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1

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

2

Temperature-dependent absolute refractive index measurements of synthetic fused silica  

NASA Astrophysics Data System (ADS)

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 +/-1 ×10-5. Statistical variations in derived values of the thermo-optic coefficient (dn/dT) are at the +/-2 × 10-8/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.

2006-07-01

3

Temperature-dependent Absolute Refractive Index Measurements of Synthetic Fused Silica  

NASA Technical Reports Server (NTRS)

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

Leviton, Douglas B.; Frey, Bradley J.

2006-01-01

4

Absolute index of refraction and its temperature dependence of calcium fluoride, barium fluoride, and strontium fluoride near 157 nm  

NASA Astrophysics Data System (ADS)

We have made accurate measurements near 157 nm of the absolute index of refraction, the index of refraction, the index dispersion, and the temperature dependence of the index, for the cubic-symmetry, group-II fluorides: calcium fluoride, strontium fluoride, and barium fluoride. Accurate measurements of these quantities for calcium fluoride are needed for designs of lens systems for 157 nm excimer-laser- based exposure tools for photolithography. Measurements of these isotropic materials high ly transmissive near 157 nm, such as strontium fluoride and barium fluoride, are needed for designs which include secondary materials in addition to calcium fluoride to correct for chromatic aberrations. These optical properties were measured with precision gonimeters on prisms of the materials in a nitrogen atmosphere using the minimum deviation method. The relative refractive indices were converted to absolute indices by using values of the index of nitrogen obtained by independent interferometric measurement near 157 nm. Values of the absolute refractive indices for these materials were obtained with an accuracy of 6 X 10-6. A key result is that the dispersion of barium fluoride near 157 nm is approximately 68 percent larger than that of calcium fluoride, which makes barium fluoride a potentially useful material for combination with calcium fluoride for chromatic aberration correction near 157 nm.

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

2000-07-01

5

The Index of Refraction  

NSDL National Science Digital Library

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

Foundation, Wgbh E.

2011-10-25

6

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

Gradient Refractive Index Lenses.  

ERIC Educational Resources Information Center

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

Morton, N.

1984-01-01

9

Neutrino currents in the absolute spacetime: Relating the refractive index of the aether to the OPERA excess velocity  

NASA Astrophysics Data System (ADS)

The superluminal neutrino velocity measured by the OPERA experiment is explained in a non-relativistic spacetime conception. Spacetime is viewed as a permeable medium of wave propagation. The neutrino wave equation is coupled to a permeability tensor, like electromagnetic fields in dielectric media. The inertial frame in which this tensor is isotropic defines a distinguished frame of reference, the rest frame of the aether. The dispersion relation of the spinorial wave modes gives rise to a superluminal group velocity of the energy flux. The Gordon decomposition of spinor currents in a refractive and dispersive spacetime is performed with finite as well as zero rest mass. The convective and spin components of the superluminal neutrino current are related to the permeability tensor. The refractive index of the aether depends on the neutrino energy, and is inferred in the 10 to 50 GeV range from the measured excess velocity. Implications of the superluminal speed of signal transfer regarding relativity principles and causality are discussed.

Tomaschitz, R.

2012-02-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

11

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

12

Refractive Index of Sodium Iodide  

Microsoft Academic Search

The refractive index of sodium iodide, an important scintillator material that is widely used for radiation detection, is based on a single measurement made by Spangenberg at one wavelength using the index-matching liquid immersion method (Z. Kristallogr., 57, 494-534 (1923)). In the present paper, we present new results for the refractive index of sodium iodide as measured by the minimum

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

2012-01-01

13

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) [Albuquerque, NM

2002-01-01

14

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

15

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

16

Make That Invisible! Refractive Index Matching  

NSDL National Science Digital Library

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

University Of Houston

17

Optical Fiber Sensor for Measuring Refractive Index  

Microsoft Academic Search

An optical fiber sensor for measuring a liquid refractive index is proposed. When an optical fiber is bent and part of its cladding is stripped off, the light energy (E) emerging from the fiber depends on the refractive index of the surrounding medium (nm). The change in nm can be found from E. The light output energy and the measuring

Takashi Takeo; Hajime Hattori

1982-01-01

18

Negative index of refraction in optical metamaterials  

Microsoft Academic Search

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

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

2005-01-01

19

Group Contribution to Molar Refraction and Refractive Index of Conjugated Polymers.  

National Technical Information Service (NTIS)

The functional group contribution to molar refraction and refractive index of pi-conjugated polymers has been evaluated from the available refractive index dispersion data for 33 conjugated polymers. The Lorentz-Lorenz molar refraction (Ru) of 24 function...

C. J. Yang S. A. Jenekhe

1996-01-01

20

Refractive index of plant cell walls  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

21

Refractive index, molar refraction and comparative refractive index study of propylene carbonate binary liquid mixtures.  

PubMed

Refractive indices (n) have been experimentally determined for the binary liquid-liquid mixtures of Propylene carbonate (PC) (1) with benzene, ethylbenzene, o-xylene and p-xylene (2) at 298.15, 303.15 and 308.15 K over the entire mole fraction range. The experimental values of n are utilised to calculate deviation in refractive index (?n), molar refraction (R) and deviation in molar refraction (?R). A comparative study of Arago-Biot (A-B), Newton (NW), Eyring and John (E-J) equations for determining refractive index of a liquid has been carried out to test their validity for all the binary mixtures over the entire composition range at 298.15 K. Comparison of various mixing relations is represented in terms of average deviation (AVD). The ?n and ?R values have been fitted to Redlich-Kister equation at 298.15 K and standard deviations have been calculated. The results are discussed in terms of intermolecular interactions present amongst the components. PMID:24061238

Wankhede, Dnyaneshwar Shamrao

2012-06-01

22

Approximations to the plasma refractive index  

NASA Astrophysics Data System (ADS)

For fifty years the quasi-longitudinal and quasi-transverse approximations to the refractive index formula for an ionized plasma have been used. Recent investigations have sought to generalize the traditional treatment in various ways. In the author's opinion, something further remains to be explained, and in the present paper various algebraic identities are examined between distinct forms of the refractive index, whereby a radical can sometimes be switched between numerator and denominator. Approximations to this radical are kept distinct algebraically from any subsequent expansions that may be made in the refractive index formula. The properties of this radical and its various approximations are examined in detail, both algebraically and numerically.

Heading, J.

1984-12-01

23

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

24

Refractive Index Dispersion in Ternary Germanate Glasses  

NASA Astrophysics Data System (ADS)

The refractive index dispersion in germanate oxyfluoride glasses of GeO2-P2O5-MF2 (M=Ca, Zn), which are developed for optical fiber application, is investigated in the 0.4-4 µ m wavelength range by the minimum deviation method. The prepared glasses have a GeO2 content varying from 80 to 30 mol%. The dispersion curves for these glasses tend to shift to shorter wavelengths as the GeO2 content is decreased. Material dispersions are also derived from the refractive index measurements and the zero-material dispersion wavelengths (?0) are found in the vicinity of 1.5 µ m. On the basis of the empirical relationship between ?0 and the minimum loss wavelength (?0), the ? min values are located at around 1.8 µ m. A minimum loss of as low as 0.08 dB/km is expected for the present germanate glasses.

Sakaguchi, Shigeki; Todoroki, Shinichi; Rigout, Nathalie

1995-10-01

25

Matched Index of Refraction Flow Facility  

ScienceCinema

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

Mcllroy, Hugh

2013-05-28

26

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

27

Tissue refractive index as marker of disease  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

28

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

29

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.

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

30

Cosmology with a dark refraction index  

NASA Astrophysics Data System (ADS)

In this dissertation we review Gordon's optical metric theory, generalize it, and apply it to modern cosmology. In Chapter 1, we build the notation, define important quantities (luminosity distance, angular diameter distance, etc.), derive a few key equations (reciprocity relation, transport equations of optical scalars, etc.), and develop some basic techniques which will be useful later on. In Chapter 2 we apply Gordon's optical metric theory to Friedman-Lemaître- Robertson-Walker cosmologies. We associate a refraction index with the cosmic fluid and derive the refraction-corrected distance redshift relations. We then 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. In Chapter 3 we show that Gordon's optical metric on a curved spacetime can be generalized to include absorption by allowing the metric to become complex. We distinguish two different cases, i.e., strong and weak absorption, and demonstrate the use of the complex optical metric theory by giving three examples. We use one of these examples to compute corrected distance-redshift relations for Friedman-Lemaître-Robertson-Walker models in which the cosmic fluid possesses a complex index of refraction that represents grey extinction. We then fit this corrected Hubble curve to the same supernovae data used in Chapter 2 by assuming pure absorption. In Chapter 4 we equate the physical intensity reduction of a light wave caused by weak absorption with a geometrical reduction in intensity caused by a "transverse" conformal transformation of the spacetime metric in which the wave travels. We then modify Gordon's optical metric to include absorption via a totally different way than that of Chapter 3 in which we included absorption in Gordon's optical metric by allowing the metric to be complex. We derive the distance-redshift relation from the modified optical metric for Friedman- Lemaître-Robertson-Walker spacetimes whose cosmic fluid has associated refraction and absorption coefficients. We then fit the current supernovae data with a cosmological model containing both refraction and absorption and provide an alternate explanation (other than dark energy) of the apparent acceleration of the universe expansion.

Chen, Bin

2009-09-01

31

Prediction of Refractive Index of Quaternary Liquid Mixtures  

Microsoft Academic Search

Refractive index data for three quaternary liquid mixtures have been analysed after extending the mixing rules for index of refraction available in literature. Relative merits and interrelations of various important mixing rules for these quaternary liquid mixtures have been discussed in detail. Surprisingly the extended equations yield fairly good agreement between theoretical and experimental values of refractive indices.

J. D. Pandey; A. K. Shukla; R. K. Shukla; R. D. Rai

1988-01-01

32

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

33

Refractive index of liquid mixtures: theory and experiment.  

PubMed

An innovative approach is presented to interpret the refractive index of binary liquid mixtures. The concept of refractive index "before mixing" is introduced and shown to be given by the volume-fraction mixing rule of the pure-component refractive indices (Arago-Biot formula). The refractive index of thermodynamically ideal liquid mixtures is demonstrated to be given by the volume-fraction mixing rule of the pure-component squared refractive indices (Newton formula). This theoretical formulation entails a positive change of refractive index upon ideal mixing, which is interpreted in terms of dissimilar London dispersion forces centred in the dissimilar molecules making up the mixture. For real liquid mixtures, the refractive index of mixing and the excess refractive index are introduced in a thermodynamic manner. Examples of mixtures are cited for which excess refractive indices and excess molar volumes show all of the four possible sign combinations, a fact that jeopardises the finding of a general equation linking these two excess properties. Refractive indices of 69 mixtures of water with the amphiphile (R,S)-1-propoxypropan-2-ol are reported at five temperatures in the range 283-303 K. The ideal and real refractive properties of this binary system are discussed. Pear-shaped plots of excess refractive indices against excess molar volumes show that extreme positive values of excess refractive index occur at a substantially lower mole fraction of the amphiphile than extreme negative values of excess molar volume. Analysis of these plots provides insights into the mixing schemes that occur in different composition segments. A nearly linear variation is found when Balankina's ratios between excess and ideal values of refractive indices are plotted against ratios between excess and ideal values of molar volumes. It is concluded that, when coupled with volumetric properties, the new thermodynamic functions defined for the analysis of refractive indices of liquid mixtures give important complementary information on the mixing process over the whole composition range. PMID:20957714

Reis, João Carlos R; Lampreia, Isabel M S; Santos, Angela F S; Moita, Maria Luísa C J; Douhéret, Gérard

2010-12-01

34

Epifilm thickness measurements using Fourier transform infrared spectroscopy: Effect of refractive index dispersion and refractive index measurement  

NASA Astrophysics Data System (ADS)

Procedures and results of refractive index measurements using a Fourier transform infrared spectrometer are reported. These measurements were performed on both lightly and heavily doped silicon samples over the midinfrared (2.5-25 micrometers) spectrum region. A strong dependence of refractive index as a function of substrate dopant concentration was observed. Moreover, it was observed that the refractive index of heavily doped silicon also varies significantly with wavelength. Furthermore, it was also observed that the refractive index of silicon decreases with increasing wafer temperature for long wavelengths. Finally, the effect of refractive index dispersion on epifilm thickness measurement was examined. The results suggest that the spectral dispersion of the refractive index cannot be neglected for epifilm thickness measurements.

Zhou, Zhen-Hong; Choi, Byungin; Flik, M. I.; Fan, S.; Reif, Rafael

1994-08-01

35

Index of Refraction and SnellâÂÂs Law  

NSDL National Science Digital Library

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

2012-05-30

36

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

37

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

Microsoft Academic Search

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

Matteo Galli; Franco Marabelli; Giorgio Guizzetti

2003-01-01

38

Recent developments in microstructured fiber Bragg grating refractive index sensors  

NASA Astrophysics Data System (ADS)

Refractive index measurement by optical fiber sensors has proved to be effective in the research of biochemical and biomedical applications. The theoretical principles and technology underlying several microstructured fiber Bragg grating refractive index sensors developed over the past decade are classified and briefly summarized, and their future developments are considered.

Luo, Bin-Bin; Zhou, Xiao-jun; Zhao, Ming-fu; Zhong, Nianbing; Wang, Sao-fei

2010-01-01

39

Measurement of Refractive Index Using a Michelson Interferometer.  

ERIC Educational Resources Information Center

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

Fendley, J. J.

1982-01-01

40

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.

41

Quantum Radiation from Superluminal Refractive-Index Perturbations  

SciTech Connect

We analyze in detail photon production induced by a superluminal refractive-index perturbation in realistic experimental operating conditions. The interaction between the refractive-index perturbation and the quantum vacuum fluctuations of the electromagnetic field leads to the production of photon pairs.

Belgiorno, F. [Dipartimento di Matematica, Universita di Milano, Via Saldini 50, IT-20133 Milano (Italy); Cacciatori, S. L.; Sala, V. G. [INFN and Department of Physics and Mathematics, Universita dell'Insubria, Via Valleggio 11, IT-22100 Como (Italy); Ortenzi, G. [Dipartimento di Matematica ed Applicazioni, Universita degli Studi di Milano Bicocca, via Cozzi 53, IT-20125 Milano (Italy); Faccio, D. [CNISM and Department of Physics and Mathematics, Universita dell'Insubria, Via Valleggio 11, IT-22100 Como (Italy)

2010-04-09

42

Quantum radiation from superluminal refractive-index perturbations.  

PubMed

We analyze in detail photon production induced by a superluminal refractive-index perturbation in realistic experimental operating conditions. The interaction between the refractive-index perturbation and the quantum vacuum fluctuations of the electromagnetic field leads to the production of photon pairs. PMID:20481923

Belgiorno, F; Cacciatori, S L; Ortenzi, G; Sala, V G; Faccio, D

2010-04-01

43

NOVEL BROADBAND TERAHERTZ NEGATIVE REFRACTIVE INDEX METAMATERIALS: ANALYSIS AND EXPERIMENT  

Microsoft Academic Search

Broadband planar and non-planar negative refractive index (NRI) metamaterial (MTM) designs consisting of a periodically arranged split ring resonator and wire structures are developed in the terahertz (THz) frequency regime using the Finite-Difference Time- Domain (FDTD) method. The novel MTM designs generate a broad negative index of refraction (NIR) passband approximately two and a half times higher than those of

Nantakan Wongkasem; A. Akyurtlu; Jin Li; Adam Tibolt; Zeng Kang; William D. Goodhue

2006-01-01

44

Refractive index matching using a diethyl phthalate/ ethanol solution  

NASA Astrophysics Data System (ADS)

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

Miller, Paul; Slifka, Andy; Moody, Galan

2005-11-01

45

Measuring refractive index using the focal displacement method.  

PubMed

A simple technique is introduced for measuring the refractive index of plane-parallel samples having thickness of the order of a millimeter. The refractive index values are reported for six bulk semiconductors, each index measured at two infrared wavelengths using this method. The values are found to be within a few percent of those in literature for four semiconductors. The other two semiconductors were newly grown ternary alloys (CdMgTe and CdMnTe), for which the refractive index values have not been reported previously at the wavelengths studied here. PMID:24921140

Murray, Joel M; Wei, Jean; Barnes, Jacob O; Slagle, Jonathan E; Guha, Shekhar

2014-06-10

46

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

47

Corneal group refractive index measurement using low-coherence interferometry  

NASA Astrophysics Data System (ADS)

Purpose: The goal of the study is to measure the group refractive index of the human cornea in vitro to improve the accuracy of corneal thickness measurements. Methods: Corneal buttons were trephined from 23 human cadaver eyes and the group refractive index of the cornea was measured at lambda equals 840 nm using a low-coherence Michelson interferometer and the technique proposed by Sorin and Gray (Phot. Tech. Lett. 4:105 - 107, 1992). The effect of dehydration on the measurement was studied by measuring the corneal optical thickness as a function of time. Results: Preliminary measurements of the group refractive index at 840 nm gave ng equals 1.450 plus or minus 0.024 for the human cornea, which is much higher than a calculated group refractive index of ng equals 1.387. Because of dehydration, the optical thickness of the cornea decreased at a rate of 5.5 micrometer/minute which led to an artificially high value for the group refractive index. Conclusion: The calculated group refractive index of ng equals 1.387 appears to be an accurate value for the purpose of corneal thickness measurements using low-coherence interferometry, and corneal group refractive index measurements can be performed in vitro if the measurements are performed rapidly to avoid the effect of dehydration.

Uhlhorn, Stephen R.; Manns, Fabrice; Tahi, Hassan; Rol, Pascal O.; Parel, Jean-Marie A.

1998-06-01

48

Measurement of gradient refractive index profile using a birefringent lens  

NASA Astrophysics Data System (ADS)

The shape, depth, and maximum change in refractive index profile are of the most important parameters to be controlled when developing gradient refractive index (GRIN) lens blanks. Generally refractive index profiles are measured by standard interferometers such as Mach- Zehnder, Twyman, and Shearing interferometers. These methods generate a large amount of data and need rigorous computation. A new kind of deflectometry is reported that can measure a GRIN profile using the interference pattern generated by a birefringent lens. Results based on this method are presented for radial GRIN glasses developed by Ag+- Na+ and Na+-Li+ ion exchange in alkali aluminosilicate glasses.

Biswas, Nisha S.; Sarkar, Samir K.; Basuray, Amitabha

1996-02-01

49

Temperature dependence of the infrared refractive index of sapphire  

NASA Astrophysics Data System (ADS)

Infrared domes on guided missiles are aerodynamically heated nonuniformly. Because the index of refraction is temperature dependent, the temperature gradient can cause image blur and bore-sight error. The temperature dependence of the infrared refractive index has not been directly measured in sapphire, a popular dome material. However, an accurate model of the temperature-dependent infrared refractive index can be obtained from visible measurements of the refractive index, far-infrared reflectance measurements, and infrared measurements of the absorption coefficient. Visible measurements determine the contribution to the refractive index from electronic transitions. Far-infrared measurements determine the contributions from fundamental lattice vibrations (phonons). Infrared absorption data are used to determine parameters in a multiphonon sum band model. By applying the Hilbert transform to this multiphonon absorption model, a model for the multiphonon refractivity is obtained. Two- and three-phonon contributions to the refractive index are important for an accurate model that includes temperature dependence. Results for the ordinary ray and extraordinary ray are obtained.

Thomas, Michael E.; Sova, Raymond M.; Joseph, Richard I.

1994-09-01

50

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

51

Engineering a resonant nanocoating for an optical refractive index sensor  

NASA Astrophysics Data System (ADS)

We proposing to boost the performance of refractive index sensors based on the tilted fiber Bragg grating (TFBG) structure by resonant coupling of small spherical nanoparticles to the TFBG resonances. The optimal choice of nanoparticle parameters is discussed.

Bialiayeu, A.; Ianoul, A.; Albert, J.

2014-03-01

52

Index of refraction of molecular nitrogen for sodium matter waves  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

53

Aerodynamically Efficient Gradient Refractive Index Missile Seeker Lens.  

National Technical Information Service (NTIS)

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 see...

H. M. Carr

1982-01-01

54

Refractive index measurement through image analysis with an optofluidic device.  

PubMed

We present a novel optical method, to our knowledge, to measure the refractive index of liquids by means of the images produced by an optofluidic lens. In addition we propose a new method to make optofluidic lenses. PMID:22330448

Calixto, Sergio; Rosete-Aguilar, Martha; Sanchez-Marin, Francisco J; Calixto-Solano, Margarita; López-Mariscal, Carlos

2012-01-30

55

Fresnel equations and the refractive index of active media.  

PubMed

A class of realizable active media exists for which the refractive index cannot be defined as an analytic function in the upper half-plane of complex frequency. The conventional definition of the refractive index based on analyticity is modified such that it is valid for active media in general, and associated Fresnel equations are proved. In certain active media, the presence of a "backward" wave, for which both phase velocity and Poynting's vector point towards the excitation source, is demonstrated. PMID:16605469

Skaar, Johannes

2006-02-01

56

Refractive Index of Water in the Infrared.  

National Technical Information Service (NTIS)

The infrared reflectance of water at incidence angles of 70 and 75 degrees has been measured in the spectral region between 2 and 25 micromicrons. The measured reflectances of polarized radiant flux have been used to determine the real part of the refract...

M. R. Querry B. Curnutte D. Williams

1969-01-01

57

Photoresist Exposure Parameter Extraction from Refractive Index Change during Exposure  

NASA Astrophysics Data System (ADS)

The refractive indices of photoresist are usually measured byan ellipsometer or spectrophotometer, but the values are limited to pre-exposure. It is known thatthe real and imaginary indices are changed during the exposure.But there is little report on these variations since itis difficult to measure this refractive index change at deep ultraviolet. The DillABC parameters show a significant variation with the resist and substrate thicknessas well as the experimental conditions.A method is suggested to extract the parameters from the refractive index changes.We can get the refractive index change and extract the Dill ABC exposure parameters from that.The multiple thin film interference calculation is used to fit the measured transmittance data.The results of our experiments and calculations for several resists including193 nm chemically amplified resists are compared with other methods.The results are agreed well with the full multilayer thin film simulation.

Sohn, Young-Soo; Sung, Moon-Gyu; Lee, Young-Mi; Lee, Eun-Mi; Oh, Jin-Kyung; Byun, Sung-Hwan; Jeong, Yeon-Un; Oh, Hye-Keun; An, Ilsin; Lee, Kun-Sang; Park, In-Ho; Cho, Joon-Yeon; Lee, Sang-Ho

1998-12-01

58

Three-dimensional optical metamaterial with a negative refractive index  

Microsoft Academic Search

Metamaterials are artificially engineered structures that have properties, such as a negative refractive index, not attainable with naturally occurring materials. Negative-index metamaterials (NIMs) were first demonstrated for microwave frequencies, but it has been challenging to design NIMs for optical frequencies and they have so far been limited to optically thin samples because of significant fabrication challenges and strong energy dissipation

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

2008-01-01

59

Integrated Microfibre Device for Refractive Index and Temperature Sensing  

PubMed Central

A microfibre device integrating a microfibre knot resonator in a Sagnac loop reflector is proposed for refractive index and temperature sensing. The reflective configuration of this optical structure offers the advantages of simple fabrication and ease of sensing. To achieve a balance between responsiveness and robustness, the entire microfibre structure is embedded in low index Teflon, except for the 0.5–2 mm diameter microfibre knot resonator sensing region. The proposed sensor has exhibited a linear spectral response with temperature and refractive index. A small change in free spectral range is observed when the microfibre device experiences a large refractive index change in the surrounding medium. The change is found to be in agreement with calculated results based on dispersion relationships.

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

2012-01-01

60

Interferometric measurement of the refractive-index gradient distribution in gradient-index optical blanks  

NASA Astrophysics Data System (ADS)

A new interferometric method for measuring the refractive-index distribution in a plane-parallel section cut from a gradient-index lens blank is described. A standard double-pass interferometric scheme modified to provide a single pass of the beam through the investigated gradient-index sample is used. The two-dimensional variation of the refractive index in dimensions transverse to the sample surface is measured with an accuracy of better than 1 \\times 10-4. interferometry, nondestructive testing, refractometry, optical properties, index of refraction.

Gerasimova, L. A.

1996-06-01

61

Quantitative comparison of gradient index and refractive lenses.  

PubMed

We analyze the Seidel wavefront aberrations and spot sizes of gradient index (GRIN) singlet lenses with ?n?1. We consider and compare curved and planar GRIN lenses with F-numbers of 5 and 1 against equivalent refractive lenses. We find that the planar GRIN lenses generally have larger spot sizes compared to their refractive lens equivalents at wide angles. This appears to be due to an inability to correct for coma by adjusting the refractive index gradient alone. We can correct for the coma by bending the GRIN lens. This results in a singlet lens with performance close to but not exceeding that of the equivalent refractive lens. We also examine the impact of anisotropy on the planar GRIN lenses. We find that fabricating the planar GRIN lenses from a uniaxial medium has the potential to improve the performance of the lenses. PMID:23201812

Nguyen, Vinh; Larouche, Stéphane; Landy, Nathan; Lee, Jae Seung; Smith, David R

2012-11-01

62

Construction of glass waveguide refractive index profiles by the effective-index finite-difference method  

Microsoft Academic Search

A numerical method is applied to construct the refractive index profiles of optical waveguides from the measured effective indices (EI). The method is based on choosing a proper analytical function for the refractive index profile and searching its unknown parameters using the simplex search algorithm. Simultaneously, the finite-difference method (FDM) is used to solve the semi-vectorial Helmholtz equation for the

F. Gonella; A. Quaranta; A. Sambo; F. Caccavale; I. Mansour

1996-01-01

63

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

NASA Astrophysics Data System (ADS)

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

Bai, Kunlun; Katz, Joseph

2014-04-01

64

Probing multifractality in tissue refractive index: prospects for precancer detection.  

PubMed

Multiresolution analysis on the spatial refractive index inhomogeneities in the epithelium and connective tissue regions of a human cervix reveals a clear signature of multifractality. Importantly, the derived multifractal parameters, namely, the generalized Hurst exponent and the width of the singularity spectrum, derived via multifractal detrended fluctuation analysis, shows interesting differences between tissues having different grades of precancers. The refractive-index fluctuations are found to be more anticorrelated, and the strength of multifractality is observed to be considerably stronger in the higher grades of precancers. These observations on the multifractal nature of tissue refractive-index variations may prove to be valuable for developing light-scattering approaches for noninvasive diagnosis of precancer and early-stage cancer. PMID:23454965

Das, Nandan; Chatterjee, Subhasri; Soni, Jalpa; Jagtap, Jaidip; Pradhan, Asima; Sengupta, Tapas K; Panigrahi, Prasanta K; Vitkin, I Alex; Ghosh, Nirmalya

2013-01-15

65

Using plasma experiments to illustrate a complex index of refraction  

NASA Astrophysics Data System (ADS)

The index of refraction for the propagation of a wave in a plasma depends on the plasma density, background magnetic field, and frequency of the wave. The study of plasma wave propagation is an excellent tool for teaching students the subtleties involved in a complex media rather than in glass or water where the index of refraction is close to a constant. Whistler waves were launched and detected in a plasma physics laboratory at UCLA devoted to involving high school students and teachers. The magnetic field of the wave was measured in space and time and the wavenumbers at a variety of frequencies were determined. The index of refraction predicted by Appleton's equation was used to reconstruct the two-dimensional phase fronts and compared to the laboratory data with excellent agreement. The experimental techniques are discussed in conjunction with their use as an educational tool.

Gekelman, W.; Pribyl, P.; Wise, J.; Lee, A.; Hwang, R.; Eghtebas, C.; Shin, J.; Baker, B.

2011-09-01

66

Terahertz refractive index sensors using dielectric pipe waveguides.  

PubMed

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

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

2012-03-12

67

Femtosecond laser-induced refractive index modification in multicomponent glasses  

NASA Astrophysics Data System (ADS)

We present a comprehensive study on femtosecond laser-induced refractive index modification in a wide variety of multicomponent glasses grouped as borosilicate, aluminum-silicate, and heavy-metal oxide glasses along with lanthanum-borate and sodium-phosphate glasses. By using high-spatial resolution refractive index profiling techniques, we demonstrate that under a wide range of writing conditions the refractive index modification in multicomponent glasses can be positive, negative, or nonuniform, and exhibits a strong dependence on the glass composition. With the exception of some aluminum-silicate glasses all other glasses exhibited a negative/nonuniform index change. We also demonstrate direct writing of waveguides in photosensitive Foturan® glass with a femtosecond laser without initiating crystallization by thermal treatment. Upon ceramization of lithium-aluminum-silicate glasses such as Foturan®, Zerodur®, and Robax® we observe switching of laser-induced refractive index change from being positive to negative. The measured transmission losses in the waveguides at 1550 nm agree with the index profile measurements in alkali-free aluminum-silicate glasses.

Bhardwaj, V. R.; Simova, E.; Corkum, P. B.; Rayner, D. M.; Hnatovsky, C.; Taylor, R. S.; Schreder, B.; Kluge, M.; Zimmer, J.

2005-04-01

68

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

69

Determination of the effective refractive index of nanoparticulate ITO layers.  

PubMed

Nanoparticles of transparent conducting oxides, such as indium tin oxide, can be used in printing techniques to generate functional layers for various optoelectronic devices. Since these deposition methods do not create fully consolidated films, the optical properties of such layers are expected to be notably different from those of the bulk material and should be characterized on their own. In this work we present a way to measure the effective refractive index of a particulate ITO layer by refraction of light. The obtained data points are used to identify an accurate layer model for spectroscopic ellipsometry. In this way the complex refractive index of the particle layer is determined in a wide spectral range from ultra violet to near infrared. PMID:24104162

Baum, M; Alexeev, I; Latzel, M; Christiansen, S H; Schmidt, M

2013-09-23

70

Thermal radiation in quasiperiodic photonic crystals with negative refractive index  

NASA Astrophysics Data System (ADS)

In this work we investigated the thermal power spectrum of the electromagnetic radiation through one-dimensional stacks of alternating negative and positive refractive index layers, arranged as truncated quasiperiodic photonic structures obeying the Fibonacci (FB), Thue-Morse (TM), and double-period (DP) sequences. The thermal radiation power spectra are determined by means of a theoretical model based on a transfer matrix formalism for both normal and oblique incidence geometries, together with Kirchoff's second law. We studied the radiation spectra by considering the case where both refractive indices of layers A and B are assumed to be a constant, as well as a more realistic case which takes into account the frequency-dependent electric permittivity epsilon and magnetic permeability ? to characterize the negative refractive index n in layer B.

de Medeiros, F. F.; Albuquerque, E. L.; Vasconcelos, M. S.; Mauriz, P. W.

2007-12-01

71

Gradients of refractive index in the crystalline lens and transient changes in refraction among patients with diabetes  

PubMed Central

Transient hyperopic refractive shifts occur on a timescale of weeks in some patients after initiation of therapy for hyperglycemia, and are usually followed by recovery to the original refraction. Possible lenticular origin of these changes is considered in terms of a paraxial gradient index model. Assuming that the lens thickness and curvatures remain unchanged, as observed in practice, it appears possible to account for initial hyperopic refractive shifts of up to a few diopters by reduction in refractive index near the lens center and alteration in the rate of change between center and surface, so that most of the index change occurs closer to the lens surface. Restoration of the original refraction depends on further change in the refractive index distribution with more gradual changes in refractive index from the lens center to its surface. Modeling limitations are discussed.

Charman, W. Neil; Adnan; Atchison, David A.

2012-01-01

72

Gradients of refractive index in the crystalline lens and transient changes in refraction among patients with diabetes.  

PubMed

Transient hyperopic refractive shifts occur on a timescale of weeks in some patients after initiation of therapy for hyperglycemia, and are usually followed by recovery to the original refraction. Possible lenticular origin of these changes is considered in terms of a paraxial gradient index model. Assuming that the lens thickness and curvatures remain unchanged, as observed in practice, it appears possible to account for initial hyperopic refractive shifts of up to a few diopters by reduction in refractive index near the lens center and alteration in the rate of change between center and surface, so that most of the index change occurs closer to the lens surface. Restoration of the original refraction depends on further change in the refractive index distribution with more gradual changes in refractive index from the lens center to its surface. Modeling limitations are discussed. PMID:23243557

Charman, W Neil; Adnan; Atchison, David A

2012-12-01

73

High-refractive-index polymer coatings for optoelectronics applications  

NASA Astrophysics Data System (ADS)

The performance of many solid-state devices including emissive displays, optical sensors, integrated optical circuits, and light-emitting diodes can be improved by applying a transparent high refractive index coating (>= 1.65) onto the light-emitting or light-sensing portion of the device. Ideally, the coating should combine the excellent durability and easy deposition of a spin-applied polymer coating with the high refractive index and optical clarity of a vacuum deposited metal oxide coating such as titanium dioxide or zirconium oxide. While some success has been achieved in combining these very dissimilar materials to form transparent hybrid coating systems, for example, using sol-gel or nanoparticle dispersion techniques, the resulting coating systems often require complicated manufacturing schemes and have limited storage stability and reliability. We have demonstrated two new approaches to development of high refractive index polymer coatings. In the first approach, an organometallic polymer and a conventional organic polymer are combined to form a compatible coating. When cured at elevated temperatures, the organometallic polymer decomposes to form a highly dispersed metal oxide phase that imparts high index properties to the final hybrid coating. The new coatings are transparent and have refractive indices ranging from 1.6 to as high as 1.9 depending on the metal oxide content. The second approach utilizes our discovery that polyimide materials possess naturally high refractive indices in comparison to most polymer materials. Through careful molecular design, we have developed a new class of polyimide materials having refractive indices ranging from 1.60 to 1.78 at visible wavelengths and exhibiting excellent optical clarity. The new polyimides can be spin-applied to a layer thickness of more than 10 microns in a single coating step and form thermally stable films with good mechanical strength and adhesion to device substrates.

Flaim, Tony D.; Wang, Yubao; Mercado, Ramil

2004-02-01

74

Nanostructured Composite Layers With Quasi-Zero Refractive Index  

NASA Astrophysics Data System (ADS)

Nanostructured composite transparent layers based on an acrylic copolymer and silver nanoparticles and synthesized by a technology developed by us are found to have quasi-zero refractive index over a wide range of wavelengths (450-1000 nm) according to an analysis and interpretation of experimental reflection and transmission spectra.

Gadomsky, O. N.; Stepin, S. N.; Katnov, V. E.; Zubkov, E. G.

2013-11-01

75

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

76

Aerodynamically efficient gradient refractive index missile seeker lens  

Microsoft Academic Search

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

H. M. Carr III

1982-01-01

77

Thinned fiber Bragg gratings as high sensitivity refractive index sensor  

Microsoft Academic Search

In this work, the numerical and experimental analysis on the use of thinned fiber Bragg gratings as refractive index sensors have been carried out. Wet chemical etching in a buffered hydrofluoric acid solution was used for sensor fabrication. Experimental characterization for an almost full etched cladding sensor is presented demonstrating good agreement with numerical results and resolutions of ?10-5 and

A. Iadicicco; A. Cusano; A. Cutolo; R. Bernini; M. Giordano

2004-01-01

78

Amplification without inversion and high refractive index in heterogeneous molecules  

NASA Astrophysics Data System (ADS)

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

Budriga, O.

2014-10-01

79

Unidirectional transmission using array of zero-refractive-index metamaterials  

NASA Astrophysics Data System (ADS)

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

2014-05-01

80

Measurement of refractive index of photopolymer for holographic gratings  

NASA Astrophysics Data System (ADS)

We have made attempts to measure directly the small-scale variation of optical path lengths in photopolymer samples. For those with uniform thickness, the measured quantity is supposed to be proportional to the refractive index of the photopolymer. The system is based on a Mach-Zehnder interferometer using phase-locking technique and measures the change in optical path length during the sample is scanned across the optical axis. The spatial resolution is estimated to be 2?m, which is limited by the sample thickness. The path length resolution is estimated to be 6nm, which corresponds to the change in refractive index less than 10-3 for the sample of 10?m thick. The measurement results showed clearly that the refractive index of photopolymer is not simply proportional to the exposure energy, contrary to the conventional photosensitive materials such as silver halide emulsion and dichromated gelatine. They also revealed the refractive index fluctuation in uniformly exposed photopolymer sample, which explains the milky appearance that sometimes observed in thick samples.

Watanabe, Eriko; Mizuno, Jun; Fujikawa, Chiemi; Kodate, Kashiko

2007-03-01

81

The Refractive Index of an Ionized Medium. II  

Microsoft Academic Search

The aim of the work is to confirm and to clarify a result in an earlier paper which showed that the refractive index of an ionized medium is given by mu 2 - 1 = -4 pi Ne2\\/mv2 and not by the corresponding formula in 3(mu 2 - 1)\\/(mu 2 + 2). This is done by a direct analysis of

Charles Darwin

1943-01-01

82

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

83

Probing a possible vacuum refractive index with ?-ray telescopes  

NASA Astrophysics Data System (ADS)

We have used a stringy model of quantum space-time foam to suggest that the vacuum may exhibit a non-trivial refractive index depending linearly on ?-ray energy: ?-1˜E/M, where M is some mass scale typical of quantum gravity that may be ˜10 GeV: see [J. Ellis, N.E. Mavromatos, D.V. Nanopoulos, Phys. Lett. B 665 (2008) 412] and references therein. The MAGIC, HESS and Fermi ?-ray telescopes have recently probed the possible existence of such an energy-dependent vacuum refractive index. All find indications of time-lags for higher-energy photons, but cannot exclude the possibility that they are due to intrinsic delays at the sources. However, the MAGIC and HESS observations of time-lags in emissions from AGNs Mkn 501 and PKS 2155-304 are compatible with each other and a refractive index depending linearly on the ?-ray energy, with M˜10 GeV. We combine their results to estimate the time-lag ?t to be expected for the highest-energy photon from GRB 080916c measured by the Fermi telescope, which has an energy ˜13.2 GeV, assuming the redshift z=4.35±0.15 measured by GROND. In the case of a refractive index depending linearly on the ?-ray energy we predict ?t=26±11 s. This is compatible with the time-lag ?t?16.5 s reported by the Fermi Collaboration, whereas the time-lag would be negligible in the case of a refractive index depending quadratically on the ?-ray energy. We suggest a strategy for future observations that could distinguish between a quantum-gravitational effect and other interpretations of the time-lags observed by the MAGIC, HESS and Fermi ?-ray telescopes.

Ellis, John; Mavromatos, N. E.; Nanopoulos, D. V.

2009-04-01

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

Refractive index and birefringence of 2H silicon carbide  

NASA Technical Reports Server (NTRS)

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

Powell, J. A.

1972-01-01

86

Precise Measurement of Refractive Index and Absorption Coefficient of Near Millimeter Wave and Far Infrared Materials.  

National Technical Information Service (NTIS)

It is no longer necessary to use extrapolated microwave dielectric values when designing millimeter wave components and systems. Our recent highly accurate broadband millimeter wave data on complex refractive index, complex refractive index, complex diele...

M. N. Afsar K. J. Button

1983-01-01

87

Refractive Index Method for at Line Determinations of Hydrogen Peroxide in Cleaning Baths.  

National Technical Information Service (NTIS)

Density and refractive index methods for determining hydrogen peroxide in cleaning baths were compared to the potassium permanganate titration method. The refractive index method was shown to be rapid and simple and required only a few drops of sample. Th...

D. M. Kapsch H. A. Woltermann

1979-01-01

88

Ultrafast refractive index control of a terahertz graphene metamaterial.  

PubMed

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

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

2013-01-01

89

The whistler mode refractive index as a function of gyrofrequency  

SciTech Connect

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

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

2011-08-15

90

INDEX OF REFRACTION OF SHOCK LOADED SODA-LIME GLASS  

SciTech Connect

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

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

2009-12-28

91

Refractive index changes during germination of bacillus subtilis spores  

NASA Astrophysics Data System (ADS)

Light transmission measurements in the wavelength range of 400 to 1000 nm were performed on Bacillus subtilis spores at periodic time intervals after heat-shock induced activation. The Gaussian ray approximation, using a concentric sphere model for the spore coat and spore core, was used to calculate the scattering cross-section of the spores. Analysis of transmission spectra determined that the refractive index of the spore core was 1.515. In the three hours following heat shock, the core refractive index decreased to 1.39, and subsequently remained constant. During the measurements, the spore radius increased from 0.38 microns to 0.6 microns. The results were confirmed by phase contrast microscopy.

Katz, Alvin; Alimova, Alexandra; Xu, Min; Rudolph, Elizabeth; Gottlieb, Paul; Steiner, J. C.; Alfano, Robert R.

2005-04-01

92

Transition of refractive index contrast in course of grating growth  

NASA Astrophysics Data System (ADS)

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

Sabel, Tina; Zschocher, Michael

2013-08-01

93

Refractive index compensation in over-determined interferometric systems.  

PubMed

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

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

2012-01-01

94

Refractive index modification using fs-laser double pulses.  

PubMed

Buried waveguides in glass are manufactured by irradiation with femtosecond laser double pulses. The refractive index change Deltan is determined by measuring the numerical aperture NA of the waveguides and by through light microscopy. The value of Deltan shows a significant dependency on the time delay Deltat of the fs-laser double pulses. A Deltan of up to 2x10(-3) in fused silica is reached at a Deltat between 400 and 800 ps. Based on the results of the double pulse experiments the initial effects of the refractive index change are discussed, taking into account thermal effects and the formation of self trapped excitons (STE) and transient color centers and their interaction with the next laser pulse. PMID:19547363

Wortmann, Dirk; Ramme, Mark; Gottmann, Jens

2007-08-01

95

Refractive Index Compensation in Over-Determined Interferometric Systems  

PubMed Central

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

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

2012-01-01

96

Accurate refractive index profiling in a graded-index plastic optical fiber exceeding gigabit transmission rates  

Microsoft Academic Search

An optimum index profile offering the highest bit rate communication was formed in a poly methyl methacrylate (PMMA)-based graded-index plastic optical fiber (GI-POF) by modifying the polymerization process. The interfacial-gel polymerization process we have proposed to fabricate the PMMA-based GI-POF is capable of forming a nearly optimum refractive index profile. However, the theoretically calculated bandwidth from the measured index profile

Takaaki Ishigure; Sho Tanaka; Eiji Kobayashi; Yasuhiro Koike

2002-01-01

97

Refractive Index of Lithium Fluoride Ramp Compressed to 800 GPa  

NASA Astrophysics Data System (ADS)

The compression of materials to high pressure can alter their optical properties in ways that provide insight into the resulting structural changes. Under strong shock compression, transparent insulators transform into conducting fluids as a result of pressure-induced reduction of the band gap and thermal promotion of electrons across that gap. LiF is ramp compressed to 800 GPa on the Omega Laser Facility without generating shocks, producing high pressures at significantly lower temperatures than would be created by shock waves. Ramp compressed lithium fluoride (LiF) is observed to remain transparent to 800 GPa, pressures seven times higher than previous shock compression experiments. The ramp-compressed refractive index of LiF is measured at pressures up to 800 GPa and depends linearly on density. This is the highest-pressure refractive index measurement made to date. The linear dependence of the refractive index and density is examined using a single oscillator model. This model indicates that the linear behavior is a result of monoatomic closure of the band gap. Extrapolation of these results indicates that the band gap closure (metallization) will be greater than 4,000 GPa. The high metallization pressure of LiF is attributed to its large band gap and isoelectronic counterparts that exhibit high metallization pressures. The observed high-pressure transparency and measurement of LiF refractive index enables advancement of in situ experiments to higher-pressure regimes. In collaboration with T.R. Boehly (LLE), M.A. Barrios (LLE -- now at LLNL), D.D. Meyerhofer (LLE), J.H. Eggert (LLNL), R.F. Smith (LLNL), D.G. Hicks (LLNL), P.M. Celliers (LLNL), and G.W. Collins (LLNL).

Fratanduono, Dayne

2011-11-01

98

Synthesis of Transparent Densely Crosslinked Polysiloxane with High Refractive Index  

Microsoft Academic Search

Densely crosslinked polysiloxane, with high refractive index and high transparency, was synthesized via co-hydrolysis\\/condensation and then cured via hydrosilylation with a Pt catalyst. Si nuclear magnetic resonance (NMR) spectra were utilized to identify the process of co-hydrolysis\\/condensation and characterize the structures of the prepolymers. Fourier transform infrared spectroscopy (FTIR) was used to investigate the hydrosilylation reaction. The number-average molecular weight

Jin Wang; Ming-Liang Du; Cong-Sheng Xu; Han Zhu; Ya-Qin Fu

2012-01-01

99

Thermal radiation in quasiperiodic photonic crystals with negative refractive index  

Microsoft Academic Search

In this work we investigated the thermal power spectrum of the electromagnetic radiation through one-dimensional stacks of alternating negative and positive refractive index layers, arranged as truncated quasiperiodic photonic structures obeying the Fibonacci (FB), Thue-Morse (TM), and double-period (DP) sequences. The thermal radiation power spectra are determined by means of a theoretical model based on a transfer matrix formalism for

F. F. de Medeiros; E. L. Albuquerque; M. S. Vasconcelos; P. W. Mauriz

2007-01-01

100

Thermal radiation in quasiperiodic photonic crystals with negative refractive index  

Microsoft Academic Search

In this work we investigated the thermal power spectrum of the electromagnetic radiation through one-dimensional stacks of alternating negative and positive refractive index layers, arranged as truncated quasiperiodic photonic structures obeying the Fibonacci (FB), Thue–Morse (TM), and double-period (DP) sequences. The thermal radiation power spectra are determined by means of a theoretical model based on a transfer matrix formalism for

F F de Medeiros; E L Albuquerque; M S Vasconcelos; P W Mauriz

2007-01-01

101

Fiber optic-based refractive index sensing at INESC Porto.  

PubMed

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

102

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.

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

2012-01-01

103

A simple optical probing technique for nonlinearly induced refractive index  

NASA Astrophysics Data System (ADS)

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

Banerjee, Partha; Abeywickrema, Ujitha

2013-09-01

104

Laser optical gas sensor by photoexcitation effect on refractive index.  

PubMed

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

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

2010-03-20

105

Microvolume index of refraction determinations by interferometric backscatter  

NASA Astrophysics Data System (ADS)

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

Bornhop, Darryl J.

1995-06-01

106

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.

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

2013-01-01

107

Flexible zero refractive index optical metamaterial with matched impedance  

NASA Astrophysics Data System (ADS)

We demonstrate a flexible thin film zero refractive index optical metamaterial with matched impedance to free space and low absorption loss at 1.55 ?m. The metallo-dielectric multilayer structure with fishnet geometry was optimized by a genetic algorithm. The fabrication process and characterization approach are described. The experiment results agree well with the theoretical predictions, showing an effective index of neff = 0.072 + 0.51i and an impedance of Zeff/Z0 = 1.009 - 0.021i.

Yun, Seokho; Lin, Lan; Jiang, Zhi Hao; Ma, Ding; Liu, Zhiwen; Werner, Douglas H.; Mayer, Theresa S.

108

Measurement of the refractive index of the LAB-based liquid scintillator and acrylic at RENO  

Microsoft Academic Search

In this paper, we describe the first measurement of the refractive index of the linear alkyl benzene (LAB)-based liquid scintillator and acrylic used at the Reactor Experiment for Neutrino Oscillation (RENO). The refractive index of a material is an important optical property and the prism spectrometer is the most common device for measuring the refractive index. Using the minimum deviation

I. S. Yeo; J. H. Jang; M. S. Kim; J. K. Ahn; S. R. Baik; E. I. Choi; Seonho Choi; Y. Choi; H. I. Jang; J. S. Jang; E. J. Jeon; I. S. Jeong; K. K. Joo; B. C. Kim; H. S. Kim; J. Y. Kim; S. B. Kim; S. H. Kim; W. Kim; Y. D. Kim; J. Lee; I. T. Lim; K. J. Ma; Y. D. Oh; M. Y. Pac; I. G. Park; J. S. Park; K. S. Park; J. W. Shin; S. S. Stepanyan; B. S. Yang; I. Yu

2010-01-01

109

Construction of glass waveguide refractive index profiles by the effective-index finite-difference method  

NASA Astrophysics Data System (ADS)

A numerical method is applied to construct the refractive index profiles of optical waveguides from the measured effective indices (EI). The method is based on choosing a proper analytical function for the refractive index profile and searching its unknown parameters using the simplex search algorithm. Simultaneously, the finite-difference method (FDM) is used to solve the semi-vectorial Helmholtz equation for the guided modes effective indices. The method is applied successfully to two particular Ag +?Na + ion-exchanged glass slab waveguides. The results are as accurate as those obtained from from commonly used IWKB-based method. The EI-FDM in principle can be applied to both slab and channel waveguides and does not require that the index profiles are monotonically decreasing, like most of IWKB-based methods. The relation between the induced refractive index and silver concentration profile, measured by SIMS, is found to be almost linear.

Gonella, F.; Quaranta, A.; Sambo, A.; Caccavale, F.; Mansour, I.

1996-05-01

110

Highly sensitive refractive index sensor based on two cascaded special long-period fiber gratings with rotary refractive index modulation.  

PubMed

We present a refractive index (RI) sensor based on a fiber Mach-Zehnder interferometer (MZI) formed by two cascaded special long-period fiber gratings (LPFGs) with rotary refractive index modulation (RLPFGs), in which the coupling occurred between the guided mode and the high-order asymmetric cladding mode. The experimental results show that the RI sensitivity of a refractometer with an interaction length of 40?mm is up to 58.8?nm/RI in the range of 1.3344 to 1.3637, which is 3.5 times higher than that of an MZI formed by two normal LPFGs. The temperature sensitivity for the same parameters of an RLPFG-MZI is about 0.03?nm/°C. Such a kind of high-sensitivity, easy-to-fabricate and simple-structure interferometer may find applications in the chemical or biochemical sensing fields. PMID:21833138

Fan, Yan-en; Zhu, Tao; Shi, Leilei; Rao, Yun-Jiang

2011-08-10

111

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

112

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

113

High refractive index and temperature sensitivity LPGs for high temperature operation  

NASA Astrophysics Data System (ADS)

A fiber optic sensor for high sensitivity refractive index and temperature measurement able to withstand temperature up to 450 °C is reported. Two identical LPG gratings were fabricated, whereas one was coated with a high refractive index (~1.78) sol-gel thin film in order to increase its sensitivity to the external refractive index. The two sensors were characterized and compared in refractive index and temperature. Sensitivities of 1063 nm/RIU (1.338 - 1.348) and 260 pm/°C were achieved for refractive index and temperature, respectively.

Nascimento, I. M.; Gouveia, C.; Jana, Surnimal; Bera, Susanta; Baptista, J. M.; Moreira, Paulo; Biwas, Palas; Bandyopadhyay, Somnath; Jorge, Pedro A. S.

2013-11-01

114

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

115

Homogeneous polymer blend microparticles with a tunable refractive index  

SciTech Connect

We show that homogeneous polymer blend microparticles can be prepared {ital in situ} from droplets of dilute solution of codissolved polymers. Provided that the droplet of solution is small enough ({lt}10 {mu}m) , solvent evaporation is rapid enough to inhibit phase separation. Thus the polymers that are being mixed need not be miscible, which greatly enhances the applicability of the technique. From analysis of two-dimensional Fraunhofer diffraction (angular scattering) patterns, we show that both the real and the imaginary parts of the refractive index can be tuned by adjustment of the relative weight fractions of polymers in solution. {copyright} {ital 1999} {ital Optical Society of America}

Barnes, M.D.; Kung, C.; Lermer, N.; Fukui, K.; Sumpter, B.G.; Noid, D.W. [Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6142 (United States); Otaigbe, J.U. [Department of Materials Science, Iowa State University, Ames, Iowa 50011 (United States)

1999-02-01

116

Temperature Coefficients of the Refractive Index for Complex Hydrocarbon Mixtures  

NASA Astrophysics Data System (ADS)

Temperature coefficients of the refractive index (dn/dT ) in the 25° C to 35° C temperature interval for hydrocarbon mixtures containing as many as 14 compounds were investigated in this work. The measured -dn/dT of the mixtures were compared with calculations based on the values for each compound and their concentrations. Differences of about 1 % between measured and calculated values were observed for all mixtures. The additivity of -dn/dT for these hydrocarbons enables preparation of surrogate fuels that are formulated to have properties like those of specific diesel fuels.

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

2014-05-01

117

Glory oscillations in the index of refraction for matter waves.  

PubMed

We have measured the index of refraction for sodium de Broglie waves in gases of Ar, Kr, Xe, and N2 over a wide range of sodium velocities. We observe glory oscillations--a velocity-dependent oscillation in the forward scattering amplitude. An atom interferometer was used to observe glory oscillations in the phase shift caused by the collision, which are larger than glory oscillations observed in the cross section. The glory oscillations depend sensitively on the shape of the interatomic potential, allowing us to discriminate among various predictions for these potentials, none of which completely agrees with our measurements. PMID:12443465

Roberts, Tony D; Cronin, Alexander D; Kokorowski, David A; Pritchard, David E

2002-11-11

118

Measurements of nonlinear refractive index in scattering media  

PubMed Central

We have recently developed a spectral re-shaping technique to simultaneously measure nonlinear refractive index and nonlinear absorption. In this technique, the information about the nonlinearities is encoded in the frequency domain, rather than in the spatial domain as in the conventional Z-scan method. Here we show that frequency encoding is much more robust with respect to scattering. We compare spectral re-shaping and Z-scan measurements in a highly scattering environment and show that reliable spectral re-shaping measurements can be performed even in a regime that precludes standard Z-scans.

Samineni, Prathyush; Perret, Zachary; Warren, Warren S.; Fischer, Martin C.

2012-01-01

119

RICH with multiple aerogel layers of different refractive index  

NASA Astrophysics Data System (ADS)

A proximity focusing ring imaging Cherenkov detector with multiple aerogel radiator layers is studied. In situations where limited space is available and a compact RICH detector is required, the use of a nonhomogeneous, multiple refractive index radiator offers a possibility for improving the resolution. Experimental investigations of the relevant parameters, i.e. single photon Cherenkov angle uncertainty and number of detected photons per ring, are presented for different aerogel radiator configurations. The results are promising and appear to satisfy the requirements for the forthcoming upgrade of the particle identification system of the Belle detector.

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

2005-11-01

120

High-refractive-index measurement with an elastomeric grating coupler  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

121

The Density and Refractive Index of Adsorbing Protein Layers  

PubMed Central

The structure of the adsorbing layers of native and denatured proteins (fibrinogen, ?-immunoglobulin, albumin, and lysozyme) was studied on hydrophilic TiO2 and hydrophobic Teflon-AF surfaces using the quartz crystal microbalance with dissipation and optical waveguide lightmode spectroscopy techniques. The density and the refractive index of the adsorbing protein layers could be determined from the complementary information provided by the two in situ instruments. The observed density and refractive index changes during the protein-adsorption process indicated the presence of conformational changes (e.g., partial unfolding) in general, especially upon contact with the hydrophobic surface. The structure of the formed layers was found to depend on the size of the proteins and on the experimental conditions. On the TiO2 surface smaller proteins formed a denser layer than larger ones and the layer of unfolded proteins was less dense than that adsorbed from the native conformation. The hydrophobic surface induced denaturation and resulted in the formation of thin compact protein films of albumin and lysozyme. A linear correlation was found between the quartz crystal microbalance measured dissipation factor and the total water content of the layer, suggesting the existence of a dissipative process that is related to the solvent molecules present inside the adsorbed protein layer. Our measurements indicated that water and solvent molecules not only influence the 3D structure of proteins in solution but also play a crucial role in their adsorption onto surfaces.

Voros, Janos

2004-01-01

122

Size dependence of complex refractive index function of growing nanoparticles  

NASA Astrophysics Data System (ADS)

The evidence of the change of the complex refractive index function E( m) of carbon and iron nanoparticles as a function of their size was found from two-color time-resolved laser-induced incandescence (TiRe-LII) measurements. Growing carbon particles were observed from acetylene pyrolysis behind a shock wave and iron particles were synthesized by pulse Kr-F excimer laser photo-dissociation of Fe(CO)5. The magnitudes of refractive index function were found through the fitting of two independently measured values of particle heat up temperature, determined by two-color pyrometry and from the known energy of the laser pulse and the E( m) variation. Small carbon particles of about 1-14 nm in diameter had a low value of E( m)˜0.05-0.07, which tends to increase up to a value of 0.2-0.25 during particle growth up to 20 nm. Similar behavior for iron particles resulted in E( m) rise from ˜0.1 for particles 1-3 nm in diameter up to ˜0.2 for particles >12 nm in diameter.

Eremin, A.; Gurentsov, E.; Popova, E.; Priemchenko, K.

2011-08-01

123

Refractive index sensing using Fluorescence Lifetime Imaging (FLIM)  

NASA Astrophysics Data System (ADS)

The fluorescence lifetime is a function of the refractive index of the fluorophore's environment, for example in the case of the biologically important green fluorescent protein (GFP). In order to address the question whether this effect can be exploited to image the local environment of specific proteins in cell biology, we need to determine the distance over which the fluorophore's lifetime is sensitive to the refractive index. To this end, we employ Fluorescence Lifetime Imaging (FLIM) of fluorescein in NaOH buffer at an interface. This approach allows us to map the fluorescence lifetime as a function of distance from a buffer/air and buffer/oil interface. Preliminary data show that the fluorescence lifetime of fluorescein increases near a buffer/air interface and decreases near a buffer/oil interface. The range over which this fluorescence lifetime change occurs is found to be of the order several µm which is consistent with a theoretical model based on the full width at half maximum of the emission spectrum proposed by Toptygin.

Jones, Carolyn; Suhling, Klaus

2006-07-01

124

Double cavity refractive index photonic crystal sensor temperature calibrated  

NASA Astrophysics Data System (ADS)

In this paper we present a preliminary study to realize an integrated photonic crystal double cavities refractive index sensor calibrated in temperature. The studied conguration allows to realize a very compact device with only one interrogation channel, since the monitored signals are the cavities re ected signals. The sensitive elements used are the modulation of the cavities linewidth due to temperature and refractive index change, measured by means of the cavities detuning. The appeal of such type of devices, respect to the corresponding ones in optical bers, is the possibility to expand the conguration to create on the same chip the detector and the requested signal processing devices. The reliability of the proposed conguration is related to the interrogation technique, based on the radio-frequency phase modulation of the impinging laser light. This techniques was widely demonstrated in the last years1-4 and initially borrowed by the cavity frequency stabilization and locking Pound-Drever-Hall methods.5 Here we demonstrate as it is possible to use it for simultaneously detection of the detuning of two cavities with only one interrogation channel.

De Laurentis, Martina; Irace, Andrea; Breglio, Giovanni

2012-05-01

125

Press-patterned UV-curable high refractive index coatings  

NASA Astrophysics Data System (ADS)

The research and development of organic materials for use in optical components and devices aims to take advantage of several unique properties of these materials, including their stability, tailorability, and flexibility. In this study, by carefully controlling the components, we have developed a material that offers significant advantages over common optical materials. Specifically, the new material has a high refractive index and is curable with ultraviolet (UV) light, solvent free, and transparent over a wide wavelength range. We applied the material to a substrate via spin coating, although other application methods are possible. The production of optical components through press-patterning has received a large amount of attention. The low cost of replication and high throughput of the process provide the potential for low-cost optical components. Typically a metallic plate is patterned via electroplating or electroforming to produce a negative image on the plate. This plate is then pressed into the patternable material and subsequently treated to form the desired pattern in the organic material. Here we report our initial attempts at press-patterning structures into a UV-curable high refractive index material.

Morford, Robert; Shih, Wu-Sheng; Dachsteiner, JoElle

2006-03-01

126

Refractive index sensor based on the leaky radiation of a microfiber.  

PubMed

In this work we present a refractive index sensor based on the leaky radiation of a microfiber. The 5.3um diameter microfiber is fabricated by drawing a commercial optical fiber. When the microfiber is immersed into a liquid with larger refractive index than the effective index of fiber mode, the light will leak out through the leaky radiation process. The variation of refractive index of liquid can be monitored by measuring radiation angle of light. The refractive index sensitivity can be over 400 degree/RIU in theory. In the experiment, the variation value 0.001 of refractive index of liquid around this microfiber can be detected through this technique. This work provides a simple and sensitive method for refractive index sensing application. PMID:24921381

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

2014-05-19

127

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

128

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

PubMed

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. PMID:21743527

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

2011-07-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

130

Highly sensitive sensor for detecting refractive index change of liquids using single microfiber  

Microsoft Academic Search

We demonstrate a novel sensor capable of detecting small refractive index change of liquids using single microfiber. The sensor is based on the principle of differential frequency technique and is used to measure the variation of refractive index with concentration of glucose in distilled water. Our experimental results show that the device exhibits the capability of measuring an index variation

Chenghua Sui; Pinghui WUI; Biqing Ye

2010-01-01

131

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

132

Complex refractive index of starch acetate used as a biodegradable pigment and filler of paper  

NASA Astrophysics Data System (ADS)

Complex refractive index of strongly depolarizing starch acetate is investigated as a function of bulk package density, which is compulsory parameter in analysis of light scattering from nanoscale starch acetate pigments and fillers. The measurements were made using a laser-goniometer and spectrophotometer to gain data for refractive index analysis according to the Brewster's law and Fresnel equations. The real part of refractive index was verified by microscopic immersion method.

Karvinen, Petri; Oksman, Antti; Silvennoinen, Raimo; Mikkonen, Hannu

2007-05-01

133

Electromagnetic scattering by spherical negative-refractive-index particles: Low-frequency resonance and localization parameters  

Microsoft Academic Search

The Mie scattering of electromagnetic waves of wave vector k by spherical negative-refractive-index particles of radius a exhibits an unusual resonance at ka-->0. The scattering enhancement from the ka-->0 resonance is insensitive to the size of scatterers, distinct from the Mie scattering resonances from positive-refractive-index particles. For media consisting of a collection of the negative-refractive-index particles, the unusual resonance results

Zheng Liu; Zhifang Lin; S. T. Chui

2004-01-01

134

Full-vectorial analysis of complex refractive index photonic crystal fibers  

Microsoft Academic Search

We investigated the modal properties of complex refractive-index core photonic crystal fibers (PCFs) with the supercell model. The validity of the approach is shown when we compare our results with those reported earlier on a step complex refractive-index profile. The imaginary part of the electric field results in wave-front distortion in the complex refractive-index profile PCFs, which means that the

Ren Guobin; Wang Zhi; Lou Shuqin; Liu Yan; Jian Shuisheng

2004-01-01

135

Temperature dependence of refractive index of glassy SiO 2 in the infrared wavelength range  

Microsoft Academic Search

An interferometric method was used for the determination of refractive index of glassy SiO2 in the infrared (IR) wavelength region (1.44refractive index was found to increase with temperature at a given wavelength. Irregularities of the thermal coefficient of the refractive index (dn\\/dT) with temperature were observed and explained

C. Z. Tan; J. Arndt

2000-01-01

136

Complex refractive index of Martian dust - Wavelength dependence and composition  

NASA Technical Reports Server (NTRS)

The size distribution and complex refractive index of Martian dust-cloud particles observed in 1971 with the Mariner 9 UV spectrometer are determined by matching the observed single-scattering albedo and phase function with Mie-scattering calculations for size distributions of spheres. Values of phase function times single-scattering albedo are presented for 12 wavelength intervals in the range from 190 to 350 nm, and best-fit values are obtained for the absorption index. It is found that the absorption index of the dust particles increases with decreasing wavelength from 350 to about 210 nm and then drops off shortward of 210 nm, with a structural shoulder occurring in the absorption spectrum between 240 and 250 nm. A search for a candidate material that can explain the strong UV absorption yields TiO2, whose anatase polymorph has an absorption spectrum matching that of the Martian dust. The TiO2 content of the dust particles is estimated to be a few percent or less.

Pang, K.; Ajello, J. M.

1977-01-01

137

Dependence of the Radiation Pressure on the Background Refractive Index  

NASA Astrophysics Data System (ADS)

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

Webb, Kevin J.

2013-07-01

138

Integrated refractive index optical ring resonator detector for capillary electrophoresis.  

PubMed

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

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

2007-02-01

139

Time variation of refractive index in the core of active fiber under pulsed optical pumping  

Microsoft Academic Search

The kinetics of refractive index change in active fiber under pulsed cladding-coupled optical pumping was investigated using interferometric technique. Relaxation processes after lasing threshold was observed.

V. V. Gainov; O. A. Ryabushkin

2008-01-01

140

Highly refractive index sensitive femtosecond laser inscribed long period gratings  

NASA Astrophysics Data System (ADS)

The distinct behaviour of femtosecond laser inscribed long period gratings, with a non-uniform index perturbation within the optical fibre core, has been studied experimentally. The non-uniform laser-induced perturbation results in light coupling from the core mode to a greater number of cladding modes than is the case with their UV laser inscribed counterparts, and this is made evident from the surrounding refractive index (SRI) grating response. Femtosecond inscribed long period gratings are shown to simultaneously couple to multiple sets of cladding modes. A 400?m LPG is shown to result in attenuation peaks that have both blue and red wavelength shifts over a 1250nm to 1700nm wavelength range. This gives rise to SRI sensitivities far greater than anything achievable by monitoring a single attenuation peak. The maximum sensitivity produced by monitoring a single attenuation peak was 1106nm/RIU, whereas monitoring opposing wavelength shifts resulted in a significantly improved sensitivity of 1680nm/RIU.

Davies, Edward; Kalli, Kyriacos; Koutsides, Charalambos; Zhang, Lin

2011-05-01

141

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

142

Optical refractive index of massive particles and physical meanings of left-handed media [rapid communication  

NASA Astrophysics Data System (ADS)

In this Letter the expression for the refractive index of de Broglie wave in the presence of a potential field is obtained and based on this, the physical meanings of negative index of refraction is revealed. We demonstrate that the electromagnetic wave propagation in a left-handed medium with negative refractive index behaves just like that of antiphotons, which is required of the complex vector field theory. It is believed that the complex vector field theory is helpful in considering the wave propagation and photonic band gap structures in the left-handed medium photonic crystals with a periodicity in negative and positive indices of refraction.

Shen, Jian Qi

2005-09-01

143

Thermal emission of a semi-transparent slab with variable spatial refractive index  

Microsoft Academic Search

The directional emission intensities emerging from a parallel plane slab or semi-transparent media in which is imposed a variable spatial refractive index, have been determined by a curved ray-tracing method determining the trajectories of radiation propagation and integrating the radiative transfer equation on each of these trajectories. Cases of linear and sinusoidal refractive indexes are examined, for both isothermal and

P. Ben Abdallah; V. Le Dez

2000-01-01

144

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

EPA Science Inventory

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

145

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

2014-05-01

146

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

147

Imaging and 3D tomographic reconstruction of time-varying, inhomogeneous refractive index fields  

Microsoft Academic Search

Time varying, inhomogeneous refractive index fields are every-where, from hot air rising above a fire and mirages above hot roads in the summer, to gases flowing from pressurized containers, and mixtures of different liquids. We present a novel method for imaging and volumetric reconstruction of time-varying refractive index fields, based on the Background Oriented Schlieren (BOS) technique developed in the

Bradley Atcheson; Ivo Ihrke; Derek Bradley; Wolfgang Heidrich; Marcus Magnor; Hans-Peter Seidel

2007-01-01

148

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

149

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

Microsoft Academic Search

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 ?4 (TO) band

Carl W. Ponader; Joseph F. Schroeder; Alexander M. Streltsov

2008-01-01

150

Origin of the refractive index modification of femtosecond laser processed doped phosphate glass  

Microsoft Academic Search

The origin of the local refractive index modification in femtosecond laser inscribed structures has been investigated with confocal microfluorescence imaging. We have identified the origin of both, positive and negative refractive index changes in a commercial Er-Yb codoped phosphate glass upon irradiation in the low repetition rate regime (1 kHz). Consistent relations among the photoluminescence behavior of the dopants (erbium

Andrés Ferrer; Daniel Jaque; Jan Siegel; Alexandro Ruiz De La Cruz; Javier Solís

2011-01-01

151

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

152

Pressure dependence of the refractive index of monoclinic and yttria-stabilized cubic zirconia  

Microsoft Academic Search

The pressure dependence of the refractive index of monoclinic and yttria-stabilized cubic zirconia was measured up to 3 and 8 GPa, respectively, using an interferometric method with the diamond-anvil cell. The experimental results show a practically linear behavior for both crystalline structures. For cubic zirconia, the refractive index remains practically constant under pressure, while for the biaxial monoclinic phase, one

N. M. Balzaretti; J. A. H. da Jornada

1995-01-01

153

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

SciTech Connect

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

Smith, Charlene M.; Borrelli, Nicholas F. [Science and Technology Division, Corning Incorporated Corning, New York 14830 (United States)

2006-09-15

154

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

155

Intense Ion Beam Diode Studies with Refractive Index Gradient Diagnostics  

NASA Astrophysics Data System (ADS)

A new modification of Refractive INdex Gradient (RING) diagnostics with a laser beam probe(M.E. Cuneo et al., IEEE Trans. on Plasma Science 19), 800 (1991). is being developed to study processes in the anode plasma in intense ion beam diodes. The beam centroid deflection angle and angular characteristics of the laser beam after passing through the plasma/gas layer adjacent to the anode of an ion diode are measured simultaneously by using a differential bi-cell photodiode and Fourier-transform optics with a streak camera as a detector. A spatial resolution of 0.25 mm was achieved with a long-focal length, ``three-telescope'' optical system. Initial measurements on the ion-beam diode on the COrnell Beam Research Accelerator (COBRA) indicated that the maximum density gradient in the anode plasma at the peak of the diode voltage (t ? 40ns, V_diode ? 800 kV) for a diode gap of 5 mm was about 0.35 mm from the anode. The plasma density there was about 3 \\cdot 10^15 cm-3. The plasma layer expanded away from the anode and, 100-150 ns after the voltage pulse, was replaced near the anode surface by a neutral component at a density of ~ 10^17 cm-3. Further experiments on COBRA are in progress. Work supported by Sandia Contract AF-1660.

Knyazev, B. A.; Greenly, J. B.; Hammer, D. A.; Krastelev, E. G.; Chen, C.; Cuneo, M. E.

1996-11-01

156

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.

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

2011-01-01

157

Full-field refractive index distribution measurement of a gradient-index lens with heterodyne interferometry  

NASA Astrophysics Data System (ADS)

A light beam coming from a circular heterodyne light source with an electro-optic modulator is incident on a gradient-index lens obliquely. The reflected light passes through an analyzer and an imaging lens, and is recorded by a fast CMOS camera. A group of periodic sinusoidal segments recorded by each pixel is modified, and its associated phase is derived with a unique technique. The processes are applied to other pixels; the two-dimensional phase distribution can be obtained similarly. The estimated data are substituted into the special equations derived from Fresnel's equations, and the full-field refractive index distribution of the gradient-index lens can be obtained. This method has the merits of both common-path interferometry and heterodyne interferometry.

Hsieh, Hung-Chih; Chen, Yen-Liang; Wu, Wang-Tsung; Chang, Wei-Yao; Su, Der-Chin

2010-10-01

158

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

PubMed

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

Biswal, Akshaya Kumar

2013-01-01

159

Refractive Index for Atomic Waves: Theory and Detailed Calculations  

NASA Astrophysics Data System (ADS)

This paper describes new theoretical results and calculations concerning the recently introduced index of refraction of a gas for atomic waves. More precisely, the motion of the atoms of the gas is taken into account and the equation describing the Doppler and Fizeau effects is introduced. The case where the atoms of the wave and the gas have spin 1/2 is also discussed and the rotatory power and circular dichroism of an optically pumped gas is calculated. Finally, the index of the rare gases for sodium waves is calculated. The results show how important it is to take into account glory scattering and Doppler averaging to make a meaningful comparison with experiments. The index appears to be very sensitive to the precise value of the quantum parameter B = 2? D_e?^2 (in atomic unit). Using the available interaction potential curves, we obtained a reasonably good agreement between the measurements and the corresponding calculated values. However, some experimental results appear difficult to explain with the best available interaction potentials. Ce travail présente une étude théorique de l'indice de réfraction pour une onde de matière se propageant dans un gaz. Le calcul de l'indice prend en compte le mouvement des atomes du gaz et met en évidence les effets Doppler et Fizeau. Le cas où les atomes du gaz et ceux de l'onde ont un spin 1/2 est également discuté, ce qui permet le calcul du pouvoir rotatoire et du dichroïsme circulaire d'un gaz optiquement pompé. Finalement, l'indice de l'hélium, du néon, de l'argon, du krypton et du xénon est calculé pour une onde de sodium. Ces calculs montrent l'importance des effets de gloire et de la moyenne thermique. Ces effets doivent donc être pris en compte pour l'interprétation précise des résultats expérimentaux. De plus, il apparaît que l'indice dépend fortement du paramètre quantique B = 2? D_e?^2 (en unité atomique). En utilisant les potentiels sodium gaz rares disponibles dans la littérature, nous obtenons un accord raisonnable entre l'indice calculé et les résultats expérimentaux. Cependant, il reste difficile de rendre compte de certaines valeurs expérimentales avec les meilleurs potentiels actuellement disponibles.

Champenois, C.; Audouard, E.; Duplàa, P.; Vigué, J.

1997-04-01

160

Refractive index change during exposure for 193-nm chemically amplified resists  

NASA Astrophysics Data System (ADS)

Some of the important areas to be improved for lithography simulation are getting correct exposure parameters and determining the change of refractive index. It is known that the real and imaginary refractive indices are changed during exposure. We obtained these refractive index changes during exposure for 193 nm chemically amplified resists. The variations of the transmittance as well as the resist thickness were measured during ArF excimer laser exposure. We found that the refractive index change is directly related to the concentration of the photo acid generator and de-protected resin. It is important to know the exact values of acid concentration from the exposure parameters since a small difference in acid concentration magnifies the variation in the amplified de-protection during post exposure bake. We developed and used a method to extract Dill ABC exposure parameters for 193 nm chemically amplified resist from the refractive index change upon exposure.

Oh, Hye-Keun; Sohn, Young Soo; Sung, Moon Gyu; Lee, Young Mi; Lee, Eun Mi; Byun, Sung Hwan; An, Ilsin; Lee, Kun-Sang; Park, In-Ho

1999-05-01

161

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

NASA Technical Reports Server (NTRS)

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

Russell, P. B.; Hamill, P.

1984-01-01

162

Real refractive index: Dependence on relative humidity and solute composition with relevancy to atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

A closure evaluation of the hygroscopic response in refractive index (n) was completed with measurements and a semi-empirical model using aqueous solutions containing inorganic salts, dicarboxylic acids, and their mixtures. Measurements of n were made for subsaturated aqueous solutions at select mass fractions of solute with an ellipsometer and a refractometer. The semi-empirical model was based on the Zdanovskii-Stokes-Robinson (ZSR) mixing rule, the partial molar refraction (PMR) method and previously published thermodynamic data. Closure was obtained within 0.75%, as represented by the average absolute error, for n values obtained from the ellipsometry/refractometry measurements and the ZSR-PMR model for aqueous solutions. It was observed that the hygroscopic response of n on relative humidity could be described by a linear equation. Sensitivity of the top of the atmosphere aerosol radiative forcing to changes in n is also discussed. Finally, strengths and limitations for the ellipsometer, the refractometer, and the ZSR-PMR method, are discussed.

Wang, Wei; Rood, Mark J.

2008-12-01

163

High-bandwidth plastic optical fiber with W-refractive index profile  

Microsoft Academic Search

A plastic optical fiber having a W-shaped refractive index profile [W-shaped plastic optical fiber (POF)] was prepared for the first time to realize a higher bit rate transmission than those of the conventional silica-based multimode fiber and graded-index (GI) POF links. Since the W-shaped POF has a valley of the refractive index at the boundary of the core and cladding

Takaaki Ishigure; Hideki Endo; Kunihiro Ohdoko; Yasuhiro Koike

2004-01-01

164

Modal bandwidth enhancement in a plastic optical fiber by W-refractive index profile  

Microsoft Academic Search

A plastic optical fiber (POF) having a W-shaped refractive index profile (W-shaped POF) was prepared for the first time that had a possibility to realize a higher bit rate transmission than those of the conventional silica-based multimode fiber and graded index (GI) POF links. Since the W-shaped POF has a valley of the refractive index at the boundary of the

Takaaki Ishigure; Hideki Endo; Kunihiro Ohdoko; Keita Takahashi; Yasuhiro Koike

2005-01-01

165

Antireflective property of thin film a-Si solar cell structures with graded refractive index structure.  

PubMed

We report the antireflective property of thin film amorphous silicon (a-Si) solar cell structures based on graded refractive index structure together with theoretical analysis. Optimizations of the index profile are performed using the rigorous coupled-wave analysis method. The graded refractive index structure fabricated by oblique angle deposition suppresses optical reflection over a wide range of wavelength and incident angle, compared to the conventional structure. The average reflectance of thin film a-Si solar cell structure with the graded refractive index structure is suppressed by 54% at normal incidence due to the effective refractive index matching between ITO and a-Si, indicating a reasonable agreement with calculated results. PMID:21445212

Jang, Sung Jun; Song, Young Min; Yeo, Chan Il; Park, Chang Young; Yu, Jae Su; Lee, Yong Tak

2011-03-14

166

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

167

Determination of refractive index and thickness of thin-film from reflectivity spectrum using genetic algorithm  

NASA Astrophysics Data System (ADS)

The precise determination of refractive index (n) of material and thickness (t) of thin-films are desirable for many applications in the field of optics and optoelectronics. In the proposed work, we have utilized a computational genetic algorithm (GA) to find the refractive index and the thickness from the experimentally measured reflectivity spectra of thin-film. The algorithm was implemented using the Lab VIEW as a programming tool. The obtained results show that the prepared algorithm successfully calculates the spectral dependence of refractive index and thickness of thin-films by fitting an experimentally measured reflectivity spectra with the calculated ones.

Patel, Sanjaykumar J.; Kheraj, Vipul

2013-06-01

168

Enhancing intensity and refractive index sensing capability with infrared plasmonic perfect absorbers.  

PubMed

An infrared refractive index sensor based on plasmonic perfect absorbers for glucose concentration sensing is experimentally demonstrated. Utilizing substantial absorption contrast between a perfect absorber (?98% at normal incidence) and a non-perfect absorber upon the refractive index change, a maximum value of figure of merit (FOM*) about 55 and a bulk wavelength sensitivity about 590??nm/RIU are achieved. The demonstrated sensing platform provides great potential in improving the performance of plasmonic refractive index sensors and developing future surface enhanced infrared spectroscopy. PMID:24876008

Cheng, Fei; Yang, Xiaodong; Gao, Jie

2014-06-01

169

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

170

Refractive-Index-Matched Indium-Tin-Oxide Electrodes for Liquid Crystal Displays  

NASA Astrophysics Data System (ADS)

Refractive-index-matched indium-tin-oxide (ITO) electrode for thin-film transistor liquid crystal displays is presented to reduce optical losses caused by Fresnel reflections. Simulations show a 24% improvement in optical transmittance when the conventional dense ITO is replaced with the refractive-index-matched ITO in a stack of glass/ITO/liquid crystal/ITO/glass. The refractive-index-matched ITO, fabricated by oblique-angle deposition technique, shows higher optical transmittance and smaller dependency on film thickness and wavelength than conventional dense ITO.

Yan, Xing; Mont, Frank W.; Poxson, David J.; Schubert, Martin F.; Kim, Jong Kyu; Cho, Jaehee; Schubert, E. Fred

2009-12-01

171

Two-core transversally chirped microstructured optical fiber refractive index sensor.  

PubMed

We present a sensing architecture consisting of a two-core chirped microstructured optical fiber (MOF) for refractive index sensing of fluids. We show that by introducing a chirp in the hole size, the MOF can be a structure with decoupled cores, forming a Mach-Zehnder interferometer in which the analyte directly modulates the device transmittance by its differential influence on the effective refractive index of each core mode. We show that by filling all fiber holes with analyte, the sensing structure achieves high sensitivity (transmittance changes of 300 per RIU at 1.42) and has the potential for use over a wide range of analyte refractive index. PMID:24690846

Torres, Pedro; Reyes-Vera, Erick; Díez, Antonio; Andrés, Miguel V

2014-03-15

172

Hybrid FBG-LPG sensor for surrounding refractive index and temperature simultaneous discrimination  

NASA Astrophysics Data System (ADS)

In this work, we propose a configuration of a hybrid fiber Bragg grating together with a long period grating sensor used for simultaneously detect surrounding refractive index and temperature to be applied in aqueous environment and to reveal pollution. We present the simulation of such sensor and analyze the reflected wavelength and amplitude variations of the fiber Bragg grating spectrum to obtain the temperature and the external refractive index variations, respectively. The results show that the fiber Bragg grating reflected amplitude change depends on the variation of the long period grating transmission spectrum with the surrounding refractive index modification and the reflected wavelength shift depends on the temperature of the aqueous solution.

Chamorro Enríquez, Daniel Alfredo; da Cruz, Alberto R.; Rocco Giraldi, Maria Thereza M.

2012-06-01

173

Refractive-index increase in laser-written waveguides in glasses  

NASA Astrophysics Data System (ADS)

We present estimates of the refractive-index change in waveguides in silica produced by focused femtosecond laser pulses. The estimates are based on the shift of the central frequency of ? 4 (TO) band (Si-O stretching mode) in micro-Raman spectra. These data were compared with the relation of this parameter to density and to refractive index changes in seen in glasses modified by high pressure or irradiation. We conclude that the measured refractive-index increase in the waveguides can be explained by densification of glass.

Streltsov, Alexander M.; Ponader, Carl W.; Schroeder, Joseph F., III

2006-05-01

174

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

PubMed

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. PMID:20935706

Chen, Ji-Huan; Zhao, Jia-Rong; Huang, Xu-Guang; Huang, Zhen-Jian

2010-10-10

175

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

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

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

SciTech Connect

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

Hattori, Koichi, E-mail: khattori@yonsei.ac.kr [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)] [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Itakura, Kazunori, E-mail: kazunori.itakura@kek.jp [Theory Center, IPNS, High energy accelerator research organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan) [Theory Center, IPNS, High energy accelerator research organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Department of Particle and Nuclear Studies, Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2013-07-15

178

Negative refractive index metamaterials supporting 2-D waves  

Microsoft Academic Search

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

Ashwin K. Iyer; George V. Eleftheriades

2002-01-01

179

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

Thome, Kurtis; Gubbels, Timothy; Barnes, Robert

2011-01-01

180

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

181

Effect of refractive index in optical particle sizing by using spatial frequency method  

Microsoft Academic Search

Investigation of optical particle sizing by using spatial frequency method was conducted by analytical and experimental methods. An equation to determine the optimized optical observation angles for different relative refractive indices of media was derived. The sensitivity of the spatial frequency varying with the relative refractive index of media and the polarization angle of the incident beams was simulated by

H.-H. Qiu; W. Jia

2000-01-01

182

Influence of hydrogen ion concentration on refractive index value in red blood cells of diabetes patients  

Microsoft Academic Search

Since hyperglycaemia changes fluidity of erythrocyte cell membrane and impair cell deformability, our goal was to characterize light refractive properties of haemoglobin and red blood cells (RBC) in diabetes patients. Microscopic investigation was carried out on intact and in methanol fixed RBCs of diabetes patients with long-term hyperglycaemia (glycosylated haemoglobin > 7,5%). Interference microscopy was used for refractive index (RI)

Gunta Mazarevica; Talivaldis Freivalds; Antra Jurka

2002-01-01

183

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

184

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

Microsoft Academic Search

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

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

2003-01-01

185

Ionization effect on arc plasma's optical diagnosis by the measurement of the refractive index.  

PubMed

The effect of arc plasma ionization on its temperature diagnosis by the measurement of the refractive index is discussed. The refractive index of arc plasma in two conditions is compared: 1) only the first ionization is considered and 2) both the first and second ionizations are considered. In order to facilitate plasma temperature reconstruction, two corresponding refractive index models are deduced. For the sake of making this study universal, both the monatomic and dual-atomic molecule arc plasmas are chosen as typical examples for theoretical deduction and analysis. A condition, which can be adopted to estimate whether the second ionization should be considered in temperature reconstruction, is proposed. Finally, an argon arc plasma is chosen as an example for experiment, and the experimental results match well with the theoretical analysis. This study is crucial to arc plasma's optical diagnosis, which is based on the measurement of the refractive index. PMID:22695575

Chen, Yun-yun; Zhang, Cheng-yi; Gu, Fang; Wang, Qing-hua; Li, Zhen-hua

2012-06-01

186

Cladding modes analysis of photonics crystal fiber for refractive index sensors using Finite Element method  

Microsoft Academic Search

We developed a Finite Element package to analyze cladding mode field extensions into the air-holes of photonics crystal fiber for refractive index sensing. Our analysis could determine the most sensitive cladding mode for liquid sensing.

Naeem Khurram; Linh Viet Nguyen; Kamal Alameh; Youngjoo Chung

2010-01-01

187

Refractive index dispersion functions of solid-phase polymers by multicolor optical diffraction  

SciTech Connect

We show that fourth-order dispersion functions of solid-phase polymers can be determined by multicolor optical diffraction. Electrodynamically trapped microparticles of polyethylene glycol with different molecular weights were probed by two-dimensional optical diffraction with four different laser wavelengths (632.8, 514.5, 488.0, and 457.9 nm); subsequent Mie analysis of one-dimensional scattering patterns yielded size and refractive index (both real and imaginary parts). Using a single wavelength as a size reference, the nonlinear dependence of the refractive index of solid (nonevaporating) polymer microparticles was determined by finding the refractive index for a given wavelength that best matched a Mie calculation subject to the reference size constraint. The experimentally determined refractive index values were fit to a standard fourth-order Cauchy function to obtain values for n{sub 0}, n{sub 1}, and n{sub 2}.

Ford, J. V.; Sumpter, B. G.; Noid, D. W.; Barnes, M. D.; Otaigbe, J. U.

2000-10-16

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.

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

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

190

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

191

Measuring High-Frequency Humidity, Temperature and Radio Refractive Index in the Surface Layer.  

National Technical Information Service (NTIS)

Three different instrument systems are compared in their ability to either directly measure humidity, temperature, and refractive-index fluctuations. Each system consists of a basic instrument--a Lyman-alpha hygrometer, an infrared absorption hygrometer o...

J. T. Priestley R. J. Hill

1985-01-01

192

A refractive index sensor based on the resonant coupling to cladding modes in a fiber loop.  

PubMed

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

193

Simple Near-Field Scanning System for Refractive Index Profiles and Mode Spot Shape.  

National Technical Information Service (NTIS)

Measurements of refractive index profile and mode spot intensity distribution are fundamentally important for singlemode fiber characterization. Using the Transmitted Near Field technique, the two measurements are essentially the same, but with different ...

C. A. Millar

1984-01-01

194

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.

Reyes, Mauricio; Monzon-Hernandez, David; Martinez-Rios, Alejandro; Silvestre, Enrique; Diez, Antonio; Cruz, Jose Luis; Andres, Miguel V.

2013-01-01

195

Integral refractive index determination of living suspension cells by multifocus digital holographic phase contrast microscopy.  

PubMed

A method for the determination of the integral refractive index of living cells in suspension by digital holographic microscopy is described. Digital holographic phase contrast images of spherical cells in suspension are recorded, and the radius as well as the integral refractive index are determined by fitting the relation between cell thickness and phase distribution to the measured phase data. The algorithm only requires information about the refractive index of the suspension medium and the image scale of the microscope system. The specific digital holographic microscopy advantage of subsequent focus correction allows a simultaneous investigation of cells in different focus planes. Results obtained from human pancreas and liver tumor cells show that the integral cellular refractive index decreases with increasing cell radius. PMID:17994897

Kemper, Björn; Kosmeier, Sebastian; Langehanenberg, Patrik; von Bally, Gert; Bredebusch, Ilona; Domschke, Wolfram; Schnekenburger, Jürgen

2007-01-01

196

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

197

Methods for Prediction of Refractive Index in Glasses for the Infrared  

SciTech Connect

It is often useful to obtain custom glasses that meet particular requirements of refractive index and dispersion for high-end optical design and applications. In the case of infrared glasses, limited experimental data are available due to difficulties in processing of these glasses and also measuring refractive indices accurately. This paper proposes methods to estimate refractive index and dispersion as a function of composition for selected infrared-transmitting glasses. Methods for refractive index determination are reviewed and evaluated, including Gladstone-Dale, Wemple-DiDomenico single oscillator, Optical basicity, and Lorentz-Lorenz total polarizability. Various estimates for a set of PbO-Bi2O3-Ga2O3 (heavy metal oxide) and As-S (chalcogenide) glasses will be compared with measured values of index and dispersion.

McCloy, John S.

2011-06-14

198

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

NASA Astrophysics Data System (ADS)

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

Anderson, Benjamin R.; Kuzyk, Mark G.

2014-05-01

199

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

NASA Astrophysics Data System (ADS)

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 ?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.

2008-03-01

200

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.

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

2013-01-01

201

Thermal emission of a two-dimensional rectangular cavity with spatial affine refractive index  

Microsoft Academic Search

The directional emission intensities emerging from a two-dimensional rectangular cavity of semi-transparent media in which is imposed a spatial variable refractive index, have been determined by a curved ray-tracing method determining the trajectories of radiation propagation and integrating the radiative transfer equation on each of these trajectories. Cases of affine refractive indexes with respect to the space variables are examined,

P. Ben Abdallah; V. Le Dez

2000-01-01

202

Improved self-imaging for multi-mode optical fiber involving cladding refractive index  

NASA Astrophysics Data System (ADS)

In this work, improved self-imaging for optical fiber is proposed. For the first time, a precise formula of reimaging distance involving normalized frequency and cladding refractive index is given. By using our proposal, we can estimate the reimaging distance and evaluate the impact of cladding refractive index precisely and effectively. This method can be used to analyze multi-mode fiber interferences, especially no-core fiber interference.

Zheng, Jingjing; Li, Jing; Ning, Tigang; Pei, Li; Jian, Shuisheng; Wen, Yinghong

2013-01-01

203

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.

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

2011-01-01

204

Refractive index of laser active region based on InAs/InGaAs quantum dots  

NASA Astrophysics Data System (ADS)

The effective refractive index of the active region of 1.3 ?m edge-emitting tilted wave lasers based on InAs/InGaAs self-assembled quantum dots by the analysis of the far-field pattern is investigated. The obtained values of 3.485 and 3.487 in the operating lasers and in the cold waveguides, respectively, are well comparable with the refractive index of bulk InAs at corresponding wavelength.

Gordeev, Nikita Yu; Rumyantsev, Oleg I.; Savenko, Ivan G.; Payusov, Alexey S.; Zubov, Fedor I.; Maximov, Mikhail V.; Zhukov, Alexey E.

2013-01-01

205

A laser multifocus system for measurements of particle size, velocity and refractive index  

NASA Astrophysics Data System (ADS)

This paper describes a laser multifocus velocimeter (LMFV) using a phase diffraction grating to measure particle diameter, velocity, and refractive index. The optical system is easily constructed by the use of the grating. As the fringe of the LMFV is sharp and wide, the LMFV makes it possible to measure high velocity and large diameter with high accuracy compared with an LDV. The diameter, velocity, and refractive index can be measured simultaneously and easily by this instrument.

Nakatani, N.; Kohri, S.; Yamada, T.; Sakabe, T.

206

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

Microsoft Academic Search

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

Anthony Grbic; George V. Eleftheriades

2002-01-01

207

Planar optical waveguides for optical panel having gradient refractive index core  

DOEpatents

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

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

2001-01-01

208

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

Microsoft Academic Search

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 omega4 (TO) band

Carl W. Ponader; Joseph F. Schroeder; Alexander M. Streltsov

2008-01-01

209

Refractive index method for at line determinations of hydrogen peroxide in cleaning baths  

Microsoft Academic Search

Density and refractive index methods for determining hydrogen peroxide in cleaning baths were compared to the potassium permanganate titration method. The refractive index method was shown to be rapid and simple and required only a few drops of sample. This method exhibited a +- 0.14% HâOâ standard deviation for a single measurement and an average bias of - 0.002% HâOâ

D. M. Kapsch; H. A. Woltermann

1979-01-01

210

Measurements of the nonlinear refractive index of freestanding porous silicon layers at different wavelengths  

Microsoft Academic Search

Measurements of the nonlinear refractive index n2 of a high-porosity freestanding porous silicon sample are reported at different laser wavelengths by means of the z-scan technique. The results show a negative below-gap nonlinear refractive index, so that thermal contributions to the observed effects can be reasonably excluded. Values for n2 of the order of 10-9 esu are here reported. These

S. Lettieri; P. Maddalena; L. P. Odierna; D. Ninno; V. La Ferrara; G. di Francia

2001-01-01

211

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

213

The measurement of refractive index homogeneity of the large diameter Ge plate using interferometry  

NASA Astrophysics Data System (ADS)

The method is presented to measure the homogeneity of the refractive index of infrared optical material, germanium (Ge) plate, using infrared interferometer working at 10.6?m. In order to measure the refractive index homogeneity of large diameter infrared material, the infrared standard lens is used in the test arm of infrared interferometer. The Ge plate is placed in the infrared spherical wave brought by infrared standard lens. The difference is measured between the wavefront with Ge plate and the one without Ge plate by the infrared interferometer working at 10.6?m. The addition aberration caused by Ge plate needs to be eliminated with Zernike polynomials fit from the results. As the Ge plate is too soft to process, its surface form may not meet the requirement for the measurement. In order to improve the measuring accuracy of the refractive index homogeneity, the surface deformations of two boundaries of the Ge plate are measured by phase-shifting digital interferometer working at 0.6328?m. The surface deformations are removed from the result of the refractive index homogeneity measurement. In this way, the measuring accuracy of the refractive index homogeneity is up to 10-5. A piece of Ge plate is tested. The peak-valley (PV) value of its refractive index deviation is 3.65×10-5, and the root mean square (RMS) value is 4.11×10-6.

He, Jun; Chen, Lei

2009-11-01

214

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

215

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

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

Refraction of Electromagnetic Energy for Wave Packets Incident on a Negative Index Medium: Always Negative  

NASA Astrophysics Data System (ADS)

Since all physical radiation sources admit their radiation in the form of wave packets, we analyze refraction of electromagnetic wave packets on passing from an isotropic positive (PIM) to an isotropic negative index medium (NIM). We definitively show that in all cases the energy is always refracted negatively. For localized waves, the group refraction is always negative. We accomplish this by treating comprehensively group refraction at a PIM-NIM interface by analytical and numerical treatment of several exhaustive examples: localized wave packets, beams, and also a finite number of plane waves. We focus on physically important quantities such as the energy flow and momentum. In all of the cases we show that the energy and momentum refract negatively. We show that in all cases where the wave group does not extend to infinity in the perpendicular direction of the wave vector, the interference pattern also refracts negatively. Work supported by NSF-0098801 and AFRL, Hanscom.

Sokoloff, J. B.; Lu, W. T.; Sridhar, S.

2003-03-01

218

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.

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

2013-01-01

219

An MMI-based wavelength combiner employing non-uniform refractive index distribution.  

PubMed

A novel wavelength combiner using non-uniform refractive index distribution within a multimode interference device is proposed and simulated. The refractive index step creates separate localized modes with different effective refractive indices and two modes are strongly excited which form the basis of an interferometer. We applied the concept to 1.30/1.31 ?m and 1.31/1.55 ?m wavelength combiners on an InP substrate. The lengths of the devices are 1272 ?m and 484 ?m with simulated insertion losses of 0.6 dB and 0.67 dB respectively. PMID:24718225

Singh, Siddharth; Kojima, Keisuke; Koike-Akino, Toshiaki; Wang, Bingnan; Parsons, Kieran; Nishikawa, Satoshi; Yagyu, Eiji

2014-04-01

220

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

PubMed Central

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

Cherkezyan, Lusik; Subramanian, Hariharan; Stoyneva, Valentina; Rogers, Jeremy D.; Yang, Seungmoo; Damania, Dhwanil; Taflove, Allen; Backman, Vadim

2012-01-01

221

Investigation of index of refraction changes in chalcogenide glasses during molding processes  

NASA Astrophysics Data System (ADS)

Precision glass molding has a well-documented effect of a decrease in the index of refraction of the glass during the molding process. This index drop has such significant value that optical designs for molded lenses must take into account the index drop to accurately determine the optical performance of the final lens. Widespread adoption of chalcogenide glasses for molded infrared optics has raised a series of questions as to the behavior of these glasses under molding conditions. This paper will investigate the index of refraction changes in two different chalcogenide glasses and determine if these changes are significant enough for optical designers to consider in their designs.

Novak, Jacklyn; Pini, Ray; Moreshead, William V.; Stover, Erik; Symmons, Alan

2013-10-01

222

Measurements of the refractive indices and refractive index increment of a synthetic PMMA solutions at 488 nm  

NASA Astrophysics Data System (ADS)

We describe a Mach-Zehnder interferometer (MZI) method for measuring the refractive index (RI) of polymethyl-methacrylate (PMMA) solution in both acetone and methyl-ethyl-ketone (MEK). The measurements are made as a function of concentration values 4, 8, 12, 16 and 20 g/l at a wavelength of 488 nm with a high degree of accuracy tends to 1.4×10 -5. The refractive index increments (RIIs) d n/d c of PMMA in both investigated solvents are determined too. In addition, the RIIs ? n as a function of concentration and the RIIs at zero concentration (d n/d c) c=0 are determined for both solvents accurately. The PMMA solutions in acetone and MEK solvents are chosen for laser light scattering investigations.

Ghazy, R.; El-Baradie, B.; El-Shaer, A.; El-Mekawey, F.

1999-12-01

223

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

NASA Astrophysics Data System (ADS)

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

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

1999-10-01

224

Temperature-insensitive miniaturized fiber inline Fabry-Perot interferometer for highly sensitive refractive index measurement.  

PubMed

We report a miniaturized fiber inline Fabry-Perot interferometer (FPI), with an open micro-notch cavity fabricated by one-step fs laser micromachining, for highly sensitive refractive index measurement. The device was tested for measurement of the refractive indices of various liquids including isopropanol, acetone and methanol at room temperature, as well as the temperature-dependent refractive index of deionized water from 3 to 90 degrees C. The sensitivity for measurement of refractive index change of water was 1163 nm/RIU at the wavelength of 1550 nm. The temperature cross-sensitivity of the device was about 1.1x10(-6) RIU/degrees C. The small size, all-fiber structure, small temperature dependence, linear response and high sensitivity, make the device attractive for chemical and biological sensing. PMID:18542685

Wei, Tao; Han, Yukun; Li, Yanjun; Tsai, Hai-Lung; Xiao, Hai

2008-04-14

225

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

Microsoft Academic Search

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

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

1993-01-01

226

Design and synthesis of low refractive index polymers for modulation in optical waveguides  

NASA Astrophysics Data System (ADS)

Design and synthesis of new electro-optic polymers are presented. These polymers have specific refractive index as low as the index of glass ion-exchange waveguides. With these materials, a novel hybrid structure can be designed for optical modulation in passive waveguide. The low index is obtained by copolymerization of an electro-optic monomer and two fluorinated comonomers. The result is a copolymer with an index close to 1.50, high electro-optic coefficient and good technical properties.

Bosc, D.; Rousseau, A.; Morand, A.; Benech, P.; Tedjini, S.

1999-11-01

227

High water content hydrogel with super high refractive index.  

PubMed

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

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

2013-11-01

228

Polarization-based refractive index sensor using dual asymmetric long-period gratings in ridge waveguides.  

PubMed

We propose a sensor scheme operating in the wavelength band of 1460-1530 nm (S band) that utilizes two orthogonally polarized eigenmodes in a ridge-waveguide geometry by employing a pair of nonidentical asymmetric long-period gratings. Numerical simulations show a high sensitivity ~4900 nm/RIU (refractive index unit) over the refractive index range 1.33-1.34 exhibiting a relative resonance shift of 1 pm for an index change of ~10(-7). Such high resolution sensors enable detection of minute changes with potential applications to various biochemical industries. PMID:23545964

Garg, Ruchi; Thyagarajan, K

2013-04-01

229

Design of hybrid coatings composed of homogeneous layers and refractive index gradients  

NASA Astrophysics Data System (ADS)

Inhomogeneous coatings are promising for superior optical properties, e.g. broadband antireflection, in comparison to conventional HL-stack designs. Although a lot of excellent theoretical work on optical behaviour of rugates and gradient index films has been done during the last decades, there is no real breakthrough in industrial fabrication. The realization of such coatings leads to an extensive and time-consuming computer-aided control, because of complicated layer designs with continuously changing refractive index gradients. We describe the design and optical performance of an omnidirectional antireflection coating that essentially represents a hybrid coating composed from homogeneous layers and linear refractive index gradient layers.

Janicki, Vesna; Leitel, Robert; Wilbrandt, Steffen; Stenzel, Olaf; Gäbler, Dieter; Kaiser, Norbert

2005-09-01

230

Refractive Index of a Transparent Liquid Measured with a Concave Mirror  

ERIC Educational Resources Information Center

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

Joshi, Amitabh; Serna, Juan D.

2012-01-01

231

Determination of optical waveguide refractive-index profiles with the inverse analytic transfer matrix method  

Microsoft Academic Search

In this paper, we present an inverse analytic transfer matrix (IATM) method to predict the refractive index profiles from the measurement of mode indices based on the analytic transfer matrix (ATM) method, which can exactly determine the modal characteristics of a planar optical waveguide with arbitrary index profiles. IATM method has been proved to be universally reliable not only in

Y. D ING; Z. Q. C AO; Q. S. S HEN

232

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

233

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

NASA Astrophysics Data System (ADS)

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

Andriyevsky, Bohdan V.

1995-11-01

234

Newton, Abbe, and the relation between refractive index and dispersion  

NASA Astrophysics Data System (ADS)

Chromatic aberration in lenses is corrected by combining glasses with different index/dispersion characteristics. The correction is based on an empirical linear relation between index and dispersion, a rule known qualitatively for many years that was given definitive form by Abbe and Schott in 1886. Despite a long history, its physical basis has remained obscure. Here we show it is a consequence of the spectral shape of the glasses' UV absorption by expanding the Kramers-Kronig relation for the index in a series of absorption-spectrum moments. To first order, the index is determined by the inverse-first moment, the dispersion by the inverse-third moment. For a complex glass, these moments may be rewritten as sums of UV-absorption moments for the glass-former and the glass-modifiers. The total index is then a sum of glass-former index plus a term proportional to the dispersion introduced by the modifier ions. The index vs. dispersion plot gives families of straight lines originating at the host-glass index/dispersion point. A line's slope is determined by the inverse-third moment of the modifier absorption, its length by the modifier concentration. Newton's erroneous conclusion that achromatic lenses could not be made was based on the limited range of glasses available to him, all of which fell on a single index-dispersion line.

Karstens, William; Smith, David Y.

2008-03-01

235

Temperature dependence of the near-infrared refractive index of silicon, gallium arsenide, and indium phosphide  

NASA Astrophysics Data System (ADS)

Infrared laser interferometry was used to measure the temperature dependence, ?(T), of the refractive index of Si, GaAs, and InP at ?=1.15, 1.31, 1.53, and 2.39 ?m. Semiconductor wafer samples that had been polished on both sides were either heated or cooled while measuring the sample temperature and the transmitted or reflected intensity of an infrared laser beam. The changing optical path length within the material causes alternating constructive and destructive interference between reflections off the front and back surfaces of the wafer. By subtracting the contribution of thermal expansion, ?(T), which is small and accurately known, ?(T) was obtained. Representative values of ? (293 K) at 1.53 ?m are 5.15×10-5 K-1, 6.65×10-5 K-1, and 5.95×10-5 K-1 for Si, GaAs, and InP. Polynomial expressions are presented for Si, GaAs, and InP, yielding values of ?(T) that are accurate to within +/-5%. $beta (T)- increases with increasing temperature and decreases with increasing wavelength. There is a large resonance enhancement of ?(T) in direct-gap semiconductors as the photon energy Eh? approaches the band-gap energy Eg. Absolute values and temperature dependences of ? calculated from published theory agree reasonably well with the measurements. The extreme accuracy in ? needed for interferometric thermometry, however, cannot be met by these theoretical calculations, and so requires the experimental measurements.

McCaulley, J. A.; Donnelly, V. M.; Vernon, M.; Taha, I.

1994-03-01

236

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

237

Retrieval of refractive index over specular surfaces for remote sensing applications  

NASA Astrophysics Data System (ADS)

Polarization knowledge is important to detect object characteristics. An approximate relationship between vertically and horizontally polarized reflectivities of specular surfaces is developed and validated using the refractive index datasets of water in the various wavelength ranges at various incidence angles. This study proposes a unique technique to estimate the refractive indexes of a specular surface at a given view angle by the direct inversion of the Fresnel equation and the decomposition of the unpolarized emissivity. The unpolarized emissivity is calculated using the Fresnel equation and the refractive index of water at wavelengths ranging from ultraviolet (200 nm) to microwave (18.75 cm). Consequently, the differences of reflectivity between the Fresnel equations and the Hong approximation are approximately less than 0.001 within the Brewster angles of a material. In addition, the results for refractive index show a reasonable range of retrievals within the Brewster's angle. The imaginary parts of the refractive indexes have larger errors than the real parts, due to the uncertainty of the direct inversion of the Fresnel equation.

Hong, Sungwook

2009-10-01

238

Simultaneous refractive index and thickness measurement with the transmission interferometric adsorption sensor  

NASA Astrophysics Data System (ADS)

Refractive index and thickness of the adlayer are determined simultaneously using the transmission interferometric adsorption sensor (TInAS). Optical biosensors, where both refractive index and thickness of a homogeneous adlayer (thus the adsorbed mass) are determined simultaneously, so-called model-free biosensors, are important tools to investigate the adsorbed mass of biomolecules with unknown conformation. Our proposed calculation method enables model-free biosensing from a single spectrum acquired by a simple TInAS setup, namely using information of peak/dip positions as well as peak/dip intensities. The feasibility of this method was experimentally tested by adsorbing polyelectrolyte multilayer as well as biomolecules. To validate the new method also for the more intricate heterogeneous adlayer, the apparent refractive index and thickness were assessed theoretically by simulating a selection of different adsorbate configurations with the multiple multipole program (MMP). We found that a lateral inhomogeneity of the adsorbate (e.g. islands or adsorbed colloids) results in correct thickness and in reduced refractive index averaged in proportion to their density while vertically inhomogeneous density caused more complex responses. However, the apparent mass was always correct. Measurement errors can lead to significant errors in the apparent refractive index, particularly when the adlayer is very thin (<5 nm). This model-free TInAS technique would be useful not only for the measurement of adsorbed mass but also for the conformational analysis of the adsorbed molecules.

Sannomiya, Takumi; Balmer, Tobias E.; Heuberger, Manfred; Vörös, Janos

2010-10-01

239

Time-resolved imaging of laser-induced refractive index changes in transparent media.  

PubMed

We describe a method to visualize ultrafast laser-induced refractive index changes in transparent materials with a 310 fs impulse response and a submicrometer spatial resolution. The temporal profile of the laser excitation sequence can be arbitrarily set on the subpicosecond and picosecond time scales with a pulse shaping unit, allowing for complex laser excitation. Time-resolved phase contrast microscopy reveals the real part of the refractive index change and complementary time-resolved optical transmission microscopy measurements give access to the imaginary part of the refractive index in the irradiated region. A femtosecond laser source probes the complex refractive index changes from the excitation time up to 1 ns, and a frequency-doubled Nd:YAG laser emitting 1 ns duration pulses is employed for collecting data at longer time delays, when the evolution is slow. We demonstrate the performance of our setup by studying the energy relaxation in a fused silica sample after irradiation with a double pulse sequence. The excitation pulses are separated by 3 ps. Our results show two dimensional refractive index maps at different times from 200 fs to 100 ?s after the laser excitation. On the subpicosecond time scale we have access to the spatial characteristics of the energy deposition into the sample. At longer times (800 ps), time-resolved phase contrast microscopy shows the appearance of a strong compression wave emitted from the excited region. On the microsecond time scale, we observe energy transfer outside the irradiated region. PMID:21456747

Mermillod-Blondin, Alexandre; Mauclair, Cyril; Bonse, Jörn; Stoian, Razvan; Audouard, Eric; Rosenfeld, Arkadi; Hertel, Ingolf V

2011-03-01

240

Note: Refractive index as an indicator for non-homogeneous solid identification  

NASA Astrophysics Data System (ADS)

Non-homogenous material such as solid composite materials examination using refractive index-sensing remains a challenge for researchers. A derivative total reflection method for simultaneous measurement of the refractive indices of various components of a non-homogeneous solid was developed. Only a measurement of the reflectance from the surface of composite sample is necessary. In our experiments, simulation samples, porcine tissue, and Rosso Levanto marble samples were measured to verify proposed method.

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

2014-01-01

241

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

242

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

NASA Astrophysics Data System (ADS)

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.

Kimura, Keisaku; Sato, Seiichi

2014-05-01

243

Nonlinear refractive index of some anthraquinone dyes in 1294-1b liquid crystal  

NASA Astrophysics Data System (ADS)

Third order nonlinear refractive index of three anthraquinone dyes, i.e., Solvent Blue 59, Solvent Blue 35 and Solvent Green 3 doped in 1294-1b nematic liquid crystal (NLC) were studied by the single beam Z-scan technique using a continuous-wave He-Ne laser at 632.8 nm. The negative nonlinear refractive index (n 2) in the order of 10 - 5 cm 2/w for all samples was obtained. We believe that, this large nonlinearity is owing to Janossy effect and the difference in the nonlinear refractive index of our dyes can be described by the structures of dyes and the interactions between dyes and 1294-1b molecules. So as to understand the effect of dye structure on nonlinearity enhancement, the dichroic ratio of these dyes in 1294-1b was measured using polarized spectroscopy.

Milanchian, K.; Abdi, E.; Tajalli, H.; Ahmadi K., S.; Zakerhamidi, M. S.

2012-03-01

244

Core-cladding mode recoupling based fiber optic refractive index sensor  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

245

A Simple Model for Measuring Refractive Index of a Liquid Based upon Fresnel Equations  

NASA Astrophysics Data System (ADS)

Due to many experimental data required and a lot of calculations involved, it is very complex and cumbersome to model prism-based liquid-refractive-index-measuring methods. We develop a new method of mathematical modelling for measuring refractive index of a liquid based upon the Fresnel formula and prism internal reflection at an incident angle less than the critical angle. With this method, only two different concentrations measurements for a kind of solution can lead to the determination of computational model. Measurements are performed to examine the validity of the theoretical model. Experimental results indicate the feasibility of the theoretical model with an error of 1%. The method is also capable of measuring even smaller changes in the optical refractive index of the material on a metal surface by the surface plasma resonance sensing techniques.

Zhang, Zhi-Wei; Wu, Zhi-Fang; Wen, Ting-Dun

2007-11-01

246

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

SciTech Connect

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

Brichard, Benoit [SCK-CEN-Belgian Nuclear Research Center, Boeretang 200, 2400 Mol (Belgium); Butov, Oleg V.; Golant, Konstantin M. [Fiber Optics Research Center, Russian Academy of Sciences, Vavilov Street 38, 119991 Moscow (Russian Federation); Fernandez Fernandez, Alberto [Masterminds Ltd., rue du Temple 40, CH-2800 Delemont (Switzerland)

2008-03-01

247

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

248

Tilted Fiber Bragg Grating photowritten in microstructured optical fiber for improved refractive index measurement.  

PubMed

We report what we believe to be the first Tilted short-period Fiber Bragg Grating photowritten in a microstructured optical fiber for refractive index measurement. We investigate the spectral sensitivity of Tilted Fiber Bragg Grating to refractive index liquid inserted into the holes of a multimode microstructured fiber. We measure the wavelength shift of the first four modes experimentally observed when calibrated oils are inserted into the fiber holes, and thus we determine the refractive index resolution for each of these modes. Moreover, a cross comparison between experimental and simulation results of a modal analysis is performed. Two simulation tools are used, respectively based on the localized functions method and on a finite element method. All results are in very good agreement. PMID:19529434

Phan Huy, Minh Châu; Laffont, Guillaume; Dewynter, Véronique; Ferdinand, Pierre; Labonté, Laurent; Pagnoux, Dominique; Roy, Philippe; Blanc, Wilfried; Dussardier, Bernard

2006-10-30

249

Influence of refractive index and molecular weight of alcohol agents on skin optical clearing effect  

NASA Astrophysics Data System (ADS)

In order to discuss the relative factors affecting the optical clearing effect of agents on skin tissues, six hydroxy-terminated and saturated alcohols with different refractive index and molecular weight were chosen as the optical clearing agents (OCAs). After being treated by different OCAs, the change of transmitted intensity of porcine skins in vitro was measured by single integrating sphere system. The results showed the optical clearing effects of six OCAs, i.e., glycerol, PEG400, PEG200, 1,3-propylene glycol, 1,4-butanediol and 1-butanol, arranged in the descending order. Based on the above results, the refractive index and molecular weight was further discussed. The optical clearing effect of alcohols has been deduced to have negative correlation with refractive index (r=-0.608), but no correlation with molecular weight (r= 0.008).

Mao, Zhongzhen; Zheng, Ying; Hu, Yating; Lu, Wei; Luo, Qingming; Zhu, Dan

2007-03-01

250

Refractive index sensing in aqueous environment using three different polymeric waveguide interferometers  

NASA Astrophysics Data System (ADS)

In this work, the performances of three developed polymer integrated optical sensors based on different waveguide configurations were evaluated for homogeneous refractive index (RI) sensing in aqueous environment. Young interferometer configuration with reference and sensing waveguide arms was utilized in sensor chips. Light from a laser source was end-fire coupled into the chips and interference pattern produced by the out coupled light was investigated. External fluidic pump was used to produce the analyte flow. The homogeneous bulk refractive index change was characterized by applying DI-water with varying glucose concentrations. With an interaction length of 1 cm a detection limit in the order of 10-5 ~ sub-10-6 refractive index unit (RIU) was determined. The sensing performances are compared among the sensors in terms of sensitivity, stability, multiparameter sensing ability, and fabrication and operation simplicity. The polymeric-inorganic composited rib waveguide configuration showed the highest performance and relatively simple fabrication process amongst the evaluated sensors.

Wang, Meng; Hiltunen, Jussi; Myllylä, Risto

2013-05-01

251

Index of refraction measurements and window corrections for PMMA under shock compression  

NASA Astrophysics Data System (ADS)

Symmetric plate impact experiments were performed to investigate the change in the refractive index of Polymethylmethacrylate (PMMA) under shock loading. Flyer and target geometries allowed the measurement of shock velocity, particle velocity, and refractive index in the shocked state, using a Het-V system (1550 nm). The change in refractive index of PMMA as a function of density is generally considered to be well described by the Gladstone-Dale relationship, meaning that the "apparent" velocity measured by a laser velocity interferometer is the "true" velocity, and hence there is no window correction. The results presented here demonstrate that the behaviour of PMMA deviates from an ideal Gladstone-Dale description, requiring a small velocity correction of order 1% at peak stresses up to 1.9 GPa. These results are consistent with literature values measured using a wavelength of 632.8 nm by [1].

Chapman, David James; Eakins, Daniel E.; Williamson, David Martin; Proud, William

2012-03-01

252

Tuning of refractive index of poly(vinyl alcohol): Effect of embedding Cu and Ag nanoparticles  

NASA Astrophysics Data System (ADS)

In this article, we have reported the results of our measurements, related to the tuning of the refractive index of the poly(vinyl alcohol) (PVA) polymer on embedding Cu and Ag nanoparticles at different concentrations. The size distribution and dispersion behaviour of embedded nanoparticles within PVA have been studied through transmission electron microscopy. A systematic increase in refractive index of PVA on increasing the concentration of embedded nanoparticles has been observed. These results have been tried to be explained using Bhar and Pinto model based on the Lorimar's theory for polymer composites. The values of refractive index of these nanocomposites have also been calculated using the Lorentz-Lorenz effective medium theory and found to be in close agreement with the experimental data. Nanoparticles embedded induced modifications in the structure of PVA have been revealed through FTIR spectroscopy.

Mahendia, Suman; Kumar Tomar, Anil; Goyal, Parveen K.; Kumar, Shyam

2013-02-01

253

Suppression of Air Refractive Index Variations in High-Resolution Interferometry  

PubMed Central

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

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

2011-01-01

254

Complex Refractive Index Determination Using Planar and Converging Beam Transfer Functions  

NASA Astrophysics Data System (ADS)

Terahertz time domain spectroscopy can help us to determine the complex refractive index of materials. To achieve this a theoretical model of the spectrometer has to be implemented; a usual method for refractive index determination is to fit a theoretically calculated transfer function to the experimental data. Material parameter extraction models based on transfer functions can be of varying complexity based on the requirements for accuracy and also the difficulty of factoring all experimental parameters. Here, we are going to show how algorithms based on transfer functions with different complexity can be setup. It will be described how a transfer function can be used to extract the refractive index of material and the key stages of the analysis, the fitting algorithm, and the need for phase unwrapping. Transfer functions of an increasing complexity will be shown, with and without the etalon term, using planar or converging beam.

Apostolopoulos, Vasilis; Daniell, Geoff; Chung, Aaron

255

Comparison of the accuracy of aerosol refractive index measurements from single particle and ensemble techniques.  

PubMed

The ability of two techniques, aerosol cavity ring down spectroscopy (A-CRDS) and optical tweezers, to retrieve the refractive index of atmospherically relevant aerosol was compared through analysis of supersaturated sodium nitrate at a range of relative humidities. Accumulation mode particles in the diameter range 300-600 nm were probed using A-CRDS, with optical tweezer measurements performed on coarse mode particles several micrometers in diameter. A correction for doubly charged particles was applied in the A-CRDS measurements. Both techniques were found to retrieve refractive indices in good agreement with previously published results from Tang and Munkelwitz, with a precision of ±0.0012 for the optical tweezers and ±0.02 for the A-CRDS technique. The coarse mode optical tweezer measurements agreed most closely with refractive index predictions made using a mass-weighted linear mixing rule. The uncertainty in the refractive index retrieved by the A-CRDS technique prevented discrimination between predictions using both mass-weighted and volume-weighted linear mixing rules. No efflorescence or kinetic limitations on water transport between the particle and the gas phase were observed at relative humidities down to 14%. The magnitude of the uncertainty in refractive index retrieved using the A-CRDS technique reflects the challenges in determining particle optical properties in the accumulation mode, where the extinction efficiency varies steeply with particle size. PMID:22856537

Mason, Bernard J; King, Simon-John; Miles, Rachael E H; Manfred, Katherine M; Rickards, Andrew M J; Kim, Jin; Reid, Jonathan P; Orr-Ewing, Andrew J

2012-08-23

256

Dynamic control over nanoparticle plasmon resonance through variation of refractive index  

NASA Astrophysics Data System (ADS)

In a semiconductor material it is possible to vary the index of refraction by exciting electron-hole pairs through a laser pulse. Generally the change in refractive index changes linearly with the carrier density and also increases with the lattice temperature. We present our results on the variation in index of refraction in the TiO2 shell of an Ag/TiO2 core-shell nanoparticle by exciting electron-hole pairs in TiO2 through a laser pulse. We performed bandstructure calculations using VASP to determine the variation of the optical dielectric tensor as a function of photon frequency. This change in refractive index not only affects the refraction of photons with frequency below bandgap, but also affects strongly the resonance peaks of the surface plasmons due to the Ag core. This effect can be used to dynamically control the plasmon resonance of a hybrid metal-semiconductor nanoparticle, for example for use in cancer therapy or nanoplasmonic circuits.

Paudel, Hari P.; Leuenberger, Michael N.

2011-03-01

257

Refractive index distribution and optical properties of the isolated human lens measured using magnetic resonance imaging (MRI)  

Microsoft Academic Search

Using a non-invasive MRI technique for measuring the refractive index distribution through the crystalline lens, refractive index maps were obtained through 20 intact isolated human lenses (7–82years). Focal length measurements, obtained by simulated light ray propagation through each index map were found to be in agreement with direct measurements performed on a scanning laser apparatus. With increasing age, the refractive

C. E. Jones; D. A. Atchison; R. Meder; J. M. Pope

2005-01-01

258

Precise determination of refractive-index changes in Ti-diffused LiNbO3 optical waveguides  

Microsoft Academic Search

A new method for determining refractive-index changes in Ti-diffused LiNbO3 optical waveguides is reported. The measurement process was as follows: (1) Diffusion profiles and Ti concentrations in LiNbO3 optical waveguides were measured by an x-ray microanalyzer. (2) Ti concentrations in the samples were converted into refractive-index changes using calibration curves which gave the relation between Ti concentrations and refractive-index changes.

Makoto Minakata; Shoichi Saito; Masashi Shibata; Shintaro Miyazawa

1978-01-01

259

Direct near-surface measurement of refractive index: extension of the Brewster-Pfund method to graded-index films  

NASA Astrophysics Data System (ADS)

As a complement to the standard m-line method, where an analytical curve is fitted to the measurements of waveguide modes and extrapolated to provide the refractive index in the zero-depth limit, we review our polarimetric approach to a direct-near surface measurement of graded-index films, and present its new and more straightforward version, which is applicable to existing samples without masking procedures prior to ion exchange.

Pereira, Marcelo B.; Horowitz, Flavio

2003-11-01

260

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

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

261

Measurement method for the refractive index of thick solid and liquid layers.  

PubMed

A simple method is proposed for the refractive index measurement of thick solid and liquid layers. In contrast to interferometric methods, no mirrors are used, and the experimental setup is undemanding and simple. The method is based on the variation of transmission caused by optical interference within the layer as a function of incidence angle. A new equation is derived for the positions of the interference extrema versus incidence angle. Scattering at the surfaces and within the sample, as well as weak absorption, do not play important roles. The method is illustrated by the refractive index measurements of sapphire, window glass, and water. PMID:19649048

Santi?, Branko; Gracin, Davor; Jurai?, Krunoslav

2009-08-01

262

Influence of humidity on refractive index of polymers for optical waveguide and its temperature dependence  

NASA Astrophysics Data System (ADS)

Humidity dependence of the refractive index of deuterated polymethylmethacylate (d-PMMA) is examined at a wavelength of 1.3 ?m using the return loss method. The refractive index of d-PMMA increases as humidity increases at room temperature, while it decreases as humidity increases at temperatures higher than 60 °C. This humidity dependence was ascribed to the counterbalance between moisture sorption and swelling. Some hydrophobic polymers, such as silicone resin and fluorinated epoxy resin were affected by humidity to a lesser degree than d-PMMA.

Watanabe, Toshio; Ooba, Naoki; Hida, Yasuhiro; Hikita, Makoto

1998-03-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

264

Theory of negative-refractive-index response of double-fishnet structures.  

PubMed

A theory is presented of the negative refractive index observed in the so-called double-fishnet structures. We find that the electrical response of these structures is dominated by the cutoff frequency of the hole waveguide whereas the resonant magnetic response is due to the excitation of gap surface plasmon polaritons propagating along the dielectric slab. Associated with this origin, we show how the negative refractive index in these metamaterials presents strong dispersion with the parallel momentum of the incident light. PMID:18851217

Mary, A; Rodrigo, Sergio G; Garcia-Vidal, F J; Martin-Moreno, L

2008-09-01

265

Temperature-dependent index of refraction of monoclinic Ga2O3 single crystal.  

PubMed

We present temperature-dependent refractive index along crystallographic b[010] and a direction perpendicular to (100)-plane for monoclinic phase (?) Ga(2)O(3) single crystal grown by the optical floating zone technique. The experimental results are consistent with the theoretical result of Litimein et al.1. Also, the Sellmeier equation for wavelengths in the range of 0.4-1.55 ?m is formulated at different temperatures in the range of 30-175 °C. The thermal coefficient of refractive index in the above specified range is ~10(-5)/°C. PMID:22086027

Bhaumik, Indranil; Bhatt, R; Ganesamoorthy, S; Saxena, A; Karnal, A K; Gupta, P K; Sinha, A K; Deb, S K

2011-11-01

266

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

PubMed

We report the first measurements of the index of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary parts 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 of (n-1) is in very good agreement with traditional measurements of this quantity. Finally, the real and imaginary parts of (n-1) and their ratio rho exhibit glory oscillations, in good agreement with calculations. PMID:17677948

Jacquey, M; Büchner, M; Trénec, G; Vigué, J

2007-06-15

267

Simultaneous measurement of group refractive index and thickness of optical samples using optical coherence tomography  

SciTech Connect

Optical coherence tomography (OCT), based on a Michelson interferometer and utilizing low coherence light as the optical source, is a novel technique for the noninvasive imaging of optical scattering media. A simple OCT scheme based on a 3x3 fiber coupler is presented for the simultaneous measurement of the refractive index and thickness of optical samples. The proposed system enables the refractive index and thickness to be determined without any prior knowledge of the sample parameters and is characterized by a simple and compact configuration, a straightforward measurement procedure, and a low cost. The feasibility of the proposed approach is demonstrated experimentally using BK7 and B270 optical glass samples.

Cheng, Hsu-Chih; Liu, Yi-Cheng

2010-02-10

268

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

269

Liquid core fibre Bragg grating based refractive index sensor formed by femtosecond assisted chemical etching technique  

NASA Astrophysics Data System (ADS)

We report the fabrication of a refractive index (RI) sensor based on a liquid core fibre Bragg grating (FBG). A micro-slot FBG was created in standard telecom optical fibre employing the tightly focused femtosecond laser inscription aided chemical etching. A micro-slot with dimensions of 5.74(h) × 125(w) × 1388.72(l) ?m was engraved across the whole fibre and along 1mm long FBG which gives advantage of a relatively robust liquid core waveguide. The device performed the refractive index sensitivity up to about 742.72 nm/RIU.

Saffari, P.; Yan, Z.; Zhou, K.; Zhang, L.; Bennion, I.

2011-05-01

270

Solution of transport equations in layered media with refractive index mismatch using the PN-method.  

PubMed

The PN-method is a spectral discretization technique used to obtain numerical solutions to the radiative transport equation. To the best of our knowledge, the PN-method has yet to be generalized to the case of refractive index mismatch in layered slabs used to numerically simulate skin. Our main contribution is the application of a collocation method that takes into account refractive index mismatch at layer interfaces. The stability, convergence, and accuracy of the method are established. Example calculations demonstrating the flexibility of the method are performed. PMID:19798392

Phillips, Kevin G; Jacques, Steven L

2009-10-01

271

Refractive-index profile and physical process determination in thick gratings in electrooptic crystals  

NASA Technical Reports Server (NTRS)

A method for determining the refractive index profile of thick phase gratings in linear electrooptic crystals is presented. This method also determines the effective photovoltaic electric field and the relative contributions of diffusion and drift during hologram recording. The method requires only a knowledge of the modulation ratio during hologram recording and the fundamental and the higher-order diffraction efficiencies of the grating. As an illustration of the method, the refractive index profile, the effective photovoltaic field, and the relative contributions of diffusion and drift are determined from experimental measurements for a lithium niobate holographic grating.

Su, S. F.; Gaylord, T. K.

1976-01-01

272

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

273

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

274

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

275

Measurement of refractive index variation of physiological analytes using differential-phase OCT  

NASA Astrophysics Data System (ADS)

We report results of a study using differential phase optical coherence tomography (DP-OCT) for measurement of variation of refractive index (n) vs. analyte concentration (C) in translucent solutions and turbid tissue phantoms. Variation of refractive index with analyte concentration (dn/dC) in aqueous solutions of glucose, calcium chloride, magnesium chloride, sodium chloride, potassium chloride, potassium bicarbonate, urea, bovine serum albumin, and bovine globulin was measured. Obtained results demonstrated: (1) dn/dC for glucose is significantly greater than that of other analytes in the physiological range; and (2) high sensitivity of DP-OCT method for measurement of analyte concentration.

Larin, Kirill V.; Akkin, Taner; Milner, Thomas E.; Dave, Digand P.; Motamedi, Massoud; Esenaliev, Rinat O.

2004-06-01

276

Method of refractive index, roughness and uniformity of silicon carbide layer deposited by plasma enhanced chemical vapour deposition method  

NASA Astrophysics Data System (ADS)

The silicon carbide layer was deposited on Si substrate by Plasma Enhanced Chemical Vapor Deposition method and it was shown its RFTIR spectrum is periodic in near and medium IR range by using this property refractive index of thin film was calculated. It was shown both deposition rate and uniformity of thin film were decreased by increasing substrate temperature. We also showed although the refractive index and deposition rate of SiC layer depend on the substrate temperature, and the roughness of surface was decreased but refractive index was increased by increasing substrate temperature It was shown the refractive index increases by annealing SiC thin film, at 900 °C.

Rostami, Ali; Shafiei, S. Yousef; Shafi-e-asl, Amir; Marami Iranaq, A. R.

2013-06-01

277

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

278

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

279

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

280

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

281

Design and calibration of low-cost fiber optic sensors for refractive index measurement of turbid liquids  

NASA Astrophysics Data System (ADS)

An optical fiber, stripped partially out of its cladding is used to sense refractive index of a liquid to a precision to fifth place of decimal. The dependence of the light output of the sensor on the refractive index of the test liquid is nonlinear. The light output of the sensor depends on the thickness to which the cladding is stripped. It shows both positive and negative slope with increasing refractive index of the test liquid. The slope of the plot of sensor output against liquid refractive index shows a change of sign at around the fiber refractive index. The sensor is unaffected by the presence of absorption and is insensitive to the chemical nature of the solute. The sensor is sensitive in the whole of the tested range of refractive indices 1.33 to 1.52. Experiments that show the significance of cladding modes in sensing are described.

Gupta-Bhaya, Pinaki; Ghosh, Anjan Kumar; Saxena, Vishal; John, Joseph

2006-10-01

282

Effects of sputtering through small apertures on the refractive index of niobium pentoxide films  

SciTech Connect

Niobium pentoxide (Nb/sub 2/O/sub 5/) can be reactively rf sputtered to produce high-index low-loss amorphous films for use as integrated optical (IO) components. Tight tolerances are required on refractive index, loss, scatter, and geometric form. Of particular interest to IO devices are thin-film Luneburg lenses which have been successfully employed on lithium niobate (LiNbO/sub 3/) based acousto-optic spectrum analyzers. To develop a particular lens configuration it is necessary to sputter through a circular aperture mask in contact with the LiNbO/sub 3/. Experimental evidence has shown that there is a significant drop in refractive index under fixed deposition conditions as the ratio of aperture diameter to mask thickness A/t is decreased. For an A/t ratio of 7.0 the index is 2.272 while an A/t ratio of 1.0 results in an index of 2.224. Increasing the power to the Nb target and bias sputtering have been successfully applied to raise the index. An increase in power from 70 to 400 W raised lens indices from 2.220 to 2.280. Bias sputtering similarly increases lens indices but distorted the lens profile. The mechanisms influencing refractive index change in amorphous Nb/sub 2/O/sub 5/ films sputtered under varying deposition conditions are discussed.

Hickernell, F.S.

1988-05-01

283

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

284

Negative refractive index metamaterials using only metallic cut wires.  

PubMed

We present, design and analyze a novel planar Left-Handed (LH) metamaterial at microwave frequencies. This metamaterial is composed of only metallic cut wires and is used under normal-to-plane incidence. Using Finite Element Method (FEM) based simulations and microwave experiments, we have investigated the material properties of the structure. Simultaneous negative values are observed for the permittivity epsilon and permeability mu by the inversion method from the transmission and reflection responses. A negative index n is verified in a bulk prism engineered by stacking several layers of the metamaterial. Our work demonstrates the feasibility of a LH metamaterial composed of only cut wires. PMID:19365456

Sellier, Alexandre; Burokur, Shah Nawaz; Kanté, Boubacar; de Lustrac, André

2009-04-13

285

Determination of ordinary refractive index profile for a planar waveguide by transmission spectrum analysis  

NASA Astrophysics Data System (ADS)

We introduce a new method to determine the ordinary refractive index profile of a planar waveguide on a crystal plate. The index profile of the planar waveguide can be numerically divided into multilayers; the transmission spectrum of the multilayer waveguide can be calculated and numerically analyzed to fit the measured transmission spectrum. We demonstrated this method on a proton exchanged planar waveguide in z-cut LiTaO3. We found that the ordinary refractive index profile of this waveguide can very well be described by a Fermi-Dirac function. The index profile evolution with proton exchange time and anneal time were obtained together with the diffusion coefficients for the proton exchange and anneal processes. We discovered that, for the proton exchange process in LiTaO3, there exists a surface diffusion phenomenon which has a much smaller diffusion coefficient than that of the bulk diffusion.

Chao, Shiuh; Chen, Yun-Chiao; Chen, Huai-Yi

1998-06-01

286

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

NASA Technical Reports Server (NTRS)

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

Khanna, R. K.; Zhao, Guizhi

1986-01-01

287

Reconstruction of fiber grating refractive-index profiles from complex bragg reflection spectra.  

PubMed

Reconstruction of the refractive-index profiles of fiber gratings from their complex Bragg reflection spectra is experimentally demonstrated. The amplitude and phase of the complex reflection spectrum were measured with a balanced Michelson interferometer. By integrating the coupled-mode equations, we built the relationship between the complex coupling coefficient and the complex reflection spectrum as an iterative algorithm for reconstructing the index profile. This method is expected to be useful for reconstructing the index profiles of fiber gratings with any apodization, chirp, or dc structures. An apodized chirped grating and a uniform grating with a depression of index modulation were used to demonstrate the technique. PMID:18323933

Huang, D W; Yang, C C

1999-07-20

288

Reconstruction of Fiber Grating Refractive-Index Profiles from Complex Bragg Reflection Spectra  

NASA Astrophysics Data System (ADS)

Reconstruction of the refractive-index profiles of fiber gratings from their complex Bragg reflection spectra is experimentally demonstrated. The amplitude and phase of the complex reflection spectrum were measured with a balanced Michelson interferometer. By integrating the coupled-mode equations, we built the relationship between the complex coupling coefficient and the complex reflection spectrum as an iterative algorithm for reconstructing the index profile. This method is expected to be useful for reconstructing the index profiles of fiber gratings with any apodization, chirp, or dc structures. An apodized chirped grating and a uniform grating with a depression of index modulation were used to demonstrate the technique.

Huang, Ding-Wei; Yang, Chih-Chung

1999-07-01

289

Simultaneous absorbance, fluorescence and refractive index (SAFRIN) detection for Micro LC  

Microsoft Academic Search

Absorbance, fluorescence and refractive index detection are simultaneously accomplished in a Micro LC system. A unique double eccentric-bend fused silica capillary is employed with axial illumination to achieve a long path length, multisensing flow cell. Two different optical sources, one that excites fluorescence through absorption and one that is not absorbed by eluting analytes, are imaged into the bends with

Ahmad A. Abbas; Dennis C. Shelly

1999-01-01

290

Design and experiment study of solution refractive index sensor based on TFBG-SPR  

NASA Astrophysics Data System (ADS)

The core and cladding modes exhibit different refractive index sensitivities, while temperature and stress sensitivities are approximately equal. Because of the characters of cladding mode, the solution refractive index(SRI) sensor is designed and studied. In order to increase the sensitivity of SRI sensor, 45nm thick gold film is deposited on the surface of cladding of TFBG to excite surface plasmon resonance(SPR). The quality and uniformity of gold surface were investigated with aid of a thermal field scanning electron microscopy and the effect is satisfactory. After that, the refractive index(RI) sensing characteristics of both bare and gold deposited TFBGs were studied by experiments of different concentration solutions of NaCl?MgCl2 and CaCl2 respectively. The result proved that the TFBG-SPR increase the RI sensitivity dramatically by 1.5 nm/RIU to 500 nm/RIU. And SRI of TFBG-SPR is 250 to 400 times larger than that of the bare-TFBG. The linear fittings of the center wavelength of cladding modes and SRI of bare and gold-coating deposited SPR sensor are good when refractive index is changed from 1.333 to 1.3941. Meanwhile, the influence of temperature on SPR was taken in consideration and compensated.

Jiang, Qi; Lv, Dandan

2013-08-01

291

The effect of refractive index on the friction coefficient of DLC coated polymer substrates  

Microsoft Academic Search

This paper describes the enhanced mechanical performance that can be achieved by the application of diamond-like carbon (DLC) coatings to polymer substrates. The polymers coated are silicone and polyethylene, and the effect on the friction coefficient is studied. Film adhesion is found to depend on the DLC film refractive index (n), whereas the friction is largely independent of n in

K. Donnelly; D. P. Dowling; M. L. McConnell; R. V. Flood

1999-01-01

292

The Combined Effect of Temperature and Humidity Fluctuations on Refractive Index  

Microsoft Academic Search

Depending on whether the radiation under consideration is acoustic, visible or microwave, either temperature or humidity fluctuations are ordinarily assumed to be an insignificant source of refractive index fluctuations. For applications in the atmospheric surface layer or in a free convection layer, the value of the local Bowen ratio , which is the ratio of sensible to latent heat flux

Marvin L. Wesely

1976-01-01

293

Transmission line models for negative refractive index media and associated implementations without excess resonators  

Microsoft Academic Search

Recently, three-dimensional composite periodic media comprising split-ring resonators (SRR) and thin wires have been shown to exhibit a negative refractive index in the frequency range around the SRR resonance. In this letter, we propose transmission line models for studying and interpreting the electromagnetic propagation behavior of such materials. Based on these equivalent transmission line models, we show that by periodically

George V. Eleftheriades; Omar Siddiqui; Ashwin K. Iyer

2003-01-01

294

Dispersion-equation coefficients for the refractive index and birefringence of calcite and quartz crystals  

Microsoft Academic Search

The refractive index, birefringence and their dispersions are analyzed accurately in a physically meaningful model of a dispersion equation having only five coefficients for the calcite and quartz crystals. This dispersion equation is based on the average electronic absorption gap in the UV region and the effective lattice resonance absorption gap in the IR region. The five coefficients of the

Gorachand Ghosh

1999-01-01

295

Protein diffusion in agarose hydrogel in situ measured by improved refractive index method  

Microsoft Academic Search

The accurate knowledge of the diffusion behavior of protein within biomimetic hydrogel matrix at body temperature has a great implication for the design of efficient controlled release protein-base drug delivery devices. In this paper, we improved our previous in situ refractive index method with great temperature-controlled capability. For the first time, this newly improved method was employed to study the

Songmiao Liang; Jian Xu; Lihui Weng; Hongjun Dai; Xiaoli Zhang; Lina Zhang

2006-01-01

296

Simultaneous measurement of liquid absorbance and refractive index using a compact optofluidic probe.  

PubMed

We present a novel optical technique for simultaneously measuring the absorbance and the refractive index of a thin film using an infrared optofluidic probe. Experiments were carried on two different liquids and the results agree with the bibliographical data. The ultimate goal is to achieve a multi-functional micro-optical device for analytical applications. PMID:23649405

Malak, Maurine; Marty, Frédéric; Bourouina, Tarik; Angelescu, Dan

2013-07-21

297

Sensitivity of photonic crystal fiber grating sensors: biosensing, refractive index, strain, and temperature sensing  

Microsoft Academic Search

We study the sensitivity of fiber grating sensors in the applications of strain, temperature, internal label-free biosensing, and internal refractive index sensing. It is shown that optical dispersion plays a central role in determining the sensitivity, and the dispersion may enhance or suppress sensitivity as well as change the sign of the resonant wavelength shifts. We propose a quality factor,

Lars Rindorf; Ole Bang

2008-01-01

298

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.

2014-05-01

299

Real and imaginary index-of-refraction measurements for RP-1 rocket fuel  

NASA Astrophysics Data System (ADS)

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, critical angle, Mueller matrix, and Michelson interferometer techniques. Reflectance measurements are used to obtain nr at a wavelength of 0.193 micrometers . Critical angle method is used to determine nr at 0.5145 micrometers and 0.532 micrometers . The real part of the refractive index is obtained from Snell's law by measuring the critical angle. The real part of the refractive index at 1.064 micrometers is derived based on elements of the Mueller matrix. Specular measurements were performed using a TMA scatterometer to obtain the Mueller matrix. A Michelson interferometer is used to determine nr at 10.5915 micrometers .

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

1994-03-01

300

Photoinduced refractive index change and absorption bleaching in poly(methylphenylsilane) under varied atmospheres.  

SciTech Connect

Polysilane materials exhibit large photo-induced refractive index changes under low incident optical fluences, making them attractive candidates for applications in which rapid patterning of photonic device structures is desired immediately prior to their use. This agile fabrication strategy for integrated photonics inherently requires that optical exposure, and associated material response, occurs in nonlaboratory environments, motivating the study of environmental conditions on the photoinduced response of the material. The present work examines the impact of atmosphere on the photosensitive response of poly(methylphenylsilane) (PMPS) thin films in terms of both photoinduced absorption change and refractive index modification. Material was subjected to UV light exposure resonant with the lowest energy optical transition associated with the conjugated Si-Si backbone. Exposures were performed in both aerobic and anaerobic atmospheres (oxygen, air, nitrogen, and 5% H{sub 2}/95% N{sub 2}). The results clearly demonstrate that the photosensitive response of this model polysilane material was dramatically affected by local environment, exhibiting a photoinduced refractive index change, when exposed under an oxygen containing atmosphere, that was twice that observed under anaerobic conditions. This effect is discussed in terms of photo-oxidation processes within the polysilane structure and in the context of the need for predictable photosensitive refractive index change in varied photoimprinting environments.

Potter, Barrett George, Jr. (University of Arizona, Tucson, AZ); Simmons-Potter, Kelly (University of Arizona, Tucson, AZ); Chandra, Haripin (University of Arizona, Tucson, AZ); Thomes, William Joseph, Jr.; Jamison, Gregory Marks

2005-06-01

301

Measurement of thermally induced changes in the refractive index of glass caused by laser processing  

Microsoft Academic Search

The effects of CO2 laser heating of pure fused silica are investigated. Studies show that the laser heating process causes a small volume of glass to be left in an altered microstructural state. To measure the refractive index of this altered region, a process was developed to create a thin film of altered glass. Samples were measured with a prism

James Sullivan; Jian Zhao; Ted D. Bennett

2005-01-01

302

Simultaneous determination of bubble diameter and relative refractive index using glare circles  

Microsoft Academic Search

In the shadow image of a spherical gas bubble, high intensity rings are visible, i.e., glare circles. These can be used to obtain a more precise estimate of the bubble diameter than can be obtained from the shadow contour. The glare circle diameter can also be used to determine the relative refractive index by comparing it with the shadow diameter.

S. Dehaeck; J. P. A. J. van Beeck

2007-01-01

303

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

Microsoft Academic Search

The refractive index of a liquid carries important information about its physical properties, including concentration and density, thus making it possible to determine and monitor the composition of the solution. This is important in fundamental research, chemical analysis and medical diagnostics, as well as in the processing and manufacturing of various substances. The authors have developed a compact and adaptable

O. Vilitis; P. Shipkovs; D. Merkulov

2009-01-01

304

[Estimation of the size of bilayer liposome by optical density and refractive index].  

PubMed

A simple method for estimating a mean particles size in a suspension is suggested on the basis of an empirical correlation of a liposome size found by the optical shift method and on optic properties of the suspension. For liposome size characteristics only two parameters: optical density and refraction index increment are measured. PMID:6845444

Levchuk, Iu N; Volovik, Z N; Shcherbatskaia, N V

1983-01-01

305

Determination of soot temperature, volume fraction and refractive index from flame emission spectrometry  

Microsoft Academic Search

An inversion scheme based on tomographic reconstruction of flame emission spectra has been developed for nonintrusive characterization of soot temperature and volume fraction fields within an optically thin axisymmetric flame by extracting characteristic information on soot refractive index from spectral gradients of emission spectra. Its performance is assessed by providing input data obtained from intensities simulated by a direct code

I??l Ayranc?; Rodolphe Vaillon; Nevin Selçuk; Frédéric André; Dany Escudié

2007-01-01

306

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

Microsoft Academic Search

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

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

2007-01-01

307

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

SciTech Connect

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

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

2010-08-23

308

Thermally induced refractive index gradients in a dye-laser cell  

NASA Astrophysics Data System (ADS)

The program GABI calculates refractive index gradients generated in a dye solution, flowing in a planar cell, and pumped by a repetitively pulsed copper vapor laser beam. The calculation results serve for design evaluation and selection of optimal pump geometry, dye solvent and dye solution flow velocity.

Burshtein, Z.; Levron, D.; Bialolenker, G.

1988-11-01

309

Hybrid long period fiber grating for measuring refractive index and pressure in downhole application  

Microsoft Academic Search

A hybrid long period fiber grating (HLPFG) sensor was utilized for sensing the refractive index and pressure for downhole applications. The HLPFG is fabricated by fattening and tapering on a single mode fiber, utilizing a standard fusion splicing and a CO2 laser, respectively. The limit of detection (LOD) of the HLPFG for the RI measurement in the range from 1.3150

J. Sadeghi; M. I. Zibaii; M. Kheiri; A. Ahmadlou; H. Latifi; M. H. Ghezelaiagh

2011-01-01

310

Laser-Induced Refractive-Index Gratings in Eu-Doped Glasses.  

National Technical Information Service (NTIS)

Four-wave mixing techniques were used to establish and probe refractive-index gratings in Eu(3+)-doped silicate and phosphate glasses. When the Eu(3+) ions are resonantly excited, superimposed transient and permanent gratings are formed. The former are ch...

F. M. Durville E. G. Behrens R. C. Powell

1986-01-01

311

Refractive Index of Ge Nanocrystals Embedded in a GeOx Matrix  

NASA Astrophysics Data System (ADS)

We investigated the optical properties of the Ge nanocrystal embedded in a GeOx matrix by spectroscopic ellipsometry. Substoichiometric films were thermally annealed to obtain embedded Ge nanocrystals. Ge nanocrystal formation is supported by XRD, Raman, and TEM studies. The refractive index increases from 1.959 for as-deposited sample to 2.167 forsample annealed at 600 °C.

Vijayarangamuthu, K.; Singh, Chaman; Rath, Shyama

2011-07-01

312

Conjugated gammadion chiral metamaterial with uniaxial optical activity and negative refractive index  

NASA Astrophysics Data System (ADS)

We demonstrate numerically and experimentally a conjugated gammadion chiral metamaterial that uniaxially exhibits huge optical activity and circular dichroism, and gives a negative refractive index. This chiral design provides smaller unit cell size and larger chirality compared with other published planar designs. Experiments are performed at GHz frequencies (around 6 GHz) and are in good agreement with the numerical simulations.

Zhao, R.; Zhang, L.; Zhou, J.; Koschny, Th.; Soukoulis, C. M.

2011-01-01

313

Determination of Optical Waveguide Refractive-Index Profiles with the Inverse Analytic Transfer Matrix Method  

Microsoft Academic Search

In this paper, we present an inverse analytic transfer matrix (IATM) method to predict the refractive index profiles from\\u000a the measurement of mode indices based on the analytic transfer matrix (ATM) method, which can exactly determine the modal\\u000a characteristics of a planar optical waveguide with arbitrary index profiles. IATM method has been proved to be universally\\u000a reliable not only in

Y. Ding; Z. Q. Cao; Q. S. Shen

2004-01-01

314

Magnetic Response and Negative Refractive Index of Metamaterials  

SciTech Connect

We study the scaling of negative magnetic response of the SRR from microwave to upper THz frequencies. We show, that the linear scaling breaks down for SRR sizes below the order of 1 {micro}m. This breakdown is due to the contribution of the finite electron mass to the inductance of the effective LC oscillator. While at microwave frequencies metals can be treated as near-perfect conductors, close to optical frequencies they rather constitute lossy negative dielectrics. We also study the scaling of the losses in SRR as well as the higher order excitations or plasmon modes and their magnetic response. We discuss the non-resonant diamagnetic response of the SRR and the corresponding corrections to the shape of the frequency dependent effective permeability of the metamaterial. We discuss the connection of recently suggested alternative negative index metamaterial designs in a unified picture.

Koschny, Th.; Zhou, J.; Soukoulis, C.M.

2007-05-04

315

High-refractive-index gratings for spectroscopic and laser applications  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

316

Determination of the refractive index of microparticles by utilizing light dispersion properties of the particle and an immersion liquid.  

PubMed

The knowledge of the refractive index of a particle is important in sensing and imaging applications, e.g., in biology, medicine and process industry. The refractive index of tiny solid particles such as microsize particles can be determined by the so-called liquid immersion technique. This study deals with three different types of interrogation methods to get the refractive index of a particle in a liquid matrix. These methods utilize thermo-optical properties and wavelength-dependent refractive index of the particle and the immersion liquids, as well as, the classical method using a set of in advance prepared set of immersion liquids with different refractive indices. The emphasis is on a method to get especially the wavelength-dependent refractive index of microparticles and exploiting different wavelength-dependences of immersion liquid and a solid particle because identification of a particle is more reliable if the refractive index of the particle is known at several wavelengths. In this study glycerol-water mixtures served as immersion liquids to obtain the refractive index of CaF2 at several discrete wavelengths in the spectral range 200-500 nm. The idea is to find the maximum value of light transmission of suspension by scanning the wavelength of a commercial spectrophotometer. The light dispersion-based method is suggested as a relatively easy, economic and fast method to determine the refractive index of a particle by a spectrophotometer at several wavelengths of light. The accuracy of the detection of the refractive index is suggested to be better than ± 0.005 refractive index units. PMID:24054563

Niskanen, I; Räty, J; Peiponen, K E

2013-10-15

317

Dynamics of pump-induced refractive index changes in single-mode Yb-doped optical fibers.  

PubMed

We quantify the refractive index changes (RIC) in single-mode ytterbium-doped optical fibers induced by optical pulses at 980 nm and, for the first time, report details of the effect dynamics. The RIC dynamics is shown to follow that of the population of the excited/unexcited ion states with a factor proportional to their polarizability difference (PD). The absolute PD value is evaluated in the spectral range of 1460-1620 nm for different fiber samples and is found to be independent on the fiber geometry and on the ion concentration. The PD dispersion profile indicates to a predominant far-resonance UV rather than near-resonant IR transitions contribution to the RIC. PMID:18711503

Fotiadi, Andrei A; Antipov, Oleg L; Mégret, Patrice

2008-08-18

318

Simultaneous measurement of the thickness profile and refractive index distribution of silicon wafers  

NASA Astrophysics Data System (ADS)

We describe a method to simultaneously measure both thickness profile and refractive index distribution of a silicon wafer based on a lateral scanning of the wafer itself. By using dispersive interferometer principle based on a broadband source, which is a femtosecond pulse laser with 100 nm spectral bandwidth, both thickness profile and refractive index distribution can be measured at the same time using a single scanning operation along a lateral direction. The proposed measurement system was tested using an approximately 90 mm range with a 0.2 mm step along the center-line, except for the rim area in a ?100 silicon wafer. As a result, the thickness profile was determined to have a wedge-like shape with an approximately 2 ?m difference at an averaged thickness of 478.03 ?m. Also, the mean value of the refractive index distribution was 3.603, with an rms value of about 0.001. In addition, the measurement uncertainty of the thickness profile was evaluated by considering two uncertainty components that are related to the scanning operation, like the yaw motion of the motorized stage and the long-term stability of an optical path difference in an air path. The measurement reliability of both the thickness profile and refractive index distribution can be increased through several methods such as an analysis of the correlation between the thickness profile and the refractive index distribution and a comparative measurement using a contact-type method; these potential methods are the subject of our future work.

Park, Jungjae; Jin, Jonghan; Kim, Jae Wan; Kang, Chu-Shik; Kim, Jong-Ahn

2013-06-01

319

Refractive Index of ZnS, ZnSe, and ZnTe and Its Wavelength and Temperature Derivatives.  

National Technical Information Service (NTIS)

Refractive index data of ZnS, ZnSe, and ZnTe were searched, compiled, and analyzed. Recommended values of refractive index for the transparent spectral region were generated in the ranges 0.5-14 micrometers and 93-1000 K for ZnS, 0.55-18 micrometers and 9...

H. H. Li

1984-01-01

320

Determination of index of refraction and size of supermicrometer particles from light scattering measurements at two angles  

Microsoft Academic Search

A twin angle optical particle counter (TAOPC) that measures forward scattering at 40° and 74° was developed to determine the index of refraction of atmospheric particles. An error analysis indicates that measurement uncertainties for size at 40° are between 4 and 10% for particles >1.5 ?m and between 5 and 15% at 74°. For the index of refraction determination, the

Trude Eidhammer; Derek C. Montague; Terry Deshler

2008-01-01

321

Determination of index of refraction and size of supermicrometer particles from light scattering measurements at two angles  

Microsoft Academic Search

A twin angle optical particle counter (TAOPC) that measures forward scattering at 40° and 74° was developed to determine the index of refraction of atmospheric particles. An error analysis indicates that measurement uncertainties for size at 40° are between 4 and 10% for particles >1.5 mum and between 5 and 15% at 74°. For the index of refraction determination, the

Trude Eidhammer; Derek C. Montague; Terry Deshler

2008-01-01

322

Refractive-index measurement based on the effects of total internal reflection and the uses of heterodyne interferometry.  

PubMed

A new method for measuring the refractive index is presented. First, the phase difference between s and p polarizations that is due to the total internal reflection is measured by heterodyne interferometry. Then, substituting this phase difference into the Fresnel equations, we can obtain the refractive index of the test medium. PMID:18253295

Chiu, M H; Lee, J Y; Su, D C

1997-05-01

323

Linear and nonlinear refractive index of As-Se-Ge and Bi doped As-Se-Ge thin films  

NASA Astrophysics Data System (ADS)

The present work reports the linear and nonlinear refractive index for (As2Se3)90Ge10 and [(As2Se3)90Ge10]95Bi5 thin films. The formulation proposed by Fournier and Snitzer has been used to predict the nonlinear behavior of refractive index. The linear refractive index and Wemple-DiDomenico parameters were used for the determination of nonlinear refractive index in the wavelength region 0.4 to 1.5 ?m. Linear refractive index has been determined using the well known Swanepoel method. This is observed that nonlinear refractive index increases linearly with increasing linear refractive index. With Bi addition this has been found that nonlinear refractive index increases by 2.4 times, while on comparing with pure and doped silica glasses results are 2-3 orders higher. Density and molar volume has also been calculated. The obtained results may lead to yield more sensitive optical limiting devices and these glasses may be used as an optical material for high speed communication fibers.

Sharma, Pankaj; Katyal, S. C.

2010-06-01

324

The Relation of the Refractive Index of Evaporated and Condensed Milk Serum to the Total Solids Content  

Microsoft Academic Search

The refractive index of milk serum has been used primarily for the detec- tion of added water in milk. Since the results of this determination are influenced directly by the soluble components it is logical to expect a definite relationship to exist between the total solids and the refractive index of the serum. Some investigators have shown that a definite

S. G. Menefee; O. R. Overman

1939-01-01

325

Saturation of the nonlinear refractive index in atomic gases  

NASA Astrophysics Data System (ADS)

Motivated by the ongoing controversy over the origin of the nonlinear index saturation and subsequent intensity clamping in femtosecond filaments, we study the atomic nonlinear polarization induced by high-intensity ultrashort laser pulses in hydrogen by numerically solving the time-dependent Schrödinger equation. Special emphasis is given to the efficient modeling of the nonlinear polarization at a central laser frequency corresponding to a wavelength of 800 nm. Here, the recently proposed model of the higher-order Kerr effect (HOKE) and two versions of the standard model for femtosecond filamentation, including either a multiphoton or tunnel ionization rate, are compared. We find that around the clamping intensity the instantaneous HOKE model does not reproduce the temporal structure of the nonlinear response obtained from the quantum-mechanical results. In contrast, the noninstantaneous charge contributions included in the standard models ensure a reasonable quantitative agreement. Therefore, the physical origin for the observed saturation of the overall electron response is confirmed to mainly result from contributions of free or nearly-free electrons.

Köhler, Christian; Guichard, Roland; Lorin, Emmanuel; Chelkowski, Szczepan; Bandrauk, André D.; Bergé, Luc; Skupin, Stefan

2013-04-01

326

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

327

In situ determination of refractive index and size of Bacillus spores by light transmission.  

PubMed

Light-extinction measurements in the wavelength range of 400 to 1000 nm are performed in situ on Bacillus subtilis endospores during heat-shock-induced activation. Simultaneous information on particle size and refractive indices during activation is calculated from the transmission spectra by use of the Gaussian ray approximation of anomalous diffraction theory. During activation the refractive index of the core decreases from 1.51 to 1.39, and the size increases from 0.38 to 0.6 microm. PMID:15791985

Katz, A; Alimova, Alexandra; Xu, M; Gottlieb, Paul; Rudolph, Elizabeth; Steiner, J C; Alfano, R R

2005-03-15

328

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

329

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

330

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 10×50 nm 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

331

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

NASA Astrophysics Data System (ADS)

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

Heading, J.

1989-10-01

332

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

333

A numerical method for determining refractive index of a glass sample from its implicit transcendental function  

NASA Astrophysics Data System (ADS)

The refractive index of a glass sample was determined from an implicit function of its optical path within the sample arm of a Michelson interferometer. On rotation of the sample from normal incidence, the light beam suffers increasing refraction, causing the optical path for air to decrease whilst that for the glass sample increases. This is observed as a shift in the number of fringes, which were captured and counted in real time on a computer, as rotation proceeded. The angle of rotation and the fringe shift were entered into an implicit function of optical path versus refractive index written to an Excel worksheet. A refractive index matching the wavelength of the He-Ne laser light source was read-off to three decimal places. A new source of uncertainty has been identified, misalignment on a micrometer scale of the laser normal to the sample surface. Whilst driving the sample to find normal incidence a finite angular region of insensitivity (dead space) occurs due to misalignment of the laser normal to the sample surface by a few micrometers. A linearization technique was employed to compensate for this offset and hence reduce its uncertainty contribution.

Ince, R.; S?n?r, E.; Feeney, M.; Yükselici, M. H.; Ince, A. T.

2008-07-01

334

Fabrication of polymer waveguides and spot size converters by UV induced refractive index modification  

NASA Astrophysics Data System (ADS)

Generalization of optical communication promotes fabrication of low cost integrated waveguide components. Polymer waveguides are attractive because they are very simple to process and are promising for low cost devices. Up to date, several methods are used to make single mode guides in polymer films. Traditionally, they require multi-step processes involving photolithography, etching and annealing. The UV induced modification of the dielectrics property of polymers is a useful technique for low cost realization of integrated optical circuits and can enable a direct writing process. This paper reports a demonstration of photo-printed waveguides in an intrinsically photosensitive polymer film. In this polymer (PVCi: PolyVinylCinnamate), local UV irradiation yields a lowering of refractive index even at telecom wavelengths (1300 and 1550 nm). We show significant achievement concerning the index contrasts up to 3x10-2 at 1550 nm. The more the refractive index contrast between the core and cladding increases, the more the guide size and curvature can be reduced, allowing the manufacture of smaller photonic devices. However miniaturization of optical planar waveguides in integrated devices increases the coupling losses from and to single-mode optical fibers. Simulations and experimental demonstrations with PVCi photosensitive waveguides also show the potential of photo-printing process to make efficient index mode converters between small planar waveguides and single-mode fibers. The process uses the post-irradiation of the guide by an UV source to gradually decrease the refractive index from the guide to the fibre.

Hardy, Isabelle; Grosso, Philippe; Bosc, Dominique

2005-06-01

335

Fiber-Laser-Based Sensor for Measuring Refractive Index and Solute Concentration of Aqueous Solutions  

NASA Astrophysics Data System (ADS)

We report a novel-principle fiber-laser intra-cavity sensor for measuring refractive index and solute concentration of aqueous solutions. The sensor operation is based on a variation of the laser oscillation relaxation frequency (RF, the measured parameter), sensitive to the intra-cavity loss. As the loss includes the reflection coefficient on the frontier aqueous solution-silica fiber cleaved cut, being the laser output coupler and simultaneously the sensor head, the RF becomes affected by the changes in refractive index of the aqueous solution; in turn, because the solution index is proportional to the solute concentration in water, the RF becomes also a function of the latter. The sensor capacity is demonstrated on the example of measurements of sugar concentration in water. A modeling of the sensor operation is presented, allowing its performance optimization.

Arellano-Sotelo, Héctor; Barmenkov, Yuri O.; Kir'yanov, Alexander V.

2008-10-01

336

Temperature and refractive index measurements using long-period fiber gratings fabricated by femtosecond laser  

NASA Astrophysics Data System (ADS)

Long period fiber gratings (LPFGs) with different periods in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs and the repetition rate of 250 kHz at a center wavelength of 800 nm in air. Comparative with bare LPFG in temperature sensor, LPFG had been encapsulated using large coefficient of thermal expansion of epoxy polymer and Aluminum to enhance the temperature sensitivity. The results showed that the temperature sensitivity of encapsulated LPFG was 2 times than that of bare LPFG. In addition, we also researched the relationship between resonant wavelength and surrounding refractive index (SRI) when LPFG immersed in refractive index of solution of different index at 20 degree Celsius.

Yu, Yongqin; Zheng, Jiarong; Yi, Kai; Ruan, Shuangchen; Du, Chenlin; Huang, Jianhui; Zhong, Wansheng

2011-11-01

337

Refractive index control in bicomponent polymer films for integrated thermo-optical applications  

NASA Astrophysics Data System (ADS)

Optical properties of transparent polymer thin films, produced by spin-coating on silicon and constituted of polycarbonate (PC), poly(methyl methacrylate) (PMMA), and PC/PMMA, were investigated with regard to integrated thermo-optical (TO) device applications. Refractive index dependences on wavelength, temperature, and film composition were measured by spectroscopic ellipsometry with a dedicated autocontrolled heater setup, in the ranges of 400 to 800 nm, 25 to 85 °C and 0 to 100 wt % PC, respectively, with determination of Cauchy and Lorentz-Lorenz parameters. Within these intervals, thermomechanical compatibility and pronounced index contrast of around 0.12 between PC and PMMA, as well as their TO coefficients one order of magnitude higher than that of silica, allow convenient tailoring for specific TO requirements. In addition, wide-range fine-tuning of refractive index variation is found to be facilitated by the weak dependence of isothermal dispersion curves and TO coefficients on film composition.

Soave, Paulo Azevedo; Dau, Ronaldo André Ferreira; Becker, Márcia Regina; Pereira, Marcelo Barbalho; Horowitz, Flavio

2009-12-01

338

Controlled refractive index of photosensitive polymer: towards photo-induced waveguide for near infrared wavelengths  

NASA Astrophysics Data System (ADS)

Photo-writing process of polymer optical waveguides can offer advantages to make easier connection fiber guide, and noticeably simplifies the fabrication procedure. In order to carry out a photo-writing technique, we choose a photosensitive polymer. Thus, under far UV irradiation, polyvinylcinnamate (PVCi) undergoes a change in its absorption, yielding a refractive index variation. This work presents the first results of relationship between the bleaching of the UV band and the refractive index change in the area of optical telecommunication spectrum. By the way, it is shown that the index contrast obtained by controlling the UV source, can be improved, in order to make suitable this process for printing integrated optical waveguides.

Assa??d, Imane; Hardy, Isabelle; Bosc, Dominique

2002-12-01

339

Microchanneled chirped fibre Bragg gratings for simultaneous refractive index and temperature measurements  

NASA Astrophysics Data System (ADS)

We report here the fabrication, charaterisation and refractive index sensing of two microchanneled chirped fiber Bragg gratings (MCFBGs) with different channel sizes (~550?m and ~1000?m). The chirped grating structures were UV-inscribed in optical fibre and the microchannels were created in the middle of the CFBGs by femtosecond (fs) laser assisted chemical etching method. The creation of microchannels in the CFBG structures gives an access to the external index liquid, thus inducing refractive index (RI) sensitivity to the structure. In comparison with previously reported FBG based RI sensors, for which the cladding layers usually were removed, the MCFBGs represent a more ideal solution for robust devices as the microchannel will not degrade the structure strength. The two MCFBGs were spectrally charaterised for their RI and temperature responses and both gratings exhibited unique thermal and RI sensitivities, which may be utilised for implementation of bio-chemical sensors with capability to eliminate temperature crosssensitivity.

Saffari, Pouneh; Fu, Hongyan; Zhou, Kaiming; Zhang, Lin; Bennion, Ian

2009-05-01

340

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

341

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

342

On the mechanism of photoinduced refractive index changes in phosphosilicate glass  

SciTech Connect

The photoinduced growth of the refractive index of phosphosilicate glass during Bragg grating inscription and the thermal decay of the grating have a number of unusual features. The observed index variations are interpreted in terms of a new model for photoinduced glass network rearrangement. The model assumes the formation of photoinduced voids (nanopores) in the glass network near point defects. The nanopores may migrate through the network via bond switching when the network is in a 'soft' state. The photoinduced variations in network density lead to index variations. (fibres)

Larionov, Yu V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Sokolov, V O; Plotnichenko, V G [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation)

2010-05-26

343

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

NASA Astrophysics Data System (ADS)

The planar waveguides have been fabricated in z-cut beta barium metaborate crystals by 2.8 MeV Si + ion implantation with doses of 1 × 10 15 and 3 × 10 15 ions/cm 2 at room temperature. The waveguides were characterized by the prism-coupling method. The refractive index profiles were reconstructed using reflectivity calculation method. It is found that relatively large positive changes of extraordinary refractive indices happen in the guiding regions, and the negative changes of ordinary refractive indices happen at the end of the track. TRIM'98 (transport of ions in matter) code was used to simulate the damage profile in ?-BBO by 2.8 MeV Si + ion implantation.

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

2004-12-01

344

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

345

Influence of the accuracy in index of refraction matching on fluid flow measurements  

NASA Astrophysics Data System (ADS)

Fluid flow imaging through curved surfaces suffers from optical distortion caused by the mismatch in the refractive indices of the fluid and the solid surface, leading to errors in velocity measurements and the resulting estimates of wall shear stress. Examples include imaging of flow through porous media and in-vitro studies of biological flow problems. A common approach for minimizing optical distortions is to adjust the refractive index of the fluid to closely match that of the solid. In this study we investigate how the accuracy in the index of refractive matching influences the image distortion and, in particular, the measurement accuracy of wall shear stress, a critical property in biofluid dynamics. A ray-tracing approach is used to simulate the optical distortion and is validated against experiments in a simple geometry, i.e. imaging of a liquid flow inside a cylindrical tube. Ray-tracing is implemented through an in-house code for simple geometries and the results are compared with simulations using a more complete (free) software that is already available online and can deal with complex geometries. Results show that a slight mismatch in the indices of refraction, as small as one part in a thousand, can lead to a significant error in the estimate of wall shear stress.

Durgesh, Vibhav; Koochesfahani, Manoochehr; Tong, Yiying

2008-11-01

346

Refractive index and hygroscopic stability of AlxGa1-xAs native oxides  

NASA Astrophysics Data System (ADS)

We present prism coupling measurements on AlxGa1-xAs native oxides showing the dependence of refractive index on composition (0.3<=x<=0.97), oxidation temperature (400<=T<=500), and carrier gas purity. Index values range from n=1.490 (x=0.9, 400 °C) to 1.707 (x=0.3, 500 °C). The oxides are shown to adsorb moisture, increasing their index by up to 0.10 (7%). Native oxides of AlxGa1-xAs (x<=0.5) have index values up to 0.27 higher and are less hygroscopic when prepared with a small amount of O2 in the N2+H2O process gas. The higher index values are attributed to a transition from a hydroxide to a denser (AlxGa1-x)2O3 oxide phase.

Hall, D. C.; Wu, H.; Kou, L.; Luo, Y.; Epstein, R. J.; Blum, O.; Hou, H.

1999-08-01

347

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

348

Measurement of the thermal contribution to the nonlinear refractive index of air at 1064 nm  

SciTech Connect

The thermal contribution to the nonlinear refractive index of air at 1.064 {mu}m was measured with a high-finesse Fabry-Perot cavity and a 500-mW cw laser beam. At room temperature and pressure, the nonlinear refractive-index coefficient of air was found to be n{sub 2}{sup (} {sup th)}=(-1.9{+-}0.2)x10{sup -14} cm{sup 2}/W for a beam waist radius of 0.23 mm and was found to be independent of the relative humidity. The thermal nonlinearities of N{sub 2} , O{sub 2} , and CO{sub 2} were also measured, and it was found that the dominant contribution to air is its O{sub 2} content. (c) 2000 Optical Society of America.

Bentley, Sean J.; Boyd, Robert W.; Butler, William E.; Melissinos, Adrian C.

2000-08-15

349

Laser direct writing of high-refractive-index polymer/TiO2 nanocomposites  

NASA Astrophysics Data System (ADS)

This work reports the preparation of polymer/TiO2 nanocomposite by adding TiO2 nanoparticles to the polymer matrices. TiO2 nanoparticles can be effectively dispersed into the polymer. The refractive index of the nanocomposites can be tuned by increasing the concentration of TiO2 nanoparticles. The prepared samples exhibit excellent optical transparency in the Vis-NIR region, i.e. at two-photon polymerization (TPP) processing wavelength, and can be used to write threedimensional structures by means of TPP. Structures with high refractive index have been produced with the novel ultrahigh resolution technology based on TPP processing of polymer/TiO2 nanocomposites.

Guo, Qingchuan; Ghadiri, Reza; Xiao, Shizhou; Esen, Cemal; Medenbach, Olaf; Ostendorf, Andreas

2012-02-01

350

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

351

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

NASA Astrophysics Data System (ADS)

Low refractive index polymers are used as cladding materials for high numerical aperture (NA) fibers. Since transparent fluoro polymers are ideal for this application, they have been used over many years. However, some fluoro chemicals face an issue related to perfluoro octanoic acid (PFOA) which is caused by its longtime persistence in the environment and human body. In this research, non-PFOA type UV curable fluoro resins suitable for cladding were developed with novel materials. The cured films showed high transparency, good adhesion to glass and low refractive index of 1.359 and 1.386 at 850 nm. Optical fibers prepared with those cladding showed almost equivalent attenuation to a fiber with commercially available material.

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

2014-03-01

352

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

PubMed Central

Parasitization by malaria-inducing Plasmodium falciparum leads to structural, biochemical, and mechanical modifications to the host red blood cells (RBCs). To study these modifications, we investigate two intrinsic indicators: the refractive index and membrane fluctuations in P. falciparum-invaded human RBCs (Pf-RBCs). We report experimental connections between these intrinsic indicators and pathological states. By employing two noninvasive optical techniques, tomographic phase microscopy and diffraction phase microscopy, we extract three-dimensional maps of refractive index and nanoscale cell membrane fluctuations in isolated RBCs. Our systematic experiments cover all intraerythrocytic stages of parasite development under physiological and febrile temperatures. These findings offer potential, and sufficiently general, avenues for identifying, through cell membrane dynamics, pathological states that cause or accompany human diseases.

Park, YongKeun; Diez-Silva, Monica; Popescu, Gabriel; Lykotrafitis, George; Choi, Wonshik; Feld, Michael S.; Suresh, Subra

2008-01-01

353

Photonic band gaps in quasiperiodic photonic crystals with negative refractive index  

NASA Astrophysics Data System (ADS)

We investigate the photonic band gaps in quasiperiodic photonic crystals made up of both positive (SiO2) and negative refractive index materials using a theoretical model based on a transfer matrix treatment. The quasiperiodic structures are characterized by the nature of their Fourier spectrum, which can be dense pure point (Fibonacci sequences) or singular continuous (Thue-Morse and double-period sequences). These substitutional sequences are described in terms of a series of generations that obey peculiar recursion relations. We discussed the photonic band gap spectra for both the ideal cases, where the negative refractive index material can be approximated as a constant in the frequency range considered, as well as the more realistic case, taking into account the frequency-dependent electric permittivity ? and magnetic permeability ? . We also present a quantitative analysis of the results, pointing out the distribution of the allowed photonic bandwidths for high generations, which gives a good insight about their localization and power laws.

Vasconcelos, M. S.; Mauriz, P. W.; de Medeiros, F. F.; Albuquerque, E. L.

2007-10-01

354

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.

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

2010-01-01

355

Refractive index sensor based on a 1D photonic crystal in a microfluidic channel.  

PubMed

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

356

A novel laser gain medium: Micro-sphere array cooled by refractive index-matched coolant  

NASA Astrophysics Data System (ADS)

A micro-sphere array laser gain medium cooled by refractive index-matched coolant was demonstrated for the first time to our knowledge. The new concept is possessed of potential to improve thermal management, to increase the thermal load capacity and to build large scale laser medium with small-sized solid laser materials. The feasibility was experimentally proved with an oscillator experiment in which reliable laser output was observed: the maximum output was 113.3 mJ for the pump energy of 765.8 mJ, the threshold was 131.7 mJ and the slope efficiency was 19%. Promising improvement could be achieved by employing methods for maintaining accurate refractive index matching during the lasing process.

Gui, Luo; Ding, Jianyong; She, Jiangbo; Peng, Bo; Wei, Wei; Fan, Dianyuan

2013-09-01

357

Sensitivity to refractive index of high-aspect-ratio nanofins with optical vortex.  

PubMed

An easy and large-scale fabrication technique of metal fins was used to produce periodic Au fin arrays that realized light confinement in the near-infrared region. Light confinement was revealed by vortex patterns in the optical power flow of an array of high-aspect-ratio fins (height of 1000 nm for a width of 50 nm). The light confinement resulted in sharp dips in the reflectance spectrum of the high-aspect-ratio fin array. The wavelengths of the reflectance dips were found to shift toward higher values when the refractive index of the surrounding medium was increased. Experimental and simulated dip shift values were in good agreement with a demonstrated sensitivity of 580 nm per refractive index unit. PMID:23186947

Maeda, Etsuo; Lee, Yaerim; Kobayashi, Youjiro; Taino, Akiko; Koizumi, Mari; Fujikawa, Shigenori; Delaunay, Jean-Jacques

2012-12-21

358

Directly photoinscribed refractive index change and Bragg gratings in Ohara WMS-15 glass ceramic  

SciTech Connect

We inscribed thick volume gratings in WMS-15 glass ceramic by ultraviolet light at 193 and 248 nm. Unlike earlier work in ceramic materials, the inscription process modified the optical properties of the material without the need for any additional chemical or thermal processing. Experimental evidence from measurements of grating growth, thermal annealing, and spectral absorption indicates that two distinct physical mechanisms are responsible for the grating formation. Weak, easily thermally bleached gratings resulted from exposure fluences below 0.3 kJ/cm{sup 2}. Optical absorption measurements suggest that these low fluence gratings are predominantly absorption gratings. More thermally stable gratings, found to be refractive index gratings with unsaturated refractive index modulation amplitude as large as 6x10{sup -5} were formed at cumulative fluences of 1 kJ/cm{sup 2} and above.

Krug, Peter A.; Matei Rogojan, Rodica; Albert, Jacques

2009-06-20

359

Determining the complex index of refraction of an unknown object using turbulence-degraded polarimetric imagery  

NASA Astrophysics Data System (ADS)

A novel index-of-refraction material-characterization technique using passive polarimetric imagery degraded by atmospheric turbulence is presented. The method uses a variant of the LeMaster and Cain [J. Opt. Soc. Am. A 25(9), 2170-2176 (2008)] blind-deconvolution algorithm to recover the true object (i.e., the first Stokes parameter), the degree of linear polarization, and the polarimetric-image point spread functions. Nonlinear least squares is then used to find the value of the complex index of refraction that best fits the theoretical degree of linear polarization, derived using a polarimetric bidirectional reflectance distribution function, to the turbulence-corrected degree of linear polarization. To verify the proposed material-characterization technique, experimental results of two painted metal samples are provided and analyzed.

Hyde, Milo W., IV

2010-12-01

360

Ultrasensitive refractive index sensor with temperature insensitivity based on concatenated LPGs  

NASA Astrophysics Data System (ADS)

In this paper we report on fabrication and characterization of a refractive index sensor based on two concatenated double resonanced long period fiber gratings (LPFGs) with an inter grating space in between them. The inter grating space provides a temperature dependent extra phase difference between the core mode and the participating cladding modes, making the sensor similar to a Mach-Zehnder interferometer with its arms phase shifted. We demonstrate that by adjusting the inter grating space the thermally induced phase difference in the LPG region can be compensated, producing temperature insensitive resonance wavelengths. The interferometer is highly stable over a wide range of temperatures (20-100 °C). The measured refractive index sensitivity for aqueous solutions (1.333-1.393) is 2583.3 nm/RIU, which is highly desirable for precision sensing of biological samples.

Tripathi, Saurabh M.; Bock, Wojtek J.; Kumar, Arun; Mikulic, Predrag; Bock, Katherine J.

2013-05-01

361

Analysis of Optically Induced Refractive Index Change of Dye-Doped Nematic Liquid Crystals  

NASA Astrophysics Data System (ADS)

We present a detailed quantitative experimental and theoretical study of laser induced refractive index changes in nematic liquid crystals doped with methyl-red, disperse red and azobenzene liquid crystal. These refractive index changes, originating from molecular reorientations and order parameter modification, are measured by means of intensity and polarization grating methods. The reorientation of the director axis is calculated from polarization dependence of the probe beam diffraction efficiency. The contribution of each effect to the total diffraction efficiency is quantitatively evaluated. In general, we found that the reorientational direction of the NLC molecules depends on the dopants as well as the nature of the pump beam polarization state. In methyl-red doped samples, the laser induced reorientation mechanism dominates, whereas order parameter modification plays a major role in the others.

Shishido, A.; SHIH, M.-Y.; Khoo, I. C.

362

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

363

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

PubMed Central

Determining the electronic and dielectric properties of water at high pressure and temperature is an essential prerequisite to understand the physical and chemical properties of aqueous environments under supercritical conditions, for example, in the Earth interior. However, optical measurements of compressed ice and water remain challenging, and it has been common practice to assume that their band gap is inversely correlated with the measured refractive index, consistent with observations reported for hundreds of materials. Here we report ab initio molecular dynamics and electronic structure calculations showing that both the refractive index and the electronic gap of water and ice increase with increasing pressure, at least up to 30?GPa. Subtle electronic effects, related to the nature of interband transitions and band edge localization under pressure, are responsible for this apparently anomalous behaviour.

Pan, Ding; Wan, Quan; Galli, Giulia

2014-01-01

364

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

365

Determination of complex refractive index of thin metal films from terahertz time-domain spectroscopy  

NASA Astrophysics Data System (ADS)

Thin metal films alone or incorporated in a multilayer stack structure with dielectric films are good candidates of terahertz absorbers necessary for achieving the maximum responsivity in microbolometer devices. However, the design and optimization of these absorber structures depend on the knowledge of the complex refractive index of metal films in the terahertz frequency range, which is not easy to measure or determine from experiment. This paper presents a novel method that allows fast and reliable extraction of the complex refractive index from terahertz time-domain spectroscopy. It starts with terahertz time-domain transmission measurements, followed by Fourier transforms to obtain the transmission spectrum in the frequency range of 0.1-3 THz, and finally an extraction process using the enhanced ``on-the-downhill'' algorithm. Some experimental examples are given, all of which show good agreement with theoretical calculations. This extraction method, combined with the scattering matrix model, can help design and optimize complicated absorber structures for terahertz microbolometers.

Zhou, Da-Xiang; Parrott, E. P. J.; Paul, Douglas J.; Zeitler, J. Axel

2008-09-01

366

Transient refractive index measurements in XeF laser gas mixtures  

SciTech Connect

Transient refractive index (TRI) measurements have been made in e-beam-pumped, XeF laser gas mixtures as a function of energy loading. Both NF/sub 3/ and F/sub 2/ were used as halogen donors in a neon base. TRI due to halogen donor burnup and to plasma dispersion was measured at 578.4 nm in typical laser mixtures containing Xe and at 353.2 nm in mixtures without Xe. The net index of refraction of the mixtures decreased with increasing energy loading, resulting in a difference of about 50 x 10/sup -9/ to 100 x 10/sup -9/ between a pumped and unpumped region at a typical loading of 150 J/I.

Fulghum, S.F.; Trainor, D.; Appel, C.

1989-05-01

367

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

368

Observation of refractive index gradients in a laser-generated plume using laser schlieren imaging  

SciTech Connect

Understanding the interaction between a pulsed Nd:YAG laser beam and the plume generated above the surface of a workpiece during laser welding is important for process modeling and control. We present a laser schlieren method which can be used to observe this interaction by imaging the refractive index gradient within the plume. The laser schlieren technique uses an expanded, collimated probe laser beam to image a phase object onto a filter with a radial gradient in optical density. The probe beam is focused through the filter and onto the image plane of an intensified high-speed camera, so that the temporal variation of the laser/plume interaction may be observed over the duration of the laser pulse. Qualitative measurements of the spatial distribution of refractive index are presented. The velocity of the vaporized metal forming the plume is also measured for a stainless steel weldment.

Essien, M.; Keicher, D.M.; Jellison, J.L.

1995-12-31

369

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

370

Refractive index dispersion in thin ZnGa2O4 films  

NASA Astrophysics Data System (ADS)

We have studied refractive index dispersion in thin ZnGa2O4 films obtained by high-frequency RF ion plasma sputtering. We have established that the spectral dependence of the refractive index in the visible region of the spectrum is mainly determined by transitions from the band including 2p states of the oxygen and 3d states of the zinc, forming the highest occupied level of the valance band, to the bottom of the conduction band formed by the 4s4p states of the zinc. For the studied films, we have determined the parameters of the single-oscillator approximation, the dispersion energy, the chemical bond ionicity, and the coordination number.

Bordun, O. M.; Kukharskyy, I. Yo.; Bihday, V. G.

2012-01-01

371

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

372

Refractive Index and Size Distribution of Aerosols as Estimated from Light Scattering Measurements.  

NASA Astrophysics Data System (ADS)

Angular distributions of the intensity of light scattered by airborne particles were measured for both parallel and perpendicularly polarized components. A precision polar nephelometer was constructed for use of this study. The data were analyzed using a newly developed inversion library method to give a simultaneous estimate of the complex index of refraction m = mr mii of aerosols and their size distribution, where mr is the real part and mi the imaginary part of the refractive index. Results of 302 measurements show that the monthly mean values of mr and mi vary within the range 1.47-1.57 and 0.009-0.037, respectively, depending upon the relative humidity.The size distribution of aerosols can be approximated by the log-normal distribution function; the mean radius and the standard deviation are found to be rg = 0.138 m and g = 2.56, respectively, as geometrical mean values for the whole data.

Tanaka, Masayuki; Takamura, Tamio; Nakajima, Teruyuki

1983-07-01

373

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

PubMed

Determining the electronic and dielectric properties of water at high pressure and temperature is an essential prerequisite to understand the physical and chemical properties of aqueous environments under supercritical conditions, for example, in the Earth interior. However, optical measurements of compressed ice and water remain challenging, and it has been common practice to assume that their band gap is inversely correlated with the measured refractive index, consistent with observations reported for hundreds of materials. Here we report ab initio molecular dynamics and electronic structure calculations showing that both the refractive index and the electronic gap of water and ice increase with increasing pressure, at least up to 30 GPa. Subtle electronic effects, related to the nature of interband transitions and band edge localization under pressure, are responsible for this apparently anomalous behaviour. PMID:24861665

Pan, Ding; Wan, Quan; Galli, Giulia

2014-01-01

374

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

375

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

NASA Astrophysics Data System (ADS)

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

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

1996-01-01

376

Photonic band gaps in quasiperiodic photonic crystals with negative refractive index  

Microsoft Academic Search

We investigate the photonic band gaps in quasiperiodic photonic crystals made up of both positive (SiO2) and negative refractive index materials using a theoretical model based on a transfer matrix treatment. The quasiperiodic structures are characterized by the nature of their Fourier spectrum, which can be dense pure point (Fibonacci sequences) or singular continuous (Thue-Morse and double-period sequences). These substitutional

M. S. Vasconcelos; P. W. Mauriz; F. F. de Medeiros; E. L. Albuquerque

2007-01-01

377

Zero n ¯ photonic band gap in a quasiperiodic stacking of positive and negative refractive index materials  

Microsoft Academic Search

Light propagation in a Fibonacci sequence consisting of alternating slabs of positive and negative refractive index materials is studied with a transfer matrix method. A zero-n¯ gap is found in the photonic spectra of this quasiperiodic structure. The self-similar and non-self-similar wave functions are exhibited at the frequencies close to the zero-n¯ gap. It also shows that the zero-n¯ gap

Jing Li; Degang Zhao; Zhengyou Liu

2004-01-01

378

Electrostrictive contribution to the intensity-dependent refractive index of optical fibers  

Microsoft Academic Search

We show that electrostriction contributes significantly to self-action effects in optical fibers, adding 19% to the nonlinear refractive index for fields that vary slowly compared with the ,1-ns time scale of the acoustic response. Electrostriction also modifies the tensor nature of the nonlinear-optical response. The electrostrictive nonlinearity is the origin of the observed difference between measurements of n2 with cw

Eric L. Buckland; Robert W. Boyd

1996-01-01

379

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

Microsoft Academic Search

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

Young-Sik Ghim; Seung-Woo Kim

2006-01-01

380

Temperature dependence of the refractive-index dispersion in amorphous germanium at elevated temperatures  

Microsoft Academic Search

Refractive-index dispersion in amorphous germanium was measured in the vicinity of the optical gap (0.2-1.2 eV) and for the first time at elevated temperatures (25°C-400°C). The results at each temperature follow the dispersion of a single oscillator, whose resonance energy and strength decrease linearly with temperature. However, the magnitude of these variations differs markedly (e.g., by a factor of 2

D. Goldschmidt

1983-01-01

381

Temperature-Dependent Refractive Index Determination from Critical Angle Measurements:  Implications for Quantitative SPR Sensing  

Microsoft Academic Search

Temperature-dependent measurements of surface cover- age and interfacial kinetics remain relatively unexploited in thin-film sensing applications that rely on optical surface-sensitive techniques such as surface plasmon resonance spectroscopy (SPR). These techniques are inherently sensitive to the optical properties of the bulk solution in contact with the thin film; therefore, quantita- tive thin-film sensing requires accurate refractive index data for bulk

James H. Grassi; Rosina M. Georgiadis

1999-01-01

382

Refractive index dynamics of InAs/GaAs quantum dots  

NASA Astrophysics Data System (ADS)

The refractive index dynamics of an InAs/InGaAs/GaAs dots-in-a-well semiconductor optical amplifier is calculated and compared with experimental results. The fast and slow recovery timescales together with the behaviour with increasing injection are reproduced and explained in terms of the density of carriers available in upper quantum dot and continuum states. Also, a Coulomb-mediated shift of the dot susceptibility is suggested as responsible for the fast recovery of the phase.

Crowley, M. T.; Houlihan, J.; Piwonski, T.; O'Driscoll, I.; Williams, D. P.; O'Reilly, E. P.; Uskov, A. V.; Huyet, G.

2013-07-01

383

The Index of Refraction of Lithium Fluoride at Pressures in Excess of 100 GPa  

NASA Astrophysics Data System (ADS)

The compression of materials to high pressure can alter their optical properties in ways that provide insight into the resulting structural changes. Under strong shock compression; transparent insulators transform into conducting fluids as a result of pressure-induced reduction of the band gap and thermal promotion of electrons across that gap. A new ramp compression technique; direct-drive shaped ablation, is used to compress LiF to 800 GPa without generating shocks thereby producing high pressures at significantly lower temperatures than would be created by shock waves. In this study, ramp compressed lithium fluoride (LiF) is observed to remain transparent to 800 GPa, pressures seven times higher than previous shock compression experiments. The ramp compressed refractive index of LiF is measured at pressures up to 800 GPa and depends linearly on density over this range. This is the highest pressure refractive index measurement made to date. The linear dependence of the refractive index and density is examined using a single-oscillator model. This model indicates that the linear behavior is a result of monoatomic closure of the band gap. Extrapolation of these results indicates that the band gap closure (metallization) will be greater than 5,000 GPa, well above the Goldhammer-Herzfeld criterion for metallization (˜ 2,860 GPa). The high metallization pressure of LiF is attributed to its large band gap and isoelectronic counterparts that exhibit high metallization pressures. The high pressure transparency of LiF has technical utility as an optical window for materials studies since the transparency at high pressure allows in situ measurements of samples confined by that window. The observed transparency and measurement of LiF refractive index enables advancement of those experiments to higher pressure regimes.

Fratanduono, Dayne Eric

384

Refractive index modification in glass by laser backwriting ablation of metals.  

PubMed

We report the use of laser ablation of metal targets onto a glass substrate as a way of producing waveguiding devices. In the geometry employed, the nanosecond pulses used for the ablation pass through the glass substrate, and are focused on the metal surface, which is located in close proximity with the substrate. We present measurements of the refractive index profile obtained with this technique, and present a discussion of the physical mechanisms that produce the profiles measured. PMID:19529258

Rangel-Rojo, Raul; Castelo, A; Flores-Arias, M T; Gómez-Reino, C; López-Gascón, C I; de la Fuente, G F

2006-09-18

385

Large negative refractive index modification induced by irradiation of femtosecond laser inside optical glasses  

Microsoft Academic Search

We report on the refractive index modification (?n) and its cross sectional profile of the created lines inside the different types of optical glasses, containing BaO, TiO2, or La2O3 as a metal oxide. The lines were fabricated by scanning a stage and focusing the femtosecond laser pulses, 800nm wavelength, a 250kHz repetition rate and 200fs pulse duration, from the Ti:sapphire

Tomohiro Hashimoto; Shuhei Tanaka

2011-01-01

386

Fabrication of Submicrometer High Refractive Index Tantalum Pentoxide Waveguides for Optical Propulsion of Microparticles  

Microsoft Academic Search

Design, fabrication, and optimization of tantalum pentoxide (Ta2O5 ) waveguides to obtain low-loss guidance at a wavelength of 1070 nm are reported. The high-refractive index contrast (Deltan ~ 0.65, compared to silicon oxide) of Ta2O5 allows strong confinement of light in waveguides of submicrometer thickness (200 nm), with enhanced intensity in the evanescent field. We have employed the strong evanescent

Balpreet Singh Ahluwalia; Ananth Z. Subramanian; Olav Gaute Hellesø; Nicolas M. B. Perney; Neil P. Sessions; James S. Wilkinson

2009-01-01

387

Scaling of Surface Plasmon Resonances in Triangular Silver Nanoplate Sols for Enhanced Refractive Index Sensing  

Microsoft Academic Search

The plasmonic spectra of solution phase ensembles of triangular silver nanoplates have been analysed in order to examine the\\u000a fundamental properties underlying their size-dependent enhanced refractive index sensitivities. Linewidth studies highlight\\u000a variations in the response of these solution phase nanostructures to those previously reported for single immobilized triangular\\u000a nanostructures. The observation of insignificant broadening of the resonance linewidth for larger

Denise E. Charles; Matthew Gara; Damian Aherne; Deirdre M. Ledwith; John M. Kelly; Werner J. Blau; Margaret E. Brennan-Fournet

2011-01-01

388

Subpicosecond interferometric measurement of the nonlinear refractive index of poly(3-hexylthiophene).  

PubMed

We measured the magnitude and the time response of the nonlinear refractive index (n(2)) of poly(3-hexylthiophene)by a femtosecond time-resolved interferometric technique. Decays of 320 fs and 3.0 ps were found. The n(2) value obtained was -6 x 10(-9) esu at 620 nm. Calculation of the dispersion of n(2) showed that the negative value is consistent with that of a four-level model. PMID:19798245

Hattori, T; Okawa, H; Wada, T; Sasabe, H

1992-11-15

389

Nonlinear refractive index and three-photon absorption coefficient of Poly(9,9-dioctylfluorence) (PFO)  

Microsoft Academic Search

We report on the nonlinear optical Kerr effect and third harmonic generation (THG) arising from &(3)circ; of Poly(9,9- dioctylfluorence) (PFO), which is an emerging organic pi- conjugated polymer from the perspective of diverse optoelectronic applications. The measured nonlinear refractive index, obtained with closed-aperture Z-scan, is n2= (2.04 ±0.10)x10-12 esu at lambda= 1540 nm. Open- aperture Z-scan yields the three-photon absorption

Shahin Mani; Joon Jang; John Ketterson; Pierre Lovera; Gareth Redmond

2010-01-01

390

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

391

Side-polished plastic optical fibre as refractive index, cure and viscosity sensor  

NASA Astrophysics Data System (ADS)

Sensors based on side-polished plastic optical fibre are presented. To enhance the sensitivity to a certain physical parameter, the guiding properties of an optical fibre have to be weakened. Side-polishing technique offers a simple implementation, since the mechanical resistance of the POF allows an easy removal of a portion of the jacket, cladding and core. Three sensors are characterized under a wide range of external refractive indexes. Both, theoretical and experimental results show that the range of operation of the refractive index sensor can be shifted by using different geometries or different macrobending conditions of the sensitive area. The phenomenon behind the principle of operation of the sensor is the reflection and transmission of light at an interface of two dielectric media expressed by Fresnel's equations. The use of this intrinsic scheme to monitor the cure process of a material or the viscosity of a liquid is also presented. The changes in refractive index are used to monitor, in real time, the cure of different materials such as resins and varnishes because the optical properties of the material can be related to the density of the material. The viscosity of a liquid is related to the droplet formation in a convexly bended sensor.

Bilro, L.; Alberto, N.; Sá, L. M.; Pinto, J. L.; Nogueira, R. N.

2011-05-01

392

Origin of the refractive index modification of femtosecond laser processed doped phosphate glass  

NASA Astrophysics Data System (ADS)

The origin of the local refractive index modification in femtosecond laser inscribed structures has been investigated with confocal microfluorescence imaging. We have identified the origin of both, positive and negative refractive index changes in a commercial Er-Yb codoped phosphate glass upon irradiation in the low repetition rate regime (1 kHz). Consistent relations among the photoluminescence behavior of the dopants (erbium and ytterbium ions), the local sign of the density change and the local modification of the refractive index by means of characteristic emission features such as the intensity and the spectral peak position have been established. Blue or redshift in the photoluminescence emission have been observed and related to a local perturbation in the crystal field caused by a modification of the mean distance among the dopant ions, and thus of the local matrix density. These conclusions are additionally supported by the spatial distribution of photoluminescence emission intensities, which have been interpreted in terms of energy transfer mechanisms underlying the overall erbium-ytterbium emission process.

Ferrer, Andrés; Jaque, Daniel; Siegel, Jan; La Cruz, Alexandro Ruiz De; Solís, Javier

2011-05-01

393

Photochemical laminating of low-refractive-index transparent antireflective SiO2 film  

NASA Astrophysics Data System (ADS)

A transparent low refractive index SiO2 film was laminated on a glass substrate with photochemical reaction by an Xe2* excimer lamp in the presence or NF3, 02 and silicon wafer at room temperature. The glass substrate and the silicon wafer were placed in the reaction chamber, which was filled with NF3 and O2 gases in the mixing ratio of 10:1 and under 330 Torr. The Xe2* excimer lamp was, then, irradiated for 20 minutes. The SiO2 film was spontaneously laminated on the glass substrate by repeating an adsorption of SiF4 and a photochemical oxidization with NO2, which was photo-dissociated from a mixed gas of NF3 and O2. The film thickness was 160 nm and the infrared spectrum was measured; the Si-O peaks were depicted at 600, 700, 1100[1/cm-1]. And Si-F peak was observed at 740[1/cm-1]. Then, the refractive index of the SiO2 film was 1.36. After annealing the film for one hour at 200 degree, the refractive index increased to 1.42.

Murahara, Masataka M.; Ogawa, Yasuhiro; Yoshida, Kunio; Okamoto, Yoshiaki

2003-05-01

394

Velocimetry with refractive index matching for complex flow configurations, phase 1  

NASA Astrophysics Data System (ADS)

The feasibility of obtaining detailed velocity field measurements in large Reynolds number flow of the Space Shuttle Main Engine (SSME) main injector bowl was demonstrated using laser velocimetry and the developed refractive-index-matching technique. An experimental system to provide appropriate flow rates and temperature control of refractive-index-matching fluid was designed and tested. Test results are presented to establish the feasibility of obtaining accurate velocity measurements that map the entire field including the flow through the LOX post bundles: sample mean velocity, turbulence intensity, and spectral results are presented. The results indicate that a suitable fluid and control system is feasible for the representation of complex rocket-engine configurations and that measurements of velocity characteristics can be obtained without the optical access restrictions normally associated with laser velocimetry. The refractive-index-matching technique considered needs to be further developed and extended to represent other rocket-engine flows where current methods either cannot measure with adequate accuracy or they fail.

Thompson, B. E.; Vafidis, C.; Whitelaw, J. H.

1987-08-01

395

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.

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

2013-01-01

396

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

397

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

398

Accurate in situ measurement of complex refractive index and particle size in intralipid emulsions  

NASA Astrophysics Data System (ADS)

A first accurate measurement of the complex refractive index in an intralipid emulsion is demonstrated, and thereby the average scatterer particle size using standard Mie scattering calculations is extracted. Our method is based on measurement and modeling of the reflectance of a divergent laser beam from the sample surface. In the absence of any definitive reference data for the complex refractive index or particle size in highly turbid intralipid emulsions, we base our claim of accuracy on the fact that our work offers several critically important advantages over previously reported attempts. First, our measurements are in situ in the sense that they do not require any sample dilution, thus eliminating dilution errors. Second, our theoretical model does not employ any fitting parameters other than the two quantities we seek to determine, i.e., the real and imaginary parts of the refractive index, thus eliminating ambiguities arising from multiple extraneous fitting parameters. Third, we fit the entire reflectance-versus-incident-angle data curve instead of focusing on only the critical angle region, which is just a small subset of the data. Finally, despite our use of highly scattering opaque samples, our experiment uniquely satisfies a key assumption behind the Mie scattering formalism, namely, no multiple scattering occurs. Further proof of our method's validity is given by the fact that our measured particle size finds good agreement with the value obtained by dynamic light scattering.

Dong, Miao L.; Goyal, Kashika G.; Worth, Bradley W.; Makkar, Sorab S.; Calhoun, William R.; Bali, Lalit M.; Bali, Samir

2013-08-01

399

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

400

Simultaneous measurement of refractive index and temperature by integrating an external Fabry-Perot cavity with a fiber Bragg grating.  

PubMed

A fiber sensor for simultaneous measurements of refractive index and temperature based on the integration of a fiber Bragg grating (FBG) with an external Fabry-Perot (F-P) cavity is presented. The fringe contrast of the interference spectrum generated by the F-P cavity is used to determine the external refractive index, while the wavelength shift of the FBG is used to measure temperature. The result showed that the refractive index and temperature sensitivity for the integrated sensor is 8.1 × 10(-6) and 0.01006 nm/°C, respectively. PMID:22667608

Chen, Luan Xiong; Huang, Xu Guang; Li, Jiao Yang; Zhong, Ze Bing

2012-05-01

401

Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing.  

PubMed

We demonstrate a fiber in-line Fabry-Perot interferometer cavity sensor for refractive index measurement. The interferometer cavity is formed by drilling a micro-hole at the cleaved fiber end facet, followed by fusion splicing. A micro-channel is inscribed by femtosecond laser micromachining to vertically cross the cavity to allow liquid to flow in. The refractive index sensitivity obtained is ~994 nm/RIU (refractive index unit). Such a device is simple in configuration, easy for fabrication and reliable in operation due to extremely low temperature cross sensitivity of ~4.8 × 10(-6) RIU/°C. PMID:23037431

Liao, C R; Hu, T Y; Wang, D N

2012-09-24

402

Optimization of the Refractive-Index Distribution of Graded-Index Polymer Optical Fiber by the Diffusion-Assisted Fabrication Process  

NASA Astrophysics Data System (ADS)

Graded-index polymer optical fiber (GI-POF) is a promising high-speed communication medium for very-short-reach networks, such as home or office networks. The refractive-index distribution of GI-POF needs to be accurately controlled to maximize the bandwidth. We attempted to control the refractive-index distribution by developing a simulation for dopant diffusion. In the rod-in-tube method, GI-POF with an optimal refractive-index distribution was obtained by adjusting the diffusion temperature and the diffusion time, whereas in the coextrusion process, GI-POF with an optimal refractive-index distribution was fabricated by controlling the length of the diffusion tube and the rate of discharge of polymer.

Mukawa, Yoshiki; Kondo, Atsushi; Koike, Yasuhiro

2012-04-01

403

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

404

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

NASA Astrophysics Data System (ADS)

Crystallins are present in the lens at extremely high concentrations in order to provide transparency and generate a high refractive power of the lens. The crystallin families prevalent in the highest density lens tissues are ?-crystallins in vertebrates and S-crystallins in cephalopods. As shown elsewhere, in parallel evolution, both have evolved molecular refractive index increments 5-10% above those of most proteins. Although this is a small increase, it is statistically very significant and can be achieved only by very unusual amino acid compositions. In contrast, such a molecular adaptation to aid in the refractive function of the lens did not occur in crystallins that are preferentially located in lower density lens tissues, such as vertebrate ?-crystallin and taxon-specific crystallins. In the current work, we apply a model of non-interacting hard spheres to examine the thermodynamic contributions of volume exclusion at lenticular protein concentrations. We show that the small concentration decrease afforded by the higher molecular refractive index increment of crystallins can amplify nonlinearly to produce order of magnitude differences in chemical activities, and lead to reduced osmotic pressure and the reduced propensity for protein aggregation. Quantitatively, this amplification sets in only at protein concentrations as high as those found in hard lenses or the nucleus of soft lenses, in good correspondence to the observed crystallin properties in different tissues and different species. This suggests that volume exclusion effects provide the evolutionary driving force for the unusual refractive properties and the unusual amino acid compositions of ?-crystallins and S-crystallins.

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

2011-08-01

405

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

406

Research on polarization state of prism coupler sensor for measuring liquid refractive index  

NASA Astrophysics Data System (ADS)

Due to many experimental data required and a lot of calculations involved, it is very complex and cumbersome to model prism-based liquid-refractive-index-measuring methods. By use of the feature of TE-polarized wave and TM-polarized wave and differential measurement principle, we developed a new method of mathematical modeling for measuring refractive index of a liquid based upon Fresnel formula and prism internal reflection at incident angle less than critical angle. With this method only two different concentrations measurements for a kind of solution can lead to the determination of computational model. It introduces the principle of an optic-fiber sensor system based on prism-coupler for measuring refractive index of a liquid, and it contains the configuration picture of the sensing optical path, the spectrogram of the semiconductor laser and the structure block diagram of measuring system, the system is mainly made up of the semiconductor laser with 1654.14nm in wavelength, 1×2 optical switch, Y-shaped photo-coupler with coupled rate 50:50, the detector based on isosceles prism-coupler, the data process and control system based on AT89C51 and photoelectric transformer. For TM-polarized wave and TE-polarized wave, theoretical simulations show that the ratio of sensitivity is 1.11, therefore, the beam that the component of TM-polarized wave is more than the one of TE-polarized wave is advantageous to heightening the system?s measurement sensitivity. Measurements are performed to examine the validity of the theoretical model and four theoretical models are given, and these results indicate the feasibility of four theoretical models with an error of 3%. In this study, a beam of light is broken down into two beams in the coupler of Y-shaped coupler, the one acts as the reference optical path, the other is known as the sensing optical path, consequently the method can limit well the fluctuation of the light source, the variation of the photodiode? s dark-current of photodiode and many other interfering factors and can be used for real-time detection and online analysis of liquid refractive-index. The method is also capable of measuring even smaller changes in the optical refractive index of the material on a metal surface by the surface plasma resonance sensing techniques.

Zhang, Zhi-Wei

2013-09-01

407

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

NASA Astrophysics Data System (ADS)

Spectra and optical constants of nitrile ices known or suspected to be in Titan's atmosphere are presented from 2.5 to 200 microns (4000 to 50 cm-1 ). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan's winter pole. Ices studied include: HCN, hydrogen cyanide; C2 N2 , cyanogen; CH3 CN, acetonitrile; C2 H5 CN, propionitrile; and HC3 N, cyanoacetylene. For each of these molecules we report new measurements of the index of refraction, n, determined in both the amorphous-and crystalline-phase at 670 nm. Spectra were measured and optical constants were calculated for each nitrile at a variety of temperatures including 20, 35, 50, 75, 95, and 110 K, in the amorphous-and crystalline-phase. This laboratory effort uses a dedicated FTIR spectrometer to record transmission spectra of thin-film ice samples. Laser interference is used to measure film thickness during condensation onto a transparent cold window attached to the tail section of a closed-cycle helium cryo-stat. Optical constants, real (n) and imaginary (k) refractive indices, are determined using Kramers-Kronig (K-K) analysis. Our calculation reproduces the complete spectrum, including all interference effects. Index of refraction measurements are made in a separate dedicated FTIR spectrometer where interference deposit fringes are measured using two 670 nm lasers at different angles to the ice substrate. A survey of these new measurements will be presented along with a discussion of their validation, errors, and application to Titan data. We acknowledge Mark Loeffler who recently joined in our refractive index measurements. The authors also acknowledge support from the Cassini Data Analysis Program. RLH and MHM acknowledge additional funding from NASA's PGG and Outer Planets Programs, and the Goddard Center for Astrobiology.

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

408

Spatially confined and temporally resolved refractive index and scattering evaluation in human skin performed with optical coherence tomography  

Microsoft Academic Search

In the present applications of optical coherence tomography (OCT), parameters besides pure morphology are evaluated in skin tissue under in vivo conditions. Spatially mapped refractive indices and scattering coefficients may support tissue characterization for research and diagnostic purposes in cosmetics\\/pharmacy and medicine, respectively. The sample arm of our OCT setup has been arranged to permit refractive index evaluation with little

Alexander R. Knuettel; Martin Boehlau-Godau

2000-01-01

409

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

NASA Technical Reports Server (NTRS)

Spectra and optical constants of nitrite ices known or suspected to be in Titan's atmosphere are presented from 2.5 to 200 microns (4000 to 50 per cm ). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan's winter pole. Ices studied include: HCN, hydrogen cyanide; C2N2, cyanogen; CH3CN, acetonitrile; C 2H5CN, propionitrile; and HC3N, cyanoacetylene. For each of these molecules we report new measurements of the index of refraction, n, determined in both the amorphous- and crystallinephase at 670 nm. Spectra were measured and optical constants were calculated for each nitrite at a variety of temperatures including 20, 35, 50, 75, 95, and 110 K, in the amorphous- and crystalline-phase. This laboratory effort uses a dedicated FTIR spectrometer to record transmission spectra of thin-film ice samples. Laser interference is used to measure film thickness during condensation onto a transparent cold window attached to the tail section of a closed-cycle helium cryostat. Optical constants, real (n) and imaginary (k) refractive indices, are determined using Kramers-Kronig (K-K) analysis. Our calculation reproduces the complete spectrum, including all interference effects. Index of refraction measurements are made in a separate dedicated FTIR spectrometer where interference deposit fringes are measured using two 670 nm lasers at different angles to the ice substrate. A survey of these new measurements will be presented along with a discussion of their validation, errors, and application to Titan data.

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

2010-01-01

410

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

PubMed

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

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

2014-07-01

411

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

412

Highly sensitive compact refractive index sensor based on phase-shifted sidewall Bragg gratings in slot waveguide.  

PubMed

The geometrical and physical parameters of phase-shifted sidewall Bragg gratings in a silicon slot waveguide are optimized to possess performance characteristics desirable for integrated optical sensors. By tailoring the spectral response of such phase-shifted sidewall gratings, highly sensitive compact refractive index sensors detecting the resonance wavelength shift or the variation of light intensity are designed with the transfer matrix method. Both refractive index sensors have a minimum detection limit on the order of 10(-6), and a linear response and a compact structure dimension as small as 11.7 ?m, offering the capabilities for sensor array and lab-on-a-chip integration. The resonance-shift sensor has a much wider detection range of 1.32 refractive index units than the intensity-measurement sensor. The performance parameters are compared with other refractive index sensors, including Mach-Zehnder interferometers, ring resonators, surface gratings, and phase-shifted gratings in silicon nanowire. PMID:24513995

Wang, Xin; Madsen, Christi K

2014-01-01

413

Design of multilayer antireflection coatings made from co-sputtered and low-refractive-index materials by genetic algorithm.  

PubMed

Designs of multilayer antireflection coatings made from co-sputtered and low-refractive-index materials are optimized using a genetic algorithm. Co-sputtered and low-refractive-index materials allow the fine-tuning of refractive index, which is required to achieve optimum anti-reflection characteristics. The algorithm minimizes reflection over a wide range of wavelengths and incident angles, and includes material dispersion. Designs of antireflection coatings for silicon-based image sensors and solar cells, as well as triple-junction GaInP/GaAs/Ge solar cells are presented, and are shown to have significant performance advantages over conventional coatings. Nano-porous low-refractive-index layers are found to comprise generally half of the layers in an optimized antireflection coating, which underscores the importance of nano-porous layers for high-performance broadband and omnidirectional antireflection coatings. PMID:18542630

Schubert, Martin F; Mont, Frank W; Chhajed, Sameer; Poxson, David J; Kim, Jong Kyu; Schubert, E Fred

2008-04-14

414

Nonlinear-index-of-refraction measurement in a resonant region by the use of a fiber Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

The nonlinear index of refraction in a resonant region has been determined by the use of a fiber-based Mach-Zehnder interferometer to measure the temporal fringe shift between two signals. The measurement technique is direct and does not require additional amplitude information for the extraction of the nonlinear index of refraction. This technique has been used to measure the temporal response of an InGaAsP semiconductor optical amplifier at 1.313 mu m.

Kang, K. I.; Chang, T. G.; Glesk, I.; Prucnal, P. R.

1996-03-01

415

Two-dimensional distribution of refractive-index changes in Ti-diffused LiNbO3 strip waveguides  

Microsoft Academic Search

A method is reported for determining the two-dimensional distribution of refractive-index changes in Ti-diffused LiNbO3 strip waveguides. The measurement process was as follows. Distributions of diffused Ti concentration in LiNbO3 were measured using an x-ray microanalyzer. Using calibration curves the Ti concentrations were then converted into refractive-index changes. To obtain high spatial resolution in the two-dimensional XMA measurement the electron

Makoto Minakata; Shoichi Saito; Masashi Shibata

1979-01-01

416

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.

Guzman-Sepulveda, Jose Rafael; Guzman-Cabrera, Rafael; Torres-Cisneros, Miguel; Sanchez-Mondragon, Jose Javier; May-Arrioja, Daniel Alberto

2013-01-01

417

Low refractive index gas sensing using a surface plasmon resonance fibre device  

NASA Astrophysics Data System (ADS)

A series of surface plasmonic fibre devices were fabricated using multiple coatings deposited on a lapped section of a single mode fibre. Coupling from the guided mode to surface plasmons was promoted following UV laser irradiation of the coated region through a phase mask, which generated a surface relief grating structure. The devices showed high spectral sensitivities and strong coupling for low refractive indices as compared to other grating-type fibre devices. The plasmonic devices were used to detect the variation in the refractive indices of alkane gases with measured wavelength and coupling sensitivity to index of 3400 nm RIU-1 and 8300 dB RIU-1, respectively. As a demonstration of the performance of these gas sensors, a minimum concentration of 2% by volume of butane in ethane was achieved.

Allsop, T.; Neal, R.; Davies, E. M.; Mou, C.; Bond, P.; Rehman, S.; Kalli, K.; Webb, D. J.; Calverhouse, P.; Bennion, I.

2010-09-01

418

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

419

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.

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

2013-01-01

420

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

421

Commercial scale fabrication method for fabricating a gradient refractive-index rod: Overcoming volume shrinkage and chemical restrictions.  

PubMed

We report a fabrication method for a gradient refractive-index polymeric object from a binary comonomer system, regardless of the monomers' reactivity ratio and the molar volume criteria of gradient refractive-index development. To fabricate a large gradient refractive-index rod consisting of a methyl methacrylate and 2,2,3,3-tetrafluoropropyl methacrylate comonomer pair that has not been used for fabrication of a copolymer gradient refractive-index rod by previous conventional methods because of chemical restrictions in molar volume and reactivity ratio difference, we use the so-called successive UV polymerization in a controlled radial volume in conjunction with an automatic refill reactor. Simultaneously and automatically, the volume shrinkage problem, an inevitable shortcoming for the fabrication of a large polymeric object in a commercial production scale, is overcome and exploited. The theoretical features of the refractive-index profile generation of this method are also compared with those of conventional methods for which the chemical restrictions of monomers are crucial for the shape of a refractive-index profile. PMID:16983409

Cho, Hansol; Son, Young Mok; Kim, Mu Gyeom; Ra, Byoung Joo; Park, Joon-Yong; Lee, Seung Hui; Choi, Jin Sung; Song, Min Young; Park, O Ok; Kim, Youn Cheol; Hwang, Jin Taek

2006-10-01

422

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.

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

2010-01-01

423

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

424

Determination of index of refraction and size of supermicrometer particles from light scattering measurements at two angles  

NASA Astrophysics Data System (ADS)

A twin angle optical particle counter (TAOPC) that measures forward scattering at 40° and 74° was developed to determine the index of refraction of atmospheric particles. An error analysis indicates that measurement uncertainties for size at 40° are between 4 and 10% for particles >1.5 ?m and between 5 and 15% at 74°. For the index of refraction determination, the measurement uncertainties lead to index of refraction uncertainties between 1 and 2.5%. The instrument was tested on nonabsorbing spherical particles of known composition and size in the laboratory. The majority of the estimated indices of refraction were within ±1% of the expected indices, and size determination was within acceptable error. The instrument was also tested on non-spherical absorbing particles to determine the complex index of refraction of ambient mineral dust particles collected in Laramie, Wyoming, in February 2006. The index of refraction was determined with the particle number ratio approach and was estimated to be in the range 1.60-1.67 for the real part and 0.009-0.0104 for the imaginary part. Simultaneously with the TAOPC measurements, particles were collected on polycarbonate filters for computer-controlled scanning electron microscopy (CCSEM) analysis. Index of refraction calculated from this analysis was in the range 1.61-1.66 for the real part and 0.008-0.012 for the imaginary part. Particles were also collected for longer periods on two different filter pack systems in February 2006. Estimates of index of refraction from these measurements compared well with the CCSEM analysis.

Eidhammer, Trude; Montague, Derek C.; Deshler, Terry

2008-08-01

425

Higher-order nonlinearity of refractive index: The case of argon.  

PubMed

The nonlinear coefficients, n4, of the time-dependent refractive index for argon are calculated in the non-resonant optical regime. Second-order polynomial fitting of DC-Kerr, ?((2))(-?; ?, 0, 0), electric field induced second harmonic generation (ESHG), ?((2))(-2?; ?, ?, 0), and static second-order hyperpolarizability, ?((2))(0; 0, 0, 0), is performed using an auxiliary electric field approach to obtain the corresponding fourth-order optical properties. A number of basis sets are investigated for the fourth-order hyperpolarizability processes at 800 nm at coupled cluster singles and doubles level of theory, starting with the t-aug-cc-pV5Z basis set and expanding that basis set by adding diffuse functions and polarization functions. Comparison shows that the results obtained with the t-aug-cc-pV5Z basis are in very good agreement with the results obtained using the q-aug-cc-pV5Z, t-aug-cc-pV6Z, and q-aug-cc-pV6Z basis sets. To calculate the nonlinear refractive index n4, an approximate formula is suggested which expresses the related degenerate six-wave mixing coefficient, ?((4))(-?; ?, -?, ?, -?, ?), in terms of the DC-Kerr, ?((4))(-?; ?, 0, 0, 0, 0), ESHG, ?((4))(-2?; ?, ?, 0, 0, 0), and the static fourth-order hyperpolarizability coefficients. The higher-order nonlinear refractive index n4 is found to be positive over the wavelengths 300 nm-2000 nm. In the infrared spectral range, the obtained values of n4 are in qualitative agreement with the results of Kramers-Kronig-based calculations. PMID:24908017

Tarazkar, Maryam; Romanov, Dmitri A; Levis, Robert J

2014-06-01

426

Using three different optical fiber designs to study humidity effect on the air refractive index  

NASA Astrophysics Data System (ADS)

Design and operation of three different optical designs based on the light intensity modulation for investigation of the humidity effects on the air index of refraction are described. The measurement variable is the transmitted power, which depends on the refractive index of the medium in the path of a fiber-to-fiber optical design. Three different probes (probe #1, #2, and #3) are tested in which probe #1 and probe #2 can also check the presence of water or any other transparent liquid in the gap between the two axial fibers. Performances of the new systems are tested as a refractive index monitoring mean and experimental results are given. The variations of the modulated powers as functions of the air humidity change in the light path are determined for the reported optical designs. For probe #1 for a power variation of 255-315 nW, the relative humidity changes from 32% to 41%. For probe #2 for 5 mm gap distance, for a power change of 2470-2754 nW, the relative humidity changes from 54.95% to 90.39%. For probe #3 for the 10 mm fiber gap, a power change 929.5-972.9 nW is noted for the relative humidity change of 33.0-76.75%. Power variations as a function of the axial fiber gap distances are also given and the optimum condition for the highest sensitivity is obtained. Probe #3 shows a higher sensitivity compared to probe #1 and it is superior to probe #2 because it operates in a fog-free condition. Finally, the calibration curve for each probe is given that can be used for the operation of the probe as a humidity sensor.

Golnabi, H.

2012-11-01

427

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

428

Validation of refractive index structure parameter estimation for certain infrared bands.  

PubMed

Variation of the atmospheric refraction index due to turbulent fluctuations is one of the key factors that affect the performance of electro-optical and infrared systems and sensors. Therefore, any prior knowledge about the degree of variation in the refractive index is critical in the success of field studies such as search and rescue missions, military applications, and remote sensing studies where these systems are used frequently. There are many studies in the literature in which the optical turbulence effects are modeled by estimation of the refractive index structure parameter, C(n)(2), from meteorological data for all levels of the atmosphere. This paper presents a modified approach for bulk-method-based C(n)(2) estimation. According to this approach, conventional wind speed, humidity, and temperature values above the surface by at least two levels are used as input data for Monin-Obukhov similarity theory in the estimation of similarity scaling constants with a finite difference approximation and a bulk-method-based C(n)(2) estimation. Compared with the bulk method, this approach provides the potential for using more than two levels of standard meteorological data, application of the scintillation effects of estimated C(n)(2) on the images, and a much simpler solution than traditional ones due to elimination of the roughness parameters, which are difficult to obtain and which increase the complexity, the execution time, and the number of additional input parameters of the algorithm. As a result of these studies, Atmospheric Turbulence Model Software is developed and the results are validated in comparison to the C(n)(2) model presented by Tunick. PMID:23669824

Sivasl?gil, Mustafa; Erol, Cemil Berin; Polat, Özgür Murat; Sar?, Hüseyin

2013-05-10

429

Higher-order nonlinearity of refractive index: The case of argon  

NASA Astrophysics Data System (ADS)

The nonlinear coefficients, n4, of the time-dependent refractive index for argon are calculated in the non-resonant optical regime. Second-order polynomial fitting of DC-Kerr, ?(2)(-?; ?, 0, 0), electric field induced second harmonic generation (ESHG), ?(2)(-2?; ?, ?, 0), and static second-order hyperpolarizability, ?(2)(0; 0, 0, 0), is performed using an auxiliary electric field approach to obtain the corresponding fourth-order optical properties. A number of basis sets are investigated for the fourth-order hyperpolarizability processes at 800 nm at coupled cluster singles and doubles level of theory, starting with the t-aug-cc-pV5Z basis set and expanding that basis set by adding diffuse functions and polarization functions. Comparison shows that the results obtained with the t-aug-cc-pV5Z basis are in very good agreement with the results obtained using the q-aug-cc-pV5Z, t-aug-cc-pV6Z, and q-aug-cc-pV6Z basis sets. To calculate the nonlinear refractive index n4, an approximate formula is suggested which expresses the related degenerate six-wave mixing coefficient, ?(4)(-?; ?, -?, ?, -?, ?), in terms of the DC-Kerr, ?(4)(-?; ?, 0, 0, 0, 0), ESHG, ?(4)(-2?; ?, ?, 0, 0, 0), and the static fourth-order hyperpolarizability coefficients. The higher-order nonlinear refractive index n4 is found to be positive over the wavelengths 300 nm-2000 nm. In the infrared spectral range, the obtained values of n4 are in qualitative agreement with the results of Kramers-Kronig-based calculations.

Tarazkar, Maryam; Romanov, Dmitri A.; Levis, Robert J.

2014-06-01

430

Complex Refractive Index of Titan's Aerosol Analogues (in the 200-1000 NM Range)  

NASA Astrophysics Data System (ADS)

Chemistry taking place in the upper atmosphere of Titan evolve to the production of heavier C-H-N organic compounds who form the particles of the haze layers that hide Titan's surface. Among the parameters involved in the different physical models, the complex refractive index of Titan's aerosols is one of the most critical due to the influence that the chemical composition and structural organization has on its parameters. It is therefore useful to have a correct estimation of their values. The first laboratory experiment was carried out by Khare et al. (1984) where they determined these parameters for a product supposed to be a material that well reproduced the Titan's aerosols. It has to be appreciated the effort of Sagan group in performing these measurements, but it has to be also recognized that the fitted values can carry a great uncertainty. Nevertheless, these results have been used during fifteen years by several investigators and have formed the basis for a long series of calculations and photochemical models, even when a correction factor is always necessary to accomplish a good fit of the data. In the frame of a program for getting characteristics of Titan's aerosol analogues, measurements of the complex refractive index were done (Coll et al., 1999). The results showed no relationship with previous studies, and made us to establish a protocol to initiate a detailed study of these optical characteristics of analogues produced under more realistic and well controlled conditions. Finally we present here sets of graphics for transmission, reflectance, and final determinations of refractive index and extinction coefficient with error bars, assuming thickness uncertainties and porosity effects modeling. Critical reading of these graphs will be exposed (how the optical properties of these aerosols can influence the matching of the observed geometric albedo spectrum...).

Coll, P.; Ramirez, S. I.; da Silva, A.; Lafait, J.; Navarro-Gonzalez, R.; Raulin, F.

1999-09-01

431

Direct measurement of the complex refractive index of thin foils in the XUV spectral range by point diffraction interferometry  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate the application of point diffraction interferometry to determine the complex refractive index of thin foils in the extreme ultraviolet spectral range. Results are cross-checked by an independent interferometric measurement of the refractive index and a direct transmission measurement of the foils. As the light source, we apply high-order harmonics of a titanium-sapphire laser generated in a gas jet. This interferometric method has the advantage to simultaneously and directly deliver the refractive and absorptive part of the refractive index without relying on the Kramers-Kronig relations or the Fresnel equations. We present results for a set of materials (aluminum, silicon, germanium, boron, and parylene), which are of interest for the design of bandpass filters or multilayer coatings.

Hemmers, D.; Benzid, M.; Pretzler, G.

2012-07-01

432

SELFAS2: Radio emission from cosmic ray air showers. Effect of realistic air refractive index  

NASA Astrophysics Data System (ADS)

Using the simulation code SELFAS2, we present predictions of the radio signal emitted by extensive air showers (EAS) during their development in the atmosphere. The radio emission in the MHz range coming from air showers is the superposition of two mechanisms: the variation of the transverse current due to the systematic opposite drift of electrons and positrons in the Earth's magnetic field, and the variation of the charge excess due to the electrons in excess in the shower front. In this paper, we stress particularly the effect of the realistic air refractive index on the radio signal predicted by SELFAS2.

Marin, Vincent

2013-05-01

433

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

434

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

435

Structural properties of aqueous metoprolol succinate solutions. Density, viscosity, and refractive index at 311 K  

NASA Astrophysics Data System (ADS)

Density, viscosity and refractive index of aqueous solutions of metoprolol succinate of different concentrations (0.005-0.05 mol dm-3) were measured at 38°C. Apparent molar volume of resultant solutions were calculated and fitted to the Masson's equation and apparent molar volume at infinite dilution was determined graphically. Viscosity data of solutions has been fitted to the Jone-Dole equation and viscosity A- and B-coefficients were determined graphically. Physicochemical data obtained were discussed in terms of molecular interactions.

Deosarkar, S. D.; Kalyankar, T. M.

2013-06-01

436

Dispersion-equation coefficients for the refractive index and birefringence of calcite and quartz crystals  

NASA Astrophysics Data System (ADS)

The refractive index, birefringence and their dispersions are analyzed accurately in a physically meaningful model of a dispersion equation having only five coefficients for the calcite and quartz crystals. This dispersion equation is based on the average electronic absorption gap in the UV region and the effective lattice resonance absorption gap in the IR region. The five coefficients of the dispersion equation are different for each fundamental parameters. The dispersion equation for the birefringence leads to represent a standardized equation describing the birefringence of all optical materials.

Ghosh, Gorachand

1999-05-01

437

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

NASA Astrophysics Data System (ADS)

The nonlinear analysis of slow-wave electron cyclotron masers (ECM) based on anomalous Doppler effect in a slab waveguide is presented. A method of tapered refractive index (TRI) is proposed to enhance the efficiency of slow-wave ECM. The numerical calculations show that the TRI method can significantly enhance the efficiency of slow-wave ECM with the frequency ranging from the microwave to terahertz band. The effect of beam velocity spread on the efficiency has also been studied. Although the velocity spread suppresses the efficiency significantly, a great enhancement of efficiency can still be introduced by the TRI method.

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

2013-04-01

438

Effect of tissue fluid on accurate determination of the complex refractive index of animal tissue.  

PubMed

We investigate the effect of tissue fluid on the measurement of complex refractive index (RI) of animal tissue. A new model is proposed and verified through experimental results of simulation samples made of glycerol and methyl-red-doped poly(methyl methacrylate). Coupled with polarized optical reflectance measurements performed on several kinds of animal muscle tissues, RIs were resolved using the new model. We find that the tissue fluid existing at the prism-sample interface is unavoidable. We also find that with a change of proportion of the tissue fluid, the RI of muscle tissue can still be measured using the new model. PMID:22894483

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

2012-07-01

439

High-performance liquid chromatographic determination of glycogen in sea urchin gonads with refractive index detection.  

PubMed

A high-performance liquid chromatographic method using refractive index detection for the determination of glycogen in sea urchin (Paracentrotus lividus) gonads is developed. After alkaline digestion with sodium carbonate, samples are adjusted to pH 4.6 with citric acid and incubated with amyloglucosidase to hydrolyze the glycogen. The resulting glucose is determined using a Spherisorb NH2 column as the stationary phase and an acetonitrile-water mixture (80:20, v/v) as the mobile phase. The relative standard deviation (%) was 3.57, the limit of detection was 40.1 microg/mL, and the recovery percentage was 97.2%. PMID:11011721

López-Hernández, J; González-Castro, M J; Pereda-González, M

2000-09-01

440

Miniature highly-birefringent microfiber loop with extremely-high refractive index sensitivity.  

PubMed

A miniature polarimetric interferometer with the twist of a highly-birefringent microfiber is demonstrated. Good transmission spectral characteristics, which are co-governed by the birefringence and the twist degree of the microfiber, are investigated. The structure exhibits extremely-high sensitivity of around 24,373 nm per refractive-index unit and excellent temperature stability of better than 0.005 nm/°C. Featured with compactness, reconfigurability, stability, robustness, and compatibility with other fiberized components, our device has potential in tunable filtering, sensing, multi-wavelength lasing, and etc. PMID:22535109

Sun, Lipeng; Li, Jie; Tan, Yanzhen; Shen, Xiang; Xie, Xiaodong; Gao, Shuai; Guan, Bai-Ou