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1

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

2

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

PubMed

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

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

2001-08-01

3

Refractive index of alcohol nonionics  

Microsoft Academic Search

Refractive index is a rapid and consistent method of analysis for alcohols and nonionics from normal alcohols and ethylene\\u000a oxide. Correlations of refractive index with hydroxyl number of alcohols and nonionics are excellent and measurement error\\u000a is considerably lower for refractive index. Refractive index affords a measurement of the amount of ethylene oxide in nonionics\\u000a and can be used as

D. R. Weimer; L. D. Lindemuth; W. L. Groves

1967-01-01

4

Increased Catastrophic-Optical-Damage Output Power for High-Power Semiconductor Lasers Coated with High-Refractive-Index Films  

Microsoft Academic Search

Mirror facet coating with a high-refractive-index film such as TiO2 and Ta2O5 is proposed to obtain high-power short-wavelength semiconductor lasers. A drastic increase in the output power attainable before catastrophic optical damage occurs is theoretically predicted for such a laser without the need to decrease facet reflectivity. This increase is shown to originate from destructive interference of laser light fields

Yoshiyasu Ueno

1998-01-01

5

Fiber optic refractive index monitor  

DOEpatents

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

Weiss, Jonathan David (Albuquerque, NM)

2002-01-01

6

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

7

Refractive Index Enhancement in Gases.  

National Technical Information Service (NTIS)

In this project, we have been investigation a new approach for manipulating the refractive index of a gas while maintaining vanishing absorption of the beam. We have recently experimentally demonstrated the key ingredients of this approach in Rubidium vap...

D. Sikes D. D. Yavuz N. Proite T. Green Z. Simmons

2012-01-01

8

Index of Refraction without Geometry  

ERIC Educational Resources Information Center

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

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

2006-01-01

9

Index of Refraction without Geometry  

ERIC Educational Resources Information Center

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

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

2006-01-01

10

Refractive index measurement using comparative interferometry  

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

11

Refractive Index of Sodium Iodide  

SciTech Connect

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

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

2012-01-01

12

Refractive Index of the Drifting Plasma.  

National Technical Information Service (NTIS)

The refractive index of drifting plasma is derived from the solution of a modified wave equation. The new refractive index is reduced in terms of stationary plasma parameters and its usefulness is outlined. (Author)

P. K. Shukla R. N. Singh R. P. Singh

1970-01-01

13

Refractive index change in dissociating shocked benzene  

NASA Astrophysics Data System (ADS)

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

Erskine, D. J.

1994-06-01

14

Refractive index change in dissociating shocked benzene  

SciTech Connect

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

Erskine, D.J.

1994-06-01

15

Measurement of refractive index of PF5060  

Microsoft Academic Search

For optical studies of boiling heat transfer process, it is essential that the refractive index and its dependence on temperature for the test liquid be known. In this work a simple set-up was built to measure the refractive index of Fluorinert Liquid PF-5060 with temperature compensation and temperature control. The pinhole laser light beam was used for determining the refraction

D. Qiu; V. K. Dhir

1999-01-01

16

Measurement of the refractive index and thermal refractive index coefficients of Nd:YAP crystal  

Microsoft Academic Search

The principal refractive indices of yttrium aluminate crystal doping with 1-wt. % neodymium (Nd:YAP) have been measured by a minimum deviation method for the wavelengths 0.5398, 0.6328, and 1.0795 μm in the temperature range of 289--435 K. The thermal refractive index coefficients have been obtained at these wavelengths, and they are all positive and slightly decrease with increased wavelength. The

Zhengdong Zeng; Hongyuan Shen; Miaoliang Huang; Hao Xu; Ruirong Zeng; Yuping Zhou; Guifang Yu; Chenghui Huang

1990-01-01

17

Negative refractive index in chiral metamaterials.  

PubMed

We experimentally demonstrate a chiral metamaterial exhibiting negative refractive index at terahertz frequencies. The presence of strong chirality in the terahertz metamaterial lifts the degeneracy for the two circularly polarized waves and allows for the achievement of negative refractive index without requiring simultaneously negative permittivity and negative permeability. The realization of terahertz chiral negative index metamaterials offers opportunities for investigation of their novel electromagnetic properties, such as negative refraction and negative reflection, as well as important terahertz device applications. PMID:19257274

Zhang, Shuang; Park, Yong-Shik; Li, Jensen; Lu, Xinchao; Zhang, Weili; Zhang, Xiang

2009-01-12

18

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

19

Demonstration of optical interference filters utilizing tunable refractive index layers.  

PubMed

Optical interference filters utilizing tunable refractive index layers are shown to have higher spectral fidelity as compared to conventional filters consisting of non-tunable refractive index layers. To demonstrate this increase in spectral fidelity, we design and compare a variety of optical interference filters employing both tunable and non-tunable refractive index layers. Additionally, a five-layer optical interference filter utilizing tunable refractive index layers is designed and fabricated for use with a Xenon lamp to replicate the Air Mass 0 solar irradiance spectrum and is shown to have excellent spectral fidelity. PMID:21165093

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

2010-11-01

20

Refraction in Media with a Negative Refractive Index  

Microsoft Academic Search

We show that an electromagnetic (EM) wave undergoes negative refraction at the interface between a positive and negative refractive index material, the latter being a properly chosen photonic crystal. Finite-difference time-domain (FDTD) simulations are used to study the time evolution of an EM wave as it hits the interface. The wave is trapped temporarily at the interface, reorganizes, and, after

S. Foteinopoulou; E. N. Economou; C. M. Soukoulis

2003-01-01

21

Atmospheric stability index using radio occultation refractivity profiles  

NASA Astrophysics Data System (ADS)

A new stability index based on atmospheric refractivity at ~500 hPa level and surface measurements of temperature, pressure and humidity is formulated. The new index named here as refractivity based lifted index (RLI) is designed to give similar results as traditionally used lifted index derived from radiosonde profiles of temperature, pressure and humidity. The formulation of the stability index and its comparison with the traditional temperature profile based lifted index (LI) is discussed. The index is tested on COSMIC radio occultation derived refractivity profiles over Indian region. The forecast potential of the new index for rainfall on 2°×2° latitude-longitude spatial scale with lead time of 3-24 hours indicate that the refractivity based lifted index works better than the traditional temperature based lifted index for the Indian monsoon region. Decreasing values of RLI tend to give increasing rainfall probabilities.

Jagadheesha, D.; Manikiam, B.; Sharma, Neerja; Pal, P. K.

2011-04-01

22

Measurements of the Refractive Index of Films  

Microsoft Academic Search

The refractive index of a film of transparent or translucent material may be determined by immersing the film in a suitable liquid mixture and observing the intensity of light reflected from the surface of the specimen. The composition of the immersion liquid is varied, and a record is made of its refractive index (measured on a refractometer) and of the

Fred W. Billmeyer

1947-01-01

23

Photon mass and negative index of refraction  

Microsoft Academic Search

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

M. Grado-Caffaro

2007-01-01

24

Refractive-index-based optofluidic particle manipulation  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

25

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

26

Refraction in Media with a Negative Refractive Index  

Microsoft Academic Search

We show that an electromagnetic (EM) wave undergoes negative refraction at\\u000athe interface between a positive and negative refractive index material. Finite\\u000adifference time domain (FDTD) simulations are used to study the time evolution\\u000aof an EM wave as it hits the interface. The wave is trapped temporarily at the\\u000ainterface and after a long time, the wave front moves

S. Foteinopoulou; E. N. Economou; C. M. Soukoulis

2003-01-01

27

A terahertz metamaterial with unnaturally high refractive index.  

PubMed

Controlling the electromagnetic properties of materials, going beyond the limit that is attainable with naturally existing substances, has become a reality with the advent of metamaterials. The range of various structured artificial 'atoms' has promised a vast variety of otherwise unexpected physical phenomena, among which the experimental realization of a negative refractive index has been one of the main foci thus far. Expanding the refractive index into a high positive regime will complete the spectrum of achievable refractive index and provide more design flexibility for transformation optics. Naturally existing transparent materials possess small positive indices of refraction, except for a few semiconductors and insulators, such as lead sulphide or strontium titanate, that exhibit a rather high peak refractive index at mid- and far-infrared frequencies. Previous approaches using metamaterials were not successful in realizing broadband high refractive indices. A broadband high-refractive-index metamaterial structure was theoretically investigated only recently, but the proposed structure does not lend itself to easy implementation. Here we demonstrate that a broadband, extremely high index of refraction can be realized from large-area, free-standing, flexible terahertz metamaterials composed of strongly coupled unit cells. By drastically increasing the effective permittivity through strong capacitive coupling and decreasing the diamagnetic response with a thin metallic structure in the unit cell, a peak refractive index of 38.6 along with a low-frequency quasi-static value of over 20 were experimentally realized for a single-layer terahertz metamaterial, while maintaining low losses. As a natural extension of these single-layer metamaterials, we fabricated quasi-three-dimensional high-refractive-index metamaterials, and obtained a maximum bulk refractive index of 33.2 along with a value of around 8 at the quasi-static limit. PMID:21331038

Choi, Muhan; Lee, Seung Hoon; Kim, Yushin; Kang, Seung Beom; Shin, Jonghwa; Kwak, Min Hwan; Kang, Kwang-Young; Lee, Yong-Hee; Park, Namkyoo; Min, Bumki

2011-02-17

28

Refractive index of silicon at ? ray energies.  

PubMed

For x rays the real part of the refractive index, dominated by Rayleigh scattering, is negative and converges to zero for higher energies. For ? rays a positive component, related to Delbrück scattering, increases with energy and becomes dominating. The deflection of a monochromatic ? beam due to refraction was measured by placing a Si wedge into a flat double crystal spectrometer. Data were obtained in an energy range from 0.18 MeV to 2 MeV. The data are compared to theory, taking into account elastic and inelastic Delbrück scattering as well as recent results on the energy dependence of the pair creation cross section. Probably a new field of ? optics with many new applications opens up. PMID:22681083

Habs, D; Günther, M M; Jentschel, M; Urban, W

2012-05-01

29

Quantum storage via refractive-index control  

SciTech Connect

Off-resonant Raman interaction of a single-photon wave packet and a classical control field in an atomic medium with controlled refractive index is investigated. It is shown that a continuous change of refractive index during the interaction leads to the mapping of a single photon state to a superposition of atomic collective excitations (spin waves) with different wave vectors and vice versa. The suitability of refractive-index control for developing multichannel quantum memories is discussed and possible schemes of implementation are considered.

Kalachev, Alexey [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States); Zavoisky Physical-Technical Institute of the Russian Academy of Sciences, Sibirsky Trakt 10/7, Kazan, 420029 (Russian Federation); Kocharovskaya, Olga [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States)

2011-05-15

30

Quantum storage via refractive-index control  

NASA Astrophysics Data System (ADS)

Off-resonant Raman interaction of a single-photon wave packet and a classical control field in an atomic medium with controlled refractive index is investigated. It is shown that a continuous change of refractive index during the interaction leads to the mapping of a single photon state to a superposition of atomic collective excitations (spin waves) with different wave vectors and vice versa. The suitability of refractive-index control for developing multichannel quantum memories is discussed and possible schemes of implementation are considered.

Kalachev, Alexey; Kocharovskaya, Olga

2011-05-01

31

Ultrasensitive photonic crystal fiber refractive index sensor.  

PubMed

We introduce a microfluidic refractive index sensor based on a directional coupler architecture using solid-core photonic crystal fibers. The sensor achieves very high sensitivity by coupling the core mode to a mode in the adjacent fluid-filled waveguide that is beyond modal cutoff, and with strong field overlap. We demonstrate the device through the selective infiltration of a single hole with fluid along a microstructured optical fiber. A detection limit of 4.6x10(-7) refractive index units has been derived from measurements with a sensitivity of 30,100 nm per refractive index unit, which is the highest for a fiber device to date. PMID:19183645

Wu, Darran K C; Kuhlmey, Boris T; Eggleton, Benjamin J

2009-02-01

32

Measurement of the refractive index and thermal refractive index coefficients of Nd:YAP crystal  

SciTech Connect

The principal refractive indices of yttrium aluminate crystal doping with 1-wt. % neodymium (Nd:YAP) have been measured by a minimum deviation method for the wavelengths 0.5398, 0.6328, and 1.0795 {mu}m in the temperature range of 289--435 K. The thermal refractive index coefficients have been obtained at these wavelengths, and they are all positive and slightly decrease with increased wavelength. The constants of the single term Sellmeier equation are also given for the 273--420 K temperature range. These constants are in linear relationship with temperature in the 4 {times} 10{sup {minus}3} error range.

Zeng, Z.; Shen, H.; Huang, M.; Xu, H.; Zeng, R.; Zhou, Y.; Yu, G.; Huang, C. (Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, China (CN))

1990-03-20

33

Measurement of the refractive index and thermal refractive index coefficients of Nd:YAP crystal.  

PubMed

The principal refractive indices of yttrium aluminate crystal doping with 1-wt.% neodymium (Nd:YAP) have been measured by a minimum deviation method for the wavelengths 0.5398, 0.6328, and 1.0795 microm in the temperature range of 289-435 K. The thermal refractive index coefficients have been obtained at these wavelengths, and they are all positive and slightly decrease with increased wavelength. The constants of the single term Sellmeier equation are also given for the 273-420 K temperature range. These constants are in linear relationship with temperature in the 4 x 10(-3) error range. PMID:20562993

Zeng, Z; Shen, H; Huang, M; Xu, H; Zeng, R; Zhou, Y; Yu, G; Huang, C

1990-03-20

34

Metamaterials with gradient negative index of refraction.  

PubMed

We propose a new metamaterial with a gradient negative index of refraction, which can focus a collimated beam of light coming from a distant object. A slab of the negative refractive index metamaterial has a focal length that can be tuned by changing the gradient of the negative refractive index. A thin metal film pierced with holes of appropriate size or spacing between them can be used as a metamaterial with the gradient negative index of refraction. We use finite-difference time-domain calculations to show the focusing of a plane electromagnetic wave passing through a system of equidistantly spaced holes in a metal slab with decreasing diameters toward the edges of the slab. PMID:17912287

Pinchuk, Anatoliy O; Schatz, George C

2007-10-01

35

Optics Problem: Index of Refraction  

NSDL National Science Digital Library

A beam of parallel rays propagating to the right is refracted upon entering and leaving another medium. Both the position of the source and the angle of the source can be adjusted by click-dragging the circular hotspots. Angles may also be measured by click- dragging away from the hotspots.

Christian, Wolfgang; Belloni, Mario

2007-03-03

36

Refractive index matching and clear emulsions.  

PubMed

Refractive index (RI) matching is a unique way of making clear emulsions to meet market trends. However, RI matching has not been sufficiently investigated in terms of physical principles and methodologies. Snell's law (n2 sin r2= n1 sin r1) is applicable to cosmetic emulsions. When oil phase and water phase have equal RI (n2 = n1) values, light will not bend as it strikes obliquely at the emulsion interface. Instead, light is transmitted through the emulsion without refraction, which produces clarity. Theoretical RI values in solution can be calculated with summation of the product of the weight percentage and refractive index of each ingredient (RI(mix) = [W1 x n1 + W2 x n2 + W3 x n3 + + Wn x nn]Wtau). Oil-phase RI values are normally at 1.4 or higher. Glycols are used to adjust the water phase RI, since they typically have larger RI values than water. Noticeable deviations from calculated RI values are seen in experimentally prepared solutions. Three basic deviation types are observed: negative, positive, and slightly negative or positive, which can occur in glycol aqueous solutions at different concentrations. The deviations are attributed to changes in molecular interaction between molecules in solution, which can lead to changes in specific gravity. Negative RI deviation corresponds to a decrease in specific gravity, and positive RI deviation corresponds to an increase in specific gravity. RI values will deviate from calculated values since an increase or decrease in specific gravity leads to a change in optical density. PMID:16130046

Sun, James Ziming; Erickson, Michael C E; Parr, James W

37

Sensitivity enhanced long-period grating refractive index sensor with refractive index modified cladding layer  

NASA Astrophysics Data System (ADS)

A sensitivity enhanced long-period grating (LPG) refractive index sensor is proposed and studied by using the LP model. In the simulation, the cladding layer of the LPG is assumed to be partially removed and then deposit a sensitivity enhancement layer (SEL) with a higher refractive index. The effects of the thickness of the original cladding material, and the thickness and refractive index of the SEL layer on the LPG transmission spectrum notch wavelength shift as a function of the ambient refractive index change are reported. The LPG sensor performance depends on the phase match condition of the core mode and cladding mode coupling in the LPG structure and the dependence of the effective index of the cladding mode on the thickness of the original cladding material, and the thickness and refractive index of the SEL layer. The structure modified cladding layer moves the work point of the long period grating to the cladding mode reorganization zone, where the cladding mode effective refractive index changes rapidly upon the LPG waveguide parameter. Proper selection of parameters of the cladding layer can be applied to enhance the modulation of the effective index of the cladding mode by the ambient refractive index through the evanescent field and thus construct sensitivity enhanced ambient refractive index sensors.

Yang, Jian; Xu, Chang-Qing; Li, Yingfu

2005-09-01

38

The refractive index of thin solid films  

Microsoft Academic Search

A fundamental optics experiment in the school\\/undergraduate physics laboratory is the investigation of the dispersion of visible light using a prism spectrometer. The refractive index, n, of the prism material can be calculated for various wavelengths with the help of the relation n=sin((A+Dmin)\\/2)\\/sin(A\\/2), where A is the refracting angle of the prism and Dmin is the angle of minimum deviation.

S. K. J. Al-Ani; J. Beynon

1985-01-01

39

Refractive Index Enhancement in Atomic Media  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a scheme where a laser beam experiences refractive index enhancement with vanishing absorption. The essential idea is to excite two Raman resonances with appropriately chosen strong laser beams in a far-off resonant atomic system. We have performed our experiments both in vapor cells and in ultracold atomic clouds. Additionally, we discuss a new scheme that achieves giant Kerr nonlinearities using refractive index enhancement. This scheme does not require an intense coupling laser and has the potential to produce all-optical switches and distributed Bragg reflectors at a total energy requirement of tens of photons per atomic cross section.

Proite, Nicholas; Sikes, Daniel; Yavuz, Deniz

2010-03-01

40

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

Microsoft Academic Search

The thermal expansion and temperature dependence of the refractive index in gradient index glass have been investigated. These two thermal properties have been modeled as functions of local glass composition within the gradient index region. Additive relationships have been developed for gradient index glass from previous work done on homogeneous glass modeling. Computer programs have been written to calculate the

Paul Oliver McLaughlin

1982-01-01

41

Negative refractive index in hydrodynamical systems  

NASA Astrophysics Data System (ADS)

We discuss the presence of exotic electromagnetic phenomena in systems with finite charge density which are described by hydrodynamics. We show that such systems generically have negative refractive index for low frequencies electromagnetic waves, i.e. the energy flux and the phase velocity of the wave propagate in opposite directions. We comment on possible phenomenological applications, focusing on the Quark Gluon Plasma.

Amariti, Antonio; Forcella, Davide; Mariotti, Alberto

2013-01-01

42

Refractive Index Formulae for Radio Waves  

Microsoft Academic Search

The radio refractive index formula adopted in 1963 by the International Union of Geodesy and Geophysics (IUGG) and the International Association of Geodesy (IAG) is being reviewed. Forty years ago, this formula was essential for the reduction of distances measured with microwave EDM instruments. Since then, long-range EDM has been replaced by the Global Positioning System (GPS). Today, the formulae

Jean M. RÜEGER

2002-01-01

43

Experimental demonstration of negative index of refraction  

Microsoft Academic Search

We introduce an improved and simplified structure made of periodic arrays of pairs of H-shaped metallic wires that offer a potentially simpler approach in building negative-index materials. Using simulations and microwave experiments, we have investigated the negative-index n properties of these structures. We have measured experimentally both the transmittance and the reflectance properties and found unambiguously that a negative refractive

Jiangfeng Zhou; Thomas Koschny; Lei Zhang; Gary Tuttle; Costas M. Soukoulis

2006-01-01

44

The refractive index of thin solid films  

NASA Astrophysics Data System (ADS)

A fundamental optics experiment in the school/undergraduate physics laboratory is the investigation of the dispersion of visible light using a prism spectrometer. The refractive index, n, of the prism material can be calculated for various wavelengths with the help of the relation n=sin((A+Dmin)/2)/sin(A/2), where A is the refracting angle of the prism and Dmin is the angle of minimum deviation. With reasonable care it is possible to verify that n and lambda satisfy a simplified Cauchy relation of the form n=L+M lambda -2, where L and M are constants characteristic of the prism material.

Al-Ani, S. K. J.; Beynon, J.

1985-11-01

45

Multiwavelength optical fiber refractive index profiling  

NASA Astrophysics Data System (ADS)

Fourier transform spectroscopy and interference microscopy are combined to provide the world's first multi-wavelength optical fiber refractive index profile (RIP) measurements. The RIP and its spectral dependence are obtained with submicron spatial resolution across an octave stretching from about 500 nm to the 1 micron operating band of Yb-doped fiber lasers and amplifiers. In contrast to commercial Refracted Near Field (RNF) technology, which measures at a cleave, the technique described here measures transversely through the side of an uncleaved fiber, enabling measurements of axial fiber RIP variations found in fiber gratings, physical tapers, and fusion splices.

Yablon, Andrew D.

2010-02-01

46

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.

47

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

48

Periodic ferrite semiconductor layered composite with negative index of refraction  

Microsoft Academic Search

We have studied the index of refraction of periodic layered semiconductor-ferrite composite. Both the transmission matrix analysis and full-wave simulations confirm the existence of a negative index of refraction in the composite. We find that the magnitude of the negative index of refraction and its frequency range depend on the ratio of the semiconductor and ferrite layer thicknesses and the

Rui-Xin Wu; Tianen Zhao; John Q. Xiao

2007-01-01

49

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

50

Refractive index profile and geometry measurements in multicore fibres  

NASA Astrophysics Data System (ADS)

The refracted near-field technique (RNF) has been applied to the measurement of the refractive index profiles in multicore fibres (MCF). The fibre core diameter and the intercore distances have been determined.

Conde, R.; Depeursinge, C.; Gisin, B.; Gisin, N.; Groebli, B.

1996-05-01

51

The refractive index of human hemoglobin in the visible range  

NASA Astrophysics Data System (ADS)

Because the refractive index of hemoglobin in the visible range is sensitive to the hemoglobin concentration, optical investigations of hemoglobin are important for medical diagnostics and treatment. Direct measurements of the refractive index are, however, challenging; few such measurements have previously been reported, especially in a wide wavelength range. We directly measured the refractive index of human deoxygenated and oxygenated hemoglobin for nine wavelengths between 400 and 700 nm for the hemoglobin concentrations up to 140 g l-1. This paper analyzes the results and suggests a set of model functions to calculate the refractive index depending on the concentration. At all wavelengths, the measured values of the refractive index depended on the concentration linearly. Analyzing the slope of the lines, we determined the specific refraction increments, derived a set of model functions for the refractive index depending on the concentration, and compared our results with those available in the literature. Based on the model functions, we further calculated the refractive index at the physiological concentration within the erythrocytes of 320 g l-1. The results can be used to calculate the refractive index in the visible range for arbitrary concentrations provided that the refractive indices depend on the concentration linearly.

Zhernovaya, O.; Sydoruk, O.; Tuchin, V.; Douplik, A.

2011-07-01

52

Nondestructive measurement of refractive index profile for holey fiber preforms.  

PubMed

A non-destructive technique is presented to determine the refractive index profile of holey fiber preforms. The holes are filled with index matching oil and the holey preform deflection data is measured. An improved optical path-length formula and back projection method is used to reconstruct the two-dimensional filled holey fiber preform refractive index distribution. PMID:19471359

Zhao, Yucheng; Lyytikainen, Katja; van Eijkelenborg, Martijn; Fleming, Simon

2003-10-01

53

Characterization of nanolayer LPG refractometer according surrounding refractive index  

NASA Astrophysics Data System (ADS)

In this work the behavior of an optical fiber Long Period Grating (LPG) refractometer with the variations of the surrounding refractive index is discussed. The objective is to characterize optical fiber refractometers sensitive to surrounding refractive index, higher and lower than the cladding. For values of surrounding refractive index higher than the cladding, the LPG does not show enough sensitivity. For this reason, a nanolayer of an organic material was coated onto the fiber, using the Langmuir-Blodgett technique. We characterized LPG covered with different nanolayers thickness (110 and 120 nm) relatively to changes in surrounding refractive index.

Simões, E.; Abe, I.; Oliveira, J.; Pinto, J. L.; Caldas, P.; Frazão, O.

2010-09-01

54

Negative Index of Refraction in Anisotropic Nonmagnetic Materials  

Microsoft Academic Search

We analyze the possibility of negative refractive index and\\/or negative refraction of energy flow in a uniaxial nonmagnetic dielectric material. It is shown that an extraordinary p-polarized electromagnetic wave can exhibit a negative refraction provided the parallel (with respect to the optical axis) and perpendicular components of the permittivity have different signs. Such a situation can be encountered near phonon

V. Dvo?ák; P. Kužel

2006-01-01

55

Negative Index of Refraction in Anisotropic Nonmagnetic Materials  

Microsoft Academic Search

We analyze the possibility of negative refractive index and\\/or negative refraction of en- ergy flow in a uniaxial nonmagnetic dielectric material. It is shown that an extraordinary p-polarized electromagnetic wave can exhibit a negative refraction provided the parallel (with respect to the optical axis) and perpendicular components of the permittivity have different signs. Such a situation can be encountered near

V. DVO

56

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

57

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

58

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

59

Ultrafast refractive index control of a terahertz graphene metamaterial  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

60

Refractive Index Profile of Polymeric Fibers Characterized by Micro Interferometry  

NASA Astrophysics Data System (ADS)

Interference microscopy is the only non-destructive method which can measure orientation and crystallinity at different radial positions within a fiber. It has long been used to characterize the radial variation of fiber micro structure. However all past work has not considered fiber-liquid interfacial and fiber interior refraction correctly. The present research has developed a correct ray tracing method which takes consideration of both external and internal refraction. Based on the theory the systematic errors from the past work have been analyzed, and a numerical algorithm is developed to solve the refractive index profile using the correct optical path difference equation. In order to guarantee the precision of data acquisition process a new fringe extraction method based on interference principle has also been developed. The new method has been applied to fibers having either homogeneous or inhomogeneous structures. The experimental results indicate that the new algorithm greatly reduces effects of noise in interference fringe images and increases the accuracy of results. It is also found that the refractive index profile reduced from using this algorithm is adequately independent of immersion medium. The errors observed are almost within the calibration accuracy of the immersion media. When applied to high speed spun PET fibers, some previously unknown structural details have been revealed. The commercial POY (3500m/min.), due to low crystallinity, appears to have convex up refractive index profile n(r). On the other hand the n(r) of the higher speed spun (7000m/min.) fiber has concave down curvature.

Wu, Zhenqiu

61

Nonlinear refractive index of optical crystals  

NASA Astrophysics Data System (ADS)

The nonlinear refractive indices (n2) of a large number of optical crystals have been measured at a wavelength near one micrometer with use of nearly degenerate three-wave mixing. The measurements are compared with the predictions of an empirical formula derived by Boling, Glass, and Owyoung. This formula, which relates n2 to the linear refractive index and its dispersion, is shown to be accurate to within about 30% for materials with nonlinear indices ranging over 3 orders of magnitude. Measurements for a number of binary oxide and fluoride crystals have been analyzed under the assumption that the hyperpolarizability of the anion is much larger than that of the cation. It is found that the hyperpolarizability of oxygen varies by a factor of 10, and that of fluorine varies by a factor of 7, depending on the size of the coordinating cation. This behavior is similar to that of the linear polarizability, although the hyperpolarizability is much more sensitive than the linear polarizability to the identity of the cation. The measured halide ion hyperpolarizabilities for several alkali-halide crystals are in reasonable agreement with recent self-consistent calculations. A semiempirical model was proposed by Wilson and Curtis to account for the dependence of the linear anionic polarizability on the radius of the cation. This model also accounts quite well for the variation of the hyperpolarizability of both fluorine and oxygen, except for cation partners that have filled or unfilled d-electron shells. The nonlinear indices of a number of complex oxides (i.e., those with more than one cation) have been calculated from the partial hyperpolarizabilities deduced from the data for the binary oxides. The calculated and measured values of n2 agree to within an average error of 13%.

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

1989-02-01

62

Optical tomography for smooth-changing refraction index distribution  

Microsoft Academic Search

We propose an algebraic reconstruction method (ART) based on smooth functions to obtain the refraction index distribution of a radially symmetric phase object. Recovering the refraction index of a transversal section enables us to obtain some other physical variables such as temperature, pressure, etc. Considering phase objects with a radially symmetric distribution allows the recovery of information regarding the volumetric

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

2002-01-01

63

Measurement of refractive index using a Michelson interferometer  

Microsoft Academic Search

The Michelson interferometer has long been a popular piece of equipment in the physics undergraduate laboratory. One possible application is the measurement of the refractive index of a thin parallel-side plate of transparent material of known thickness. (Alternatively, if the refractive index is known, the thickness of the plate may be determined.) This is accomplished by using 'white light' fringes

J. J. Fendley

1982-01-01

64

Determination of the refractive index of a bacteriorhodopsin film  

Microsoft Academic Search

The wavelength-dependent refractive index of a bacteriorhodopsin thin film is measured by the use of a modified critical-angle technique. The effect of the host bovine skin gelatin on the refractive index is analyzed. The measured data on the thin film can be useful for system applications. The methods and procedures are generally applicable to any optically absorbing thin films.

Chunping Zhang; Q. Wang Song; Chin-Yu Ku; Richard B. Gross; Robert R. Birge

1994-01-01

65

Evidence of Negative-Index Refraction in Nonlinear Chemical Waves  

Microsoft Academic Search

The negative index of refraction of nonlinear chemical waves has become a recent focus in nonlinear dynamics researches. Theoretical analysis and computer simulations have predicted that the negative index of refraction can occur on the interface between antiwaves and normal waves in a reaction-diffusion (RD) system. However, no experimental evidence has been found so far. In this Letter, we report

Xujin Yuan; Hongli Wang; Qi Ouyang

2011-01-01

66

Negative refractive index in chiral spiral metamaterials at terahertz frequencies  

Microsoft Academic Search

A three-dimensional chiral metamaterial consisting of arrays of the multi-layered mutually twisted metallic spirals is proposed. We theoretically demonstrate such a chiral spiral structure exhibiting negative refractive index at terahertz frequencies. The chirality with varied refractive index can be obtained by change of configurations of the structure. The presented design offers flexibility for investigation of electromagnetic properties of chiral metamaterials

Mingxia He; Jiaguang Han; Zhen Tian; Jianqiang Gu; Qirong Xing

2011-01-01

67

Variations in the index of refraction of the atmosphere  

Microsoft Academic Search

This paper discusses the atmospheric refractive index (a) throughout the year at the surface of the earth and (b) for each season in various air masses. Mean monthly or seasonal values, respectively, are employed. The annual variation in the refractive index at the earth's surface is examined by noting the contributions of the optical and the water vapor terms. The

N. C. Gerson

1948-01-01

68

Refractive index in the viscous quark-gluon plasma  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

69

Refractive index dispersions of liquid crystals  

NASA Astrophysics Data System (ADS)

Refractive indices of two nematic liquid crystals: 5 CB and 5 PCH were measured from 400 to 820 nm region at various temperatures. Results fit the three-band model well. Through these comparisons, the contribution of (sigma) - and (pi) -electrons to the refractive indices and birefringence of uniaxial liquid crystals are evaluated quantitatively. These physical insights are useful for tailoring liquid crystal molecules with proper refractive indices.

Wu, Shin T.; Wu, Chiung S.; Warenghem, W.; Ismaili, M.

1992-10-01

70

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

71

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

NASA Astrophysics Data System (ADS)

This study describes the observation of large induced refractive index changes produced by 157nm excimer laser exposure in high-purity synthetic silica glasses. With 157nm 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.

2006-09-01

72

Refractive index tailoring in congruent Lithium Niobate by ion implantation  

Microsoft Academic Search

Refractive index profiles of ion-implanted Lithium Niobate waveguides are investigated. Z+ and z? congruent Lithium Niobate samples have been implanted with C3+ ions at a fluence of 4×1014 ions\\/cm2. Dark m-lines measurements have been performed on ordinary (no) and extraordinary (ne) indexes for three different wavelengths (532nm, 632.8nm, 818nm) before and after the annealing process. A reconstruction of refractive index

S. Sugliani; M. Bianconi; G. G. Bentini; M. Chiarini; P. De Nicola; G. B. Montanari; A. Menin; A. Malacarne; L. Potì

2010-01-01

73

Ferromagnetic metamaterial with tunable negative index of refraction  

Microsoft Academic Search

We investigate the index of refraction of the ferromagnetic metamaterial, which consists of periodic layered ferrite and semiconductor or metallic mesh. We find that the metamaterial has the negative index; the frequency range and magnitude of the negative index are tunable in applied magnetic fields. The frequency range of the negative index shifts to higher frequencies as the applied magnetic

Da-Yong Zou; Ai-Min Jiang; Rui-Xin Wu

2010-01-01

74

Negative index of refraction in artificial chiral materials  

Microsoft Academic Search

A new class of negative refractive-index metamaterials made of metallic spheres arranged in a three-dimensional lattice of helicoidal symmetry is reported. The studied metamaterial possesses several frequency bands which give rise to negative refraction. The proposed structures constitute a viable solution to realizing optical metamaterials since they can exhibit negative refraction in the frequency region of the surface-plasmon excitations of

Vassilios Yannopapas

2006-01-01

75

Optical tomography for smooth-changing refraction index distribution  

NASA Astrophysics Data System (ADS)

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

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

2002-06-01

76

Metamaterial optical refractive index sensor detected by the naked eye  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

77

Dynamic properties of photonic crystals and their effective refractive index  

NASA Astrophysics Data System (ADS)

The reflection and refraction properties of light at an interface between two media are usually classified as kinematic and dynamic. Both are determined by the refractive indices of the media. The kinematic properties refer to the direction of light propagation, whereas the dynamic properties refer to the polarization, magnitude, and phase changes of the reflected and refracted waves. Metamaterials and photonic crystals are often assigned an effective refractive index defined by their dispersion curves. This work shows for the first time, to our knowledge, that although the kinematic properties are consistent with this index definition, in some cases the dynamic properties are not. This observation has important implications for photonic crystal understanding and design because it shows that their rich physical phenomena cannot always be simplified to a description in terms of an effective refractive index.

Schwartz, Brian T.; Piestun, Rafael

2005-09-01

78

Determining the Thickness and Refractive Index of a Mirror  

ERIC Educational Resources Information Center

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

Uysal, Ahmet

2010-01-01

79

Composite materials with giant anisotropy and negative index of refraction  

Microsoft Academic Search

We demonstrate that a nanostructured plasmonic composite material can show negative index of refraction at infrared and optical frequencies. In contrast to conventional negative refraction materials, our design does not require periodicity and thus is highly tolerant to fabrication defects. Moreover, since the proposed material is intrinsically non-magnetic (mu ? 1), its performance is not limited to proximity of a

Viktor A. Podolskiy; Leo A. Alekseyev; Evgenii E. Narimanov

2005-01-01

80

On the physical origins of the negative index of refraction  

Microsoft Academic Search

The physical origins of negative refractive index are derived from a dilute microscopic model, producing a result that is generalized to the dense condensed phase limit. In particular, scattering from a thin sheet of electric and magnetic dipoles driven above resonance is used to form a fundamental description for negative refraction. Of practical significance, loss and dispersion are implicit in

David W. Ward; Keith A. Nelson; Kevin J. Webb

2005-01-01

81

Z-scan measurement of the nonlinear refractive index of graphene.  

PubMed

Under strong laser illumination, few-layer graphene exhibits both a transmittance increase due to saturable absorption and a nonlinear phase shift. Here, we unambiguously distinguish these two nonlinear optical effects and identify both real and imaginary parts of the complex nonlinear refractive index of graphene. We show that graphene possesses a giant nonlinear refractive index n(2)?10(-7) cm(2) W(-1), almost 9 orders of magnitude larger than bulk dielectrics. We find that the nonlinear refractive index decreases with increasing excitation flux but slower than the absorption. This suggests that graphene may be a very promising nonlinear medium, paving the way for graphene-based nonlinear photonics. PMID:22660052

Zhang, Han; Virally, Stéphane; Bao, Qiaoliang; Ping, Loh Kian; Massar, Serge; Godbout, Nicolas; Kockaert, Pascal

2012-06-01

82

Ferrite based metamaterials with thermo-tunable negative refractive index  

NASA Astrophysics Data System (ADS)

Thermo-tunable negative refractive index (NRI) metamaterials with single- and dual-band based on ferrite have been designed and prepared; the scattering parameters of these metamaterials have been measured at various temperatures to demonstrate the thermo-tunable property. As the temperature increases, the peak value of passband decreases and the passband frequency region shifts to the lower frequency. This temperature dependence is attributed to ferrimagnetic/paramagnetic transition of the ferrites. The thermo-tunable NRI characteristic makes these metamaterials suitable for practical applications in thermo-tunable NRI devices.

Bi, Ke; Dong, Guoyan; Fu, Xiaojian; Zhou, Ji

2013-09-01

83

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

84

Negative index of refraction and distributed Bragg reflectors  

Microsoft Academic Search

The Bragg regime shifts when conventional materials in a multilayer distributed Bragg reflector (DBR) are replaced by artificial materials with the so-called negative index of refraction. This provides an avenue for characterizing the latter class of materials.

Jaline Gerardin; Akhlesh Lakhtakia

2002-01-01

85

Negative refractive index in ferromagnetic semiconductors: experimental verification  

NASA Astrophysics Data System (ADS)

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

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

86

Design of resonators using materials with negative refractive index  

Microsoft Academic Search

By optimizing the design we show that inhomogeneous electromagnetic\\u000aresonators with almost uniform field intensity and up to twice the energy\\u000adensity of conventional structures are possible by exploiting the properties of\\u000anegative refractive index materials. materials. We demonstrate that using\\u000anegative refractive index materials it is possible to make full width at half\\u000amaximum (FWHM) of the transmission coefficient

Petra Schmidt; Ilya Grigorenko; A. F. J. Levi

2007-01-01

87

Determination of the refractive index of a bacteriorhodopsin film.  

PubMed

The wavelength-dependent refractive index of a bacteriorhodopsin thin film is measured by the use of a modified critical-angle technique. The effect of the host bovine skin gelatin on the refractive index is analyzed. The measured data on the thin film can be useful for system applications. The methods and procedures are generally applicable to any optically absorbing thin films. PMID:19855535

Zhang, C; Song, Q W; Ku, C Y; Gross, R B; Birge, R R

1994-09-15

88

Non-magnetic materials with negative refractive index  

NASA Astrophysics Data System (ADS)

We develop a new approach to materials with negative refraction index which can be implemented for optical and infrared frequencies. In contrast to conventional designs which require simultaneously negative dielectric permittivity and magnetic permeability, our system is intrinsically non-magnetic and makes use of an anisotropic dielectric constant to provide negative refractive index in waveguide geometry. The proposed approach is not limited to the proximity of a resonance and thus allows for low loss, critical for super-lensing applications.

Narimanov, Evgenii E.; Alekseyev, Leonid V.; Podolskiy, Viktor A.

2005-08-01

89

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

90

Highly sensitive refractive index sensor based on two cascaded long period gratings with rotary refractive index modulation  

Microsoft Academic Search

We present a refractive index (RI) sensor based on a fiber Mach-Zehnder interferometer, which is realized by two cascaded special long period gratings with rotary refractive index modulation (C-RLPFG). The wavelength shift of the refractometer behaves good linear response in a RI range of 1.3342 to 1.3362, and the sensitivity of 14.5pm\\/mm for 0.01SRI change has been obtained. The sensitivity

Tao Zhu; Yanen Fan; Ming Deng; Yunjiang Rao

2011-01-01

91

Plasmas with index of refraction greater than one  

SciTech Connect

Over the last decade, X-ray lasers in the wavelength range14 - 47 nm have been used to do interferometry of plasmas. Just as for optical interferometry of plasmas, the experimental analysis assumed that the index of refraction is due only to the free electrons. This makes the index of refraction less then one. Recent experiments in Al plasmas have observed fringe lines bend the wrong way as though the electron density is negative. We show how the bound electrons can dominate the index of refraction in many plasmas and make the index greater than one or enhance the index such that one would greatly overestimate the density of the plasma using interferometry.

Nilsen, J; Scofield, J H

2004-06-23

92

Three-dimensional optical metamaterial with a negative refractive index.  

PubMed

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

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

2008-08-11

93

Periodic layered waveguide with negative index of refraction  

Microsoft Academic Search

The authors demonstrate that a negative index of refraction can exist in a periodic layered waveguide composed of natural materials with either permittivity or permeability negative. They find that the negative index depends on component materials, their configurations, and working modes of the waveguide. In the long wave limit, the expressions of the effective permeability and permittivity of the waveguide

Rui-Xin Wu; Tianen Zhao; Ping Chen; Jie Xu; Xinyi Ji

2007-01-01

94

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

Microsoft Academic Search

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

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

2008-01-01

95

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

96

The index of refraction in linear anisotropic media  

NASA Astrophysics Data System (ADS)

We provide an instructive derivation of the index of refraction in linear anisotropic media by assuming that it is possible to consider matter as dipoles that are induced by the action of electromagnetic waves. We show that the index of refraction depends on the polarization of the incident beam by considering that matter can be modelled as oscillating dipoles with different values of the restoring forces that bind electrons to atoms (the Lorentz model). This model allows us to explain the double refraction by taking into account that the components of the dipolar moment produce fields that are out of phase with each other, thus the refracted extraordinary wave changes its direction of propagation compared with that of the ordinary wave. This approach provides an alternative to the usual analysis based on the study of the electric displacement vector. We present the similarities of our analysis with the fruitful Huygens' principle.

Carreño, Fernando; Antón, Miguel

1999-11-01

97

Effect of negative index of refraction in the propagation of electromagnetic waves  

Microsoft Academic Search

Consider a material slab situated between two half free spaces. An electromagnetic waves is obliquely incident on it. We investigate the effect of index of refraction of the material in the transmission of electromagnetic waves. We study three cases of the material: real positive index of refraction, real negative index of refraction and the refractive index is a function of

Muin F. Ubeid; Mohammed M. Shabat

2010-01-01

98

Refractive index measurement in human tissue samples  

NASA Astrophysics Data System (ADS)

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

Tsenova, Vesselina; Stoykova, Elena V.

2003-11-01

99

Annealing induced variation in refractive index of Rhodamine B doped Poly (vinyl) alcohol films  

NASA Astrophysics Data System (ADS)

The present paper reports the influence of fluorescent dye doping on the optical properties, in particular on the refractive index of Poly (vinyl) alcohol (PVA) host matrix. The dye (Rhodamine B) is doped in weight percent ranging from 0 to 2 wt%. It is found that at highest doping wt% (2%), dye molecules segregate to the surface breaking the bonds of the PVA matrix as well as simultaneously forming new bonds, thereby modifying the overall refractive index. Also, annealing of these samples produces a change in the refractive index. The refractive index shows a general decreasing trend with increasing wavelength but with modified values upon changing doping percentage or upon annealing. Overall results are interpreted in terms of bond modifications at the surface and interior of PVA due to the inclusion of Rhodamine B molecules.

Tripathi, J.; Tripathi, S.; Keller, J. M.; Das, K.

2013-05-01

100

Isotropic spiral plasmonic metamaterial for sensing large refractive index change.  

PubMed

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

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

2013-08-15

101

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

102

Evidence of negative-index refraction in nonlinear chemical waves.  

PubMed

The negative index of refraction of nonlinear chemical waves has become a recent focus in nonlinear dynamics researches. Theoretical analysis and computer simulations have predicted that the negative index of refraction can occur on the interface between antiwaves and normal waves in a reaction-diffusion (RD) system. However, no experimental evidence has been found so far. In this Letter, we report our experimental design in searching for such a phenomenon in a chlorite-iodide-malonic acid (CIMA) reaction. Our experimental results demonstrate that competition between waves and antiwaves at their interface determines the fate of the wave interaction. The negative index of refraction was only observed when the oscillation frequency of a normal wave is significantly smaller than that of the antiwave. All experimental results were supported by simulations using the Lengyel-Epstein RD model which describes the CIMA reaction-diffusion system. PMID:21635131

Yuan, Xujin; Wang, Hongli; Ouyang, Qi

2011-05-06

103

Measurements of photoinduced refractive index changes in bacteriorhodopsin films  

NASA Astrophysics Data System (ADS)

We report the pump--probe measurements of nonlinear refractive index changes in photochromic bacteriorhodopsin films. The photoinduced absorption is caused by pump beam at 532 nm and the accompanying refractive index changes are studied using a probe beam at 633 nm. The proposed technique is based on a convenient and accurate determination of optical path difference using digital interferometry-based local fringe shift. The results are presented for the wild-type as well as genetically modified D96N variant of the bacteriorhodopsin.

Banyal, Ravinder Kumar; Raghavendra Prasad, B.

2007-03-01

104

Improved method for measuring refractive index of a medium  

NASA Astrophysics Data System (ADS)

An improved method for measuring the refractive index of a medium is presented. First, the light coming form a circular heterodyne source is incident on the test medium. And, the reflected light passes through an analyzer with the transmission axis at a moderate azimuth angle. Then, the phase variation of the reflected light is measured by the heterodyne interferometric technique. Finally, substituting this phase variation into the equations derived from Fresnel's equations and Jones calculus, we can obtain the refractive index of the test medium.

Su, Der-Chin; Lee, Ju-Yi

1998-06-01

105

Calculation of refractive-index distribution of hexagonal GRIN lenses  

NASA Astrophysics Data System (ADS)

The GRIN lens is widely used in optical communication and imaging systems. Its array can be used to design integrated optic imaging system, especially for hexagonal GRIN. In this paper, the analytic solution of refractive-index distribution of regularly hexagonal GRIN was obtained by separating variables and transforming coordinate. Having been simulated and compared, the correctness of this analytic solution was proved qualitatively and quantitatively. It has great benefit for further research of regular hexagonal GRIN lens and compound eye imaging system. Furthermore, a universal solution of the refractive-index distribution of a regular N-gon (N is even) lens was obtained by this method.

Zhou, Zigang; Zhang, Ren; Chen, Kai

2007-12-01

106

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

SciTech Connect

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

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

1981-09-01

107

Structures with negative index of refraction  

Microsoft Academic Search

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

Costas M. Soukoulis; Jiangfeng Zhou; Thomas Koschny; Lei Zhang; Gary Tuttle

2011-01-01

108

Refractive index and wave vector in passive or active media  

NASA Astrophysics Data System (ADS)

Materials that exhibit loss or gain have a complex-valued refractive index n . Nevertheless, when considering the propagation of optical pulses, using a complex n is generally inconvenient—hence the standard choice of real-valued refractive index, i.e., ns=Re(n2) . However, an analysis of pulse propagation based on the second-order wave equation shows that use of ns results in a wave vector different to that actually exhibited by the propagating pulse. In contrast, an alternative definition nc=Re(n2) , always correctly provides the wave vector of the pulse. Although for small loss the difference between the two is negligible, in other cases it is significant; it follows that phase and group velocities are also altered. This result has implications for the description of pulse propagation in near resonant situations, such as those typical of metamaterials with negative (or otherwise exotic) refractive indices.

Kinsler, Paul

2009-02-01

109

Ink-Jet Printing of Gradient Index of Refraction Lenses.  

National Technical Information Service (NTIS)

This is the Phase I Final Report developed under SBIR contract for topic number SB001-010. The overall technical objective was to design a rapid- prototyping/manufacturing machine capable of fabricating GRIN (gradient index of refraction) lenses as large ...

W. R. Cox

2000-01-01

110

Refractive index measurement with optical fiber Mach-Zehnder interferometer  

Microsoft Academic Search

An interferometric technique for determination of the refractive index of liquids is described. The method is based on measurements of phase variations caused by the relative movement of an optical fiber tip in a liquid sample. The apparatus consists of two independent interferometers. A two-frequency Michelson interferometer is used to measure the liquid sample displacement in the air, while an

Alojz Suhadolnik; Ales Babnik; Janez Mozina

1993-01-01

111

Giant Kerr nonlinearities using refractive-index enhancement  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

112

Complex Refractive Index of Media in the THz Spectral Range  

NASA Astrophysics Data System (ADS)

This chapter considers complex permittivity and refractive index of a medium, and basic laws for the terahertz (THz) plane wave interaction with media. We present simple effective medium models for the permittivity of two-phase media, and deal with the Kramers-Kronig relations and maximum entropy model that are used for the THz spectra testing and correction.

Peiponen, Kai-Erik; Gornov, Evgeny

113

Refractive index of Lithosil and Suprasil 312 at cryogenic temperature  

NASA Astrophysics Data System (ADS)

Measurements of the refractive index of two different Lithosil samples and a sample of Suprasil 312 at cryogenic temperature and at 293 K are reported for the spectral range from 480 nm to 894 nm. Such data are useful for the design of fused silica optical components and systems destined for space missions.

Vannoni, Maurizio; Olivieri, Monica; Mondello, Giuseppe; Sordini, Andrea; Molesini, Giuseppe

2010-06-01

114

Origin of dissipative losses in negative index of refraction materials  

Microsoft Academic Search

Negative index of refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized, and simulated several of these structures operating in the 10–16 GHz range. The origin

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

2003-01-01

115

Origin of dissipative losses in negative index of refraction materials  

Microsoft Academic Search

Negative index of refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized, and simulated several of these structures operating in the 10-16 GHz range. The origin

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

2003-01-01

116

Left handed metamaterials with negative index of refraction  

Microsoft Academic Search

Summary form only given. The author presents an introduction to the design and physical consequences of metamaterials with a frequency band with simultaneous negative permittivity and permeability. Negative index of refraction at microwave frequencies, and novel methods of construction are discussed.

S. Schultz

2002-01-01

117

Performance of a negative index of refraction lens  

Microsoft Academic Search

A plano-concave lens with negative index of refraction has been designed and fabricated. Such lenses have been postulated for many years, but only recently has their realization been made possible through improved simulation and fabrication procedures. We report here the simulation, fabrication, and performance of such a lens. The lens images the source field and reproduces the results of standard

C. G. Parazzoli; R. B. Greegor; J. A. Nielsen; M. A. Thompson; K. Li; A. M. Vetter; M. H. Tanielian; D. C. Vier

2004-01-01

118

Refractive index variation in nonaqueous sterically stabilized copolymer particles  

Microsoft Academic Search

We present procedures for preparing sterically stabilized polymer particles whose refractive index can be controlled over a range of a few percent. Particle sphericity and size distribution are such that suspensions crystallize at high concentrations. This at least ensures that Brownian motion dominates over particle settling and that the polydispersity is no more than about 10%. Of particular interest are

S. M. Underwood; W. Megen

1996-01-01

119

Index of Refraction Profile in a Highway Mirage  

NASA Astrophysics Data System (ADS)

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

Nelsen, Bryan; Lobue, James; Edwards, Mark

2003-11-01

120

On resolving the refractive index and the wave vector.  

PubMed

The identification of the refractive index and the wave vector for general (possibly active) linear, isotropic, homogeneous, and nonspatially dispersive media is discussed. Correct conditions for negative refraction necessarily include the global properties of the permittivity and permeability functions epsilon=epsilon(omega) and mu=mu(omega). On the other hand, a necessary and sufficient condition for left handedness can be identified at a single frequency (Re epsilon/|epsilon|+Re mu/|mu|<0). At oblique incidence to semi-infinite, active media, it is explained that the wave vector generally loses its usual interpretation for real frequencies. PMID:17072427

Skaar, Johannes

2006-11-15

121

Simulation and testing of a graded negative index of refraction lens  

Microsoft Academic Search

A gradient index (GRIN) lens using a negative index of refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable index of refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the index of refraction gradient required for a given focal length. An

R. B. Greegor; C. G. Parazzoli; J. A. Nielsen; M. A. Thompson; M. H. Tanielian; D. R. Smith

2005-01-01

122

Control of Refractive Index of Fluorinated Polyimide by Proton Beam Irradiation  

NASA Astrophysics Data System (ADS)

To clarify the feasibility of controlling the refractive index of a polymer by proton beam irradiation, we irradiated 1.0 MeV protons to a fluorinated polyimide film. Before and after the proton irradiation at a fluence between 1× 1014 and 7× 1016 cm-2, the film surface was scanned by a profilometer. It was found that the depth of a dent, which increases with fluence, was induced by the irradiation. The refractive index of the ion-irradiated region was calculated using the Lorentz--Lorenz equation, substituting the depth of the dent and the projected range of the protons. When the fluorinated polyimide was irradiated at a fluence of 7× 1016 cm-2, the refractive index increased by about 3.3%, which agrees with the increment in refractive index measured by spectroscopic ellipsometry. The increment in refractive index (0.21%) induced by the irradiation of protons at the fluence of 1× 1015 cm-2 is comparable to the value (0.35%) observed when protons were irradiated to SiO2 glass at a similar fluence. Therefore, it is reasonable to assume that the ion irradiation to a polymer can be a good method for fabricating a high-performance polymer-based optical waveguide.

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

2013-01-01

123

Refractive index tailoring in congruent Lithium Niobate by ion implantation  

NASA Astrophysics Data System (ADS)

Refractive index profiles of ion-implanted Lithium Niobate waveguides are investigated. Z+ and z- congruent Lithium Niobate samples have been implanted with C3+ ions at a fluence of 4 × 1014 ions/cm2. Dark m-lines measurements have been performed on ordinary (no) and extraordinary (ne) indexes for three different wavelengths (532 nm, 632.8 nm, 818 nm) before and after the annealing process. A reconstruction of refractive index profiles by Reflectivity Calculation Method (RCM) is presented and commented. The literature data for nuclear damage regime have been collected and critically examined. no and ne curves as function of the density of energy released in nuclear collisions, Ed, describing the effects of ion implantation on LN refractive indexes has been obtained on the basis of literature data. no depth profile, predicted according to no(Ed) curve, is in good agreement with the RCM reconstructed one. In the case of ne, a satisfactory agreement has been reached only slightly modifying the ne(Ed) curve and considering an alternative RCM profile structure.

Sugliani, S.; Bianconi, M.; Bentini, G. G.; Chiarini, M.; de Nicola, P.; Montanari, G. B.; Menin, A.; Malacarne, A.; Potì, L.

2010-10-01

124

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

125

Control of transient refractive index and laser beam propagation in a nanoplasma gas with a prepulse  

Microsoft Academic Search

Prepulse controlled laser beam propagation is demonstrated by utilizing transient refractive index in expanding-nanoplasma gases. The correlation between macroscopic refractive index and microscopic polarizability is verified, supporting the one-dimensional self-consistent hydrodynamic nanoplasma model

Hsu-hsin Chu; Yee-Fang Xiao; Hai-En Tsai; Chau-Hwang Lee; Jiunn-Yuan Lin; Jyhpyng Wang; Szu-yuan Chen

2004-01-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

127

Bacterial infection of macrophages induces decrease in refractive index.  

PubMed

Infection of cells by pathogens leads to both biochemical and structural modifications of the host cell. To study the structural modifications in a label-free manner, we use digital holographic microscopy, DHM, to obtain the integral refractive index distribution of cells. Primary murine bone marrow derived macrophages (BMDM) infected with Salmonella enterica serovar Typhimurium, undergo highly significant reduction in refractive index, RI, compared to uninfected cells. Infected BMDM cells from genetically modified mice lacking an inflammatory protein that causes cell death, caspase 1, also exhibit similar decrease in RI. These data suggest that any reduction in RI of Salmonella-infected BMDMs is pathogen induced and independent of caspase 1-induced inflammation or cell death. This finding suggests DHM may be useful for general real time monitoring of host cell interactions with infectious pathogens. PMID:22887897

Ekpenyong, Andrew E; Man, Si Ming; Achouri, Sarra; Bryant, Clare E; Guck, Jochen; Chalut, Kevin J

2012-08-06

128

Complex refractive index variation in proton-damaged diamond.  

PubMed

An accurate control of the optical properties of single crystal diamond during microfabrication processes such as ion implantation plays a crucial role in the engineering of integrated photonic devices. In this work we present a systematic study of the variation of both real and imaginary parts of the refractive index of single crystal diamond, when damaged with 2 and 3 MeV protons at low-medium fluences (range: 10(15) - 10(17) cm(-2)). After implanting in 125 × 125 ?m(2) areas with a scanning ion microbeam, the variation of optical pathlength of the implanted regions was measured with laser interferometric microscopy, while their optical transmission was studied using a spectrometric set-up with micrometric spatial resolution. On the basis of a model taking into account the strongly non-uniform damage profile in the bulk sample, the variation of the complex refractive index as a function of damage density was evaluated. PMID:23038581

Lagomarsino, S; Olivero, P; Calusi, S; Monticone, D Gatto; Giuntini, L; Massi, M; Sciortino, S; Sytchkova, A; Sordini, A; Vannoni, M

2012-08-13

129

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

130

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

131

Refractive index of light and the quark-gluon plasma  

NASA Astrophysics Data System (ADS)

The refractive index (RI) of light propagating in a medium of quark-gluon plasma (QGP) is studied. The weakly coupled QGP is studied in the framework of hard-thermal-loop (HTL) perturbation theory, and the strongly coupled one is treated based on the holographic approach. In more realistic setups, the feasibility of observing the optical phenomenon related to the RI of QGP is also discussed.

Liu, Juan; Luo, Min-Jie; Xu, Hao-Jie

2012-12-01

132

Modification of refractive index in silicon oxynitride films during deposition  

Microsoft Academic Search

Inhomogeneous thin films of SiOxNy have been deposited by laser ablation of a Si3N4 sintered target in an oxygen gas environment. The high oxidation rate of silicon nitride has been used to control the film stoichiometry by varying the oxygen partial pressure. The refractive index of the deposited material was able to be tailored at any value from 1.47 (SiO2)

R Machorro; E. C Samano; G Soto; F Villa; L Cota-Araiza

2000-01-01

133

Negative Refractive Index in Left-Handed Materials  

Microsoft Academic Search

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

David R. Smith; Norman Kroll

2000-01-01

134

Effect of ion implantation on the refractive index of glass  

Microsoft Academic Search

Studies on the changes of the index of refraction in glass due to ion implantation provide an insight into the structure of\\u000a amorphous substances, besides being important for the development of techniques for the production of optical integrated circuits.\\u000a Using a heavy ion accelerator, optically flat samples of Pyrex and Corning borosilicate glass were implanted with ions of\\u000a gallium and

P K Bhattacharya; N Sarma; A G Wagh

1976-01-01

135

Energy gap refractive index relations in semiconductors An overview  

NASA Astrophysics Data System (ADS)

An overview of the understanding of correlations between energy gap and refractive index of semiconductors is presented here. The atomic approach of Moss, the nearly free electron model of Penn, the oscillator concept of Wemple and the optical polarizability approach of Finkenrath are considered in this study. The Ravindra relation is discussed in the context of alternate approaches that have been presented in the literature. Case studies of applications of these relations to infrared materials and wide band gap semiconductors are presented.

Ravindra, N. M.; Ganapathy, Preethi; Choi, Jinsoo

2007-03-01

136

Wave effects in acoustic media with a negative refractive index  

Microsoft Academic Search

A method for analyzing media with a negative refractive index in acoustics has been proposed. An analog of the Lippmann-Schwinger\\u000a equation is derived from the initial hydrodynamical equation and a theory of wave scattering by inhomogeneities of a medium\\u000a with an arbitrarily specified value and sign of density and compressibility is constructed. Numerical simulation of the effects\\u000a related to negative

V. A. Burov; K. V. Dmitriev; S. N. Sergeev

2008-01-01

137

Simultaneous strain and refractive index sensor based on a TFBG  

NASA Astrophysics Data System (ADS)

°In this work, a dual sensor for simultaneous measurements of strain and refractive index (RI) is proposed. The sensor is based on a 4.5 tilted fibre Bragg grating (TFBG). Using two different demodulating techniques, namely monitoring the core mode wavelength and the normalized area of the transmission spectrum, it is possible to measure, strain and RI with a resolution of 2.5 ?? and 3 x 10-5, respectively.

Alberto, Nélia J.; Marques, Carlos A.; Pinto, João L.; Nogueira, Rogério N.

2010-09-01

138

On The Refractive Index of Soot at Flame Temperature  

Microsoft Academic Search

Data of the optical constants of soot at flame temperature are presented for the visible and infrared regions (0.4-5 ?m). Both real and imaginary parts of the refractive index are determined from in-situ extinction coefficient spectra by fitting to theoretical spectra calculated by using the Mie theory in conjunction with a dispersion model. Particle size used in Mie calculation is

Z. G. HABIB; P. Vervisch

1988-01-01

139

Intense Ion Beam Diode Studies with Refractive Index Gradient Diagnostics  

Microsoft Academic Search

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

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

1996-01-01

140

High refractive index at electron cyclotron harmonics in a plasma  

Microsoft Academic Search

A theoretical explanation for the enhanced emissions of electron cyclotron harmonics from a non-relativistic plasma immersed in an external magnetic field, is considered. An asymptotic resolution of the general dispersion equation for the cyclotron harmonics and for quasi-perpendicular propagation is systematically studied. We obtain a quasi-longitudinal and a quasi-extraordinary mode, the refractive index of both modes being very large. The

Y. Furutani; G. Kalman

1965-01-01

141

Carrier-induced refractive-index change in quantum-well lasers  

SciTech Connect

We investigated the loaded gain and the carrier-induced refractive-index change in quantum-well lasers. A quantum-well laser is found typically to have a higher gain and a smaller refractive-index change than a conventional diode laser. We also found that the gain and the refractive-index change for these two types of semiconductor lasers saturate similarly, with the refractive index being a much weaker function of laser intensity.

Chow, W.W.; Depatie, D.

1988-04-01

142

Carrier-induced refractive-index-change in quantum-well lasers.  

PubMed

We investigated the loaded gain and the carrier-induced refractive-index change in quantum-well lasers. A quantum-well laser is found typically to have a higher gain and a smaller refractive-index change than a conventional diode laser. We also found that the gain and the refractive-index change for these two types of semiconductor lasers saturate similarly, with the refractive index being a much weaker function of laser intensity. PMID:19745880

Chow, W W; Depatie, D

1988-04-01

143

Photoinduced absorption and refractive-index induction in phosphosilicate fibres by radiation at 193 nm  

SciTech Connect

The photoinduced room-temperature-stable increase in the refractive index by {approx}5x10{sup -4} at a wavelength of 1.55 {mu}m was observed in phosphosilicate fibres without their preliminary loading with molecular hydrogen. It is shown that irradiation of preliminary hydrogen-loaded fibres by an ArF laser at 193 nm enhances the efficiency of refractive-index induction by an order of magnitude. The induced-absorption spectra of preforms with a phosphosilicate glass core and optical fibres fabricated from them are studied in a broad spectral range from 150 to 5000 nm. The intense induced-absorption band ({approx}800 cm{sup -1}) at 180 nm is found, which strongly affects the formation of the induced refractive index. The quantum-chemical model of a defect related to this band is proposed. (optical fibres)

Rybaltovsky, A A; Sokolov, V O; Plotnichenko, V G; Lanin, Aleksei V; Semenov, S L; Dianov, Evgenii M [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation); Gur'yanov, A N; Khopin, V F [Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

2007-04-30

144

Kramers-Kronig relations and sum rules of negative refractive index media  

Microsoft Academic Search

Negative refractive index media have become a hot topic in physics due to their proposed revolutionary properties, which would have drastic consequences in design of novel optical devices. We show that Kramers-Kronig relations connecting the real and imaginary parts of the complex refractive index of absorbing media are valid even though the real refractive index may take negative value at

K.-E. Peiponen; V. Lucarini; E. M. Vartiainen; J. J. Saarinen

2004-01-01

145

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.

146

Negative Refractive Index in Left-Handed Materials  

SciTech Connect

The real part of the refractive index n({omega}) of a nearly transparent and passive medium is usually taken to have only positive values. Through an analysis of a current source radiating into a 1D ''left-handed'' material (LHM) -- where the permittivity and permeability are simultaneously less than zero -- we determine the analytic structure of n({omega}) , demonstrating frequency regions where the sign of Re[n({omega})] must, in fact, be negative. The regime of negative index, made relevant by a recent demonstration of an effective LHM, leads to unusual electromagnetic wave propagation and merits further exploration.

Smith, David R.; Kroll, Norman

2000-10-02

147

Refractive index of glass and its dipersion for visible light.  

SciTech Connect

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

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

2010-01-01

148

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

149

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

NASA Astrophysics Data System (ADS)

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 40mm is up to 58.8nm/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 0.03nm° C. Such a kind of high-sensitivity, easy-to-fabricate and simple-structure interferometer may find applications in the chemical or biochemical sensing fields.

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

2011-08-01

150

Highly sensitive refractive index sensor based on two cascaded long period gratings with rotary refractive index modulation  

NASA Astrophysics Data System (ADS)

We present a refractive index (RI) sensor based on a fiber Mach-Zehnder interferometer, which is realized by two cascaded special long period gratings with rotary refractive index modulation (C-RLPFG). The wavelength shift of the refractometer behaves good linear response in a RI range of 1.3342 to 1.3362, and the sensitivity of 14.5pm/mm for 0.01SRI change has been obtained. The sensitivity is 4 times higher than that of M-Z interferometer formed by using normal long period fiber gratings. Such kind of high sensitivity, easy fabrication and simple structure interferometer may find applications in chemical or biochemical sensing field.

Zhu, Tao; Fan, Yanen; Deng, Ming; Rao, Yunjiang

2011-05-01

151

Negative refractive index materials for improved solar cells  

NASA Astrophysics Data System (ADS)

Planar thin-film solar cells can exploit Fabry-Perot resonances in the spectral domain of weak absorption to make them more efficient. However, their spectral width decreases and their number increases for a thicker solar cell, both being detrimental. Here, we show that an optically complementary material, i.e., a material with a negative but otherwise identical refractive index to that of the solar cell material and with the same impedance, allows a single, spectrally immensely broad, Fabry-Perot resonance to be obtained. This is useful to enhance the absorption across the entire spectral domain of interest. If a material with the required optical response were available, a solar cell could be implemented that performs close to the Lambertian limit. However, since the idealistic material properties assumed herein cannot be achieved, an actual implementation may exploit nanostructures such as, e.g., dispersion engineered photonic crystals. In a reasonable spectral range their optical response can be close to that required.

Fahr, Stephan; Rockstuhl, Carsten; Lederer, Falk

2013-09-01

152

Refractive index matching improves optical object detection in paper  

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

153

Thermal conductivity and refractive index of hafnia-alumina nanolaminates  

NASA Astrophysics Data System (ADS)

Hafnia-alumina nanolaminates show improved smoothness and reduced crystallinity relative to pure hafnia in films formed by atomic layer deposition (ALD). However, typical nanolaminates also show reduced cross-plane thermal conductivity due to the much larger interface density relative to continuous films. We find that the interface thermal resistance in hafnia-alumina nanolaminates is very low and does not dominate the film thermal conductivity, which is 1.0 to 1.2 W/(m K) at room temperature in 100 nm thin films regardless of the interface density. Measured films had a number of interfaces ranging from 2 to 40, equivalent to interface spacing varying from about 40 to 2 nm. The degree of crystallinity of these films appears to have a much larger effect on thermal conductivity than that of interface density. Cryogenic measurements show good agreement with both the minimum thermal conductivity model for disordered solids and the diffuse mismatch model of interface resistance down to about 80 K before diverging. We find that the films are quite smooth through a 400:5 ratio of hafnia to alumina in terms of ALD cycles, and the refractive index scales as expected with increasing alumina concentration.

Gabriel, Nicholas T.; Talghader, Joseph J.

2011-08-01

154

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

155

Enhanced index of refraction in four-wave-mixing media  

NASA Astrophysics Data System (ADS)

Refractive index enhancement accompanied by vanishing absorption in a four-level atomic system interacting with two control and two probe fields in a regime of four-wave mixing (FWM) has been predicted and studied in the present work. We analyzed the maximal index enhancement in the four-level FWM system and gave index estimates for a real atomic gas of 40K, taking into account its multilevel structure and collisional and Doppler broadenings at large atomic densities. We also discussed how vanishing absorption with no nearby amplification can be realized in a two species system, consisting of a four-level FWM and a two-level system, where the latter provides additional absorption for one of the probe fields. We numerically estimated the index change in a system composed of 40K and 39K gases.

Kuznetsova, Elena; Rajapakse, Renuka; Yelin, S. F.

2013-09-01

156

Determination of refractive index and absorption coefficient of iron- oxide-bearing slags  

NASA Astrophysics Data System (ADS)

The refractive index and absorption coefficient of amorphous Fe2O3-SiO2-CaO-Al2O3 slags have been determined at room temperature as functions of the basicity of [mass pct CaO]/[mass pct SiO2] and the Fe2O3 concentration. The refractive index has been measured by an ellipsometer at 546 nm, and the absorption coefficient has been determined from transmittance measured by a spectrophotometer in the wavelength range of 350 to 1000 nm. The refractive index increases with increasing basicity of [CaO]/[SiO2] and the Fe2O3 concentration. On the other hand, with decreasing basicity of [CaO]/[SiO2], the absorption coefficient is increased in the near-infrared region, and the absorption edge by the charge transfer band is shifted to a shorter wavelength. With increasing Fe2O3 concentration, the absorption coefficient is increased in the measured wavelength range, and the absorption edge by the charge transfer band is shifted to a longer wavelength. These dependences of refractive index and absorption coefficient on the basicity and the Fe2O3 concentration are discussed.

Susa, Masahiro; Li, Futao; Nagata, Kazuhiro

1992-06-01

157

Applicability of ferrimagnetic hosts to nanostructured negative index of refraction (left-handed) materials  

Microsoft Academic Search

There has been considerable interest generated by the demonstration of (epsilon) < 0, (mu) < 0 composite materials. These negative index of refraction materials, a subset of the class of materials labeled 'left-handed', possess two different arrays of resonant structures which separately give rise to negative (epsilon) and (mu) over the appropriate microwave frequency interval. Any attempt to significantly increase

Graeme Dewar

2002-01-01

158

Extraction of complex refractive index dispersion from SPR data  

NASA Astrophysics Data System (ADS)

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

Nakkach, Mohamed; Moreau, Julien; Canva, Michael

2010-02-01

159

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

160

Tissue Refractive Index Fluctuations Report on Cancer Development  

NASA Astrophysics Data System (ADS)

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

Popescu, Gabriel

2012-02-01

161

Nonlinear refractive index of RECOB (RE = Gd and La) crystals  

NASA Astrophysics Data System (ADS)

The Z-scan technique is employed to obtain the nonlinear refractive index ( n 2) of the Ca4REO(BO3)3 (RECOB, where RE = Gd and La) single crystals using 30 fs laser pulses centered at 780 nm for the two orthogonal orientations determined by the optical axes ( X and Z) relative to the direction of propagation of the laser beam ( k// Y// crystallographic b-axis). The large values of n 2 indicate that both GdCOB and LaCOB are potential hosts for Yb:RECOB lasers operating in the Kerr-lens mode locking (KLM) regime.

Barros, G.; Guedes, I.; Misoguti, L.; Zilio, S. C.; Loong, C.-K.; Wang, J.; Hu, X.; Zhang, H.

2009-02-01

162

Room-temperature formation of low refractive index silicon oxide films using atmospheric-pressure plasma.  

PubMed

This study aims to apply atmospheric-pressure (AP) plasma to the fabrication of single-layer anti-reflection (AR) coatings with porous silicon oxide. 150 MHz very high-frequency (VHF) excitation of AP plasma permits to enhance the chemical reactions both in the gas phase and on the film-growing surface, increasing deposition rate significantly. Silicon oxide films were prepared from silane (SiH4) and carbon dioxide (CO2) dual sources diluted with helium. The microstructure and refractive index of the films were studied using infrared absorption and ellipsometry as a function of VHF power density. It was shown that significant increase in deposition rate at room temperature prevented the formation of a dense SiO2 network, decreasing refractive index of the resulting film effectively. As a result, a porous silicon oxide film, which had the lowest refractive index of 1.24 at 632.8 nm, was obtained with a very high deposition rate of 235 nm/s. The reflectance and transmittance spectra showed that the low refractive index film functioned as a quarter-wave AR coating of a glass plate. PMID:21776642

Nakamura, Kei; Yamaguchi, Yoshihito; Yokoyama, Keiji; Higashida, Kosuke; Ohmi, Hiromasa; Kakiuchi, Hiroaki; Yasutake, Kiyoshi

2011-04-01

163

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

164

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

National Technical Information Service (NTIS)

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 ra...

B. J. Frey D. B. Leviton

2006-01-01

165

Optimization of Cladding-Structure-Modified Long-Period-Grating Refractive-Index Sensors  

Microsoft Academic Search

The cladding-modified long-period-grating (LPG) refractive-index sensors with a high-refractive-index overlay are optimized based on systematical studies on the structure-modified LPG. Dependence of the cladding-mode effective indexes on the parameters of the structure-modified LPG, such as the overlay refractive index (RI), the overlay thickness, the cladding-layer radius, and the ambient RI, as well as the order of cladding mode, are investigated

Jian Yang; Li Yang; Chang-Qing Xu; Yingfu Li

2007-01-01

166

Experimental verification of a negative index of refraction.  

PubMed

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 beam through a prism fabricated from this material, we determine the effective n, appropriate to Snell's law. These experiments directly confirm the predictions of Maxwell's equations that n is given by the negative square root of epsilon.mu for the frequencies where both the permittivity (epsilon) and the permeability (mu) are negative. Configurations of geometrical optical designs are now possible that could not be realized by positive index materials. PMID:11292865

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

2001-04-01

167

Dark matter constraints from a cosmic index of refraction  

SciTech Connect

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

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

2010-09-15

168

Ultrasensitive optical rotation and refractive-index measurements  

SciTech Connect

Among the many techniques that benefited from the development of laser technology, two examples are the improved detectability in optical rotation and in refractive index measurements. In conjunction with liquid chromotography, one can take advantage of the improved detectability to study molecules that are present in small quantities in fairly complex samples, such as biological fluids and fossil fuels. The high degree of collimation of the laser allows better levels of extinction to be achieved between crossed polarizers. The amount of scattered light, and thus the amount of depolarization, can be greatly reduced. This then allows small rotations of the polarization axis of light to be detected. A detectability of 1.5 x 10/sup -5/ degrees can be achieved. The high monochromaticity of the laser brings about new applications of Fabry-Perot interferometry. The interference fringes can be used to monitor refractive index changes inside the interferometer. In conjunction with a flow cell interfaced to a liquid chromatograph, a detectability of 4 x 10/sup -9/ RI units is possible.

Yeung, E.S.

1983-01-01

169

Dark Matter Constraints from a Cosmic Index of Refraction  

SciTech Connect

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

Gardner, Susan; Latimer, David C.

2009-04-01

170

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

171

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

172

Measurement of complex refractive index of human blood by low-coherence interferometry  

NASA Astrophysics Data System (ADS)

In this article, the usefulness of the optical technique for measurements of blood complex refractive index has been examined. Measurement of optical properties of human blood is difficult to perform because of its nonuniform nature. However, results of my investigation have shown the usefulness of low-coherence interferometry for measurement complex refractive index of human blood. Furthermore, mathematical analysis of spectrum of measured signal have made possible to determined relationship between complex refractive index and hematocrit level in human blood.

Jedrzejewska-Szczerska, M.

2013-10-01

173

Multimode fiber Mach-Zehnder interferometer for measurement of refractive index  

Microsoft Academic Search

A novel class of multimode optical fiber Mach-Zehnder interferometer suited for refractive index measurement is presented. The Mach-Zehnder interferometer was constructed by making two coupling points in a multimode optical fiber at localized regions with an electric arc system. The Mach-Zehnder interferometer as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results

Chien-Hsing Chen; Yi-Chun Chen; Jian-Neng Wang; Lai-Kwan Chau; Jaw-Luen Tang; Wei-Te Wu

2010-01-01

174

Tapered fiber Mach-Zehnder interferometer for simultaneous measurement of refractive index and temperature  

Microsoft Academic Search

An approach to achieve simultaneous measurement of refractive index and temperature is proposed by using a Mach-Zehnder interferometer realized on tapered single-mode optical fiber. The attenuation peak wavelength of the interference with specific order in the transmission spectrum shifts with changes in the environmental refractive index and temperature. By utilizing S-band and C\\/L-band light sources, simultaneous discrimination of refractive index

Ping Lu; Liqiu Men; Kevin Sooley; Qiying Chen

2009-01-01

175

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

Microsoft Academic Search

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

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

2003-01-01

176

Model of refractive-index changes in lithium niobate waveguides fabricated by ion implantation  

Microsoft Academic Search

A model is presented to explain the refractive-index changes in the ion-implanted LiNbOâ waveguides that indicates that the lattice damage may be the main factor for the refractive-index changes. The model indicates that a slight enhancement may occur for the extraordinary refractive index in the ion-implanted LiNbOâ waveguides with lattice damage ratios of less than 65%, and a maximum positive

Jiang Yi; Wang Keming; Wang Xuelin; Chen Feng; Jia Chuanlei; Wang Lei; Jiao Yang; Lu Fei

2007-01-01

177

Model of refractive-index changes in lithium niobate waveguides fabricated by ion implantation  

Microsoft Academic Search

A model is presented to explain the refractive-index changes in the ion-implanted LiNbO3 waveguides that indicates that the lattice damage may be the main factor for the refractive-index changes. The model indicates that a slight enhancement may occur for the extraordinary refractive index in the ion-implanted LiNbO3 waveguides with lattice damage ratios of less than 65%, and a maximum positive

Yi Jiang; Ke-Ming Wang; Xue-Lin Wang; Feng Chen; Chuan-Lei Jia; Lei Wang; Yang Jiao; Fei Lu

2007-01-01

178

On the performance quantification of resonant refractive index sensors.  

PubMed

Refractive index (RI) sensors based on optical resonance techniques are receiving a high degree of attention because of the need to develop simple, low-cost, high-throughput detection technologies for a number of applications. While the sensing mechanism of most of the reported RI sensors is similar, the construction is quite different from technique to technique. It is desirable to have a uniform mechanism for comparing the various RI sensing techniques, but to date there exists a degree of variation as to how the sensing performance is quantified. Here we set forth a rigorous definition for the detection limit of resonant RI sensors that accounts for all parameters that affect the detection performance. Our work will enable a standard approach for quantifying and comparing the performance of optical resonance-based RI sensors. Additionally, it will lead to design strategies for performance improvement of RI sensors. PMID:18542175

White, Ian M; Fan, Xudong

2008-01-21

179

Spatially varying index of refraction: An open ended undergraduate topic  

SciTech Connect

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

Krueger, D.A.

1980-03-01

180

Full field imaging based instantaneous hyperspectral absolute refractive index measurement  

SciTech Connect

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

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

2012-01-01

181

Group refractive index reconstruction with broadband interferometric confocal microscopy  

PubMed Central

We propose a novel method of measuring the group refractive index of biological tissues at the micrometer scale. The technique utilizes a broadband confocal microscope embedded into a Mach–Zehnder interferometer, with which spectral interferograms are measured as the sample is translated through the focus of the beam. The method does not require phase unwrapping and is insensitive to vibrations in the sample and reference arms. High measurement stability is achieved because a single spectral interferogram contains all the information necessary to compute the optical path delay of the beam transmitted through the sample. Included are a physical framework defining the forward problem, linear solutions to the inverse problem, and simulated images of biologically relevant phantoms.

Marks, Daniel L.; Schlachter, Simon C.; Zysk, Adam M.; Boppart, Stephen A.

2010-01-01

182

Long period grating refractive-index sensor: optimal design for single wavelength interrogation  

SciTech Connect

We report the design criteria for the use of long period gratings (LPGs) as refractive-index sensors with output power at a single interrogating wavelength as the measurement parameter. The design gives maximum sensitivity in a given refractive-index range when the interrogating wavelength is fixed. Use of the design criteria is illustrated by the design of refractive-index sensors for specific application to refractive-index variation of a sugar solution with a concentration and detection of mole fraction of xylene in heptane (paraffin).

Kapoor, Amita; Sharma, Enakshi K.

2009-11-01

183

Experimental verification and simulation of negative index of refraction using Snell's law.  

PubMed

We report the results of a Snell's law experiment on a negative index of refraction material in free space from 12.6 to 13.2 GHz. Numerical simulations using Maxwell's equations solvers show good agreement with the experimental results, confirming the existence of negative index of refraction materials. The index of refraction is a function of frequency. At 12.6 GHz we measure and compute the real part of the index of refraction to be -1.05. The measurements and simulations of the electromagnetic field profiles were performed at distances of 14lambda and 28lambda from the sample; the fields were also computed at 100lambda. PMID:12689029

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

2003-03-11

184

Characterization of Long-period Grating Refractive Index Sensors and Their Applications  

PubMed Central

The influence of grating length and bend radius of long-period gratings (LPGs) on refractive index sensing was examined. Sensitivity to refractive indexes smaller than that of silica could be enhanced by bending LPGs. Bent LPGs lost sensitivity to refractive indexes higher than that of silica, whereas a 20-mm-long LPG arranged in a straight line had considerable sensitivity. These experimental results demonstrated that the sensitivity characteristics of LPGs to refractive index could be controlled by grating length and bend radius.

Tsuda, Hiroshi; Urabe, Kei

2009-01-01

185

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

186

Lattice Parameter Dependence of Refractive Index and Dielectric Constant of Czochralski Grown Rare-Earth Garnet Single Crystals in Solid Solution  

NASA Astrophysics Data System (ADS)

The refractive index and dielectric constant of garnet single crystals grown by the Czochralski method were measured. New results were obtained which revealed that both the refractive index and dielectric constant increased with the increase of their lattice parameters depending on their ionic radius of rare-earth ions.

Kimura, Hideo; Miyazaki, Akimitsu

2002-08-01

187

Wave Refraction in Negative-Index Media: Always Positive and Very Inhomogeneous  

Microsoft Academic Search

We present the first treatment of the refraction of physical electromagnetic waves in newly developed negative index media (NIM), also known as left-handed media (LHM). The NIM dispersion relation implies that group fronts refract positively even when phase fronts refract negatively. This difference results in rapidly dispersing, very inhomogeneous waves. In fact, causality and finite signal speed always prevent negative

P. M. Valanju; R. M. Walser; A. P. Valanju

2002-01-01

188

[Study on measurement of liquid refractive index by analyzing SPR spectrum character].  

PubMed

The principle of optic fiber surface plasmon resonance sensor is discussed in detail based on the electromagnetic theory and radial theory in the present paper. The relationship between SPR spectrum resonance wavelength and liquid refractive index is also analyzed. Through relative spectrum measurement technology, SPR spectrum curves, whose resonance wavelength increases with increasing liquid refractive index, were obtained for eight different kinds of chemical liquids. The measurement of concentration of mixed solution including ethanol and glycol was performed by analyzing the spectrum attribute. The experimental results show that the sensing system features simple structure and all light transmitted by fiber. It not only realizes rapid, accurate and real time measurement for target medium, but also can be used in some special situations and easily realize long distance measurement. PMID:16836149

Zeng, Jie; Liang, Da-kai; Zeng, Zhen-wu; Du, Yan

2006-04-01

189

Design of two-dimensional photonic crystal nanocavities with low-refractive-index material cladding  

NASA Astrophysics Data System (ADS)

We have theoretically investigated two-dimensional photonic crystal (2D PC) nanocavities with low-refractive-index (low- n) material cladding using a 3D finite-difference time-domain method. When the refractive index of the cladding is increased from 1 to 1.535, corresponding to that of organic polymers, the Q factor markedly decreases (Q<103). We finely adjusted the positions of the holes at both edges of the 2D PC nanocavities. The Q factor can be increased by a factor of up to 21 (Q>104) by shifting the neighboring four pairs of holes inward by suitable amounts. In addition, we examined the real and wavevector space distributions of the resonant modes. We revealed significant design rules based on single and double Gaussian envelope functions, which can be used to effectively and flexibly develop and finely adjust the optical properties of 2D PC nanocavities with low- n material cladding.

Okano, M.; Yamada, T.; Sugisaka, J.; Yamamoto, N.; Itoh, M.; Sugaya, T.; Komori, K.; Mori, M.

2010-01-01

190

Cyclotriphosphazenes with sulfur-containing side groups: refractive index and optical dispersion.  

PubMed

Two types of cyclotriphosphazenes with sulfur-containing side groups were synthesized for an examination of their optical properties including refractive index, optical dispersion, and absorption in the UV-vis region. In the first type, the residue from ethanethiol was introduced through P-S bonding. In the second type, the residues from alcohols that contain alkyl sulfide units were introduced through P-O bonding. A high content of sulfur and phosphorus atoms and thus a high refractive index of 1.6161 were achieved in the first case: however, the optical dispersion increased due to the absorption by the P-S bonds. This increase in optical dispersion was avoided in the second case, where the phosphazene skeleton showed no absorption down to 230 nm. The molar refraction and the molar volume of the -P=N- repeating unit were evaluated, and these demonstrated the advantage of the cyclotriphosphazene skeleton as a building block for optical materials with high refractive indices. In addition, the transparency of the phosphazene skeleton is beneficial for low optical dispersion. PMID:19319392

Fushimi, Toshiki; Allcock, Harry R

2009-02-16

191

Broadband Negative-Refractive-Index Media: Analytical Modeling and Free Space Measurements  

Microsoft Academic Search

Since the realization of negative-refractive-index (NRI) media, the narrow bandwidth of these materials has continually hindered their practical use. The bandwidth of traditional NRI media is limited by the narrowband response of the split-ring resonator (SRR) that gives rise to negative effective permeability. Typical SRRs exhibit negative permeability over a fractional bandwidth of approximately 10%. Increasing the bandwidth over which

Scott M. Rudolph; Carl Pfeiffer; Anthony Grbic

192

Fabrication of refractive index distributions in polymer using a photochemical reaction  

NASA Astrophysics Data System (ADS)

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

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

2000-01-01

193

Fermat's principle and the formal equivalence of local light-ray rotation and refraction at the interface between homogeneous media with a complex refractive index ratio.  

PubMed

We derive a formal description of local light-ray rotation in terms of complex refractive indices. We show that Fermat's principle holds, and we derive an extended Snell's law. The change in the angle of a light ray with respect to the normal of a refractive index interface is described by the modulus of the refractive index ratio; the rotation around the interface normal is described by the argument of the refractive index ratio. PMID:19183663

Sundar, Bhuvanesh; Hamilton, Alasdair C; Courtial, Johannes

2009-02-01

194

Controlling the mode volume in high-Q microcavities with high refractive index coatings  

NASA Astrophysics Data System (ADS)

Developing optical resonators with high quality factors, small mode volumes, and high refractive index contrast is important for many integrated optics and communications applications. High quality factors and small mode volumes are especially desirable to maximize the circulating intensity and Purcell factor for laser applications. However, controlling an optical resonator's mode volume and refractive index contrast can be difficult as they depend primarily on the inherent material properties of the resonator. One approach to reduce mode volume and control refractive index contrast is to apply high refractive index polymer coatings. However, polymer coatings are not compatible with all fabrication processes and not as robust as silica and silicon. Recently, we developed and characterized high refractive index silica films containing small amounts of titanium dopant. The silica films are fabricated using a sol gel method with methyl triethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) precursors. Depending on the amount of titanium added, the refractive index of the resulting film can be tuned from 1.44 to 1.62, as measured by spectroscopic ellipsometry. By spin coating these high index silica films onto silica toroid resonators, we experimentally and numerically obtain a significant reduction in mode volume while maintaining high quality factors. Additionally, the presence of the high refractive index coating allows tuning of the circulating light's position, shape, and interaction with the coating. Therefore, these high refractive index films offer a useful and more robust method to optimize the properties of optical devices for communications and integrated optics applications.

Maker, Ashley J.; Rose, Brian A.; Armani, Andrea M.

2013-03-01

195

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

196

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

197

A negative refractive index metamaterial wave plate for millimetre-wave applications  

NASA Astrophysics Data System (ADS)

By use of a metamaterial based on the ‘cut wire pair’ geometry, highly birefringent wave plates may be constructed by virtue of the geometry’s ability of having a negative and positive refractive index along its perpendicular axes. Past implementations have been narrow band in nature due to the reliance on producing a resonance to achieve a negative refractive index band and the steep gradient in the phase difference that results. In this paper we attempt to design and manufacture a W-band quarter wave plate embedded in polypropylene that applies the Pancharatnam method to increase the useable bandwidth. Our modelling demonstrates that a broadening of the phase difference’s bandwidth defined as the region 90° +/- 2° is possible from 0.6% (101.7 GHz - 102.3 GHz) to 7.8% (86.2 GHz - 93.1 GHz). Our experimental results show some agreement with our modelling but differ at higher frequencies.

Mohamed, I.; Pisano, G.; Ng, M. W.; Maffei, B.; Haynes, V.; Ozturk, F.

2012-09-01

198

Numerical simulations of negative-index refraction in wedge-shaped metamaterials.  

PubMed

A wedge-shaped structure made of split-ring resonators (SRR) and wires is numerically simulated to evaluate its refraction behavior. Four frequency bands, namely, the stop band, left-handed band, ultralow-index band, and positive-index band, are distinguished according to the refracted field distributions. Negative phase velocity inside the wedge is demonstrated in the left-handed band and the Snell's Law is conformed in terms of its refraction behaviors in different frequency bands. Our results confirmed that negative index of refraction indeed exists in such a composite metamaterial and also provided a convincing support to the results of previous Snell's Law experiments. PMID:16090107

Dong, Z G; Zhu, S N; Liu, H; Zhu, J; Cao, W

2005-07-12

199

Determination of the refractive index of a-Si(1-x)C(x):H thin films from infrared absorption spectra.  

PubMed

The index of refraction of a-Si(1-x)C(x):H thin films obtained by dc magnetron sputtering was determined by means of IR absorption measurements. Structural and compositional changes that take place by increasing x make the film a mixture of different species, giving an effective value of the refractive index. PMID:20820249

Lugomer, S; Maksimovi?, A; Gracin, D

1993-03-01

200

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

Microsoft Academic Search

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

Hanli Liu; Bertrand Beauvoit; Mika Kimura; Britton Chance

1996-01-01

201

Refractive index of a transparent liquid measured with a concave mirror  

NASA Astrophysics Data System (ADS)

This paper describes the spherical concave mirror method for measuring the index of refraction of transparent liquids based on locating the actual and apparent radii of curvature of the mirror. We derived the refractive index equation using Snell’s law and the small-angle approximation.

Joshi, Amitabh; Serna, Juan D.

2012-09-01

202

Development of Chiral Negative Refractive Index Metamaterials for the Terahertz Frequency Regime  

Microsoft Academic Search

A novel negative refractive index (NRI) chiral meta-material (MTM), based on the Y structure, has been designed and tested in the microwave and terahertz frequencies. In addition to providing magnetoelectric coupling, this MTM has a negative index of refraction passband that can be tuned in both the frequency of operation and bandwidth with lower losses compared to other known chiral

Nantakan Wongkasem; Alkim Akyurtlu; Kenneth A. Marx; Qi Dong; Jin Li; William D. Goodhue

2007-01-01

203

Photonic approach to making a material with a negative index of refraction  

Microsoft Academic Search

An approach to producing a composite material with negative refraction index is demonstrated. It is shown that a photonic structure consisting of two dielectric materials, with positive and negative dielectric permittivities, can support electromagnetic surface waves which exhibit the unusual electromagnetic property of left handedness (or negative refraction index). Depending on the dielectric materials, these surface waves localized at the

Gennady Shvets

2003-01-01

204

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

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

205

Femtosecond filament induced birefringence in argon and in air: Ultrafast refractive index change  

Microsoft Academic Search

The birefringence of a linearly polarized femtosecond laser filament in gases has been previously established. In this work, we report the time-dependent refractive index measurements of the filament based upon the spectral modulation of a weak probe pulse in air and in argon gas at 1 atmospheric pressure. The polarization dependence of the refractive index modulation induced by the delayed

Claude Marceau; S. Ramakrishna; Simon Génier; Tie-Jun Wang; Yanping Chen; Francis Théberge; Marc Châteauneuf; Jacques Dubois; Tamar Seideman; See Leang Chin

2010-01-01

206

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

207

A new approach to estimate refractive index, electronic polarizability, and optical basicity of binary oxide glasses  

NASA Astrophysics Data System (ADS)

In this paper, we introduce the optical electronegativity ??glass* to predict basic properties of binary oxide glasses. Optical electronegativity ??glass* of numerous binary oxide glasses has been evaluated on the basis of two different properties: the linear refractive index n and energy gap Eg, which have demonstrated remarkable correlation. Furthermore, we also calculate the refractive index n through the energy-gap-based optical electronegativity ??E*, and obtain a perfect linear correlation between the calculated refractive index ncal and the n0 values of Dimitrov and Komatsu. The average electronic oxide polarizability ? and the optical basicity ? of binary oxide glasses have been estimated on the basis of the optical electronegativity ??glass* calculated from the refractive index n. The estimated values are in good agreement with the available experimental data. The present method needs only one original experimental parameter to estimate the optical electronegativity ??glass*, which is the refractive index n.

Zhao, Xinyu; Wang, Xiaoli; Lin, Hai; Wang, Zhiqiang

2008-07-01

208

Model of refractive-index changes in lithium niobate waveguides fabricated by ion implantation  

SciTech Connect

A model is presented to explain the refractive-index changes in the ion-implanted LiNbO{sub 3} waveguides that indicates that the lattice damage may be the main factor for the refractive-index changes. The model indicates that a slight enhancement may occur for the extraordinary refractive index in the ion-implanted LiNbO{sub 3} waveguides with lattice damage ratios of less than 65%, and a maximum positive change ({delta}n=0.0338) occurs at a damage ratio of 33%. The model explains both the positive refractive-index changes observed in waveguides formed using 500 keV Si{sup +}-ion implantation and the refractive-index changes observed in He{sup +}-ion-implanted waveguides.

Jiang Yi; Wang Keming; Wang Xuelin; Chen Feng; Jia Chuanlei; Wang Lei; Jiao Yang; Lu Fei [School of Physics and Microelectronics, Shandong University, Jinan 250100, Shandong (China); School of Information Science and Engineering, Shandong University, Jinan 250100, Shandong (China)

2007-05-15

209

Method for the preparation of porous silica antireflection coatings varying in refractive index from 1. 22 to 1. 44  

SciTech Connect

Coatings of refractive index that vary between 1.22 and 1.44 were prepared from combinations of a colloidal silica suspension and a polysiloxane solution. The polysiloxane acted both as a binder and a filler for the colloidal silica particles. Increasing ratios gave coatings of lower porosity, hence higher refractive index, and better abrasion resistance. This variation in refractive index allowed high-efficiency quarter-wave antireflection coatings to be prepared on substrates whose index varied from 1.45 to 2.1. The laser damage thresholds of all the coatings were {lt}50 J/cm{sup 2} at a wavelength of 1.06 {mu}m with a 10-ns pulse length.

Thomas, I.M. (Lawrence Livermore National Laboratory, University of California, P.O. Box 5508, L-483, Livermore, California 94550 (United States))

1992-10-01

210

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

NASA Astrophysics Data System (ADS)

The refractive index of holographic emulsions is an important parameter needed for designing holographic optical elements (HOEs). In this paper 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 HOEs 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, Tae-Jin; Campbell, Eugene W.; Kostuk, Raymond K.

1993-09-01

211

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

NASA Astrophysics Data System (ADS)

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.

1993-03-01

212

Geometry-invariant gradient refractive index lens: analytical ray tracing.  

PubMed

A new class of gradient refractive index (GRIN) lens is introduced and analyzed. The interior iso-indicial contours mimic the external shape of the lens, which leads to an invariant geometry of the GRIN structure. The lens model employs a conventional surface representation using a coincoid of revolution with a higher-order aspheric term. This model has a unique feature, namely, it allows analytical paraxial ray tracing. The height and the angle of an arbitrary incident ray can be found inside the lens in a closed-form expression, which is used to calculate the main optical characteristics of the lens, including the optical power and third-order monochromatic aberration coefficients. Moreover, due to strong coupling of the external surface shape to the GRIN structure, the proposed GRIN lens is well suited for studying accommodation mechanism in the eye. To show the power of the model, several examples are given emphasizing the usefulness of the analytical solution. The presented geometry-invariant GRIN lens can be used for modeling and reconstructing the crystalline lens of the human eye and other types of eyes featuring a GRIN lens. PMID:22612122

Bahrami, Mehdi; Goncharov, Alexander V

2012-05-01

213

Padé approximant for refractive index and nonlocal envelope equations  

NASA Astrophysics Data System (ADS)

Padé approximation is superior to Taylor expansion when functions contain poles. This is especially important for response functions in complex frequency domain, where singularities are present and intimately related to resonances and absorption. Therefore, we introduce a rational Padé approximant for the complex medium refractive index n(?). The approximant is calculated using only local information of medium dispersion properties close to a carrier frequency ?0. In return it typically offers an accurate global representation of medium dispersion and absorption. Moreover, the fulfillment of the causality principle and the Kramers-Kronig relation can be established. In practice, our results are relevant if n(?) is known only for ???0 whereas optical field is spectrally broad such that (i) the resonance absorption becomes important and (ii) a traditional polynomial dispersion operator diverges and induces huge errors. As an exemplary application we use the approximant to derive a nonlocal envelope model for ultrashort pulses. The model provides a natural bridge between the commonly used local envelope equations and the most general non-envelope models operating directly with the electric field.

Amiranashvili, Sh.; Bandelow, U.; Mielke, A.

2010-02-01

214

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

SciTech Connect

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

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

2006-10-15

215

Determination of the refractive index of highly scattering human tissue by optical coherence tomography  

NASA Astrophysics Data System (ADS)

We describe two new techniques, based on optical coherence tomography (OCT), for determining the refractive index of highly scattering human tissue. We obtained refractive indices of in vitro human tissue, using OCT to measure the physical and optical path lengths of the sample. We obtained measurements of the refractive index of in vitro and in vivo human tissue, using OCT to track the focal length shift that results from translating the focus along the optic axis within the tissue. The refractive indices of human skin, adipose, and muscle were measured and compared with previously published estimates.

Tearney, G. J.; Brezinski, M. E.; Southern, J. F.; Bouma, B. E.; Hee, M. R.; Fujimoto, J. G.

1995-11-01

216

Refractive index changes of a donor impurity in spherical nanostructures: Effects of hydrostatic pressure and temperature  

NASA Astrophysics Data System (ADS)

The effects of hydrostatic pressure and temperature on the linear, nonlinear and total refractive index (RI) changes of a hydrogenic impurity in the center of spherical quantum dot (QD) and quantum anti-dot (QAD) have been investigated. The comparative approach is used for presenting the results of both models. Our numerical results indicate that the RI changes are considerably sensitive to the value of pressure and temperature. It is found that by increasing the pressure and temperature, the RI curves corresponding to QD and QAD are considerably different in shapes and behaviors. Also, our results show that the temperature increasing imposes the opposite effects than the pressure increasing to the both models.

Naimi, Y.

2013-11-01

217

Color Generation and Refractive Index Sensing Using Diffraction from 2D Silicon Nanowire Arrays.  

PubMed

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

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

2013-06-19

218

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

219

Specially designed long period grating with internal geometric bending for enhanced refractive index sensitivity  

NASA Astrophysics Data System (ADS)

We propose a long period grating (LPG) characterized by specially designed refractive index (RI) profile in which each grating plane is tilted at increasing angles, as moving away from the center of symmetry of the structure towards its both edges. This internally manufactured geometric structure, which basically simulates the bending of an optical fiber, increases the RI sensitivity of an LPG to the external medium. We experimentally demonstrate a three-fold improvement in the RI sensitivity, thus providing the basis for another step forward in the field of RI sensors based on optical fiber gratings.

Chiavaioli, F.; Trono, C.; Baldini, F.

2013-06-01

220

Measuring the refractive index on a goniometer in the dynamic regime  

NASA Astrophysics Data System (ADS)

Goniometers with ring lasers and other automatic goniometers operate in the dynamic regime, i.e., they have a continuously rotating object table with a prism. This article is devoted to a new method of measuring the refractive index of materials on a dynamic goniometer using the least-deviation method. The material carrier of unit refractive index is a sample in the form of a triangular prism or a liquid placed in a cell in the form of a hollow triangular prism. The fundamental optical layout of the measurement method is shown, and its metrological characteristics are considered. The proposed measurement method is implemented in the State Primary Standard Unit Refractive Index.

Vishnyakov, G. N.; Levin, G. G.; Kornysheva, S. V.; Zyuzev, G. N.; Lyudomirskii, M. B.; Pavlov, P. A.; Filatov, Yu. V.

2005-12-01

221

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

NASA Astrophysics Data System (ADS)

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

Xu, Linlin; Li, Ying; Li, Baojun

2012-10-01

222

Hybrid plasmonic biosensor for simultaneous measurement of both thickness and refractive index  

NASA Astrophysics Data System (ADS)

A novel hybrid plasmonic biosensor using a sub-wavelength reflection metal grating is proposed and analyzed. The simulation results show that the hybrid plasmonic-cavity (HPCM) are wavelength dependent on both the refractive index (RI) and thickness of the surrounding analyte layer, with a sensitivity of 448 nm/RIU (refractive index unit) and 75 nm/?m, respectively. However wavelength related to the cavity resonant mode (CRM) is only sensitive to the environmental refractive index changes. In principle it is possible to determine both RI and thickness of the coating layer simultaneously.

Ma, Youqiao; Farrell, Gerald; Semenova, Yuliya; Chan, Hau Ping; Wu, Qiang

2013-09-01

223

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

SciTech Connect

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

Chen Jihuan; Zhao Jiarong; Huang Xuguang; Huang Zhenjian

2010-10-10

224

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

225

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

SciTech Connect

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

Skarka, V. [Laboratory POMA, CNRS FRE 2988, University Angers, 2, Boulevard Lavoisier, F-49045 Angers (France); Aleksic, N. B. [Institute of Physics, Pregrevica 118, 11000 Belgrade (Serbia); Berezhiani, V. I. [Andronikashvili Institute of Physics, 6 Tamarashvili, Tbilisi 0177 (Georgia)

2010-04-15

226

Effect of Thin Metallic Layers on the Refractive Index of a Multilayer System  

NASA Astrophysics Data System (ADS)

We present a simplified structure made of periodic metallic layers on a glass substrate, which offers a potentially simpler approach to building photonic crystals. Using microwave experiments and Fresnel formulas, we investigate the refractive index properties of these structures. We make both transmission and reflection measurements and find that the refractive index of a periodic layered media decreases depending on the periodicity of the geometric arrangement, dielectric contrast and filling fraction of metallic layers. It is shown that metallic layers lead to a substantial change of interference pattern which can be interpreted as a result of interference in a uniform medium with a refractive index smaller than 1.

Ozturk, A.; Suleymanli, R.; Aktas, B.; Teber, A.

2012-02-01

227

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

228

Analysis on the saturation of refractive index modulation in fiber Bragg gratings (FBGs) written by partially coherent UV beams.  

PubMed

We present an analysis on the saturation of refractive index modulation of fiber Bragg gratings written in nonhydrogenated Ge-B co-doped single-mode photosensitive optical fiber by partially coherent pulsed UV beams. The UV beams of different spatial coherence properties were generated by second harmonic conversion of high repetition rate, high average power copper vapor laser (CVL) oscillators with different optical resonators. It is observed that for UV beams of higher spatial coherence, the fiber Bragg grating reflectivity growth was faster and saturation of refractive index modulation was higher. The experimental results are explained with the help of a physical model based on exponential decay of defect centers per unit volume on UV absorption in the fiber core. The subsequent increase in the refractive index was attributed to the structural modification and densification of the fiber core. PMID:22534886

Mahakud, Ramakanta; Prakash, Om; Nakhe, Shankar V; Dixit, Sudhir Kumar

2012-04-20

229

Measurements of strain-induced refractive index changes in shocked LiF using laser-driven flyer plates  

NASA Astrophysics Data System (ADS)

The refraction index of compressed LiF directly affects the accuracy of VISAR experiments that use LiF windows. We report on experiments at the LLNL Janus laser that reproduced previous measurements of strain-induced changes to the refractive index. Here laser-driven ramp-compression is used to accelerate aluminum flyer plates that impact a LiF window. The resultant particle velocity is inferred by measuring the flyer velocity just before impact. VISAR measurements through the LiF window provide an `apparent' particle velocity that can be used to infer the refractive index of the shock-compressed LiF. This is the first demonstration of the laser-driven flyer-plate technique applied to a measurement. We discuss how this technique will be implemented on the OMEGA laser to increase the pressures that can be achieved.

Fratanduono, Dayne; Barrios, Maria; Boehly, Tom; Meyerhofer, David; Hicks, Damien; Celliers, Peter; Eggert, Jon; Collins, G.

2009-06-01

230

On the relationship between Bloch modes and phase-related refractive index of photonic crystals.  

PubMed

It has previously been shown that the phase-related refractive index is positive in photonic crystals that display negative refraction at higher bands. We hypothesize that the phase velocity is governed by a wave that can be related to the dominant Bloch mode. This dominant wave can be identified from an approximate solution of Maxwell Equations using a homogeneously averaged dielectric constant and the dominant wavevector is related to the fundamental wavevector and the reciprocal lattice vectors. We validate this hypothesis by numerical Fourier decomposition of the field in the entire simulation domain. It confirms that for negative refraction at higher bands, the phase-related refractive index is indeed positive and differs significantly from the negative value of effective refractive index calculated from the band structure. PMID:19550583

Sun, Guilin; Kirk, Andrew G

2007-10-01

231

Interfacial refractive index sensing using visible-excited intrinsic zinc oxide photoluminescence coupled to whispering gallery modes  

NASA Astrophysics Data System (ADS)

Whispering gallery modes (WGMs) excited by the intrinsic photoluminescence (PL) in zinc oxide microspherical resonators are investigated in this work. The microspheres were synthesized via a one-pot hydrothermal technique. A polymer was applied after the synthesis to fill remaining pores in the oxide particle. Defect-related ZnO PL was excited in the visible, coupling to WGMs. The observed WGMs red-shift with increasing refractive index of the surrounding medium with a sensitivity of 90-100 nm/refractive index unit. The spherical microresonators may be used to investigate binding to and structure at the particle/solution interface.

Moirangthem, Rakesh Singh; Erbe, Andreas

2013-07-01

232

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

233

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

Microsoft Academic Search

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

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

2010-01-01

234

Positive phase evolution of waves propagating along a photonic crystal with negative index of refraction  

Microsoft Academic Search

We analyze propagation of electromagnetic waves in a photonic crystal at frequencies at which it behaves as an effective medium with a negative index in terms of refraction at its interface with free space. We show that the phase evolution along the propagation direction is positive, despite the fact that the photonic crystal displays negative refraction following Snell's law, and

Alejandro Martínez; Javier Martí

2006-01-01

235

One-dimensional photonic crystals with a sawtooth refractive index: another exactly solvable potential  

NASA Astrophysics Data System (ADS)

Exact analytical results expressed in terms of Bessel functions for the bandgaps, reflectance and transmittance of one-dimensional photonic crystals with a sawtooth refractive index profile on the period are derived, to our knowledge for the first time. This extends the set of exactly solvable models with periodic refractive indices. Asymptotic approximations to the above exact results have been also obtained.

Morozov, G. V.; Sprung, D. W. L.; Martorell, J.

2013-10-01

236

A Comparison of Kretschmann-Raether Angular Regimes for Measuring Changes in Bulk Refractive Index  

SciTech Connect

We compare 2 angular regimes for the measurement of changes in the real refractive index of bulk fluid analytes. The measurements are based on the use of the Kretschmann-Raether configuration to sense a change in reflectivity with index. Specifically, we numerically simulate the relative sensitivities of the total internal reflection (TIR) and surface-plasmon resonance (SPR) regimes. For a fixed-angle apparatus, the method which gives the greatest change in reflectivity varies with metal film thickness. For films thicker than the skin depth, the SPR regime is the most sensitive to index changes. For thinner films, however, the TIR angle is then dominant, with increases in sensitivity on the order of 75% for 10 nm gold or silver media.

KASUNIC, K.J.

1999-09-16

237

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

PubMed Central

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

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

2008-01-01

238

Cryogenic refractive index and coefficient of thermal expansion of S-TIH1 glass  

NASA Astrophysics Data System (ADS)

The S-TIH1 glass from Ohara Inc. is a type of material that exhibits a high room-temperature refractive index as well as a wide variation in dispersion as a function of wavelength. Because of these properties, this material could be a suitable candidate for use in a refractive system based on a prism design. In order to broaden its applicable uses, this paper reports on the results from a temperature-dependent refractive index measurement program performed on this type of glass to enable a high-fidelity refractive system design that would operate at cryogenic temperatures. These measurements were performed using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at the Goddard Space Flight Center (GSFC). We report on the absolute refractive index and thermo-optic coefficient (dn/dT ) at temperatures ranging from 100 to 300 K and at wavelengths from 0.455 to 2.536 ?m. We compare our index of refraction measurements to the material manufacturer's data at room temperature. We also provide temperature-dependent Sellmeier coefficients based on our measured data to allow accurate interpolation of index as a function of wavelength and temperature. These studies are also complemented with measurements of the coefficient of thermal expansion (CTE) to further validate the use of this type of glass in a cryogenic optical systems.

Quijada, Manuel A.; Leviton, Douglas B.; Content, David A.

2013-09-01

239

Dielectric effect of changes of refractive index in a Mg based II-VI semiconductor nanostructure  

NASA Astrophysics Data System (ADS)

Dielectric confinement on exciton binding energy is investigated taking into account the geometrical confinement and the Mg incorporation in MgSe/Zn1-xMgxSe//MgSe quantum well. The effect of mismatch between the dielectric constants between the well and the barrier is considered throughout the problem. Changes of refractive index as a function of photon energy for various Mg composition in the quantum well are investigated with and without the inclusion of dielectric confinement. The result shows that the resonant peak moves towards the blue region when the Mg alloy content is increased.

Hudson Mark, J. Abraham; Peter, A. John

2013-02-01

240

Understanding the mechanism of refractive index modulation in materials undergoing photo-Fries rearrangement  

NASA Astrophysics Data System (ADS)

Molecules and polymers that undergo a photo-Fries rearrangement are studied by using DFT calculation in order to predict the refractive index modulation which accompanies this light induced process. In particular, monomeric units of polystyrene derivatives (such as poly(p-formyloxystyrene) and poly(4-acetoxystyrene)) are considered and the refractive index calculated starting from the molecular polarizability and following the Lorentz-Lorenz approach. The results demonstrate that the conversion of ester groups to ketone/alcohol provides just a small modulation of the refractive index that does not fit the experimental results reported in the literature. A change in material density is therefore considered as main source of the modulation of the refractive index. Theoretical and experimental evidences are reported to support the picture.

Zanutta, Alessio; Colella, Letizia; Bertarelli, Chiara; Bianco, Andrea

2013-10-01

241

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

NASA Astrophysics Data System (ADS)

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

Deng, Yanzhuo; Li, Bincheng

1998-02-01

242

O the Feasibility of Using Satellite Doppler Data for Predicting AN Atmospheric Index of Refraction Profile  

Microsoft Academic Search

Doppler data are collected from orbiting Navy Navigation Satellites. If an atmospheric index of refraction profile can be predicted from the Doppler data, then the location of ducting layers, which bend radar rays around the earth, thus creating radar \\

Adrienne Marie Dare

1985-01-01

243

Long-term measurements of refractive index structure constant in atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

Results of long-term measurements of the refractive index structure constant in the boundary layer are introduced. The measurements were made on a 150-meter-high lattice mast equipped by nineteen meteorological sensors and one pressure sensor at the bottom of the mast. The Kolmogorov statistical theory of turbulence was used to calculate the refractive index structure constant C2n, allowing us to present annual cumulative distribution functions (CDFs) and seasonal quantiles. The quantiles of measured height dependence of the refractive index structure constant are also shown and compared with existing models (Hufnagel/Andrews/Phillips, SLC Day and Gurvich). Parameters of a linear model were calculated to fit the measured median height profile of the refractive index structure constant with the uncertainty of measurements also being addressed.

Jicha, Otakar; Pechac, Pavel; Zvanovec, Stanislav; Grabner, Martin; Kvicera, Vaclav

2012-10-01

244

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

245

Simultaneous measurement of refractive index and thickness of transparent material by dual-beam confocal microscopy  

NASA Astrophysics Data System (ADS)

We propose and demonstrate a novel technique, termed dual-beam confocal microscopy, for the simultaneous measurement of the refractive index and geometrical thickness of a single layer. The technique is based on the creation of two closely spaced lateral confocal gates for the two orthogonal polarization states of a laser beam in a sample via a Nomarski prism. Thereafter, by applying Gaussian beam theory, the refractive index can be determined with an error of 1% or less for a commercial cover glass. Based on the measured refractive index, the thickness of the sample can also be calculated. To verify the proposed methodology and optical setup, a microlens array was scanned, with the surface profile and refractive index subsequently compared with their catalog specifications.

Kuo, Wen-Chuan; Bou, Yu-Ki; Lai, Chih-Ming

2013-07-01

246

Non-magnetic System with Negative Index of Refraction for Terahertz Application  

Microsoft Academic Search

We propose a non-magnetic system with negative refraction index for terahertz applications. The system is based on a planar metallic waveguide with bismuth core, and uses strong anisotropy of bismuth permittivity and its ultra-low losses

Leo Alekseyev; Viktor A. Podolskiy; Evgenii E. Narimanov

2005-01-01

247

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

248

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

NASA Astrophysics Data System (ADS)

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

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

2006-01-01

249

Viscosity and refractive index of follicular fluid in relation to in vitro fertilization  

Microsoft Academic Search

Purpose: To set the standard values of follicular fluid viscosity and refractive index, and to investigate a possible relationship between these physiological parameters and the outcome of in vitro fertilization treatment.

Benjamin Fisch; Linda Harel; Shoshana Amit; Ruth Kaplan-Kraicer; Naomi Mor; Yona Tadir; Jardena Ovadia; Paul Merlob

1996-01-01

250

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

Microsoft Academic Search

The condition for a negative index of refraction with respect to the vacuum index is established in terms of permittivity and permeability susceptibilities. It is found that the imposition of analyticity to satisfy the Kramers-Kronig relations is a sufficiently general criterion for a physical negative index. The satisfaction of the Kramers-Kronig relations is a manifestation of the principle of causality

Alkim Akyurtlu; Adil-Gerai Kussow

2010-01-01

251

Change in the refractive index of a photorefractive crystal during formation of a spatially screened soliton  

SciTech Connect

A change in the refractive index of a photorefractive barium-sodium niobate crystal in an alternating electric field during the propagation of intensity-modulated coherent radiation in it is studied. It is shown experimentally that a change in the refractive index in the soliton regime in a photorefractive crystal with a small nonlocal response is independent of the external-field amplitude and intensity-modulation depth. (nonlinear-optics phenomena)

Assel'born, Sergei A; Kundikova, Nataliya D; Novikov, Igor' V [University Academic Division of Nonlinear Optics, Institute of Electrophysics, Ural Division, Russian Academy of Sciences, South Ural State University, Chelyabinsk (Russian Federation)

2010-02-28

252

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

Microsoft Academic Search

We present a temperature-dependent Sellmeier equation for the refractive index of stoichiometric LiTaO3. The extraordinary refractive index, for the range 0.39-4.1 mum and for temperatures of 30-200 °C, are based on previously published data [Jpn. J. Appl. Phys. 41, 465 (2002)] and on measured data derived from quasi-phase-matched (QPM) resonances. We used the new Sellmeier coefficients that we obtained to

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

2003-01-01

253

Spin angular momentum transfer from TEM(00) focused Gaussian beams to negative refractive index spherical particles.  

PubMed

We investigate optical torques over absorbent negative refractive index spherical scatterers under the influence of linear and circularly polarized TEM(00) focused Gaussian beams, in the framework of the generalized Lorenz-Mie theory with the integral localized approximation. The fundamental differences between optical torques due to spin angular momentum transfer in positive and negative refractive index optical trapping are outlined, revealing the effect of the Mie scattering coefficients in one of the most fundamental properties in optical trapping systems. PMID:21833372

Ambrosio, Leonardo A; Hernández-Figueroa, Hugo E

2011-07-22

254

Active modulation of refractive index by stress in the terahertz frequency range.  

PubMed

Experimental tests are presented to investigate the stress effect on terahertz (THz) waves with a THz time-domain spectroscopy system. Through the Jones matrix method, an experimental principle is derived according to the experimental system. Experimental results indicate the linear relationship between a polytetrafluoroethylene refractive index and applied stress. The result can be applied to the active modulation of a refractive index or phase of a THz wave. PMID:24085099

Li, Lin'an; Song, Wei; Wang, Zhiyong; Wang, Shibin; He, Mingxia; Han, Jiaguang; Cong, Longqing

2013-09-01

255

Measuring refractive index profiles of integrated LiNbO3 waveguides  

NASA Astrophysics Data System (ADS)

A nondestructive technique that provides near-field measurements as well as refractive index profiles and geometry of waveguides in LiNbO3 within a few minutes is demonstrated. It is a modification of the refracted-near-field (RNF) method well known for optical fiber characterization. Spatial resolution below 1 micrometers is achieved. The index resolution is about 2 X 10-4, the reproducibility better than 7%. A new calibration method for RNF measurement is introduced.

Groebli, Barbara; Gisin, Bernard; Gisin, Nicolas; Zbinden, Hugo

1995-08-01

256

Numerical simulations of negative-index refraction in wedge-shaped metamaterials  

Microsoft Academic Search

A wedge-shaped structure made of split-ring resonators (SRR) and wires is numerically simulated to evaluate its refraction behavior. Four frequency bands, namely, the stop band, left-handed band, ultralow-index band, and positive-index band, are distinguished according to the refracted field distributions. Negative phase velocity inside the wedge is demonstrated in the left-handed band and the Snell's Law is conformed in terms

Z. G. Dong; S. N. Zhu; H. Liu; J. Zhu; W. Cao

2005-01-01

257

Holographic coherence tomography for measurement of three-dimensional refractive-index space  

NASA Astrophysics Data System (ADS)

A new tomographic method for the measurement of three-dimensional refractive-index fields of transparent media, which we call holographic coherence tomography and which combines double-exposure holographic interferometry with the detecting style of optical coherence tomography, has been developed. The three-dimensional refractive-index field can be achieved with a confocal lens system by continual longitudinal and horizontal scanning of the holographic reconstruction image.

Lu, Yang; Lei, Hua; Pan, Qinmin; Liu, Zhengdong; Rempel, Garry L.

2002-07-01

258

Large refractive index change induced by ion implantation in lithium niobate  

Microsoft Academic Search

Large but negative refractive index change (? 10% at 632.8-nm line) is observed in several lithium niobate samples, each occurring in a thin layer induced by implantation of argon or neon ions. Implantation energy is 60 kV and the ion dose is 1016 cm?2 or more in each sample. Mechanisms causing the refractive index change and possible applications for integrated

David T. Y. Wei; William W. Lee; Louis R. Bloom

1974-01-01

259

Large refractive index change induced by ion implantation in lithium niobate  

Microsoft Academic Search

Large but negative refractive index change (~ 10% at 632.8-nm line) is observed in several lithium niobate samples, each occurring in a thin layer induced by implantation of argon or neon ions. Implantation energy is 60 kV and the ion dose is 1016 cm-2 or more in each sample. Mechanisms causing the refractive index change and possible applications for integrated

David T. Y. Wei; William W. Lee; Louis R. Bloom

1974-01-01

260

Effect of binders on the damage threshold and refractive index of coatings prepared from colloidal suspensions  

SciTech Connect

Addition of polyvinyl alcohol (PVA) to aqueous suspensions of AlOOH, ZrO2 and HfO{sub 2} has been found to increase the damage threshold and refractive index of coatings prepared from these suspensions. The increase in damage threshold may be due to the increase in coating strength brought about by the enhanced particle-to-particle bond strength due to the polymer binder. The binder also increases the refractive index by decreasing the porosity. This leads to a reduction in the number of layer pairs required for high reflection in a typical HR coating. A mirror consisting of only ten layer pairs of HfO{sub 2}-SiO{sub 2} with PVA binder in the HfO{sub 2} had a reflectivity of over 99% at 1.06 {mu}m and a damage threshold of 25-28 J/cm{sup 2}at 1.06 {mu}m with a 10 ns pulse. 6 refs, 5 figs, 4 tabs.

Thomas, I.M.

1992-10-01

261

Effect of binders on the damage threshold and refractive index of coatings prepared from colloidal suspensions  

SciTech Connect

Addition of polyvinyl alcohol (PVA) to aqueous suspensions of AlOOH, ZrO2 and HfO[sub 2] has been found to increase the damage threshold and refractive index of coatings prepared from these suspensions. The increase in damage threshold may be due to the increase in coating strength brought about by the enhanced particle-to-particle bond strength due to the polymer binder. The binder also increases the refractive index by decreasing the porosity. This leads to a reduction in the number of layer pairs required for high reflection in a typical HR coating. A mirror consisting of only ten layer pairs of HfO[sub 2]-SiO[sub 2] with PVA binder in the HfO[sub 2] had a reflectivity of over 99% at 1.06 [mu]m and a damage threshold of 25-28 J/cm[sup 2]at 1.06 [mu]m with a 10 ns pulse. 6 refs, 5 figs, 4 tabs.

Thomas, I.M.

1992-10-01

262

Highly sensitive refractive index sensor based on adiabatically tapered microfiber long period gratings.  

PubMed

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

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

2013-10-17

263

Low loss two-step ion-exchanged waveguides with high surface refractive index  

NASA Astrophysics Data System (ADS)

Two-step ion-exchanged waveguides with high surface refractive indices are fabricated under a variety of conditions. By modifying the conventional two-step ion exchange, the losses and the effective diffusion depth can be decreased without a significant effect on the surface refractive index. The influence of the first step, K+-Na+ ion exchange, performed time dependably on the surface refractive index change is investigated. Energy-dispersive x-ray spectroscopy is performed to establish the diffusion profiles of various ions.

Hassanzadeh, Abdollah; Mittler, Silvia

2011-07-01

264

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

SciTech Connect

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

Petrin, A. B. [Russian Academy of Sciences, Joint Institute of High Temperatures (Russian Federation)], E-mail: a_petrin@mail.ru

2008-09-15

265

Estimating Refractive Index Spectra in Regions of Clear Air Turbulence  

Microsoft Academic Search

Estimates of the spectrum of refractivity fluctuations to be expected in regions of clear turbulence are shown for scales in the inertial subrange. Based on the complete analysis by Atlas et al., it is concluded that radar detection of clear air turbulence with current technology is unlikely for all but inversion conditions. However, the present analysis can be used to

J. J. Stephens; E. R. Reiter

1967-01-01

266

Press-patterned UV-curable high refractive index coatings  

Microsoft Academic Search

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

Robert Morford; Wu-Sheng Shih; JoElle Dachsteiner

2006-01-01

267

Resolving the wave vector in negative refractive index media  

Microsoft Academic Search

We address the general issue of resolving the wave vector in complex electromagnetic media including negative refractive media. This requires us to make a physical choice of the sign of a square root imposed merely by conditions of causality. By considering the analytic behavior of the wave vector in the complex plane, it is shown that there are a total

S. Anantha Ramakrishna; Olivier J. F. Martin

2005-01-01

268

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

PubMed

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

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

2012-11-19

269

Measurement of Index of Refraction using Low-Coherence Interferometry*  

NASA Astrophysics Data System (ADS)

The indices of refraction of various materials were measured in a Michelson interferometer using several low-coherence light sources and compared to the values measured by other methods. This measurement technique yielded a value of n = 1.47 for quartz and n=1.33 (660 nm) and n = 1.32 (940 nm) for water. The effects of dispersion in thick samples and other sources of error were also modeled and investigated. This technique will be used to measure the indices of refraction of various ocular tissues and compared with those available in the literature. * This work was supported by the NSF sponsored Center for Biophotonics Science and Technology (CBST) at UC Davis. * The support by the UTSA Faculty Development Leave is duly acknowledged. * This work was also supported by NIH MARC-U*STAR Grant: GM07717.

Dickerson, Joshua

2005-03-01

270

Topology of relativistic refractive index surfaces for electron cyclotron waves  

Microsoft Academic Search

The dispersion of electron cyclotron waves in a weakly relativistic Maxwellian plasma is investigated. It is shown that the apparently very complicated picture of the coupling of the extraordinary (X) mode to Bernstein waves can be accounted for in a simple way by considering the refractive indices as Riemann-like surfaces in the Clemmow-Mullaly-Allis (CMA) parameter space, ( omega p2\\/ omega

J. Egedal; H. Bindslev

1994-01-01

271

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

PubMed

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

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

2012-11-01

272

Fundamental processes of refractive index modifications during femtosecond laser waveguide writing  

NASA Astrophysics Data System (ADS)

By using focused ultrashort pulsed laser radiation refractive index modifications are induced in glass in order to generate optical components. The understanding of physically fundamental processes induced by laser radiation is the basis for the systematic control and maximization of the refractive index change for the realization of three-dimensional, optical components for integrated optics like in-volume waveguides. In this paper fundamental processes which are induced by focused laser radiation in the volume of borosilicate glass D263 and fused silica are investigated. The glass materials are structured by laser radiation in the infrared spectral range (?=1045nm). By using femtosecond laser pulses with high repetition rates (f = 500 kHz), thermal processes like heat accumulation effects are induced leading to heat affected zones and thus waveguide cross sections with dimensions larger than the focal spot. The absorptivity during modification in relation to the applied pulse energy is measured for different repetition rates in both glass materials. Furthermore, the laser induced structural change in the glass matrix by the increase of three- and four-membered ring structures is proved with Raman spectroscopy.

Schaefer, D.; Schnitzler, D.; Kelbassa, I.

2013-03-01

273

Simple fiber optic refractive index sensor based on evanescent higher order modes  

NASA Astrophysics Data System (ADS)

This paper presents an optical fiber refractive index sensor based on the evanescent higher order modes. Its structure and principle are quite simple. The sensor is composed of two segments of optical fibers that are spliced together. An ordinary multimode fiber with a core diameter of 50 ?m is used to input the light. The functions of a second multimode fiber with a core diameter of 200 ?m are twofold. In the region of the splice, a section of the cladding a few centimetre long is removed by an electrical discharge. This part works as a sensing element, and the rest of the fiber is used to output the light. Once the light travels though the input fiber and crosses the splice to enter the second fiber, numerous modes both guided and leaky are generated due to the abrupt increase of the core diameter. The evanescent light fields of these guided modes are sensitive to changes in the refractive index of the material surrounding the fiber cladding. The evanescent field change directly causes a change in the output light intensity. The developed sensor is compact in size, simple to fabricate, promising in performance, and has a high potential for practical applications.

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

2009-06-01

274

Refractive Index and Hygroscopic Stability of Al(x)Ga(1-x)As Native Oxides  

SciTech Connect

The authors present prism coupling measurements on Al{sub x}Ga{sub 1{minus}x}As native oxides showing the dependence of refractive index on composition (0.3 {le} x {le} 0.97), oxidation temperature (400 {le} T {le} 500), and carrier gas purity. Index values range from n = 1.490 (x = 0.9, 400) to 1.707 (x = 0.3, 500 C). The oxides are shown to adsorb moisture, increasing their index by up to 0.10 (7%). Native oxides of Al{sub x}Ga{sub 1{minus}x}As (x {le} 0.5) have index values up to 0.27 higher and are less hygroscopic when prepared with a small amount of O{sub 2} in the N{sub 2} + H{sub 2}O process gas. The higher index values are attributed to a greater degree of oxidation of the Ga in the film.

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

1999-07-08

275

Image Contrast Immersion Method for Measuring Refractive Index Applied to Spider Silks.  

National Technical Information Service (NTIS)

A technique for measuring the refractive index of micron sized fibers using a series of immersion index matching oils, and image contrast measurements is proposed and demonstrated. It has been applied to radial silks of the orb web weaving spider Plebs eb...

D. J. Little D. M. Kane

2011-01-01

276

Low-loss single-layer metamaterial with negative index of refraction at visible wavelengths  

Microsoft Academic Search

We present a structure exhibiting a negative index of refraction at visible or near infrared frequencies using a single metal layer. This contrasts with recently developed structures based on metal-dielectric-metal composites. The proposed metamaterial consists of periodically arranged thick stripes interacting with each other to give rise to a negative permeability. Improved designs that allow for a negative index for

C. García-Meca; R. Ortuño; R. Salvador; A. Martínez; J. Martí

2007-01-01

277

Negative index of refraction, perfect lenses and transformation optics - some words of caution  

Microsoft Academic Search

In this paper we show that a negative index of refraction is not a direct implication of transformation optics with orientation-reversing diffeomorphisms. Rather, a negative index appears due to a specific choice of sign freedom. Furthermore, we point out that the transformation designed lens, which relies on the concept of spacetime folding, does not amplify evanescent modes, in contrast to

Luzi Bergamin; Alberto Favaro

2010-01-01

278

Measurement of optical penetration depth and refractive index of human tissue  

NASA Astrophysics Data System (ADS)

Experimental techniques for measurement of optical penetration depth and refractive index of human tissue are presented, respectively. Optical penetration depth can be obtained from the measurement of the relative fluence-depth distribution inside the target tissue. The depth of normal and carcinomatous human lung tissues irradiated with the wavelengths of 406.7, 632.8 and 674.4 nm in vitro are respectively determined. In addition, a novel simple method based on total internal reflection for measuring the refractive index of biotissue in vivo is developed, and the refractive indices of skin from people of different age, sex and skin color are measured. Their refractive indices are almost same and the average is 1.533.

Xie, Shusen; Li, Hui; Li, Buhong

2003-01-01

279

Correlation between the nonlinear refractive index and structure of germanium-based chalcogenide glasses  

SciTech Connect

The nonlinear refractive index (n{sub 2}) of new germanium-based sulfo-selenide glasses has been measured at 1064 nm using Z-scan technique, with picosecond pulses emitted by a 10 Hz Q-switched mode-locked Nd:Yag laser. We have determined the impact of the progressive replacement of S by Se on the nonlinear properties of these glasses. The value of n{sub 2} strongly increases with the substitution of S by Se, up to 350 times the n{sub 2} for fused silica. X-ray photoelectron spectroscopy (XPS) indicates that the increase of Ge-Se bond units in the glass network is responsible for the increase of n{sub 2}. The suitability of these glasses for optical switching at telecommunication wavelengths based on such nonlinear properties has been also confirmed.

Petit, L. [School of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States)], E-mail: lpetit@clemson.edu; Carlie, N. [School of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States); Humeau, A.; Boudebs, G. [Laboratoire des Proprietes Optiques des Materiaux et Applications, UMR CNRS 6163, Universite d'Angers, 2 Boulevard Lavoisier, 49045 Angers Cedex 01 (France); Jain, H. [Center for Optical Technologies and Department of Materials Science and Engineering, Lehigh University, 5 E Packer Avenue, Bethlehem, PA 18015 (United States); Miller, A.C. [Center for Advanced Materials and Nanotechnology, Lehigh University, Bethlehem, PA 180015-1539 (United States); Richardson, K. [School of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States)

2007-12-04

280

Nonlinear refractive index of vanadate crystals in the near IR region  

NASA Astrophysics Data System (ADS)

We used the single-beam Z-scan method, employing picosecond laser pulses with ? = 1064 nm, to measure the nonlinear refractive index and nonlinear absorption in vanadate crystals, which are promising for design of laser sources. We have established that there is practically no nonlinear absorption in these crystals in the near IR range and that doping them with neodymium ions leads to a significant reduction in the nonlinear refraction. This effect can be used to partially compensate for the negative impact of nonlinear refraction on the lasing characteristics of lasers.

Vodchits, A. I.; Orlovich, V. A.; Apanasevich, P. A.

2012-01-01

281

Refractive index, optical dispersion, and group velocity of infrared waves in silica glass  

Microsoft Academic Search

An interferometric method was used for determination of the refractive index of silica glass in the infrared wavelength range by means of infrared spectroscopy. Refractive indices at the positions of successive interference fringes were determined in the wavelength region from 1.35 to 4.85?m. The value of dn\\/d? as a function of wavelength ? was evaluated which shows two maxima near

C. Z. Tan; J. Arndt

2001-01-01

282

Beam-deflection optical tomography of the refractive-index distribution based on the Rytov approximation.  

PubMed

A method of beam-deflection optical tomography based on the Rytov approximation of the wave equation is proposed. A linear relation between the deflection angle and the refractive-index distribution from the Rytov approximation and an equation of geometrical optics is derived. The tomographic reconstruction in this method is reduced to the solution of a system of linear equations. Experimental results show that this method can reconstruct strongly refracting fields from projection data of six view angles. PMID:20802750

Sasaki, O; Kobayashi, T

1993-02-10

283

A Spatial Beam Splitter Consisting of a Near-Zero Refractive Index Medium  

Microsoft Academic Search

A novel metamaterial-based beam splitter is demonstrated in this communication. The metamaterial is a three-dimensional (3 D) fishnet structure arranged in a two-dimensional (2 D) square lattice. According to Snell's law, the refracted wave from medium into air tends to be normal to the interface if the effective refractive index of medium is approximately zero. In light of this concept,

Ruey-Bing Hwang; Neng-Chieh Hsu; Cheng-Yuan Chin

2012-01-01

284

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

Microsoft Academic Search

The planar waveguides have been fabricated in z-cut beta barium metaborate crystals by 2.8MeV Si+ ion implantation with doses of 1×1015 and 3×1015ions\\/cm2 at room temperature. The waveguides were characterized by the prism-coupling method. The refractive index profiles were reconstructed using reflectivity calculation method. It is found that relatively large positive changes of extraordinary refractive indices happen in the guiding

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

2004-01-01

285

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

Microsoft Academic Search

We develop an approach to use nanostructured plasmonic materials as a non-magnetic negative-refractive index system at optical and near-infrared frequencies. In contrast to conventional negative refraction materials, our design does not require periodicity and thus is highly tolerant to fabrication defects. Moreover, since the proposed materials are intrinsically non-magnetic, their performance is not limited to proximity of a resonance so

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

286

Nonmagnetic nanocomposites for optical and infrared negative-refractive-index media  

Microsoft Academic Search

We develop an approach to use nanostructured plasmonic materials as a nonmagnetic negative-refractive-index system at optical and near-infrared frequencies. In contrast to conventional negative-refraction materials, our design does not require periodicity and thus is highly tolerant to fabrication defects. Moreover, since the proposed materials are intrinsically nonmagnetic, their performance is not limited to the proximity of a resonance, so the

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

2006-01-01

287

Transmission spectra of one-dimensional photonic crystals including negative-refractive-index media  

Microsoft Academic Search

We introduce a new model of one-dimensional (1D) photonic crystal composed of alternately arranged RHM and LHM layers with\\u000a positive and negative refractive indices respectively, for which the transmission spectra of the model are calculated numerically\\u000a with the transfer matrix method, and the bandgap structure and the polarization properties are analyzed. We found that the\\u000a introduction of negative refractive index

Xiao-Ming Shen; Xian-Feng Chen; Mei-Ping Jiang; Du-Fang Shi

2005-01-01

288

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

289

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

NASA Astrophysics Data System (ADS)

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

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

1996-04-01

290

Index of refraction for cold lithium- and diatomic sodium waves traveling through cold noble gases  

NASA Astrophysics Data System (ADS)

In the present paper we propose to measure the index of refraction for diatomic sodium molecules traveling through a cold helium gas. Theoretical calculations of the index of refraction for this system are presented as a function of the molecule velocity and atom gas temperature. Whereas previous theoretical efforts to compute the refractive index have been concerned with atomic systems and atomic matter waves, we extend the investigation to diatomic molecules in the present work. To enable such calculations the potential energy surface for the atom-molecule interaction is calculated ab initio, along with the long range dispersion coefficients for the atom-molecule system. The full close-coupled equations, describing the atom-molecule collisions, are solved numerically to work out the influence of the collisions on the matter waves. We investigate the sensitivity of the results upon changes and inaccuracies in the potential energy surface. Several molecular rotational levels are included in the present study, and the index of refraction is found to depend on the rotational state. In addition, the index of refraction for atomic lithium matter waves traveling through the cold noble gases helium and argon are computed, motivated by a recent experiment with atomic lithium matter waves. Different resonances (glory- and scattering resonances) are identified from the results. Such resonances offer an important opportunity for the comparison of experiment and theory.

Bjørgen, H.; Lysebo, M.; Veseth, L.

2011-02-01

291

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

292

Quantitative reconstruction of refractive index distribution and imaging of glucose concentration by using diffusing light  

NASA Astrophysics Data System (ADS)

We show that a two-step reconstruction method can be adapted to improve the quantitative accuracy of the refractive index reconstruction in phase-contrast diffuse optical tomography (PCDOT). We also describe the possibility of imaging tissue glucose concentration with PCDOT. In this two-step method, we first use our existing finite-element reconstruction algorithm to recover the position and shape of a target. We then use the position and size of the target as a priori information to reconstruct a single value of the refractive index within the target and background regions using a region reconstruction method. Due to the extremely low contrast available in the refractive index reconstruction, we incorporate a data normalization scheme into the two-step reconstruction to combat the associated low signal-to-noise ratio. Through a series of phantom experiments we find that this two-step reconstruction method can considerably improve the quantitative accuracy of the refractive index reconstruction. The results show that the relative error of the reconstructed refractive index is reduced from 20% to within 1.5%. We also demonstrate the possibility of PCDOT for recovering glucose concentration using these phantom experiments.

Liang, Xiaoping; Zhang, Qizhi; Jiang, Huabei

2006-11-01

293

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

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

294

Beat frequencies in a ring laser gyro with its refractive index over unity  

NASA Astrophysics Data System (ADS)

A frequency shift ?f during rotation in a ring laser gyro with its refractive index of unity was already well known. However, when the refractive index nr is over unity, several expressions for a beat frequency such as 2?f~nr, nr0, nr-1, and nr-2 were proposed. In this article, a beat frequency in a uniformly rotating ring laser gyro with nr>1 is calculated using nonrelativistic, special relativistic, and general relativistic theories. To the first order, all the results obtained from these theories show a common beat frequency, which is proportional to the refractive index nr, as far as the dispersion is neglected. When the dispersion is considered, the beat frequency is in proportion to nr0[1-(r?/?0)2(dnr/df)2]-1, where f is a frequency of a laser beam, ?0 is a wavelength of a laser beam when the ring laser stands still, and nr0 is a refractive index at ?0. If nr0=1-(r?/?0)2(dnr/df)2 is satisfied, the beat frequency seems to be independent of the refractive index.

Numai, Takahiro

2001-02-01

295

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

296

Reconstruction of refractive-index distribution in off-axis digital holography optical diffraction tomographic system.  

PubMed

In the paper the optical diffraction tomographic system for reconstruction of the internal refractive index distribution in optical fiber utilizing grating Mach-Zehnder interferometer configuration is explored. The setup applies afocal imaging. Conventional grating application gives, however, highly aberrated object beam producing incorrect refractive-index reconstructions. The grating inherent aberrations are characterized, its influence on both image projections and refractive index reconstructions is presented. To remove aberrations and enable tomographic reconstruction a novel digital holographic algorithm, correcting optical system imaging, is developed. The algorithm uses plane wave spectrum decomposition of optical field for solving diffraction problem between parallel and tilted planes and enabling correction of imaging system aberrations. The algorithm concept was successfully proved in simulations and the experiment. PMID:19654783

Kozacki, Tomasz; Krajewski, Rafal; Kujawi?ska, Ma?gorzata

2009-08-01

297

Interferometry with direct compensation of fluctuations of refractive index of air  

NASA Astrophysics Data System (ADS)

We present an experimental arrangement of an interferometric system designed to operate with full compensation for varying refractive index of air in the measuring axis. The concept is based on a principle where the wavelength of the laser source is derived not from an optical frequency of the stabilized laser but from a fixed length being a base-plate or a frame of the whole measuring setup. This results into stabilization of the wavelength of the laser source in atmospheric conditions to mechanical length of suitable etalon made of a material with very low thermal expansion. The ultra-low thermal expanding glass ceramic materials available on the market perform thermal expansion coefficients on the level 10-8 which significantly exceeds the limits of uncertainty posed by indirect evaluation of refractive index of air through Edlen formula. To verify the concept a tracking of laser frequency following the drift of refractive index has been performed.

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

2010-09-01

298

Measurement of Single Cell Refractive Index, Dry Mass, Volume, and Density Using a Transillumination Microscope  

PubMed Central

Phase contrast microscopy has become ubiquitous in the field of biology, particularly in qualitative investigations of cellular morphology. However, the use of quantitative phase retrieval methods and their connection to cellular refractive index and dry mass density remain under utilized. This is due in part to the restriction of phase and cellular mass determination to custom built instruments, involved mathematical analysis, and prohibitive sample perturbations. We introduce tomographic bright field imaging, an accessible optical imaging technique enabling the three dimensional measurement of cellular refractive index and dry mass density using a standard transillumination optical microscope. The validity of the technique is demonstrated on polystyrene spheres. The technique is then applied to the measurement of the refractive index, dry mass, volume, and density of red blood cells. This optical technique enables a simple and robust means to perform quantitative investigations of engineered and biological specimens in three dimensions using standard optical microscopes.

Phillips, Kevin G.; Jacques, Steven L.; McCarty, Owen J. T.

2013-01-01

299

Measuring the refractive index of transparent materials using high precision circular heterodyne interferometry  

NASA Astrophysics Data System (ADS)

This study measured a wide range of the refractive index of transparent glass with low phase error using precision circular heterodyne interferometry. We determined precision measurement conditions with theoretical error analysis. The findings showed that minimum phase error could be achieved through appropriate selections of the incident angle and azimuth angle of the analyzer. Using the proposed method, phase error could be estimated at better than 1×10-4. Error in refractive index measurements for each sample could be estimated at better than 1×10-4 under precision measurement conditions. In addition, the proposed method has the advantages of simple optical configuration, easy operation, and a wide measurement range of the refractive index of transparent materials.

Hsu, Cheng-Chih; Chen, Shu-Yu; Chen, Yi-Cheng

2012-12-01

300

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

301

Simple interferometer for evanescent field refractive index sensing as a feasibility study for an immunosensor.  

PubMed

We describe a fiber optic interferometric refractive index sensor to illustrate that, by using the evanescent field of an optical waveguide, a potentially very sensitive determination of changes in the refractive index on the waveguide surface can be obtained. These changes can, e.g., be the result of immunoreactions. We used a Mach-Zehnder interferometer configuration with a flow-through cuvette in one arm with a decladded multimode glass fiber of 0.6-mm diameter and 2-cm interaction length. The obtained resolution in measuring refractive index changes is 1 x 10-(3). We also developed the theory describing the sensitivity of this sensor using the modal and the geometrical ray description. PMID:20700308

Heideman, R G; Kooyman, R P; Greve, J; Altenburg, B S

1991-04-20

302

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 PMMA under shock loading. Flyer and target geometries allowed the measurement of shock velocity, particle velocity, and refractive index in the shocked state, using the simultaneous application of VISAR (532nm) and Het-V (1550nm). 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 characterise the accuracy of this assumption at peak stresses up to 2 GPa.

Chapman, David; Eakins, Daniel; Williamson, David; Proud, William

2011-06-01

303

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

304

Optical properties of a photopolymer with large refractive index modulation for holographic application  

NASA Astrophysics Data System (ADS)

Optical transparency and high diffraction efficiency are two essential factors for high performance of the photopolymer. Optical transparency mainly depends on the miscibility between polymer binder and photopolymerized polymer, while diffraction efficiency depends on the refractive index modulation between polymer binder and photopolymerized polymer. For most of organic materials, the large refractive index difference between two polymers accompanies large structural difference that leads to the poor miscibility and thus poor optical quality via light scattering. Therefore, it is difficult to design a high-performance photopolymer satisfying both requirements. In this work, we prepared a new phase-stable photopolymer with large refractive index modulation and investigated the optical properties. Our photopolymer is based on modified poly (methyl methacrylate) as a polymer binder, acryl amide as a photopolymerizable monomer, triethanolamine as initiator, and yellow eosin as a photosensitizer at 532nm. Diffraction efficiency over 85% and optical transmittance over 90% were obtained for the photopolymer.

Shin, Chang-Won; Kim, Nam; Kim, Won-Sun; Jeong, Yong-Cheol; Park, Jung-Ki

2004-10-01

305

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

SciTech Connect

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

Sakai, Osamu; Shimomura, Takuya; Tachibana, Kunihide [Department of Electronic Science and Engineering, Kyoto University, Kyoto-Daigaku Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan)

2010-12-15

306

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

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

307

Ferromagnetic wire lattice with a tunable negative index of refraction for microwaves using an external magnetic field  

Microsoft Academic Search

A new structure of negative-refractive-index material is proposed, which is composed of ferromagnetic wires setting in two-dimensional Bravais lattice (FWL) with the application of external magnetic field. The refractive index of the FWL consisting of ferrum wires arranged in square lattice is calculated. The refractive index exhibits negative value in the GHz region. A notable characteristic of the FWL is

Yun-Song Zhou; Ben-Yuan Gu; Fu-He Wang

2006-01-01

308

Characterization of a novel ultra low refractive index material for biosensor application  

PubMed Central

Nanoporous materials can provide significant benefits to the field of biosensors. Their size and porous structure makes them an ideal tool for improving sensor performance. This study characterized a novel ultra low index of refraction nanoporous organosilicate (NPO) material for use as an optical platform for fluorescence-based optical biosensors. While serving as the low index cladding material, the novel coating based on organosilicate nanoparticles also provides an opportunity for a high surface area coating that can be utilized for immobilizing biological probes. Biological molecules were immobilized onto NPO, which was spin-coated on silicon and glass substrates. The biological molecule was composed of Protein A conjugated to AlexaFluor 546 fluorophore and then immobilized onto the NPO substrate via silanization. Sample analysis consisted of spectrofluorometry, FT-IR spectroscopy, scanning electron microscopy, contact angle measurement and ellipsometry. The results showed the presence of emission peaks at 574 nm, indicating that the immobilization of Protein A to the NPO material is possible. When compared to Si and glass substrates not coated with NPO, the results showed a 100X and 10X increase in packing density with the NPO coated films respectively. Ellipsometric analysis, FT-IR, contact angle, and SEM imaging of the surface immobilized NPO films suggested that while the surface modifications did induce some damage, it did not incur significant changes to its unique characteristics, i.e., pore structure, wettability and index of refraction. It was concluded that NPO films would be a viable sensor substrate to enhance sensitivity and improve sensor performance.

Memisevic, Jasenka; Korampally, Venumadhav; Gangopadhyay, Shubhra; Grant, Sheila A.

2009-01-01

309

Characterization of a novel ultra low refractive index material for biosensor application.  

PubMed

Nanoporous materials can provide significant benefits to the field of biosensors. Their size and porous structure makes them an ideal tool for improving sensor performance. This study characterized a novel ultra low index of refraction nanoporous organosilicate (NPO) material for use as an optical platform for fluorescence-based optical biosensors. While serving as the low index cladding material, the novel coating based on organosilicate nanoparticles also provides an opportunity for a high surface area coating that can be utilized for immobilizing biological probes. Biological molecules were immobilized onto NPO, which was spin-coated on silicon and glass substrates. The biological molecule was composed of Protein A conjugated to AlexaFluor 546 fluorophore and then immobilized onto the NPO substrate via silanization. Sample analysis consisted of spectrofluorometry, FT-IR spectroscopy, scanning electron microscopy, contact angle measurement and ellipsometry. The results showed the presence of emission peaks at 574 nm, indicating that the immobilization of Protein A to the NPO material is possible. When compared to Si and glass substrates not coated with NPO, the results showed a 100X and 10X increase in packing density with the NPO coated films respectively. Ellipsometric analysis, FT-IR, contact angle, and SEM imaging of the surface immobilized NPO films suggested that while the surface modifications did induce some damage, it did not incur significant changes to its unique characteristics, i.e., pore structure, wettability and index of refraction. It was concluded that NPO films would be a viable sensor substrate to enhance sensitivity and improve sensor performance. PMID:20161155

Memisevic, Jasenka; Korampally, Venumadhav; Gangopadhyay, Shubhra; Grant, Sheila A

2009-08-18

310

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

311

Experimental verification of negative refraction for a wedge-type negative index metamaterial operating at terahertz  

NASA Astrophysics Data System (ADS)

We report on angle-resolved time domain spectroscopy (TDS) carried out on a prismlike negative index metamaterial operating around 0.5 THz. The wedge-type devices are constituted of hole arrays etched in gold thin films, which are stacked according to a sequential mask shift. By means of a goniometric TDS setup and subsequent analysis of the temporal waveforms, negative refraction is demonstrated with values close to n=-1 around 0.5 THz. The dispersion of refractive index retrieved from the Snell-Descartes law shows comparable trends in comparison with the dispersion deduced from complex transmission and reflection measurements on slab-type samples.

Wang, Shengxiang; Garet, Frédéric; Blary, Karine; Lheurette, Eric; Coutaz, Jean Louis; Lippens, Didier

2010-11-01

312

Experiment study on measurement of the optical fiber refractive index based on digital holography  

NASA Astrophysics Data System (ADS)

The characteristics of optical fiber are quite important for improving the performance in various application of the optical fiber including communication and sensor systems. Based on optical Mach-Zehnder interferometer, a new measuring method of optical fiber refractive index profiling using digital holography is proposed in this paper, which simplifies the experimental setup compared to traditional holography. Several kinds of fiber samples such as multimode fiber, polarization-preserving fiber and special fiber are tested and their holograms are recorded by CCD. After filtering of the hologram, the phase distribution of fiber sample can be reconstructed and extracted. At last the experimental results of refractive index profiling of fiber are given.

Wang, Duocheng; Chang, Zheng; Huang, Sujuan

2012-11-01

313

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

NASA Astrophysics Data System (ADS)

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

Olivares-Vargas, A.; Trejo-Durán, M.; Alvarado-Méndez, E.; Cornejo-Monroy, D.; Mata-Chávez, R. I.; Estudillo-Ayala, J. M.; Castaño-Meneses, V.

2013-09-01

314

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

PubMed

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

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

2010-11-23

315

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

316

Tailoring the behavior of optical microcavities with high refractive index sol-gel coatings.  

PubMed

Silica optical resonators with high quality factors, small mode volumes, and high refractive index contrast are desirable in many applications throughout the fundamental and applied sciences. However, these parameters are not easily modified in plain silica devices. In the present work, we theoretically and experimentally demonstrate the use of high refractive index sol-gel coatings to achieve a significant reduction in mode volume of silica toroids while maintaining high quality factors. In addition to tuning the mode volume, the presence of the coating changes both the location and shape of the optical field. PMID:22825153

Maker, Ashley J; Rose, Brian A; Armani, Andrea M

2012-07-15

317

High Performance Optical Coatings Utilizing Tailored Refractive Index Nanoporous Thin Films  

NASA Astrophysics Data System (ADS)

Refractive index is perhaps the most important quantity in optics. It is particularly relevant in the field of optical coatings, where the refractive index appears in virtually every optics equation as a figure of merit. Recently it has been demonstrated through control of the deposition angle during oblique-angle electron-beam deposition, nanoporous films of virtually any desired porosity may be accurately deposited. As the porosity of a nanoporous film directly relates to its effective refractive index, the refractive index value of a film may be tailored to any value between that of the bulk material and close to that of air. These two characteristics, namely; (i) tailored-refractive index and (ii) very low-refractive index values close to that of air, offer significant advantages in the design and optical performance in all optical coating applications. In this dissertation we explore optical coating applications whose performance can be greatly enhanced by utilization of a tailored- and low-refractive index nanoporous material system. One such important application is in the design and fabrication of broadband, omnidirectional antireflection (AR) coatings on solar cell devices. To harness the full spectrum of solar energy, Fresnel reflections at the surface of a photovoltaic cell must be reduced as much as possible over the relevant solar wavelength range and over a wide range of incident angles. However, the development of AR coatings embodying omni-directionality over a wide range of wavelengths is challenging. By utilizing the tailored- and low-refractive index properties of the nanoporous material system, in conjunction with a computational genetic algorithm and a predictive quantitative model for the porosity of such nanoporous films, truly optimized AR coatings can be designed and fabricated on solar cells. Here we show that these optimized AR structures demonstrate significant improvement to overall device efficiency. Traditionally, nanoporous films fabricated by oblique-angle deposition techniques have been restricted to rigid and planar substrates such as silicon and glass. This limitation greatly constrains the applicability, tailorability, functionality and even the economic viability of such nanoporous films. As another avenue into extending the applicability of such films, here we demonstrate a novel nanoporous film / polymer substrate composite system fabricated by utilizing oblique-angle electron-beam methodology. This unique composite system exhibits several favorable characteristics, namely i) fine-tuned control over film nano-porosity and thickness, ii) excellent adhesion between the nanoporous film and polymer substrate, iii) and ability to withstand significant and repeated bending as well as three dimensional molding, all the while closely retaining the composite system's designed nanostructure and optical properties. These newly available characteristics show promise to greatly extend the range of applications and functionalities of such nanoporous films.

Poxson, David J.

318

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

319

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

PubMed Central

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

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

2010-01-01

320

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

NASA Astrophysics Data System (ADS)

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

Willey, Ronald R.

2011-09-01

321

Nanonewton optical force trap employing anti-reflection coated, high-refractive-index titania microspheres  

NASA Astrophysics Data System (ADS)

Optical tweezers are exquisite position and force transducers and are widely used for high-resolution measurements in fields as varied as physics, biology and materials science. Typically, small dielectric particles are trapped in a tightly focused laser and are often used as handles for sensitive force measurements. Improvement to the technique has largely focused on improving the instrument and shaping the light beam, and there has been little work exploring the benefit of customizing the trapped object. Here, we describe how anti-reflection coated, high-refractive-index core-shell particles composed of titania enable single-beam optical trapping with an optical force greater than a nanonewton. The increased force range broadens the scope of feasible optical trapping experiments and will pave the way towards more efficient light-powered miniature machines, tools and applications.

Jannasch, Anita; Demirörs, Ahmet F.; van Oostrum, Peter D. J.; van Blaaderen, Alfons; Schäffer, Erik

2012-07-01

322

Optical absorption and refraction index change of a confined exciton in a spherical quantum dot nanostructure  

NASA Astrophysics Data System (ADS)

Electronic energies of an exciton confined in a strained Zn1- x Cd x Se/ZnSe quantum dot have been computed as a function of dot radius with various Cd content. Calculations have been performed using Bessel function as an orthonormal basis for different confinement potentials of barrier height considering the internal electric field induced by the spontaneous and piezoelectric polarizations. The optical absorption coefficients and the refractive index changes between the ground state ( L = 0) and the first excited state ( L = 1) are investigated. It is found that the optical properties in the strained ZnCdSe/ZnSe quantum dot are strongly affected by the confinement potentials and the dot radii. The intensity of the total absorption spectra increases for the transition between higher levels. The obtained optical nonlinearity brings out the fact that it should be considered in calculating the optical properties in low dimensional semiconductors especially in quantum dots.

Mathan Kumar, K.; John Peter, A.; Lee, C. W.

2011-12-01

323

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

324

The Role of Multiferroics in the Negative Index of Refraction  

Microsoft Academic Search

We explore the possibility of realizing intrinsic far infrared negative index materials (NIM) in multiferroic crystals (crystals simultaneously possessing a ferroelectric and ferromagnetic phase) possessing electric and magnetic dipole resonances with nearby resonance frequencies, or overlapping regions of negative permittivity and permeability. We demonstrate the functionality of such a material using finite difference time domain simulations. In order to motivate

David W. Ward; Eric Statz; Kevin J. Webb; Keith A. Nelson

2004-01-01

325

Generation of J0-Bessel-Gauss beam by a heterogeneous refractive index map.  

PubMed

In this paper, we present the theoretical studies of a refractive index map to implement a Gauss to a J(0)-Bessel-Gauss convertor. We theoretically demonstrate the viability of a device that could be fabricated on a Si/Si(1-y)O(y)/Si(1-x-y)Ge(x)C(y) platform or by photo-refractive media. The proposed device is 200 ?m in length and 25 ?m in width, and its refractive index varies in controllable steps across the light propagation and transversal directions. The computed conversion efficiency and loss are 90%, and -0.457 dB, respectively. The theoretical results, obtained from the beam conversion efficiency, self-regeneration, and propagation through an opaque obstruction, demonstrate that a two-dimensional (2D) graded index map of the refractive index can be used to transform a Gauss beam into a J(0)-Bessel-Gauss beam. To the best of our knowledge, this is the first demonstration of such beam transformation by means of a 2D index-mapping that is fully integrable in silicon photonics based planar lightwave circuits (PLCs). The concept device is significant for the eventual development of a new array of technologies, such as micro optical tweezers, optical traps, beam reshaping and nonlinear beam diode lasers. PMID:22751390

San-Roman-Alerigi, Damian P; Ng, Tien K; Zhang, Yaping; Ben Slimane, Ahmed; Alsunaidi, Mohammad; Ooi, Boon S

2012-07-01

326

Femtosecond laser fabricated all-optical fiber sensors with ultrahigh refractive index sensitivity: modeling and experiment  

NASA Astrophysics Data System (ADS)

All-optical fiber sensors based on ultracompact fiber inline Mach-Zehnder interferometer (MZI) are fabricated by side-ablating a U-shape microcavity in a single-mode optical fiber with the fiber core partially removed using femtosecond (fs) laser pulses, in which the two light paths are accordingly formed in the remaining D-type fiber core and the U-shape microcavity. Beam propagation method (BPM) analysis is utilized to illustrate the dependences of good transmission spectra on parameters including the ablation depth, ablation length and the refractive index of U-shape micocavity, which gives some guidelines to optimize parameters for fs laser micromachining and predicts RI (refractive index) sensitivities within given RI ranges. The modeling results of ultrahigh RI sensitivities for gases and solutions are -3243.75 ± 0.65nm/RIU (refractive index unit) and -10789.29 ± 18.91nm/RIU, respectively. In RI testing experiments, the sensor exhibits ultrahigh RI sensitivities of -3754.79 ± 44.24nm/RIU with refractive indices ranging from 1.0001143 to 1.0002187 by testing different mixture ratios of N2 and He gases, and -12162.01 ± 173.92nm/RIU with refractive indices ranging from 1.3330 to 1.33801 by testing different concentrations of sucrose solutions, which is essentially in agreement with the modeling results.

Jiang, Lan; Zhao, Longjiang; Wang, Sumei; Yang, Jinpeng; Xiao, Hai

2011-08-01

327

The Role of Multiferroics in the Negative Index of Refraction  

Microsoft Academic Search

We explore the possibility of realizing intrinsic far infrared negative index\\u000amaterials (NIM) in multiferroic crystals (crystals simultaneously possessing a\\u000aferroelectric and ferromagnetic phase) possessing electric and magnetic dipole\\u000aresonances with nearby resonance frequencies, or overlapping regions of\\u000anegative permittivity and permeability. We demonstrate the functionality of\\u000asuch a material using finite difference time domain simulations. In order to\\u000amotivate

David W. Ward; Eric Statz; Kevin J. Webb; Keith A. Nelson

2004-01-01

328

Microwave Focusing Using Negative Index of Refraction Materials  

Microsoft Academic Search

We present experimental results testing the theoretical prediction that a flat slab of negative index material can act as a perfect lens, focusing propagating waves. Our data gives two-dimensional profiles of the electromagnetic field transmitted from a 10 GHz point source in a 2D waveguide through composite wire and split-ring resonator rectangular prisms. Prior experiments show that these structures have

Jeffrey Brock; Andrew Houck; Isaac Chuang

2003-01-01

329

[Measurement of refractive index with a PM-LPG based Sagnac loop sensor].  

PubMed

By inscribing a long-period fiber grating (LPG) on a polarization-maintaining fiber (PMF), a fiber Sagnac loop sensor for simultaneous measurement of refractive index and temperature has been proposed and demonstrated. The LPG was fabricated on the PMF by using a CO2 laser, and then inserted into a fiber loop formed by using a normal single-mode fiber coupler. One of the transmission minimum of the Sagnac loop sensor was measured, whose wavelength varied with temperature and the intensity changed with refractive index. Temperature sensitivity of -0.654 nm x degrees C(-1) and refractive sensitivity of 49.9 dB x RIU(-1) have been achieved. The sensor system shows advantages of small size and low cost, and owns a good application prospect. PMID:21714225

Kang, Juan; Dong, Xin-Yong; Zhao, Chun-Liu; Zhang, Zai-Xuan; Jin, Shang-Zhong

2011-04-01

330

Direct index of refraction measurements at extreme-ultraviolet and soft-x-ray wavelengths  

SciTech Connect

Coherent radiation from undulator beamlines has been used to directly measure the real and imaginary parts of the index of refraction of several materials at both extreme-ultraviolet and soft-x-ray wavelengths. Using the XOR interferometer, we measure the refractive indices of silicon and ruthenium, essential materials for extreme-ultraviolet lithography. Both materials are tested at wavelength (13.4 nm) and across silicon's L2(99.8 eV) and L3(99.2 eV) absorption edges. We further extend this direct phase measurement method into the soft-x-ray region, where measurements of chromium and vanadium are performed around their L3absorption edges at 574.1 and 512.1 eV, respectively. These are the first direct measurements, to our knowledge, of the real part of the index of refraction made in the soft-x-ray region.

Rosfjord, Kristine; Chang Chang; Miyakawa, Ryan; Barth, Holly; Attwood, David

2006-03-10

331

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

Microsoft Academic Search

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

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

2003-01-01

332

Imaging and Waveguide Elements with Periodic or Negative Refractive Index Materials  

Microsoft Academic Search

Enthusiasm for negative refractive index materials has been aroused following the recent demonstration of a metamaterial implementation at microwave frequencies using printed con- ducting elements on a substrate (1) and the suggestion of application of this material class as a planar lens (2). Realizing such structures at terahertz and also optical frequencies would provide exciting signal processing and imaging opportunities.

D. W. Ward; E. Statz; M. Yang; K. A. Nelson; K. J. Webb

2003-01-01

333

Analysis of radar altitude estimation error using radio refractive index in Korea  

Microsoft Academic Search

This paper presents statistical analysis of radar altitude estimation error using the radio refractive index (RRI), N, in Korea. RRIs are derived from two stations, Sokcho and Baengnyeongdo, which are placed in the east and west of Korea on the same latitude, respectively. The seasonal mean values of the RRI are large in summer and small in winter, and regional

SungHoon Moon; Hyun Wook Moon; Jae Rim Oh; Young Joong Yoon; Jong Hyun Lee

2011-01-01

334

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

Microsoft Academic Search

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

P. B. Russell; Patrick Hamill

1984-01-01

335

Pressure Dependence of the Refractive Index of Amorphous Lone-Pair Semiconductors.  

National Technical Information Service (NTIS)

The pressure dependence of the refractive index (dn/dP) of several amorphous chalcogenide semiconductors is reported. dn/dP is positive for materials containing group-VI elements in twofold coordination (lone-pair semiconductors), whereas it is negative f...

M. Kastner

1972-01-01

336

Relation between the iodine number and refractive index of crude soybean oil  

Microsoft Academic Search

Conclusions  The iodine number of soybean oil can be determined by calculation from the measurement of refractive index with an accuracy\\u000a comparable to any chemical method, provided that the instrument used is sufficiently accurate, the measurements are carefully\\u000a made, and, for any given crop year, a correlation curve is established.

K. R. Majors; R. T. Milner

1939-01-01

337

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

338

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

Microsoft Academic Search

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

Adrian C. Selden

2011-01-01

339

Dispersion requirements of low-loss negative refractive index materials and their realisability  

Microsoft Academic Search

A necessary dispersion requirement is given for the effective relative permeability, ? r(?) and permittivity ?r(?) as a function of frequency for lossy homogeneous disper- sive materials and negative refractive index materials in particular, if they exist at some dimensional scale D. The requirements are valid both for isotropic and uniaxial materi- als, the latter defined by material properties that

A. J. Mackay

2009-01-01

340

Bio-Inspired Polymeric Gradient Refractive Index (GRIN) Human Eye Lens.  

National Technical Information Service (NTIS)

A synthetic polymeric lens was designed and fabricated based on a bio-inspired, 'Age=5' human eye lens design by utilizing a nanolayered polymer film-based technique. The internal refractive index distribution of an anterior and posterior GRIN lens were c...

A. Rosenberg M. Ponting R. Flynn R. S. Lepkowicz S. Ji

2012-01-01

341

Variation of the refractive index with temperature and the tuning rate for KDP isomorphs  

Microsoft Academic Search

The variation of refractive index with temperature is measured as a function of wavelength, temperature, and polarization for KDP and eight of its isomorphs. These data are used to predict the tuning rate for second harmonic generation as a function of temperature. The predicted tuning ratio compares well with the measured tuning rate. Reasonable agreement is found in most cases,

Norman P. Barnes; Donald J. Gettemy; Ratan S. Adhav

1982-01-01

342

Fibre Bragg grating photowriting in microstructured optical fibres for refractive index measurement  

Microsoft Academic Search

We report results relating to fibre Bragg grating photowriting in two kinds of Ge-doped core microstructured optical fibre devoted to sensing applications. A cross-comparison between theoretical and experimental modal field patterns is carried out. We present the first values of the spectral sensitivity of a Bragg grating in relation to the refractive index of calibrated oils inserted into the holes.

M. C. Phan Huy; G. Laffont; Y. Frignac; V. Dewynter-Marty; P. Ferdinand; P. Roy; J.-M. Blondy; D. Pagnoux; W. Blanc; B. Dussardier

2006-01-01

343

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

Microsoft Academic Search

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

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

2011-01-01

344

Effect of optical pumping on the refractive index and temperature in the core of active fibre  

NASA Astrophysics Data System (ADS)

This paper examines the refractive index change (RIC) induced in the core of Yb3+-doped active silica fibres by pulsed pumping. RIC kinetic measurements with a Mach — Zehnder interferometer make it possible to separately assess the contributions of the electronic and thermal mechanisms to the RIC and evaluate temperature nonuniformities in the fibre.

Gainov, V. V.; Ryabushkin, Oleg A.

2011-09-01

345

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

346

Analysis of mode locking and ultrashort laser pulses with a nonlinear refractive index  

Microsoft Academic Search

A new method for locking the longitudinal modes of a laser resonator and generating ultrashort pulses of light is described. The cavity modes are coupled together when a medium with a refractive index nonlinearity is placed in the cavity. A theoretical study is presented which analyzes the mode structure of a laser resonator containing a cell filled with an anisotropic

J.-P. Laussade; A. Yariv

1969-01-01

347

Computer Assisted Reduction of Experimental Data for the Index of Refraction of Water Systems  

Microsoft Academic Search

Computer programs were developed with polynomial fits to help analyze data for a series of experiments on the fundamental property of water (H 2 O) by monitoring the index of refraction. The computer played a major role in helping to compare data curves to accepted models for trends. The computer expedited the analysis of data, the preparation of graphs and

J. E. Gadhi; Mangal Dhoubhadel

348

Internal modes of solitons in media with a saturable nonlinearity of the refractive index  

Microsoft Academic Search

The theoretical analysis and calculation of internal modes (eigenmodes of small perturbations) of 1D, 2D, and 3D optical solitons in transparent media with a saturable nonlinearity of the refractive index are performed. Corrections that are nonlinear in the amplitude of perturbations and lead to the radiative damping of internal modes are found. The damping is shown to become weaker with

A. B. Vitenberg; P. I. Krepostnov; V. O. Popov; N. N. Rozanov

2002-01-01

349

Integrated optical inspection on surface geometry and refractive index distribution of a microlens array  

Microsoft Academic Search

This paper presents an effective technique based on optical interferometry to investigate the surface geometry\\/profile and refractive index distribution of a planar microlens array. The experimental setup consists of a sodium light source and a He–Ne laser source, which are incorporated into a microscopy system. The two light sources with different coherence lengths are utilized alternatively for surface geometry and

C. Quan; S. H. Wang; C. J. Tay; I. Reading; Z. P. Fang

2003-01-01

350

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

351

Experimental determination and numerical simulation of the properties of negative index of refraction materials  

Microsoft Academic Search

Negative index of refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized and simulated several of these structures operating in the 10 - 15 GHz range.

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

2003-01-01

352

Superconducting artificial materials with a negative permittivity, a negative permeability, or a negative index of refraction  

Microsoft Academic Search

Artificial materials are media made of inclusions such that the sizes and spacing of the inclusions is much smaller than the incident electromagnetic radiation. This allows a medium to act as an effective bulk medium to electromagnetic radiation. Artificial materials can be tailored to produce desired values of the permittivity, permeability, and index of refraction at specific frequencies. The applications

Michael Christopher Ricci

2007-01-01

353

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

Microsoft Academic Search

The capabilities of perovskite-like compounds with the effect of colossal magnetoresistance (CMR) and some other complex oxides to have a negative index of refraction (NIR) are considered. Physical properties of these compounds are also analyzed from the standpoint of designing tunable metamaterials on their base. Of particular interest are temperature and magnetic field driven first-order transformations in oxides with perovskite

E. L. Fertman; A. B. Beznosov

2011-01-01

354

Guided modes in channel waveguides with a negative index of refraction  

Microsoft Academic Search

The guided modes of a negative refractive index channel waveguide have been numerically investigated. It has been found that the modes exhibit a number of unusual properties that differ considerably from those of a conventional waveguide. In particular, it has been shown that these waveguides can exhibit low or negative group velocity as well as extraordinarily large group velocity dispersion.

A. C. Peacock; N. G. R. Broderick

2003-01-01

355

Negative index of refraction observed in a single layer of closed ring magnetic dipole resonators  

Microsoft Academic Search

We report the results of a spectroscopic study of a single layer of metallic single closed ring resonators on freestanding thin membrane at near normal and grazing angles of incidence. When the magnetic component of the light is perpendicular to the ring plane, we observe a negative index of refraction down to -1 around 150 THz, attributed to a strong

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

2007-01-01

356

Electromagnetic characteristics features of 1D periodic structures including layers with negative index of refraction  

Microsoft Academic Search

Propagation of plane electromagnetic waves in 1D periodic structures including the layers with both positive and negative refraction indexes is considered within the frame of the long wavelength approximation. The dependencies of the media effective characteristics (dielectric, magnetic, gyrotropic, electrooptic) on the corresponding properties and the relative thicknesses of the layers are investigated. These dependencies can have a resonant form

E. G. Starodubtsev

2005-01-01

357

A negative index of refraction metamaterial based on a wire array embedded in ferrite  

Microsoft Academic Search

A metamaterial exhibiting a negative index of refraction can be fabricated from an array of conducting wires cladded with non-magnetic dielectric and embedded in a magnetic host medium. The wires are responsible for the ? < 0 property and the magnetic medium for the mu < 0 property. A near exact calculation of the electromagnetic response of this metamaterial indicated

G. Dewar

2005-01-01

358

Negative index of refraction, spacetime folding and perfect imaging in transformation optics  

Microsoft Academic Search

Negative index of refraction has become an accepted part of transformation optics, which is encountered in transformations that change the orientation of the manifold. Based on this concept, various designs of perfect lenses have been proposed, which all rely on a folding of space or spacetime, where the maps from electromagnetic space to laboratory space are multi-valued. Recently, a new

Luzi Bergamin

2009-01-01

359

Full wave simulations of coated spheres with negative index of refraction at infrared frequencies  

Microsoft Academic Search

In this work we have successfully performed 3D full wave simulations of coated spheres. Retrieved effective material properties shows negative index of refraction similar to earlier analytical results except for some quantitative differences. The next step is to explore metamaterial property sensitivity to intrinsic material properties and fabrication tolerance.

T. A. Lam; Y. Kuga

2007-01-01

360

Minimization of losses in a structure having a negative index of refraction  

Microsoft Academic Search

A structure consisting of an array of wires cladded with a nonmagnetic dielectric and embedded in a ferrimagnetic host has been calculated to have a negative index of refraction. The structure has moderate losses over a bandwidth of a few GHz. The calculation takes into account the skin effect within the wires and is valid provided the wavelength of electromagnetic

Graeme Dewar

2005-01-01

361

Diffraction of electromagnetic waves by spherical bodies formed from a material with a negative refractive index  

Microsoft Academic Search

Scattering and absorption characteristics of linearly and circularly polarized electromagnetic waves that are diffracted by\\u000a spherical bodies formed from a material with a negative refractive index are studied. Unique properties of scattered fields\\u000a are discussed. Numerical results are presented.

B. A. Panchenko

2007-01-01

362

Estimation of the refractive index of plastic pigments by Wiener bounds  

NASA Astrophysics Data System (ADS)

Optical properties of spherical and nonabsorbing styrene- acryl copolymer pigment spheres with concentric spherical shells were studied by wavelength-dependent reflectance from the slurry. the data were analyzed using a light-scattering model and Wiener bounds. The object was to obtain estimates for the refractive index of a particle shell as a function of wavelength.

Jaaskelainen, A. J.; Peiponen, Kai-Erik; Raety, Jukka; Tapper, U.; Richard, O.; Kauppinen, E. I.; Lumme, K.

2000-11-01

363

Refinement of the imaginary part of the complex refractive index of liquid aluminum oxide  

Microsoft Academic Search

All the existing data in the literature dealing with the imaginary part of the complex refractive index ~ of liquid aluminum oxide have been obtained from the spectral brightness of the radiation of a system of molten particles moving in a hot stream of gases. Proceeding from the assumption of the equality of the temperatures of the particles and the

L. P. Bakhir; G. I. Levashenko; V. V. Tamanovich

1977-01-01

364

An Alternative Approach to the Tomographic Reconstruction of Smotth Refractive Index Distributions  

NASA Astrophysics Data System (ADS)

Continuous, mathematically smooth Phase Objects with radial symmetry are reconstructed from cross sections of their refractive index distribution by a novel method, consisting of a linear combination of Gaussian basis functions, whose technical details are discussed. As an application example, this approach is used to get a fast and accurate estimation of the temperature distribution of an actual soldering tip.

de la Rosa-Miranda, E.; Berriel-Valdos, L. R.; Gonzalez-Ramirez, E.; Alaniz-Lumbreras, D.; Saucedo-Anaya, T.; de la Rosa-Vargas, J. J.; Villa-Hernandez, J. J.; Torres-Argüelles, V.; Castano, V. M.

2013-06-01

365

Polymer Waveguide Label-Free Biosensors With Enhanced Sensitivity by Incorporating Low-Refractive-Index Polymers  

Microsoft Academic Search

Label-free biosensors consisting of polymeric waveguides with a Bragg reflection grating are demonstrated for the purpose of highly sensitive protein detectors. Due to the unique nanoimprinting and injection molding processes, polymer waveguide devices have the potential to provide cost-effective disposable biosensors as long as a robust compatible immunoassay process is developed. A fluorinated polymer material with the lowest refractive index,

Jun-Whee Kim; Kyung-Jo Kim; Jeong-Ah Yi; Min-Cheol Oh

2010-01-01

366

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

DOEpatents

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

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

1980-01-01

367

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

368

Effect of optical pumping on the refractive index and temperature in the core of active fibre  

SciTech Connect

This paper examines the refractive index change (RIC) induced in the core of Yb{sup 3+}-doped active silica fibres by pulsed pumping. RIC kinetic measurements with a Mach - Zehnder interferometer make it possible to separately assess the contributions of the electronic and thermal mechanisms to the RIC and evaluate temperature nonuniformities in the fibre.

Gainov, V V; Ryabushkin, Oleg A [V.A.Kotel'nikov Institute of Radio Engineering and Electronics, Fryazino Branch, Russian Academy of Sciences, Fryazino, Moscow Region (Russian Federation)

2011-09-30

369

Tailoring refractive index of aSi:H by TBP (C 4H 11P) doping  

Microsoft Academic Search

The refractive index, n, and extinction coefficient, k, of n-type TBP (tertiarybutylphosphine) doped a-Si:H films is reported. TBP is preferred over phosphine because of its lower toxicity and pyrophoricity. The films were deposited using glow discharge (plasma lab ?P) technique. The optical constants, n, k and absorption coefficient, ? are determined as functions of wavelength, ? and doping concentration. The

R. M Mehra; Inderbir; Jasmina; P. C Mathur

1997-01-01

370

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

Microsoft Academic Search

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

Dariusz Stramski

1999-01-01

371

Inline core-cladding intermodal interferometer based on nano-coated photonic crystal fiber for refractive-index sensing  

NASA Astrophysics Data System (ADS)

The paper presents a modification of the refractive-index (RI) response of a photonic crystal fiber (PCF) based intermodal interferometer using a thin plasma-deposited silicon nitride (SiNx) overlay with a high refractive index. We show that the film overlay can effectively change the distribution of the cladding modes and thus tune the RI sensitivity of the interferometer. Thanks to the nano-coating we were able to increase RI sensitivity eightfold in the range required for biosensors (nD~1.33). Due to the extreme hardness of SiNx films and their excellent adhesion to the fiber surface, we believe that after the deposition the device can still maintain its advantages, i.e. lack of degradation over time or with temperature.

Smietana, Mateusz; Brabant, Daniel; Bock, Wojtek J.; Mikulic, Predrag; Eftimov, Tinko

2011-05-01

372

Long Wave Short Wave Resonance in Nonlinear Negative Refractive Index Media  

Microsoft Academic Search

We show that long wave short wave resonance can be achieved in a second-order nonlinear negative refractive index medium when the short wave lies on the negative index branch. With the medium exhibiting a second-order nonlinear susceptibility, a number of nonlinear phenomena such as solitary waves, paired solitons, and periodic wave trains are possible or enhanced through the cascaded second-order

Aref Chowdhury; John A. Tataronis

2008-01-01

373

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 200-500nm. 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

2013-04-20

374

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

Microsoft Academic Search

The electric permittivity and magnetic permeability for the quark-gluon plasma (QGP) is calculated within the hard-thermal-loop (HTL) perturbation theory. The refractive indices in the magnetizable and non-magnetizable plasmas are calculated. In a magnetizable plasma, there is a frequency pole $\\\\omega_{mp}$ in the magnetic permeability and the refractive index. The refractive index becomes negative in the range $\\\\omega\\\\in[k,\\\\omega_{mp}]$, where $k$ is

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

2011-01-01

375

Tailoring the refractive index of aluminum doped zinc oxide thin films by co-doping with titanium  

NASA Astrophysics Data System (ADS)

The refractive index of transparent conductive oxides has a direct effect on the transmission of lights into thin film solar cells. Here we report the study of improving the refractive index of aluminum doped zinc oxide through titanium co-doping. The Al-Ti co-doped zinc oxide (ATZO) thin films with different Ti doping concentration were deposited on glass substrates by radio frequency magnetron sputtering with ATZO targets in an argon atmosphere. The structural, optical and electrical properties of the thin films were investigated using X-ray diffraction, ultraviolet-visible-near-infrared spectroscopy and hall measurements, respectively. The results showed that the as-deposited thin films were all textured along c-axis and perpendicular to the surface of substrate. The average transmittance in the visible region were more than 80% for all the ATZO thin films. The minimum resistivity of the obtained ATZO (1 wt% TiO2 doping) thin films were 2.6 × 10-3 ? cm and 1.4 × 10-3 ? cm before and after annealing in vacuum, respectively. The refractive index of the thin films (at ?0 = 550 nm) increased from 1.91 to 2.05 as the TiO2 content increased from 0 wt% to 3 wt%.

Wei, Tiefeng; Lan, Pinjun; Yang, Ye; Zhang, Xianpeng; Tan, Ruiqin; Li, Yong; Song, Weijie

2012-12-01

376

Universal amplitude combinations in critical mixtures of triethylamine and water from refractive index, density, turbidity, and specific heat experiments  

Microsoft Academic Search

We report new data on refractive index (n), density (&rgr;), and turbidity (?) in a mixture of triethylamine and water at critical concentration. These data have been obtained simultaneously for the same sample in order to make the comparison of amplitudes the most reliable. The high sensitivity (a few ppm) of the refractive index and density measurements enables the leading

G. Zalczer; D. Beysens

1990-01-01

377

Effects of the asymmetric refractive index change profile on the reflection spectra of multimode fiber Bragg gratings  

Microsoft Academic Search

In this paper, the effects of the asymmetric refractive index change profile on the reflection spectra of multimode fiber Bragg gratings (MMFBGs) are experimentally and theoretically investigated. Different guided modes in a multimode fiber (MMF) are coupled with each other and the sub-reflection peaks are generated if the refractive index change profile of the MMFBG is asymmetric in the cross

Hong-Gang Yu; Yong Wang; Chun Yang; Qing-Yang Xu; Xiao-Le Yang; Chang-Qing Xu

2005-01-01

378

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

NASA Astrophysics Data System (ADS)

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

Stavenga, D. G.

2006-08-01

379

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

NASA Astrophysics Data System (ADS)

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

Elek, Francis; Eleftheriades, George V.

2005-08-01

380

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

PubMed Central

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

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

2010-01-01

381

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

PubMed

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

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

1995-08-01

382

Tuning the refractive index of blended polymer films by RIR-MAPLE deposition  

NASA Astrophysics Data System (ADS)

Graded index polymer films enable novel optics using rigid or flexible substrates, such as waveguides or anti-reflection coatings. Previously, such films have been fabricated by nanoimprint lithography or the decomposition of a single component in polymer blends. Yet, it is desirable to have precise control over the polymer film composition in order to have the most flexibility in designing refractive index profiles. Resonant-infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a polymer thin film deposition technique that enables multi-layer structures on a wide variety of substrate materials, regardless of the solubilities of constituent polymers. In this work, the feasibility of tuning the refractive index of blended polymer films of polystyrene and poly(methyl methacrylate) deposited by RIR-MAPLE is demonstrated. Different polymer blend film compositions are deposited using RIR-MAPLE by varying the polymer target ratio. Transmission electron microscopy and atomic force microscopy are used to characterize the film morphology.

McCormick, Ryan D.; Cline, Eric D.; Chadha, Arvinder S.; Zhou, Weidong; Stiff-Roberts, Adrienne D.

2012-02-01

383

Beam shaping system based on polymer spherical gradient refractive index lenses  

NASA Astrophysics Data System (ADS)

A two-element laser beam shaping system based on spherical gradient refractive index (GRIN) lenses has been designed utilizing the optical design package CODE V®. The impetus for this design is the recent development of large diameter (~ 20 mm) layered polymer spherical GRIN lenses that can be fabricated with arbitrary index of refraction profiles between 1.490 and 1.573. A merit function is developed that includes the index range constraint, radius of curvature and thickness fabrication constraints, and a mapping function which maps the Gaussian irradiance profile into a flat-top profile. The designed system features high transmission efficiency, with nearly 100% of the energy transferred to the output beam and a variance of less than 3% in uniformity from the center to the edge of the beam. The adaptability of the lens making process allows for an additional degree of freedom in beam shaping.

Zahreddine, Ramzi N.; Lepkowicz, Richard S.; Bunch, Robert M.; Baer, Eric; Hiltner, Anne

2008-08-01

384

Low-loss single-layer metamaterial with negative index of refraction at visible wavelengths.  

PubMed

We present a structure exhibiting a negative index of refraction at visible or near infrared frequencies using a single metal layer. This contrasts with recently developed structures based on metal-dielectric-metal composites. The proposed metamaterial consists of periodically arranged thick stripes interacting with each other to give rise to a negative permeability. Improved designs that allow for a negative index for both polarizations are also presented. The structures are numerically analyzed and it is shown that the dimensions can be engineered to shift the negative index band within a region ranging from telecommunication wavelengths down to blue light. PMID:19547274

García-Meca, C; Ortuño, R; Salvador, R; Martínez, A; Martí, J

2007-07-23

385

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

386

Simultaneous measurement of refractive index and thickness of birefringent wave plates  

SciTech Connect

A nondestructive measurement system based on a position sensing detector (PSD) and a laser interferometer for determining the thickness and refractive indices of birefringent optical wave plates has been developed. Unlike previous methods presented in the literature, the proposed metrology system allows the refractive index and thickness properties of the optical plate to be measured simultaneously. The experimental results obtained for the e-light and o-light refractive indices of a commercially available birefringent optical wave plate with refractive indices of no=1.542972 and ne=1.552033 are found to be accurate to within 0.004132 and 0.000229, respectively. Furthermore, the experimentally derived value of the wave plate thickness deviates by no more than 0.9 {mu}m from the analytically derived value of 453.95 {mu}m. Overall, the experimental results confirm that the proposed metrology system provides a simple yet highly accurate means of obtaining simultaneous measurements of the refractive indices and thickness of birefringent optical wave plates.

Yeh, Y.-L

2008-04-01

387

Temperature-dependent refractive index of CaF2 and Infrasil 301  

NASA Astrophysics Data System (ADS)

In order to enable high quality lens designs using calcium fluoride (CaF2) and Heraeus Infrasil 301 (Infrasil) for cryogenic operating temperatures, we have measured the absolute refractive index of these two materials as a function of both wavelength and temperature using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center. 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 ?m, while for Infrasil, we cover temperatures ranging from 35 to 300 K and wavelengths from 0.4 to 3.6 ?m. For CaF2, we compare our index measurements to measurements of other investigators. For Infrasil, we compare our measurements to the material manufacturer's data at room temperature and to cryogenic measurements for fused silica from previous investigations including one of our own. Finally, we provide temperature-dependent Sellmeier coefficients based on our measured data to allow accurate interpolation of index to other wavelengths and temperatures.

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

2007-10-01

388

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Measurement of Refractive Index for High Reflectance Materials with Terahertz Time Domain Reflection Spectroscopy  

NASA Astrophysics Data System (ADS)

A method to measure the refractive index for high reflectance materials in the terahertz range with terahertz time domain reflection spectroscopy is proposed. In this method, the THz waveforms reflected by a silicon wafer and high reflectance sample are measured respectively. The refractive index of the silicon wafer, measured with the THz time domain transmission spectroscopy, is used as a reference in the THz time domain reflective spectroscopy. Therefore, the complex refractive index of the sample can be obtained by resorting to the known reflective index of the silicon and the Fresnel law. To improve the accuracy of the phase shift, the Kramers-Kronig transform is adopted. This method is also verified by the index of the silicon in THz reflection spectroscopy. The bulk metal plates have been taken as the sample, and the experimentally obtained metallic refractive indexes are compared with the simple Drude model.

Sun, Wen-Feng; Wang, Xin-Ke; Zhang, Yan

2009-11-01

389

Temperature-dependent refractive index of Cleartran ZnS to cryogenic temperatures  

NASA Astrophysics Data System (ADS)

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

Leviton, Douglas B.; Frey, Bradley J.

2013-09-01

390

Interferometric measurement of the resonant absorption and refractive index in rubidium gas  

NASA Astrophysics Data System (ADS)

We present a laboratory demonstration of the Kramers-Kronig relation between the resonant absorption and refractive index in rubidium gas. Our experiment uses a rubidium vapor cell in one arm of a simple Mach-Zehnder interferometer. As the laser frequency is scanned over an atomic resonance, the interferometer output is affected by variations of both the absorption and refractive index of the gas with frequency, all of which can be calculated in a straightforward manner. Changing the vapor density and interferometer phase produces a family of different output signals. The experiment was performed using a commercially available tunable diode laser system that was designed specifically for the undergraduate physics laboratory. As a teaching tool this experiment is reliable, fun, and instructive, while it also introduces the student to some sophisticated and fundamental physical concepts.

Libbrecht, K. G.; Libbrecht, M. W.

2006-12-01

391

Polynomial approximation method for tomographic reconstruction of three-dimensional refractive index fields with limited data  

NASA Astrophysics Data System (ADS)

We propose a polynomial approximation method (PAM) for reconstruction of three-dimensional refractive index fields by interferometric tomography using limited data. Based on the assumption that the fields to be reconstructed are usually smooth and can be decomposed into a finite order of (orthogonal) polynomials, a set of linear equations can be constructed using both the measured projection data and the Radon transform of the basis functions. By solving these equations, the least-squares solutions of expansion coefficients can be obtained and then substituted back to yield the desired fields. Numerical results have demonstrated that the proposed method is fast, robust to noise and can achieve satisfactory results for refractive index fields with limited projection views and large opaque objects.

Tian, Chao; Yang, Yongying; Zhuo, Yongmo; Ling, Tong; Li, Haoran

2012-03-01

392

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

PubMed

Using Jamin-Lebedeff interference microscopy, we measured the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive index values of the glass scales of the butterfly Graphium sarpedon are, at wavelengths 400, 500 and 600 nm, 1.572, 1.552 and 1.541, and those of the feather barbules of the white goose Anas anas domestica are 1.569, 1.556 and 1.548, respectively. The dispersion spectra of the chitin in the butterfly scales and the keratin in the bird barbules are well described by the Cauchy equation n(?) = A + B/?(2), with A = 1.517 and B = 8.80·10(3) nm(2) for the butterfly chitin and A = 1.532 and B = 5.89·10(3) nm(2) for the bird keratin. PMID:22109431

Leertouwer, Hein L; Wilts, Bodo D; Stavenga, Doekele G

2011-11-21

393

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

394

Positive phase evolution of waves propagating along a photonic crystal with negative index of refraction.  

PubMed

We analyze propagation of electromagnetic waves in a photonic crystal at frequencies at which it behaves as an effective medium with a negative index in terms of refraction at its interface with free space. We show that the phase evolution along the propagation direction is positive, despite the fact that the photonic crystal displays negative refraction following Snell's law, and explain it in terms of the Fourier components of the Bloch wave. Two distinct behaviors are found at frequencies far and close to the band edge of the negative-index photonic band. These findings contrast with the negative phase evolution that occurs in left-handed materials, so care has to be taken when applying the term left-handed to photonic crystals. PMID:19529372

Martínez, Alejandro; Martí, Javier

2006-10-16

395

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

396

Nonlinear refractive index of multicomponent glasses designed for fabrication of photonic crystal fibers  

NASA Astrophysics Data System (ADS)

The second order nonlinear refractive index n 2 of various multicomponent glasses was measured at the wavelength of 1240 nm close to the 1.3-?m fiber transmission window. With the refractive index covering the range from 1.45 to 2.3, a comparatively broad range of n 2 with values from 1.1×10-20 m2/W for boro-silicate based glass NC21 to 4.3×10-19 m2/W for lead-bismuth-gallate based glass PBG08 was measured using the Z-scan method. Considering the broad infrared transmission range of multicomponent glasses, these materials pose a great potential for future applications as photonic crystal fiber sources of infrared supercontinuum.

Lorenc, D.; Aranyosiova, M.; Buczynski, R.; Stepien, R.; Bugar, I.; Vincze, A.; Velic, D.

2008-11-01

397

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

NASA Astrophysics Data System (ADS)

In imaging-based studies of flow around solid objects, it is useful to have materials that are refractive-index-matched to the surrounding fluid. However, materials currently in use are usually rigid and matched to liquids that are either expensive or highly viscous. This does not allow for measurements at high Reynolds number, nor accurate modeling of flexible structures. This work explores the use of two hydrogels (agarose and polyacrylamide) as refractive-index-matched models in water. These hydrogels are inexpensive, can be cast into desired shapes, and have flexibility that can be tuned to match biological materials. The use of water as the fluid phase allows this method to be implemented immediately in many experimental facilities and permits investigation of high-Reynolds-number phenomena. We explain fabrication methods and present a summary of the physical and optical properties of both gels, and then show measurements demonstrating the use of hydrogel models in quantitative imaging.

Byron, Margaret L.; Variano, Evan A.

2013-02-01

398

An improved refractive index sensor based on genetic optimization of plasmon waveguide resonance.  

PubMed

Plasmon waveguide resonance (PWR) sensors are particularly useful for biosensing due to their unique ability to perform sensing with two different polarizations. In this paper we report a comprehensive performance comparison between the surface plasmon resonance (SPR) sensor and the PWR sensor in terms of the sensitivity and the refractive index resolution. Both sensors were optimized using a genetic algorithm to acquire their best performance for bulk sensing applications. The experimental results show that the PWR sensor has a refractive index resolution of 5 × 10-7 RIU which is 6 times smaller than that of the optimized SPR sensor. The TE polarization in the PWR sensor has a resolution of 1.4 × 10-6 RIU which is smaller than the SPR sensor. The polarization diversity in the PWR sensor is another advantage which can be used to improve the measurement reliability. PMID:24103959

Bahrami, Farshid; Maisonneuve, Mathieu; Meunier, Michel; Aitchison, J Stewart; Mojahedi, Mo

2013-09-01

399

Effects of thickness and external refractive index in coated tilted fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

In this work, an experimental analysis on the spectral effects induced by depositing a uniform high refractive index (HRI) thin coating on weakly tilted fiber Bragg gratings (TFBGs) is carried out. First, two weakly TFBGs presenting different tilt angles were fabricated. Successively, by using dip-coating technique, two different coating thicknesses were deposited on each of them. The transmission spectra of the obtained structures were collected as the surrounding refractive index (SRI) changed in the range 1÷1.47. The coated gratings present some differences in their spectral evolution, that can be opportunely exploited. The coated configuration could improve some aspects of previous demodulation techniques exploited in the case of bare TFBGs. Moreover, an important effect of HRI coatings is to enhance the SRI sensitivity of the spectral position of the dips corresponding to cladding modes coupling, leading to a different interrogation method for sensing applications.

Paladino, D.; Pilla, P.; Cutolo, A.; Campopiano, S.; Giordano, M.; Cusano, A.; Caucheteur, C.; Mégret, P.

2007-07-01

400

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

401

Modification of refractive index in amorphous As-Se films induced by composition and illumination  

NASA Astrophysics Data System (ADS)

Photostructural transformations in amorphous films of chalcogenide glasses (ChG) under light irradiation present scientific and practical interests. From scientific point of view, because the composition of ChG determine the kind of structural units and the mean coordination number, in the present work the amorphous films of the chalcogenide systems As100-xSex (x=40÷98) and As40Se60:Sny (y=0÷5.0 at.% Sn) were studied. The changes of the refractive index under light irradiation and heat treatment are calculated from the transmission spectra. The more sensitive to light irradiation are the amorphous films of As60Se40 and As50Se50, which exhibit big modifications of the refractive index ((?n/n)=0.394).

Iovu, M. S.; Harea, D. V.; Colomeico, E. P.; Iovu, M. A.; Ciorba, V. G.

2007-08-01

402

Switching characteristic of Bragg micro-cavity constructing with positive/negative refractive index materials  

NASA Astrophysics Data System (ADS)

In 1968, physicist V.G. Beselago pointed out that there always exists negative refractive index in materials when their electric constant and magnetic permeability ? are both negative, and therefore the propagation properties of the EM wave in such materials behave distinctively from those in media with positive refractive index (RI). In this paper, we construct two types of one-dimensional photonic crystals made up with positive and negative RI materials and investigate their nonlinear optical properties. One type of photonic crystals consists of materials with both negative linear and positive third-order nonlinear RIs, the other are mainly made up with a Bragg micro-cavity constructed with both linear positive and negative RIs which contains Kerr media. We show that both types of photonic crystals exhibit bistable switching characteristics. Moreover, as compared with the crystals involved pure positive RI, our photonic crystals possess even lower threshold valve in optical switching.

Deng, K. F.

2005-12-01

403

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

404

Liquid densities, heat capacities, refractive index and excess quantities for {protic ionic liquids + water} binary system  

Microsoft Academic Search

Densities, ?, of aqueous solutions of the room temperature protic ionic liquid (PIL), pyrrolidinium nitrate are determined at the atmospheric pressure over the temperature range from (283.15 to 323.15)K and within the whole composition range. The molar isobaric heat capacities, Cp, and refractive index, nD, of {PIL+water} binary system are measured at 298.15K. The excess molar volumes VE, excess molar

Mérièm Anouti; Magaly Caillon-Caravanier; Yosra Dridi; Johan Jacquemin; Christopher Hardacre; Daniel Lemordant

2009-01-01

405

Fabrication of high refractive index-modulation structures in fused silica by femtosecond laser pulses  

Microsoft Academic Search

We present the microfabrication of high refractive index-modulated structures written by line scan inside bulk of fused silica with a femtosecond laser at wavelength of 810 nm. The femtosecond laser beam, with duration between 130 fs and 500 fs at a repetition rate of 1 kHz, was focused through a microscope objective with numerical aperture (NA) of 0.10 or 0.25

Hengchang Guo; Yan Li; Xi Wang; Ying Fang; Hongbing Jiang; Hong Yang; Qihuang Gong

2005-01-01

406

A Compact Integrated Planar-Waveguide Refractive-Index Sensor Based on a Corrugated Metal Grating  

Microsoft Academic Search

In this paper, a theoretical model of a new planar integrated surface plasmon-polariton (SPP)-excitation-based refractive-index sensor is presented and comprehensively investigated. The main principle of operation of this device is based on energy transfer by means of a corrugated metal grating between a p-polarized guided mode propagating in a waveguide layer and the SPP propagating in the opposite direction in

Galina Nemova; Raman Kashyap

2007-01-01

407

Detailed Refractive Index Measurement near Melting in a Plastic Crystal: Succinonitrile  

Microsoft Academic Search

An interferometric measurement of the temperature derivative of the refractive index in succinonitrile is reported over a temperature range (30[ddot]C ? 66[ddot]C) that includes melting. In pure material the behavior is clearly that of a first-order transition both on heating and on cooling. In impure material premelting effects are seen below fusion. In all cases appreciable supercooling can be observed.

R. M. Macfarlane; E. Courtens; T. Bischofberger

1976-01-01

408

Low-frequency index of refraction for a two-dimensional metallodielectric photonic crystal  

Microsoft Academic Search

We calculate analytically the effective index of refraction neff of a periodic arrangement of nonmagnetic metallic cylinders in the low-frequency limit. At omega-->0 the dielectric constant of the cylinders is singular, gammam(omega)≈-(omegap\\/omega)2 , allowing propagation in the plane of periodicity of a mode with the magnetic field parallel to the cylinders ( H polarization). The in-plane electric field induces eddy

A. A. Krokhin; E. Reyes; L. Gumen

2007-01-01

409

Sol-gel deposition of nanostructured low refractive index materials on solar collector glazing  

Microsoft Academic Search

Nanoporous SiO2 and nanocomposite MgF2:SiO2 coatings have been deposited by sol-gel dip- coating in a particle-free atmosphere. The refractive index of the prepared nanostructured thin films is determined from spectrophotometric data. In both cases, significantly lower values than for compact SiO2 have been achieved. Highly transparent samples have been produced in a single dip-coating step followed by simple thermal annealing

A. Schüler; D. Dutta; H. Chelawat; E. De Chambrier; C. Roecker; J.-L. Scartezzini

410

Internal modes of solitons in media with a saturable nonlinearity of the refractive index  

Microsoft Academic Search

The theoretical analysis and calculation of internal modes (eigenmodes of small perturbations) of 1D, 2D, and 3D optical solitons\\u000a in transparent media with a saturable nonlinearity of the refractive index are performed. Corrections that are nonlinear in\\u000a the amplitude of perturbations and lead to the radiative damping of internal modes are found. The damping is shown to become\\u000a weaker with

A. B. Vitenberg; P. I. Krepostnov; V. O. Popov; N. N. Rozanov

2002-01-01

411

Spatial Harmonics and Homogenization of Negative-Refractive-Index Transmission-Line Structures  

Microsoft Academic Search

In this paper, we discuss negative-refractive-index transmission-line (NRI-TL) metamaterial structures with respect to spatial harmonics. The power in the fundamental spatial harmonic is shown to yield a measure that relates to the homogeneity of the metamaterial. It is shown that NRI-TL metamaterials yield highly homogeneous field distributions if both the unit cell is short compared to the guided wavelength, and

Michael Zedler; George V. Eleftheriades

2010-01-01

412

Volumetric layered transmission-line metamaterial exhibiting a negative refractive index  

Microsoft Academic Search

We examine a new class of volumetric metamaterials based on two-dimensional (2D) transmission-line layers that exhibit a negative refractive index (NRI). The dispersion characteristics of a single 2D layer are revealed through a periodic analysis, and the effective-medium response of the volumetric layered topology is predicted by an intuitive equivalent circuit model. Dispersion and transmission characteristics are also obtained for

Ashwin K. Iyer; George V. Eleftheriades

2006-01-01

413

Negative index of refraction in metallic metamaterial comprising split-ring resonators  

Microsoft Academic Search

We numerically investigate the negative index of refraction in a metamaterial composed of metallic split-ring resonators, which exhibits simultaneously negative permittivity and permeability without resorting to additional metallic wires. It is confirmed that, in the left-handed band, negative permittivity is generated in analogy to the cut-wire metamaterial and negative permeability comes from the antisymmetric resonant mode, which occurs at a

Zheng-Gao Dong; Shuang-Ying Lei; Ming-Xiang Xu; Hui Liu; Tao Li; Fu-Ming Wang; Shi-Ning Zhu

2008-01-01

414

Coated nonmagnetic spheres with a negative index of refraction at infrared frequencies  

Microsoft Academic Search

A three-dimensional lattice of micron-scale coated spheres is shown to have an isotropic negative index of refraction at infrared frequencies. The materials used are entirely non-magnetic. The Mie scattering theory of the constituent spheres is used in the effective medium theory. The physical mechanisms and procedures are presented in the design of a negative effective permeability with solid polaritonic spheres,

Mark S. Wheeler; J. Stewart Aitchison; Mohammad Mojahedi

2006-01-01

415

An approach to achieving a negative index of refraction using coincident resonances  

Microsoft Academic Search

A novel method of achieving a negative index of refraction in the far-infrared region using intrinsic material properties is proposed. SrTiO3 has a dielectric resonance at ?100 cm?1 that can be lowered by lowering the temperature or with Ba doping. NiO has an antiferromagnetic resonance at ?35 cm?1 that can be raised with an applied field or with Co doping.

S D Kirby; M Lee; R B van Dover

2007-01-01

416

Double Negative Index of Refraction Observed in a Single Layer of Closed Ring Resonators  

Microsoft Academic Search

We report the results of a spectroscopic study of a single layer of nanoscale metallic single closed ring resonators on a free- standing thin membrane at near-normal and grazing angles of incidence^[1]. When the magnetic component of the light is perpendicular to the ring plane, we observe a so-called ``double'' negative index of refraction at near-infrared frequencies attributed to a

Zhao Hao; Michael Martin; Bruce Harteneck; Stefano Cabrini; Erik Anderson

2008-01-01

417

Propagation of a localized wavepacket in a metamaterial with a negative index of refraction  

Microsoft Academic Search

Propagation properties of electromagnetic waves in a medium with a negative index of refraction are investigated. A model\\u000a of a physical signal that combines simultaneously qualities of both a spatially-localized beam and a wavepacket was used as\\u000a the incident wave. Such a choice was necessary because of the strong frequency dispersion of metamaterials in the spectral\\u000a region with a negative

V. V. Grigor’ev; V. V. Kabanov

2008-01-01

418

Isotropic optical negative index of refraction metamaterials composed of randomly arranged nanoparticles  

Microsoft Academic Search

We report a strategy for achieving fully isotropic negative refraction index in a homogenized composite medium (HCM) conceptualized using both Maxwell-Garnett's and Lewin's effective medium formulations. The HCM consists of two isotropic dielectric-magnetic media (DMM): one DMM (randomly distributed small gold nanoparticles in free space) provides only negative permittivity, and another DMM (spherical SiC particles) provides only negative permeability via

Adil-Gerai Kussow; Alkim Akyurtlu

2007-01-01

419

Numerical simulations of negative-index refraction in a lamellar composite with alternating single negative layers  

Microsoft Academic Search

Negative-index refraction is demonstrated in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the renowned left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of

Zheng-Gao Dong; Shi-Ning Zhu; Hui Liu

2006-01-01

420

An approach to achieving a negative index of refraction using coincident resonances  

Microsoft Academic Search

A novel method of achieving a negative index of refraction in the far-infrared region using intrinsic material properties is proposed. SrTiO3 has a dielectric resonance at ~100 cm-1 that can be lowered by lowering the temperature or with Ba doping. NiO has an antiferromagnetic resonance at ~35 cm-1 that can be raised with an applied field or with Co doping.

S. D. Kirby; M. Lee; R. B. van Dover

2007-01-01

421

Low-Loss Multilayered Metamaterial Exhibiting a Negative Index of Refraction at Visible Wavelengths  

Microsoft Academic Search

We experimentally demonstrate a low-loss multilayered metamaterial exhibiting a double-negative refractive index in the visible spectral range. To this end, we exploit a second-order magnetic resonance of the so-called fishnet structure. The low-loss nature of the employed magnetic resonance, together with the effect of the interacting adjacent layers, results in a figure of merit as high as 3.34. A wide

Carlos García-Meca; Juan Hurtado; Javier Martí; Alejandro Martínez; Wayne Dickson; Anatoly V. Zayats

2011-01-01

422

Compact Negative-Refractive-Index Transmission-Line (NRI-TL) coupler, filter and diplexer  

Microsoft Academic Search

This work demonstrates how certain properties of Negative-Refractive-Index Transmission-Line (NRI-TL) metamaterials can be utilized to miniaturize conventional microwave devices used to feed antennas. Specifically in NRI-TLs small values of the loading elements lead to large phase shifts per-unit-length, thus facilitating miniaturization. Using this principle, a compact NRI-TL branch-line coupler (85% area reduction) is presented. Moreover, a filter is presented with

Rubaiyat Islam; George V. Eleftheriades

2007-01-01

423

Estimation of nonlinear refractive index in various silica-based glasses for optical fibers  

NASA Astrophysics Data System (ADS)

The dependence of the nonlinear refractive index n2 on glass compositions for optical fibers is clarified. The relation between n2 and germanium- or fluorine-doped SiO2 is calculated on the basis of the measurement of n 2 at 1.55 mu m with the improved cross-phase-modulation method, taking into account the radial distribution of the optical power in the fibers.

Kato, T.; Suetsugu, Y.; Nishimura, M.

1995-11-01

424

Nonlinear optical effects in media with a positive-negative refractive index  

Microsoft Academic Search

The nonlinear phenomena in media whose linear refractive index changes its magnitude and sign with a change in the wave carrier\\u000a frequency or spatial coordinate, are considered. The results of theoretical investigations of the generation of harmonics\\u000a in a homogeneous medium, optical bistability, and propagation of stationary solitary waves in a two-channel waveguide are\\u000a discussed.

A. I. Maimistov; I. R. Gabitov

2008-01-01

425

DESIGN OF WIRE-WRAPPED ROD BUNDLE MATCHED INDEX-OF-REFRACTION EXPERIMENTS  

Microsoft Academic Search

Experiments will be conducted in the Idaho National Laboratory (INL) Matched Index-of-Refraction (MIR) Flow Facility [1] to characterize the three-dimensional velocity and turbulence fields in a wire-wrapped rod bundle typically employed in liquid-metal cooled fast reactors and to provide benchmark data for computer code validation. Sodium cooled fast reactors are under consideration for use in the U.S. Department of Energy

Hugh McIlroy; Hongbin Zhang; Kurt D. Hamman

2008-01-01

426

Volumetric properties, viscosity and refractive index of the protic ionic liquid, pyrrolidinium octanoate, in molecular solvents  

Microsoft Academic Search

Densities (?) and viscosities (?) of binary mixtures containing the Protic Ionic Liquid (PIL), pyrrolidinium octanoate with five molecular solvents: water, methanol, ethanol, n-butanol, and acetonitrile are determined at the atmospheric pressure as a function of the temperature and within the whole composition range. The refractive index of all mixtures (nD) is measured at 298.15K. The excess molar volumes VE

Mérièm Anouti; Annie Vigeant; Johan Jacquemin; Catherine Brigouleix; Daniel Lemordant

2010-01-01

427

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

Microsoft Academic Search

The planar waveguides have been fabricated in z-cut beta barium metaborate crystals by 2.8 MeV Si+ ion implantation with doses of 1 × 1015 and 3 × 1015 ions\\/cm2 at room temperature. The waveguides were characterized by the prism-coupling method. The refractive index profiles were reconstructed using reflectivity calculation method. It is found that relatively large positive changes of extraordinary

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

2004-01-01

428

Measurement of relief depth and refractive index variation of phase hologram  

NASA Astrophysics Data System (ADS)

The paper proposes a method of measuring relief depth and refractive index variation which distribute in a holographic phase grating. By this method an interference microscope and a microcomputer with a CCD camera are used in measuring and can obtain highly precise data. In the paper, an example of measuring DCG grating is presented, the errors of these data are analyzed and optimum conditions which make a measurement system keep its highest accuracy are given.

Zhang, Xiao-Chun; Guo, Yong-Kang; Guo, Lu-Rong

1993-03-01

429

Interferometric determination of electron density in a high pressure hydrogen arc: I - Calculation of refraction index  

Microsoft Academic Search

The refraction index of a hydrogen plasma in LTE was calculated as a function of the wavelength of observation, temperature and pressure, taking into account bound-bound and bound-free transitions of the neutral atom. According to our calculations, the influence of excited states at higher temperatures is smaller than indicated by Baum and co-workers in 1975 for argon. Using the calculations

R. Radtke; K. Guenther; R. Ulbricht

1980-01-01

430

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

Microsoft Academic Search

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

S. Wozniak; R. Zawodny

1981-01-01

431

Effects of the absorption coefficient on the refractive index of germanium in a fiber optic-semiconductor temperature sensor  

NASA Astrophysics Data System (ADS)

This paper introduces a theoretical model which reveals the relation between the absorption and the refractive index of germanium within absorption region, which is crucial to a new fiber optic-semiconductor film temperature sensor developed lately in our lab. The new designed sensor is based on the effect of the temperature dependence of the refractive index of semiconductor. Many efforts on the effect of the temperature-dependent refractive index of semiconductor are reported in transparent region mostly by empirical model such as Sellmeier model[1]. We analyze the temperature dependence of the refractive index of semiconductor near the absorption edge other than in the transparent region. From the Kramers-Kronig relations, the refractive index is an integral of the absorption coefficient over the whole energy spectrum.Taking advantage of the model that explained the contribution of the integral cloesd to the absorption edge to the refractive index by Frank Stern [2] we are able to calculate the variation of the refractive index due to the thermal shift of absorption edge. The contribution of the temperature-dependent absorption coefficient to the refractive index is enhanced dramatically at the absorption edge of semiconductor, where the temperature dependence of the energy gap Eg can be used to get the absorption edge shift with Yu-Brook's model[3]. While the contribution of the absorption shift far away from the absorption edge to ?n is negligible comparing to that near the edge according to Frank Stern[2]. Further demonstration experiments will be carried out to support our theory, in which refractive indexes of germanium are measured at specific wavelengths of 1310nm, 1550nm and 2000nm. Since the direct absorption edge of germanium is at about 0.82eV, corresponding to the wavelength of 1550nm, we estimate that the thermo-optic coefficient dn/dT of germanium at 1550nm would be larger than that at 1310nm and 2000nm.

Peng, Liu; Min, Li; Zhong, Pan

2011-11-01

432

All organic DFB laser enhanced by intermediate high refractive index polymer layer  

NASA Astrophysics Data System (ADS)

Performances of a distributed feedback (DFB) organic dye laser were enhanced by introducing an intermediate high refractive index layer of poly(N-vinylcarbazole) (PVCz) laminated between a glass substrate and a laser dye doped active polymer layer. The active layer is consisted of rhodamine 6G and cellulose acetate (CA). Introduction of an intermediate layer allows a single mode lasing. Slope efficiencies of 2.2 and 4.7% and thresholds of 0.3 and 0.14 mJ/cm2/pulse were measured for the waveguides with 1.7 and 3.4 ?m active layers, respectively. Furthermore, permanent relief grating on an intermediate layer gave rise to the reduction of the threshold. With increasing in amplitude of the relief grating from 20 to 45 nm, lasing threshold was reduced from 0.18 to 0.04 mJ/cm2/pulse for the waveguide with 1.7 ?m active layer. The slope efficiency increased from 3.5 to 4.2%.

Tsutsumi, N.; Shinobu, M.

2011-12-01

433

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

SciTech Connect

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

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

1993-06-01

434

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

435

A method for measuring the complex refractive index of a turbid medium  

NASA Astrophysics Data System (ADS)

Based on the heterodyne interferometry and Fresnel equations, an alternative method for measuring the complex refractive index of a turbid medium. A light beam is incident on the boundary between a right-angle prism and a turbid medium. The phase difference between s- and p- polarizations of the reflected light occurs. The phase difference depends on then incident angle and the complex refractive index of a turbid medium; their relation can be derived from Fresnel equations. The phase difference can be measured accurately with the heterodyne interferometry. Because there are two unknown parameters to be estimated, at least the phase differences under two different conditions should be measured. Then, these measured data are substituted into the derived relation, and a set simultaneous equation is obtained. If the simultaneous equation is solved, the complex refractive index can be estimated. Because the reflected light from the boundary is measured, the scattering noises coming from the turbidity of the tested medium can be greatly reduced. In addition, this method has some merits such as simple optical setup, high sensitivity, high stability, and suitability for a little amount of the tested medium in its native state (without dilution).

Jian, Zhi-Cheng; Lin, Jiun-You; Hsieh, Po-Jen; Chen, Huei-Wen; Su, Der-Chin

2005-06-01

436

Experimental determination and numerical simulation of the properties of negative index of refraction materials.  

PubMed

Negative index of refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized and simulated several of these structures operating in the 10 - 15 GHz range. Our simulations using Maxwell's Equations solvers have included wire arrays, ring arrays and assemblies of unit cells comprised of rings and wires. We find good agreement between the numerical simulations and experimental measurements of the scattering parameters and index of refraction. The procedure was to first model ring and wire structures on the unit cell level to obtain scattering parameters from which effective å, ì and n were retrieved. Next an assembled array of unit cells forming a 12 degrees wedge was used for the Snell's Law determination of the negative index of refraction. For the structure examined the computed value of n is within 20% of the one experimentally measured in the Snell's Law experiment from 13.6 to 14.8 GHz. PMID:19461780

Greegor, R; Parazzoli, C; Li, K; Koltenbah, B; Tanielian, M

2003-04-01

437

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

PubMed

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. PMID:23922125

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

2013-08-01

438

Engineering properties of high-refractive index optical gels for photonic device applications  

NASA Astrophysics Data System (ADS)

We have investigated a new class of high refractive index, non-yellowing, viscoelastic optical gels. Refractive indices for these materials can be adjusted from that needed to match fused silica to above nD equals 1.6 to match the higher index engineering glasses, plastics, and semiconductors. These materials are designed for permanent optically clear encapsulation in devices where severe mechanical shock or differential thermal expansion, such as occurs during PCB soldering operations, may render conventional high strength optical epoxies unusable. These low shear stress gels can also be customized to exhibit a wide range of rheological 'stiffness'. We have demonstrated quasi-fluid versions with apparent viscosities of 500,000 cP to hard-rubber-like consistencies registering on the high end of the Shore 00 durometer scale. In this paper, we present measurements of engineering properties on both elastometer-like curing optical gels, and thixotropic non- curing optical gels for: a) optical properties from near UV to near IR: refractive index over temperature, dispersion, and optical absorption; b) rheological properties: viscosity vs. shear rate, Shore hardness and cone penetration. Validation of ultra-low volatility and high temperature thermo oxidative stability required for long-lived photonic devices is discussed. Use of gel technology in fiber splices and photonic devices is described.

Stone, David S.; Connor, Samantha R.

2000-04-01

439

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

440

The Effect of Change in Refractive Index on Wave Propagation Through (FeS2) Thin Film  

NASA Astrophysics Data System (ADS)

Wave propagation in inhomogenous feS2 film was studied and the influence of the change in the refractive index introduced as a perturbation on EM wave propagating through the film. The solution of the scalar wave equation was obtained first using series expansion solution method of Green`s function with appropriate boundary condition. The result was written as sources of two fields where the second term was considered to be correction term due to the perturbation or small change in the refractive index. The influence of large step in refractive index and surface impedance offered by the film medium to the propagating wave was discussed.

Ugwu, E. I.; Uduh, P. C.; Agbo, G. A.

441

Determination of the refractive index and size distribution of aerosol from dual-scattering-angle optical particle counter measurements  

NASA Astrophysics Data System (ADS)

A method is presented for inferring both the refractive index and the size distribution of aerosol from observations of a dual-scattering-angle optical particle counter (OPC). An existing prototype of an OPC with 60° and 90° dual-scattering angles was used for the experiments. Based on the high sensitivity of the OPC response to the refractive index of particulates, two families of size distribution curves may be calculated. The solution of the refractive index corresponds to the superposition of the two size distributions. This method was applied to the simulation and to the field measurements conducted in Beijing and Hefei, and the results of both are presented.

Hu, Huanling; Li, Xuebin; Zhang, Yinchao; Li, Tao

2006-06-01

442

Re-Examination of PMC Scattering in the Middle Ultraviolet: Is the Ice Index of Refraction Wrong?  

NASA Astrophysics Data System (ADS)

Recent analysis of MSX-UVISI spectrographic data indicates that a "hump" exists in the middle ultraviolet spectral albedo of polar mesospheric clouds and that such a feature cannot be explained in the context of a mono-modal lognormal distribution of Mie scatterers. However, neither Mie scattering nor a mono-modal distribution need be abandoned if the index of refraction of the particles differs somewhat from the currently-accepted index of refraction of ice in the wavelength region of interest. Indeed, the index of refraction of ice in the middle ultraviolet is poorly known and essentially un-measured, so inferences from PMC measurements can possibly correct the index in this wavelength regime. The index of refraction of ice has important ramifications outside the field of PMC scattering because it has implications for the structure of ice at cold temperatures (~100K) and can be used in the exploration of icy moons.

Carbary, J. F.

2005-12-01

443

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

444

Design of a novel negative refractive index material based on numerical simulation  

NASA Astrophysics Data System (ADS)

This paper presents a novel metamaterial constructed with wires, spheres and hollow slabs (WSHS), which simultaneously exhibits negative permittivity and permeability. An electromagnetic wave simulation is performed based on the proposed metamaterial and shows that a negative refractive index is achieved for this metamaterial. Adjusting the lattice constant of the unit cell is an easy way to manipulate the frequency of negative index of this structure. A left-hand material prism is designed composed of metamaterial unit cells and the simulation on the proposed prism proves the left-hand behavior of the designed metamaterial.

Rizwan, Muhammad; Dou, Yan-Kun; Jin, Hai-Bo; Hou, Zhi-Ling; Kong, Ling-Bao; Li, Jing-Bo; Butt, Faheem K.; Rehman, Fida

2013-07-01

445

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

PubMed

We experimentally demonstrate a low-loss multilayered metamaterial exhibiting a double-negative refractive index in the visible spectral range. To this end, we exploit a second-order magnetic resonance of the so-called fishnet structure. The low-loss nature of the employed magnetic resonance, together with the effect of the interacting adjacent layers, results in a figure of merit as high as 3.34. A wide spectral range of negative index is achieved, covering the wavelength region between 620 and 806 nm with only two different designs. PMID:21405495

García-Meca, Carlos; Hurtado, Juan; Martí, Javier; Martínez, Alejandro; Dickson, Wayne; Zayats, Anatoly V

2011-02-11

446

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

Microsoft Academic Search

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

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

2009-01-01

447

Viscosity, refractive index, and surface tension of multicomponent systems: Mathematical representation and estimation from data for binary systems  

Microsoft Academic Search

An equation previously developed for estimation of the excess thermodynamic properties of multicomponent systems from binary mixing data has been applied to other physical properties through extrathermodynamic properties such as the excess Gibbs free energy of activation for viscous flow, molar refractivity, and exess surface free energy. This equation provides reasonably accurate predictions for viscosity, refractive index and surface tension

William E. Acree; Gary L. Bertrand

1983-01-01

448

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

449

Refractive index, sound velocity and thickness of thin transparent films from multiple angles picosecond ultrasonics  

SciTech Connect

We present a method for refractive indices and longitudinal sound velocity measurements from picosecond ultrasonic experiments made at different probe incidence angles. For transparent or semitransparent materials such as dielectrics or semiconductors, picosecond ultrasonic experiments can lead to oscillations in the reflectivity curves whose frequency depends on the refractive indices, the sound velocity and the experiments angle. From these data we establish a simple method for the calculation of the refractive indices and verify it on a GaAs sample. We show on fluorinated silica glass and aluminum nitride practical applications of this method on thin films. From two experiments we measure the refraction index and the sound velocity of these materials, with no assumption on the materials properties or on the sample layers' thicknesses. Here the materials are buried under a thin aluminum film. It illustrates the fact that the method can be applied to multilayers. From the same experiments we then derive the thickness of the layers. It shows that this method can render picosecond ultrasonic experiments independent from other characterization means.

Cote, R.; Devos, A. [Institut d'Electronique, de Microelectronique et de Nanotechnologie, Unite Mixte de Recherche CNRS 8520, Avenue Poincare BP 69, F-59652 Villeneuve d'Ascq CEDEX (France)

2005-05-15

450

Modeling refractive index change in writing long-period fiber gratings using mid-infrared laser radiation  

NASA Astrophysics Data System (ADS)

The research on the use of fiber sensors based on long-period fiber gratings inscribed by CO2 laser mid-infrared radiation has increased in the last years. In this paper, a set of analytical expressions are used to model the interaction between laser radiation and an optical fiber and to determine the resulting refractive index change. Thermal and residual stress analysis is exemplified for a standard single mode fiber, demonstrating the capability of these models to point out the necessary parameters to achieve proper optical fiber devices based on long period fiber gratings. Experimental results are also presented.

Coelho, João M. P.; Nespereira, Marta C.; Abreu, Manuel; Rebordão, José M.

2013-03-01

451

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

452

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

PubMed

A zero-refractive-index metamaterial is one in which waves do not experience any spatial phase change, and such a peculiar material has many interesting wave-manipulating properties. These materials can in principle be realized using man-made composites comprising metallic resonators or chiral inclusions, but metallic components have losses that compromise functionality at high frequencies. It would be highly desirable if we could achieve a zero refractive index using dielectrics alone. Here, we show that by employing accidental degeneracy, dielectric photonic crystals can be designed and fabricated that exhibit Dirac cone dispersion at the centre of the Brillouin zone at a finite frequency. In addition to many interesting properties intrinsic to a Dirac cone dispersion, we can use effective medium theory to relate the photonic crystal to a material with effectively zero permittivity and permeability. We then numerically and experimentally demonstrate in the microwave regime that such dielectric photonic crystals with reasonable dielectric constants manipulate waves as if they had near-zero refractive indices at and near the Dirac point frequency. PMID:21623377

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

2011-05-29

453

Refractive-index measurement of gradient-index microlenses by diffraction tomography.  

PubMed

Diffraction tomography is applied to reconstruction of the gradient-index distribution of planar gradient-index microlenses, fabricated by thermal ion exchange. Measurements of the single-phase projections are performed by phase-shifting interferometry For reconstruction, the Rytov approximation for smooth inhomogeneities is applied. Results are compared with measurement results from other methods and simulation results. PMID:21085345

Singer, W; Dobler, B; Schreiber, H; Brenner, K H; Messerschmidt, B

1996-05-01

454

Sensitivity-enhanced refractive index sensor by using tapered thin-core fiber based inline Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

A sensitivity-enhanced optical fiber refractive index sensor based on inline Mach-Zehnder interferometer is proposed. The sensor head is formed by splicing a tapered thin-core diameter fiber between two sections of single mode fibers. The taper (less than 1 mm) plays an important role in improving the sensitivity of the sensor. The sensitivity of refractive index is measured to be 0.447 nm for a 1% change of refractive index in the typical refractive index range of 1.333- 1.3725. The whole fabrication process (including splicing and tapering) can be operated by a commercial fiber splicing machine. The proposed sensor also shows the merits of simple structure, low cost, and easy fabrication.

Shi, Jie; Xiao, Shilin; Bi, Meihua

2011-11-01

455

Design of negative-refractive-index materials on the basis of rods with a gradient of the dielectric constant  

NASA Astrophysics Data System (ADS)

The authors propose an approach to the design of negative-refractive-index materials based on the use of dielectric rods with a gradient of the dielectric constant. A triangular-lattice photonic crystal assembled from multilayer dielectric rods with a refractive index approximating a fish-eye profile is shown to exhibit a negative refractive index in the wavelength range defined by the inequality 0.67refractive index equal to -0.85.

Sergentu, V. V.; Ursaki, V. V.; Tiginyanu, I. M.; Foca, F.; Föll, H.; Boyd, Robert W.

2007-08-01

456

Water density and polarizability deduced from the refractive index determined by interferometric measurements up to 250 MPa  

NASA Astrophysics Data System (ADS)

The refractive index of water is precisely determined in the visible light range as a function of the pressure until 250 MPa by means of a new measurement device that uses a special pipe tee included in an interferometer set. This technique allows revisiting the Bradley-Tait and Sellmeier equations to make them dependent on the wavelength and the pressure, respectively. The Bradley-Tait equation for the pressure dependence of the water refractive index is completed by a wavelength-dependent factor. Also, in the considered pressure and wavelength ranges, it is shown that the Sellmeier coefficients can be straightforwardly linked to the pressure, allowing the determination of the refractive index of water for either any wavelength or pressure. A new simple model allows the determination of the density of water as a function of the measured refractive index. Finally, the polarizability of water as function of pressure and wavelength is calculated by means of the Lorentz-Lorenz equation.

Weiss, L.; Tazibt, A.; Tidu, A.; Aillerie, M.

2012-03-01

457

Femtosecond irradiation induced refractive-index changes and channel waveguiding in bulk Ti\\/sup 3+\\/:sapphire  

Microsoft Academic Search

Femtosecond writing of refractive-index changes in sapphire is demonstrated by doping the crystal with an appropriate ion (here: Ti\\/sup 3+\\/) that reduces the threshold of the process. Passive and active buried channel waveguiding is demonstrated.

V. Apostolopoulos; L. Laversenne; T. Colomb; C. Depeursinge; R. P. Salathe´; M. Pollinau; R. Osellame; G. Cerullo; P. Laporta; Nghi Q. Lam

2004-01-01

458

Note: refractive index sensing of turbid media by differentiation of the reflectance profile: does error-correction work?  

PubMed

A widely used method for determining refractive index postulates that the derivative of the angular profile for light reflected from the sample is maximum at the critical angle for total internal reflection (TIR). It is well-known that in turbid media this "differentiation method" yields errors in refractive index. Unexplained anomalies in previous error-calculations are eliminated if one uses a recent model of TIR which departs from traditional Fresnel theory. However we find that, in practical situations, the refractive index obtained by differentiation even after error-correction is significantly different from the best estimate for the refractive index obtained by curve-fitting the reflectance data. Thus the differentiation method lacks scientific validity in turbid media. PMID:22938349

Goyal, K G; Dong, M L; Kane, D G; Makkar, S S; Worth, B W; Bali, L M; Bali, S

2012-08-01

459

Microchanneled Chirped Fiber Bragg Grating Formed by Femtosecond Laser-Aided Chemical Etching for Refractive Index and Temperature Measurements  

Microsoft Academic Search

In this work, a microchanneled chirped fiber Bragg grating (MCFBG) is proposed and fabricated through the femtosecond laser-assisted chemical etching. The microchannel ( $sim$550 $mu$ m) gives access to the external index liquid, thus inducing refractive index (RI) sensitivity to the structure. In the experiment, the transmission bands induced by the reduced effective index in the microchannel region were used

Hongyan Fu; Kaiming Zhou; Pouneh Saffari; Chengbo Mou; Lin Zhang; Sailing He; Ian Bennion

2008-01-01

460

Effect of annealing on the electrical properties and refractive index of HgI2 single crystals  

Microsoft Academic Search

The effect of annealing on the electrical properties and the refractive index of red mercuric iodide (HgI 2) single crystals is investigated. The ac-impedance and phase angle were measured in the frequency range from 100 Hz to 10 kHz at different annealing temperatures. The ac-conductivity, dielectric constants, loss tangent and the refractive index as a function of frequency are determined.

M. H. Abdallah; Y. Ramaden; S. A. Jawad; M. Hassan; M. S. Ahmad; A. M. Zihlif

1995-01-01

461

Effect of annealing on the electrical properties and refractive index of HgI2 single crystals  

Microsoft Academic Search

The effect of annealing on the electrical properties and the refractive index of red mercuric iodide (HgI2) single crystals is investigated. The ac-impedance and phase angle were measured in the frequency range from 100 Hz to 10 kHz at different annealing temperatures. The ac-conductivity, dielectric constants, loss tangent and the refractive index as a function of frequency are determined. The

M. H. Abdallah; Y. Ramaden; S. A. Jawad; M. Hassan; M. S. Ahmad; A. M. Zihlif

1995-01-01

462

Effect of annealing on the electrical properties and refractive index of HgI 2 single crystals  

Microsoft Academic Search

The effect of annealing on the electrical properties and the refractive index of red mercuric iodide (HgI2) single crystals is investigated. The ac-impedance and phase angle were measured in the frequency range from 100 Hz to 10 kHz at different annealing temperatures. The ac-conductivity, dielectric constants, loss tangent and the refractive index as a function of frequency are determined. The

M. H. Abdallah; Y. Ramaden; S. A. Jawad; M. Hassan; M. S. Ahmad; A. M. Zihlif

1995-01-01

463

Simultaneous determination of thickness and refractive index based on time-of-flight measurements of terahertz pulse.  

PubMed

We present a simple technique for simultaneous determination of thickness and refractive index of plane-parallel samples in the terahertz radiation domain. The technique uses time-of-flight measurements of the terahertz pulse. It has been employed on nine different polymers and semiconductor materials, which are transparent for terahertz frequencies. Our results of thickness measurement are in good agreement with micrometer reading. The accuracy in the determination of refractive index is on the order of two decimal points. PMID:22858978

Hussain, Babar; Ahmed, Mushtaq; Nawaz, M; Saleem, M; Razzaq, M; Aslam Zia, M; Iqbal, M

2012-07-20

464

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

465

Measurement of the complex refractive index of tissue-mimicking phantoms and biotissue by extended differential total reflection method  

NASA Astrophysics Data System (ADS)

Refractive index of biotissue is a useful optical parameter in the biomedical field. An extended differential total reflection method is introduced to determine the complex refractive index. The real part is directly determined by differential of the reflectance curve, and the imaginary part is obtained from nonlinear fitting. The method is verified by a series of tissue-mimicking phantoms, porcine muscle and porcine adipose.

Ye, Qing; Wang, Jin; Deng, Zhi-Chao; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

2011-09-01

466

Measurements of strain-induced refractive index changes in shocked LiF using laser-driven flyer plates  

Microsoft Academic Search

The refraction index of compressed LiF directly affects the accuracy of VISAR experiments that use LiF windows. We report on experiments at the LLNL Janus laser that reproduced previous measurements of strain-induced changes to the refractive index. Here laser-driven ramp-compression is used to accelerate aluminum flyer plates that impact a LiF window. The resultant particle velocity is inferred by measuring

Dayne Fratanduono; Maria Barrios; Tom Boehly; David Meyerhofer; Damien Hicks; Peter Celliers; Jon Eggert; G. Collins

2009-01-01

467

Refractive index engineering by fast ion implantations: a generic method for constructing multi-components electro-optical circuits  

Microsoft Academic Search

Refractive index engineering (RI_Eng) by ion implantations is a generic methodology for constructing multi-component integrated circuits of electrooptic and nanophotonic devices with sub-wavelength features operating in the visible - near IR wavelengths. The essence of the method is to perform spatially selective implantations for sculpting complex 3D pre-designed amorphized patterns with sub-wavelength features and reduced refractive index within the volume

Aharon J. Agranat; Alexander Gumennik; Harel Ilan

2010-01-01

468

Analysis on the variation of Ar and He plasma refractive index with temperature in CO2 laser beam welding  

Microsoft Academic Search

According to the quasi-neutrality equation, the law of partial pressure, pressure equation, Saha equation and the principle of superposition on plasma refractive index, the Ar, He plasma's electron density, atom density, ion density and the variation of refractive index with changing of temperature are calculated when the pressure is 1,3,5,7 atm. respectively. Moreover it is analyzed that Ar, He plasma

Jinhe Liu; Fengming Zhang; Decai Yang

1998-01-01

469

A highly sensitive fiber optic sensor based on two-core fiber for refractive index measurement.  

PubMed

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

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

2013-10-22

470

Direct measurement of the x-ray refractive index by Fresnel diffraction at a transparent edge.  

PubMed

We demonstrate the feasibility of measuring x-ray refractive indices by transparent edge diffraction without recourse to the Kramers-Kronig relations. The method requires a coherent x-ray source, a transparent sample with a straight edge, and a high resolution x-ray detector. Here, we use the aluminum K? radiation originating from a laser-produced plasma to coherently illuminate the edge of thin aluminum and beryllium foils. The resulting diffraction patterns are recorded with an x-ray CCD camera. From least-squares fits of Fresnel diffraction modeling to the measured data we determine the refractive index of Al and Be at the wavelength of the Al K? radiation (0.834 nm, 1.49 keV). PMID:23632552

Gayer, C W; Hemmers, D; Stelzmann, C; Pretzler, G

2013-05-01

471

Theoretical modeling of refractive index in ion implanted LiNbO3 waveguides  

NASA Astrophysics Data System (ADS)

A theoretical model is developed to evaluate the roles of various mechanisms, including the molar polarization and molar volume, the spontaneous polarization a