E-print Network

We address light propagation in couplers with longitudinal biharmonic modulation of refractive index in neighboring channels. While simplest single-frequency out-of-phase modulation allows suppression of coupling for strictly defined set of resonant frequencies, the addition of modulation on multiple frequency dramatically modifies the structure of resonances. Thus, additional modulation on double frequency may suppress primary resonance, while modulation on triple frequency causes fusion of primary and secondary resonances.

Kartashov, Yaroslav V

2009-01-01

336

Switching management in couplers with biharmonic longitudinal modulation of refractive index.  

PubMed

We address light propagation in couplers with longitudinal biharmonic modulation of refractive index in neighboring channels. While simplest single-frequency out-of-phase modulation allows suppression of coupling for a strictly defined set of resonant frequencies, the addition of modulation on multiple frequencies dramatically modifies the structure of resonances. Thus, additional modulation on a double frequency may suppress the primary resonance, while modulation on a triple frequency causes fusion of primary and secondary resonances. PMID:19927205

Kartashov, Yaroslav V; Vysloukh, Victor A

2009-11-15

337

Switching management in couplers with biharmonic longitudinal modulation of refractive index  

Microsoft Academic Search

We address light propagation in couplers with longitudinal biharmonic modulation of refractive index in neighboring channels. While simplest single-frequency out-of-phase modulation allows suppression of coupling for strictly defined set of resonant frequencies, the addition of modulation on multiple frequency dramatically modifies the structure of resonances. Thus, additional modulation on double frequency may suppress primary resonance, while modulation on triple frequency

Yaroslav V. Kartashov; Victor A. Vysloukh

2009-01-01

338

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

339

Role of molecular symmetries in magneto-spatial dispersional change of the refractive index in fluids  

Microsoft Academic Search

Variations in refractive index due to the (B0 . k) effect are calculated for a circularly polarized light wave. The effect is related with the mechanism of nonlinear electron distortion in a field B0 described by an i-tensor of rank 4 and the reorientation mechanism represented by the product of two c-tensors, of ranks 3 and 1. The magnetic classes

S. Wozniak; R. Zawodny

1981-01-01

340

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

341

Periodic analysis of a 2-D negative refractive index transmission line structure  

Microsoft Academic Search

The propagation characteristics of a two-dimensional (2-D) negative refractive index (NRI) transmission line (TL) structure are explained using Bloch theory. Bloch analysis of a generalized 2-D periodic electrical network is performed and the results are applied to the NRI TL structure. A 2-D Brillouin diagram of the NRI TL metamaterial is presented and its band structure is intuitively explained. Voltage

Anthony Grbic; George V. Eleftheriades

2003-01-01

342

Needle-based refractive index measurement using low-coherence interferometry  

Microsoft Academic Search

We present a novel needle-based device for the measurement of refractive index and scattering using low-coherence interferometry. Coupled to the sample arm of an optical coherence tomography system, the device detects the scattering response of, and optical path length through, a sample residing in a fixed-width channel. We report use of the device to make near-infrared measurements of tissues and

Adam M. Zysk; Steven G. Adie; Julian J. Armstrong; Matthew S. Leigh; Alexandre Paduch; David D. Sampson; Freddy T. Nguyen; Stephen A. Boppart

2007-01-01

343

Measurements of refractive index sensitivity using long-period grating refractometer  

Microsoft Academic Search

We report the development and demonstration of a long-period grating refractometer. The principle of operation is based on the using of a long-period grating that is structurally induced by a CO2 laser, and where the resonance wavelengths are shifted as the refractive index of medium surrounding the cladding of the long-period grating. The different concentrations for three types of solutions

Joo Hin Chong; Ping Shum; H. Haryono; A. Yohana; M. K Rao; Chao Lu; Yinian Zhu

2004-01-01

344

A spatial refractive index sensor using whispering gallery modes in an optically trapped microsphere  

Microsoft Academic Search

We propose the use of an optically trapped, dye doped polystyrene microsphere\\u000afor spatial probing of the refractive index at any position in a fluid. We\\u000ademonstrate the use of the dye embedded in the microsphere as an internal\\u000abroadband excitation source, thus eliminating the need for a tunable excitation\\u000asource. We measured the full width at half maximum of

Peter Zijlstra; Karen L. van der Molen; Allard P. Mosk

2006-01-01

345

Refractive-index measurements using an integrated Mach-Zehnder interferometer  

Microsoft Academic Search

In this paper a refractometer system with an integrated optical sensor is presented. The sensitive element is a single or multichannel Mach-Zehnder interferometer (MZI) fabricated on silicon using waveguides made from SiO2 and SiON. The refractometer allows for real-time monitoring of refractive indices of gases and liquids in an index range between 1 and 1.49 using the silicon MZI as

Th Schubert; N Haase; H Kück; R Gottfried-Gottfried

1997-01-01

346

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

347

Enhanced light extraction of Bi3Ge4O12 scintillator by graded-refractive-index antireflection coatings  

NASA Astrophysics Data System (ADS)

A three-layer graded-refractive-index antireflection coating is designed and prepared on the one surface of the Bi3Ge4O12 scintillator by sol-gel technology. The emission intensity of the Bi3Ge4O12 with a graded-refractive-index antireflection coating exhibits a broadband and omnidirectional enhancement of 15.9% compared with the reference sample without coating. This significant enhancement is attributed to the decrease of Fresnel reflection, which is consistent with the measurement of transmission spectra. Additionally, it is evident that the graded-refractive-index coating is superior to the conventional quarter-wave coating due to the omnidirectionality advantage.

Tong, Fei; Liu, Bo; Chen, Hong; Zhu, Zhichao; Gu, Mu

2013-08-01

348

Multiple scattering of matter waves: An analytic model of the refractive index for atomic and molecular gases  

SciTech Connect

We present an analytic model of the refractive index for matter waves propagating through atomic or molecular gases. The model, which combines the Wentzel-Kramers-Brillouin (WKB) treatment of the long-range attraction with the Fraunhofer model treatment of the short-range repulsion, furnishes a refractive index in compelling agreement with recent experiments of Jacquey et al. [Phys. Rev. Lett. 98, 240405 (2007)] on Li atom matter waves passing through dilute noble gases. We show that the diffractive contribution, which arises from scattering by a two-dimensional 'hard core' of the potential, is essential for obtaining a correct imaginary part of the refractive index.

Lemeshko, Mikhail; Friedrich, Bretislav [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

2010-08-15

349

Measurement of refractive index change induced by dark reaction of photopolymer with digital holographic quantitative phase microscopy  

NASA Astrophysics Data System (ADS)

Light-induced refractive index change in photopolymer is quantified by a digital holographic microscope. The refractive index change is induced as the dark reaction which proceeds inside the photopolymer after a writing beam is stopped. Time-lapse phase distribution across the photopolymer is measured by the off-axis digital holographic microscope which enables us to retrieve the 2-D phase map from a single hologram. It is found that the initial phase profile does not coincide with the illumination intensity distribution. This observation suggests that the rate of the refractive index change in dark reaction is not proportional to the illumination intensity in case the exposure energy becomes high.

Arimoto, Hidenobu; Watanabe, Wataru; Masaki, Kazuyoshi; Fukuda, Takashi

2012-11-01

350

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

351

Performance limits to the operation of nanoplasmonic chemical sensors: noise-equivalent refractive index and detectivity  

NASA Astrophysics Data System (ADS)

We considered figures of merit for chemical and biological sensors based on plasmonic structures and utilizing adsorption/desorption mechanism. The operation of these devices in general is limited by noise determining the minimum detectable refractive-index change. We dedicated our work to the intrinsic noise mechanisms connected with the plasmonic process itself. In contrast, most of the available literature is almost exclusively dedicated to the external noise sources (illumination source and photodetector). Reviewing the refractive-index fluctuations caused by thermal, adsorption-desorption and 1/f noise, we observed a striking analogy between the qualitative behavior of noise in (nano)plasmonic devices and that in semiconductor infrared detectors. The power spectral densities for noise in both of these have an almost identical shape; the adsorption-desorption noise corresponds to generation-recombination processes in detectors, while the other two mechanisms exist in the both types of the devices. Thus the large and mature existing apparatus for infrared detector noise analysis may be applied to the plasmonic sensors. Based on the observed analogy, we formulated the noise-equivalent refractive-index and the specific detectivity as the figures of merit to analyze the ultimate performance of plasmon sensors. The approach is valid for conventional surface plasmon resonance sensors, but also for nanoplasmonic and metamaterial-based devices.

Jaksic, Zoran; Jaksic, Olga; Matovic, Jovan

2009-04-01

352

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

353

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

SciTech Connect

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 (?{sub 0}?=?5.29?mm), the zoned fishnet metamaterial lens, designed to have a focal length FL?=?9?{sub 0}, exhibits a refractive index n?=??0.25. The focusing performance of the diffractive optical element is briefly compared with that of a non-zoned fishnet metamaterial lens and an isotropic homogeneous zoned lens made of a material with the same refractive index. Experimental and numerically-computed radiation diagrams of the fabricated zoned lens are presented and compared in detail with that of a simulated non-zoned lens. Simulation and experimental results are in good agreement, demonstrating an enhancement generated by the zoned lens of 10.7?dB, corresponding to a gain of 12.26?dB. Moreover, beam steering capability of the structure by shifting the feeder on the xz-plane is demonstrated.

Pacheco-Peña, V., E-mail: victor.pacheco@unavarra.es; Orazbayev, B., E-mail: b.orazbayev@unavarra.es; Beaskoetxea, U., E-mail: unai.beaskoetxea@unavarra.es; Beruete, M., E-mail: miguel.beruete@unavarra.es [TERALAB (MmW—THz—IR and Plasmonics Laboratory), Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona (Spain); Navarro-Cía, M., E-mail: m.navarro@imperial.ac.uk [Optical and Semiconductor Devices Group, Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2BT (United Kingdom); Centre for Plasmonics and Metamaterials, Imperial College London, London SW7 2AZ (United Kingdom); Centre for Terahertz Science and Engineering, Imperial College London, London SW7 2AZ (United Kingdom)

2014-03-28

354

Determining the refractive index of shocked [100] lithium fluoride to the limit of transmissibility  

NASA Astrophysics Data System (ADS)

Lithium fluoride (LiF) is a common window material used in shock- and ramp-compression experiments because it displays a host of positive attributes in these applications. Most commonly, it is used to maintain stress at an interface and velocimetry techniques are used to record the particle velocity at that interface. In this application, LiF remains transparent to stresses up to 200 GPa. In this stress range, LiF has an elastic-plastic response with a very low (<0.5 GPa) elastic precursor and exhibits no known solid-solid phase transformations. However, because the density dependence of the refractive index of LiF does not follow the Gladstone-Dale relation, the measured particle velocity at this interface is not the true particle velocity and must be corrected. For that reason, the measured velocity is often referred to as the apparent velocity in these types of experiments. In this article, we describe a series of shock-compression experiments that have been performed to determine the refractive index of LiF at the two most commonly used wavelengths (532 nm and 1550 nm) between 35 and 200 GPa to high precision. A modified form of the Gladstone-Dale relation was found to work best to fit the determined values of refractive index. In addition, we provide a direct relationship between the apparent and true particle velocity to correct experimentally obtained wave profiles by others using these velocimetry techniques.

Rigg, P. A.; Knudson, M. D.; Scharff, R. J.; Hixson, R. S.

2014-07-01

355

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

356

Experimental study of liquid refractive index sensing based on a U-shaped optical fiber  

NASA Astrophysics Data System (ADS)

A U-shaped optical fiber sensing system designed to measure the refractive index of liquid had been proposed. The sensing mechanism of U-shaped optical fiber was discussed. A general single-mode fiber was bent into U-shaped and partially cladding of U-shaped fiber was corroded by HF acid buffer solution. Powers of different diameters of U-shaped fibers had been measured by many experiments. The results showed that the diameter of U-shaped fiber cladding 40 ?m and the diameter of U-shaped was 1 cm were suitable to measure liquid refractive index. Then, this U-shaped optical fiber was immersed in liquid, such as pure water, ethanol, acetone and isopropanol, respectively. The evanescent field of the U-shaped fiber should be modulated by the liquid. The optical signal in the U-shaped fiber was measured with the optical spectrum analyzers(OSA). Finally, the experimental results were analyzed, and the spectra in the air was selected as a reference. The relative intensity was obtained for the different liquid. These results showed that the relative intensity of the liquid had a good linear relationship. This sensing device could accurately demarcate refractive index of liquid. It is simple, low cost, and it can also be applied in measuring the level of liquid.

Zhang, Zhi; Yan, Haitao; Li, Liben; Wang, Ming

2013-12-01

357

Contrast-enhanced digital holographic imaging of cellular structures by manipulating the intracellular refractive index.  

PubMed

The understanding of biological reactions and evaluation of the significance for living cells strongly depends on the ability to visualize and quantify these processes. Digital holographic microscopy (DHM) enables quantitative phase contrast imaging for high resolution and minimal invasive live cell analysis without the need of labeling or complex sample preparation. However, due to the rather homogeneous intracellular refractive index, the phase contrast of subcellular structures is limited and often low. We analyze the impact of the specific manipulation of the intracellular refractive index by microinjection on the DHM phase contrast. Glycerol is chosen as osmolyte, which combines high solubility in aqueous solutions and biological compatibility. We show that the intracellular injection of glycerol causes a contrast enhancement that can be explained by a decrease of the cytosolic refractive index due to a water influx. The underlying principle is proven by experiments inducing cell shrinkage and with fixated cells. The integrity of the cell membrane is considered as a prerequisite and allows a reversible cell swelling and shrinking within a certain limit. The presented approach to control the intracellular phase contrast demonstrated for the example of DHM opens prospects for applications with other quantitative phase contrast imaging methods. PMID:20799787

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

2010-01-01

358

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

PubMed

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. PMID:25419536

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

2014-02-27

359

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

360

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

SciTech Connect

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, E-mail: leoxyt@mail.xjtu.edu.cn; Ling Wu, Ling; Chen Li, Di [State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710049 (China)

2014-03-03

361

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

362

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

363

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

364

High sensitivity refractive index gas sensing enhanced by surface plasmon resonance with nano-cavity antenna array  

NASA Astrophysics Data System (ADS)

The surface plasmon resonance gas sensor is presented for refractive index detection using nano-cavity antenna array. The gas sensor monitors the changes of the refractive index by measuring the spectral shift of the resonance dip, for modulating the wavelength of incident light. It is demonstrated that minute changes in the refractive index of a medium close to the surface of a metal film, owing to a shift in the resonance dip of the wavelength, can be detected. The average detection sensitivity is about 3200 nm/RIU (refractive index units), which is more than twice that of a metal grating-based gas sensor. The reflectivity of the surface plasmon resonance dip is only ~ 0.03%, and the full widths at half maximum (FWHMs) of bandwidth of the angle and wavelength are ~ 0.20° and 4.71 nm, respectively.

Zhao, Hua-Jun

2012-08-01

365

Fabrication of gradient refractive index ball lenses using the method of combination of ion exchanging and sagging  

NASA Astrophysics Data System (ADS)

Based on the Fick's diffusion equations, the distribution function of refractive index of a gradient refractive index ball lens (GRIN ball lens/GBL) is derived. Lithium containing silicate glass is fabricated and GRIN ball lenses (GBLs) which diameters are from 0.3 mm to 3.0 mm are made by the method of combination of Ion exchanging and sagging in sodium nitrate. Refractive index profiles of these GBLs are measured by interferometer, and the performances such as effective focal length (EFL), back focal length (BFL) and numerical aperture (NA) between GBLs and homogeneous ball lenses (HBLs) are compared. Results show that the distribution of the index of refraction is parabolic curve and its ? n is about 0.0002, the performances of the former are super to the latter.

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

2007-08-01

366

Ion migration assisted inscription of high refractive index contrast waveguides by femtosecond laser pulses in phosphate glass.  

PubMed

In this Letter, we report on the successful fabrication of low loss, high refractive index contrast waveguides via ion migration upon femtosecond laser writing in phosphate glass. Waveguides were produced in two different phosphate glass compositions with high and low La(2)O(3) content. In the La-rich glass, a large refractive index increase in the guiding region was observed due to the incoming migration of La accompanied by the out-diffusion of K. The much smaller refractive index change in the La-less glass is caused by rearrangements of the glass structure. These results confirm the feasibility of adapting the glass composition for enabling the laser writing of high refractive index contrast structures via spatially selective modification of the glass composition. PMID:24322229

Toney Fernandez, T; Haro-González, P; Sotillo, B; Hernandez, M; Jaque, D; Fernandez, P; Domingo, C; Siegel, J; Solis, J

2013-12-15

367

Analysis of scattering by spheres having a negative acoustical refractive index  

NASA Astrophysics Data System (ADS)

Electromagnetic waves having oppositely directed phase and group velocities propagate in metamaterials having a negative permeability and negative permittivity [J. B. Pendry and D. R. Smith, Phys. Today 57(6), 37-44 (2004)]. Such materials are predicted to have unusual electromagnetic scattering properties [R. Ruppin, Solid State Commun. 116, 411-415 (2000)]. If it is possible to fabricate acoustical materials having a simultaneously negative effective elastic modulus and density (in a dynamical sense), the mechanical energy flux will have the opposite direction as the wave-vector associated with phase evolution. Rays descriptive of the energy flux refracted by such hypothetical materials at interfaces with ordinary fluids would be characterized by a negative acoustical refractive index. Partial-wave-series calculations of high frequency scattering by fluid spheres having an acoustical refractive index at (or close to) 1 reveal backscattering enhancements associated with glory rays which, unlike ordinary spheres [P. L. Marston and D. S. Langley, J. Acoust. Soc. Am. 73, 1464-1475 (1983)], require only a single internal chord. Generalized Lamb waves on elastic shells having opposite phase and group velocities also cause enhanced backscattering associated with unusual rays [G. Kaduchak, D. H. Hughes, and P. L. Marston, J. Acoust. Soc. Am. 96, 3704-3714 (1994)].

Marston, Philip L.

2005-04-01

368

Dirac cones induced by accidental degeneracy in photonic crystals and zero-refractive-index materials  

NASA Astrophysics Data System (ADS)

A zero-refractive-index metamaterial is one in which waves do not experience any spatial phase change, and such a peculiar material has many interesting wave-manipulating properties. These materials can in principle be realized using man-made composites comprising metallic resonators or chiral inclusions, but metallic components have losses that compromise functionality at high frequencies. It would be highly desirable if we could achieve a zero refractive index using dielectrics alone. Here, we show that by employing accidental degeneracy, dielectric photonic crystals can be designed and fabricated that exhibit Dirac cone dispersion at the centre of the Brillouin zone at a finite frequency. In addition to many interesting properties intrinsic to a Dirac cone dispersion, we can use effective medium theory to relate the photonic crystal to a material with effectively zero permittivity and permeability. We then numerically and experimentally demonstrate in the microwave regime that such dielectric photonic crystals with reasonable dielectric constants manipulate waves as if they had near-zero refractive indices at and near the Dirac point frequency.

Huang, Xueqin; Lai, Yun; Hang, Zhi Hong; Zheng, Huihuo; Chan, C. T.

2011-08-01

369

SnO{sub 2} nanoparticles in silica: Nanosized tools for femtosecond-laser machining of refractive index patterns  

SciTech Connect

We show that SnO{sub 2} nanoclusters in silica interact with ultrashort infrared laser pulses focused inside the material generating a hydrostatic compression and photoelastic response of the surrounding glass. This effect, together with the laser-induced nanocluster amorphization, gives rise to positive or negative refractive-index changes, up to 10{sup -2}, depending on the beam-power density. This result points out a wide tuning of the refractive index patterns obtainable in silica-based optical technology.

Paleari, A.; Franchina, E.; Chiodini, N.; Lauria, A.; Bricchi, E.; Kazansky, P.G. [CNISM and Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, via Cozzi 53, I-20125 Milan (Italy); Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2006-03-27

370

An integrated solution for mold shape modification in precision glass molding to compensate refractive index change and geometric deviation  

NASA Astrophysics Data System (ADS)

In precision glass molding, refractive index change and geometric deviation (or curve change as often referred to in industry) occurred during molding process can result in substantial amount of aberrations. Previously, refractive index change and geometric deviation were investigated in separate studies by the authors. However, optical performance of a molded glass lens depends on both refractive index and geometry. In order to mold lenses with optimal performance, both refractive index change and geometric deviation have to be taken into consideration simultaneously and compensated. This paper presented an integrated compensation procedure for modifying molds to compensate both refractive index change and geometric deviation. Group refractive index change predicted by the finite element method simulation was used to provide a modified geometry design for a desired lens. Geometric deviations of molded glass lenses with the modified design were analyzed with a previously developed numerical simulation approach, which is used to modify the mold shape. This procedure was validated by molding a generic aspherical glass lens. Both geometry and optical measurement results confirmed that the molded lens performed as specified by the original design. It also demonstrated that finite element method assisted compensation procedure can be used to predict the final optical performance of compression molded glass components. This research provided an opportunity for optics manufacturers to achieve better performance lens while maintaining lower cost and a shorter cycle time.

Su, Lijuan; Wang, Fei; He, Peng; Dambon, Olaf; Klocke, Fritz; Yi, Allen Y.

2014-02-01

371

Pressure Sensing in High-Refractive-Index Liquids Using Long-Period Gratings Nanocoated with Silicon Nitride  

PubMed Central

The paper presents a novel pressure sensor based on a silicon nitride (SiNx) nanocoated long-period grating (LPG). The high-temperature, radio-frequency plasma-enhanced chemical-vapor-deposited (RF PECVD) SiNx nanocoating was applied to tune the sensitivity of the LPG to the external refractive index. The technique allows for deposition of good quality, hard and wear-resistant nanofilms as required for optical sensors. Thanks to the SiNx nanocoating it is possible to overcome a limitation of working in the external-refractive-index range, which for a bare fiber cannot be close to that of the cladding. The nanocoated LPG-based sensing structure we developed is functional in high-refractive-index liquids (nd > 1.46) such as oil or gasoline, with pressure sensitivity as high as when water is used as a working liquid. The nanocoating developed for this experiment not only has the highest refractive index ever achieved in LPGs (n > 2.2 at ? = 1,550 nm), but is also the thinnest (<100 nm) able to tune the external-refractive-index sensitivity of the gratings. To the best of our knowledge, this is the first time a nanocoating has been applied on LPGs that is able to simultaneously tune the refractive-index sensitivity and to enable measurements of other parameters. PMID:22163527

Smietana, Mateusz; Bock, Wojtek J.; Mikulic, Predrag; Chen, Jiahua

2010-01-01

372

Optical tomography reconstruction algorithm based on the radiative transfer equation considering refractive index: Part 2. Inverse model.  

PubMed

This paper is the second part of the study of optical tomography based on radiative transfer equation considering refractive index, namely the inverse model which reconstruct the image from the data obtained from the forward model in the first part of this study. In the forward model, we divided the problem into two cases: one is the uniform refractive index and the other is the gradient refractive index. We also use the human brain phantom which contains void-like region to test the forward model, the experiment result shows that the simulation agrees well with the theoretical model. Similarly, in the inverse model, we also consider the reconstruct scheme in two cases as above. In the case of uniform refractive index, we use the adjoint difference method to calculate the gradient of the objective function. In the case of gradient refractive index, we use Lagrangian formalism method to obtain the formula of the gradient. In order to test the reconstruct algorithm, we use the image which was used in the forward model as the predicted data. From the reconstruct image, we can see the case of gradient refractive index agrees with the original image more closer. This shows that the reconstruct algorithm we used is robust and effective. PMID:23484634

Guan, Jinlan; Fang, Shaomei; Guo, Changhong

2013-04-01

373

Optical tomography reconstruction algorithm based on the radiative transfer equation considering refractive index--Part 1: Forward model.  

PubMed

The present study consists of two parts. The overall goal is to introduce and experimentally test the optical tomographic imaging algorithm based on the radiative transfer equation considering the refractive index. Considering that the high scattering medium with void-like regions has very low absorption and scattering coefficients, we use the radiative transfer equation to describe the optical parameters of the medium. In the process of photo propagation, not only the absorption and scattering coefficients have impact on the light radiance, but also the refractive index affect the light radiance. Therefore, we focus on the impact of the refractive index in this present study. We divide the refractive index into two cases: the uniform refractive index and the gradient refractive index. The paper is the first part of the present study, namely the forward model. We calculate the derivative of the fluency with the optical parameters by upwind-difference method, and a simpler mathematical framework is obtained in our study. In order to verify the accuracy of the forward model, we select the human brain phantom image with a void-like region and tumor as the experimental data. We found that the experimental measurements are in good agreement with the theoretical predictions of the measurements. PMID:23453610

Guan, Jinlan; Fang, Shaomei; Guo, Changhong

2013-04-01

374

A Highly Sensitive Fiber Optic Sensor Based on Two-Core Fiber for Refractive Index Measurement  

PubMed Central

A simple and compact fiber optic sensor based on a two-core fiber is demonstrated for high-performance measurements of refractive indices (RI) of liquids. In order to demonstrate the suitability of the proposed sensor to perform high-sensitivity sensing in a variety of applications, the sensor has been used to measure the RI of binary liquid mixtures. Such measurements can accurately determine the salinity of salt water solutions, and detect the water content of adulterated alcoholic beverages. The largest sensitivity of the RI sensor that has been experimentally demonstrated is 3,119 nm per Refractive Index Units (RIU) for the RI range from 1.3160 to 1.3943. On the other hand, our results suggest that the sensitivity can be enhanced up to 3485.67 nm/RIU approximately for the same RI range. PMID:24152878

Guzmán-Sepúlveda, José Rafael; Guzmán-Cabrera, Rafael; Torres-Cisneros, Miguel; Sánchez-Mondragón, José Javier; May-Arrioja, Daniel Alberto

2013-01-01

375

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

376

Fabrication Quality Analysis of a Fiber Optic Refractive Index Sensor Created by CO2 Laser Machining  

PubMed Central

This study investigates the CO2 laser-stripped partial cladding of silica-based optic fibers with a core diameter of 400 ?m, which enables them to sense the refractive index of the surrounding environment. However, inappropriate treatments during the machining process can generate a number of defects in the optic fiber sensors. Therefore, the quality of optic fiber sensors fabricated using CO2 laser machining must be analyzed. The results show that analysis of the fiber core size after machining can provide preliminary defect detection, and qualitative analysis of the optical transmission defects can be used to identify imperfections that are difficult to observe through size analysis. To more precisely and quantitatively detect fabrication defects, we included a tensile test and numerical aperture measurements in this study. After a series of quality inspections, we proposed improvements to the existing CO2 laser machining parameters, namely, a vertical scanning pathway, 4 W of power, and a feed rate of 9.45 cm/s. Using these improved parameters, we created optical fiber sensors with a core diameter of approximately 400 ?m, no obvious optical transmission defects, a numerical aperture of 0.52 ± 0.019, a 0.886 Weibull modulus, and a 1.186 Weibull-shaped parameter. Finally, we used the optical fiber sensor fabricated using the improved parameters to measure the refractive indices of various solutions. The results show that a refractive-index resolution of 1.8 × 10?4 RIU (linear fitting R2 = 0.954) was achieved for sucrose solutions with refractive indices ranging between 1.333 and 1.383. We also adopted the particle plasmon resonance sensing scheme using the fabricated optical fibers. The results provided additional information, specifically, a superior sensor resolution of 5.73 × 10?5 RIU, and greater linearity at R2 = 0.999. PMID:23535636

Chen, Chien-Hsing; Yeh, Bo-Kuan; Tang, Jaw-Luen; Wu, Wei-Te

2013-01-01

377

Fabrication quality analysis of a fiber optic refractive index sensor created by CO2 laser machining.  

PubMed

This study investigates the CO2 laser-stripped partial cladding of silica-based optic fibers with a core diameter of 400 ?m, which enables them to sense the refractive index of the surrounding environment. However, inappropriate treatments during the machining process can generate a number of defects in the optic fiber sensors. Therefore, the quality of optic fiber sensors fabricated using CO2 laser machining must be analyzed. The results show that analysis of the fiber core size after machining can provide preliminary defect detection, and qualitative analysis of the optical transmission defects can be used to identify imperfections that are difficult to observe through size analysis. To more precisely and quantitatively detect fabrication defects, we included a tensile test and numerical aperture measurements in this study. After a series of quality inspections, we proposed improvements to the existing CO2 laser machining parameters, namely, a vertical scanning pathway, 4 W of power, and a feed rate of 9.45 cm/s. Using these improved parameters, we created optical fiber sensors with a core diameter of approximately 400 ?m, no obvious optical transmission defects, a numerical aperture of 0.52 ± 0.019, a 0.886 Weibull modulus, and a 1.186 Weibull-shaped parameter. Finally, we used the optical fiber sensor fabricated using the improved parameters to measure the refractive indices of various solutions. The results show that a refractive-index resolution of 1.8 × 10(-4) RIU (linear fitting R2 = 0.954) was achieved for sucrose solutions with refractive indices ranging between 1.333 and 1.383. We also adopted the particle plasmon resonance sensing scheme using the fabricated optical fibers. The results provided additional information, specifically, a superior sensor resolution of 5.73 × 10(-5) RIU, and greater linearity at R2 = 0.999. PMID:23535636

Chen, Chien-Hsing; Yeh, Bo-Kuan; Tang, Jaw-Luen; Wu, Wei-Te

2013-01-01

378

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

379

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

NASA Astrophysics Data System (ADS)

Sensing using surface plasmon resonances is one of the most promising practical applications of plasmonic nanostructures and Fano resonances allow achieving a lower detection limit thanks to their narrow spectral features. However, a narrow spectral width of the subradiant mode in a plasmonic system, as observed in the weak coupling regime, is in general associated with a low modulation of the complete spectral response. In this article, we show that this limitation can be overcome by a nonlinear approach based on second harmonic generation and its dependence on symmetry at the nanoscale. The Fano resonant systems considered in this work are gold nanodolmens. Their linear and nonlinear responses are evaluated using a surface integral equation method. The numerical results demonstrate that a variation of the refractive index of the surrounding medium modifies the coupling between the dark and bright modes, resulting in a modification of the electromagnetic wave scattered at the second harmonic wavelength, especially the symmetry of the nonlinear emission. Reciprocally, we show that evaluating the asymmetry of the nonlinear emission provides a direct measurement of the gold nanodolmens dielectric environment. Interestingly, the influence of the refractive index of the surrounding medium on the nonlinear asymmetry parameter is approximately 10 times stronger than on the spectral position of the surface plasmon resonance: hence, smaller refractive index changes can be detected with this new approach. Practical details for an experimental realization of this sensing scheme are discussed and the resolution is estimated to be as low as ?n = 1.5 × 10-3, respectively 1.5 × 10-5, for an acquisition time of 60 s for an isolated gold nanodolmen, respectively an array of 10 × 10 nanodolmens.Sensing using surface plasmon resonances is one of the most promising practical applications of plasmonic nanostructures and Fano resonances allow achieving a lower detection limit thanks to their narrow spectral features. However, a narrow spectral width of the subradiant mode in a plasmonic system, as observed in the weak coupling regime, is in general associated with a low modulation of the complete spectral response. In this article, we show that this limitation can be overcome by a nonlinear approach based on second harmonic generation and its dependence on symmetry at the nanoscale. The Fano resonant systems considered in this work are gold nanodolmens. Their linear and nonlinear responses are evaluated using a surface integral equation method. The numerical results demonstrate that a variation of the refractive index of the surrounding medium modifies the coupling between the dark and bright modes, resulting in a modification of the electromagnetic wave scattered at the second harmonic wavelength, especially the symmetry of the nonlinear emission. Reciprocally, we show that evaluating the asymmetry of the nonlinear emission provides a direct measurement of the gold nanodolmens dielectric environment. Interestingly, the influence of the refractive index of the surrounding medium on the nonlinear asymmetry parameter is approximately 10 times stronger than on the spectral position of the surface plasmon resonance: hence, smaller refractive index changes can be detected with this new approach. Practical details for an experimental realization of this sensing scheme are discussed and the resolution is estimated to be as low as ?n = 1.5 × 10-3, respectively 1.5 × 10-5, for an acquisition time of 60 s for an isolated gold nanodolmen, respectively an array of 10 × 10 nanodolmens. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05623j

Butet, Jérémy; Martin, Olivier J. F.

2014-11-01

380

Finite element approximation of the radiative transport equation in a medium with piece-wise constant refractive index  

NASA Astrophysics Data System (ADS)

The radiative transport equation can be used as a light transport model in a medium with scattering particles, such as biological tissues. In the radiative transport equation, the refractive index is assumed to be constant within the medium. However, in biomedical media, changes in the refractive index can occur between different tissue types. In this work, light propagation in a medium with piece-wise constant refractive index is considered. Light propagation in each sub-domain with a constant refractive index is modeled using the radiative transport equation and the equations are coupled using boundary conditions describing Fresnel reflection and refraction phenomena on the interfaces between the sub-domains. The resulting coupled system of radiative transport equations is numerically solved using a finite element method. The approach is tested with simulations. The results show that this coupled system describes light propagation accurately through comparison with the Monte Carlo method. It is also shown that neglecting the internal changes of the refractive index can lead to erroneous boundary measurements of scattered light.

Lehtikangas, O.; Tarvainen, T.; Kim, A. D.; Arridge, S. R.

2015-02-01

381

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

382

Dopant-dependent reflectivity and refractive index of microcrystalline molybdenum-bronze thin films  

NASA Astrophysics Data System (ADS)

Reflectivity spectra of HxMoO3 and LixMoO3 thin films were measured over the photon energy range from 0.4 to 4.2 eV. It was found that microcrystalline molybdenum bronzes have reflectances between 6% and 30% over the concentration x, range 0?x?0.64. Values for the real part of the refractive index n were also determined from the refined reflectivity data using different numerical techniques depending upon the dispersive and nondispersive regions in the data. The values of high-frequency dielectric constant ?hf of ZxMoO3 (Z=H+,Li+) bronzes were determined from the refractive index data to estimate the effective electronic masses involved in the optical and/or polaronic transitions. We interpret the optical data using the modified Drude-Zener model together with a single-oscillator model to differentiate between bound and free electronic states. Using a single-oscillator model, the oscillator energy Ea and the dispersion energy Ed were found to increase and decrease, respectively, with increasing x values, opposite to what occurs in crystalline molybdenum bronzes. These findings support the fact that Bloch electrons are almost absent in the investigated microcrystalline bronzes. The small reflectivity crests and the observed shift of the minimum reflectivity (or minimum refractive index) toward higher frequency with increasing x value in ZxMoO3 appear to be consistent with polaronic hopping, which arises from the excitation of electrons from localized in-gap states of Mo5+ ions into higher impurity states of Mo6+ (or Mo4+) ions within the optical band gap.

Hussain, Zahid

2002-05-01

383

Measurement of the nonlinear refractive index of tellurite glass fiber by using induced grating autocorrelation technique  

NASA Astrophysics Data System (ADS)

Nonlinear phenomena in optical fibers have been attracting considerable attention because of the rapid growth of the fiber optics communication industry. The increasing demand in internet use and the expansion of telecommunications in the developing world have triggered the need for high capacity and ultra-fast communication devices and also the need to increase the number of transmission channels in the fibers. Wavelength Division Multiplexing (WDM) and Dense Wavelength Division Multiplexing (DWDM) systems are capable of transmitting large volumes of data at very high rates into huge numbers of optical transmission channels. This ability is limited by the gain bandwidth of Silica based fiber optics amplifiers already installed in the communication networks. Tellurite based fiber amplifiers offer the necessary bandwidth for amplification of WDM and DWDM channels. To investigate the nonlinear properties of the optical fibers in this research, we used a 10 picoseconds pulse width passively mode-locked Nd:Vanadate ( Nd:YVO4) laser operating at 1342nm with a repetition rate of 76 MHz. We accurately measured the nonlinear refractive index of single mode silica fibers utilizing the Induced Grating Autocorrelation (IGA) technique. IGA technique was extended furthermore to study nonlinear effects in multimode fibers, and for the first time, we successfully measured the nonlinear refractive index (n2) of a multimode silica fiber. Confident of the ability of IGA technique for determining n 2 of multimode silica fibers, we measured the nonlinear refractive index of multimode Tellurite glass fibers with length as short as 0.5 meter. The goal of this work is to provide accurate and reliable information on the nonlinear optical properties of Tellurite glass fibers, novel fibers with promising future for developing ultrafast and high transmission capacity communication devices.

Traore, Aboubakar

384

Long period fiber grating based refractive index sensor with enhanced sensitivity using Michelson interferometric arrangement  

NASA Astrophysics Data System (ADS)

The long period fiber grating (LPFG) is widely used as a sensor due to its high sensitivity and resolution. However, the broad bandwidth of the attenuation bands formed by the mode coupling between the fundamental core mode and the cladding modes constitutes a difficulty when the device is used as a conventional sensor. To overcome this limitation, a Michelson interferometer-type sensor configuration has been developed, using an LPFG grating pair formed by coating a mirror at the distal end of the LPFG. This sensor configuration is more convenient to use and is able to overcome the limitations of the single LPFG based sensor as the shifts in the attenuation bands being more easily detectable due to the formation of the sharp spectral fringe pattern in the LPFG based Michelson interferometer. In this work, I studied the LPFG based Michelson interferometer as the refractive index sensor and discussed the sensitivity enhancement of the LPFG based Michelson interferometer as a refractive index sensor by employing higher order cladding modes and by reducing the cladding radius. The results demonstrated the HE17 mode with a cladding radius of 62.5 ?m, in the range of surrounding refractive index (SRI) of 1-1.45, and its resonant peak showed a wavelength shift of 26.99 nm/RIU. When the cladding region was further reduced to 24 ?m, the resonant peak showed a wavelength shift of 569.88 nm/RIU, resulting in a sensitivity enhancement of nearly 21 times. However, as the cladding region was etched further, then the HE17 order cladding mode and higher mode would be cut off. Therefore, the implementation of high sensitivity for SRI sensing with the reduced cladding in the LPFG based Michelson interferometer is dependent on the proper combination of the cladding radius and cladding mode order.

Singh, Amit

2014-12-01

385

Highly birefringent suspended-core photonic microcells for refractive-index sensing  

NASA Astrophysics Data System (ADS)

An in-line photonic microcell with a highly birefringent suspended microfiber core is fabricated by locally heating and pressurizing selected air-holes of an endless single mode photonic crystal fiber. The microfiber core has rhombus-like cross-sectional geometry and could achieve a high birefringence of up to 10-2. The microfiber core is fixed at the center of the microcell by thin struts attached to an outer jacket tube, which protects and isolates the microfiber from environmental contaminations. Highly sensitive and robust refractive index sensors based on such microcells are experimentally demonstrated.

Wang, Chao; Jin, Wa; Liao, Changrui; Ma, Jun; Jin, Wei; Yang, Fan; Ho, Hoi Lut; Wang, Yiping

2014-08-01

386

Adaptive refinement and selection process through defect localization for reconstructing an inhomogeneous refraction index  

NASA Astrophysics Data System (ADS)

We consider the iterative reconstruction of both the internal geometry and the values of an inhomogeneous acoustic refraction index through a piecewise constant approximation. In this context, we propose two enhancements intended to reduce the number of parameters used in reconstruction, while preserving accuracy. This is achieved through the use of geometrical information obtained from a previously developed defect localization method. The first enhancement consists of a preliminary selection of relevant parameters, while the second one is an adaptive refinement to enhance precision with a low number of parameters. Each of them is numerically illustrated.

Grisel, Y.; Mouysset, V.; Mazet, P. A.; Raymond, J. P.

2014-06-01

387

Negative refractive index material-inspired 90-deg electrically tilted ultra wideband resonator  

NASA Astrophysics Data System (ADS)

A negative refractive index material loaded patch antenna is proposed for ultra wideband applications. The wideband operation has been achieved by creating a defected ground plane with a CNC shaped split ring resonator. The defected ground plane CNC resonator also exhibits a 90-deg electrical tilt. Two additional slots are engineered in the patch antenna for further bandwidth enhancement. A -10 dB bandwidth with an order of 57.89% has been achieved with a peak gain of 5.37 dBi at a 5.5 GHz resonant frequency. Measured results demonstrate good agreement with simulated results.

Upadhyaya, Trushit K.; Kosta, Shiv Prasad; Jyoti, Rajeev; Palandoken, Merih

2014-10-01

388

Fabrication of elliptic microfibers with CO2 laser for high-sensitivity refractive index sensing.  

PubMed

We propose a convenient method for achieving highly birefringent (HiBi) elliptic microfibers by use of the CO2-laser machining and the flame-brushing techniques. With optimization of fabrication process, a high birefringence of up to 2.10×10(-2) is experimentally obtained. Especially, within a polarization Sagnac interferometer acting as a refractive index (RI) sensor, both positive and abnormal negative sensitivity is measured, dependent on the geometrical variables of the HiBi microfiber. The maximum RI sensitivity is ?195,348??nm/RI-unit around RI=1.35887, which is the highest among the microfiber devices as reported, to our knowledge. PMID:24978529

Sun, Li-Peng; Li, Jie; Gao, Shuai; Jin, Long; Ran, Yang; Guan, Bai-Ou

2014-06-15

389

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

NASA Astrophysics Data System (ADS)

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.

Yong, Zehui; Lei, Dang Yuan; Lam, Chi Hang; Wang, Yu

2014-04-01

390

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

391

Refractive index fluctuations in solids: nanoprobing by means of single-molecule spectroscopy  

E-print Network

We suggest a novel approach for probing of local fluctuations of the refractive index $n$ in solids by means of single-molecule (SM) spectroscopy. It is based on the dependence $T_1(n)$ of the effective radiative lifetime $T_1$ of dye centres in solids on $n$ due to the local field effects. Detection of SM zero-phonon lines at ultra-low temperatures gives the values of SM natural spectral linewidth (which is inverse proportional to $T_1$) and makes it possible to reveal the distribution of the local $n$ values in solids. Here we demonstrate this possibility on the example of amorphous polyethylene and polycrystalline naphthalene doped with terrylene.

Anikushina, T A; Gorshelev, A A; Naumov, A V

2015-01-01

392

Multiplex in-cylinder pressure measurement utilizing an optical fiber with specific refractive-index composition.  

PubMed

An approach to multiplex in-cylinder pressure measurement that utilizes a single-mode optical fiber with specific refractive-index composition has been proposed. The sensing fiber has been designed to show a certain amount of optical power loss with a small change in the fiber-local-bend radius. Along with pressure-transferring diaphragms the sensing fiber was embedded into the head gasket of a four-cylinder gasoline engine. The internal-pressure change in each combustion chamber was detected on the basis of bending power loss in the fiber. Combustion pressure peaks for each cylinder were clearly observed. PMID:21085226

Komachiya, M; Sonobe, H; Oho, S; Kurita, M; Nakazawa, T; Sasayama, T

1996-03-01

393

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

SciTech Connect

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 Lingbao; Hou Zhiling; Jing Jian [School of Science and Beijing Key Laboratory of Environmentally Harmful Chemicals Assessment, Beijing University of Chemical Technology, Beijing 100029 (China); Jin Haibo [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Du Chaohai [Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

2013-04-15

394

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

395

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

396

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

397

Adaptive optics enhanced direct laser writing of high refractive index gyroid photonic crystals in chalcogenide glass.  

PubMed

Chiral gyroid photonic crystals are fabricated in the high refractive index chalcogenide glass arsenic trisulfide with an adaptive optics enhanced direct laser writing system. The severe spherical aberration imparted when focusing into the arsenic trisulfide is mitigated with a defocus decoupled aberration compensation technique that reduces the level of aberration that must be compensated by over an order of magnitude. The fabricated gyroids are shown to have excellent uniformity after our adaptive optics method is employed, and the transmission spectra of the gyroids are shown to have good agreement with numerical simulations that are based on a uniform and diffraction limited fabrication resolution. PMID:24515028

Cumming, Benjamin P; Turner, Mark D; Schröder-Turk, Gerd E; Debbarma, Sukanta; Luther-Davies, Barry; Gu, Min

2014-01-13

398

Swift and heavy ion implanted chalcogenide laser glass waveguides and their different refractive index distributions  

SciTech Connect

Planar waveguides have been fabricated in Nd- or Ho-doped gallium lanthanum sulfide laser glasses by 60 MeV Ar or 20 MeV N ion implantation. The refractive index profiles were reconstructed based on the results of prism coupling. The Ar implanted waveguides exhibit an approximate steplike distribution, while the N implanted ones show a ''well + barrier'' type. This difference can be attributed to the much lower dose of Ar ions. After annealing, the N implanted waveguides can support two modes at 1539 nm and have low propagation loss, which makes them candidates for novel waveguide lasers.

Qiu Feng; Narusawa, Tadashi; Zheng Jie

2011-02-10

399

Estimation of the refractive index structure characteristic of air from coherent Doppler wind lidar data.  

PubMed

A technique is proposed for estimating the refractive index structure characteristic of air from data of a coherent Doppler wind lidar. The proposed technique is tested in atmospheric experiments. Time profiles of the structure characteristic in the atmospheric surface layer are obtained and compared with the time profiles of the dissipation rate of the kinetic energy of turbulence obtained from the same lidar data. It is shown in this way that coherent lidars can be used for investigating not only wind turbulence, but also temperature turbulence. PMID:25078167

Banakh, V A; Smalikho, I N; Rahm, S

2014-08-01

400

Simultaneous detection of refractive index and surface charges in nanolaser biosensors  

NASA Astrophysics Data System (ADS)

The emission intensity of a GaInAsP photonic crystal nanolaser is affected by the pH of the solution, in which the nanolaser is immersed. This phenomenon can be explained by the change in the redox potential, which modifies the filling of electrons at surface states of the semiconductor and hence the nonradiative surface recombination. This phenomenon allows the nanolaser to simultaneously and independently detect the refractive index and electric charges near the surface on the basis of the variation in emission wavelength and intensity, respectively. This paper demonstrates this function through alternate deposition of charged polyelectrolytes and hybridization of deoxyribonucleic acids.

Watanabe, Keisuke; Kishi, Yoji; Hachuda, Shoji; Watanabe, Takumi; Sakemoto, Mai; Nishijima, Yoshiaki; Baba, Toshihiko

2015-01-01

401

Swift and heavy ion implanted chalcogenide laser glass waveguides and their different refractive index distributions.  

PubMed

Planar waveguides have been fabricated in Nd- or Ho-doped gallium lanthanum sulfide laser glasses by 60?MeV Ar or 20?MeV N ion implantation. The refractive index profiles were reconstructed based on the results of prism coupling. The Ar implanted waveguides exhibit an approximate steplike distribution, while the N implanted ones show a "well + barrier" type. This difference can be attributed to the much lower dose of Ar ions. After annealing, the N implanted waveguides can support two modes at 1539?nm and have low propagation loss, which makes them candidates for novel waveguide lasers. PMID:21343996

Qiu, Feng; Narusawa, Tadashi; Zheng, Jie

2011-02-10

402

Vacuum energy and the spacetime index of refraction: A new synthesis  

E-print Network

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 one could examine the response of vacuum energy to the presence of a stationary gravitational field in its different quantum field theoretic manifestations such as Casimir effect and Lamb shift. The results are given explicitly for a Casimir apparatus in the weak field limit of a Kerr hole.

M. Nouri-Zonoz

2010-10-06

403

Negative-Index Refraction in a Lamellar Composite with Alternating Single Negative Layers  

E-print Network

Negative-index refraction is achieved in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the famous left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of such an ENG-MNG lamellar composite. In addition, beyond the effective medium approximation, the propagating field squeezed near the ENG/MNG interface is demonstrated to be left-handed surface waves with backward phase velocity.

Z. G. Dong; S. N. Zhu; H. Liu

2005-08-17

404

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

405

Optical characterization of refractive index sensors based on planar waveguide Fabry-Perot Bragg grating cavity  

NASA Astrophysics Data System (ADS)

This study demonstrates the high sensitivity of high Q polymeric planar waveguide refractive index sensors used on the evanescent field. A Fabry-Perot Bragg gratings cavity was fabricated with a cavity size of 5 mm 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 confirmed the FP Bragg gratings cavity is more sensitive than the single Bragg grating. The sensor developed in this study shows much promise in the application of biomedical diagnostics such as a bio-sensor and/or environmental monitoring systems.

Lee, Sang-Mae; Jeong, Wan-Taek; Kim, Kyung-Chun; Kim, Kyung-Jo; Oh, Mincheol; Chung, Thomas; Saini, Simarjeet S.; Dagenais, Mario

2013-05-01

406

Novel bifunctional systems for measuring the refractive index profile and residual stress birefringence in optical fibers and preforms  

Microsoft Academic Search

Two measuring systems are presented enabling determination of the refractive index profile and its anisotropy as well as principal stress components in optical fibers and preforms, respectively. The systems for optical fibers is a scanning-type, differentiating interferometer used to directly measure the wavefront derivative, from which, after the inverse Abel transformation, the index profile is obtained. The required high sensitivity

Waclaw Urbanczyk; Kazimierz Pietraszkiewicz; Wladyslaw A. Wozniak

1992-01-01

407

Exceptionally efficient organic light emitting devices using high refractive index substrates.  

PubMed

Organic light emitting devices (OLEDs) are now used in commercial cell phones and flat screen displays, but may become even more successful in lighting applications, in which large area, high efficiency, long lifetime and low cost are essential. Due to the relatively high refractive index of the organic layers, conventional planar bottom emitting OLEDs have a low outcoupling efficiency. Various approaches for enhancing the optical outcoupling efficiency of bottom emitting OLEDs have been introduced in the literature. In this paper we demonstrate a green bottom emitting OLED with a record external quantum efficiency (42%) and luminous efficacy (183 lm/W). This OLED is based on a high index substrate and a thick electron transport layer (ETL) which uses electrical doping. The efficient light outcoupling is modeled by optical simulations. PMID:19399135

Mladenovski, Saso; Neyts, Kristiaan; Pavicic, Domagoj; Werner, Ansgar; Rothe, Carsten

2009-04-27

408

Nonlinear refractive index measurements and self-action effects in Roselle-Hibiscus Sabdariffa solutions  

NASA Astrophysics Data System (ADS)

We report the observation of self-action phenomena, such as self-focusing, self-defocusing, self-phase modulation and beam fanning in Roselle-Hibiscus Sabdariffa solutions. This material is found to be a new type of natural nonlinear media, and the nonlinear reflective index coefficient has been determined using a Z-scan technique and by measuring the critical power for the self-trapping effect. Z-scan measurements show that this material has a large negative nonlinear refractive index, n 2 = 1 × 10-4 esu. A comparison between the experimental n 2 values and the calculated thermal value for n 2 suggests that the major contribution to nonlinear response is of thermal origin.

Henari, F. Z.; Al-Saie, A.

2006-12-01

409

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 (ca. 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. 2 figs.

Chow, R.; Loomis, G.E.; Thomas, I.M.

1999-03-16

410

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

411

Low-loss multilayered metamaterial exhibiting a negative index of refraction at visible wavelengths  

NASA Astrophysics Data System (ADS)

Over the last decade, metamaterials have attracted a great interest thanks to their potential to expand the range of electromagnetic properties found in natural materials. In particular, the possibility of achieving negative refractive index media (NIM) enables us to implement superlenses and optical storing devices. Since the first experimental demonstration at microwave frequencies, much effort has been put in extending negative refraction to the visible spectrum, where we can take full advantage of NIM properties. For instance, the superior imaging ability of NIM would be essential for visible microscopy. The desired features for NIM are low loss and isotropy. This last property includes polarization independence and negative-index behavior in all spatial directions. None of these features have been attained in previous experiments. Thus, the current challenge is to improve such aspects in order to make NIM suitable for practical applications. In this work, we experimentally demonstrate a low-loss multilayer metamaterial exhibiting a double-negative index in the visible spectrum, while presenting polarization independence at normal incidence. This has been achieved by exploiting the properties of a second-order magnetic resonance of the so-called fishnet structure, in contrast to previous works that used first-order magnetic resonances, both related to gap surface plasmon polariton (SPP) modes. The low-loss nature of the employed magnetic resonance, together with the effect of the interacting adjacent layers, results in a figure of merit as high as 3.34. A wide spectral range of negative index is achieved, covering the wavelength region between 620 and 806 nm with only two different designs. The fabricated metamaterials are the first experimental multilayer NIM in the visible spectrum, which entails an important step towards homogeneous NIM in this range. Finally, we found that the SPP modes determining the permeability resonance display weak angular dispersion.

Garcia-Meca, Carlos

2012-02-01

412

Investigation of the temperature dependent complex index of refraction of infrared thin-film coating materials  

NASA Astrophysics Data System (ADS)

The use of IR optical substrates and thin-films is an integral part of optical system construction for remote sensing instrumentation. From telescopes to multi-spectral imagers, entire optical systems can be built with a relatively small set of materials. The temperature dependence of the optical, mechanical and electronic properties of bulk infrared (IR) materials has been well characterized in the literature [1-5]. Manufacturer and research reports provide some representation of the impact of temperature excursions on the index of refraction (dn/dT), and the absorption profile (dk/dT) of bulk crystalline germanium (Ge) and synthetic crystalline zinc sulphide (ZnS). The availability of empirical data for thin-films, however, is much more limited. These optical constants for as-deposited amorphous thin-films of Ge and ZnS are investigated. Models for the temperature dependent refractive index have been developed using transmittance and reflectance data over the wavelength region between 2.0-20.0 ?m. The spectra of manufactured filters are characterized at ambient and cryogenic temperatures (300K-50K) in order to validate the models developed.

Alves, Lucas C.

2010-08-01

413

High refractive index substrates for fluorescence microscopy of biological interfaces with high z contrast  

PubMed Central

Total internal reflection fluorescence microscopy is widely used to confine the excitation of a complex fluorescent sample very close to the material on which it is supported. By working with high refractive index solid supports, it is possible to confine even further the evanescent field, and by varying the angle of incidence, to obtain quantitative information on the distance of the fluorescent object from the surface. We report the fabrication of hybrid surfaces consisting of nm layers of SiO2 on lithium niobate (LiNbO3, n = 2.3). Supported lipid bilayer membranes can be assembled and patterned on these hybrid surfaces as on conventional glass. By varying the angle of incidence of the excitation light, we are able to obtain fluorescent contrast between 40-nm fluorescent beads tethered to a supported bilayer and fluorescently labeled protein printed on the surface, which differ in vertical position by only tens of nm. Preliminary experiments that test theoretical models for the fluorescence-collection factor near a high refractive index surface are presented, and this factor is incorporated into a semiquantitative model used to predict the contrast of the 40-nm bead/protein system. These results demonstrate that it should be possible to profile the vertical location of fluorophores on the nm distance scale in real time, opening the possibility of many experiments at the interface between supported membranes and living cells. Improvements in materials and optical techniques are outlined. PMID:11717428

Ajo-Franklin, Caroline M.; Kam, Lance; Boxer, Steven G.

2001-01-01

414

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.

415

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

416

Effect of the refraction index in the diameter estimation of thin metallic wires  

NASA Astrophysics Data System (ADS)

The most common technique for diameter measurement of thin metallic cylinders is optical diffractometry. It consists in illuminating the cylinder with a collimated monochromatic light beam, determining the diameter from the location of the minima of the far field diffraction pattern. Babinet principle is normally assumed, being the diffraction pattern of the cylinder equivalent to that of a strip whose width is equal to the cylinder diameter. Due to the three dimensional nature of the cylinder, this model is not valid for accurate measurements. It has been experimentally shown that, when compared to interferometry, Fraunhoffer model presents a systematic overestimation in the cylinder diameter. Rigorous models which assume that the wire presents an infinite conductance have been developed. However, the refraction index of the material has also appeared important for an accurate estimation since it produces a phase shift of the reflected wave by the wire surface, modifying the state of polarization of the incident light beam and, as a consequence, the location of the diffraction minima. In this work we propose a model based on the Geometrical Theory of Diffraction that assumes both the three-dimensional nature and a finite conductance of the wire. Results for several materials are presented, showing that the overestimation of the wire diameter depends on the state of polarization and wavelength of the incident light beam, as well as the diameter and refraction index of the metallic wire.

Sanchez-Brea, Luis Miguel; Martinez-Anton, Juan Carlos; Bernabeu, Eusebio

2005-08-01

417

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

418

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

419

The DRESOR method for radiative heat transfer in a one-dimensional medium with variable refractive index  

NASA Astrophysics Data System (ADS)

This paper extends the DRESOR (Distribution of Ratios of Energy Scattered by the medium Or Reflected by the boundary surface) method to radiative transfer in a variable refractive index medium. In this method, the intensity is obtained from the source term along the curved integration paths determined only by the variable refractive index, and the DRESOR values are calculated by the Monte Carlo method in which the propagation of the energy bundles are affected by Snell's law. With given temperatures on the black boundaries of a one-dimensional medium, the temperature distribution inside the medium with a variable scattering property is calculated under the condition of radiative equilibrium. It is shown that the DRESOR method has a good accuracy in the cases studied. For an isotropic-scattering medium with the same optical thickness, the scattering albedo has no effect on the temperature distribution, which can be obtained from the general equations and can be seen as an extension of what exists for a constant refractive index; however, the different refractive index causes obvious changes in the temperatures inside the medium. The effect of anisotropic scattering on the temperature distribution cannot be ignored, although it is still weaker than the effect caused by variation in the refractive index.

Wang, Zhichao; Cheng, Qiang; Wang, Guihua; Zhou, Huaichun

2011-12-01

420

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

421

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

422

Problem set #13; due Wednesday, April 24, in class. 1. (a) Calculate the x-ray index of refraction and critical angle for total  

E-print Network

Problem set #13; due Wednesday, April 24, in class. 1. (a) Calculate the x-ray index of refraction calculation for the index of refraction with the results of more sophisticated calculations at the LBL web. Scroll down the index and click on "scattering factors". Use the B = 0 result. 3. Calculate

Braun, Paul

423

Refractive-index distributions generating as light rays a given family of curves lying on a surface.  

PubMed

In the framework of geometrical optics, we consider the inverse problem consisting in obtaining refractive-index distributions n=n(u,v) of a two-dimensional transparent inhomogeneous isotropic medium from a known family f(u,v)=c of monochromatic light rays, lying on a given regular surface. Using some basic concepts of differential geometry, we establish a first-order linear partial differential equation relating the assigned family of light rays with all possible refractive-index profiles compatible with this family. In particular, we study the refractive-index distribution producing, as light rays, a given family of geodesic lines on some remarkable surfaces. We give appropriate examples to explain the theory. PMID:21293533

Borghero, Francesco; Kotoulas, Thomas

2011-02-01

424

Negative refractive index of metallic cross-I-shaped pairs: origin and evolution with pair gap width.  

PubMed

A structured composite of the negative index of refraction was fabricated by one layer of cross-I-shaped metal pairs. In this structure, the electric and magnetic inclusions were effectively integrated into one small unit. We varied the spacing of the cross pair to control the location of the magnetic resonance mode and their intercoupling with the electric mode. The frequency dependences of permittivity, permeability, and refractive indices with different gap widths of the pairs were systematically discussed by free-space measurement as well as numerical simulation. A spacing window dependent on the geometrical parameters was found in which the real part of the refractive index could have a negative value. The one-layer cross-pair pattern proposed in this work can be extended to three-dimensional structures with well-controlled interlayer coupling that will greatly facilitate the fabrication and measurement of negative-index materials in high frequencies. PMID:18764072

Ma, Y G; Wang, X C; Ong, C K

2008-07-01

425

Simultaneous measurement of refractive index and wedge angle of optical windows using Fizeau interferometry and a cyclic path optical configuration.  

PubMed

We present a new technique for the simultaneous measurement of refractive index and wedge angle of optical windows using Fizeau interferometry and a cyclic path optical configuration (CPOC). Two laterally separated beams are obtained from an expanded collimated beam using an aperture containing two rectangular openings. The test wedge plate is placed in one of the two separated beams. Using CPOC, these two beams are made to overlap and interfere, producing interference fringes in the overlapping region. The beams reflected from the front and back surfaces of the test wedge plate interfere and produce Fizeau fringes. The refractive index is related to the spacing of the above two beam fringes. The wedge angle is determined from the evaluated values of the refractive index and Fizeau fringe spacing. The results obtained for a BK-7 optical window are presented. PMID:19696865

Kumar, Y Pavan; Chatterjee, Sanjib

2009-08-20

426

Nonlinear intersubband absorption and refractive index change in n-type ?-doped GaAs for different donor distributions  

NASA Astrophysics Data System (ADS)

In this study, both the linear and nonlinear intersubband optical absorption coefficients and the refractive index changes are calculated for the uniform, triangular and Gaussian-like donor distribution. The Gaussian-like distribution differs from the Gaussian distribution other authors use. The electronic structure of n-type Si ?-doped GaAs has been theoretically calculated by solving the Schrödinger and Poisson equations self-consistently. Our results show that the location and the size of the linear and total absorption coefficients and refractive index changes depend on the donor distribution type. The shape of ?-effective potential profile and the subband properties are changed as dependent on the donor distribution model. Therefore, the variation of the absorption coefficients and refraction index changes, which can be appropriate for various optical modulators and infrared optical device applications can be smooth obtained by the alteration donor distribution model.

Ozturk, Emine

2015-01-01

427

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

428

Nonlinearity of refractive index in glasses based on heavy metal oxides with different lead and tellurium contents  

NASA Astrophysics Data System (ADS)

We have studied the nonlinearity of the refractive index at a wavelength of 1.08 µm for optical lead silicate and lead phosphate tellurite glasses of different compositions. We have shown that the nonlinear refractive index n2 increases as the lead content increases in lead silicate glasses and as the tellurium content increases in lead phosphate tellurite glasses, where the latter are typically have higher values of n2, as high as 24·10-13 cgs units (47·10-16 cm2/W), and lower Rayleigh losses. We have established a correlation between the nonlinear refractive index and the microstructure of the studied glasses. The highly nonlinear glasses are distinguished by extensive fluctuations in the heavy metal oxide concentration which are “frozen” during cooling of the glass melt.

Denisov, I. A.; Selivanov, A. G.; Yumashev, K. V.; Anan'ev, A. V.; Maksimov, L. V.; Ovcharenko, N. V.; Bogdanov, V. N.; Lipovskii, A. A.; Vlasova, A. N.

2007-11-01

429

Simultaneous measurement of refractive index and wedge angle of optical windows using Fizeau interferometry and a cyclic path optical configuration  

SciTech Connect

We present a new technique for the simultaneous measurement of refractive index and wedge angle of optical windows using Fizeau interferometry and a cyclic path optical configuration (CPOC). Two laterally separated beams are obtained from an expanded collimated beam using an aperture containing two rectangular openings. The test wedge plate is placed in one of the two separated beams. Using CPOC, these two beams are made to overlap and interfere, producing interference fringes in the overlapping region. The beams reflected from the front and back surfaces of the test wedge plate interfere and produce Fizeau fringes. The refractive index is related to the spacing of the above two beam fringes. The wedge angle is determined from the evaluated values of the refractive index and Fizeau fringe spacing. The results obtained for a BK-7 optical window are presented.

Kumar, Y. Pavan; Chatterjee, Sanjib

2009-08-20

430

Giant refractive-index modulation by two-photon reduction of fluorescent graphene oxides for multimode optical recording.  

PubMed

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

431

Comparison of Densitometry, Refractive Index, and Classical Permanganate Titration Assay Methods with Commercially Available Rocket-Grade Hydrogen Peroxide  

NASA Astrophysics Data System (ADS)

Using classical methods of assay analysis for highly concentrated rocket grade hydrogen peroxide (RGHP, H2O2), comparison and correlation to historical values using currently available commercial-source RGHP is presented. In particular, fluid densities, refractive index, and the potassium permanganate (KMnO4) wet chemical method of analysis are compared. Discussion includes those analytical processes that support field use, with attendant rapid, accurate, and verifiable concentration determinations of RGHP. Method accuracy is ranked as Manual KMnO4 Titration > Refractive Index > Density, based on vendor certifications, with the refractive index method having best precision (+/-0.02%wt H2O2). Results from densitometry data are anomalous, with variability likely due to less mature measurement techniques used in this study.

McPherson, M. D.

2004-10-01

432

Structure variation of the index of refraction of GaAs-AlAs superlattices and multiple quantum wells  

NASA Technical Reports Server (NTRS)

A detailed calculation of the index refraction of various GaAs-AlAs superlattices is presented for the first time. The calculation is performed by using a hybrid approach which combines the k-p method with the pseudopotential technique. Appropriate quantization conditions account for the influence of the superstructures on the electronic properties of the systems. The results of the model are in very good agreement with the experimental data. In comparison with the index of refraction of the corresponding AlGaAs alloy, characterized by the same average mole fraction of Al, the results indicate that the superlattice index of refraction values attain maxima at the various quantized transition energies. For certain structures the difference can be as large as 2 percent. These results suggest that the waveguiding and dispersion relation properties of optoelectronic devices can be tailored to design for specific optical application by an appropriate choice of the superlattice structure parameters.

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

1985-01-01

433

Index of refraction of GaAs-Al(x)Ga(1-x)As superlattices and multiple quantum wells  

NASA Technical Reports Server (NTRS)

A theoretical study of the index of refraction of superlattices and its variation as a function of frequency and the superlattice parameters, i.e., layer width and AlAs composition, is presented. Gamma-region exciton and valence-band mixing effects are included in the model. It is found that these two effects have an important influence on the value of the index of refraction and that superstructure effects rapidly decrease for energies greater than the superlattice potential barriers. Because of the quasi-two-dimensional character of the Gamma-region excitons, the results indicate that the superlattice index of refraction can vary by about two percent at the quantized, bound-exciton, transition energies. Overall, the theoretical results are in good agreement with the experimental data.

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

1987-01-01

434

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

435

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

436

Combined Use of Satellite and Surface Observations to Infer the Imaginary Part of Refractive Index of Saharan Dust  

NASA Technical Reports Server (NTRS)

We present a method for retrieval of the imaginary part of refractive index of desert dust aerosol in the near UV part of spectrum. The method uses Total Ozone Mapping Spectrometer (TOMS) measurements of the top of the atmosphere radiances at 331 and 360 run and aerosol optical depth provided by the Aerosol Robotic Network (AERONET). Obtained values of imaginary part of refractive index retrieved for Saharan dust aerosol at 360 nm are significantly lower than previously reported values. The average retrieved values vary between 0.0054 and 0.0066 for different geographical locations. Our findings are in good agreement with the results of several recent investigations.

Sinyuk, Alexander; Torres, Omar; Dubovik, Oleg; Bhartia, P. K. (Technical Monitor)

2002-01-01

437

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

438

Femtosecond-irradiation-induced refractive-index changes and channel waveguiding in bulk Ti{sup 3+}:Sapphire  

SciTech Connect

We have employed femtosecond laser writing in order to induce refractive-index changes and waveguides in Ti{sup 3+}-doped sapphire. Doping the sapphire crystal with an appropriate ion significantly reduces the threshold for creating structural changes, thus enabling the writing of waveguide structures. Passive and active buried channel waveguiding is demonstrated and images of the guided modes, propagation-loss values, fluorescence spectra, and output efficiencies are presented. The guiding area is located around the laser-damaged region, indicating that the guiding effect is stress induced. Refractive-index changes are measured by digital holography. Proper active doping should enable femtosecond processing and waveguide writing in various crystalline materials.

Apostolopoulos, V.; Laversenne, L.; Colomb, T.; Depeursinge, C.; Salathe, R.P.; Pollnau, M.; Osellame, R.; Cerullo, G.; Laporta, P. [Advanced Photonics Laboratory, Institute for Imaging and Applied Optics, Swiss Federal Institute of Technology, CH-1015 Lausanne (Switzerland); Dipartimento di Fisica, Politecnico di Milano and IFN-CNR, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy)

2004-08-16

439

Direct examination of turbulent refractive-index variations along laser beam propagation paths and corresponding optical-wavefront distortions  

NASA Astrophysics Data System (ADS)

A combined experimental/computational approach is conducted using a specially-designed laboratory facility and a physical framework based on refractive fluid interfaces in order to enable the direct examination of the turbulent refractive-index field along laser beam propagation paths, as well as of the corresponding optical-wavefront distortions of the propagated beam. The experimental facility utilized is the variable-pressure flow facility at UC Irvine which enables direct imaging of the turbulent refractive-index field at large Reynolds numbers in controlled laboratory flows. Laser-induced fluorescence of acetone vapor seeded in air is utilized to directly image the turbulent refractive-index spatial fluctuations along the beam propagation paths. A custom-built high-resolution Shack-Hartmann wavefront sensor is utilized that is useful to measure the optical-wavefront distortions of the propagated optical beam. The flow-imaging measurements, combined with the beam-wavefront data, enable a direct study of the correspondence between the turbulent refractive interfacial-fluid thickness variations and the beam-propagation parameters of interest in free-space laser communications such as the Strehl ratio. Combined with the experiments, computations are also conducted on the flow-imaging data in order to study the structure of the optical beam as it propagates through the measured refractive-index variations. This enables a one-to-one correspondence to be established between the refractive interfacial-fluid thickness variations encountered by the beam and their effect on the distortions of the optical wavefronts, quantified in terms of a cumulative Strehl ratio, along the entire propagation path examined through the flow.

Aguirre, Roberto C.; Nathman, Jennifer C.; Garcia, Philip J.; Catrakis, Haris J.

2005-08-01

440

hal-00115743,version2-15May2007 First measurements of the index of refraction of gases for lithium atomic waves  

E-print Network

of refraction for waves trans- mitted through matter was extended from light waves to neutron waves around 1940hal-00115743,version2-15May2007 First measurements of the index of refraction of gases for lithium of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary

Boyer, Edmond

441

Calibration correction of an active scattering spectrometer probe to account for refractive index of stratospheric aerosols  

NASA Technical Reports Server (NTRS)

The use of the active scattering spectrometer probe (ASAS-X) to measure sulfuric acid aerosols on U-2 and ER-2 research aircraft has yielded results that are at times ambiguous due to the dependence of particles' optical signatures on refractive index as well as physical dimensions. The calibration correction of the ASAS-X optical spectrometer probe for stratospheric aerosol studies is validated through an independent and simultaneous sampling of the particles with impactors; sizing and counting of particles on SEM images yields total particle areas and volumes. Upon correction of calibration in light of these data, spectrometer results averaged over four size distributions are found to agree with similarly averaged impactor results to within a few percent: indicating that the optical properties or chemical composition of the sample aerosol must be known in order to achieve accurate optical aerosol spectrometer size analysis.

Pueschel, R. F.; Overbeck, V. R.; Snetsinger, K. G.; Russell, P. B.; Ferry, G. V.

1990-01-01

442

Hyperspectral optical fiber refractive index measurement spanning 2.5 octaves  

NASA Astrophysics Data System (ADS)

Optical fiber refractive index profiles were measured across a 2.5 octave wavelength range (from 375 nm to 2100 nm) using a single phase-shifting interferometer. This spectral range is more than a factor of 2 larger than previously reported multi-wavelength interferometers, and includes the pump and amplification bands of Er-doped, Yb-doped, Er:Yb-doped, and Tm-doped fibers. The apparatus can measure the material dispersion in a spatially-resolved manner that permits more accurate prediction of the fiber's waveguide properties. The measurement wavelength can be tailored to optimize the beneficial or deleterious effects of material dispersion, optical resolution, and interferometric phase ambiguities.

Yablon, Andrew D.; Jasapara, Jayesh

2013-02-01

443

An effective vacuum refractive index from gravity and the present ether-drift experiments  

E-print Network

Re-analyzing the data published by the Berlin and Duesseldorf ether-drift experiments, we have found a clean non-zero daily average for the amplitude of the signal. The two experimental values, A_0\\sim (10.5 \\pm 1.3) 10^{-16} and A_0\\sim (12.1\\pm 2.2) 10^{-16}$ respectively, are entirely consistent with the theoretical prediction (9.7\\pm 3.5) 10^{-16} that is obtained once the Robertson-Mansouri-Sexl anisotropy parameter is expressed in terms of N_{vacuum}, the effective vacuum refractive index that one would get, for an apparatus placed on the Earth's surface, in a flat-space picture of gravity .

M. Consoli; E. Costanzo

2006-04-04

444

Modified Roberts-Langenbeck test for measuring thickness and refractive index variation of silicon wafers.  

PubMed

We describe a method to simultaneously measure thickness variation and refractive index homogeneity of 300 mm diameter silicon wafers using a wavelength-shifting Fizeau interferometer operating at 1550 nm. Only three measurements are required, corresponding to three different cavity configurations. A customized phase shifting algorithm is used to suppress several high order harmonics and minimize intensity sampling errors. The new method was tested with both silicon and fused silica wafers and measurement results proved to be highly repeatable. The reliability of the method was further verified by comparing the measured thickness variation of a 150 mm diameter wafer to a measurement of the wafer flatness after bonding the wafer to an optical flat. PMID:23037060

Park, Jungjae; Chen, Lingfeng; Wang, Quandou; Griesmann, Ulf

2012-08-27

445

Highly emissive and low refractive index layers from doped silica nanospheres for solar cell applications  

NASA Astrophysics Data System (ADS)

Confinement of europium (Eu 3+) ions in silica (SiO 2) nanospheres yields efficient red-emitting nanophosphors when excited via charge transfer states (CTS) absorption in UV (393 nm) radiation. This is explained on the basis of modulation of f-f transition due to quantum confinement of rare-earth ion in a nanosize host. It is also evidenced that the short range crystallanity and confinement effects provided by the nanospheres increases the Eu 3+ emission intensity by almost ten times at the expense of CTS. Coating of organically modified SiO 2 nanospheres resulted in low refractive index layers that are highly useful as cover glazing for solar collectors.

Haranath, D.; Gandhi, Namita; Sahai, Sonal; Husain, M.; Shanker, Virendra

2010-08-01

446

Re-definition of effective refractive index of thin film buried quantum dots  

NASA Astrophysics Data System (ADS)

In this article, we predicted the optical properties of the thin film including quantum dots according to the mathematic mode which is based on the quantum theory. The method consists of two parts. The first one is the classical explanation for the interaction between light and matters. It takes care of the interaction as dipoles and electromagnetic wave and describes clearly the profile of spectrum. Another part is the transition of quantized energy, absorption and spontaneous emission which exhibits singular valleys or peaks in spectrum. For the reason of quantum theory, we have to verify Bohr radius of each crystallized material to make sure that the particle size is small enough to present quantum effect. After constructing the spectrum, the data significantly presents optical properties of matters, we try to re-define the effective refractive index of the thin film including quantum dots by the spectrum which is the result of light affected by matters.

Chen, Yu-Jen; Lee Schmidt, Cheng-Chung; Flory, François

2011-09-01

447

Determination of thickness, refractive index, and spectral scattering of an inhomogeneous thin film with rough interfaces  

SciTech Connect

The magnitude of spectral transmittance and reflectance is affected by the presence of inhomogeneity and interfacial roughness. Therefore, the methods, based on the magnitude of spectral transmittance and reflectance, are not adequate for the determination of thickness and optical constants of films with inhomogeneity and interfacial roughness. The present article proposes a method for the determination of thickness and refractive index using only the positions of the interference fringes in spectral transmittance and reflectance at two different angles of incidence. The proposed method is verified through numerical simulations, which result in <1% error for the film thickness. The complete parametrical dependence of spectral transmittance and reflectance of inhomogeneous film with rough interfaces on a substrate have been worked out for the film on transparent and opaque substrates, respectively. The spectrum envelopes have been solved simultaneously and the mathematical formulae are given for the determination of spectral scattering due to inhomogeneity and interfacial roughness for both transmittance and reflectance cases.

Pradeep, J. Anto; Agarwal, Pratima [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781 039 (India)

2010-08-15

448

Dispersion of the refractive index of a neutron in a crystal  

NASA Astrophysics Data System (ADS)

The dispersion (resonance) behavior of the refractive index of a neutron moving in a crystal with energies close to Bragg values has been studied. It has been shown that a small change in the energy of the neutron by about the Bragg width in this case (? E/ E ˜ 10-5) results in a significant (several tens of percent) change in the potential of the interaction of the neutron with the crystal. A new phenomenon—the acceleration of the neutron passing through a perfect crystal moving at a variable velocity near a Bragg resonance—has been observed. The effect appears because the parameter of deviation from the Bragg condition and, therefore, the neutron-crystal interaction potential change during the time of flight of the neuron through the accelerated crystal. As a result, the kinetic energy of the neutron leaving the crystal changes.

Voronin, V. V.; Berdnikov, Ya. A.; Berdnikov, A. Ya.; Braginetz, Yu. P.; Vezhlev, E. O.; Kuznetsov, I. A.; Lasitsa, M. V.; Semenikhin, S. Yu.; Fedorov, V. V.

2014-12-01

449

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

450

Using a plasma physics experiment to expand student understanding of the index of refraction  

NASA Astrophysics Data System (ADS)

The Los Angeles Physics Alliance Group (LAPTAG) Plasma Lab has met regularly at UCLA for the past 9 years. High school students have been involved in the construction of probes, amplifiers, antennae, machine shop use, printed circuit construction, experimental design, and scientific programming for the analysis of data. We describe a unique opportunity for high school students to participate in the process of science. Using plasma physics as an educational ``hook,'' students are engaged through a series of experiments, lectures, presentations, and group discussions. The outcome is that students gain a deeper understanding of the scientific method and in this case, the concepts of index of refraction and its effects on wave propagation. For example, students comprehend such advanced topics as dispersion, k-space, plasma properties, and wave group and phase velocities. This engagement supports efforts to improve STEM career choices by exposing high school students to challenging and interesting experiences in preparation for advanced study. )

Wise, Joe; Gekelman, Walter; Baker, Robert; Pribyl, Patrick

2010-02-01

451

Measurement of organic chemical refractive indexes using an optical time-domain reflectometer.  

PubMed

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

452

Digital holographic microtomography for high-resolution refractive index mapping of live cells.  

PubMed

Quantification of three-dimensional (3D) refractive index (RI) with sub-cellular resolution is achieved by digital holographic microtomography (DH?T) using quantitative phase images measured at multiple illumination angles. The DH?T system achieves sensitive and fast phase measurements based on iterative phase extraction algorithm and asynchronous phase shifting interferometry without any phase monitoring or active control mechanism. A reconstruction algorithm, optical diffraction tomography with projection on convex sets and total variation minimization, is implemented to substantially reduce the number of angular scattered fields needed for reconstruction without sacrificing the accuracy and quality of the reconstructed 3D RI distribution. Tomogram of a living CA9-22 cell is presented to demonstrate the performance of the method. Further, a statistical analysis of the average RI of the nucleoli, the nucleus excluding the nucleoli and the cytoplasm of twenty CA9-22 cells is performed. PMID:22927364

Su, Jing-Wei; Hsu, Wei-Chen; Chou, Cheng-Ying; Chang, Chen-Hao; Sung, Kung-Bin

2013-05-01

453

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

454

Casimir effect in a weak gravitational field and the spacetime index of refraction  

E-print Network

In a recent paper [arXiv:0904.2904] using a conjecture it is shown how one can calculate the effect of a weak stationary gravitational field on vacuum energy in the context of Casimir effect in an external gravitational field treated in 1+3 formulation of spacetime decomposition.. In this article, employing quntum 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. This could be taken as a strong evidence in favour of the proposed conjecture. Generalizations to weak {\\it stationary} spacetimes and virtual photons are also discussed.

B. Nazari; M. Nouri-Zonoz

2010-10-07

455

Tailoring the index of refraction of nanocrystalline hafnium oxide thin films  

SciTech Connect

Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s}?=?25–700?°C). HfO{sub 2} films grown at T{sub s}?index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (?)}?=?550?nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-?-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and the microstructure of HfO{sub 2} films.

Vargas, Mirella [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)] [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States); Murphy, N. R. [Materials and Manufacturing Directorate (RX), 3005 Hobson Way, Wright-Patterson Air Force Base (WPAFB), Dayton, Ohio 45433 (United States)] [Materials and Manufacturing Directorate (RX), 3005 Hobson Way, Wright-Patterson Air Force Base (WPAFB), Dayton, Ohio 45433 (United States); Ramana, C. V., E-mail: rvchintalapalle@utep.edu [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)

2014-03-10

456

Metamaterial lens made of fully printed resonant-type negative-refractive-index transmission lines  

NASA Astrophysics Data System (ADS)

We studied a well-resolved lens based on planar fully printed resonant-type negative-refractive-index transmission lines made of complementary split ring resonators. The lens goes beyond previous lens in terms of moderate loss and compactness. The focusing has been demonstrated by the circuit theory simulation and full-wave simulation and finally confirmed by the experiments, showing that that the lens is able to overcome the diffraction limit of 0.5 effective wavelengths and exhibits a super resolution as small as 0.348 effective wavelengths inside the lens. The superlens free of any lumped elements opens an easy and inexpensive avenue toward imaging devices with super performances.

Xu, He-Xiu; Wang, Guang-Ming; Qing Qi, Mei; Lv, Yuan-Yuan; Gao, Xi

2013-05-01

457

In situ index-of-refraction measurements of the South Polar firn with the RICE detector  

NASA Astrophysics Data System (ADS)

Using the RICE (Radio Ice Cherenkov Experiment) detector at the South Pole, we have estimated the variation in the index of refraction (n) of the firn, as a function of elevation (z) measured from the surface down to z = -150 m. Measurements were made by lowering a dipole transmitter into a dry (5 in (127 mm) caliber) borehole, originally drilled for the RICE experiment in 1998, and determining signal arrival times, as a function of transmitter depth, in the englacial RICE receiver array. We clearly confirm the expected correlation of n(z) with ice density. Our measurements are in fair agreement with previous laboratory characterizations of the dielectric properties of ice cores. These are the first such in situ measurements to be performed at the South Pole.

Kravchenko, Ilya; Besson, David; Meyers, Josh

458

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

459

Refractive index sensing for online monitoring water and ethanol content in bio fuels  

NASA Astrophysics Data System (ADS)

We report on a refractive index sensor based on a planar Bragg grating (PBG) capable to online monitor the water content in Biodiesel and the amount of ethanol admixture to conventional fuels, respectively. Our results demonstrate the capability of the sensor to distinguish the transition between about 190 and 500 ppm water in Biodiesel, enabling to monitor the production process of Biodiesel in the relevant range according to industrial standards. The ethanol content in petrol has been investigated in the range of 0-100%, covering the entire standardized range of E-5 to E-85 fuel mixing ratios. These experiments reveal a sensitivity of 112 nm/riu allowing the measurement of the ethanol content with a resolution of 8.9·10-6.

Belle, S.; Scheurich, S.; Hellmann, R.; So, S.; Sparrow, I. J. G.; Emmerson, G. D.

2010-04-01

460

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

461

Potentiation of Femtosecond Laser Intratissue Refractive Index Shaping (IRIS) in the Living Cornea with Sodium Fluorescein  

PubMed Central

Purpose. To assess the effectiveness of intratissue refractive index shaping (IRIS) in living corneas and test the hypothesis that it can be enhanced by increasing the two-photon absorption (TPA) of the tissue. Methods. Three corneas were removed from adult cats and cut into six pieces, which were placed in preservative (Optisol-GS; Bausch & Lomb, Inc., Irvine, CA) containing 0%, 0.25%, 1%, 1.5%, or 2.5% sodium fluorescein (Na-Fl). An 800-nm Ti:Sapphire femtosecond laser with a 100-fs pulse duration and 80-MHz repetition rate was used to perform IRIS in each piece, creating several refractive index (RI) modification lines at different speeds (between 0.1 and 5 mm/s). The lines were 1 ?m wide, 10 ?m apart, and ?150 ?m below the tissue surface. The RI change of each grating was measured using calibrated, differential interference contrast microscopy. TUNEL staining was performed to assess whether IRIS or Na-Fl doping causes cell death. Results. Scanning at 0.1 mm/s changed the RI of undoped, living corneas by 0.005. In doped corneas, RI changes between 0.01 and 0.02 were reliably achieved with higher scanning speeds. The magnitude of RI changes attained was directly proportional to Na-Fl doping concentration and inversely proportional to the scanning speed used to create the gratings. Conclusions. IRIS can be efficiently performed in living corneal tissue. Increasing the TPA of the tissue with Na-Fl increased both the scanning speeds and the magnitude of RI changes in a dose-dependent manner. Ongoing studies are exploring the use of IRIS to alter the optical properties of corneal tissue in situ, over an extended period. PMID:19815735

Nagy, Lana J.; Ding, Li; Xu, Lisen; Knox, Wayne H.

2010-01-01

462

Analyzing the effect of absorption and refractive index on image formation in high numerical aperture transmission microscopy of single cells  

NASA Astrophysics Data System (ADS)

Transmission bright-field microscopy is the clinical mainstay for disease diagnosis where image contrast is provided by absorptive and refractive index differences between tissue and the surrounding media. Different microscopy techniques often assume one of the two contrast mechanisms is negligible as a means to better understand the tissue scattering processes. This particular work provides better understanding of the role of refractive index and absorption within Optical Projection Tomographic Microscopy (OPTM) through the development of a generalized computational model based upon the Finite-Difference Time-Domain method. The model mimics OPTM by simulating axial scanning of the objective focal plane through the cell to produce projection images. These projection images, acquired from circumferential positions around the cell, are reconstructed into isometric three-dimensional images using the filtered backprojection normally employed in Computed Tomography (CT). The model provides a platform to analyze all aspects of bright-field microscopes, such as the degree of refractive index matching and the numerical aperture, which can be varied from air-immersion to high NA oil-immersion. In this preliminary work, the model is used to understand the effects of absorption and refraction on image formation using micro-shells and idealized nuclei. Analysis of absorption and refractive index separately provides the opportunity to better assess their role together as a complex refractive index for improved interpretation of bright-field scattering, essential for OPTM image reconstruction. This simulation, as well as ones in the future looking at other effects, will be used to optimize OPTM imaging parameters and triage efforts to further improve the overall system design.

Coe, Ryan L.; Seibel, Eric J.

2013-02-01

463

An investigation of matched index of refraction technique and its application in optical measurements of fluid flow  

NASA Astrophysics Data System (ADS)

Optical distortions caused by non-uniformities of the refractive index within the measurement volume is a major impediment for all laser diagnostic imaging techniques applied in experimental fluid dynamic studies. Matching the refractive indices of the working fluid and the test section walls and interfaces provides an effective solution to this problem. The experimental set-ups designed to be used along with laser imaging techniques are typically constructed of transparent solid materials. In this investigation, different types of aqueous salt solutions and various organic fluids are studied for refractive index matching with acrylic and fused quartz, which are commonly used in construction of the test sections. One aqueous CaCl2·2H2O solution (63 % by weight) and two organic fluids, Dibutyl Phthalate and P-Cymene, are suggested for refractive index matching with fused quartz and acrylic, respectively. Moreover, the temperature dependence of the refractive indices of these fluids is investigated, and the Thermooptic Constant is calculated for each fluid. Finally, the fluid viscosity for different shear rates is measured as a function of temperature and is applied to characterize the physical behavior of the proposed fluids.

Amini, Noushin; Hassan, Yassin A.

2012-12-01