Sample records for refractive index increases

  1. Photonic Crystal Defects with Increased Surface Area for Improved Refractive Index Sensing

    E-print Network

    Weiss, Sharon

    by the wavelength shift of a distinct spectral feature as a function of the refractive index change of analyte those with resonant spectral features such as porous silicon waveguides, provide increased sensitivity analyte volumes, and sharp spectral resonances that enable the detection of small refractive index

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

    PubMed Central

    Pan, Ding; Wan, Quan; Galli, Giulia

    2014-01-01

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

  3. The Index of Refraction

    NSDL National Science Digital Library

    WGBH Educational Foundation

    2011-10-25

    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.

  4. High refractive index photocurable resins

    NASA Astrophysics Data System (ADS)

    Morford, Robert V.; Mercado, Ramil L.; Planje, Curtis E.; Flaim, Tony D.

    2005-04-01

    The performance of optoelectronic devices can be increased by incorporating a high refractive index layer into the system. This paper describes several potential high refractive index resin candidates. Our materials include the added advantages over other systems because the new materials are cationically photocurable and free flowing, have low shrinkage upon cure, have no (or little) volatile organic components, are applicable by a variety of methods (dip coating, roller coating, injection molding, or film casting), can be applied in a variety of thicknesses (10-100 m), are fast-curing, and possess robust physical properties. Particular attention focuses on the refractive index in the visible spectrum, light transmission, and formulation viscosity.

  5. Gradient Refractive Index Lenses.

    ERIC Educational Resources Information Center

    Morton, N.

    1984-01-01

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

  6. Fiber optic refractive index monitor

    DOEpatents

    Weiss, Jonathan David (Albuquerque, NM)

    2002-01-01

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

  7. Refractive index measurement using comparative interferometry

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

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

  8. Variation of corneal refractive index with hydration

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

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

  9. How efiective is the efiective refractive index?

    Microsoft Academic Search

    Brian T. Schwartz; Rafael Piestun

    Photonic crystals are often assigned an efiective refractive index deflned by their dispersion relation. This index can predict their refractive properties consistent with Snell's law, but might not predict their dynamic properties in accordance with the Fresnel formulae. c

  10. Make That Invisible! Refractive Index Matching

    NSDL National Science Digital Library

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

    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.

  11. Negative index of refraction in optical metamaterials

    Microsoft Academic Search

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

    2005-01-01

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

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

    PubMed

    Wankhede, Dnyaneshwar Shamrao

    2012-06-01

    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

  13. Formation of bulk refractive index structures

    DOEpatents

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

    2003-07-15

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

  14. Local Refractive Index Dependence of Plasmon Resonance Spectra from Individual Nanoparticles

    Microsoft Academic Search

    Jack J. Mock; David R. Smith; Sheldon Schultz

    2003-01-01

    We present an experimental optical darkfield microscope study of the dependence of the plasmon resonance spectrum of individual silver nanoparticles on the local index of refraction. We systematically characterize the position of the resonance peaks associated with the same set of individual silver nanoparticles embedded sequentially in index oils with increasing refractive index. This technique effectively allows the local refractive

  15. Cosmology With A Dark Refraction Index

    E-print Network

    B. Chen; R. Kantowski

    2009-02-23

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

  16. High refractive index and temperature sensitivity LPGs for high temperature operation

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  17. Nanofabrication of negative refractive index metasurfaces

    Microsoft Academic Search

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

    2006-01-01

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

  18. Laboratory Measurements of Sea Salt Aerosol Refractive Index

    E-print Network

    Oxford, University of

    generated sodium chloride and sea salt aerosols (SSA) were made with a view to retrieving refractive index . . . . . . . . . . . . . . . . . . . . . . 6 1.2.3 Complex Refractive Index . . . . . . . . . . . . . . . . . . . . 6 1.2.4 Size Distribution

  19. Refractive index enhancement with vanishing absorption in an atomic vapor.

    PubMed

    Proite, N A; Unks, B E; Green, J T; Yavuz, D D

    2008-10-01

    We report a proof-of-principle experiment where the refractive index of an atomic vapor is enhanced while maintaining vanishing absorption of the beam. The key idea is to drive alkali atoms in a vapor with appropriate control lasers and induce a gain resonance and an absorption resonance for a probe beam in a two-photon Raman configuration. The strength and the position of these two resonances can be manipulated by changing the parameters of the control lasers. By using the interference between these two resonances, we obtain an enhanced refractive index without an increase in the absorption. PMID:18851571

  20. Refractive Index Enhancement with Vanishing Absorption in an Atomic Vapor

    E-print Network

    N. A. Proite; B. E. Unks; J. T. Green; D. D. Yavuz

    2008-07-16

    We report a proof-of-principle experiment where the refractive index of an atomic vapor is enhanced while maintaining vanishing absorption of the beam. The key idea is to drive alkali atoms in a vapor with appropriate control lasers and induce a gain resonance and an absorption resonance for a probe beam in a two-photon Raman configuration. The strength and the position of these two resonances can be manipulated by changing the parameters of the control lasers. By using the interference between these two resonances, we obtain an enhanced refractive index without an increase in the absorption.

  1. Matched Index of Refraction Flow Facility

    ScienceCinema

    Mcllroy, Hugh

    2013-05-28

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

  2. Scanning focused refractive-index microscopy

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    PubMed

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

    2015-06-01

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

  4. Refractive index modification of polymers using nanosized dopants

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

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

  5. Cladding mode reorganization in high-refractive-index-coated long-period gratings: effects on the refractive-index sensitivity.

    PubMed

    Cusano, Andrea; Iadicicco, Agostino; Pilla, Pierluigi; Contessa, Luigi; Campopiano, Stefania; Cutolo, Antonello; Giordano, Michele

    2005-10-01

    We theoretically and experimentally investigated the reorganization of cladding modes in high-refractive-index- (HRI-) coated long-period gratings (LPGs), focusing on the influence of refractive-index sensitivity. When azimuthally symmetric nanoscale HRI coatings are deposited along LPG devices, a significant modification of the distribution of cladding modes occurs, depending on the layers' features (refractive index and thickness) and on the external refractive index. In particular, if these parameters are properly chosen, a transition between cladding modes and overlay modes occurs. Numerical and experimental effects of the mode transition on the sensitivity of the surrounding refractive index are described. PMID:16208891

  6. Abnormally high optical transmittance of refractive-index modified ZnO \\/ organic hybrid films

    Microsoft Academic Search

    Takuya Tsuzuki

    2008-01-01

    Hybrid films consisting of ZnO nanoparticles and organic matrices were fabricated at particle concentration levels of up to 60 wt%. The correlation between the refractive index and optical transmittance in the visible light region was investigated. The refractive index of the hybrid films was modified in a continuous manner in the range from 1.44 to 1.55. The refractive index increased

  7. Microwave gain medium with negative refractive index

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  8. Holographic measurements of refractive-index changes.

    PubMed

    Politch, J; Segal, M

    1978-07-01

    We consider here a new method for identifying changes in the index of refraction. A birefringent material was illuminated directly, without a diffuser, and recorded holographically in one step. An unpolarized TEM(00) continuous-wave laser, which emits elliptically polarized light on the time-average scale, was applied in this experiment. With such a holographic recording system three types of reconstruction for the same object are possible, off-axis with laser, off-axis with white light, and on-axis with laser (Gabor hologram). Properties of the holographic recording system and reconstruction of images by the first two of these methods are discussed. PMID:19684687

  9. An updated equation for the refractive index of air

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. Improved retroreflection method for measuring the refractive index of liquids.

    PubMed

    Shao, Duo; Tian, Linghao; Chen, Jingfei; Chen, Xianfeng

    2010-06-01

    We propose a new method for measuring the refractive index of liquids with high precision; the method is based on use of the optical fiber end face. As an example, we investigated the refractive index of sugar solution under varying conditions tens of times. The results show that this method has the advantage of higher stability and repeatability. The concentration and the temperature-dependent refractive index of the sugar solution is also experimentally studied. PMID:20517374

  11. Ultrafast refractive index control of a terahertz graphene metamaterial

    PubMed Central

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

    2013-01-01

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

  12. Recent developments in microstructured fiber Bragg grating refractive index sensors

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

  13. Total external reflection from metamaterials with ultralow refractive index

    Microsoft Academic Search

    Brian T. Schwartz; Rafael Piestun

    2003-01-01

    Metamaterials composed of metal-dielectric nanostructures are engineered to have an effective refractive index less than unity at optical wavelengths. The effect of total external reflection is demonstrated when light from vacuum is incident onto these materials at an angle exceeding the critical angle defined by Snell's law. Novel approaches are discussed to derive the effective index of refraction from the

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

    PubMed

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

    2014-03-31

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

  15. Sensitive liquid refractive index sensors using tapered optical fiber tips.

    PubMed

    Tai, Yi-Hsin; Wei, Pei-Kuen

    2010-04-01

    An optical fiber sensor based on the change of optical confinement in a subwavelength tip is presented. The optical spot is substantially increased when the environmental refractive index (RI) increases from 1.3 to 1.4. By measuring the intensity of low angular spectral components, an intensity sensitivity up to 8000% per RI unit is achieved. The fiber tip sensors take advantage of the small detection volume and real-time responses. We demonstrate the application of the nanofiber sensors for measuring concentrations of acids and evaporation rates of aqueous mixtures. PMID:20364178

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

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Hamill, P.

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Ma, Zhenhe; Zhou, Hongxian

    2015-03-01

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

  18. Transparent nanocomposites based on refractive index matched nanoparticles

    E-print Network

    Candea, George

    Transparent nanocomposites based on refractive index matched nanoparticles Katja Fröhlich1,2, Eleni Figure 1: Left: Pure polymer. Right: With nanoparticles reinforced polymer. Methods and Results nsolvent-resistance by incorporation of nanoparticles as fillers. · Transparency achieved by match of refractive indices n of filler p

  19. Determining the Thickness and Refractive Index of a Mirror

    ERIC Educational Resources Information Center

    Uysal, Ahmet

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  1. Miniature interferometer for refractive index measurement in microfluidic chip

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  2. Engineering a resonant nanocoating for an optical refractive index sensor

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  3. Interferometer for measurement of absolute refractive index and thickness

    Microsoft Academic Search

    Serguei A. Alexandrov; I. V. Chernyh

    1993-01-01

    The interferometer model for measurement of the absolute refractive index of the optical media with the accuracy of 0.00001 has been developed, manufactured and researched. The sample for test to be manufactured as the flat parallel plate. The interferometer gives possibility to defined sample geometrical thickness with accuracy 0.0002 mm simultaneously with index measurement. The range of index and thickness

  4. Refractive index in warm and hot dense matter

    NASA Astrophysics Data System (ADS)

    Faussurier, Gérald; Blancard, Christophe; Cossé, Phillipe

    2015-05-01

    A method to estimate the index of refraction in warm and hot dense matter is proposed. This method combines the Kubo-Greenwood approach, Maxwell equations, and existing codes that calculate photoabsorption and photoemission coefficients in warm and hot dense plasmas. An effective electrical conductivity is calculated from existing opacity codes from which the index of refraction is derived. Illustrations are shown on specific examples.

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

    NASA Astrophysics Data System (ADS)

    Shojaei, S.

    2015-06-01

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

  6. Impact of exposure induced refractive index changes of photoresists on the photolithographic process

    NASA Astrophysics Data System (ADS)

    Erdmann, Andreas; Henderson, Clifford L.; Willson, C. Grant

    2001-06-01

    In many commercial and noncommercial photoresists the real and the imaginary parts of the refractive index are changed during exposure. Using a finite-difference beam-propagation algorithm, we analyze the impact of these nonlinear optical effects on the photolithographic process. Changes of the real part of the refractive index have a considerable impact on dose latitudes, sidewalls, swing curves, iso-dense bias and other process parameters. These effects become more dominant as the thickness of the resist layer increases.

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

    DOEpatents

    Veligdan, James T.

    2004-08-24

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

  8. Refractive index of K9 Glass under Shock Loading

    NASA Astrophysics Data System (ADS)

    Hu, Changming; Wang, Xiang; Cai, Lingcang; Liu, Cangli

    2013-06-01

    We study K9 glass refraction index under shock loading conducted on powder gun,all experimental tests are plate impact loading. The impact veceloty range from 300m/s to 1200m/s, and the measure method is laser interferometer Photon Doppler Velocimetry(PDV) to measure the particle velocity both at the impact interface and free surface, The shock pressure from 2 GPa to 8 GPa, values for refraction are found from velocity corrections that must be made to account for refraction-index changes in the K9 glass due to shock wave motion. Experiment results show that refraction-index of K9 glass changes with the shock pressure in line relations, it can be as measure window to study the interesting materials under 10 GPa during the shock loading.

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

    PubMed

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

    2008-09-18

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    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.

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

    PubMed

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

    2014-07-14

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

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

    SciTech Connect

    Cao, Xiuxia; Li, Jiabo; Li, Jun; Li, Xuhai; Xu, Liang; Wang, Yuan; Zhu, Wenjun; Meng, Chuanmin, E-mail: mcm901570@126.com [Laboratory for Shock Wave and Detonation Physics, Institute of Fluid Physics, Mianyang, Sichuan 621900 (China); Zhou, Xianming, E-mail: xzhou0816@163.com [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610207 (China)

    2014-09-07

    High-pressure refractive index of optical window materials not only can provide information on electronic polarizability and band-gap structure, but also is important for velocity correction in particle-velocity measurement with laser interferometers. In this work, the refractive index of r-cut sapphire window at 1550?nm wavelength was measured under shock pressures of 5–65?GPa. The refractive index (n) decreases linearly with increasing shock density (?) for shock stress above the Hugoniot elastic limit (HEL): n?=?2.0485 (± 0.0197)???0.0729 (± 0.0043)?, while n remains nearly a constant for elastic shocks. This behavior is attributed to the transition from elastic (below HEL) to heterogeneous plastic deformation (above HEL). Based on the obtained refractive index-density relationship, polarizability of the shocked sapphire was also obtained.

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

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

    Microsoft Academic Search

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

    2008-01-01

    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

  15. Integrated Microfibre Device for Refractive Index and Temperature Sensing

    PubMed Central

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

    2012-01-01

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

  16. Measurement of pressure dependent nonlinear refractive index of inert gases.

    PubMed

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

    2010-12-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Bai, Kunlun; Katz, Joseph

    2014-04-01

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

  1. Refractive index of carcinogen-induced rat mammary tumours

    NASA Astrophysics Data System (ADS)

    Zysk, Adam M.; Chaney, Eric J.; Boppart, Stephen A.

    2006-05-01

    Near-infrared optical techniques for clinical breast cancer screening in humans are rapidly advancing. Based on the computational inversion of the photon diffusion process through the breast, these techniques rely on optical tissue models for accurate image reconstruction. Recent interest has surfaced regarding the effect of refractive index variations on these reconstructions. Although many data exist regarding the scattering and absorption properties of normal and diseased tissue, no measurements of refractive index appear in the literature. In this paper, we present near-infrared refractive index data acquired from N-methyl-N-nitrosourea-induced rat mammary tumours, which are similar in pathology and disease progression to human ductal carcinoma. Eight animals, including one control, were employed in this study, yielding data from 32 tumours as well as adjacent adipose and connective tissues.

  2. Mode transition in high refractive index coated long period gratings.

    PubMed

    Cusano, A; Iadicicco, A; Pilla, P; Contessa, L; Campopiano, S; Cutolo, A; Giordano, M

    2006-01-01

    In this work, the numerical and experimental investigation of the cladding modes re-organization in high refractive index (HRI) coated Long Period Gratings (LPGs) is reported. Moreover, the effects of the cladding modes re-organization on the sensitivity to the surrounding medium refractive index (SRI) have been outlined. When azimuthally symmetric nano-scale HRI coatings are deposited along LPGs devices, a significant modification of the cladding modes distribution occurs, depending on the layer features (refractive index and thickness) and on the SRI. In particular, if layer parameters are properly chosen, the transition of the lowest order cladding mode into an overlay mode occurs. As a consequence, a cladding modes re-organization can be observed leading to relevant improvements in the SRI sensitivity in terms of wavelength shift and amplitude variations of the LPGs attenuation bands. PMID:19503312

  3. Conical Dispersion and Effective Zero Refractive Index in Photonic Quasicrystals

    NASA Astrophysics Data System (ADS)

    Dong, Jian-Wen; Chang, Ming-Li; Huang, Xue-Qin; Hang, Zhi Hong; Zhong, Zhi-Chao; Chen, Wen-Jie; Huang, Zhan-Yun; Chan, C. T.

    2015-04-01

    It is recognized that for a certain class of periodic photonic crystals, conical dispersion can be related to a zero-refractive index. It is not obvious whether such a notion can be extended to a noncrystalline system. We show that certain photonic quasicrystalline approximants have conical dispersions at the zone center with a triply degenerate state at the Dirac frequency, which is the necessary condition to qualify as a zero-refractive-index medium. The states in the conical dispersions are extended and have a nearly constant phase. Experimental characterizations of finite-sized samples show evidence that the photonic quasicrystals do behave as a near zero-refractive-index material around the Dirac frequency.

  4. COMPARISON OF REFRACTIVE INDEX ESTIMATED FROM SINGLE-CELL AND BULK OPTICAL PROPERTIES

    Microsoft Academic Search

    Rebecca E. Green; Heidi M. Sosik; Michele D. DuRand; Robert J. Olson

    Particle size and refractive index distributions are important determinants of bulk optical properties in the ocean. We have compared refractive indices of phytoplankton cultures estimated from individual particle and bulk optical measurements. For individual particles, size and refractive index were estimated from flow cytometric forward and side scattering measurements combined with Mie theory. Using an inverse method, bulk refractive index

  5. Dual interferometer system for measuring index of refraction

    NASA Astrophysics Data System (ADS)

    Goodwin, Eric Peter

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

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

    NASA Astrophysics Data System (ADS)

    Sharma, Pankaj; Katyal, S. C.

    2010-06-01

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

  7. Intersubband Optical Absorption Coefficients and Refractive Index Changes in a Gaussian Spherical Quantum Dot

    NASA Astrophysics Data System (ADS)

    Ehsanfard, Najmeh; Kazerani Vahdani, Mohammad Reza

    2015-07-01

    The effects of smooth confining potential on the linear and nonlinear optical properties are investigated with Gaussian confining potential in Quantum Dots (GQDs). To this end the effective mass approximation, the compact density matrix approach, and iterative method are used to calculate linear and nonlinear Absorption Coefficient (AC) and Refractive Index (RI) change of an electron confined in GQD. The effects of confining potential and radius of GQD and also incident optical intensity have been investigated. The results show that increasing confining potential decreases the refractive index magnitude and shifts the peak values to the higher energy regions. It is also shown that the peak values of absorption coefficient increase by increasing confining potential. Both absorption coefficient and refractive index experience red shift by increasing the size of quantum dot. It is also shown that transition from step potential to Gaussian potential makes AC and RI to experience a blue shift.

  8. Complex refractive index of Martian dust - Wavelength dependence and composition

    NASA Technical Reports Server (NTRS)

    Pang, K.; Ajello, J. M.

    1977-01-01

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

  9. Pigment mass density and refractive index determination from optical measurements

    NASA Astrophysics Data System (ADS)

    Vargas, William E.; Niklasson, Gunnar A.

    1997-02-01

    The reflectance and transmittance of polymer films containing colloidal particles are characterized by specular and diffuse components which, for a given wavelength of the incident radiation, depend on particle size and composition, particle concentration, and film thickness. Pigment particles do not in general exhibit bulk densities or bulk optical constants. In this paper we introduce a method to determine the mass density and refractive index of non-absorbing or absorbing particles from experimental measurements. A four-flux radiative transfer model is used to describe the optical properties of dilute mixtures of silicon dioxide and titanium dioxide particles in a polymer matrix. The refractive index of the particles is varied from bulk values, in order to achieve good agreement with experimental reflectance and transmittance spectra. The obtained refractive indices can be related to the mass density of the particle material by the Clausius - Mossotti equation.

  10. Measuring the refractive index with precision goniometers: a comparative study

    NASA Astrophysics Data System (ADS)

    Krey, Stefan; Off, Dennis; Ruprecht, Aiko

    2014-03-01

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

  11. Gravitational Lensing Analyzed by Graded Refractive Index of Vacuum

    E-print Network

    Xing-Hao Ye; Qiang Lin

    2008-02-13

    We found strong similarities between the gravitational lensing and the conventional optical lensing. The similarities imply a graded refractive index description of the light deflection in gravitational field. We got a general approach to this refractive index in a static spherically symmetric gravitational field and obtained its exterior and interior solutions exactly through the general relativity. In weak field case, the two solutions come to a simple unified exponential function of the gravitational potential. With these results, the gravitational lensing can be analyzed in a convenient optical way. Especially, the long puzzling problem of the central image missing can be solved easily. We also pointed out that the graded refraction property of the gravitational spacetime is related to the vacuum influenced by the gravitational matter.

  12. Optical glass: refractive index change with wavelength and temperature

    NASA Astrophysics Data System (ADS)

    Englert, Marion; Hartmann, Peter; Reichel, Steffen

    2014-05-01

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

  13. Experimental Verification of a Negative Index of Refraction

    Microsoft Academic Search

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

    2001-01-01

    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

  14. A Fibre Reflectometer To Monitor Refractive Index Changes In Fluids

    NASA Astrophysics Data System (ADS)

    Legendre, J. P.

    1986-01-01

    The standard fibre optic reflectometer has been reexamined. Reflectometers have been configured to measure various physical parameters but the fundamental parameter that is sensed is refractive index. This study has focussed on the basic characteristics of this simple sensor, its linearity, its sensitivity and its potential problem areas when applied in real world situations.

  15. Metamaterials with ultralow index of refraction: properties and applications

    Microsoft Academic Search

    Brian T. Schwartz; Rafael Piestun

    2003-01-01

    There has been a growing interest in the design and fabrication of composite materials to enhance the flexibility in specifying their optical properties for device applications. Here we show that metamaterials composed of metal-dielectric nano-structures can be engineered to have an effective refractive index below unity at optical wavelengths. These materials show intriguing optical properties including total external reflection. Different

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

    SciTech Connect

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

    2014-05-12

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

  17. ORIGINAL ARTICLE Quantifying the refractive index dispersion of a pigmented

    E-print Network

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

  18. Humidity contribution to the refractive index structure function C 2

    E-print Network

    Chang, Mark J. L.

    Humidity contribution to the refractive index structure function C 2 n . Carlos O. Font, Mark P. JË?uez, Puerto Rico 00680 2 U.S. Naval Research Laboratory, Washington D.C. 20375 ABSTRACT Humidity and C 2 n that C 2 n in the infrared region is also function of humidity, in addition to temperature and pressure

  19. Humidity contribution to the refractive index structure function C2

    E-print Network

    Chang, Mark J. L.

    Humidity contribution to the refractive index structure function C2 n. Carlos O. Font, Mark P. J. L¨uez, Puerto Rico 00680 2U.S. Naval Research Laboratory, Washington D.C. 20375 ABSTRACT Humidity and C2 n data function of humidity, in addition to temperature and pressure. Keywords: Strength of turbulence, humidity

  20. Index of Refraction Profile in a Highway Mirage

    NASA Astrophysics Data System (ADS)

    Nelsen, Bryan; Lobue, James; Edwards, Mark

    2003-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

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

  3. [Complex refractive index measurement of fly ash particles using suspension spectral transmission method].

    PubMed

    Xing, Jian; Sun, Xiao-Gang; Zhou, Chen; Yuan, Gui-Bin; Zhang, Zhi-Lin

    2010-12-01

    Spectral complex refractive index of fly ash particles is an important parameter in the processing of scattering properties calculation. On the basis of theory about inversion of complex refraction index using transimission method, a novel method was proposed, in which fly ash particles were dispersed in the water to compose turbid liquid, and spectral transmissivity of turbid liquid was measured using visible spectrophotometer. Particles size distribution was measured using laser particles sizing. So complex refraction index of fly ash particles was inverted simply. The result indicated that no signifcant absorption appeared in the visible wavelength range for fly ash particles, but transmittance decreased with wavelength increasing. The inversion results from the proposed method agreed with KBr sampling method. The proposed method is simpler, and has fewer constraints, meanwhile the inverion wavelength will be expanded if using infrared spectrophotometer. PMID:21322243

  4. Monodisperse, high refractive index, highly charged ZnS colloids self assemble into crystalline colloidal arrays

    E-print Network

    Asher, Sanford A.

    Monodisperse, high refractive index, highly charged ZnS colloids self assemble into crystalline synthesis of monodisperse, highly surface charged, high refractive index ZnS spherical particles by using surface. These monodisperse highly charged ZnS particles are some- what porous and have a refractive index

  5. Measurements of refractive index and near infrared absorbance of hemoglobin solutions incubated with glucose

    Microsoft Academic Search

    Olga S. Zhernovaya; Valery V. Tuchin; Igor Meglinski; Laurie Ritchie

    2007-01-01

    The purpose of this study is to investigate the effect of presence of glucose and glycation of hemoglobin on refractive index and absorbance of aqueous hemoglobin solutions with different glucose concentrations. It is shown that the changes of refractive index caused by glycation of hemoglobin may be observed using refractive index measurements.

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

    E-print Network

    Refractive index and dispersion of butterfly chitin and bird keratin measured by polarizing the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive index values of the glass scales of the butterfly Graphium sarpedon are, at wavelengths 400, 500 and 600

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  8. The whistler mode refractive index as a function of gyrofrequency

    SciTech Connect

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

    2011-08-15

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

  9. Refractive Index Compensation in Over-Determined Interferometric Systems

    PubMed Central

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

    2012-01-01

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

  10. Elasticity, strength, and refractive index of argon at high pressures

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Gleason, A. E.; Yan, J. Y.; Koski, K. J.; Clark, Simon; Jeanloz, Raymond

    2010-04-01

    High-pressure Brillouin spectroscopy of polycrystalline argon, measured using two scattering angles ( 180° and 70° ), determines the isotropic elastic moduli, shear strength, equation of state, and refractive index of face-centered-cubic argon from 1.3 to 30 GPa at room temperature. The index of refraction n=1.33-1.67 over this pressure range. An Eulerian finite-strain analysis (Birch-Murnaghan equation of state) yields an isothermal bulk modulus and pressure derivative KT=15.1(±1.1)GPa and KT'=5.4(±0.3) at 2 GPa. The resulting equation of state agrees well with previous x-ray diffraction measurements, illustrating the suitability of high-pressure Brillouin scattering for characterizing the elasticity and strength of polycrystalline materials.

  11. Correction of group refraction index based on pulse trains interference

    NASA Astrophysics Data System (ADS)

    Wei, Dong; Aketagawa, Masato

    2015-02-01

    We propose a new concept for an unconventional type of two-color method for interferometry-based length measurements based on the adjacent pulse repetition interval length (APRIL), which is the physical length associated with the pulse repetition period. We demonstrate by numerical simulations that if the wavelength-based two-color method can eliminate the inhomogeneous disturbance of effects caused by the phase refractive index, then the APRIL-based two-color method can eliminate the air turbulence of errors induced by the group refractive index. We show that our analysis will benefit the pulse-laser-based two-color method, which secures traceability to the definition of the meter.

  12. Transition of refractive index contrast in course of grating growth.

    PubMed

    Sabel, Tina; Zschocher, Michael

    2013-01-01

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

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

    PubMed

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

    2012-01-01

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

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

    Microsoft Academic Search

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

    1987-01-01

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

  15. Propagation of photons in homogeneous magnetic fields: Index of refraction

    Microsoft Academic Search

    Wu-Yang Tsai; Thomas Erber

    1975-01-01

    The index of refraction associated with the vacuum polarization induced ; by homogeneous magnetic fields is calculated for two cases: high energy photons ; traversing fields weak compared with the critical field, H\\/sub cr\\/ = m$sup ; 2$c³\\/eh approximately 4.41 x 10¹³ G; and low energy photons in fields ; of arbitrary intensity. Some implications for the physical optics of

  16. Refractive Index of Lithium Fluoride Ramp Compressed to 800 GPa

    NASA Astrophysics Data System (ADS)

    Fratanduono, Dayne

    2011-10-01

    The compression of materials to high pressure can alter their optical properties in ways that provide insight into the resulting structural changes. Under strong shock compression, transparent insulators transform into conducting fluids as a result of pressure-induced reduction of the band gap and thermal promotion of electrons across that gap. LiF is ramp compressed to 800 GPa on the Omega Laser Facility without generating shocks, producing high pressures at significantly lower temperatures than would be created by shock waves. Ramp compressed lithium fluoride (LiF) is observed to remain transparent to 800 GPa, pressures seven times higher than previous shock compression experiments. The ramp-compressed refractive index of LiF is measured at pressures up to 800 GPa and depends linearly on density. This is the highest-pressure refractive index measurement made to date. The linear dependence of the refractive index and density is examined using a single oscillator model. This model indicates that the linear behavior is a result of monoatomic closure of the band gap. Extrapolation of these results indicates that the band gap closure (metallization) will be greater than 4,000 GPa. The high metallization pressure of LiF is attributed to its large band gap and isoelectronic counterparts that exhibit high metallization pressures. The observed high-pressure transparency and measurement of LiF refractive index enables advancement of in situ experiments to higher-pressure regimes. In collaboration with T.R. Boehly (LLE), M.A. Barrios (LLE-now at LLNL), D.D. Meyerhofer (LLE), J.H. Eggert (LLNL), R.F. Smith (LLNL), D.G. Hicks (LLNL), P.M. Celliers (LLNL), and G.W. Collins (LLNL). This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

  17. Fiber optic-based refractive index sensing at INESC Porto.

    PubMed

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

    2012-01-01

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

  18. Light localization induced by a random imaginary refractive index

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  19. Enhanced refractive index without absorption in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  20. Glory Oscillations in the Index of Refraction for Matter Waves

    Microsoft Academic Search

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

    2002-01-01

    We have measured the index of refraction for sodium de Broglie waves in gases\\u000aof Ar, Kr, Xe, and nitrogen over a wide range of sodium velocities. We observe\\u000aglory oscillations -- a velocity-dependent oscillation in the forward\\u000ascattering amplitude. An atom interferometer was used to observe glory\\u000aoscillations in the phase shift caused by the collision, which are larger

  1. Enhanced refractive index without absorption in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  2. Thermal radiation in quasiperiodic photonic crystals with negative refractive index

    Microsoft Academic Search

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

    2007-01-01

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

  3. Thermal radiation in quasiperiodic photonic crystals with negative refractive index

    Microsoft Academic Search

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

    2007-01-01

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

  4. A RICH with aerogel: a study of refractive index uniformity

    E-print Network

    Alemi, M; Calvi, M; Matteuzzi, C; Musy, M; Perego, D L; Easo, S

    2004-01-01

    The use of aerogel as a radiator in the RICH detectors of LHCb is a challenge due to the hot environment of the hadron collider LHC. Large size tiles of silica aerogel were recently produced with unprecedented optical quality for such dimensions. Results of laboratory measurements and beam tests are briefly reported. A description of a method to measure the uniformity of the index of refraction within the tile is given.

  5. Surface plasmon resonance based fiber optic refractive index sensors

    NASA Astrophysics Data System (ADS)

    Hlubina, Petr; Kadulova, Miroslava; Ciprian, Dalibor

    2014-12-01

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

  6. Analyzing refractive index profiles of confined fluids by interferometry.

    PubMed

    Kienle, Daniel F; Kuhl, Tonya L

    2014-12-01

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

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

    SciTech Connect

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  9. Refractive index sensing with hyperbolic metamaterials: strategies for biosensing and nonlinearity enhancement.

    PubMed

    Vasilantonakis, N; Wurtz, G A; Podolskiy, V A; Zayats, A V

    2015-06-01

    Metamaterials with hyperbolic dispersion based on metallic nanorod arrays provide a flexible platform for the design of bio- and chemical sensors and nonlinear devices, allowing the incorporation of functional materials into and onto the plasmonic metamaterial. Here, we have investigated, both analytically and numerically, the dependence of the optical response of these metamaterials on refractive index variations in commonly used experimental sensing configurations, including transmission, reflection, and total internal reflection. The strategy for maximising refractive index sensitivity for different configurations has been considered, taking into account contributions from the superstrate, embedding matrix, and the metal itself. It is shown that the sensitivity to the refractive index variations of the host medium is at least 2 orders of magnitude higher than to the ones originating from the superstrate. It is also shown that the refractive index sensitivity increases for higher-order unbound and leaky modes of the metamaterial sensor. The impact of the transducer's thickness was also analysed showing significant increase of the sensitivity for the thinner metamaterial layers (down to few 0.01 fraction of wavelength and, thus, requiring less analyte) as long as modes are supported by the structure. In certain configurations, both TE and TM-modes of the metamaterial transducer have comparable sensitivities. The results provide the basis for the design of new ultrasensitive chemical and biosensors outperforming both surface plasmon polaritons and localised surface plasmons based transducers. PMID:26072797

  10. Ultraviolet light induced refractive index structures in germanosilica

    NASA Astrophysics Data System (ADS)

    Svalgaard, M.

    1997-03-01

    The focus of the research presented in this ph.d. thesis is refractive index structures photoinduced in germanonsilica waveguides with ultra-violet (UV) radiation. The physical mechanisms involved in photosensitivity and applications of a wide range of UV induced refractive index structures in both optical fibers and planar wavguides have been explored. This work includes fabrication of fiber Bragg gratings and design of equipment intended for enhancement of photosensitivity by indiffusion of molecular hydrogen. New insight regarding UV induced reactions in germanosilica has been provided through application of a scanning near-field optical microscope to obtain high resolution images of UV induced refractive index structures and by monitoring the dynamics of UV induced index changes and luminescence. During part of my ph.d. project I have worked at the National Institute of Standards and Technolgy in Colorado (USA) under supervision of Dr. Sarah L. Gilbert, fabricating and characterizing erbium doped fiber lasers incorporating UV written Bragg gratings. Due to their compact structure, such devices are shown to exhibit a frequency stability several orders of magnitude better than lasers incorporating bulk optics. Finally, I have developed a new method for direct UV writing of planar waveguide devices using a focussed continuous wave UV laser beam which is scanned across a photosensitive thin film deposited on a silicon wafer. Contrary to other waveguide fabrication techniques this method requires no additional wafer processing. By demonstrating a wide variety of integrated devices it is shown that the performance of this method in terms of waveguide loss, flexibility and fabrication yield rivals or surpasses that currently obtainable with other more elaborate techniques.

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

    PubMed Central

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

    2012-01-01

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

  12. Absorption Spectra and Refractive Index Changes of an Exciton in a Core/Shell Quantum Dot

    NASA Astrophysics Data System (ADS)

    Xie, Wen-Fang

    2015-05-01

    The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov-Bohm oscillation in core/shell quantum dots.

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

    E-print Network

    Sung, Yongjin

    The refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, the refractive ...

  14. Refractive index of colored films of molybdenum trioxide

    NASA Astrophysics Data System (ADS)

    Reyes-Betanzo, C.; Herrera-Pérez, J. L.; Cocoletzi, Gregorio H.; Zelaya-Angel, O.

    2000-07-01

    We apply a film thickness-independent technique to measure the index of refraction n=n+ik for amorphous thin films of molybdenum trioxide. The films were grown by thermal evaporation and then colored by light irradiation for different exposure times. Data for the reflectivity and differential reflectivity yield n and show no dependence on the density of color centers. We find that small variations of the absorption coefficient induce changes in the differential reflectance line shape at angles different from the Brewster angle.

  15. Measurements of nonlinear refractive index in scattering media

    PubMed Central

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

    2012-01-01

    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. PMID:20588401

  16. Tissue Refractive Index Fluctuations Report on Cancer Development

    NASA Astrophysics Data System (ADS)

    Popescu, Gabriel

    2012-02-01

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

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

    PubMed Central

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

    2011-01-01

    Crystallins are present in the lens at extremely high concentrations in order to provide transparency and generate a high refractive power of the lens. The crystallin families prevalent in the highest density lens tissues are ? crystallins in vertebrates and S crystallins in cephalopods. In parallel evolution, both have evolved molecular refractive index increments 5 – 10 % above those of most proteins. Although this is a small increase, it is statistically very significant and can be achieved only by very unusual amino acid compositions. In contrast, such a molecular adaptation to aid in the refractive function of the lens did not occur in crystallins that are preferentially located in lower density lens tissues, such as vertebrate ? crystallin and taxon specific crystallins. In the current work, we apply a model of non-interacting hard spheres to examine the thermodynamic contributions of volume exclusion at lenticular protein concentrations. We show that the small concentration decrease afforded by the higher molecular refractive index increment of crystallins can amplify nonlinearly to produce order of magnitude differences in chemical activities, and lead to reduced osmotic pressure and the reduced propensity for protein aggregation. Quantitatively, this amplification sets in only at protein concentrations as high as those found in hard lenses or the nucleus of soft lenses, in good correspondence to the observed crystalline properties in different tissues and different species. This suggests that volume exclusion effects provide the evolutionary driving force for the unusual refractive properties and the unusual amino acid compositions of ? crystallins and S crystallins. PMID:21566271

  18. The density and refractive index of adsorbing protein layers.

    PubMed

    Vörös, Janos

    2004-07-01

    The structure of the adsorbing layers of native and denatured proteins (fibrinogen, gamma-immunoglobulin, albumin, and lysozyme) was studied on hydrophilic TiO(2) and hydrophobic Teflon-AF surfaces using the quartz crystal microbalance with dissipation and optical waveguide lightmode spectroscopy techniques. The density and the refractive index of the adsorbing protein layers could be determined from the complementary information provided by the two in situ instruments. The observed density and refractive index changes during the protein-adsorption process indicated the presence of conformational changes (e.g., partial unfolding) in general, especially upon contact with the hydrophobic surface. The structure of the formed layers was found to depend on the size of the proteins and on the experimental conditions. On the TiO(2) surface smaller proteins formed a denser layer than larger ones and the layer of unfolded proteins was less dense than that adsorbed from the native conformation. The hydrophobic surface induced denaturation and resulted in the formation of thin compact protein films of albumin and lysozyme. A linear correlation was found between the quartz crystal microbalance measured dissipation factor and the total water content of the layer, suggesting the existence of a dissipative process that is related to the solvent molecules present inside the adsorbed protein layer. Our measurements indicated that water and solvent molecules not only influence the 3D structure of proteins in solution but also play a crucial role in their adsorption onto surfaces. PMID:15240488

  19. The Density and Refractive Index of Adsorbing Protein Layers

    PubMed Central

    Vörös, Janos

    2004-01-01

    The structure of the adsorbing layers of native and denatured proteins (fibrinogen, ?-immunoglobulin, albumin, and lysozyme) was studied on hydrophilic TiO2 and hydrophobic Teflon-AF surfaces using the quartz crystal microbalance with dissipation and optical waveguide lightmode spectroscopy techniques. The density and the refractive index of the adsorbing protein layers could be determined from the complementary information provided by the two in situ instruments. The observed density and refractive index changes during the protein-adsorption process indicated the presence of conformational changes (e.g., partial unfolding) in general, especially upon contact with the hydrophobic surface. The structure of the formed layers was found to depend on the size of the proteins and on the experimental conditions. On the TiO2 surface smaller proteins formed a denser layer than larger ones and the layer of unfolded proteins was less dense than that adsorbed from the native conformation. The hydrophobic surface induced denaturation and resulted in the formation of thin compact protein films of albumin and lysozyme. A linear correlation was found between the quartz crystal microbalance measured dissipation factor and the total water content of the layer, suggesting the existence of a dissipative process that is related to the solvent molecules present inside the adsorbed protein layer. Our measurements indicated that water and solvent molecules not only influence the 3D structure of proteins in solution but also play a crucial role in their adsorption onto surfaces. PMID:15240488

  20. Dark Matter Constraints from a Cosmic Index of Refraction

    SciTech Connect

    Gardner, Susan; Latimer, David C.

    2009-04-01

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

  1. Control of Refractive Index Distribution for High-Bandwidth Graded Index Plastic Optical Fiber

    Microsoft Academic Search

    Makoto Asai; Kazuma Nehashi; Yasuhiro Koike

    2008-01-01

    The graded index plastic optical fiber (GI-POF) has been proposed as the transmission medium to realize high-speed information transmission. We have succeeded in fabricating a GI-POF by the coextrusion process, a method that allows continuous fabrication of GI-POF. Although it has been indicated that the refractive index distribution of GI-POF fabricated by this process is formed by Fick diffusion with

  2. Refractive index and density of ammonia ice at different temperatures of deposition

    NASA Astrophysics Data System (ADS)

    Satorre, M. Á.; Leliwa-Kopystynski, J.; Santonja, C.; Luna, R.

    2013-07-01

    The optical properties and density of ammonia have not been exhaustively studied despite the relevance of these characteristics in astrophysical scenarios. This work presents new data pertaining to the real part of the refractive index of ammonia at 632.8 nm and the density at different temperatures of deposition ranging from 13 K to ammonia's desorption temperature of approximately 110 K. The results indicate a significant variability for both parameters versus temperature: an increase of 50% for the density and of 10% for the refractive index as the temperature increases in the range of 13-60 K; at temperatures greater than 60 K, a constant value is reached for both parameters. This initial variation and the following plateau reflect structural differences in the form of ammonia at low and high temperatures of deposition that can play an important role in the interaction of ammonia with other molecules of astrophysical interest.

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

    PubMed

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

    2003-03-14

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  5. Effect of polymer chain in coexisting liquid phases by refractive index measurements

    Microsoft Academic Search

    Pannur Venkatesu

    2005-01-01

    The behavior of polyethylene oxide (PEO, molecular weight, Mw=9×105, as an impurity) was studied in the critical binary mixture of nitroethane (NE)+3-methylpentane (MP) by refractive index measurements. The measurements were performed at three different PEO concentrations (C=0.373, 0.759, and 1.509 mg\\/cc) in the near critical composition of NE\\/MP. We observed that the coexisting phase region shifts down with increasing PEO

  6. Refractive index dynamics of InAs/GaAs quantum dots

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  7. 3-D photo-patterning of refractive index structures in photosensitive thin film materials

    DOEpatents

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

    2002-01-01

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

  8. Strong ion migration in high refractive index contrast waveguides formed by femtosecond laser pulses in phosphate glass

    NASA Astrophysics Data System (ADS)

    Hoyo, J.; Sotillo, Belen; Hernandez, M.; Toney Fernandez, T.; Haro-González, Patricia; Jaque, D.; Fernandez, P.; Domingo, C.; Siegel, J.; Solis, J.

    2014-05-01

    Strong ion migration in shown to enable the production of high refractive index contrast waveguides by fs-laser writing in a commercial (Er,Yb)-doped phosphate based glass. Waveguide writing was performed using a high repetition rate fslaser fibre amplifier operated at 500 kHz and the slit shaping technique. Based on measurements of the NA of waveguides, the positive refractive index change (?n) of the guiding region has been estimated to be ˜1-2 x10-2. The compositional maps of the waveguides cross-sections performed by X-ray microanalysis evidenced a large increase of the La local concentration in the guiding region up to ~25% (relative to the non-irradiated material). This large enrichment in La was accompanied by the cross migration of K to a neighbouring low refractive index zone. The refractive index of the La-phosphate glass increases linearly with the La2O3 content (?n per mole fraction increase of La2O3 ? 5x10-3) mainly because of the relative mass of the La3+ ions. The density increase without substantial modification of the glass network was confirmed by space-resolved micro-Raman spectroscopy measurements showing minor variations in the (PO2)sym vibration Raman band. These results provide evidence for the feasibility of adapting the glass composition for enabling laser-writing of high refractive index contrast structures via spatially selective modification of the glass composition.

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

    NASA Astrophysics Data System (ADS)

    van der Horst, Astrid

    2006-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-07-01

    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.

  11. Quantum vacuum emission from a refractive index front

    E-print Network

    Maxime Jacquet; Friedrich Koenig

    2015-04-28

    We consider a boundary separating two otherwise homogeneous regions of a dielectric, that is moving at approximately the group velocity of light. We investigate the emission of light from the quantum vacuum by this moving refractive index step in 1+1 dimensions for realistic dispersive media. We extend an analytical framework based on the Hopfield model [1] to calculate the emission from all modes at any frequency. We establish conditions for analogue event horizons and study the various mode configurations with and without horizons. We then present analytically calculated emission spectra in the moving and laboratory frame. We find that the emission spectrum is highly structured into intervals of emission with black hole-, white hole-, and no horizons. We also calculate the number of photons emitted as a function of the step height and find a power law of 2.5 for low step heights.

  12. Real part of refractive index measurement approach for absorbing liquid.

    PubMed

    Liu, Hao; Ye, Junwei; Yang, Kecheng; Xia, Min; Guo, Wenping; Li, Wei

    2015-07-01

    An algorithm based on use of a reflected refractometer to measure the real part of the refractive index (RI) for an absorbing liquid is presented. The absorption of liquid will blur the division between bright and dark regions on a Fresnel reflective curve. However, the reflective ratio at some incident angles that are less than the critical angle have little sensitivity to absorbability. Unlike common methods that extract RI from reflectivity in critical angle vicinity, the presented method acquires the real RI from reflective ratio at a subcritical angle. Supported by the theoretical analysis and experimental results on a reflected refractometer, we have achieved accuracy better than 3×10-4 RIU on ink samples with absorption coefficient around 300??cm-1. Additional tests on Alizarin yellow GG solutions prove that the subcritical algorithm is feasible and of high accuracy. PMID:26193150

  13. Inline fiber interference-based refractive-index sensor

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  14. Textile inspired flexible metamaterial with negative refractive index

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    PubMed

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

    2007-03-01

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

  16. Semiconductor laser devices having lateral refractive index tailoring

    DOEpatents

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

    1990-01-01

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

  17. Density and refractive index measurements of 1-ethyl-3-methylimidazolium-based ionic liquids

    Microsoft Academic Search

    Allan N. Soriano; Bonifacio T. Doma Jr.; Meng-Hui Li

    2010-01-01

    This work was the continuation of our previous study where the correlations between density and refractive index of pure systems of ionic liquids were examined. The density and refractive index of five 1-ethyl-3-methylimidazolium-based ionic liquids were measured at standard pressure and temperature up to 353.2K. Densities and refractive indices of the studied ionic liquids were presented as a function of

  18. Ordinary and extraordinary complex refractive index of the lead tungstate (PbWO 4) crystal

    Microsoft Academic Search

    S. Baccaro; L. M. Barone; B. Borgia; F. Castelli; F. Cavallari; I. Dafinei; F. de Notaristefani; M. Diemoz; A. Festinesi; E. Leonardi; E. Longo; M. Montecchi; G. Organtini

    1997-01-01

    The ordinary and the extraordinary complex refractive index of PbWO4 together with the crystal optical axis orientation are determined on the basis of transmittance and reflectance measurements at normal incidence with polarised light and the measurement of the separation angle between the ordinary and the extraordinary ray at various laser wavelengths. The real part of the extraordinary complex refractive index

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

    Microsoft Academic Search

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

    1999-01-01

    A method for calculating the refractive index of GRIN optical fiber from its transverse interference pattern is presented.In this method the transverse interference fringe pattern through an optical fiber using a sheet of light is applied to get the refractive index profile of it. The optical fiber is not immersed in a matching liquid as used in different techniques [Barakat

  20. Generating Bessel beams with a tunable acoustic gradient index of refraction lens

    E-print Network

    Arnold, Craig B.

    Generating Bessel beams with a tunable acoustic gradient index of refraction lens Tracy Tsai a, Princeton University, Princeton, NJ ABSTRACT The Tunable Acoustic Gradient Index of Refraction (TAG) lens is shown to be an alternative method of generating Bessel beam for optical manipulation. The TAG lens

  1. High-speed varifocal imaging with a tunable acoustic gradient index of refraction lens

    E-print Network

    Arnold, Craig B.

    High-speed varifocal imaging with a tunable acoustic gradient index of refraction lens Alexandre by the speed at which focal length can be changed. Here we demonstrate the use of a tunable acoustic gradient (TAG) index of refraction lens as a fast varifocal element. The optical power of the TAG lens varies

  2. Short communication On the refractive index of ageing dispersions of Laponite

    Microsoft Academic Search

    Ravi Kumar; K. Muralidhar; Yogesh M. Joshi

    Aqueous dispersion of Laponite at low ionic concentration is of interest since it undergoes structural evolution with respect to time, which is usually termed as ageing. In this work we study the refractive index behavior as a function of ageing time, concentration and temperature. We observed that the extended Lorenz-Lorentz equation fitted the refractive index dependence on concentration and temperature

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

    SciTech Connect

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

    2005-04-18

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

  4. Glory Oscillations in the Index of Refraction for Matter Waves Tony D. Roberts,1

    E-print Network

    Cronin, Alex D.

    Glory Oscillations in the Index of Refraction for Matter Waves Tony D. Roberts,1 Alexander D October 2002) We have measured the index of refraction for sodium de Broglie waves in gases of Ar, Kr, Xe, and N2 over a wide range of sodium velocities. We observe glory oscillations--a velocity

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

    PubMed Central

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

    2007-01-01

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

  6. Dynamic properties of photonic crystals and their effective refractive index

    Microsoft Academic Search

    Brian T. Schwartz; Rafael Piestun

    2005-01-01

    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

  7. A posteriori error of the transmission interference method of thin film refractive index calculation

    NASA Astrophysics Data System (ADS)

    Sisonyuk, A. G.

    1996-04-01

    The method of a posteriori error calculation has been applied to the calculation of the refractive index and thickness of optical thin films from spectrophotometric transmission interference measurements. The refractive index and thickness of transparent or semitransparent thin film deposited on a transparent substrate can be calculated using both Edser - Butler and Swanepoel equations. A least-squares method and smoothing have been used to refine the Swanepoel's estimate and a correlation analysis has been applied to the differences between the two refractive index estimates. The refractive index covariance function is approximated by an exponential function and is then used in the statistical modelling process. The method has been applied to the calculation of the refractive index of a 0022-3727/29/4/020/img1 thin film deposited on a quartz substrate. In practice the method is especially useful in view of its ability to detect the deterioration of data caused by instrumental drift.

  8. Photo-induced refractive-index changes in filaments formed in glass with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

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

    2000-11-01

    Recently, the structural modifications of glass by focusing femtosecond laser pulses have been demonstrated. We present photo-induced structural changes in silica glass with femtosecond laser pulses. We investigated the relationship between the formation of filaments and local refractive index changes in silica glass. In situ observation revealed the coincidence between the location of filament and that of refractive index change. The observation also showed that the region of refractive index change elongates toward the upstream direction of laser pulses with the exposure time. The region of refractive index change was several hundred- micron long and the diameter was smaller than two microns. The length of the region was dependent on the numerical aperture of focusing lenses. The refractive index change was confirmed to be as large as 0.01 by three different methods. We fabricated a 2-mm waveguide by translating the sample along the optical axis.

  9. Index of refraction of magneto-dielectric photonic crystals

    NASA Astrophysics Data System (ADS)

    Krokhin, Arkadii; Reyes, Edgar

    2004-03-01

    We study the low-frequency limit for two-dimensional magneto-dielectric photonic crystals (MDPC's). The system consists of cylinders (material a) arranged periodically in a background (material b). Both materials are characterized by their permittivities (\\varepsilon_a, \\varepsilon_b) and permeabilities (?_a, ?_b). The effective index of refraction n_eff(hatk) = lim_karrow 0 (ck/?) is calculated as a function of the direction of propagation hatk= k/k for the E- and H-polarized modes. We use the method of plane waves developed for non-magnetic photonic crystals.^1 We show that unlike non-magnetic photonic crystals, where the E-mode is "ordinary" and the H-mode is "extraordinary," now the both modes exhibit extraordinary behavior. Because of this specific feature the optical properties of the MDPC's cannot be characterized by index (or Fresnel) ellipsoid. We, thus, predict that artificial structures, MDPC's, possess optical properties that do not exist for natural crystals. This work is supported by CONACyT, grant 42136-F. [1] P. Halevi, A.A. Krokhin, J. Arriaga, Phys. Rev. Lett. 82, 719 (1999); A.A. Krokhin, P. Halevi, J. Arriaga, Phys. Rev. B 65, 115208 (2002).

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    SciTech Connect

    Stein, A.; Kocaman, S.; Aras, M.S.; Hsieh, P.-C. McMillan, J.F.; Biris, C.G.; Panoiu, N.C.; Yu, M.B.; Kwong, D.L.; Wong, C.W.

    2011-08-01

    We show that optical beams propagating in path-averaged zero-index photonic crystal superlattices can have zero phase delay. The nanofabricated superlattices consist of alternating stacks of negative index photonic crystals and positive index homogeneous dielectric media, where the phase differences corresponding to consecutive primary unit cells are measured with integrated Mach-Zehnder interferometers. These measurements demonstrate that at path-averaged zero-index frequencies the phase accumulation remains constant and equal to zero despite the increase in the physical path length. We further demonstrate experimentally that these superlattice zero- bandgaps remain invariant to geometrical changes of the photonic structure and have a center frequency which is deterministically tunable. The properties of the zero- gap frequencies, optical phase, and effective refractive indices are well described by detailed experimental measurements, rigorous theoretical analysis, and comprehensive numerical simulations.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1995-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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.

  15. Lifetime Reduction and Enhanced Emission of Single Photon Color Centers in Nanodiamond via Surrounding Refractive Index Modification.

    PubMed

    Khalid, Asma; Chung, Kelvin; Rajasekharan, Ranjith; Lau, Desmond W M; Karle, Timothy J; Gibson, Brant C; Tomljenovic-Hanic, Snjezana

    2015-01-01

    The negatively-charged nitrogen vacancy (NV(-)) center in diamond is of great interest for quantum information processing and quantum key distribution applications due to its highly desirable long coherence times at room temperature. One of the challenges for their use in these applications involves the requirement to further optimize the lifetime and emission properties of the centers. Our results demonstrate the reduction of the lifetime of NV(-) centers, and hence an increase in the emission rate, achieved by modifying the refractive index of the environment surrounding the nanodiamond (ND). By coating the NDs in a polymer film, experimental results and numerical calculations show an average of 63% reduction in the lifetime and an average enhancement in the emission rate by a factor of 1.6. This strategy is also applicable for emitters other than diamond color centers where the particle refractive index is greater than the refractive index of the surrounding media. PMID:26109500

  16. Lifetime Reduction and Enhanced Emission of Single Photon Color Centers in Nanodiamond via Surrounding Refractive Index Modification

    PubMed Central

    Khalid, Asma; Chung, Kelvin; Rajasekharan, Ranjith; Lau, Desmond W.M.; Karle, Timothy J.; Gibson, Brant C.; Tomljenovic-Hanic, Snjezana

    2015-01-01

    The negatively-charged nitrogen vacancy (NV?) center in diamond is of great interest for quantum information processing and quantum key distribution applications due to its highly desirable long coherence times at room temperature. One of the challenges for their use in these applications involves the requirement to further optimize the lifetime and emission properties of the centers. Our results demonstrate the reduction of the lifetime of NV? centers, and hence an increase in the emission rate, achieved by modifying the refractive index of the environment surrounding the nanodiamond (ND). By coating the NDs in a polymer film, experimental results and numerical calculations show an average of 63% reduction in the lifetime and an average enhancement in the emission rate by a factor of 1.6. This strategy is also applicable for emitters other than diamond color centers where the particle refractive index is greater than the refractive index of the surrounding media. PMID:26109500

  17. Implementation of transformed lenses in bed of nails reducing refractive index maximum value and sub-unity regions.

    PubMed

    Prado, Daniel R; Osipov, Andrey V; Quevedo-Teruel, Oscar

    2015-03-15

    Transformation optics with quasi-conformal mapping is applied to design a Generalized Maxwell Fish-eye Lens (GMFEL) which can be used as a power splitter. The flattened focal line obtained as a result of the transformation allows the lens to adapt to planar antenna feeding systems. Moreover, sub-unity refraction index regions are reduced because of the space compression effect of the transformation, reducing the negative impact of removing those regions when implementing the lens. A technique to reduce the maximum value of the refractive index is presented to compensate for its increase because of the transformation. Finally, the lens is implemented with the bed of nails technology, employing a commercial dielectric slab to improve the range of the effective refractive index. The lens was simulated with a 3D full-wave simulator to validate the design, obtaining an original and feasible power splitter based on a dielectric lens. PMID:25768148

  18. Interferometric study of electronic changes in the refractive index of a Nd:YAG laser crystal caused by intense pumping

    SciTech Connect

    Antipov, Oleg L; Eremeikin, O N; Savikin, A P [Institute of Applied Physics, Russian Academy of Sciences, Moscow (Russian Federation)

    2003-10-31

    Changes in the refractive index of a Nd:YAG laser crystal caused by intense pumping are measured using a polarisation interferometer. A significant electronic component in the refractive-index changes associated with the excitation of the {sup 4}F{sub 3/2} electronic level of Nd{sup 3+} ions is revealed in the crystal pumped by 808-nm radiation of a pulsed diode array. An appreciable increase in the electronic component of the refractive index, which is caused by the population of the {sup 2}F(2){sub 5/2} high-energy level, is observed in a Nd:YAG crystal additionally pumped by a 266-nm laser beam. Analytic calculations show that the short-wavelength 4f-5d transitions provide a predominant contribution to the polarisability of excited Nd{sup 3+} ions at the 1064.2-nm lasing transition. (active media)

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

    PubMed

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

    2012-04-20

    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

  20. Plasmonic circular resonators for refractive index sensors and filters

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Zhang, Xia; Ren, Xiaomin

    2015-05-01

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

  1. Gradient polymer network liquid crystal with a large refractive index change.

    PubMed

    Ren, Hongwen; Xu, Su; Wu, Shin-Tson

    2012-11-19

    A simple approach for preparing gradient polymer network liquid crystal (PNLC) with a large refractive index change is demonstrated. To control the effective refractive index at a given cell position, we applied a voltage to a homogeneous cell containing LC/diacrylate monomer mixture to generate the desired tilt angle and then stabilize the LC orientation with UV-induced polymer network. By varying the applied voltage along with the cells' movement, a PNLC with a gradient refractive index distribution is obtained. In comparison with conventional approaches using patterned photomask or electrode, our method offers following advantages: large refractive index change, freedom to design specific index profile, and large panel capability. Potential applications include tunable-focus lenses, prism gratings, phase modulators, and other adaptive photonic devices. PMID:23187501

  2. Tapered laser diode with linearly effective-refractive-index variation waveguide

    NASA Astrophysics Data System (ADS)

    Heo, Duchang; Kwak, Yun-Seok; Kim, Tae-kyung; Choi, Young-Wook

    2015-03-01

    We investigated a novel design concept of index-guided tapered LDs with linearly effective-refractive-index variation to make a quality beam in 808 nm for intermediate power LDs between a few decades of mW to ~ W. In this concept, the tapered width at each position in the propagation direction varies linearly depending on change in effective-refractive-index not geometry. We use GaAsP/InGaP/InGaAlP quantum well LD structure of 808 nm and standard LD fabrication processes to test. To design a detail structure, we use the effective-refractive-index method and transfer matrix method. The tapered ridge LD with linear effective-refractive-index variation shows more stable in beam quality but needs more study to optimize the structure.

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

    SciTech Connect

    Chen Jihuan; Zhao Jiarong; Huang Xuguang; Huang Zhenjian

    2010-10-10

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

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

    PubMed Central

    YOUNG, P.A.; CLENDENON, S.G.; BYARS, J.M.; DUNN, K.W.

    2015-01-01

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

  5. Ultrasensitive refractive index sensor based on elliptic microfibers fabricated by CO2 laser

    NASA Astrophysics Data System (ADS)

    Sun, Li-Peng; Li, Jie; Jin, Long; Guan, Bai-Ou

    2014-05-01

    A highly-birefringent elliptic microfiber is fabricated by use of the CO2-laser machining and fusion tapering methods. The fiber ellipse can be well controlled with modification of the CO2 laser output power. Both positive and negative sensitivities are observed for the structure to be used in the refractive index sensing application, in contrast to the previously-reported microfiber devices. Moreover, the maximum obtained sensitivity is as high as 195348nm/RIU (refractive index unit) around refractive index of 1.35887, which is one order of magnitude higher than other microfiber counterparts. The temperature-cross sensitivity of 0.007nm/°C is quite low.

  6. Index of Refraction Measurements Using a Laser Distance Meter

    ERIC Educational Resources Information Center

    Ochoa, Romulo; Fiorillo, Richard; Ochoa, Cris

    2014-01-01

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

  7. Determination of the suitable refractive index of solar cells silicon nitride

    NASA Astrophysics Data System (ADS)

    El Amrani, A.; Bekhtari, A.; El Kechai, A.; Menari, H.; Mahiou, L.; Maoudj, M.; Si-Kaddour, R.

    2014-09-01

    In silicon solar cells studies, the optimal refractive index of plasma- enhanced chemical vapor deposited silicon nitride films is usually determined by an electrical characterization. This technique is done by minority carrier lifetime or surface recombination velocity measurement. We developed in this study a method which encompasses electrical and optical film properties. This method is based on the calculation of the short circuit current densities of multicrystalline silicon solar cells. The optimal refractive index is determined by the maximum short circuit current density. Films with the following refractive indices were studied: 1.9, 2.0, 2.1 and 2.4. The thicknesses are those of an optimal anti-reflection coating (one-quarter wavelength). The optical characterization of these films deposited on multicrystalline silicon wafers and on corning glass gave a minimal weighted reflection for refractive index of 2.0 and a maximum transmission for refractive index of 1.9, respectively. The QSSPC characterization revealed that the film refractive index of 1.9 performed the best passivation quality. Internal quantum efficiencies of simulated multicrystalline silicon solar cells coated with these films were determined by PC1d program simulation. Short-circuit current densities calculated using these experimental and simulated data revealed that the optimal refractive index is 1.9.

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

    SciTech Connect

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

    2013-07-15

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

  9. Improvement in refractive index sensitivity by means of internally curved long period fiber gratings

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    A novel configuration of long period fiber grating (LPFG), based on a specially designed refractive index (RI) profile, was manufactured and studied. The internally manufactured geometric structure is characterized by grating planes tilted at increasing angles, as moving away from the center of symmetry of the structure towards its both edges. This structure reproduces the bending of an optical fiber and improves the RI sensitivity of an LPG to the external surrounding medium. A three-fold enhancement in the RI sensitivity was experimentally proved, thus giving a further contribution towards the development of more sensitive RI sensors based on optical fiber LPGs.

  10. Study of Compact Tunable Filters Using Negative Refractive Index Transmission Lines 

    E-print Network

    Lewis, Brian Patrick

    2011-08-08

    : Electrical Engineering iii iii ABSTRACT Study of Compact Tunable Filters Using Negative Refractive Index Transmission Lines. (May 2011) Brian Patrick Lewis, B.S., Texas A&M University Chair of Advisory Committee: Dr. Kai Chang Today?s...: the insertion losses increased from less than 0.5dB to greater than 3dB, the center frequency shifted 31 3 1 from 2.8 GHz (HFSS) to 2.6 GHz, and the upper rejection band began fading at a frequency about 30-60% higher than the center...

  11. Fast measurement of the refractive-index dispersion of dilute liquid solutions of absorbing molecules

    Microsoft Academic Search

    Elizareth Hernández-Sánchez; Humberto Contreras-Tello; Celia Sánchez-Pérez; Augusto García-Valenzuela

    2009-01-01

    We describe a fast method for measuring the refractive-index dispersion of transparent and absorbing liquid solutions. The method is based on measuring the reflectance spectra of an optical beam of white light in an internal reflection configuration near the critical angle defined by the refractive indices of the incident medium (a glass prism) and that of the solvent, which is

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

    NASA Astrophysics Data System (ADS)

    Luetjen, Christopher; Hallsted, Jonathan; Kleinert, Michaela

    2013-12-01

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

  13. Growth rate, refractive index, and IR reflection spectra of CO2 and N2 cryocrystals

    Microsoft Academic Search

    A. S. Drobyshev; D. N. Garipogly

    1996-01-01

    The results of investigations are presented for the dependence of growth rate, refractive index, and IR reflection spectra of real nitrogen and carbon dioxide cryocrystals on the conditions of their formation (temperature of condensation surface and the gaseous phase pressure, for example). It is found that the growth rate and refractivity of CO2 vary nonlinearly with temperature, which may be

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

    PubMed Central

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

    2008-01-01

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

  15. Measurement of the refractive index of transparent materials using null polarimetry near Brewster's angle

    NASA Astrophysics Data System (ADS)

    Nee, Soe-Mie F.

    1998-10-01

    The nondestructive measurement of refractive index of transmissive materials using null polarimetry is simple, accurate and does not require much on sample preparation. In null polarimetry, the ellipsometric parameter (psi) for reflection from a sample is measured. (psi) for transparent material is defined by tan (psi) equals rp/rs where rp and rs are coefficients of reflection for the p- and s-polarization respectively. By choosing the angle of incidence (Theta) near the Brewster angle, refractive index can be computed from (Theta) and (psi) directly. The only requirement on the sample is that no back surface reflection is allowed to mess up the front surface reflection. Precision in the refractive index is about 0.0004. Spectra of refractive index for quartz are measured and compared with the spectra quoted from existing Handbooks.

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

    PubMed Central

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

    2013-01-01

    We report an easy-to-build, compact, and low-cost optical fiber refractive index sensor. It consists of a single fiber loop whose transmission spectra exhibit a series of notches produced by the resonant coupling between the fundamental mode and the cladding modes in a uniformly bent fiber. The wavelength of the notches, distributed in a wavelength span from 1,400 to 1,700 nm, can be tuned by adjusting the diameter of the fiber loop and are sensitive to refractive index changes of the external medium. Sensitivities of 170 and 800 nm per refractive index unit for water solutions and for the refractive index interval 1.40–1.442, respectively, are demonstrated. We estimate a long range resolution of 3 × 10?4 and a short range resolution of 2 × 10?5 for water solutions. PMID:23979478

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

    Microsoft Academic Search

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

    2009-01-01

    A fiber optic refractive index sensor is tested for continuous monitoring of fluid-fluid and fluid-gas interactions within the frame of laboratory investigations of CO2 storage, monitoring and safety technology research (COSMOS project, \\

  18. Microstrip post production tuning bar error and compact resonators using negative refractive index metamaterials

    E-print Network

    Scher, Aaron David

    2005-08-29

    of these simulations is verified by experimental results. The second topic in this thesis involves the design of compact microwave resonators using the transmission line approach to create negative refractive index metamaterials. A survey of the major developments...

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

    NASA Technical Reports Server (NTRS)

    Lading, Lars; Saffman, Mark; Edwards, Robert

    1996-01-01

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

  20. Shrinkage- and refractive-index shift-corrected volume holograms for optical interconnects

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Heng; Su, Der-Chin; Su, Jung-Chieh

    2002-08-01

    The Bragg mismatching condition for volume holograms occurs because of the changes in the thickness and the refractive index of holographic recording materials during the recording and reconstruction procedures. We propose an improved compensation method to physically correct these effects in the fabrications of volume holograms for optical interconnects. In order to show the validity of this method, Slavich photographic plate VRP-M is used to fabricate optical interconnects. The correction of the Bragg diffraction angle shift of about 2.10deg, which is induced by 6.14% film shrinkage and 0.06 refractive index shift, is successfully demonstrated with the surface-normal configuration. A shrinkage- and refractive-index shift-corrected volume hologram with 23% diffraction efficiency is experimentally confirmed. The methodology proposed is applicable to other phase media when the associated film shrinkage and refractive-index shift data are experimentally determined.

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

    PubMed

    Han, Lu; Zhao, Hongping

    2014-12-29

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

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

    NASA Astrophysics Data System (ADS)

    Rheims, J.; Köser, J.; Wriedt, T.

    1997-06-01

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

  3. Characterization of a Multilayered Negative-Refractive-Index Transmission-Line (NRI-TL) Metamaterial

    Microsoft Academic Search

    A. K. Iyer; G. V. Eleftheriades

    2006-01-01

    This paper presents the characterization of a multilayered volumetric negative-refractive-index transmission-line (NRI-TL) metamaterial. An equivalent circuit model provides expressions for the effective material parameters of the medium and yields its dispersion and transmission properties. These results are presented with supporting finite-element full-wave simulations illustrating the phase-restoration and transmission properties of a volumetric NRI-TL slab lens with refractive index -1 and

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

    Microsoft Academic Search

    Anthony Grbic; George V. Eleftheriades

    2002-01-01

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

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

    Microsoft Academic Search

    Takahiro Numai

    2001-01-01

    A frequency shift Deltaf 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 2Deltaf~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

  6. Refractive Index and Fourier Transform Infrared Spectra of Virgin Coconut Oil and Virgin Olive Oil

    Microsoft Academic Search

    W. Mahmood Mat Yunus; Yap Wing Fen; Lim Mei Yee

    2009-01-01

    This study presents the refractive index and FTIR spectra of virgin coconut oil and virgin olive oil that have been measured in the wavelength range from 491.0-667.8 nm. The measurement of refractive index was carried out using a minimum deviation method while the IR transmission ranging from 600-4000 cm?1 was measured using FTIR spectrometer respectively. The measurements were done at

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

    NASA Astrophysics Data System (ADS)

    Peng, Yu; Li, Wei

    2014-07-01

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

  8. Negative refractive index metamaterials supporting 2-D waves

    Microsoft Academic Search

    Ashwin K. Iyer; George V. Eleftheriades

    2002-01-01

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

  9. Sign Identification of Nonlinear Refractive Index of Colloidal Nanoparticles by Moiré Deflectometry Technique

    NASA Astrophysics Data System (ADS)

    Granmayeh Rad, A.; Madanipour, K.; Koohian, A.; Taheri, N.

    2012-09-01

    In this paper, a visual rapid technique is presented for the sign identification of nonlinear refractive index of colloidal nanoparticles based on non-scanning Moiré deflectometry technique. In this method two lasers are used, one as a pump laser beam which causes thermal nonlinear effects in the sample and the second one is used as a probe beam laser which allows us to monitor these effects by Moiré deflectometry technique. The gradient of the nonlinear refractive index produced by the interaction of the pump laser, generates a cylindrical lens in the sample. The concave and convex lenses are produced as a result of negative and positive nonlinear refractive index respectively. Geometrical and experimental investigations show the Moiré fringes are deflected in two different directions by these lenses. By observing the shape of deflected moiré fringes, we can determine the sign of nonlinear refractive index and there will be no need for calibration or complicated calculations. This technique was applied for identification of nonlinear refractive index of Au and Tio_2 colloidal nanoparticles, under 47 mW second harmonic of Nd:YAG laser illumination. The sign of nonlinear refractive index of colloidal Au and Tio_2 nanoparticles were observed to be negative and positive respectively.

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

    E-print Network

    Koichi Hattori; Kazunori Itakura

    2013-03-08

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

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

    NASA Astrophysics Data System (ADS)

    Hattori, Koichi; Itakura, Kazunori

    2013-07-01

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

  12. Dispersion and distribution of optical index of refraction in ferroelectric relaxor crystal

    NASA Astrophysics Data System (ADS)

    Li, Chunlai

    This thesis deals with the optical properties of relaxor ferroelectrics with nano/micro polar regions, including their optical frequency dispersion near phase transition, thermo-optical properties, and transmission spectrum analysis. The essential objectives of this thesis work are to deepen the understanding on diffuse phase transition of relaxor ferroelectrics and to obtain practical data for potential optical application from technically important ferroelectrics crystals PBN and PZN-PT. Temperature dependent birefringence and optical refractive indices of PBN (Pb1-xBaxNb2O6) crystal (1-x=0.57) were measured in several optical wavelengths (lambda= 694nm, 633nm, 535nm, and 450nm) to understand the optical frequency dependency of ferroelectric phase transitions in relaxor ferroelectric crystals of tungsten bronze structure. Local polarization is verified to be dynamically activated by thermal process and probed effectively by suitable wavelength of light. An optical isotropic point, as a function of temperature and light frequency, is reported at which the crystal's standing birefringence is fully compensated by polarization. A modified single oscillator model is used to calculate the index of refraction in the ferroelectric phase. The deviation temperature from the single oscillator model is reported to be significantly marking the crossover from macroscopic to microscopic polarization. A new parameter, optical Curie temperature region, defined by the temperature difference between the well known Burns temperature and the deviation temperature (from the single oscillator model for index of refraction) is explored for its significance in depolarization behavior of the micro- to nano-polar regions of the ferroelectric relaxor. Temperature dependent optical indices of refraction of PZN-0.12PT (1-x)PbZn 1/3Nb2/3O3-xPbTiO3, x=0.12, were also studied with emphasis on poling effect. The refractive index n3 decreases as a result of [001] poling. Temperature dependent effective energy of dispersion oscillator E0 and dispersion energy Ed were calculated using single oscillator model and found that E0 and Ed increased by 32% and 60% after [001] poling, respectively. Birefringence of poled PZN-0.12PT also was measured with several frequencies and varying temperature. The polarization derived from refractive index and birefringence were consistent with each other. The remnant polarization was increased by approximately 30% as a result of [001] poling. Transmission spectrum of PZN-0.12PT was measured from near UV to IR for both poled sample and unpoled sample. Transmission was improved significantly after poling. By analyzing the transmission spectrum in the visible range, optical band gap and lattice phonon were determined. The existence of hydrogen in PZN-0.12PT single crystal grown by flux method was postulated based on evidence obtained by FTIR. For accurate and fast birefringence measurement, which is of fundamental importance to device design, quality control, and various sensing functions, a two-dimensional birefringence profiling and analysis system was designed and implemented successfully. Jones matrices of two and three 90° domains are derived and conclude that odd number of stacked 90° domains can be treated as a single 90° domain while even number of stacked 90° domains can be treated as two 90° domains. By rotating analyzer method a test experiment using voltage controllable liquid crystal as sample is demonstrated.

  13. TCF-MMF-TCF fiber structure based interferometer for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Fu, Haiwei; Li, Huidong; Shao, Min; Zhao, Na; Liu, Yinggang; Li, Yan; Yan, Xu; Liu, Qinpeng

    2015-06-01

    A liquid refractive index (RI) sensor based on in-fiber Mach-Zehnder interferometer (MZI) by sandwiching multi-mode fiber (MMF) between two short sections of thinned core fiber (TCF) is proposed in this paper. The first section of TCF excites the high-order modes and the second section TCF couples the core mode and high-order modes into lead-out SMF to form intermodal interference. The sensor with MMF length of 20 mm and TCFs length of 1 mm was fabricated. The transmission spectrum variation of the sensor with respect to surrounding refractive index (SRI) has been studied by experiment. The results show that the central wavelength of dips/peaks shifting had a good linearity with SRI. The RI sensitivity of the sensor is 130.00 nm/RIU over the RI range of 1.3333-1.4182. The RI sensitivity increase to 433.60 nm/RIU after etching the MMF cladding of the sensor. The sensor keeps low dependence on temperature before and after etching.

  14. Index of refraction, density, and solubility of ammonium iodide solutions at high pressure.

    PubMed

    Lamelas, F J

    2013-03-01

    An asymmetric moissanite anvil cell is used to study aqueous solutions of ammonium iodide at pressures up to 10 kbar. The index of refraction is measured using the rotating Fabry-Perot technique, with an accuracy of approximately 1%. The mass density and molar volume of the solutions are estimated using the measured index values, and the molar volume is used to predict the pressure dependence of the solubility. The solubility derived from the index of refraction measurements is shown to agree with that which is determined by direct observation of the onset of crystallization. PMID:23409919

  15. Tenfold improved sensitivity using high refractive-index substrates for surface plasmon sensing

    SciTech Connect

    Micheletto, Ruggero [Nanoscience and Technology, International Graduate School of Art and Sciences, Yokohama City University, Seto, Kanazawa-ku, Yokohama 236-0027 (Japan); Department of Electronic Science, Graduate School of Engineering, Kyoto University, Nishigyo-ku, Katsura, 615-8510 Kyoto (Japan); Hamamoto, Katsumi [Department of Electronic Science, Graduate School of Engineering, Kyoto University, Nishigyo-ku, Katsura, 615-8510 Kyoto (Japan); Teramecs Ltd., 97 Higashi Koyanouchi-cho, Takeda, Fushimi-ku, 612-8448 Kyoto (Japan); Fujii, Takashi [Murata Manufactoring Co., Ltd., Higashikotari 1-chome, Nagaokakyo-shi, 617-8555 Kyoto (Japan); Kawakami, Yoichi [Department of Electronic Science, Graduate School of Engineering, Kyoto University, Nishigyo-ku, Katsura, 615-8510 Kyoto (Japan)

    2008-10-27

    Surface plasmon resonance sensors exploit the high sensitivity to local perturbations of plasma waves in a thin metal layer. These devices have a wide range of applications as biomedical, environmental, industrial, and homeland security. We concentrate on the theoretical aspects of the sensing principle. By calculations at various indexes of refraction we proved that using substrate material of higher index, sensitivity and dynamics range improve conspicuously. Finally, we show experimental data taken using a special transparent ceramic material of exceptionally high index of refraction n=2.04. Tests demonstrate sensitivity about one order of magnitude better than those obtained with conventional BK7 glass.

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

    PubMed

    Garg, Ruchi; Thyagarajan, K

    2013-04-01

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

  17. Angular tolerances and trapped internal reflections in wedged high refractive index Brewster's angle plates

    Microsoft Academic Search

    H. N. Rutt

    1997-01-01

    It is well known that the angular alignment tolerance for Brewster's angle plates is not generally strict. It is often not appreciated that for high index plates however wedge tolerances are small. It is shown that in Brewster angle plates of high refractive index materials, small wedge angles in the fabricated plate can cause internal s-plane reflections to become ‘trapped’

  18. Angular tolerances and trapped internal reflections in wedged high refractive index Brewster's angle plates

    Microsoft Academic Search

    H. N. Rutt

    1997-01-01

    It is well known that the angular alignment tolerance for Brewster's angle plates is not generally strict. It is often not appreciated that for high index plates however wedge tolerances are small. It is shown that in Brewster angle plates of high refractive index materials, small wedge angles in the fabricated plate can cause internal s-plane reflections to become `trapped'

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

    ERIC Educational Resources Information Center

    Joshi, Amitabh; Serna, Juan D.

    2012-01-01

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

  20. Zero phase delay in negative-refractive-index photonic crystal superlattices

    E-print Network

    Hone, James

    Zero phase delay in negative-refractive-index photonic crystal superlattices S. Kocaman1 *, M. S4 and C. W. Wong1 * We show that optical beams propagating in path-averaged zero-index photonic crystal superlattices can have zero phase delay. The nanofabricated superlattices consist of alternating

  1. Design of photonic crystal fiber long-period grating refractive index sensor

    NASA Astrophysics Data System (ADS)

    Kanka, Jiri; Zhu, Yinian; He, Zonghu; Du, Henry

    2009-05-01

    Numerical optimization of photonic crystal fiber (PCF) structures for refractive index sensors based on long period gratings inscribed in PCFs has been performed. The optimization procedure employs the Nelder-Mead downhill simplex algorithm. This direct-search method attempts to minimize a scalar-valued nonlinear function of N real variables (called the objective function) using only function values, without any derivative information. An inverse design approach utilizes the objective function constructed using desired sensing characteristics. For the modal analysis of the PCF structure a fully-vectorial solver based on the finite element method is called by the objective function. The dispersion optimization of PCFs is aimed at achieving a high sensitivity of measurement of refractive index of analytes infiltrated into the air holes for the refractive index and probe wavelength ranges of interest. We have restricted our work to the index-guiding solid-core PCF structures with hexagonally arrayed air holes.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  3. Stratospheric aerosol acidity, density, and refractive index deduced from SAGE 2 and NMC temperature data

    NASA Technical Reports Server (NTRS)

    Yue, G. K.; Poole, L. R.; Wang, P.-H.; Chiou, E. W.

    1994-01-01

    Water vapor concentrations obtained by the Stratospheric Aerosol and Gas Experiment 2 (SAGE 2) and collocated temperatures provided by the National Meteorological Center (NMC) from 1986 to 1990 are used to deduce seasonally and zonally averaged acidity, density, and refractive index of stratospheric aerosols. It is found that the weight percentage of sulfuric acid in the aerosols increases from about 60 just above the tropopause to about 86 at 35 km. The density increases from about 1.55 to 1.85 g/cu cm between the same altitude limits. Some seasonal variations of composition and density are evident at high latitudes. The refractive indices at 1.02, 0.694, and 0.532 micrometers increase, respectively, from about 1.425, 1.430, and 1.435 just above the tropopause to about 1.445, 1.455, and 1.458 at altitudes above 27 km, depending on the season and latitude. The aerosol properties presented can be used in models to study the effectiveness of heterogeneous chemistry, the mass loading of stratospheric aerosols, and the extinction and backscatter of aerosols at different wavelengths. Computed aerosol surface areas, rate coefficients for the heterogeneous reaction ClONO2 + H2O yields HOCl + HNO3 and aerosol mass concentrations before and after the Pinatubo eruption in June 1991 are shown as sample applications.

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Tarjányi, N.

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Lee, Ho-Jae; Joo, Ki-Nam

    2014-05-01

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

  7. High sensitivity refractive index sensor based on adiabatic tapered optical fiber deposited with nanofilm by ALD.

    PubMed

    Zhu, Shan; Pang, Fufei; Huang, Sujuan; Zou, Fang; Dong, Yanhua; Wang, Tingyun

    2015-06-01

    Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractive index sensor based on an adiabatic tapered optical fiber. Different thickness of Al2O3 nanofilm is coated around fiber taper precisely and uniformly under different deposition cycles. Attributed to the high refractive index of the Al2O3 nanofilm, an asymmetry Fabry-Perot like interferometer is constructed along the fiber taper. Based on the ray-optic analysis, total internal reflection happens on the nanofilm-surrounding interface. With the ambient refractive index changing, the phase delay induced by the Goos-Hänchen shift is changed. Correspondingly, the transmission resonant spectrum shifts, which can be utilized for realizing high sensitivity sensor. The high sensitivity sensor with 6008 nm/RIU is demonstrated by depositing 3000 layers Al2O3 nanofilm as the ambient refractive index is close to 1.33. This high sensitivity refractive index sensor is expected to have wide applications in biochemical sensors. PMID:26072758

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

    Microsoft Academic Search

    ERNEST K. SMITH; Stanley Weintraub

    1953-01-01

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

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

    Microsoft Academic Search

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

    2005-01-01

    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

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

    PubMed Central

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  12. LETTER TO THE EDITOR: On uniqueness in refractive index optical tomography

    NASA Astrophysics Data System (ADS)

    Khan, Taufiquar; Thomas, Alan; Yoon, Jeong-Rock

    2006-04-01

    In optical tomography, conventionally a constant refractive index assumption is used. The uniqueness and non-uniqueness of the inverse problem for the diffusion approximation to the radiative transport equation has been studied in the past. In this letter, we report the uniqueness and non-uniqueness of the optical tomography inverse problem based on a spatially varying refractive index. We establish criteria for uniqueness applying the well-known results of Sylvester and Uhlmann (1987 Ann. Math. 125 153-69) which has been applied by Arridge and Lionheart (1998 Opt. Lett. 23 882-4) for the constant refractive index case. Our result suggests that if either n, D, or ?a/D is assumed to be known, all parameters (n, D, ?a) can be uniquely determined from the Dirichlet-to-Neumann map.

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  17. Estimation of volcanic ash refractive index from satellite infrared sounder data

    NASA Astrophysics Data System (ADS)

    Ishimoto, H.; Masuda, K.

    2014-12-01

    The properties of volcanic ash clouds (cloud height, optical depth, and effective radius of the particles) are planned to estimate from the data of the next Japanese geostationary meteorological satellite, Himawari 8/9. The volcanic ash algorithms, such as those proposed by NOAA/NESDIS and by EUMETSAT, are based on the infrared absorption properties of the ash particles, and the refractive index of a typical volcanic rock (i.e. andesite) has been used in the forward radiative transfer calculations. Because of a variety of the absorption properties for real volcanic ash particles at infrared wavelengths (9-13 micron), a large retrieval error may occur if the refractive index of the observed ash particles was different from that assumed in the retrieval algorithm. Satellite infrared sounder provides spectral information for the volcanic ash clouds. If we can estimate the refractive index of the ash particles from the infrared sounder data, a dataset of the optical properties for similar rock type of the volcanic ash can be prepared for the ash retrieval algorithms of geostationary/polar-orbiting satellites in advance. Furthermore, the estimated refractive index can be used for a diagnostic and a correction of the ash particle model in the retrieval algorithm within a period of the volcanic activities. In this work, optimal estimation of the volcanic ash parameters was conducted through the radiative transfer calculations for the window channels of the atmospheric infrared sounder (AIRS). The estimated refractive indices are proposed for the volcanic ash particles of some eruption events.

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

    PubMed

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

    2014-11-01

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

  19. On the feasibility of optical-CT imaging in media of different refractive index

    SciTech Connect

    Rankine, Leith [Medical Physics Graduate Program, Duke University, Durham, North Carolina 27710 (United States); Oldham, Mark [Department of Radiation Oncology Physics, Duke University Medical Center, Durham, North Carolina 27710 (United States)

    2013-05-15

    Purpose: Achieving accurate optical-CT 3D dosimetry without the use of viscous refractive index (RI) matching fluids would greatly increase convenience. Methods: Software has been developed to simulate optical-CT 3D dosimetry for a range of scanning configurations including parallel-beam, point, and converging light sources. For each configuration the efficacy of three refractive media was investigated: air, water, a fluid closely matched to PRESAGE{sup Registered-Sign }, and perfect matching (RI = 1.00, 1.33, 1.49, and 1.501 respectively). Reconstructions were performed using both filtered backprojection (FBP) and algebraic reconstruction technique (ART). The efficacy of the three configurations and the two algorithms was evaluated by calculating the usable radius (i.e., the outermost radius where data were accurate to within 2%), and gamma ({Gamma}) analysis. This definition recognizes that for optical-CT imaging, errors are greatest near the edge of the dosimeter, where refraction can be most pronounced. Simulations were performed on three types of dose distribution: uniform, volumetric modulated arc therapy (VMAT), and brachytherapy (Cs-137). Results: For a uniformly irradiated dosimeter the usable radius achieved with filtered backprojection was 68% for water-matching and 31% for dry-scanning in air. Algebraic reconstruction gave usable radii of 99% for both water and air (dry-scanning), indicating greater recovery of useful data for the uniform distribution. FBP and ART performed equally well for a VMAT dose distribution where less dose is delivered near the edge of the dosimeter. In this case, the usable radius was 86% and 53% for scanning in water and air, respectively. For brachytherapy, the usable radius was 99% and 98% for scanning in water and air, respectively using FBP, and a major decrease was seen with ART. Point source geometry provided 1%-2% larger usable radii than parallel geometry. Converging geometry recovered less usable dosimetry data (up to 10% reduced usable radii) than point and parallel geometries. A further disadvantage of converging geometry was an increased requirement on detector size by up to 18 Degree-Sign . Conclusions: For applications where dose information is not required in the periphery of the dosimeter, some dry and low-viscous matching configurations may be feasible. For all three dose distributions (uniform, VMAT, brachytherapy) the point source geometry produced slightly more favorable results (an extra 1%-2% usable radii) than parallel and converging. When dosimetry is required on the periphery, best results were obtained using close refractive matching and ART. A concern for water or dry-scanning is the increase in required detector size, introducing potential cost penalties for manufacturing.

  20. On the feasibility of optical-CT imaging in media of different refractive index

    PubMed Central

    Rankine, Leith; Oldham, Mark

    2013-01-01

    Purpose: Achieving accurate optical-CT 3D dosimetry without the use of viscous refractive index (RI) matching fluids would greatly increase convenience. Methods: Software has been developed to simulate optical-CT 3D dosimetry for a range of scanning configurations including parallel-beam, point, and converging light sources. For each configuration the efficacy of three refractive media was investigated: air, water, a fluid closely matched to PRESAGE®, and perfect matching (RI = 1.00, 1.33, 1.49, and 1.501 respectively). Reconstructions were performed using both filtered backprojection (FBP) and algebraic reconstruction technique (ART). The efficacy of the three configurations and the two algorithms was evaluated by calculating the usable radius (i.e., the outermost radius where data were accurate to within 2%), and gamma (?) analysis. This definition recognizes that for optical-CT imaging, errors are greatest near the edge of the dosimeter, where refraction can be most pronounced. Simulations were performed on three types of dose distribution: uniform, volumetric modulated arc therapy (VMAT), and brachytherapy (Cs-137). Results: For a uniformly irradiated dosimeter the usable radius achieved with filtered backprojection was 68% for water-matching and 31% for dry-scanning in air. Algebraic reconstruction gave usable radii of 99% for both water and air (dry-scanning), indicating greater recovery of useful data for the uniform distribution. FBP and ART performed equally well for a VMAT dose distribution where less dose is delivered near the edge of the dosimeter. In this case, the usable radius was 86% and 53% for scanning in water and air, respectively. For brachytherapy, the usable radius was 99% and 98% for scanning in water and air, respectively using FBP, and a major decrease was seen with ART. Point source geometry provided 1%–2% larger usable radii than parallel geometry. Converging geometry recovered less usable dosimetry data (up to 10% reduced usable radii) than point and parallel geometries. A further disadvantage of converging geometry was an increased requirement on detector size by up to 18°. Conclusions: For applications where dose information is not required in the periphery of the dosimeter, some dry and low-viscous matching configurations may be feasible. For all three dose distributions (uniform, VMAT, brachytherapy) the point source geometry produced slightly more favorable results (an extra 1%–2% usable radii) than parallel and converging. When dosimetry is required on the periphery, best results were obtained using close refractive matching and ART. A concern for water or dry-scanning is the increase in required detector size, introducing potential cost penalties for manufacturing. PMID:23635249

  1. Measurement of resonant and nonresonant induced refractive index changes in Yb-doped fiber grating amplifier.

    PubMed

    Shapira, Y P; Oscar, D; Spektor, B; Smulakovsky, V; Horowitz, M

    2015-02-15

    We have measured the refractive index change (RIC) induced in a fiber Bragg grating (FBG) written in a Yb-doped fiber amplifier (YB-FBG) because of the amplifier pumping. The measurement was performed by exploiting the high sensitivity of the YD-FBG transmission to the RIC. We have separated between electronic and thermal contributions to the RIC based on the difference between the time-scales of the two effects. Because of high UV-induced loss in FBGs, the thermal contribution to the RIC is increased, in comparison with previously published work, where no grating was written in the fiber amplifier. The measurement method allows us to find the sign of each contribution to the RIC, and it requires only a few centimeters of fiber. Optimal pumping scheme for reducing the RIC in a YB-FBG is studied. PMID:25680141

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Grbic, Anthony; Eleftheriades, George V.

    2002-11-01

    A composite medium consisting of an array of fine wires and split-ring resonators has been previously used to experimentally verify a negative index of refraction. We present a negative refractive index (NRI) metamaterial that goes beyond the original split-ring resonator/wire medium and is capable of supporting a backward cone of radiation. We report experimental results at microwave frequencies that demonstrate backward-wave radiation from a NRI metamaterial—a characteristic analogous to reversed Cherenkov radiation. The conception of this metamaterial is based on a fresh perspective regarding the operation of NRI metamaterials.

  4. Equivalent lenses of supersonic seeker's outflow refractive index field obtained by simulation and experiment

    NASA Astrophysics Data System (ADS)

    Wei, Qun; Jia, Hongguang; Xuan, Ming

    2008-12-01

    In order to decrease the aerodynamic drag of supersonic image guide missile and design a non-spherical dome, the outflow field of the missile's dome is simulated using FLUENT. Based on the simulated results, the accurate density field of the outflow field at all kinds of flight conditions is obtained, and then the refractive index field of the outflow field is gotten according to the Gladstone-Dale law. The results show that the shock wave induces the heterogeneity of the refractive index field and the turbulent causes distortion. The outflow field is divided into several zones which are taken as equivalent lenses for aberration analysis.

  5. High Performance Optical Coatings Utilizing Tailored Refractive Index Nanoporous Thin Films

    NASA Astrophysics Data System (ADS)

    Poxson, David J.

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  7. Measurement method of the refractive index of biotissue by total internal reflection

    NASA Astrophysics Data System (ADS)

    Li, Hui; Xie, Shusen

    1996-04-01

    A simple method based on total internal reflection is presented for measuring the refractive index of biological tissue. A narrow laser beam and a semicylindrical lens in contact with a tissue specimen are used in the experimental apparatus. The dependence of the internal reflectivity on the angle of incidence is measured to determine the critical angle and therefore the refractive index of tissue. The experimental results for several tissue samples show that the method is reliable and useful for studying tissue optics. The principal advantages of the method are its elimination of scattering effects, suitability to a small in vitro sample, and excellent accuracy.

  8. X-ray tomography using the full complex index of refraction.

    PubMed

    Nielsen, M S; Lauridsen, T; Thomsen, M; Jensen, T H; Bech, M; Christensen, L B; Olsen, E V; Hviid, M; Feidenhans'l, R; Pfeiffer, F

    2012-10-01

    We report on x-ray tomography using the full complex index of refraction recorded with a grating-based x-ray phase-contrast setup. Combining simultaneous absorption and phase-contrast information, the distribution of the full complex index of refraction is determined and depicted in a bivariate graph. A simple multivariable threshold segmentation can be applied offering higher accuracy than with a single-variable threshold segmentation as well as new possibilities for the partial volume analysis and edge detection. It is particularly beneficial for low-contrast systems. In this paper, this concept is demonstrated by experimental results. PMID:22964788

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

    NASA Astrophysics Data System (ADS)

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

    2003-02-01

    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 ?m 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 calculate the QPM wavelengths for an optical parametric oscillator (OPO) based on periodically poled stoichiometric LiTaO3 pumped at 1064 nm. The measured wavelengths of the OPO were in good agreement with our predictions.

  10. High-speed light modulation using complex refractive-index changes of electro-optic polymers

    NASA Astrophysics Data System (ADS)

    Harada, Kenji; Munakata, Katsuhiro; Itoh, Masahide; Yatagai, Toyohiko; Honda, Yutaka; Umegaki, Shinsuke

    2000-12-01

    We propose a promising type of light modulator using complex refractive-index changes of electro-optic polymers in the wavelength region of absorption. The material used in this study is a high-glass-transition-temperature active-polyimide thin film. The wavelength dependence of electrically induced complex refractive-index changes and the modulation efficiency are evaluated. A modulation efficiency of 33.8% has been realized with 141 V rms applied potential at a wavelength of 633 nm. Very fast modulation at over 25 MHz has been demonstrated.

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

    SciTech Connect

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

    2009-05-21

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

  12. Refractive index distribution measurements by means of spectrally-resolved white-light interferometry

    NASA Astrophysics Data System (ADS)

    Guerrero, A. L.; Sáinz, C.; Perrin, H.; Castell, R.; Calatroni, J.

    1992-12-01

    A new procedure to measure the spatial distribution of the refractive index in transparent media is presented. It is based on the spectral analysis of optical interferograms obtained from a wide, continuous-spectrum light source. The method yields fairly high precision (up to 10 -8) in the measurements of local values of differential refractive index, ?n ( ?n= n- nref), along a line in the sample. By means of a CCD TV-camera linked to a microcomputer, fast recording and automatic data processing are achieved. As an application, we present an experimental study of a thermal gradient in a liquid sample.

  13. Index-matched IWKB method for the measurement of spatially varying refractive index profiles within thin-film photovoltaics.

    PubMed

    Pang, Y T; Bossart, M; Eisaman, M D

    2014-01-13

    In many thin-film photovoltaic devices, the photoactive layer has a spatially varying refractive index in the substrate-normal direction, but measurement of this variation with high spatial resolution is difficult due to the thinness of these layers (typically 200 nm for organic photovoltaics). We demonstrate a new method for reconstructing the depth-dependent refractive-index profile with high spatial resolution (~10 nm at a wavelength of 500 nm) in thin (200 nm) photoactive layers by depositing a relatively thick index-matched layer (1-10 ?m) adjacent to the photoactive layer and applying the Inverse Wentzel-Kramers-Brillouin (IWKB) method. This novel technique, which we refer to as index-matched IWKB (IM-IWKB), is applicable to any thin film, including the photoactive layers of a broad range of thin-film photovoltaics. PMID:24921995

  14. A single-image method for x-ray refractive index CT.

    PubMed

    Mittone, A; Gasilov, S; Brun, E; Bravin, A; Coan, P

    2015-05-01

    X-ray refraction-based computer tomography imaging is a well-established method for nondestructive investigations of various objects. In order to perform the 3D reconstruction of the index of refraction, two or more raw computed tomography phase-contrast images are usually acquired and combined to retrieve the refraction map (i.e. differential phase) signal within the sample. We suggest an approximate method to extract the refraction signal, which uses a single raw phase-contrast image. This method, here applied to analyzer-based phase-contrast imaging, is employed to retrieve the index of refraction map of a biological sample. The achieved accuracy in distinguishing the different tissues is comparable with the non-approximated approach. The suggested procedure can be used for precise refraction computer tomography with the advantage of a reduction of at least a factor of two of both the acquisition time and the dose delivered to the sample with respect to any of the other algorithms in the literature. PMID:25856228

  15. Absolute refractive index measurement method over a broad wavelength region based on white-light interferometry.

    PubMed

    Kim, Seung Hwan; Lee, Seoung Hun; Lim, Jae In; Kim, Kyong Hon

    2010-02-10

    We report a simple method of measuring the absolute values of the phase refractive index of an optical material of a flat plate shape over a wide spectral range at a single measurement run. A white-light interferometric technique with angle rotation of the optical plate sample located in one of the interferometer arms was used in this method. The validity of this method was proved by measuring the absolute phase refractive indices of flat plate samples of fused silica and BK7, and by comparing them with calculated values from their well-known Sellmeier dispersion formulas. The accuracy of this refractive index measurement method was within 0.002, which can be further improved by enhancing the angle measurement accuracy of the angle rotating stage used in this method. PMID:20154761

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  17. Generation of J0-Bessel-Gauss Beam by an heterogeneous refractive index map

    E-print Network

    Alerigi, Damian P San Roman; Benslimane, Ahmed; Zhang, Yaping; Alsunaidi, Mohammad; Ooi, Boon S; 10.1364/JOSAA.29.001252

    2012-01-01

    In this paper, we present the theoretical studies of a refractive index map to implement a Gauss to J0-Bessel-Gauss convertor. We theoretically demonstrate the viability of such device by solving the inverse electromagnetic problem. The computed conversion e?ficiency is 90%. The theoretical results, obtained from the beam conversion efi?ciency, self-regeneration, and propagation through an opaque obstruction; demonstrate that a 2D graded index map of the refractive index can be used to transform a Gauss beam into a J0-Bessel-Gauss beam. To the best of our knowledge, this is the ?rst demonstration of such beam transformation by means of a 2D index-mapping which is fully integrable in silicon photonics based planar lightwave circuits (PLC). The concept device is signi?cant for the eventual development of a new array of technologies, such as micro optical tweezers, optical traps, beam reshaping and non-linear beam diode lasers.

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

    Microsoft Academic Search

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

    2011-01-01

    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

  19. Nondestructive determination of refractive index profile of an optical fiber: backward light scattering method.

    PubMed

    Saekeang, C; Chu, P L

    1979-04-01

    A new nondestructive technique is presented for determining the refractive index profile of an optical fiber from its backscattered pattern arising from a normally incident laser beam to the fiber axis. The proposed method requires no sample preparation or index matching liquid. The principle of the method is to construct a deflection function from the measured pattern. The index profile can then be determined by the inversion of an Abel integral equation. Good agreement is obtained between the index profile determined by this technique and that measured by the near-field scanning technique. PMID:20208886

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

    NASA Astrophysics Data System (ADS)

    Zhang, Hongjun

    2012-10-01

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

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

    E-print Network

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

    2007-04-27

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

  2. 2746 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 10, OCTOBER 2007 A Multilayer Negative-Refractive-Index

    E-print Network

    Iyer, Ashwin K.

    capacitors and meandered inductors designed to exhibit NRI properties at X-band (8­12 GHz). The volumetric Negative-Refractive-Index Transmission-Line (NRI-TL) Metamaterial Free-Space Lens at X-Band Ashwin K. Iyer-refractive-index (NRI) transmission-line (TL) metamaterial lens is described that employs fully printed interdigitated

  3. Positive identification of lithographic photoresists using real-time index of refraction monitoring for reduced cost of ownership

    Microsoft Academic Search

    Ron Jee; Susanne Pepper; David Stedman

    2009-01-01

    This study involved installation of a real-time refractive index monitoring system into a simulated photoresist feed line as would be used for delivery to a lithography tool. The goal was to determine whether this refractive index technology could be used to differentiate among all possible photoresists that could potentially be delivered to a lithography tool and resolve each one, separate

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

    Microsoft Academic Search

    S. G. Menefee; O. R. Overman

    1939-01-01

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

  5. Mode conversion and radiation loss caused by refractive-index fluctuations in an asymmetric slab waveguide

    Microsoft Academic Search

    M. Imai; S. Miyanaga; T. Asakura

    1977-01-01

    The purpose of this paper is to show how much power is converted from an incident TE0mode to other guided and radiation modes due to random fluctuations of the refractive index in the core region of an asymmetric slab waveguide. Power conversion is calculated by using a perturbation technique with the assumption that the perturbed field can be expanded in

  6. Measurement of high order Kerr refractive index of major air components

    E-print Network

    Boyer, Edmond

    of self-focusing laser pulses," Phys. Rev. A 68, 015801 (2003). 4. R. Nuter and L. Berg´e, "Pulse chirping.5400) Plasmas; (190.7110) Ultrafast nonlinear optics; (260.5950) Self-focusing References and links 1. A nonlinear refractive index of N2, O2, and Ar at room temperature for a 90 fs and 800 nm laser pulse

  7. Refractive index and thickness determination of thin-films using Lloyd’s interferometer

    Microsoft Academic Search

    A. A. Hamza; M. A. Mabrouk; W. A. Ramadan; A. M. Emara

    2003-01-01

    Determination of the refractive index and the thickness of thin-films using light interference have been presented. This has been done, for the first time, with the use of Lloyd’s interferometer. The mean idea is based on using the sample in two different positions in the same interferometer. The method has been applied for four different samples with different thickness. The

  8. Refractive index and thickness determination of thin-films using Lloyd's interferometer

    Microsoft Academic Search

    A. A. Hamza; M. A. Mabrouk; W. A. Ramadan; A. M. Emara

    2003-01-01

    Determination of the refractive index and the thickness of thin-films using light interference have been presented. This has been done, for the first time, with the use of Lloyd's interferometer. The mean idea is based on using the sample in two different positions in the same interferometer. The method has been applied for four different samples with different thickness. The

  9. Numerical investigation of negative refractive index metamaterials at infrared and optical frequencies

    Microsoft Academic Search

    Nicolae C. Panoiu; Richard M. Osgood

    2003-01-01

    An analysis of the transmission properties of a slab of metallic split-ring resonators at near infrared and optical frequencies is presented. We focus on the influence of the parameters characterizing the intrinsic frequency dispersion of the metallic rings on the physical properties of recently introduced materials that exhibit a negative refractive index. It is demonstrated that, when a mesh of

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

    Microsoft Academic Search

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

    1999-01-01

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

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

    E-print Network

    Cummer, Steven A.

    Wave fields measured inside a negative refractive index metamaterial Steven A. Cummera) and Bogdan. Such a measurement would be experimental confirmation of the fundamental physics of wave fields in a NIM. But beyond measurements of wave fields inside a NIM metamaterial that show directly that the phase velocity inside the NIM

  12. Dispersion analysis of a microstrip-based negative refractive index periodic structure

    Microsoft Academic Search

    Anthony Grbic; George V. Eleftheriades

    2003-01-01

    We present the complete band structure of a negative refractive index metamaterial based on the concept of dual transmission lines. The metamaterial is a two-dimensional (2-D) microstrip periodic structure that has cell dimensions much smaller than the wavelength of operation. It can therefore be considered as an effective medium. First, the dispersion characteristics of the metamaterial are explained by way

  13. Study on the maximum effective refractive index of single interface surface plasmon-polariton waveguide

    Microsoft Academic Search

    Ruijian Rao; Tiantong Tang

    2010-01-01

    The maximum effective refractive index (ERI) and its corresponding material match relationship of planar single interface SPP waveguide are theoretically analyzed and their approximate analytical equations are deduced, taking the loss factor of the metal in consideration. When the match relationship between the metal and insulator permittivity is satisfied, the SPP waveguide is on resonant state and the maximum ERI

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  15. Optical fiber refractive index sensor with reduced thermal sensitivity based on Superimposed Long-Period Gratings

    NASA Astrophysics Data System (ADS)

    Silva, G. E.; Caldas, P.; Santos, J. C.; Santos, J. L.

    2014-05-01

    In this paper, we report the development of a reduced temperature sensitivity optical fiber sensor for refractive index measurement based on Superimposed Long-Period Gratings (SLPG) inscribed by the electric arc technique in standard fiber. The reduced sensitivity to temperature is achieved by calculation of the difference between resonance wavelengths of two guided cladding modes.

  16. Refractive Index Sensing in an All-Solid Twin-Core Photonic Bandgap Fiber

    Microsoft Academic Search

    Wu Yuan; Graham E. Town; Ole Bang

    2010-01-01

    We describe a highly sensitive refractive index sensor based on a twin-core coupler in an all-solid photonic bandgap guiding optical fiber. A single hole acts as a microfluidic channel for the analyte, which modifies the coupling between the cores, and avoids the need for selective filling. By operating in the bandgap guiding regime the proposed sensor is capable of measuring

  17. Ultrasensitive refractive index sensor based on twin-core photonic bandgap fibers

    Microsoft Academic Search

    Wu Yuan; Graham E. Town; Ole Bang

    2009-01-01

    We have theoretically investigated twin-core all-solid photonic bandgap fibers (PBGFs) for evanescent wave sensing of refractive index within one single microfluidic analyte channel centered between the two cores. The sensor can achieve ultrahigh sensitivity by detecting the change in transmission. We find novel features in the sensing characteristics: the sensitivity is higher at the short wavelength edge of a bandgap

  18. Determination of refractive index of printed and unprinted paper using spectroscopic ellipsometry

    Microsoft Academic Search

    J. W. P. Bakker; G. Bryntse; H. Arwin

    2004-01-01

    An attempt is made to address the basic physical properties of printed and unprinted paper surfaces by using spectroscopic ellipsometry in the range 300–900 nm to determine the effective complex-valued refractive index ?N?. Some simulations to address the effect of structural properties have also been done and a qualitative comparison with some other methods, in particular Brewster angle measurements, has

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

    E-print Network

    Jonghwa Shin; Jung-Tsung Shen; Shanhui Fan

    2008-04-14

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

  20. Modification of thermal radiation by periodical structures containing negative refractive index metamaterials

    Microsoft Academic Search

    Milan Maksimovi?; Zoran Jakši?

    2005-01-01

    We investigated thermal radiation power spectrum in 1D ordered structures containing negative refractive index materials. We utilized an approach based on the Kirchoff's second law and applied the transfer matrix method to calculate emittance and to obtain the power spectrum of the multilayer. We analyzed both on-axis and off-axis radiation.

  1. Depth-resolved nanostructure and refractive index of borosilicate glass doped with Ag nanocrystals

    E-print Network

    Polman, Albert

    Depth-resolved nanostructure and refractive index of borosilicate glass doped with Ag nanocrystals Available online 20 December 2005 Abstract We present an investigation of the Ag-nanocrystal depth profile, XE-AES, and transmission and reflection spectroscopy, we show unambiguously that the Ag nanocrystals

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

    E-print Network

    2007-01-01

    with adsorbent material deposited by Sol­gel tech- nique to make it a sensor of chemicals that get adsorbed is immersed, to a high degree of precision and over a wide range of refractive index. The slope of sensor as highly sensitive RI sensing devices. Tapering of fiber and stripping of the fiber cladding have been used

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

    Microsoft Academic Search

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

    2009-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    E-print Network

    Nemat-Nasser, Sia

    138 Composites with Negative Refractive Index, Thermal, Self-healing and Self-sensing Functionality electromagnetic, self-healing, thermal management, and self-sensing properties, i.e., a truly multifunctional electric inductance and capacitance. The self-healing is achieved via Diels-Alder reaction in a newly

  6. Numerical analysis of refractive index sensitivity of long-period gratings in photonic crystal fiber

    Microsoft Academic Search

    Yinian Zhu; Zonghu He; Ji?í Ka?ka; Henry Du

    2008-01-01

    The modal coupling properties and resonance spectral response of long-period gratings (LPGs) in index-guiding photonic crystal fiber (PCF) are numerically investigated with respect to its sensitivity to changes in the index of refraction of the measurand in the PCF air channels using a full-vectorial mode solver combined with frequency-domain method. We show that the shift of wavelength resonance of a

  7. Dynamics of refractive-index changes and two-beam coupling in resonant media

    Microsoft Academic Search

    R. Saxena; I. McMichael; P. Yeh

    1990-01-01

    The dynamics of light-induced change in the refractive index of a resonant medium are examined. For illumination with weak fields, the two relevant relaxation times are T1, the population lifetime and T2, the dipole-dephasing time. The response time of the index change is determined by the slower relaxation time of the medium which is usually the time T1 taken by

  8. Constant Refractive Index Multi-Core Fiber Laser

    SciTech Connect

    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

    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.

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

    PubMed

    Hori, Yasuaki; Hirai, Akiko; Minoshima, Kaoru

    2014-05-01

    A prism-pair interferometer for a spectrum lamp was developed for precise measurement of the refractive index of a prism of optical glass. Previously we reported the prism-pair interferometer with a He-Ne laser light source, resulting in a measurement uncertainty of 1.1×10??. However, most of the refractive-index values managed by optical glass manufacturers are conventionally measured with spectrum lamps. We have optimized the prism-pair interferometer for spectrum lamps and implemented a signal-processing technique from Fourier-transform spectroscopy. When the refractive index is measured, the wavelength of the spectrum lamp is simultaneously calibrated by part of the interferometer, so that the resulting refractive index is traceable to a national standard of length. The combined standard uncertainty for a refractive index measured with the e-line (546 nm) of a Hg lamp is 6.9×10??. PMID:24921862

  10. Dispersion of the refractive index of epitaxial Pb{sub 1-x}Eu{sub x}Te (0 {<=} x {<=} 1) alloy layers below the absorption edge

    SciTech Connect

    Pashkeev, D. A., E-mail: pashkeev@sci.lebedev.ru; Selivanov, Yu. G.; Chizhevskii, E. G. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Stavrovskii, D. B. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Zasavitskiy, I. I. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2011-08-15

    The transmittance spectra of epitaxial Pb{sub 1-x}Eu{sub x}Te (0 {<=}x {<=} 0.1) alloy layers are exploited to study the dispersion of their refractive index in the spectral range from 650 to 8000 cm{sup -1} (below the absorption edge). The refractive index and the position of the absorption edge as functions of the composition parameter of the alloys are determined at two temperatures, 80 and 295 K. The refractive index is calculated in the context of the classic wave concepts of propagation of electromagnetic radiation. The experimentally determined dispersion dependences are described by the empiric Sellmeier expression of the second order. From analysis of the transmittance of the layers, it follows that the band gap of the epitaxial Pb{sub 1-x}Eu{sub x}Te alloys increases with increasing temperature at x < 0.5 and decreases at x > 0.5.

  11. Index of refraction versus oxygen partial pressure for tantalum oxide and silicon dioxide films produced by ion beam deposition

    SciTech Connect

    Goward, W.D.; Petersen, H.E.; Dijaili, S.P.; Walker, J.D.

    1998-04-30

    Tantalum oxide and silicon oxide films were made using an ion beam sputtering system. It was found that even though these films were deposited from oxide targets, additions of oxygen were necessary to achieve stoichiometry and hence index of refraction. It was observed that the tantalum oxide target changed color from white to gray, indicating that the oxygen was being depleted from the target. The addition of oxygen to the chamber during deposition replenished the target and improved film stoichiometry. The deposition rate decreased with increasing oxygen partial pressure. It was experimentally determined that by varying the oxygen partial pressure and keeping all other variables fixed, the index of refraction of the film changed in a predictable manner. That is, as the oxygen partial pressure was increased, the index decreased rapidly initially and then reached a saturation point where it stayed fixed with oxygen content. With this data a coating process can be set up using the minimum amount of oxygen (thus increasing filament lifetime) to produce a fully stoichiometric film that has a fixed index. This paper will present the details of these observations and results.

  12. Microscopic theory of gain, absorption, and refractive index in semiconductor laser materials-influence of conduction-band nonparabolicity and Coulomb-induced intersubband coupling

    Microsoft Academic Search

    J. Hader; J. V. Moloney; S. W. Koch

    1999-01-01

    The influence of the conduction-band nonparabolicity and Coulomb coupling between different electronic subbands and different hole subbands on gain, absorption, and refractive index in semiconductor heterostructures is investigated. We implement these features into a fully microscopic approach. At low carrier densities, the nonparabolicity leads to a steeper increase of the absorption for increasing transition energy. In this regime, the Coulomb

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  14. Simultaneous refractive index and thickness measurements of bio tissue by optical coherence tomography.

    PubMed

    Wang, Xinyu; Zhang, Chunping; Zhang, Lianshun; Xue, Lingling; Tian, Jianguo

    2002-10-01

    This paper presents two techniques based on optical coherence tomography, the "focus tracking method" and the "optical path shifting method," for determining refractive index and thickness simultaneously, which are especially useful for bio tissues. From comparison of these two methods, it was found that the focus tracking method is suitable for in vivo measurement, but does not have high precision. The optical path shifting method is limited to in vitro measurement, but has high precision. Using the optical path shifting method, the refractive indices of cucumber were measured at the wavelength of 850 and 1300 nm. PMID:12421131

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

    E-print Network

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

    2005-06-27

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

  16. Fiber-optic refractive index sensor based on surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Hlubina, Petr; Ciprian, Dalibor; Kadulova, Miroslava

    2015-01-01

    A fiber-optic refractive index sensor based on surface plasmon resonance (SPR) in a thin metal film deposited on an unclad core of a multimode fiber is presented. The sensing element of the SPR fiber-optic sensor is a bare core of a step-index optical fiber made of fused silica with a deposited gold film. First, a model of the SPR fiber-optic sensor based on the theory of attenuated total internal reflection is presented. The analysis is carried out in the frame of optics of multilayered media. The sensing scheme uses a wavelength interrogation method and the calculations are performed over a broad spectral range. Second, in a practical realization of the sensor with a double-sided sputtered gold film, a reflection-based sensing scheme to measure the refractive indices of liquids is considered. The refractive index of a liquid is sensed by measuring the position of the dip in the reflected spectral intensity distribution. As an example, the aqueous solutions of ethanol with refractive indices in a range from 1.333 to 1.364 are measured.

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

    PubMed Central

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

    2010-01-01

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

  18. Refractive-index changes caused by proton radiation in silicate optical glasses.

    PubMed

    Gusarov, Andrei I; Doyle, Dominic; Hermanne, Alex; Berghmans, Francis; Fruit, Michel; Ulbrich, Gerd; Blondel, Michel

    2002-02-01

    We have studied experimentally, by using a differential interferometric technique, the effect of proton radiation on the refractive index of commercial (Schott) silicate crown glasses, BK7 and LaK9, and their radiation-resistant counterparts. The strongest effect was observed for the radiation-hard lanthanum crown LaK9G15: At a 0.65-Mrad dose the index change was approximately 3 x 10(-5). Radiation-hard glasses are used in optical systems operating in radiation environments because they prevent spectral transmission degradation in the visible. However, such glasses are not protected against radiation-induced refractive-index perturbations, and a diffraction-limited optical system based on such glasses may fail owing to radiation-induced aberrations. PMID:11993913

  19. Refractive index sensor based on stress-induced long period grating

    NASA Astrophysics Data System (ADS)

    Lin, Guei-Ru; Chang, Hung-Ying; Fu, Ming-Yue; Sheng, Hao-Jan; Liu, Wen-Fung

    2014-09-01

    We proposed a novel refractive index sensor based on a side-polishing fiber to be cascaded with a stress-induced long period fiber grating (LPG), which is created by applying a force to a V-grooved plate on the single mode fiber with micro-bending deformation. When the refractive index (RI) surrounding the side-polishing surface is changed, the LPG-induced cladding mode light could be coupled back to the core mode, so that it will result in the magnitude variation of LPG loss-peak. This property of index sensing based on the stress-induced LPG by monitoring the power-level change may be exploited in chemical sensing and environmental monitoring applications.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  2. Dependence of refractive index on hydrogen concentration in proton exchanged LiNbO sub 3

    SciTech Connect

    Howerton, M.M.; Skeath, P.R. (Sachs Freemen Associates, Landover, MD (US)); Burns, W.K.; Greenblatt, A.S. (Naval Research Lab., Washington, DC (US))

    1991-02-01

    This paper reports that the nonlinear relationship between refractive index and hydrogen concentration has been experimentally determined for proton exchanged LiNbO{sub 3}, incorporating the effects of partial and full annealing. Complete annealing results in low-loss waveguides in the alpha phase with small surface index changes ({le}0.02). The anneal conditions needed to reach the alpha phase can be estimated using the measured temperature dependence of the anneal diffusion coefficient. A model is presented which attributes the index change in the alpha base to the addition of hydrogen and the loss of lithium, which is consistent with experimental results.

  3. Thermal refractive index coefficients of nonlinear optical crystal CsB3O5.

    PubMed

    Zhang, Guochun; Liu, Shanshan; Huang, Lingxiong; Zhang, Ge; Wu, Yicheng

    2013-05-15

    The principal refractive indices of crystal CsB3O5 (CBO) at the wavelengths of 0.266, 0.355, 0.532, 0.473, 0.633, 1.064, and 1.338 ?m are accurately measured by using the autocollimation method within the temperature range from 40°C to 190°C. We derive and report equations of thermal refractive index coefficients as a function of wavelength that could be used to calculate the principal thermal refractive indices at different wavelengths. Sellmeier equations at different temperatures were derived and used to calculate the phase-matching angles for the third-harmonic generation and the fourth-harmonic generation of CBO crystal at different temperatures. PMID:23938880

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

    PubMed Central

    BESSELING, TH; JOSE, J; BLAADEREN, A VAN

    2015-01-01

    Accurate distance measurement in 3D confocal microscopy is important for quantitative analysis, volume visualization and image restoration. However, axial distances can be distorted by both the point spread function (PSF) and by a refractive-index mismatch between the sample and immersion liquid, which are difficult to separate. Additionally, accurate calibration of the axial distances in confocal microscopy remains cumbersome, although several high-end methods exist. In this paper we present two methods to calibrate axial distances in 3D confocal microscopy that are both accurate and easily implemented. With these methods, we measured axial scaling factors as a function of refractive-index mismatch for high-aperture confocal microscopy imaging. We found that our scaling factors are almost completely linearly dependent on refractive index and that they were in good agreement with theoretical predictions that take the full vectorial properties of light into account. There was however a strong deviation with the theoretical predictions using (high-angle) geometrical optics, which predict much lower scaling factors. As an illustration, we measured the PSF of a correctly calibrated point-scanning confocal microscope and showed that a nearly index-matched, micron-sized spherical object is still significantly elongated due to this PSF, which signifies that care has to be taken when determining axial calibration or axial scaling using such particles. PMID:25444358

  5. Optical band gap and refractive index dispersion parameters of As x Se70Te30- x (0? x?30 at.%) amorphous films

    NASA Astrophysics Data System (ADS)

    Aly, Kamal A.

    2010-06-01

    Amorphous As x Se70Te30- x thin films with (0? x?30 at.%) were deposited onto glass substrates by using thermal evaporation method. The transmission spectra T( ?) of the films at normal incidence were measured in the wavelength range 400-2500 nm. A straightforward analysis proposed by Swanepoel based on the use of the maxima and minima of the interference fringes has been used to drive the film thickness, d, the complex index of refraction, n, and the extinction coefficient, k. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model (WDD). Increasing As content is found to affect the refractive index and the extinction coefficient of the As x Se70Te30- x films. With increasing As content the optical band gap increases while the refractive index decreases. The optical absorption is due to allowed indirect transition. The chemical bond approach has been applied successfully to interpret the increase of the optical gap with increasing As content.

  6. Block copolymer assisted refractive index engineering of metal oxides for applications in optical sensing

    NASA Astrophysics Data System (ADS)

    Poole, Zsolt L.; Ohodnicki, Paul; Buric, Michael; Yan, Aidong; Riyadh, Shaymaa; Lin, Yuankun; Chen, Kevin P.

    2014-09-01

    We demonstrate that the refractive indices of important functional metal oxides (TiO2, SnO2, and ZnO) can be engineered "at will" for applications in photonics engineering. The tailoring of the refractive indices is accomplished by 3D nanostructuring in the sub-wavelength regime (50nm or less) using the method of block-copolymer templating combined with a low cost solution processing approach. Using this method, the index of refraction of the demonstrated metal oxides and their doped variants can be engineered to be as low as 1.25. We will present both numerical simulations and experimental data demonstrating the unrestricted integration of functional metal oxides with a D-shaped optical fiber for applications in chemical and biological sensing. Using the developed refractive index engineering scheme, we introduce a novel hydrogen sensor by integrating a palladium doped TiO2 nanomaterial with D-shaped optical fiber and provide sensor characterization up to 700°C for applications in the energy sector.

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

    NASA Astrophysics Data System (ADS)

    Leviton, Douglas B.; Frey, Bradley J.

    2013-09-01

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

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

    SciTech Connect

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

    1993-06-01

    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.

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

    SciTech Connect

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

    2010-08-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

    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 As 100-xSe x (x=40÷98) and As 40Se 60:Sn y (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 As 60Se 40 and As 50Se 50, which exhibit big modifications of the refractive index ((?n/n)=0.394).

  11. Interferometric fiber sensor using exposed core microstructured optical fiber for refractive index based biochemical sensing

    NASA Astrophysics Data System (ADS)

    Nguyen, Linh Viet; Warren-Smith, Stephen C.; Cooper, Alan; Monro, Tanya M.

    2014-05-01

    We proposed and experimentally demonstrated an in-fiber interferometric-type sensor by splicing an exposed core microstructured optical fiber (ECF) with lead-in and lead-out single mode fibers (SMFs) for refractive index-based biochemical sensing applications. Due to the multimode characteristic of the ECF, several modes can be excited at the lead-in splicing point and, after propagating through the ECF section, arrive at the lead-out splicing point with different phases forming a multi-arm interference pattern in the transmission spectrum of the device. Two dominant modes were found be consistently excited by maximizing the butt coupling between ECF and SMFs. The interference fringes shifts differently upon applying liquids of different refractive index on the exposed side of the ECF.

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. Possible effects of clear-air refractive-index perturbations on SAR images.

    SciTech Connect

    Dickey, Fred McCartney; Muschinski, Andreas (University of Massachusetts, Amherst, MA); Doerry, Armin Walter

    2005-03-01

    Airborne synthetic aperture radar (SAR) imaging systems have reached a degree of accuracy and sophistication that requires the validity of the free-space approximation for radio-wave propagation to be questioned. Based on the thin-lens approximation, a closed-form model for the focal length of a gravity wave-modulated refractive-index interface in the lower troposphere is developed. The model corroborates the suggestion that mesoscale, quasi-deterministic variations of the clear-air radio refractive-index field can cause diffraction patterns on the ground that are consistent with reflectivity artifacts occasionally seen in SAR images, particularly in those collected at long ranges, short wavelengths, and small grazing angles.

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

    SciTech Connect

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

    2009-06-20

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

  16. Determination of thin film refractive index and thickness by means of film phase thickness

    NASA Astrophysics Data System (ADS)

    Nenkov, Milen; Pencheva, Tamara

    2008-06-01

    A new approach for determination of refractive index dispersion n(?) (the real part of the complex refractive index) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate thin films are investigated in the spectral region 0.38-0.78 ?m and their n(?) and d are calculated. The approach is validated using Swanepoel's method and it is found to be applicable for relatively thin films when measured transmittance spectra have one minimum and one maximum only.

  17. Determination of thin film refractive index and thickness by means of film phase thickness

    NASA Astrophysics Data System (ADS)

    Nenkov, Milen R.; Pencheva, Tamara G.

    2008-06-01

    A new approach for determination of refractive index dispersion n( ?) (the real part of the complex refractive index) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate thin films are investigated in the spectral region 0.38-0.78 ?m and their n( ?) and d are calculated. The approach is validated using Swanepoel’s method and it is found to be applicable for relatively thin films when measured transmittance spectra have one minimum and one maximum only.

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

    PubMed

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

    2003-02-01

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

  19. Uncertainty in length conversion due to change of sensitivity coefficients of refractive index

    NASA Astrophysics Data System (ADS)

    Wei, Dong; Aketagawa, Masato

    2015-06-01

    A value of length measured in air should be converted to the value in vacuum for the purpose of comparison. The typical values of the sensitivity coefficients for a particular wavelength (e.g. 632.99 nm) under standard environmental conditions are widely available. Because all measurements are not performed under standard environmental conditions and the sensitivity coefficient is affected by atmospheric pressure, temperature, and humidity, one question arises naturally: how does a measurement change with environmental conditions? This study investigates the uncertainty in length conversion due to the change of sensitivity coefficients of refractive index. We also clarify that there is no significant difference in conversion uncertainties via sensitivity coefficients of phase and group refractive indexes.

  20. Double-layered metal grating for high-performance refractive index sensing.

    PubMed

    Li, Guozhen; Shen, Yang; Xiao, Guohui; Jin, Chongjun

    2015-04-01

    The detection of minuscule changes in the local refractive index by localized surface plasmon resonances (LSPRs), carried by metal nanostructures, has been used successfully in applications such as real-time and label-free detection of molecular binding events. However, localized plasmons demonstrate 1-2 orders of magnitude lower figure of merit (FOM) compared with their propagating counterparts. Here, we propose and experimentally demonstrate a high-performance refractive index sensor based on a structure of double-layered metal grating (DMG) with an FOM and FOM* reaching 38 and 40 respectively under normal incidence. Such a high FOM and FOM* arise from a result of a sharp fano resonance, which is caused by the coherent interference between the LSPR from the individual top gold stripes and Wood's anomaly (WA). Moreover, a small conformal decay length of ~68 nm is determined in DMG, indicating that the DMG is a promising candidate for label-free biomedical sensing. PMID:25968735

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    Theoretical calculations of the index of refraction of multiple quantum wells and superlattices are presented. The model incorporates both the bound and continuum exciton contributions for the gamma region transitions. In addition, the electronic band structure model has both superlattice and bulk alloy properties. The results indicate that large light-hole masses, i.e., of about 0.23, produced by band mixing effects, are required to account for the experimental data. Furthermore, it is shown that superlattice effects rapidly decrease for energies greater than the confining potential barriers. Overall, the theoretical results are in very good agreement with the experimental data and show the importance of including exciton effects in the index of refraction.

  2. Etching Bragg gratings in Panda fibers for the temperature-independent refractive index sensing.

    PubMed

    Li, Jie; Wang, Hao; Sun, Li-Peng; Huang, Yunyun; Jin, Long; Guan, Bai-Ou

    2014-12-29

    We demonstrate the evolution of the Bragg gratings inscribed in Panda fibers with chemical etching. The resonance wavelengths can blueshift with cladding reduction similar to the conventional counterparts. But the wavelength separation between the two polarizations is co-determined by the stress and the asymmetric shape effects. The fast and slow axes of the fiber can be reversed with each other and zero birefringence can be achieved by chemical etching the structure. When the stress-applying parts of the fiber are removed, the finalizing grating can be exploited for the temperature-independent refractive index sensing, since the modes corresponding to the two polarizations exhibit the dissimilar responses to the external refractive index change but the same response to temperature. Our device is featured with easy achievement, spectral controllability, and relative robustness. PMID:25607160

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

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

  4. Experimental determination of the effective refractive index in strongly scattering media

    Microsoft Academic Search

    J. Gomez Rivas; D. H. Dau; A. Imhof; R. Sprik; B. P. J. Bret; P. M. Johnson; T. W. Hijmans; A. Lagendijk

    2003-01-01

    Measurements of the angular-resolved-optical transmission through strongly scattering samples of porous gallium phosphide are described. Currently porous GaP is the strongest-scattering material for visible light. From these measurements the effective refractive index and the average reflectivity at the sample interface can be obtained. These parameters are of great importance for an accurate interpretation of optical experiments, and are for the

  5. NEGATIVE-REFRACTIVE-INDEX TRANSMISSION-LINE LENSES FOR FREE-SPACE FOCUSING

    Microsoft Academic Search

    A. K. Iyer; G. V. Eleftheriades

    This paper describes a multilayer, negative-refractive-index transmission-line (NRI-TL) lens designed for free-space focusing at X-band (8-12GHz). The constituent layers consist of a network of coplanar-strip (CPS) transmission lines loaded using series interdigitated capacitors and shunt meandered inductors. Full-wave simulation and experimental data showing the transmission properties of the volumetric NRI-TL lens are presented, followed by free-space field measurements demonstrating its

  6. Design of photonic crystal fiber long-period grating refractive index sensor

    Microsoft Academic Search

    Jiri Kanka; Yinian Zhu; Zonghu He; Henry Du

    2009-01-01

    Numerical optimization of photonic crystal fiber (PCF) structures for refractive index sensors based on long period gratings inscribed in PCFs has been performed. The optimization procedure employs the Nelder-Mead downhill simplex algorithm. This direct-search method attempts to minimize a scalar-valued nonlinear function of N real variables (called the objective function) using only function values, without any derivative information. An inverse

  7. DESIGN OF WIRE-WRAPPED ROD BUNDLE MATCHED INDEX-OF-REFRACTION EXPERIMENTS

    Microsoft Academic Search

    Hugh McIlroy; Hongbin Zhang; Kurt D. Hamman

    2008-01-01

    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

  8. Laser-ablation-induced refractive index fields studied using pulsed digital holographic interferometry

    NASA Astrophysics Data System (ADS)

    Amer, Eynas; Gren, Per; Sjödahl, Mikael

    2009-07-01

    Pulsed digital holographic interferometry has been used to investigate the plume and the shock wave generated in the ablation process of a Q-switched Nd-YAG ( ?=1064 nm and pulse duration=12 ns) laser pulse on a polycrystalline boron nitride (PCBN) target under atmospheric air pressure. A special setup based on two synchronised wavelengths from the same laser for simultaneous processing and measurement has been used. Digital holograms were recorded for different time delays using collimated laser light ( ?=532 nm) passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps showing the propagation of the shock wave and the plume generated by the process. Radon inversion has been used to estimate the 3D refractive index fields measured from the projections assuming rotational symmetry. The shock wave density has been calculated using the point explosion model and the shock wave condition equation and its behaviour with time at different power densities ranging from 1.4 to 9.1 GW/cm 2 is presented. Shock front densities have been calculated from the reconstructed refractive index fields using the Gladstone-Dale equation. A comparison of the shock front density calculated from the reconstructed data and that calculated using the point explosion model at different time delays has been done. The comparison shows quite good agreement between the model and the experimental data. Finally the reconstructed refractive index field has been used to estimate the electron number density distribution within the laser-induced plasma. The electron number density behaviour with distance from the target at different power densities and its behaviour with time are shown. The electron number densities are found to be in the order of 10 18 cm -3 and decay at a rate of 3×10 15 electrons/cm 3 ns.

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

    Microsoft Academic Search

    Eric L. Buckland; Robert W. Boyd

    1996-01-01

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

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

    Microsoft Academic Search

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

    1990-01-01

    Based on a comprehensive collection of data previously obtained by Thorma¨hlen etal. on the experimental refractive index of water and steam from the 1870s to the present, a new formulation is presented for the range of 0.2 to 2.5 ?m in wave-length, ?10 to +500 °C in temperature and 0 to 1045 kg m?3 in density. The Lorentz-Lorentz function or

  11. The non-linear refractive index of colloidal PbSe nanocrystals: Spectroscopy and saturation behaviour

    Microsoft Academic Search

    I. Moreels; P. Kockaert; R. Van Deun; K. Driesen; J. Loicq; D. Van Thourhout; Z. Hens

    2006-01-01

    A spectroscopic study of the optical non-linearities of PbSe colloidal solutions was performed with the Z-scan technique, at wavelengths between 1200 and 1750nm. No non-linear absorption is observed, while the third-order non-linear refractive index n2 shows clear resonances, somewhat blueshifted relative to the exciton transitions in the absorbance spectrum. The occurrence of thermal effects is ruled out by time-resolved measurements.

  12. Spectroscopy of the nonlinear refractive index of colloidal PbSe nanocrystals

    Microsoft Academic Search

    I. Moreels; Z. Hens; P. Kockaert; J. Loicq; D. van Thourhout

    2006-01-01

    A spectroscopic study of the optical nonlinearity of PbSe colloidal solutions was performed with the Z-scan technique at wavelength intervals of 1200-1350 and 1540-1750 nm. While nonlinear absorption remains below the detection threshold, the third order nonlinear refractive index n2 shows clear resonances, somewhat blueshifted relative to the exciton transitions in the absorbance spectrum. The occurrence of thermal effects is

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  14. Influence of the refractive index of liquids in the speckle pattern of multimode fibers

    NASA Astrophysics Data System (ADS)

    Galindez, Carlos; Lomer, Mauro; Rodriguez-Cobo, Luis; Lopez-Higuera, J. M.

    2012-10-01

    The distribution of the intensity of each speckle depends on the relative phases of modes in the multimode fiber, so they are extremely sensitive to external perturbations of the fiber. These perturbations can locally appear in the fiber without disrupting the entire optical assembly. If the refractive index of the outside medium of the fiber is changed, it can cause variations in the speckle pattern at the fiber output. Thus, by changing the refractive index of the outside medium the speckle pattern at the output fiber varies and its influence can be observed. In this paper we demonstrate the influence of the refractive index of liquids in the speckle pattern obtained by a multimode fiber. In order to obtain greater sensitivity of the experimental measurement, the fiber is bent in a U-shape and immersed in a liquid. The core and cladding are 240 microns and 250 microns, respectively. The intensity speckle field is then captured by a CCD camera in digital image format and processed by the computer with a Matlab program. The portion of fiber exposed to the disturbance of the liquid is located 2 meters before the exit of the fiber. The portion of the fiber in contact with the liquid is curved with a radius of 2 mm.

  15. Blood pH optrode based on evanescent waves and refractive index change

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    Sensing pH in blood with an silica multimode optical fiber. This sensor is based on evanescent wave absorption and measures the change of the refractive index and absorption in a cladding made of a biocompatible Polymer. In contrast to many existing fiber optical sensors which are based upon different dyes or florescent material to sense the pH, here presents a solution where a part of the cladding is replaced with a Poly (?-amino ester) made of 1.4-Butanediol diacrylate, Piperazine, and Trimethylolpropane Triacrylate. Piperazine has the feature of changing its volume by swelling or shrinking in response to the pH level. This paper utilizes this dimension effect and measure the refractive index and the absorption of the cladding in respect to different pH-levels. The alteration of refractive index also causes a change in the absorption and therefore the output power changes as a function of the pH level. The sensor is sensitive to pH in a wide spectral range and light absorbency can be observed for wavelengths ranging from UV to far IR.

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

    PubMed Central

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

    2013-01-01

    Optical frequency combs have become an essential tool for distance metrology, showing great advantages compared with traditional laser interferometry. However, there is not yet an appropriate method for air refractive index correction to ensure the high performance of such techniques when they are applied in air. In this study, we developed a novel heterodyne interferometry technique based on two-colour frequency combs for air refractive index correction. In continuous 500-second tests, a stability of 1.0 × 10?11 was achieved in the measurement of the difference in the optical distance between two wavelengths. Furthermore, the measurement results and the calculations are in nearly perfect agreement, with a standard deviation of 3.8 × 10?11 throughout the 10-hour period. The final two-colour correction of the refractive index of air over a path length of 61 m was demonstrated to exhibit an uncertainty better than 1.4 × 10?8, which is the best result ever reported without precise knowledge of environmental parameters. PMID:23719387

  17. Refractive Index and Scattering Effects on Radiative Behavior of a Semitransparent Layer

    NASA Technical Reports Server (NTRS)

    Spuckler, C. M.; Siegel, R.

    1993-01-01

    Heat transfer characteristics are analyzed for a plane layer of semitransparent material with refractive index not less than 1. Energy transfer in the material is by conduction, emission, absorption, and isotropic scattering. Each side of the layer is heated by radiation and convection. For a refractive index larger than unity, there is internal reflection of some of the energy within the layer. This, coupled with scattering, has a substantial effect on distributing energy across the layer and altering the temperature distribution from when the refractive index is unity. The effect of scattering is examined by comparisons with results from an earlier paper for an absorbing layer. Results are given for a gray medium with a scattering albedo up to 0.999, and for a two-band spectral variation of the albedo with one band having low absorption. Radiant energy leaving the surface as a result of emission and scattering was examined to determine if it could be used to accurately indicate the surface temperature.

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

    SciTech Connect

    Rigg, P. A., E-mail: prigg@lanl.gov; Scharff, R. J.; Hixson, R. S. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Knudson, M. D. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    2014-07-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    A novel acousto-optic modulation mechanism will be addressed in this paper. Focused Gaussian beam passing through acousto-optic media experiences different refractive index regions arising from acoustic waves generated by ultrasonic source. In this way according to the snell's law of refraction the beam propagation path will be altered when these periodic traveling waves reach the incoming radiation where a typical p-n junction photodiode located inside the rising or falling lobe of the undiffracted Gaussian beam senses these small lateral deflections. Due to small variations of the refractive index the magnitude of deflection will be up to tens of micron outside the modulator. Hence, sharp intensity gradient is required for detecting such small beam movements by appropriate lens configuration to focus the Gaussian profile on the detector junction area. In the other words intensity profile of zero order beam oscillates proportional to the time dependent amplitude of the acoustic waves versus previous methods that intensity of diffracted beam changes with applied ultrasonic intensity. The extracted signal properties depend on the beam collimation, quality of beam profile and depth of focus inside the modulator. The first experimental approach was proceeded using a collimated 532 nm diode laser source (TEM00), distilled water as interaction media and 10 MHz transducer as ultrasonic generator where a cylindrical glass column with input-output flat windows was used for liquid support. The present method has advantages over common acoustooptical techniques as low cost, simplicity of operation, direct modulation of the signal and minimum alignment requirement.

  20. Nonlinear index of refraction of Cu- and Pb-implanted fused silica

    NASA Astrophysics Data System (ADS)

    Haglund, R. F., Jr.; Magruder, R. H.; Weller, R. A.; Yang, L.; Morgan, S. H.; Henderson, D. O.; Zuhr, R. A.

    1991-09-01

    We have measured the nonlinear index of refraction in high-purity fused silica implanted with Pb and Cu ions, using 100-ps pulses from a CW, mode-locked, frequency-doubled Nd:YAG laser (lambda = 532 nm). The nonlinear index measured for the Pb-implanted silica is an order of magnitude larger than that for Cu:silica. Qualitative evidence from infrared reflectance spectra suggests that these differences may result from the distinctive ways in which these implanted ions are incorporated into the glass network: the Cu appears to form of nm-size colloids, while the Pb may be incorporated into a Pb-O-Si glassy phase.

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

    SciTech Connect

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

    2014-03-03

    We proposed a method to realize three-dimensional (3D) gradient index (GRIN) devices requiring large refractive index (RI) range with broadband performance. By combining non-resonant GRIN woodpile photonic crystals structure in the metamaterial regime with a compound liquid medium, a wide RI range (1–6.32) was fulfilled flexibly. As a proof-of-principle for the low-loss and non-dispersive method, a 3D Eaton lens was designed and fabricated based on 3D printing process. Full-wave simulation and experiment validated its omnidirectional wave bending effects in a broad bandwidth covering Ku band (12?GHz–18?GHz)

  2. Polarization-dependent optical absorption of MoS2 for refractive index sensing

    PubMed Central

    Tan, Yang; He, Ruiyun; Cheng, Chen; Wang, Dong; Chen, Yanxue; Chen, Feng

    2014-01-01

    As a noncentrosymmetric crystal with spin-polarized band structure, MoS2 nanomaterials have attracts increasing attention in many areas such as lithium ion batteries, flexible electronic devices, photoluminescence and valleytronics. The investigation of MoS2 is mainly focused on the electronics and spintronics instead of optics, which restrict its applications as key elements of photonics. In this work, we demonstrate the first observation of the polarization-dependent optical absorption of the MoS2 thin film, which is integrated onto an optical waveguide device. With this feature, a novel optical sensor combining MoS2 thin-film and a microfluidic structure has been constituted to achieve the sensitive monitoring of refractive index. Our work indicates the MoS2 thin film as a complementary material to graphene for the optical polarizer in the visible light range, and explores a new application direction of MoS2 nanomaterials for the construction of photonic circuits. PMID:25516116

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

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Wei

    2013-09-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

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

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

    PubMed

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

    2008-04-14

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

  6. Engineering of parallel plasmonic-photonic interactions for on-chip refractive index sensors.

    PubMed

    Lin, Linhan; Zheng, Yuebing

    2015-07-28

    Ultra-narrow linewidth in the extinction spectrum of noble metal nanoparticle arrays induced by the lattice plasmon resonances (LPRs) is of great significance for applications in plasmonic lasers and plasmonic sensors. However, the challenge of sustaining LPRs in an asymmetric environment greatly restricts their practical applications, especially for high-performance on-chip plasmonic sensors. Herein, we fully study the parallel plasmonic-photonic interactions in both the Au nanodisk arrays (NDAs) and the core/shell SiO2/Au nanocylinder arrays (NCAs). Different from the dipolar interactions in the conventionally studied orthogonal coupling, the horizontal propagating electric field introduces the out-of-plane "hot spots" and results in electric field delocalization. Through controlling the aspect ratio to manipulate the "hot spot" distributions of the localized surface plasmon resonances (LSPRs) in the NCAs, we demonstrate a high-performance refractive index sensor with a wide dynamic range of refractive indexes ranging from 1.0 to 1.5. Both high figure of merit (FOM) and high signal-to-noise ratio (SNR) can be maintained under these detectable refractive indices. Furthermore, the electromagnetic field distributions confirm that the high FOM in the wide dynamic range is attributed to the parallel coupling between the superstrate diffraction orders and the height-induced LSPR modes. Our study on the near-field "hot-spot" engineering and far-field parallel coupling paves the way towards improved understanding of the parallel LPRs and the design of high-performance on-chip refractive index sensors. PMID:26133011

  7. Enhanced Coupling of Light from Organic Electroluminescent Device Using Diffusive Particle Dispersed High Refractive Index Resin Substrate

    Microsoft Academic Search

    Toshitaka Nakamura; Hironaka Fujii; Noriyuki Juni; Naoto Tsutsumi

    2006-01-01

    To improve light extraction from organic electroluminescent (EL) devices, we introduced a diffusive substrate with 25 ?m thickness\\u000a consisting of high refractive index resin and scattering particles. It is expected that the diffusive substrate with high\\u000a refractive index matrix converts the waveguided emission into external emission from both glass substrate and indium-tin-oxide\\/organic\\u000a layer. We used the ray tracing method to

  8. Detection of external refractive index change with high sensitivity using long-period gratings in photonic crystal fiber

    Microsoft Academic Search

    Yinian Zhu; Zonghu He; Henry Du

    2008-01-01

    We report that the proposed long-period gratings (LPGs), which were fabricated in an endlessly single-mode photonic crystal fiber (ESM-PCF) via point-by-point residual stress relaxation utilizing focused CO2 laser irradiation, exhibit a high sensitivity to variations in the external refractive index, with an identified shifting of attenuation band as large as 4.4pm for 1×10?5 change in the surrounding refractive index over

  9. Analysis on the variation of Ar and He plasma refractive index with temperature in CO2 laser beam welding

    Microsoft Academic Search

    Jinhe Liu; Fengming Zhang; Decai Yang

    1998-01-01

    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

  10. Detection of small-scale roughness and refractive index of sea ice in passive satellite microwave remote sensing

    Microsoft Academic Search

    Sungwook Hong

    2010-01-01

    Polar ice masses and sheets are sensitive indicators of climate change. Small-scale surface roughness significantly impacts the microwave emission of the sea ice\\/snow surface; however, published results of surface roughness measurements of sea ice are rare. Knowing the refractive index is important to discriminate between objects. In this study, the small-scale roughness and refractive index over sea ice are estimated

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

    PubMed Central

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

    2010-01-01

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

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

    E-print Network

    Boyer, Edmond

    of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary-workers, with the first measurements of the index of refraction of gases for sodium waves [2] in 1995 and the subsequent the first measurements of the index of refraction of gases for lithium waves. Several papers [7, 8, 9, 10

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

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

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

  14. Determination of volume, shape and refractive index of individual blood platelets

    E-print Network

    Kolesnikova, Irina V; Yurkin, Maxim A; Hoekstra, Alfons G; Maltsev, Valeri P; Semyanov, Konstantin A

    2008-01-01

    Light scattering patterns (LSP) of blood platelets were theoretically and experimentally analyzed. We used spicular spheroids as a model for the platelets with pseudopodia. The discrete dipole approximation was employed to simulate light scattering from an individual spicular spheroid constructed from a homogeneous oblate spheroid and 14 rectilinear parallelepipeds rising from the cell centre. These parallelepipeds have a weak effect on the LSP over the measured angular range. Therefore, a homogeneous oblate spheroid was taken as a simplified optical model for platelets. Using the T-matrix method, we computed the LSP over a range of volumes, aspect ratios and refractive indices. Measured LSPs of individual platelets were compared one by one with the theoretical set and the best fit was taken to characterize the measured platelets, resulting in distributions of volume, aspect ratio and refractive index.

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

    PubMed

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

    2013-01-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

    Qiao, H A; Lipschultz, Kristen A; Anheier, N C; McCloy, J S

    2012-05-01

    A state-of-the-art mid-infrared prism coupler was used to study suspected anisotropy in the refractive index of forward-looking-infrared grade chemical vapor deposited (CVD) zinc sulfide. Samples were prepared with columnar grain structure in and perpendicular to the sample plane, as well as from different depths in the CVD growth body. This study was motivated by the growing industry concern among optical design engineers, as well as developers of mid-infrared systems, over the reliability of historically accepted index data. Prior photoluminescence and x-ray diffraction measurements have suggested that refractive index may vary according to sample orientation with respect to the grain structure. Measurements were conducted to provide optical dispersion and thermal index (dn/dT) data at discrete laser wavelengths between 0.633 and 10.591 ?m at two temperature set points (30 °C and 90 °C). Refractive index measurements between samples exhibited an average standard deviation comparable to the uncertainty of the prism coupler measurement (0.0004 refractive index units), suggesting that the variation in refractive index as a function of sample orientation and CVD deposition time is negligible and should have no impact on subsequent optical designs. Measured dispersion data at mid-infrared wavelengths were also found to agree well with prior published measurements. PMID:22555685

  18. Measurement of refractive indices and thermal refractive index coefficients of Cr 3+ : Be 3 Al 2 Si 6 O 18 by auto-collimation method

    Microsoft Academic Search

    Zhenqiang Chen; Ge Zhang; Hongyuan Shen; Chenghui Huang; Wen Liu

    2004-01-01

    The principal refractive indices and the thermal refractive index coefficients for Be3Al2Si6O18 crystal doped with 1.01wt% Cr2O3 have been accurately measured by the auto-collimation method at wavelengths of 0.488, 0.53975, 1.064, 1.0795 and 1.3414 ?m,\\u000a and temperatures of 308.2, 328.6, 359.1 and 395.4 K respectively. Based on the measured results of principal indices of 0.488,\\u000a 0.6328, 1.0795 and 1.3414?m, the

  19. Higher-order nonlinearity of refractive index: the case of argon.

    PubMed

    Tarazkar, Maryam; Romanov, Dmitri A; Levis, Robert J

    2014-06-01

    The nonlinear coefficients, n4, of the time-dependent refractive index for argon are calculated in the non-resonant optical regime. Second-order polynomial fitting of DC-Kerr, ?((2))(-?; ?, 0, 0), electric field induced second harmonic generation (ESHG), ?((2))(-2?; ?, ?, 0), and static second-order hyperpolarizability, ?((2))(0; 0, 0, 0), is performed using an auxiliary electric field approach to obtain the corresponding fourth-order optical properties. A number of basis sets are investigated for the fourth-order hyperpolarizability processes at 800 nm at coupled cluster singles and doubles level of theory, starting with the t-aug-cc-pV5Z basis set and expanding that basis set by adding diffuse functions and polarization functions. Comparison shows that the results obtained with the t-aug-cc-pV5Z basis are in very good agreement with the results obtained using the q-aug-cc-pV5Z, t-aug-cc-pV6Z, and q-aug-cc-pV6Z basis sets. To calculate the nonlinear refractive index n4, an approximate formula is suggested which expresses the related degenerate six-wave mixing coefficient, ?((4))(-?; ?, -?, ?, -?, ?), in terms of the DC-Kerr, ?((4))(-?; ?, 0, 0, 0, 0), ESHG, ?((4))(-2?; ?, ?, 0, 0, 0), and the static fourth-order hyperpolarizability coefficients. The higher-order nonlinear refractive index n4 is found to be positive over the wavelengths 300 nm-2000 nm. In the infrared spectral range, the obtained values of n4 are in qualitative agreement with the results of Kramers-Kronig-based calculations. PMID:24908017

  20. Higher-order nonlinearity of refractive index: The case of argon

    NASA Astrophysics Data System (ADS)

    Tarazkar, Maryam; Romanov, Dmitri A.; Levis, Robert J.

    2014-06-01

    The nonlinear coefficients, n4, of the time-dependent refractive index for argon are calculated in the non-resonant optical regime. Second-order polynomial fitting of DC-Kerr, ?(2)(-?; ?, 0, 0), electric field induced second harmonic generation (ESHG), ?(2)(-2?; ?, ?, 0), and static second-order hyperpolarizability, ?(2)(0; 0, 0, 0), is performed using an auxiliary electric field approach to obtain the corresponding fourth-order optical properties. A number of basis sets are investigated for the fourth-order hyperpolarizability processes at 800 nm at coupled cluster singles and doubles level of theory, starting with the t-aug-cc-pV5Z basis set and expanding that basis set by adding diffuse functions and polarization functions. Comparison shows that the results obtained with the t-aug-cc-pV5Z basis are in very good agreement with the results obtained using the q-aug-cc-pV5Z, t-aug-cc-pV6Z, and q-aug-cc-pV6Z basis sets. To calculate the nonlinear refractive index n4, an approximate formula is suggested which expresses the related degenerate six-wave mixing coefficient, ?(4)(-?; ?, -?, ?, -?, ?), in terms of the DC-Kerr, ?(4)(-?; ?, 0, 0, 0, 0), ESHG, ?(4)(-2?; ?, ?, 0, 0, 0), and the static fourth-order hyperpolarizability coefficients. The higher-order nonlinear refractive index n4 is found to be positive over the wavelengths 300 nm-2000 nm. In the infrared spectral range, the obtained values of n4 are in qualitative agreement with the results of Kramers-Kronig-based calculations.

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

    NASA Astrophysics Data System (ADS)

    Singh, Amit

    2015-06-01

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

  2. Wavelength and NOx dependent complex refractive index of SOAs generated from the photooxidation of toluene

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Sato, K.; Matsumi, Y.; Imamura, T.; Yamazaki, A.; Uchiyama, A.

    2012-06-01

    Recently, secondary organic aerosols (SOAs) generated from anthropogenic volatile organic compounds have been proposed as a possible source of lightabsorbing organic compounds "brown carbon" in the urban atmosphere. However, the atmospheric importance of these SOAs remains unclear due to limited information about their optical properties. In this study, the complex refractive index (RI, m=n - ki) values at 405, 532, and 781 nm of the SOAs generated during the photooxidation of toluene (toluene-SOAs) under a variety of initial nitrogen oxide (NOx= NO + NO2) conditions were examined by photoacoustic spectroscopy (PAS) and cavity ring down spectroscopy (CRDS). The complex RI values obtained in the present study and reported in the literature indicate that the k value, which represents the light absorption of the toluene-SOAs steeply increased to shorter wavelengths at <405 nm, while the n value gradually increased to shorter wavelengths from 781 to 355 nm. The k values at 405 nm were found to increase from 1.8 × 10-3 to 7.2 × 10-3 with increasing initial NOx concentration from 109 to 571 ppbv. The nitrate to organics ratio of the SOAs determined using a highresolution time-of-flight aerosol mass spectrometer (H-ToF-AMS) also increased with increasing initial NOx concentration. The RI values of the SOAs generated during the photooxidation of 1,3,5-trimethylbenzene in the presence of NOx (1,3,5-TMB-SOAs) were also determined to investigate the influence of the chemical structure of the precursor on the optical properties of the SOAs, and it was found that the light absorption of the 1,3,5-TMB-SOAs is negligible at all of the wavelengths investigated (405, 532, and 781 nm). These results can be reasonably explained by the hypothesis that nitro-aromatic compounds such as nitro-cresols are the major contributors to the light absorption of the toluene-SOAs. Using the obtained RI values, mass absorption cross sections of the toluene-SOAs at 405 and 532 nm were estimated to be 0.08-0.48 and 0.002-0.081 m2 g-1, respectively, under typical conditions in an urban atmosphere during the daytime. These results indicate that light absorption by the SOAs potentially contributes to the radiation balance at ultraviolet wavelengths below ~400 nm, specifically when the mass concentrations of the anthropogenic SOAs are significant compared with those of black carbon particles.

  3. Refractive index sensing characteristics of dual resonance long period gratings in bare and metal-coated D-shaped fibers.

    PubMed

    Mani Tripathi, Saurabh; Marin, Emmanuel; Kumar, Arun; Meunier, Jean-Pierre

    2009-11-01

    We present a theoretical study of the ambient refractive index sensing characteristics of long period gratings in bare and metal-coated D-shaped fibers. An equivalent rectangular core waveguide method based on the first-order perturbation theory has been used to study the modal behavior of the waveguide. Power coupling corresponding to dual resonance in both cases has been investigated, and an optimum metal thickness giving maximum sensitivity has been found to exist. The study shows that the dual resonances can be shifted to lower wavelengths by increasing (decreasing) the metal thickness (core to flat surface separation). Further, an optimum combination of metal thickness and core to flat surface separation, corresponding to maximum sensitivity, has been presented for different cladding modes and their relative performance has been discussed. It has been shown theoretically that detection of refractive index changes as small as 1.67x10(-7) RIU in the ambient region is possible using the optimized parameters. The study should find application in realizing highly sensitive biochemical sensors. PMID:19881646

  4. Transient four-wave mixing in saturable media with a nonlinear refractive index

    NASA Astrophysics Data System (ADS)

    de Souza, P. C.; Nader, G.; Catunda, T.; Muramatsu, M.; Horowicz, R. J.

    1999-05-01

    We study the transient behaviour of a degenerate four-wave mixing process in a saturable nonlinear medium where the laser induced refractive index change is given by ? n= n2I/(1+ I/ Is). The theoretical model we develop can be applied for any complex value of n2 which contains absorptive, dispersive or mixed components. This model explains very well our experimental results in GdAlO 3:Cr 3+, using n2 and Is values that are in good agreement with previous measurements.

  5. Spatiotemporal collapse in a nonlinear waveguide with a randomly fluctuating refractive index.

    PubMed

    Gaididei, Y B; Christiansen, P L

    1998-07-15

    Analytical results, based on the virial theorem and the Furutsu-Novikov theorem, of the spatiotemporal evolution of a pulse in a nonlinear waveguide with a randomly fluctuating refractive index are presented. For initial conditions in which total collapse occurs in a homogeneous waveguide, random fluctuations postpone the collapse. Sufficiently large-amplitude and short-wavelength fluctuations can cause an initially localized pulse to spread instead of contracting. We show that the disorder can be applied to induce a high degree of controllability of the spatiotemporal extent of the pulses in the nonlinear waveguide. PMID:18087437

  6. Structural properties of aqueous metoprolol succinate solutions. Density, viscosity, and refractive index at 311 K

    NASA Astrophysics Data System (ADS)

    Deosarkar, S. D.; Kalyankar, T. M.

    2013-06-01

    Density, viscosity and refractive index of aqueous solutions of metoprolol succinate of different concentrations (0.005-0.05 mol dm-3) were measured at 38°C. Apparent molar volume of resultant solutions were calculated and fitted to the Masson's equation and apparent molar volume at infinite dilution was determined graphically. Viscosity data of solutions has been fitted to the Jone-Dole equation and viscosity A- and B-coefficients were determined graphically. Physicochemical data obtained were discussed in terms of molecular interactions.

  7. Phase thickness approach for determination of thin film refractive index dispersion from transmittance spectra

    NASA Astrophysics Data System (ADS)

    Nenkov, M. R.; Pencheva, T. G.

    2008-06-01

    A novel approach for determination of refractive index dispersion n(? ) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate and titanium oxide thin films are investigated and their n(? ) and d are calculated. The approach is validated using Swanepoel's method and it is found to be applicable for relatively thinner films when measured transmittance spectra have one minimum and one maximum only.

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

    NASA Astrophysics Data System (ADS)

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

    1994-07-01

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

  9. Refractive index measurement using an optical cavity based biosensor with a differential detection

    NASA Astrophysics Data System (ADS)

    Cho, SaiHim; Brake, Joshua H.; Joy, Cody; Kim, Seunghyun

    2015-03-01

    We proposed a low cost optical cavity based biosensor with a differential detection for point-of-care diagnosis. Two lasers at different wavelengths are used for the differential detection. This method enhances the sensitivity through higher responsivity and noise cancelation. To reduce noise further, especially due to the unstable low cost laser diode output, we employed a referencing method in which a reference pixel value in each CMOS image frame is subtracted from all other pixels. To validate the designed structure and demonstrate the sensitivity of it, we perform refractive index measurements of fluids with our design. In this presentation, we will discuss our design, simulation results, and measurement results.

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

    E-print Network

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

    2015-01-01

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

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

    SciTech Connect

    Shelton, David P.

    2011-07-20

    The refractive index of a liquid is determined with 0.0003 accuracy from measurements of laser beam displacement by a liquid-filled standard 10 mm spectrophotometer cell. The apparatus and methods are described and the results of measurements at {lambda}=1064 nm and T=25.0 deg. C for 30 solvents and deuterated solvents are presented. Several sources of potential systematic errors as large as 0.003 are identified, the most important being the curvature of the liquid cell windows. The measurements are analyzed accounting for the significant imperfections of the apparatus.

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

    SciTech Connect

    Wang, Chao [Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong (China); The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057 (China); Jin, Wa; Ma, Jun; Jin, Wei, E-mail: eewjin@polyu.edu.hk; Yang, Fan; Ho, Hoi Lut [Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong (China); Liao, Changrui; Wang, Yiping [Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education/Guangdong Province, Shenzhen University, Shenzhen 518060 (China)

    2014-08-11

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-07-01

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

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

    PubMed

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

    2006-07-01

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

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

    PubMed

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

    2014-06-15

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

  16. Spectral behavior in thinned long period gratings: effects of fiber diameter on refractive index sensitivity.

    PubMed

    Iadicicco, Agostino; Campopiano, Stefania; Giordano, Michele; Cusano, Andrea

    2007-10-01

    We report the experimental investigation of the sensitivity characteristics to the surrounding refractive index (SRI) in thinned long period gratings (LPGs) for a wide range of fiber diameters and different low-orders cladding modes. Wet chemical etching combined with microscopic and spectral analysis allow us to experimentally retrieve the SRI sensitivity characteristics of thinned LPGs. The obtained results allow us to identify accurately the dependence of the sensitivity characteristics on the fiber radius, taking into account the SRI range and the order mode. This provides a useful tool to identify the thinned structure able to fulfill the sensitivity requirements by maintaining an acceptable robustness level. PMID:17906722

  17. Miniature highly-birefringent microfiber loop with extremely-high refractive index sensitivity.

    PubMed

    Sun, Lipeng; Li, Jie; Tan, Yanzhen; Shen, Xiang; Xie, Xiaodong; Gao, Shuai; Guan, Bai-Ou

    2012-04-23

    A miniature polarimetric interferometer with the twist of a highly-birefringent microfiber is demonstrated. Good transmission spectral characteristics, which are co-governed by the birefringence and the twist degree of the microfiber, are investigated. The structure exhibits extremely-high sensitivity of around 24,373 nm per refractive-index unit and excellent temperature stability of better than 0.005 nm/°C. Featured with compactness, reconfigurability, stability, robustness, and compatibility with other fiberized components, our device has potential in tunable filtering, sensing, multi-wavelength lasing, and etc. PMID:22535109

  18. Measurement of nonlinear refractive index and transmission in polydiacetylene waveguides at 1.319 µm

    Microsoft Academic Search

    K. Rochford; R. Zanoni; G. I. Stegeman; W. Krug; E. Miao; M. W. Beranek

    1991-01-01

    Nonlinear optical measurements in strip-loaded channel waveguides of poly(4-BCMU) at 1.319 ?m are reported. Using a pulse-modulated interferometry method, the intensity-dependent refractive index is found to have an electronic contribution, n2=(4.8±2.7)×10?8 cm2\\/MW, and an estimated thermal contribution, n2=?(7.9±4.5)×10?11 cm2\\/MW, for 60 pS laser pulses at 76 MHz. The two-photon absorption coefficient ? is less than 0.25 cm\\/GW. Figures-of-merit suggest that

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  20. Simulation and optimization of multilayer-coated microsphere in temperature and refractive index sensing

    NASA Astrophysics Data System (ADS)

    Dong, Yongchao; Wang, Keyi; Jin, Xueying

    2015-06-01

    This study proposes an approach to simultaneously detect the refractive-index (RI) and temperature changes with a three-layer-coated microsphere resonator. The RIs of the three layers are high, low, and high from inside to outside. Using the perturbation theory and finite element method (FEM), a model is developed to calculate the RI and temperature sensitivities for the inner mode and outer mode, respectively. As a result, a second-order sensing matrix is defined to determine the RI and temperature changes. By optimizing the coatings thickness, the thermal noise can be eliminated with the differential frequency of outer and inner modes.

  1. Significant correlation between refractive index and activity of mitochondria: single mitochondrion study

    PubMed Central

    Haseda, Keisuke; Kanematsu, Keita; Noguchi, Keiichi; Saito, Hiromu; Umeda, Norihiro; Ohta, Yoshihiro

    2015-01-01

    Measurements of refractive indices (RIs) of intracellular components can provide useful information on the structure and function of cells. The present study reports, for the first time, determination of the RI of an isolated mitochondrion in isotonic solution using retardation-modulated differential interference contrast microscopy. The value was 1.41 ± 0.01, indicating that mitochondria are densely packed with molecules having high RIs. Further, the RIs of each mitochondrion were significantly correlated with the mitochondrial membrane potential, an index of mitochondrial activity. These results will provide useful information on the structures and functions of cells based on the intracellular distribution of RIs. PMID:25798310

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The nonlinear analysis of slow-wave electron cyclotron masers (ECM) based on anomalous Doppler effect in a slab waveguide is presented. A method of tapered refractive index (TRI) is proposed to enhance the efficiency of slow-wave ECM. The numerical calculations show that the TRI method can significantly enhance the efficiency of slow-wave ECM with the frequency ranging from the microwave to terahertz band. The effect of beam velocity spread on the efficiency has also been studied. Although the velocity spread suppresses the efficiency significantly, a great enhancement of efficiency can still be introduced by the TRI method.

  3. Continuous refractive index dispersion measurement based on derivative total reflection method

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Traditionally, continuous refractive index dispersion (CRID) measurement of materials with scattering is hard to realize. In this paper, CRID measurement based on the derivative total reflection method (CRIDM-DTRM) is proposed to measure the CRID of both absorption and scattering materials. It effectively determined the CRID of K9 glass, concentrated milk, and 0.5% methyl red solution in the 400-750 nm range with the spectral resolution of about 0.259 nm. For the first time, CRID of a scattering material is measured. CRIDM-DTRM is a useful technique in the field of RID measurement, especially for biotissues and anomalous dispersion materials.

  4. Subwavelength modulation of surface relief and refractive index in preirradiated liquid-crystalline polymer films

    SciTech Connect

    Yu Haifeng; Shishido, Atsushi; Ikeda, Tomiki [Chemical Resources Laboratory, Tokyo Institute of Technology, R1-11, 4259, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2008-03-10

    We present a simple method to record subwavelength gratings (SWGs) in an azobenzene (AZ)-containing liquid-crystalline polymer by preirradiation. Since the cooperative motions of mesogens are eliminated in a cis-AZ-rich isotropic phase by the pretreatment, the subwavelength modulation of surface relief and refractive index (RI) was obtained. The surface relief of less than 10 nm and the RI modulation were detected by atomic force microscopy. A large phase retardation and formed birefringence were obtained in the recorded SWGs in which a possible schematic illustration of AZ was proposed.

  5. High Refractive Index Polysiloxane as Injectable, In Situ Curable Accommodating Intraocular Lens

    PubMed Central

    Hao, Xiaojuan; Jeffery, Justine L.; Le, Tam P.T.; McFarland, Gail; Johnson, Graham; Mulder, Roger J.; Garrett, Qian; Manns, Fabrice; Nankivil, Derek; Arrieta, Esdras; Ho, Arthur; Parel, Jean-Marie; Hughes, Timothy C.

    2012-01-01

    Functionalised siloxane macromonomers, with properties designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via reequilibration of a phenyl group-containing polysiloxane of very high molecular weight with octamethylcyclotetrasiloxane (D4) and 2,4,6,8-tetra(n-propyl-3-methacrylate)-2,4,6,8-tetramethylcyclotetrasiloxane (D4AM) in toluene using trifluoromethanesulfonic acid as a catalyst. Hexaethyldisiloxane was used as an end group to control the molecular weight of the polymer. The generated polymers had a consistency suitable for injection into the empty lens capsule. The polymers contained a low ratio of polymerisable groups so that, in the presence of a photo-initiator, they could be cured on demand in situ within 5 minutes under irradiation of blue light to form an intraocular lens within the lens capsule. All resulting polysiloxane soft gels had a low elastic modulus and thus should be able to restore accommodation. The pre-cure viscosity and post-cure modulus of the generated polysiloxanes were controlled by the end group and D4AM concentrations respectively in the re-equilibration reactions. The refractive index could be precisely controlled by adjusting the aromatic ratio in the polymer to suit such application as an artificial lens. Lens stretching experiments with both human and non-human primate cadaver lenses of different ages refilled with polysiloxane polymers provided a significant increase in amplitude of accommodation (up to 4 D more than that of the respective natural lens). Both in vitro cytotoxicity study using L929 cell lines and in vivo biocompatibility study in rabbit models demonstrated the non-cytotoxicity and ocular biocompatibility of the polymer. PMID:22594975

  6. Infrared Refractive Index of Silicon: Parity and Sum-Rule Tests

    NASA Astrophysics Data System (ADS)

    Karstens, William; Inokuti, Mitio; Smith, David Y.

    2012-02-01

    We have resolved conflicting reports for the IR refractive index of silicon using general considerations of linear response theory. We find that use of unphysical series expansions in the analysis of channel spectra has been a significant source of systematic error. Recognition that the index is an even function of photon energy is crucial for analysis of these measurements and clarifies data presentation. In the region of high IR transparency of elemental semiconductors, the index may be expanded in a rapidly convergent Taylor series. Coefficients of terms in the (2n)^th power of energy are proportional to the (2n+1)^th inverse moment of the electronic absorption spectrum. In the favorable case of intrinsic Si, the electronic absorption is sufficiently well known that independent values of the intercept, slope and curvature of plots of index vs. the square of photon energy may be calculated. Index data sets with parameters significantly different from these suffer from systematic errors or refer to impure samples. Using these parity and sum-rule tests we have prepared a composite index data set for intrinsic silicon that represents a best fit to reliable measurements from microwaves to the visible. Applications to germanium and diamond will be discussed.

  7. Development of a single crystal with a high index of refraction

    NASA Astrophysics Data System (ADS)

    Kurosawa, Shunsuke; Kochurikhin, Vladimir V.; Yamaji, Akihiro; Yokota, Yuui; Kubo, Hidetoshi; Tanimori, Toru; Yoshikawa, Akira

    2013-12-01

    Time-of-flight Positron emission tomography (TOF-PET) is one of the next-generation medical imaging methods, which requires scintillators with a very short decay time. However, the shortest scintillation decay times are typically 20-30 ns, and these values are not sufficient for TOF-PET. Cherenkov counters are used in high energy physics and they are expected to be applied in medical imaging due to their short decay time. Here, high-refractive index materials are necessary for Cherenkov radiators to reach a high light output. We measured refractive indices of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG) and Lu3Ga5O12 (LuGG) crystals grown by a micro-pulling-down (?-PD) method. The GGG, YGG and LuGG crystals were found to have refractive indices of ~2.5, ~2.3 and ~2.3 at 400 nm, respectively. Then we grew a 40 mm diameter GGG crystal by the Czochralski method, and the emission decay times of the GGG crystals irradiated with muons and gamma rays were 10±1 ns and 10±2 ns, respectively, using a photomultiplier tube (Hamamatsu R6231-100). Cherenkov light of the GGG crystal could be observed for the gamma-ray irradiation.

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

    SciTech Connect

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

    2012-04-01

    A state-of-the-art mid-infrared prism coupler was used to study the refractive index properties of forward-looking-infrared (FLIR) grade zinc sulfide samples prepared with unique planar grain orientations and locations with respect to the CVD growth axis. This study was motivated by prior photoluminescence and x-ray diffraction measurements that suggested refractive index may vary according to grain orientation. Measurements were conducted to provide optical dispersion and thermal index (dn/dT) data at discrete laser wavelengths between 0.633 and 10.591 {mu}m at two temperature set points (30 C and 90 C). Refractive index measurements between samples exhibited an average standard deviation comparable to the uncertainty of the prism coupler measurement (0.0004 refractive index units), suggesting that the variation in refractive index as a function of planar grain orientation and CVD deposition time is negligible, and should have no impact on subsequent optical designs. Measured dispersion data at mid-infrared wavelengths was found to agree well with prior published measurements.

  9. Measurements of the imaginary part of the refractive index between 300 and 700 nanometers for Mount St. Helens ash

    SciTech Connect

    Patterson, E.M.

    1981-01-01

    The absorption properties, expressed as a wavelength-dependent imaginary index of refraction, of the Mount St. Helens ash from the 18 May 1980 eruption were measured between 300 and 700 nanometers by diffuse reflectance techniques. The measurements were made for both surface and stratospheric samples. The stratospheric samples show imaginary index values that decrease from approximately 0.01 to 0.02 at 300 nanometers to about 0.0015 at 700 nanometers. The surface samples show less wavelength variation in imaginary refractive index over this spectral range.

  10. Experimental demonstration of the frequency shift of bandgaps in photonic crystal fibers due to refractive index scaling

    Microsoft Academic Search

    G. Antonopoulos; F. Benabid; T. A. Birks; D. M. Bird; J. C. Knight; P. St. J. Russell

    2006-01-01

    Experimental demonstration of the frequency shift of photonic bandgaps due to refractive index scaling using D2O-filled hollow-core photonic crystal fibers is presented. The results confirm a simple scaling law for bandgaps in fibers in which the low-index medium is varied.

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

    NASA Astrophysics Data System (ADS)

    Pramanik, Sanchita; Sarkar, Somenath

    2014-10-01

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

  12. Influence of nonlinear dispersion of the refraction index on the Sagnac effect in semiconductor ring lasers

    NASA Astrophysics Data System (ADS)

    Eliseev, Peter G.; Osi?ski, Marek

    2007-02-01

    Mutually contradicting previously reported theoretical results on the effects of a dispersive active medium in a ring laser on its sensitivity to rotation are critically analyzed. A measure of the rotation rate in the active ring resonator is the beating frequency ?? between the counterpropagating waves whose frequencies are shifted in opposite directions due to the Sagnac effect. ?? is shown to be inversely proportional to the group index of the medium filling the cavity. A comparison of the results obtained considering the resting and rotating frames confirms the applicability of Fresnel's original expression for the optical drag effect to the analysis of the Sagnac effect in an active laser gyro. The frequency splitting ?? is sensitive to dispersion via the group refractive index.

  13. Self-referenced spectral interferometry for simultaneous measurements of thickness and refractive index.

    PubMed

    Na, Jihoon; Choi, Hae Young; Choi, Eun Seo; Lee, ChangSu; Lee, Byeong Ha

    2009-05-01

    We present a method for simultaneously measuring the thickness and the group refractive index of a specimen using self-referenced spectral-domain fiber-based interferometry. By removing the scanning part and using the fiber-based configuration, the system complexity and stability could be significantly improved. To minimize the system drift, we utilized the signals originated from the fiber ends of both arms. Implementing in a self-referenced configuration, we could improve the measurement accuracy down to a decimal place. Experimental measurements were made with a 1.555 mm thick fused silica plate. At 814 nm the thickness was measured as 1.5546 +/- 0.0002 mm, and at the same time, the group index was obtained as 1.4627 +/- 0.0002. PMID:19412203

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  15. Gap solitons in PT -symmetric lattices with a lower refractive-index core

    NASA Astrophysics Data System (ADS)

    Dong, Liangwei; Gu, Linlin; Guo, Dengchu

    2015-05-01

    We address the existence and stability properties of families of gap solitons in a lower refractive-index core, sandwiched between two optical lattices with a parity-time (PT ) symmetry imprinted in a defocusing medium. The scale of flat-topped complex solitons can be controlled arbitrarily by varying the embedded index core. Multipeaked solitons are found to exhibit equal peak values in the region of the index core, and they have no analog in other lattice-modulated or bulk media. We demonstrate that, in sharp contrast to solitons in regular PT lattices, flat-topped and multipeaked solitons are either stable or suffer a negligibly weak instability, even when the gain-loss coefficient approaches the PT -symmetry-breaking point. Our results, thus, build a bridge between the PT defect solitons in a narrow index core and the PT kink pairs in a broad index core. We also suggest an effective way for the observation of "surface solitons" in PT -symmetric lattices.

  16. High reliability solid refractive index matching materials for field installable connections in FTTH network

    NASA Astrophysics Data System (ADS)

    Saito, Kotaro; Kihara, Mitsuru; Shimizu, Tomoya; Yoneda, Keisuke; Kurashima, Toshio

    2015-06-01

    We performed environmental and accelerated aging tests to ensure the long-term reliability of solid type refractive index matching material at a splice point. Stable optical characteristics were confirmed in environmental tests based on an IEC standard. In an accelerated aging test at 140 °C, which is very much higher than the specification test temperature, the index matching material itself and spliced fibers passing through it had steady optical characteristics. Then we performed an accelerated aging test on an index matching material attached to a built-in fiber before splicing it in the worst condition, which is different from the normal use configuration. As a result, we confirmed that the repeated insertion and removal of fiber for splicing resulted in failure. We consider that the repetition of adhesion between index matching material and fibers causes the splice to degrade. With this result, we used the Arrhenius model to estimate a median lifetime of about 68 years in a high temperature environment of 60 °C. Thus solid type index matching material at a splice point is highly reliable over long periods under normal conditions of use.

  17. Air etalon facilitated simultaneous measurement of group refractive index and thickness using spectral interferometry.

    PubMed

    Zhang, Ke; Tao, Li; Cheng, Wenkai; Liu, Jianhua; Chen, Zhongping

    2014-11-01

    A simple method based on air etalons of a transparent cavity is proposed to simultaneously measure the group refractive index and thickness of a transparent optical plate by spectral domain low coherence interferometry. In this method, only a single beam path is needed in contrast to the two beam paths, the reference and sample arms, of the conventional Michelson interferometer. An empty cavity is first constructed in the beam path by two glass plates. Then the transparent plate under test is inserted into the cavity, so that two air gaps are formed in the cavity. A beam of light of low coherence length is then transmitted through the cavity in the normal direction. Measurements of the reflected waves by the air gaps before and after the sample plate is put into the cavity allow us to determine the group refractive index (ng) and thickness (d) of the sample simultaneously. The relative precision of the results for d and ng are both approximately 7×10-4. PMID:25402915

  18. Waveguides and nonlinear index of refraction of borate glass doped with transition metals

    NASA Astrophysics Data System (ADS)

    Almeida, Juliana M. P.; Fonseca, Ruben D.; De Boni, Leonardo; Diniz, Andre Rosa S.; Hernandes, Antonio C.; Ferreira, Paulo H. D.; Mendonca, Cleber R.

    2015-04-01

    The ability to write 3D waveguides by femtosecond laser micromachining and the nonlinear refractive index (n2) spectrum of a new borate glass matrix, containing zinc and lead oxides - (BZP) have been investigated. The transparent matrix was doped with transition metals (CdCl2, Fe2O3, MnO2 and CoO) in order to introduce electronic transitions in visible spectrum, aiming to evaluate their influence on the waveguides and n2 spectrum. We observed that n2 is approximately constant from 600 to 1500 nm, exhibiting an average value of 4.5 × 10-20 m2/W, which is about twice larger than the one for fused silica. The waveguide profile is influenced by the self-focusing effect of the matrix owing to its positive nonlinear index of refraction in the wavelength used for micromachining. A decrease in the waveguide loss of approximately four times was observed for the sample doped with Fe in comparison to the other ones, which may be associated with the change in the optical gap energy.

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

    SciTech Connect

    Nouri-Zonoz, M. [Department of Physics, University of Tehran, North Karegar Avenue, Tehran 14395-547 (Iran, Islamic Republic of); School of Astronomy and Astrophysics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531 Tehran (Iran, Islamic Republic of); Nazari, B. [Department of Physics, University of Tehran, North Karegar Avenue, Tehran 14395-547 (Iran, Islamic Republic of)

    2010-08-15

    In 1+3 (threading) formulation of general relativity spacetime behaves analogous to a medium with a specific index of refraction with respect to the light propagation. Accepting the reality of zero-point energy, through the equivalence principle, we elevate this analogy to the case of virtual photon propagation in a quantum vacuum in a curved background spacetime. Employing this new idea (conjecture) one could examine the response of vacuum energy to the presence of a weak stationary gravitational field in its different quantum field theoretic manifestations such as Casimir effect and Lamb shift. As an evidence in favor of the proposed conjecture, employing quantum field theory in curved spacetime, we explicitly calculate the effect of a weak static gravitational field on virtual massless scalar particles in a Casimir apparatus. It is shown that, as expected from the proposed conjecture, both the frequency and renormalized energy of the virtual scalar field are affected by the gravitational field through its index of refraction. Generalizations to weak stationary spacetimes and virtual photons are also discussed.

  20. Method of time resolved refractive index measurements of x-ray laser heated solids

    SciTech Connect

    Williams, G. O.; Kuenzel, S.; Fajardo, M. [GoLP/Instituto de Plasmas e Fusao Nuclear-Laboratorio Associado, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Chung, H.-K. [Atomic and Molecular Data Unit, Nuclear Data Section, IAEA, PO Box 100, A-1400 Vienna (Austria); Vinko, S. M. [Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Sardinha, A. B. [GoLP/Instituto de Plasmas e Fusao Nuclear-Laboratorio Associado, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Laboratoire d'Optique Appliquee, Ecole Nationale Superieure de Technique Avancees, Ecole Polytechnique, CNRS UMR7639, Chemin de la Huniere, 91761 Palaiseau Cedex (France); Zeitoun, Ph. [Laboratoire d'Optique Appliquee, Ecole Nationale Superieure de Technique Avancees, Ecole Polytechnique, CNRS UMR7639, Chemin de la Huniere, 91761 Palaiseau Cedex (France)

    2013-04-15

    With the advent of new x-ray light-sources worldwide, the creation of dense, uniformly heated plasma states arising from intense x-ray irradiation of solids has been made possible. In the early stages of x-ray solid heating, before significant hydrodynamic motion occurs, the matter exists in a highly non-equilibrium state. A method based on wavefront sensing is proposed to probe some of the fundamental properties of these states. The deflection and absorption of a high harmonic probe beam propagated through the plasma can be measured with a wavefront sensor, and allow for the determination of the complex refractive index (RI) of the plasma, giving a 2D map of the optical properties as function of time in a pump-probe arrangement. A solid heating model has been used to estimate the expected temperatures of x-ray heated thin foils, and these temperatures are used in three separate models to estimate the changes in the refractive index. The calculations show the changes induced on an extreme ultra-violet (XUV) probe beam by a solid density thin foil plasma are significant, in terms of deflection angle and absorption, to be measured by already existing XUV Hartmann wavefront sensors. The method is applicable to a wide range of photon energies in the XUV (10 s to several 100 s of eV) and plasma parameters, and can add much needed experimental data to the fundamental properties of such dense plasma states.

  1. PIV Measurements of Turbulent Flow Over a Permeable Wall using a Refractive-Index Matching Approach

    NASA Astrophysics Data System (ADS)

    Kim, T.; Blois, G.; Best, J. L.; Christensen, K. T.

    2013-11-01

    Turbulent flows over permeable walls occur in a variety of natural environments and engineering applications. Unlike classical and widely-studied flows over impermeable walls, the peculiar dynamics of flow generated by permeable walls are poorly understood. Early studies suggest that the well-known higher energy dissipation induced by permeability (as compared to impermeable walls with similar roughness) can be explained by unveiling the flow interactions within the transition layer that forms at the interface between the overlying flow and the permeable wall. To overcome the challenges associated with quantifying the flow character both above and within a permeable wall, a Refractive-Index-Matching (RIM) approach was employed. Doing so facilitated optical access to the fluid flowing through the permeable wall, thus yielding direct PIV pore-space flow measurements within the transition layer. The permeable wall was formed by packing acrylic spheres in a cubic arrangement and was then immersed in an aqueous solution of sodium iodide at a concentration and temperature that ensured accurate refractive index match with the wall. Measurements were focused on the flow across the wall interface and the turbulent attributes of these surface-subsurface interactions were detailed.

  2. Simultaneous measurement of refractive index and temperature based on intensity demodulation using matching grating method

    NASA Astrophysics Data System (ADS)

    Qi, Liang; Zhao, Chun-Liu; Kang, Juan; Jin, Yongxing; Wang, Jianfeng; Ye, Manping; Jin, Shangzhong

    2013-07-01

    A solution refractive index (SRI) and temperature simultaneous measurement sensor with intensity-demodulation system based on matching grating method were demonstrated. Long period grating written in a photonic crystal fiber (LPG-PCF), provides temperature stable and wavelength dependent optical intensity transmission. The reflective peaks of two fiber Bragg gratings (FBGs), one of which is etched then sensitive to both SRI and temperature, another (FBG2) is only sensitive to temperature, were located in the same linear range of the LPG-PCF's transmission spectrum. An identical FBG with FBG2 was chosen as a matching FBG. When environments (SRI and temperature) change, the wavelength shifts of the FBGs are translated effectively to the reflection intensity changes. By monitoring output lights of unmatching and matching paths, the SRI and temperature were deduced by a signal processing unit. Experimental results show that the simultaneous refractive index and temperature measurement system work well. The proposed sensor system is compact and suitable for in situ applications at lower cost.

  3. Coherent control of refractive index in far-detuned {Lambda} systems

    SciTech Connect

    O'Brien, Chris; Anisimov, Petr M.; Rostovtsev, Yuri; Kocharovskaya, Olga [Department of Physics, Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843-4242 (United States); Department of Physics and Astronomy, Hearne Institute for Theoretical Physics, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Department of Physics, University of North Texas, Denton, Texas 76203 (United States); Department of Physics, Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843-4242 (United States) and Institute of Applied Physics, RAS, Nizhniy Novgorod, RU-603120 (Russian Federation)

    2011-12-15

    Enhancement and control of the index of refraction in a mixture of two three-level atomic species that form a pair of far-detuned {Lambda} schemes under two-photon resonance has been studied. We employ the density-matrix approach to properly take population relaxation into account and to describe the interaction of each {Lambda} system with the electromagnetic fields. Both {Lambda} systems are driven by a corresponding far-detuned coherent field at one atomic transition and are probed by the same weak field. In the dressed-state basis, it represents a superposition of effective two-level subsystems with the positions, widths, and amplitudes of the resonances controlled by the driving fields and allows for efficient control of the susceptibility of the total system; leading to refractive index (RI) enhancement with vanishing absorption in the absence of amplification. We analyze the experimental implementation of such a system in a cell of Rb atoms with a natural abundance of isotopes. An upper limit estimate of the RI enhancement is obtained.

  4. Large refractive index in BiFeO3-BiCoO3 epitaxial films

    NASA Astrophysics Data System (ADS)

    Shima, Hiromi; Nishida, Ken; Yamamoto, Takashi; Tadokoro, Toshiyasu; Tsutsumi, Koichi; Suzuki, Michio; Naganuma, Hiroshi

    2013-05-01

    Rhombohedral (R-) and tetragonal (T-) Bi(Fe,Co)O3 (BFCO) films were epitaxially grown on the SrTiO3 (100) substrates, and the optical properties of the BFCO films were evaluated by spectroscopic ellipsometry. It was revealed that the refractive indexes of R- and T-BFCO epitaxial films were 2.93 and 2.86 at wavelength of 600 nm, and 2.65 and 2.59 at 1550 nm, respectively, which are comparable to the pure BiFeO3. The refractive index of the R-BFCO film was totally larger than that of the T-BFCO film; it might be caused by structural strain and local symmetry breaking. It was confirmed that the extinction coefficients of both films were almost zero at wavelengths larger than 600 nm. In addition, the optical band gaps of the R- and T-BFCO films were estimated to be 2.78 and 2.75 eV, respectively. It can expect that the BFCO film has a possibility to use optical-magnetic field sensor working at room temperature.

  5. Light sheet microscopy of cleared mouse brains: aberrations effects caused by refractive index mismatch

    NASA Astrophysics Data System (ADS)

    Silvestri, Ludovico; Sacconi, Leonardo; Pavone, Francesco S.

    2013-06-01

    Fluorescence light sheet microscopy has known a true renaissance in the last years. In fact, since optical sectioning is achieved in a wide-field detection scheme, this technique allows high resolution three-dimensional imaging with high frame rate. Light sheet microscopy is therefore an ideal candidate for reconstructing macroscopic specimens with micron resolution: coupled with clearing protocols based on refractive index matching it has been exploited to image entire mouse brains without physical sectioning. Use of clearing protocols poses several challenges to light sheet microscopy. First of all, residual light scattering inside the tissue expands the excitation light sheet, leading to the excitation of out-of-focus planes, and thus frustrating the very principle of light sheet illumination. To reject out-of-focus contributions we recently coupled light sheet illumination with confocal detection, achieving significant contrast enhancement in real time. Another issue which often arises when working with clearing agents is the refractive index mismatch between the clearing and the medium objective design medium. This introduces severe spherical aberration, which leads to broadening of the point spread function and to a strong reduction in its peak value: When imaging deep (several mm) inside macroscopic specimens, the signal can be reduced by more than an order of magnitude. We investigated the possibility of correcting such spherical aberration by introducing extra optical devices in the detection path.

  6. Graded refractive index optics based on dual-layer ultrathin films: theory, design and applications in integrated photonics

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Lim, Kim Peng; Ng, Doris K. T.

    2015-02-01

    This paper presents an overview of graded refractive index optics based on dual-layer ultrathin film technology and its application in integrated photonics as an on-chip lens for optical coupling of nano-waveguide. The theoretical derivation and discussion shows the equivalence between the dual-layer ultrathin film and a negative birefringent thin film and the influence of thin film thickness and light incident angle on this equivalence. For experimental verification, a set of dual-layer ultrathin films of titanium dioxide (TiO2) and aluminium oxide (Al2O3) are deposited on silicon with different volume fractions. Characterization of refractive index and reflectance shows a good agreement between the experiment and theoretical design, and suggests the graded refractive index profile can be achieved via varying the volume faction of the dual-layer ultrathin film stack. As an application example, a graded refractive index lens with aberration-correction based on the above dual-layer thin film stack is designed and optimized for optical coupling between silicon waveguide and optical fiber. The optical design indicates the multilayer thin-film stack with a proper graded refractive index profile can serve as the passivation cladding on top of silicon waveguide but collimate the light at the waveguide ends for optical coupling to fiber with an estimated efficiency ~89%.

  7. Long-period gratings in photonic crystal fibers for sensing of external refractive index change and macro-bending

    Microsoft Academic Search

    Zonghu He; Yinian Zhu; Ryan T. Bise; Henry Du

    2006-01-01

    Long-period gratings (LPGs) have been fabricated in endlessly single mode photonic crystal fibers (ESM-PCFs) utilizing focused CO2 laser irradiation and residual stress relaxation technique. The responses of the ESM-PCF-LPGs to external refractive index and applied bending curvature have been investigated. As compared with the conventional fiber-based LPGs inscribed under the same condition, the ESM-PCF-LPGs exhibit higher sensitivity to external refractive

  8. Colossal Light-Induced Refractive-Index Modulation for Neutrons in Holographic Polymer-Dispersed Liquid Crystals

    SciTech Connect

    Fally, Martin; Ellabban, Mostafa A. [Nonlinear Physics Group, Faculty of Physics, Universitaet Wien, Boltzmanngasse 5, A-1090 Vienna (Austria); Drevensek-Olenik, Irena [Nonlinear Physics Group, Faculty of Physics, Universitaet Wien, Boltzmanngasse 5, A-1090 Vienna (Austria); Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, and J. Stefan Institute, Jamova 39, SI 1001 Ljubljana (Slovenia); Pranzas, Klaus P.; Vollbrandt, Juergen [GKSS Forschungszentrum, D-21502 Geesthacht (Germany)

    2006-10-20

    We report strong diffraction of cold neutrons from an only 30 {mu}m thick holographic polymer-dispersed liquid crystal (H-PDLC) transmission grating. The light-induced refractive-index modulation for neutrons is about 10{sup -6}, i.e., nearly 2 orders of magnitude larger than in the best photo-neutron-refractive materials probed up to now. This makes H-PDLCs a promising candidate for fabricating neutron-optical devices.

  9. Thermal analysis, spectral characterization and refractive index studies of lithium doped PbO-ZnO-B{sub 2}O{sub 3} glass

    SciTech Connect

    Rajaramakrishna, R.; Lakshmikantha, R.; Anavekar, R. V. [Department of Physics, Bangalore University, Jnanabarthi campus, Bangalore - 560056 (India); Department of Physics, K.L.E.Society's S. N. College, Bangalore - 560 010 (India); Department of Physics, Bangalore University, Jnanabarthi campus, Bangalore - 560056 (India)

    2012-06-05

    Lithium containing lead zinc borate glasseshave been prepared by melt quenching technique. X-ray diffraction reveals the amorphous nature of the glass. Differential scanning calorimeter (DSC) study was carried out in the temperature range RT to 600 deg. C temperature and found glass transition temperature of these glasses decreases with increase in inter substitution of Pb and Zn lithium content. PZB glasses are stable, IR spectra of these glasses show characteristics band originating from borate groups namely [BO{sub 3}] [BO{sub 4}]and B-O-B stretching vibrations respectively, and found that structure is not affected with effect of lithium content. Refractive index of these glasses are in the range of 1.47 with increasing lithium content refractive index decreases indicating decrease in scattering of light.

  10. Thermal analysis, spectral characterization and refractive index studies of lithium doped PbO-ZnO-B2O3 glass

    NASA Astrophysics Data System (ADS)

    Rajaramakrishna, R.; Lakshmikantha, R.; Anavekar, R. V.

    2012-06-01

    Lithium containing lead zinc borate glasseshave been prepared by melt quenching technique. X-ray diffraction reveals the amorphous nature of the glass. Differential scanning calorimeter (DSC) study was carried out in the temperature range RT to 600°C temperature and found glass transition temperature of these glasses decreases with increase in inter substitution of Pb and Zn lithium content. PZB glasses are stable, IR spectra of these glasses show characteristics band originating from borate groups namely [BO3] [BO4]and B-O-B stretching vibrations respectively, and found that structure is not affected with effect of lithium content. Refractive index of these glasses are in the range of 1.47 with increasing lithium content refractive index decreases indicating decrease in scattering of light.

  11. Experimental analysis of distributed pump absorption and refractive index changes in Yb-doped fibers using acousto-optic interaction.

    PubMed

    Alcusa-Sáez, E P; Díez, A; Andrés, M V

    2015-03-01

    In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C band in a single-mode ytterbium-doped optical fiber under 980 nm pumping. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. The electronic contribution to the refractive index change is quantified from the wavelength shift. Using a time-resolved acousto-optic method, we investigate the distribution of pump absorption, and the resulting refractive index change profile, along sections of ytterbium-doped fiber exceeding 1 m long under different pump power levels. PMID:25723408

  12. Enhanced vibrational spectroscopy, intracellular refractive indexing for label-free biosensing and bioimaging by multiband plasmonic-antenna array.

    PubMed

    Chen, Cheng-Kuang; Chang, Ming-Hsuan; Wu, Hsieh-Ting; Lee, Yao-Chang; Yen, Ta-Jen

    2014-10-15

    In this study, we report a multiband plasmonic-antenna array that bridges optical biosensing and intracellular bioimaging without requiring a labeling process or coupler. First, a compact plasmonic-antenna array is designed exhibiting a bandwidth of several octaves for use in both multi-band plasmonic resonance-enhanced vibrational spectroscopy and refractive index probing. Second, a single-element plasmonic antenna can be used as a multifunctional sensing pixel that enables mapping the distribution of targets in thin films and biological specimens by enhancing the signals of vibrational signatures and sensing the refractive index contrast. Finally, using the fabricated plasmonic-antenna array yielded reliable intracellular observation was demonstrated from the vibrational signatures and intracellular refractive index contrast requiring neither labeling nor a coupler. These unique features enable the plasmonic-antenna array to function in a label-free manner, facilitating bio-sensing and imaging development. PMID:24836017

  13. Giant refractive-index enhancement in dispersive polaritonic band-gap and photonic band-gap materials

    SciTech Connect

    Singh, Mahi R. [Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7 (Canada)

    2004-02-01

    A theory for the refractive-index enhancement due to quantum coherence and interference has been developed in dispersive polaritonic and photonic band-gap materials doped with an ensemble of noninteracting three-level atoms. Quantum coherence is introduced by driving the atoms with a coherent monochromatic laser field. The real and the imaginary parts of the susceptibility have been calculated by using the master equation and the Laplace transform methods. It is found that the energy gap in these materials plays an important role in the refractive-index enhancement. Numerical simulations for the real and the imaginary parts of susceptibility are performed for SiC as a function of the probe laser frequency. It is found that there is a giant refractive-index enhancement with vanishing absorption when the resonance frequencies lie near the lower band edge.

  14. Enhanced interferometric methods for investigation of refractive index distribution changes along tapering structure in photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Jaroszewicz, Leszek R.; Kujawi?ska, Ma?gorzata; Stasiewicz, Karol; Siwicki, Bart?omiej; Wójcik, S?awomir; Mar?, Pawe?

    2010-09-01

    The paper presents the analysis and enhancements of interferometric methods which may provide better quality projections for tomographic, in-line determination of geometry and refractive index distribution changes along classical as well as photonic crystal fiber tapering structure. The method and system provides high optical resolution and sensitivity for determination of refractive index changes. It also provides the possibility of investigation of structures with and without circular symmetry of refractive index distribution. In the paper the interferometric tomography method in Mach-Zehnder interferometer configuration is applied and the measurements of classical and photonics crystal fibers are presented. The analysis of future use of in-line digital holographic method coupled with a variety of techniques for enhanced phase reconstruction is performed.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  16. Substrate temperature effect on the refractive index and a two-step film method to detect small inhomogeneities in optical films

    Microsoft Academic Search

    Fachun Lai; Ming Li; Kang Chen; Haiqian Wang; Yizhou Song; Yousong Jiang

    2005-01-01

    Nb2O5 films were deposited by a reactive magnetron sputtering technique. The average refractive index was found to increase with the rise of substrate temperature. Modulated interference transmittance spectra were observed in the two-step films, which were prepared by stopping the deposition process in the middle of the designed sputtering time, and then, after a full cooling down to room temperature,

  17. Surface plasmon resonance structures in spectral interrogation using high refractive index prism materials for sensing of different amino acids

    NASA Astrophysics Data System (ADS)

    Ghosh, Sharmila; Ray, Mina

    2014-11-01

    A prism coupler-based nano-plasmonic sensor consisting of a high refractive index (RI) prism (2S2G-prism, LASF9-prism), gold (Au) metal film, and different amino acids as the dielectric sample is used for sensing in attenuated total internal reflection mode. An additional semiconductor (silicon) nano-layer over the gold surface has been used for increasing the stability and sensitivity of the surface plasmon resonance sensor. A comparative analysis of performance of the nano-plasmonic sensors in the spectral regime using these two high RI prism materials with an additional semiconductor nano-layer has been presented. The sensing performance of the proposed nano-plasmonic sensors in terms of evanescent field enhancement, spectral sensitivity, detection accuracy, figure of merit, and Q-factor with different amino acid samples has been discussed along with supporting theoretical simulations in a MATLAB environment.

  18. Threshold pump intensity effect on the refractive index changes in InGaN SQD: Internal constitution and size effects

    NASA Astrophysics Data System (ADS)

    El Ghazi, Haddou; A John Peter

    2015-04-01

    In the present paper, internal composition and size-dependent threshold pump intensity effects on on-center impurity-related linear, third-order nonlinear and total refractive index changes are investigated in wurtzite (In,Ga)N/GaN unstrained spherical quantum dot. The calculation is performed within the framework of parabolic band and single band effective-mass approximations using a combination of Quantum Genetic Algorithm (QGA) and Hartree-Fock-Roothaan (HFR) method. According to the results obtained, (i) a significant red-shift (blue shift) is obtained as the dot size (potential barrier) increases and (ii) a threshold optical pump intensity depending strongly on the size and the internal composition is obtained which constitutes the limit between two behaviors.

  19. Enhanced refractive index sensor using a combination of a long period fiber grating and a small core singlemode fiber structure

    NASA Astrophysics Data System (ADS)

    Wu, Qiang; Chan, Hai Ping; Yuan, Jinhui; Ma, Youqiao; Yang, Minwei; Semenova, Yuliya; Yan, Binbin; Wang, Pengfei; Yu, Chongxiu; Farrell, Gerald

    2013-09-01

    An enhanced refractive index (RI) sensor based on a combination of a long period fiber grating (LPG) and a small core singlemode fiber (SCSMF) structure is proposed and developed. Since the LPG and SCSMF transmission spectra experience a blue and a red shift respectively as the surrounding RI (SRI) increases, the sensitivity is improved by measuring the separation between the resonant wavelengths of the LPG and SCSMF structures. Experimental results show that the sensor has a sensitivity of 1028 nm/SRI unit in the SRI range from 1.422 to 1.429, which is higher than individual sensitivities of either structure alone used in the experiment. Experimental results agree well with simulation results.

  20. The complex refractive index of atmospheric and model humic-like substances (HULIS) retrieved by a cavity ring down aerosol spectrometer (CRD-AS).

    PubMed

    Dinar, E; Riziq, A Abo; Spindler, C; Erlick, C; Kiss, G; Rudich, Y

    2008-01-01

    Atmospheric aerosols absorb and reflect solar radiation causing surface cooling and heating of the atmosphere. The interaction between aerosols and radiation depends on their complex index of refraction, which is related to the particles' chemical composition. The contribution of light absorbing organic compounds, such as HUmic-LIke Substances (HULIS) to aerosol scattering and absorption is among the largest uncertainties in assessing the direct effect of aerosols on climate. Using a Cavity Ring Down Aerosol Spectrometer (CRD-AS), the complex index of refraction of aerosols containing HULIS extracted from pollution, smoke, and rural continental aerosols, and molecular weight-fractionated fulvic acid was measured at 390 nm and 532 nm. The imaginary part of the refractive index (absorption) substantially increases towards the UV range with increasing molecular weight and aromaticity. At both wavelengths, HULIS extracted from pollution and smoke particles absorb more than HULIS from the rural aerosol. Sensitivity calculations for a pollution-type aerosol containing ammonium sulfate, organic carbon (HULIS), and soot suggests that accounting for absorption by HULIS leads in most cases to a significant decrease in the single scattering albedo and to a significant increase in aerosol radiative forcing efficiency, towards more atmospheric absorption and heating. This indicates that HULIS in biomass smoke and pollution aerosols, in addition to black carbon, can contribute significantly to light absorption in the ultraviolet and visible spectral regions. PMID:18214110

  1. Active suppression of air refractive index fluctuation using a Fabry-Perot cavity and a piezoelectric volume actuator

    SciTech Connect

    Banh, Tuan Quoc; Ohkubo, Yuria; Murai, Yoshinosuke; Aketagawa, Masato

    2011-01-01

    Air refractive index fluctuation ({Delta}n{sub air}) is one of the largest uncertainty sources in precision interferometry systems that require a resolution of nanometer order or less. We introduce a method for the active suppression of {Delta}n{sub air} inside a normal air-environment chamber using a Fabry-Perot cavity and a piezoelectric volume actuator. The temporal air refractive index (n{sub air}) at a local point is maintained constant with an expanded uncertainty of {approx}4.2x10{sup -9} (k=2), a sufficiently low uncertainty for precise measurements unaffected by {Delta}n{sub air} to be made inside a chamber.

  2. Superlensing effect for surface acoustic waves in a pillar-based phononic crystal with negative refractive index

    NASA Astrophysics Data System (ADS)

    Addouche, Mahmoud; Al-Lethawe, Mohammed A.; Choujaa, Abdelkrim; Khelif, Abdelkrim

    2014-07-01

    We demonstrate super resolution imaging for surface acoustic waves using a phononic structure displaying negative refractive index. This phononic structure is made of a monolithic square lattice of cylindrical pillars standing on a semi-infinite medium. The pillars act as acoustic resonator and induce a surface propagating wave with unusual dispersion. We found, under specific geometrical parameters, one propagating mode that exhibits negative refraction effect with negative effective index close to -1. Furthermore, a flat lens with finite number of pillars is designed to allow the focusing of an acoustic point source into an image with a resolution of ?/3, overcoming the Rayleigh diffraction limit.

  3. Diffractionless beam in free space with adiabatic changing refractive index in a single mode tapered slab waveguide

    PubMed Central

    Tsai, Chang-Ching; Vinegoni, Claudio; Weissleder, Ralph

    2009-01-01

    We propose a novel design to produce a free space diffractionless beam by adiabatically reducing the difference of the refractive index between the core and the cladding regions of a single mode tapered slab waveguide. To ensure only one propagating eigenmode in the adiabatic transition, the correlation of the waveguide core width and the refractive index is investigated. Under the adiabatic condition, we demonstrate that our waveguide can emit a diffractionless beam in free space up to 500 micrometers maintaining 72% of its original peak intensity. The proposed waveguide could find excellent applications for imaging purposes where an extended depth of field is required. PMID:19997414

  4. SPR based fiber optic sensor for refractive index sensing with enhanced detection accuracy and figure of merit in visible region

    NASA Astrophysics Data System (ADS)

    Mishra, Akhilesh K.; Mishra, Satyendra K.; Gupta, Banshi D.

    2015-06-01

    We, theoretically, propose a surface plasmon resonance (SPR) based indium tin oxide (ITO)-silver (Ag) coated fiber optic sensing probe for refractive index sensing in visible regime of the electromagnetic spectrum. A comparative study of ITO+Ag coated probe with Ag coated probe and with ITO coated probe using their respective optimized film thicknesses is carried out. We show that the proposed probe is endowed with the better sensitivity characteristic of ITO and better detection accuracy (DA) characteristic of Ag, and can sense change in refractive index with enhanced DA and figure of merit (FOM) in the visible region.

  5. Superlensing effect for surface acoustic waves in a pillar-based phononic crystal with negative refractive index

    SciTech Connect

    Addouche, Mahmoud, E-mail: mamoud.addouche@femto-st.fr; Al-Lethawe, Mohammed A., E-mail: mohammed.abdulridha@femto-st.fr; Choujaa, Abdelkrim, E-mail: achoujaa@femto-st.fr; Khelif, Abdelkrim, E-mail: abdelkrim.khelif@femto-st.fr [Institut FEMTO-ST, Université de Franche-Comté, CNRS, 32 Avenue de l'Observatoire, 25044 Besançon Cedex (France)

    2014-07-14

    We demonstrate super resolution imaging for surface acoustic waves using a phononic structure displaying negative refractive index. This phononic structure is made of a monolithic square lattice of cylindrical pillars standing on a semi-infinite medium. The pillars act as acoustic resonator and induce a surface propagating wave with unusual dispersion. We found, under specific geometrical parameters, one propagating mode that exhibits negative refraction effect with negative effective index close to ?1. Furthermore, a flat lens with finite number of pillars is designed to allow the focusing of an acoustic point source into an image with a resolution of (?)/3 , overcoming the Rayleigh diffraction limit.

  6. Contribution of the crystalline lens gradient refractive index to the accommodation amplitude in non-human primates: In vitro studies

    PubMed Central

    Maceo, Bianca M.; Manns, Fabrice; Borja, David; Nankivil, Derek; Uhlhorn, Stephen; Arrieta, Esdras; Ho, Arthur; Augusteyn, Robert C.; Parel, Jean-Marie

    2012-01-01

    The purpose of this study was to determine the contribution of the gradient refractive index to the change in lens power in hamadryas baboon and cynomolgus monkey lenses during simulated accommodation in a lens stretcher. Thirty-six monkey lenses (1.4–14.1 years) and twenty-five baboon lenses (1.8–28.0 years) were stretched in discrete steps. At each stretching step, the lens back vertex power was measured and the lens cross-section was imaged with optical coherence tomography. The radii of curvature for the lens anterior and posterior surfaces were calculated for each step. The power of each lens surface was determined using refractive indices of 1.365 for the outer cortex and 1.336 for the aqueous. The gradient contribution was calculated by subtracting the power of the surfaces from the measured lens power. In all lenses, the contribution of the surfaces and gradient increased linearly with the amplitude of accommodation. The gradient contributes on average 65 ± 3% for monkeys and 66 ± 3% for baboons to the total power change during accommodation. When expressed in percent of the total power change, the relative contribution of the gradient remains constant with accommodation and age in both species. These findings are consistent with Gullstrand’s intracapsular theory of accommodation. PMID:22131444

  7. Refractive-index based tomosynthesis using dark-field imaging optics

    NASA Astrophysics Data System (ADS)

    Sunaguchi, N.; Yuasa, T.; Ichihara, S.; Huo, Q.; Sakai, M.; Wu, Y.; Shimao, D.; Ando, M.

    2013-03-01

    Tomosynthesis (TS) is a pseudo-3-dimensional image reconstruction method to recover depth-resolved information using restricted number of projections. In this research, refraction index based TS imaging using dark-field imaging (DFI) optics is proposed and biomedical soft tissues were imaged in low dose exposure. By a single exposure of an object, two projected images are obtained from a Laue-case analyzer of DFI. Calculating the both images refraction component is deduced, while two exposures are needed in DEI (diffraction enhanced imaging). Thus the measurement time and the radiation dose in DFI are half of DEI. In addition, the proposed reconstruction algorithm, derived from the quantitative relationship in measurement process, allows high contrast tomographic imaging in spite of one order smaller number of projections for CT (computed tomography). To demonstrate the proposed imaging protocol efficacy, an ex-vivo excised tissue of human lung were imaged using a system constructed at the vertical wiggler beamline at PF-BL14C at KEK. TS image is successfully delineated high quality soft tissue structures comparable to CT.

  8. Aerosol size distribution and refractive index from bistatic lidar angular scattering measurements in the surface layer

    SciTech Connect

    Pandithurai, G.; Devara, P.C.S.; Raj, P.E.; Sharma, S. [Indian Inst. of Tropical Meteorology, Pune (India)] [Indian Inst. of Tropical Meteorology, Pune (India)

    1996-05-01

    The results of an inversion method by iteration for determining the aerosol size distribution and the refractive index of atmospheric aerosols in the surface layer from bistatic lidar angular scattering measurements, followed by a brief description of the experimental and data retrieval techniques are presented. The continuous wave, bistatic Argon ion lidar at the Indian Institute of Tropical Meteorology (IITM), Pune (18{degree}31{prime}N, 73{degree}51{prime}E, 559 m AMSL), India has been used for the measurements. Results of the analysis of 420 samples collected over a 7 years` period indicate mean value of size and refractive indices of 4.0 and 1.6, respectively, with greater fraction of larger particles during premonsoon while smaller particles during post-monsoon months at the lidar site. The retrieved aerosol parameters are compared with those determined from spectroradiometer observations at the same site. The results are found well in agreement with those obtained previously by the authors using the library search method. The above observations of angular distribution of scattered intensity are used with an aerosol model to infer the dominant type of aerosols present in the environment in and around the experimental station.

  9. Metamaterials with tunable refractive index fabricated from amorphous ferromagnetic microwires and optical Magnus effect

    NASA Astrophysics Data System (ADS)

    Ivanov, Andrey; Vedyayev, Anatoly; Galkin, Vladimir; Shalygin, Alexander; Ivanov, Valery

    2009-03-01

    For homogeneous NPVM (negative phase--velocity mediums) [V. G. Veselago, Soviet Physics - Uspekhi 10 (1968) 509; T. G. Mackay, A. Lakhtakia, Phys. Rev. E 69 (2004) 026602] anomalous effects such as negative refraction, light pressure, Doppler shift, Cherenkov-Vavilov radiation, Goos-Hanchen effect have been discovered in different frequency ranges. In this presentation the optical circular polarized effect is calculated for inhomogeneous mediums (optical Magnus effect) and it is shown that it is anomalous in NPVM with respect to ``right-handed'' materials. The proposed metamaterials fabricated from glass coated amorphous ferromagnetic Co-Fe-Cr-B-Si microwires are shown to exhibit a negative refractive index for electromagnetic waves over scale of GHz frequencies [A.V. Ivanov, A.N. Shalygin, A.V. Vedyayev, V.A. Ivanov, JETP Letters 85 (2007) 565]. The magnetostatic interaction between microwires has been taken into account. The phase and group velocities in proposed metamaterial have been calculated. The ratio of thereof depends monotonically on the size of the microwires. Optical properties of such metamaterials are tunable by an external magnetic field and mechanical stress.

  10. High temperature nano-coated electric-arc-induced long-period gratings working at the dispersion turning point for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Debowska, Anna K.; Smietana, Mateusz; Mikulic, Predrag; Bock, Wojtek J.

    2014-08-01

    In this paper we present for the first time electric-arc-induced long-period gratings (LPGs) working at the dispersion turning point (DTP) in the wavelength range of about 1550 nm. The DTP is achieved by reducing the grating period down to about 190 µm. In contrast to LPGs fabricated with the typical UV laser-based method, arc-induced gratings show high thermal stability and excellent long-term performance. These advantages make it possible to coat the LPGs using thin-film deposition methods, which require high temperatures. We present the effect of thin silicon nitride (SiNx) overlay deposited by the radio-frequency plasma-enhanced chemical vapor deposition (RF PECVD) method. This technique increased the refractive index sensitivity of the LPGs from 400-700 nm/refractive index unit (RIU) to 887-2146 nm/RIU.

  11. NONLINEAR OPTICAL PHENOMENA: Changes in the refractive index of an Nd:YAG laser crystal on excitation of the Nd3+ ions

    NASA Astrophysics Data System (ADS)

    Antipov, Oleg L.; Kuzhelev, A. S.; Luk'yanov, A. Yu; Zinov'ev, A. P.

    1998-10-01

    A polarising interferometer was used to investigate changes in the refractive index of an Nd:YAG laser crystal associated with changes in the populations of the electronic energy levels characterised by different polarisabilities. The study was carried out on diode-pumped crystals as well as on crystals which were flashlamp-pumped under conditions of saturation of the gain experienced by the optical beam. The changes in the refractive index depended nonlinearly on the pump power. The ratio of the real and imaginary parts of the nonlinear susceptibility of an Nd:YAG laser amplifier was determined: this ratio rose from 0.2 to 1.2 when the gain increased from 0.2 to 0.45 cm-1 .

  12. Birefringent microfiber-based fiber loop mirrors for tunable filters and refractive index sensors

    NASA Astrophysics Data System (ADS)

    Jin, Wa; Xuan, Haifeng; Jin, Wei

    2013-05-01

    Highly birefringent (Hi-Bi) microfiber-based fiber loop mirrors (FLMs) were studied for tunable comb filters and refractive index (RI) sensors. RI sensitivity of up to 15,441 nm/RIU was experimentally demonstrated for the RI sensors and, for the tunable filter a thermal tuning coefficient of ~-2.35nm/°C was obtained for temperature from 20 to 90°C when it was immersed into water. The use of two cascaded Hi-Bi micro-tapers within a Sagnac loop allows more flexibility in controlling the transmission/reflection spectraums of the FLM. The length of the tapered Hi-Bi microfibers is on the order of centimeters, two orders of magnitude shorter than the conventional Hi-Bi fiber-based devices.

  13. Application of matching liquid on the refractive index measurement of biotissue: A theoretical and experimental study

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    The application of matching liquid on the measurement of the refractive index (RI) of biotissue using total internal reflection (TIR) method is investigated in detail. A theoretical model describing samples with different absorbing and scattering ability is given based on Fresnel formula. The theoretical calculation is verified by experimental results of three simulation samples (transparent plexiglass, white plexiglass and ZB3 glass) and cedar wood oil as the matching liquid. Reflectance curves of porcine tissue samples were recorded and systematically studied using two kinds of matching liquid (cedar wood oil and adipose oil) at the incident of TE and TM wave, respectively. Method for proper selection of matching liquid under different conditions is discussed.

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

    E-print Network

    M. Consoli; E. Costanzo

    2006-04-04

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

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

    PubMed

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

    2013-05-01

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

  16. Highly Sensitive Detection of Naphthalene in Solvent Vapor Using a Functionalized PBG Refractive Index Sensor

    PubMed Central

    Girschikofsky, Maiko; Rosenberger, Manuel; Belle, Stefan; Brutschy, Malte; Waldvogel, Siegfried R.; Hellmann, Ralf

    2012-01-01

    We report an optical refractive index sensor system based on a planar Bragg grating which is functionalized by substituted ?-cyclodextrin to determine low concentrations of naphthalene in solvent vapor. The sensor system exhibits a quasi-instantaneous shift of the Bragg wavelength and is therefore capable for online detection. The overall shift of the Bragg wavelength reveals a linear relationship to the analyte concentration with a gradient of 12.5 ± 1.5 pm/ppm. Due to the spectral resolution and repeatability of the interrogation system, this corresponds to acquisition steps of 80 ppb. Taking into account the experimentally detected signal noise a minimum detection limit of 0.48 ± 0.05 ppm is deduced. PMID:22438751

  17. Elliptical-core two mode fiber sensors and devices incorporating photoinduced refractive index gratings

    NASA Technical Reports Server (NTRS)

    Greene, Jonathan A.; Miller, Mark S.; Starr, Suzanne E.; Fogg, Brian R.; Murphy, Kent A.; Claus, Richard O.; Vengsarkar, Ashish M.

    1991-01-01

    Results of experiments performed using germanium-doped, elliptical core, two-mode optical fibers whose sensitivity to strain was spatially varied through the use of chirped, refractive-index gratings permanently induced into the core using Argon-ion laser light are presented. This type of distributed sensor falls into the class of eighted-fiber sensors which, through a variety of means, weight the strain sensitivity of a fiber according to a specified spatial profile. We describe results of a weighted-fiber vibration mode filter which successfully enhances the particular vibration mode whose spatial profile corresponds to the profile of the grating chirp. We report on the high temperature survivability of such grating-based sensors and discuss the possibility of multiplexing more than one sensor within a single fiber.

  18. Temperature and surrounding refractive index insensitive cascaded long period grating chemical sensor

    NASA Astrophysics Data System (ADS)

    Korposh, S.; James, S. W.; Lee, Seung-Woo; Tatam, R. P.

    2014-05-01

    The response to temperature and refractive index (RI) of cascaded long period gratings operating at or near the phase matching turning point was studied. Temperature- and RI-induced changes of the phase of the channelled spectrum and wavelength shift of the long period grating's resonance band envelope were observed for two conditions; when the length of fibre separating the long period gratings was perturbed and when the whole length of the device was perturbed. It is shown that when the central section of the device is perturbed the phase of the channelled spectrum changes and the envelope remains fixed, while when the entire device is perturbed the phase and central wavelength of the envelope shift at the same rate. Thus measurement of changes in the channelled spectrum with respect to the centre of the resonance band envelope offers a means for developing sensors whose response is compensated for temperature and RI.

  19. Quantitative Mass Density Image Reconstructed from the Complex X-Ray Refractive Index

    PubMed Central

    Mukaide, Taihei; Iida, Atsuo; Watanabe, Masatoshi; Takada, Kazuhiro; Noma, Takashi

    2015-01-01

    We demonstrate a new analytical X-ray computed tomography technique for visualizing and quantifying the mass density of materials comprised of low atomic number elements with unknown atomic ratios. The mass density was obtained from the experimentally observed ratio of the imaginary and real parts of the complex X-ray refractive index. An empirical linear relationship between the X-ray mass attenuation coefficient of the materials and X-ray energy was found for X-ray energies between 8 keV and 30 keV. The mass density image of two polymer fibers was quantified using the proposed technique using a scanning-type X-ray microbeam computed tomography system equipped with a wedge absorber. The reconstructed mass density agrees well with the calculated one. PMID:26114770

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

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

    SciTech Connect

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

    2010-08-15

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

  2. Label free detection of DNA hybridization by refractive index tapered fiber biosensor

    NASA Astrophysics Data System (ADS)

    Zibaii, M. I.; Latifi, H.; Ghanati, E.; Gholami, M.; Hosseini, S. M.

    2010-04-01

    We demonstrate a simple refractive index sensor (RI) sensing system based on a biconical tapered optical fiber (BTOF), which is fabricated by heat pulling method, utilizing a CO2 laser. In this work we explore the application of these sensors for the detection of label free single stranded DNA (ssDNA) in real time. During the experiment, the target ssDNA did not need to be labeled with a fluorescent tag, which is expensive and complicated. The change in output optical transmission of the tapered fiber was recorded for Poly-L-Lysine (PLL) coating, ssDNA probe immobilization and hybridization. The result indicated that due to the hybridization with the complementary target ssDNA on the tapered surface, the RI of surrounding medium changes which leads to changes in the characteristics of the tapered region and change in the output power of the sensor.

  3. Observation of the waveguide resonance in a periodically patterned high refractive index broadband antireflection coating.

    PubMed

    Stenzel, O; Wilbrandt, S; Chen, X; Schlegel, R; Coriand, L; Duparré, A; Zeitner, U; Benkenstein, T; Wächter, C

    2014-05-10

    Grating waveguide structures have been prepared by the deposition of a high refractive index broadband antireflection coating onto a patterned fused silica substrate. Aluminum oxide and hafnium oxide as well as mixtures thereof have been used as coating materials. Optical reflection measurements combined with atomic force microscopy have been used to characterize the structures. Upon illumination with a TE wave, the best structure shows a narrow reflection peak located at 633 nm at an incidence angle of about 17°. The peak reflectance of that sample accounts for more than 89%. Off-resonance interference structures appear strongly suppressed in the spectrum between 450 and 800 nm because of the characteristics of the designed antireflection layer. The structure thus possesses a notch filter spectral characteristic in a broad spectral range. PMID:24922038

  4. Effect of Refractive Index Variation on Two-Wavelength Interferometry for Fluid Measurements

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R.

    1998-01-01

    Two wavelength interferometry can in principle be used to measure changes in both temperature and concentration in a fluid, but measurement errors may be large if the fluid dispersion is small. This paper quantifies the effects of uncertainties in dn/dT and dn/dC on the measured temperature and concentration when using the simple expression dn = (dn/dT)dT + (dn/dC)dC. For the data analyzed here, ammonium chloride in water from -5 to 10(exp infinity) C over a concentration range of 2-14% and for wavelengths 514.5 and 633 nm, it is shown that the gradients must be known to within 0.015% to produce a modest 10% uncertainty in the measured temperature and concentration. These results show that real care must be taken to ensure the accuracy of refractive index gradients when using two wavelength interferometry for the simultaneous measurement of temperature and concentration.

  5. Label-free characterization of white blood cells by measuring 3D refractive index maps

    E-print Network

    Yoon, Jonghee; Park, HyunJoo; Choi, Chulhee; Jang, Seongsoo; Park, YongKeun

    2015-01-01

    The characterization of white blood cells (WBCs) is crucial for blood analyses and disease diagnoses. However, current standard techniques rely on cell labeling, a process which imposes significant limitations. Here we present three-dimensional (3D) optical measurements and the label-free characterization of mouse WBCs using optical diffraction tomography. 3D refractive index (RI) tomograms of individual WBCs are constructed from multiple two-dimensional quantitative phase images of samples illuminated at various angles of incidence. Measurements of the 3D RI tomogram of WBCs enable the separation of heterogeneous populations of WBCs using quantitative morphological and biochemical information. Time-lapse tomographic measurements also provide the 3D trajectory of micrometer-sized beads ingested by WBCs. These results demonstrate that optical diffraction tomography can be a useful and versatile tool for the study of WBCs.

  6. Proposal for a broadband THz refractive-index sensor based on quantum-cascade laser arrays.

    PubMed

    Zhao, Le; Khanal, Sudeep; Wu, Chongzhao; Kumar, Sushil

    2015-02-23

    Many molecules have strong and characteristic rotational and vibrational transitions at terahertz (THz) frequencies, which makes this frequency range unique for applications in spectroscopic sensing of chemical and biological species. Here, we propose a broadband THz sensor based on arrays of single-mode QCLs, which could be utilized for sensing of the refractive-index of solids or liquids in reflection geometry. The proposed scheme does not require expensive THz detectors and consists of no movable parts. A recently developed antenna-feedback geometry is utilized to enhance optical coupling between two single-mode QCLs, which facilitates optical downconversion of the THz frequency signal to microwave regime. Arrays of THz QCLs emitting at discrete frequencies could be utilized to provide more than 2 THz of spectral coverage to realize a broadband, low-cost, and portable THz sensor. PMID:25836511

  7. Preparation of inulin-type fructooligosaccharides using fast protein liquid chromatography coupled with refractive index detection.

    PubMed

    Li, J; Cheong, K L; Zhao, J; Hu, D J; Chen, X Q; Qiao, C F; Zhang, Q W; Chen, Y W; Li, S P

    2013-09-20

    A fast protein liquid chromatography coupled with refractive index detection (FPLC-RID) method was firstly developed for preparation and purification of fructooligosaccharides with different degree of polymerization from burdock, Arctium lappa. After extraction with 60% ethanol and decolorization with MCI gel CHP20P, total fructooligosaccharides were purified on Bio-Gel P-2 column eluted with water at the flow rate of 0.3 ml/min, which was the optimized conditions. The obtained fructooligosaccharides with degree of polymerization of 3-9 were identified based on their methylation analysis, MS and NMR data. This method has the advantages of high automation, good recovery and easy performance, which could be used for preparation of FOS from other sources, as well as other targeted compounds without UV absorbance. PMID:23962565

  8. Topological insulator metamaterials with tunable negative refractive index in the optical region

    PubMed Central

    2013-01-01

    A blueshift tunable metamaterial (MM) exhibiting a double-negative refractive index based on a topological insulator (bismuth selenide, Bi2Se3) has been demonstrated in the near-infrared (NIR) spectral region. The potential of Bi2Se3 as a dielectric interlayer of the multilayer MM is explored. The optical response of elliptical nanohole arrays penetrating through Au/Bi2Se3/Au films is numerically investigated using the finite difference time domain (FDTD) method. The blueshift tuning range of the MM is as high as 370 nm (from 2,140 to 1,770 nm) after switching the Bi2Se3 between its trigonal and orthorhombic states. PMID:24330596

  9. Topological insulator metamaterials with tunable negative refractive index in the optical region.

    PubMed

    Cao, Tun; Wang, Shuai

    2013-01-01

    A blueshift tunable metamaterial (MM) exhibiting a double-negative refractive index based on a topological insulator (bismuth selenide, Bi2Se3) has been demonstrated in the near-infrared (NIR) spectral region. The potential of Bi2Se3 as a dielectric interlayer of the multilayer MM is explored. The optical response of elliptical nanohole arrays penetrating through Au/Bi2Se3/Au films is numerically investigated using the finite difference time domain (FDTD) method. The blueshift tuning range of the MM is as high as 370 nm (from 2,140 to 1,770 nm) after switching the Bi2Se3 between its trigonal and orthorhombic states. PMID:24330596

  10. Determination of complex refractive index of graphene waveguide by microfiber knot sensor

    NASA Astrophysics Data System (ADS)

    Yao, Baicheng; Wu, Yu; Cheng, Yang; Rao, Yunjiang; Gong, Yuan; Wang, Zegao; Chen, Yuanfu

    2013-09-01

    In this paper, a novel method to sensing the complex refractive index (CRI) of graphene waveguide (GW) is demonstrated. Theoretical analysis and simulated results indicate the spectral properties of evanescent wave guided by microfiber would be modulated by the GW nearby. In experiment, evanescent waves with wavelength from 1510nm to 1590nm transimitting on the surface of the GW for a few centimeters, which are launched and collected by specially designed microfiber knot sensors (MFKSs). Repeated experiments and statistic results verifie that the CRI of the GW varies from 2.59-i2.66 to 2.51-i2.84 for 1510nm-1590nm band. Such an application of MFKS is suitable not only for the GW, but also for other thin films, which would be significant for the design and research of state-of-art optical devices.

  11. Comparison of measured and calculated scattering from surface aerosols with an average, a size-dependent, and a time-dependent refractive index

    NASA Astrophysics Data System (ADS)

    Cai, Yong; Montague, Derek C.; Deshler, Terry

    2011-01-01

    Midcontinental surface aerosols have been measured at a small, minimally polluted city in summer and winter and on a nearby remote mountain in summer. Aerosol scattering, absorption, size distribution, and composition were measured using a three-wavelength nephelometer, an aethalometer, a passive cavity aerosol spectrometer, a scanning mobility particle sizer, an Aerodyne quadrupole aerosol mass spectrometer, and conventional filter systems. Size-dependent, time-dependent, and averaged refractive indices are estimated from the aerosol composition measurements and then used to calculate time-dependent aerosol scattering. The calculated scattering values show differences that are generally less than 5% on average for all three refractive indices, suggesting that the average refractive index is adequate for scattering estimations from time- or size-dependent aerosol measurements. The calculated scattering (backscattering) at 550 nm ranges from 2% less to 23% greater (11-22% smaller) than that measured. These differences decrease at 450 nm and increase at 700 nm and significantly exceed these values if optical size distribution measurements are not corrected for an appropriate index of refraction. Optimal agreement between calculated and measured scattering is achieved on 4 of the 6 days investigated in detail, if the real refractive index of the aerosol organic species ranges from 1.45 ± 0.02 at 450 nm to 1.62 ± 0.05 at 700 nm. Single-scatter albedos are also calculated and found to be in good agreement with those derived from the experimental observations, ranging from 0.79 to 0.87 in the city and constant, near 0.95, on the mountain top.

  12. Nonlinear refractive index of porcine cornea studied by z-scan and self-focusing during femtosecond laser processing.

    PubMed

    Miclea, M; Skrzypczak, U; Faust, S; Fankhauser, F; Graener, H; Seifert, G

    2010-02-15

    We have investigated the nonlinear refractive index of ex-vivo pig cornea by a combined approach using the standard z-scan technique on extracted corneas or corneal slices, as well as studying the deviations caused by self-focusing during femtosecond laser processing of the pig eyes. The experiments yield consistently an upper limit of 1.2 MW for the critical power of self-focusing in porcine cornea, and a value of 2 x 10(-19) m(2)/W for its nonlinear refractive index. We also demonstrate that due to this nonlinear refraction the cutting depth of typical fs-laser surgery processing in cornea may depend considerably, albeit in a well controllable way, on the laser parameters. PMID:20389380

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

    NASA Astrophysics Data System (ADS)

    Knuettel, Alexander R.; Boehlau-Godau, Martin

    2000-01-01

    In the present applications of optical coherence tomography (OCT), parameters besides pure morphology are evaluated in skin tissue under in vivo conditions. Spatially mapped refractive indices and scattering coefficients may support tissue characterization for research and diagnostic purposes in cosmetics/pharmacy and medicine, respectively. The sample arm of our OCT setup has been arranged to permit refractive index evaluation with little mechanical adjustment of a lens within the objective. A simple algorithm has been derived. Known from atmospheric work, the Klett algorithm has been applied to the same data set for retrieval of scattering coefficients. Both parameters have been measured in layered structures in skin like stratum corneum, epidermis and dermis. Significant water content in a localized sweat gland duct has been observed by refractive index evaluation. Time studies over 1.5 h permitted a first understanding about physiological changes in skin which are not obtainable by intrusive methods.

  14. Dispersion optimization of photonic crystal fiber long-period gratings for a high-sensitivity refractive index sensing

    NASA Astrophysics Data System (ADS)

    Kanka, Jiri

    2011-05-01

    Photonic crystal fiber long-period gratings (PCF-LPGs) operating near the phase-matching turning point to achieve high sensitivity to the refractive index of gas and liquid analytes infiltrated into cladding air holes are designed by numerical optimization. The vectorial finite element method is employed for the modal analysis of an index-guiding PCF and the calculation of the phase matching curves. The geometrical parameters of PCF (pitch and diameter of air holes arranged in a periodic triangular array) are optimized by using the down-hill simplex technique to engineer the dispersion of modes coupled by a LPG to obtain the turning point in the phase-matching curve at a desired wavelength for a given analyte refractive index. The resonant wavelength is subsequently extremely sensitive to the analyte refractive index, however, its large shifts can be detected with a substantially reduced resolution because the resonance dip in the LPG transmission spectrum is very broad. On the other hand, the broad resonance provides a broadband operation of a PCF-LPG sensor and its high sensitivity to the refractive index can still be achieved by relying on changes in the coupling strength (and consequently in the transmission loss) rather than in the resonant wavelength of LPG. We consider coupling between the fundamental core mode and the first-order symmetric cladding mode. We also explore an alternative approach based on coupling between the fundamental core mode and the fundamental space-filling mode instead of the individual cladding mode. The PCF-LPG structure optimized for refractive-index sensing is also assessed for label-free biosensing.

  15. Gradient refractive index of the crystalline lens of the Black Oreo Dory ( Allocyttus Niger): comparison of magnetic resonance imaging (MRI) and laser ray-trace methods

    Microsoft Academic Search

    L. F Garner; G Smith; S Yao; R. C Augusteyn

    2001-01-01

    The gradient refractive index of the crystalline lens in the Black Oreo Dory (Allocyttus Niger) was determined using two methods; an optimisation program based on finite ray-tracing and the path of laser beams through the lens, and magnetic resonance imaging (MRI) and the linear relationship between refractive index and nuclear transverse relaxation rates. The methods showed good agreement in the

  16. Substrate effect on refractive index dependence of plasmon resonance for individual silver nanoparticles observed using darkfield microspectroscopy

    Microsoft Academic Search

    A. Curry; G. Nusz; A. Chilkoti; Adam Wax

    2005-01-01

    We use optical darkfield micro-spectroscopy to characterize the plasmon resonance of individual silver nanoparticles in the presence of a substrate. The optical system permits multiple individual nanoparticles to be identified visually for simultaneous spectroscopic study. For silver particles bound to a silanated glass substrate, we observe changes in the Plasmon resonance due to induced variations in the local refractive index.

  17. Retrieval of the effective complex refractive index of Bruggeman nanoliquids from surface plasmon resonance reflectance using the maximum entropy method

    Microsoft Academic Search

    Jarkko J. Saarinen

    2006-01-01

    We show that surface plasmon resonance reflectance measurement can be used to extract the effective complex refractive index of a Bruggeman nanoliquid, i.e. a solution consisting of spherical nanoparticles embedded into a host liquid such as water, using the maximum entropy method. This retrieval can be immediately performed once the optical properties of the host liquid are known. In this

  18. Enabling RF\\/microwave devices using negative-refractive-index transmission-line (NRI-TL) metamaterials

    Microsoft Academic Search

    George V. Eleftheriades

    2007-01-01

    Metamaterials are artificially engineered structures with unusual electromagnetic properties. In this article, we review the implementation of isotropic metamaterials that exhibit a negative permittivity and a negative permeability, thus leading to a negative index of refraction. Specifically, the article focuses on transmission-line metamaterials, which are planar structures comprising a network of distributed transmission lines loaded periodically with inductors, L, and

  19. Peng & Dinsmore, submitted (2011) p. 1 High-refractive-index tin sulfide core-shell spheres for photonic applications

    E-print Network

    Dinsmore, Tony

    2011-01-01

    Peng & Dinsmore, submitted (2011) p. 1 High-refractive-index tin sulfide core-shell spheres of core-shell colloidal spheres composed of a shell of tin sulfide and a core of polystyrene. The tin sulfide shell is deposited on micron-sized latex spheres using a sonochemical technique. By angle

  20. Numerical analysis and experimental investigation of highly sensitive photonic crystal fiber long-period grating refractive index sensor

    NASA Astrophysics Data System (ADS)

    He, Zonghu; Zhu, Yinian; Ka?ka, Ji?í; Du, Henry

    2007-09-01

    In this paper, we present the numerical analyses of modal coupling properties and resonance spectral response of longperiod gratings (LPGs) in solid-core photonic crystal fibers (PCFs) with respect to their sensitivity to refractive indices of measurands in the air channels using a full-vectoral mode solver combined with frequency-domain method. The calculated results show that the wavelength resonance of a PCF-LPG can be extremely sensitive to the refractive index change. The PCF-LPG refractive index sensors, inscribed by residual stress relaxation using a scanning CO II laser, are also experimentally investigated in terms of resonance shift with the PCF-LPG structure filled with sodium chloride (NaCl) solutions at concentrations ranging from 0-26% (w/w). The spectral features were greatly improved by inscribing the LPG structure in PCF prefilled with water. The PCF-LPG sensors are shown to be able to detect the change of ~10 -7 refractive index unit (RIU) in the index range of 1.33 to 1.35, in a good agreement with the numerical simulation.

  1. Transfer matrix method for point sources radiating in classes of negative refractive index materials with 2n-fold antisymmetry

    Microsoft Academic Search

    B. Gralak; S. Guenneau

    2007-01-01

    We introduce a transfer matrix algorithm well-suited for negative refractive index materials. We achieve a clean mathematical derivation of the electromagnetic field radiated by finite and countable sets of harmonic point sources within a class of perfect lenses [1] which present some periodicity along one axis. In the case of a periodic set of point sources, combining a coordinate transformation

  2. Highly Sensitive Monolithic Silicon Photonic Crystal Fiber Tip Sensor for Simultaneous Measurement of Refractive Index and Temperature

    Microsoft Academic Search

    Il Woong Jung; Bryan Park; J. Provine; Roger T. Howe; Olav Solgaard

    2011-01-01

    Fiber optic sensors have applications in the measure- ment of a wide range of physical properties such as temperature, pressure, and refractive index. These sensors are immune to elec- tromagnetic interference, made of high temperature dielectric ma- terials and hence can be deployed in harsh environments where conventional electronics would fail. Photonic crystal (PC) fiber tip sensors are highly sensitive

  3. Quantitative estimate of fs-laser induced refractive index changes in the bulk of various transparent materials

    NASA Astrophysics Data System (ADS)

    Mermillod-Blondin, A.; Seuthe, T.; Eberstein, M.; Grehn, M.; Bonse, J.; Rosenfeld, A.

    2014-05-01

    Over the past years, many applications based on laser-induced refractive index changes in the volume of transparent materials have been demonstrated. Ultrashort pulse lasers offer the possibility to process bulky transparent materials in three dimensions, suggesting that direct laser writing will play a decisive role in the development of integrated micro-optics. At the present time, applications such as 3D long term data storage or embedded laser marking are already into the phase of industrial development. However, a quantitative estimate of the laser-induced refractive index change is still very challenging to obtain. On another hand, several microscopy techniques have been recently developed to characterize bulk refractive index changes in-situ. They have been mostly applied to biological purposes. Among those, spatial light interference microscopy (SLIM), offers a very good robustness with minimal post acquisition data processing. In this paper, we report on using SLIM to measure fs-laser induced refractive index changes in different common glassy materials, such as fused silica and borofloat glass (B33). The advantages of SLIM over classical phase-contrast microscopy are discussed.

  4. Measurements of the imaginary part of the refractive index between 300 and 700 nanometers for Mount St. Helens ash

    Microsoft Academic Search

    E. M. PATTERSON

    1981-01-01

    The absorption properties, expressed as a wavelength-dependent imaginary index of refraction, of the Mount St. Helens ash from the 18 May 1980 eruption were measured between 300 and 700 nanometers by diffuse reflectance techniques. The measurements were made for both surface and stratospheric samples. The stratospheric samples show imaginary index values that decrease from approximately 0.01 to 0.02 at 300

  5. Determination of Refractive Index Contrast and Surface Contraction in Waveguide Channels Using Multiobjective Genetic Algorithm Applied to Spectroscopic Ellipsometry

    Microsoft Academic Search

    Vasco R. Fernandes; Carlos Miguel Santos Vicente; Edison Pecoraro; Dmitry Karpinsky; Andrei L. Kholkin; Naoya Wada; Paulo S. Andre; Rute A. S. Ferreira

    2011-01-01

    The application of spectroscopic ellipsometry for the characterization of UV-patterned channel waveguides to obtain the refractive index contrast and surface deformation profile is presented. Thin films were prepared with organic-inorganic di-ureasils hybrids modified with zirconium tetra-propoxide deposited in silica on silicon substrates. The channel waveguides were produced by direct writing using UV laser radiation. The re- fractive index contrast and

  6. In vivo measurement of the shape of the tissue-refractive-index correlation function and its applicationto detection of colorectal field carcinogenesis

    NASA Astrophysics Data System (ADS)

    Gomes, Andrew J.; Ruderman, Sarah; DelaCruz, Mart; Wali, Ramesh K.; Roy, Hemant K.; Backman, Vadim

    2012-04-01

    Polarization-gated spectroscopy is an established method to depth-selectively interrogate the structural properties of biological tissue. We employ this method in vivo in the azoxymethane (AOM)-treated rat model to monitor the morphological changes that occur in the field of a tumor during early carcinogenesis. The results demonstrate a statistically significant change in the shape of the refractive-index correlation function for AOM-treated rats versus saline-treated controls. Since refractive index is linearly proportional to mass density, these refractive-index changes can be directly linked to alterations in the spatial distribution patterns of macromolecular density. Furthermore, we found that alterations in the shape of the refractive-index correlation function shape were an indicator of both present and future risk of tumor development. These results suggest that noninvasive measurement of the shape of the refractive-index correlation function could be a promising marker of early cancer development.

  7. Influence of surrounding media refractive index on the thermal and strain sensitivities of long-period gratings.

    PubMed

    Kamikawachi, Ricardo Canute; Collere Possetti, Gustavo Rafael; Falate, Rosane; Muller, Marcia; Fabris, José Luís

    2007-05-20

    A detailed study of the thermal and strain sensitivities of a long-period grating when the device is immersed in different external media is presented. The range of refractive indices analyzed are within 1.000 to 1.447, corresponding to samples of air, water, ethanol, naphtha, thinner, turpentine, and kerosene. Within the same range of refractive indices, the strain sensitivity is between (-0.24 +/- 0.03) and (-0.94 +/- 0.11) pm/microepsilon. For the grating immersed in these fluids, the refractive index sensitivity ranges from -3 to -1035.6 nm per refractive index units. The coupling thermo-optic coefficients and the strain-optic coefficients are also measured, resulting in the range from (2.45 +/- 0.04)x10(-5) to (15.89 +/- 0.82)x10(-5) deg C(-1) and (-1.15 +/- 0.04) to (-1.61 +/- 0.04) microepsilon(-1), respectively. A noticeable nonlinear behavior of the thermal sensitivity is found for external media with refractive indices higher than 1.430. PMID:17514227

  8. Refractive index sensitivity of nano-film coated long-period fiber gratings.

    PubMed

    Zou, Fang; Liu, Yunqi; Deng, Chuanlu; Dong, Yanhua; Zhu, Shan; Wang, Tingyun

    2015-01-26

    We demonstrate the fabrication of long-period fiber gratings (LPFGs) coated with high index nano-film using the atomic layer deposition (ALD) technology. Higher index sensitivity can be achieved in the transition region of the coated LPFGs. For the LPFG coated by nano-film with a thickness of 100 nm, the high index sensitivity of 3000 nm/RIU and the expanded index sensitive range are obtained. The grating contrast of the over-coupled LPFGs and conventional LPFGs are measured and the over-coupled gratings are found to have a higher contrast in the transition region. The cladding modes transition is observed experimentally with increasing surrounding index using an infrared camera. The theoretical model of the hybrid modes in four-layer cylindrical waveguide is proposed for numerical simulation. The experimental results are well consistent with theoretical analysis. PMID:25835871

  9. Best fit refractive index of matching liquid for 3D NIPAM gel dosimeters using optical CT

    NASA Astrophysics Data System (ADS)

    Chen, Chin-Hsing; Wu, Jay; Hsieh, Bor-Tsung; Chen, De-Shiou; Wang, Tzu-Hwei; Chien, Sou-Hsin; Chang, Yuan-Jen

    2014-11-01

    The accuracy of an optical computed tomography (CT)-based dosimeter is significantly affected by the refractive index (RI) of the matching liquid. Mismatched RI induces reflection and refraction as the laser beam passes through the gel phantom. Moreover, the unwanted light rays collected by the photodetector produce image artifacts after image reconstruction from the collected data. To obtain the best image quality, this study investigates the best-fit RI of the matching liquid for a 3D NIPAM gel dosimeter. The three recipes of NIPAM polymer gel used in this study consisted of 5% gelatin, 5% NIPAM and 3% N,N'-methylene bisacrylamide, which were combined with three compositions (5, 10, and 20 mM) of Tetrakis (hydroxymethyl) phosphonium chloride. Results were evaluated using a quantitative evaluation method of the gamma evaluation technique. Results showed that the best-fit RI for the non-irradiated NIPAM gel ranges from 1.340 to 1.346 for various NIPAM recipes with sensitivities ranging from 0.0113 to 0.0227. The greatest pass rate of 88.00% is achieved using best-fit RI=1.346 of the matching liquid. The adoption of mismatching RI decreases the gamma pass rate by 2.63% to 16.75% for all three recipes of NIPAM gel dosimeters. In addition, the maximum average deviation is less than 0.1% for the red and transparent matching liquids. Thus, the color of the matching liquid does not affect the measurement accuracy of the NIPAM gel dosimeter, as measured by optical CT.

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

    PubMed

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

    2011-03-01

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

  11. Towards Silk Fiber Optics: Refractive Index Characterization, Fiber Spinning, and Spinneret Analysis

    NASA Astrophysics Data System (ADS)

    Spitzberg, Joshua David

    Of the many biologically derived materials, whose historical record of use by humans underscores an ex-vivo utility, silk is interesting for it's contemporary repurposing from textile to biocompatible substrate. And while even within this category silk is one of several materials studied for novel repurposing, it has the unique character of being evolutionarily developed specifically for fiber spinning in vivo. The work discussed here is inspired by taking what nature has given, to explore the in vitro spinning of silk towards biocompatible fiber optics applications. A common formulation of silk used in biomedical studies for re-forming it into the various structures begins with the silkworm cocoon, which is degummed and dissolved into an aqueous solution of its miscible protein, fibroin, and post-treated to fabricate solid structures. In the first aim, the optical refractive index (RI) of various post-treatment methods is discussed towards determining RI design techniques. The methods considered in this work for re-forming a solid fiber from the reconstituted silk fibroin (RSF) solution borrow from the industrial techniques of gel spinning, and dry-spinning. In the second aim, methods are applied to RSF and quality of the spun fibers discussed. A feature common to spinning techniques is passing the (silk) material through a spinneret of specific shape. In the third aim, fluid flow through a simplified native silkworm spinneret is modeled towards bio-inspired lessons in design. In chapter 1 the history, reconstitution, are discussed towards understanding the fabrication of several optical device examples. Chapter 2 then prefaces the experiments and measurements in fiber optics by reviewing electromagnetic theory of waveguide function, and loss factors, to be considered in actual device fabrication. Chapter 3 presents results and discussion for the first aim, understanding design principles for the refractive index of RSF. From this point, industrial fiber-spinning approaches are reviewed from a theoretical and methodological perspective in chapter 4. Thus, chapter 5 presents results for the second aim, efforts to apply these techniques using RSF. Chapter 6 discusses the third aim, understanding the design of the silkworm spinneret by an idealized model of natural and reconstituted silk fibroin flow. While the ultimate goal of a structurally and optically smooth and uniform fiber remains elusive, this work serves as a guide for future efforts.

  12. Index of refraction of gases for matter waves: effect of the motion of the gas particles on the calculation of the index

    E-print Network

    Caroline Champenois; Marion Jacquey; Steven Lepoutre; Matthias Büchner; Gérard Trénec; Jacques Vigué

    2007-11-09

    Two different formulae relating the index of refraction $n$ of gases for atom waves to the scattering amplitude have been published. We show here that these two formulae are not consistent with the definition of the total scattering cross-section while the formula developed by one of us (C.C.) in her thesis is in agreement with this standard knowledge. We discuss this result, in particular in the neutron case for which such an index was first introduced. We finally evaluate the index of refraction as a function of well known quantities and we discuss the order of magnitude of the ratio of $(n-1)/n_t$, where $n_t$ is the gas density.

  13. Index of refraction of gases for matter waves: Effect of the motion of the gas particles on the calculation of the index

    NASA Astrophysics Data System (ADS)

    Champenois, Caroline; Jacquey, Marion; Lepoutre, Steven; Büchner, Matthias; Trénec, Gérard; Vigué, Jacques

    2008-01-01

    Two different formulas relating the index of refraction n of gases for atom waves to the scattering amplitude have been published. We show here that these two formulas are not consistent with the definition of the total scattering cross section while the formula developed by one of us [C. Champenois, Ph.D. thesis, Université P. Sabatier, 1999 (unpublished)] is in agreement with this standard knowledge. We discuss this result, in particular in the neutron case for which such an index was first introduced. We finally evaluate the index of refraction as a function of well-known quantities and we discuss the order of magnitude of the ratio of (n-1)/nt , where nt is the gas density.

  14. Anomalous behavior of neutron refraction index in a perfect crystal near the Bragg reflex

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Anomalous behavior of neutron refraction index in a perfect crystal near Bragg resonance was studied. This phenomenon is connected with the resonance behavior of potential of neutron interaction with crystal near the Bragg reflex. The amplitude of this resonance is equal to magnitude of g-harmonic of neutron interaction potential Vg and width is about the Bragg width of reflex. Recently, it was shown that for the case of noncentrosymmetric crystal this effect result in a large electric field acting on a neutron (value of the field can reach about 108V/cm) . This effect is planed using to search for the electric dipole moment of a neutron. If the degree of crystal imperfect is less than the Bragg reflection width (case of perfect crystal) the width of the reflex is determined by the own width of crystal reflex that is about 10?5 of the neutron energy. The value of g-harmonics of interaction of neutron with crystal Vg and optical potential of the interaction of neutron with crystal V0 are usually about the same. Therefore the variation of neutron energy on a 10?5 of its value will change significantly a potential of neutron interaction with crystal.

  15. Optical fiber sensor based on capillary wall for highly-sensitive refractive index measurement

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Peng, Wei; Zhang, Xinpu; Qian, Siyu

    2014-05-01

    This paper reports a temperature-compensated fiber-optic refractive index (RI) sensor for high sensitivity measurement. The sensor includes a piece of fused-silica capillary (FSC) and a fiber Bragg grating (FBG), both of which are sandwiched by single-mode fibers (SMFs). When light from the lead-in SMF enters into the wall of the FSC that acts as a RI sensing element, multiple modes are excited and interfere to form fringes collected by the lead-out SMF. The FBG is fabricated adjunct to the FSC to compensate its temperature sensitivity. The FSC based sensor prototype is fabricated and sealed in a flow cell to test its performance. Experimental results show that the sensor is highly sensitive to RI, and the sensitivity in the tested RI range from 1.33 to 1.35 is 698.52 nm/RIU and from 1.35 to 1.37 is 1061.78 nm/RIU. The temperature sensitivity of the FSC is -0.173 nm/°C, which is compensated by the FBG. This capillary wall based sensor can be further developed as a miniaturized fiber optic biosensor for biochemical application.

  16. Ultra-weak FBG and its refractive index distribution in the drawing optical fiber.

    PubMed

    Guo, Huiyong; Liu, Fang; Yuan, Yinquan; Yu, Haihu; Yang, Minghong

    2015-02-23

    For the online writing of ultra-weak fiber Bragg gratings (FBGs) in the drawing optical fibers, the effects of the intensity profile, pulse fluctuation and pulse width of the excimer laser, as well as the transverse and longitudinal vibrations of the optical fiber have been investigated. Firstly, using Lorentz-Loren equation, Gladstone-Dale mixing rule and continuity equation, we have derived the refractive index (RI) fluctuation along the optical fiber and the RI distribution in the FBG, they are linear with the gradient of longitudinal vibration velocity. Then, we have prepared huge amounts of ultra-weak FBGs in the non-moving optical fiber and obtained their reflection spectra, the measured reflection spectra shows that the intensity profile and pulse fluctuation of the excimer laser, as well as the transverse vibration of the optical fiber are little responsible for the inconsistency of ultra-weak FBGs. Finally, the effect of the longitudinal vibration of the optical fiber on the inconsistency of ultra-weak FBGs has been discussed, and the vibration equations of the drawing optical fiber are given in the appendix. PMID:25836517

  17. Refractive index matched suspensions as a tool for investigating entrainment by avalanches and debris flows

    NASA Astrophysics Data System (ADS)

    Bates, Belinda; Ancey, Christophe

    2015-04-01

    Geophysical gravity flows such as avalanches and debris flows are complicated mixtures of fluid and solids, often containing particle sizes of many orders of magnitude. In a debris flow, for example, the composition varies from head to tail, and from bottom to top due to particle size segregation and recirculation. In addition the solid components may have different masses and mechanical properties. For this reason, a complete understanding of substrate entrainment by this type of flow is still out of reach. A common strategy for advancing our understanding of the physics of processes like entrainment is to use a greatly simplified laboratory model of a debris flow, and take internal and bulk measurements. This idealized technique forms the basis of this study, in which a two-phase, monodisperse suspension of PMMA beads in a refractive-index matched suspending fluid flowed down a flume, encountering an entrainable region of the same suspension on the way. This study represents the first attempt of taking continuous internal velocity measurements inside a flowing, entraining model avalanche or debris flow in the laboratory. Interior PIV measurements of flow velocity were taken in the entrainable region, along with surface height measurements, to shed some light on the entrainment mechanisms and to see how the bulk flow responded. Further, some differential pressure measurements were made in the entrainable bed to see if pore-pressure peaks had any correlation with significant events during entrainment. We present our preliminary findings and discuss the suitability of the method to entrainment investigations.

  18. Investigation of refractive index distribution in different photonic crystal fiber elements

    NASA Astrophysics Data System (ADS)

    Jaroszewicz, Leszek R.; Kujawi?ska, Ma?gorzata; Stasiewicz, Karol; Mar?, Pawe?; Nasi?owski, Tomasz; Murawski, Micha?; Szyma?ski, Micha?; Siwicki, Bart?omiej; Krauze, Wojciech

    2011-09-01

    The paper presents the last data regarding new elements based on photonic crystal fibers such as the low-loss patch cord with a single mode fiber, the fused coupler, the asymmetric coupler for an active fiber power pump. Their fundamental optical characteristics including wavelength depending loss as a coupling ratio are presented in this paper as well as their inner structure (cross section) obtained by SEM. However, the use of SEM for the investigation of the inner element structure is destructive, thus in the last part of the paper we present the tomographic in-line determination of geometry and refractive index distribution changes along the investigated photonic structure. The analysis of different approaches to the photonic crystal fiber data capture with a sufficient optical resolution is given. The data obtained from the Mach-Zehnder interferometer with different laser sources as well as from the in-line digital holographic setup are presented and compared. The further enhancement required for the digital in-line holography is discussed.

  19. Simultaneous measurement of refractive index and temperature using an epoxy resin-based interferometer.

    PubMed

    Wang, Jian; Wu, Shengli; Ren, Wenyi

    2014-11-20

    A fiber-optics reflection probe based on fiber Fabry-Perot interference (FFPI) is proposed and experimentally demonstrated. The sensing structure comprises an epoxy resin (ER)-based cap on the end-face of the single-mode fiber. A well-defined interference spectrum is obtained by the reflective beams of two surfaces of the ER cap. The simultaneous measurements, including fringe contrast-referenced for the surrounding refractive index (SRI) and wavelength-referenced for temperature, have been achieved via selective interference dips monitoring. Experimental results indicate that the proposed FFPI presents an SRI sensitivity of 57.69 dB/RIU in the measurement range of 1.33-1.40 RIU and a temperature sensitivity of 0.98??pm·?m-1·°C-1 with per unit cavity length in the range of 30°C-70°C. The proposed sensor has advantages of being compact and robust, making it an alternative candidate as a smart sensor in chemical and biological applications. PMID:25607854

  20. Accurate determination of the complex refractive index of solid tissue-equivalent phantom

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    Tissue-equivalent phantom is becoming widespread as a substitute in the biological field to verify optical theories, test measuring systems and study the tissue performances for varying boundary conditions, sample size and shape at a quantitative level. Compared with phantoms made with Intralipid solution, ink and other liquid substances, phantom in solid state is stable over time, reproducible, easy to handle and has been testified to be a suitable optical simulator in the visible and near-infrared region. We present accurate determination of the complex refractive index (RI) of a solid tissueequivalent phantom using extended derivative total reflection method (EDTRM). Scattering phantoms in solid state were measured for p-polarized and s-polarized incident light respectively. The reflectance curves of the sample as a function of incident angle were recorded. The real part of RI is directly determined by derivative of the reflectance curve, and the imaginary part is obtained from nonlinear fitting based on the Fresnel equation and Nelder-Mead simplex method. The EDTRM method is applicable for RI measurement of high scattering media such as biotissue, solid tissue-equivalent phantom and bulk material. The obtained RI information can be used in the study of tissue optics and biomedical field.

  1. Electrical modulation of the complex refractive index in mid-infrared quantum cascade lasers.

    PubMed

    Teissier, J; Laurent, S; Manquest, C; Sirtori, C; Bousseksou, A; Coudevylle, J R; Colombelli, R; Beaudoin, G; Sagnes, I

    2012-01-16

    We have demonstrated an integrated three terminal device for the modulation of the complex refractive index of a distributed feedback quantum cascade laser (QCL). The device comprises an active region to produce optical gain vertically stacked with a control region made of asymmetric coupled quantum wells (ACQW). The optical mode, centered on the gain region, has a small overlap also with the control region. Owing to the three terminals an electrical bias can be applied independently on both regions: on the laser for producing optical gain and on the ACQW for tuning the energy of the intersubband transition. This allows the control of the optical losses at the laser frequency as the absorption peak associated to the intersubband transition can be electrically brought in and out the laser transition. By using this function a laser modulation depth of about 400 mW can be achieved by injecting less than 1 mW in the control region. This is four orders of magnitude less than the electrical power needed using direct current modulation and set the basis for the realisation of electrical to optical transducers. PMID:22274462

  2. Refractive index susceptibility of the plasmonic palladium nanoparticle: potential as the third plasmonic sensing material.

    PubMed

    Sugawa, Kosuke; Tahara, Hironobu; Yamashita, Ayane; Otsuki, Joe; Sagara, Takamasa; Harumoto, Takashi; Yanagida, Sayaka

    2015-02-24

    We demonstrate that Pd nanospheres exhibit much higher susceptibility of the localized surface plasmon resonance (LSPR) peak to medium refractive index changes than commonly used plasmonic sensing materials such as Au and Ag. The susceptibility of spherical Au nanoparticle-core/Pd-shell nanospheres (Au/PdNSs, ca. 73 nm in diameter) was found to be 4.9 and 2.5 times higher, respectively, than those of Au (AuNSs) and Ag nanospheres (AgNSs) having similar diameters. The experimental finding was theoretically substantiated using the Mie exact solution. We also showed from a quasi-static (QS) approximation framework that the high susceptibility of Pd LSPR originates from the smaller dispersion of the real part of its dielectric function than those of Au and Ag LSPR around the resonant wavelength. We conclude that the Pd nanoparticle is a promising candidate of "the third plasmonic sensing material" following Au and Ag to be used in ultrahigh-sensitive LSPR sensors. PMID:25629586

  3. Optical device for sensing the index of refraction of liquids with high turbidity

    NASA Astrophysics Data System (ADS)

    Pena-Gomar, M.; Fajardo-Lira, C.; Rosete-Aguilar, Martha; Garcia-Valenzuela, Augusto

    2000-12-01

    We discuss the use of photo-reflectance near the critical angle (PRCA) to monitor small changes of the RI of highly turbid liquids. The theory of the reflectance of a laser beam near the critical angle for an external medium with a complex RI is summarized. The applicability of PRCA to sense highly turbid media is demonstrated experimentally on bovine milk samples. We give experimental results showing the temporal variation of the refractive index (RI) during three different processes in bovine milk: (1) Mechanical stirring, (2) temperature changes, and (3) pH variations around the isoelectric point of the casein micelles (micelle aggregation). RI changes in the order of a few times 1 X 10-3 are observed during the experiments. The experimental results show that the RI of milk can be used to track physico-chemical changes in time allowing one to measure the time constant of the different process. The design of a compact RI probe for in situ applications is discussed. The miniaturization of such a probe will probably limited by factors other than the loss of sensitivity. A novel angle-of-incidence control which requires only linear displacements of some of the optical components (no rotation) is proposed and shown to be feasible. Such an optical probe may be used in the dairy industry and in general in the food industry or food science research laboratories. It could give additional analytical power to the food scientist, engineer, or technician.

  4. Substrate effect on refractive index dependence of plasmon resonance for individual silver nanoparticles observed using darkfield microspectroscopy.

    PubMed

    Curry, A; Nusz, G; Chilkoti, A; Wax, Adam

    2005-04-01

    We use optical darkfield micro-spectroscopy to characterize the plasmon resonance of individual silver nanoparticles in the presence of a substrate. The optical system permits multiple individual nanoparticles to be identified visually for simultaneous spectroscopic study. For silver particles bound to a silanated glass substrate, we observe changes in the Plasmon resonance due to induced variations in the local refractive index. The shifts in the plasmon resonance are investigated using a simple analytical theory in which the contributions from the substrate and environment are weighted with distance from the nanoparticle. The theory is compared with experimental results to determine a weighting factor which facilitates modeling of environmental refractive index changes using standard Mie code. Use of the optical system for characterizing nanoparticles attached to substrates for biosensing applications is discussed. PMID:19495158

  5. Note: Optical fiber milled by focused ion beam and its application for Fabry-Pérot refractive index sensor

    NASA Astrophysics Data System (ADS)

    Yuan, Wu; Wang, Fei; Savenko, Alexey; Petersen, Dirch Hjorth; Bang, Ole

    2011-07-01

    We introduce a highly compact fiber-optic Fabry-Pérot refractive index sensor integrated with a fluid channel that is fabricated directly near the tip of a 32 ?m in diameter single-mode fiber taper. The focused ion beam technique is used to efficiently mill the microcavity from the fiber side and finely polish the end facets of the cavity with a high spatial resolution. It is found that a fringe visibility of over 15 dB can be achieved and that the sensor has a sensitivity of ˜1731 nm/RIU (refractive index units) and a detection limit of ˜5.78 × 10-6 RIU. This miniature integrated all-in-fiber optofludic sensor may find use in minimal-invasive biomedical applications.

  6. High-resolution electrohydrodynamic jet printing for the direct fabrication of 3D multilayer terahertz metamaterial of high refractive index

    NASA Astrophysics Data System (ADS)

    Teguh Yudistira, Hadi; Pradhipta Tenggara, Ayodya; Oh, Sang Soon; Nguyen, VuDat; Choi, Muhan; Choi, Choon-gi; Byun, Doyoung

    2015-04-01

    The fabrication of 3D metamaterials, such as multilayer structures, is of great interest in practical applications of the metamaterial. Here we present an electrohydrodynamic jet printing technique as a direct fabrication method of 3D multilayer metamaterial. By alignment of the nozzle movement, we could fabricate multiple layers of the metamaterial. Controlling an electrical pulse to make droplets on-demand, we fabricated a high refractive index metamaterial and compared the optical performances of a single layer and multiple layers, with 10?µm width and 5?µm gap of I-shaped meta-atoms on the polyimide substrate. The peak refractive index was 25.7 at 0.46?THz for a four-layer metamaterial.

  7. Linear and nonlinear intersubband optical absorption coefficient and refractive index change in n-type ?-doped GaAs structure

    NASA Astrophysics Data System (ADS)

    Ozturk, Emine; Ozdemir, Yasin

    2013-05-01

    In the effective mass approximation, we have theoretically investigated the subband structure of single Si ?-doped GaAs by solving the Schrödinger and Poisson equations self-consistently. Both the linear and nonlinear intersubband optical absorption coefficients and the refractive index changes are calculated as dependent on the doping concentration and thickness. Our results show that the position and the magnitude of the linear and total absorption coefficients and refractive index changes depend on the doping concentration and thickness. The shape of potential profile and the subband energy differences are changed as dependent on the donor concentration and thickness. By considering the variation of the energy difference we can obtain a blue shift or a red shift in the intersubband optical transitions. The resonant peak of total absorption coefficient can be bleached at sufficiently high incident optical intensities. Such a dependence of the exciting optical intensity on the doping concentration and thickness can be very useful for several potential device applications.

  8. Single mode tapered fiber-optic interferometer based refractive index sensor and its application to protein sensing.

    PubMed

    Yadav, T K; Narayanaswamy, R; Abu Bakar, M H; Kamil, Y Mustapha; Mahdi, M A

    2014-09-22

    We demonstrate refractive index sensors based on single mode tapered fiber and its application as a biosensor. We utilize this tapered fiber optic biosensor, operating at 1550 nm, for the detection of protein (gelatin) concentration in water. The sensor is based on the spectroscopy of mode coupling based on core modes-fiber cladding modes excited by the fundamental core mode of an optical fiber when it transitions into tapered regions from untapered regions. The changes are determined from the wavelength shift of the transmission spectrum. The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V. PMID:25321749

  9. Prediction of refractive index and density of deep eutectic solvents using atomic contributions

    Microsoft Academic Search

    K. Shahbaz; F. S. G. Bagh; F. S. Mjalli; I. M. AlNashef; M. A. Hashim

    2013-01-01

    Deep eutectic solvents (DESs) are considered as potential alternatives for ionic liquids (ILs). The evaluation of DESs as new generation of solvents for various practical application requires enough knowledge about some main physical, chemical, and thermodynamic properties. In this study, due to lack of data for DESs' refractive indices, the refractive indices of twenty four DESs based on ammonium and

  10. Band gap bowing and refractive index spectra of polycrystalline AlxIn1 - xN films deposited by sputtering

    NASA Astrophysics Data System (ADS)

    Peng, T.; Piprek, J.; Qiu, G.; Olowolafe, J. O.; Unruh, K. M.; Swann, C. P.; Schubert, E. F.

    1997-10-01

    The AlGaInN semiconductor system is currently of high interest for applications in blue light emitting devices. AlInN is a prospective material for lattice matched confinement layers. We measure the refractive index as well as the band gap across the entire compositional range of high-quality polycrystalline AlInN samples. Strong band gap bowing is observed.

  11. Nonlinear refractive index measurement on pure and Nd doped YAG ceramic by dual arm Z-scan technique

    NASA Astrophysics Data System (ADS)

    Samuel, P.; Ensley, T. R.; Hu, H.; Hagan, D. J.; Van Stryland, E. W.; Gaume, R.

    2015-06-01

    Transparent ceramics gain much attention as an alternative medium for high power ultra-short lasers because of its superior thermal properties over single crystals. Measurement of nonlinear refractive index is essential to understand the limit of such material for ultra-short laser generation. Dual arm Z-scan technique was employed to measure n2 for single crystal and ceramic at the same time to avoid any uncertainty due to different measuring times.

  12. Numerical laser beam propagation using a Large Eddy Simulation refractive index field representing a jet engine exhaust

    NASA Astrophysics Data System (ADS)

    Sjöqvist, Lars; Henriksson, Markus; Fedina, Ekaterina; Fureby, Christer

    2010-10-01

    The exhaust from jet engines introduces extreme turbulence levels in local environments around aircrafts. This may degrade the performance of electro-optical missile warning and laser-based DIRCM systems used to protect aircrafts against heat-seeking missiles. Full scale trials using real engines are expensive and difficult to perform motivating numerical simulations of the turbulence properties within the jet engine exhaust. Large Eddy Simulations (LES) is a computational fluid dynamics method that can be used to calculate spatial and temporal refractive index dynamics of the turbulent flow in the engine exhaust. From LES simulations the instantaneous refractive index in each grid point can be derived and interpolated to phase screens for numerical laser beam propagation or used to estimate aberration effects from optical path differences. The high computation load of LES limits the available data in terms of the computational volume and number of time steps. In addition the phase screen method used in laser beam propagation may also be too slow. For this reason extraction of statistical parameters from the turbulence field and statistical beam propagation methods are studied. The temporal variation of the refractive index is used to define a spatially varying structure constant. Ray-tracing through the mean refractive index field provides integrated static aberrations and the path integrated structure constant. These parameters can be used in classical statistical parameterised models describing propagation through turbulence. One disadvantage of using the structure constant description is that the temporal information is lost. Methods for studying the variation of optical aberrations based on models of Zernike coefficients are discussed. The results of the propagation calculations using the different methods are compared to each other and to available experimental data. Advantages and disadvantages of the different methods are briefly discussed.

  13. Statistical Analysis of Photonic Crystal Spectra for the Independent Determination of the Size and Refractive Index of Cells.

    PubMed

    Stewart, Justin William; Pyayt, Anna

    2015-07-01

    Photonic crystal flow cytometry is a very attractive platform due to its great sensitivity in combination with a very compact design. Previous studies have demonstrated the possibility to use spectral processing for the measurement of a wide range of parameters, from simple object counting to independent analysis of the buffer solution and immersed microscale objects. Here we propose to go to the next level and simultaneously determine the shape and the refractive index of the cells. PMID:26073041

  14. New materials for nonlinear optical applications: The nonlinear refractive index of colloidal PbSe quantum dots

    Microsoft Academic Search

    I. Moreels; P. Kockaert; D. Van Thourhout; Z. Hens

    2007-01-01

    We present a detailed study of the nonlinear optical properties of colloidal PbSe quantum dot (Q-PbSe) suspensions and thin films. The nonlinear refractive index n2 has been measured with the Z-scan technique as a function of wavelength (1.20 - 1.75µm), optical intensity and nanocrystal volume fraction. The n2-spectra show negative resonances near the Q-PbSe optical transitions. We attributed the high

  15. High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Mont, Frank W.; Kim, Jong Kyu; Schubert, Martin F.; Schubert, E. Fred; Siegel, Richard W.

    2008-04-01

    A high-refractive-index (high-n) encapsulant is highly desirable because it can result in enhancement of light-extraction efficiency from high-n semiconductor light-emitting diode (LED) chips. A uniform dispersion of TiO2 nanoparticles in epoxy for LED encapsulation is demonstrated for surfactant-coated TiO2 nanoparticles by drying, mixing with a solvent, refluxing, centrifuging, and mixing with epoxy. The refractive index of surfactant-coated TiO2-nanoparticle-loaded epoxy is 1.67 at 500nm, significantly higher than that of conventional epoxy (n =1.53). Theoretical analysis of optical scattering in nanoparticle-loaded encapsulants reveals that the diameter of nanoparticles and the volume loading fraction of nanoparticles are of critical importance for optical scattering. Quasispecular transparency of the encapsulant film can be achieved if the thickness of the film is kept below the optical scattering length. A graded-refractive-index multilayer encapsulation structure with the thickness of each layer being less than the mean optical scattering length is proposed in order to reduce optical losses from scattering and Fresnel reflection. Furthermore, three-dimensional optical ray-tracing simulations demonstrate that encapsulants with an optimized scattering coefficient, ks, benefit from optical scattering by extracting deterministic trapped modes. Theoretical light-extraction enhancements larger than 50% are found when comparing scattering-free to scattering encapsulation materials.

  16. Simultaneous measurement of refractive index, temperature and strain based on core diameter mismatch and polarization-maintaining FBG

    NASA Astrophysics Data System (ADS)

    Tong, Zheng-rong; Wang, Jie-yu; Zhang, Wei-hua; Cao, Ye

    2013-05-01

    A kind of fiber-optic sensor for simultaneous measurement of refractive index of surrounding medium, temperature and strain is described. Based on core diameter mismatch, a multimode-single mode-multimode (MSM) structure is presented. It is demonstrated that the three parameters can be measured respectively by the interference of the core mode and cladding modes excited in the single mode fiber (SMF). Then combined with a polarization-maintaining fiber Bragg grating (PMFBG) which has different sensing properties from MSM structure, three parameters are measured simultaneously. The experimental results show that PMFBG is insensitive to the refractive index and the refractive index sensitivity of the MSM structure is 96.04 nm·RIU-1; the temperature sensitivities of the characteristic wavelength for MSM structure and the center wavelengths of fast and slow axes for PMFBG are 0.0911 nm · °C-1, 0.00976 nm · °C-1 and 0.0105 nm · °C-1, respectively; the strain sensitivities of those are -0.013 nm · ??-1, 0.012 nm · ??-1 and 0.012 nm · ??-1, respectively.

  17. Positive identification of lithographic photoresists using real-time index of refraction monitoring for reduced cost of ownership

    NASA Astrophysics Data System (ADS)

    Jee, Ron; Pepper, Susanne; Stedman, David

    2009-03-01

    This study involved installation of a real-time refractive index monitoring system into a simulated photoresist feed line as would be used for delivery to a lithography tool. The goal was to determine whether this refractive index technology could be used to differentiate among all possible photoresists that could potentially be delivered to a lithography tool and resolve each one, separate from the others. The main intention is to use this technology to prevent the wrong photoresist from being used. The use of the wrong photoresist could result in hundreds of thousands of dollars per year in wafers scrapped in late stages of the process flow. A Swagelok(R) CR-288(R) concentration monitor, using refractive index (RI) sensing, was installed into a simulated photoresist feed line to monitor and detect each one in real time. By integrating the CR-288 concentration monitor into the lithographic process system, the capability for uniquely identifying and resolving 10 out of 10 Deep Ultra Violet (DUV) photoresists was demonstrated, potentially leading to a large cost avoidance and reduced cost of ownership.

  18. Numerical and experimental investigation of long-period gratings in photonic crystal fiber for refractive index sensing of gas media.

    PubMed

    Tian, Fei; He, Zonghu; Du, Henry

    2012-02-01

    We have used the finite-difference frequency-domain (FDFD) method to simulate the core mode to cladding mode couplings in long-period gratings (LPGs) in photonic crystal fiber (PCF). Four sets of LPG-PCF have been fabricated with respective periodicities of 590, 540, 515, and 490 ?m, resulting in corresponding resonance wavelengths (RWs) of 1241, 1399, 1494, and 1579 nm. We show both theoretically and experimentally that the longer the RW, the more sensitive the LPG-PCF is to the index change in Ar. We demonstrate a robust sensitivity of 517 nm per refractive index unit using the LPG-PCF at 1579 nm RW. PMID:22297359

  19. Length and refractive index measurement by Fourier transform interferometry and frequency comb spectroscopy

    NASA Astrophysics Data System (ADS)

    Balling, Petr; Mašika, Pavel; K?en, Petr; Doležal, Miroslav

    2012-09-01

    In this paper we describe the progress we have made in our simultaneous length measurement and the femtosecond comb interferometric spectroscopy in a conventional arrangement with a moving mirror. Scanning and detection over an interval longer than the distance between two consecutive pulses of the frequency comb allow for a spectral resolution of the individual frequency modes of the comb. Precise knowledge of comb mode frequency leads to a precise estimation of the spectral characteristics of inspected phenomena. Using the pulse train of the frequency comb allows for measurement with highly unbalanced lengths of interferometer arms, i.e. an absolute long distance measurement. Further, we present a non-contact (double sided) method of measurement of the length/thickness of plane-parallel objects (gauge blocks, glass samples) by combining the fs comb (white light) with single frequency laser interferometry. The position of a fringe packet is evaluated by estimating the stationary phase position for any wavelength in the spectral band used. The repeatability of this position estimation is a few nanometres regardless of whether dispersion of the arms is compensated (transform limited fringe packet ˜10 fringes FWHM) or highly different (fringe packet stretched to >200 fringes FWHM). The measurement of steel gauge block by this method was compared with the standard method, and deviation (+13 ± 12) nm for gauge blocks (2 to 100) mm was found. The measurement of low reflecting ceramic gauges or clear glass samples was also tested. In the case of glass, it becomes possible to measure simultaneously both the thickness and the refractive index (and dispersion) of flat samples.

  20. Refractive index change dependence on Ge(1) defects in {gamma}-irradiated Ge-doped silica

    SciTech Connect

    Alessi, A.; Agnello, S.; Gelardi, F. M. [Department of Physical and Astronomical Sciences, University of Palermo, Via Archirafi 36, 90123 Palermo (Italy); Grandi, S. [Department of Physical Chemistry, University of Pavia, Via Taramelli 16, 27100 Pavia (Italy); Parlato, A. [Department of Nuclear Engineering, University of Palermo, Viale delle Scienze, Building 6, 90128 Palermo (Italy)

    2009-07-01

    We present an experimental study regarding the effects of the {gamma} radiation on silica glass doped with Ge up to 10 000 ppm molar produced by the sol-gel technique. We have determined the irradiation-induced changes in the refractive index ({delta}n) as a function of the oxygen deficiency of the samples, evaluated from the ratio between the germanium lone pair centers (GLPC) and the Ge content. {delta}n at 1500 nm have been estimated using optical-absorption spectra in the range 1.5-6 eV. We have found that {delta}n is independent of Ge differences for GLPC/Ge values <10{sup -4}, while it depends on Ge for larger oxygen deficiencies. In details, the oxygen deficiency can reduce the induced {delta}n of the investigated materials and our studies evidence that the photosensitivity of the GeO{sub 2}-SiO{sub 2} glass is reduced until the GLPC concentration reaches values of 2x10{sup 17}-5x10{sup 17} defects/cm{sup 3}. We have also investigated the induced concentration of paramagnetic point defects [Ge(1), Ge(2), and E'Ge] using the electron-paramagnetic-resonance (EPR) technique. From the comparison of the optical and EPR data we have further found a relation between the induced optical-absorption coefficient at 5.8 eV and Ge(1) defects, a linear correlation between Ge(1) and {delta}n and the absence of a correlation between the other paramagnetic defects and {delta}n. These findings suggest that the {delta}n phenomenology is closely related to the Ge(1) generation mechanisms and this latter is affected by the oxygen defic0011ien.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    Scintillometers measure amount of scintillations by emitting a beam of light over a horizontal path and expresses as the atmospheric turbulence structure parameter as the refractive index of air (Cn2). Cn2 represents the turbulent strength of the atmosphere and describes the ability of the atmosphere to transport heat and humidity. The main objective of this study was to evaluate the effect of scintillometer height on Cn2 measurements and on the estimation of latent heat fluxes. The study was conducted during the 2009 summer growing season in the USDA-ARS Conservation and Production Research Laboratory (CPRL) at Bushland [350 11' N, 1020 06' W; 1,170 m elevation MSL], Texas. Field experiment consisted of two steps: (1) cross-calibration of scintillometers and (2) measurement of Cn2 at different heights. In the first step, three large aperture scintillometers (LAS) were deployed across two large lysimeter fields with bare soil surfaces. During the 3-week cross-calibration period, all three scintillometers were installed at a 2-m height with a path length of 420 m. Cn2 was monitored at a 1-min interval and averaged for 15-min periods. Cn2 measurements were synchronized with weather station and weighing lysimeter measurements. After the cross-calibration period, scintillometers were installed at 2-, 2.5- and 3-m heights, and Cn2 measurements were continued for another 3-week period. In addition to the Cn2 measurements, net radiation (Rn) and soil heat fluxes (G) were measured in both lysimeter fields. Cn2 values were corrected for inner scale dependence before cross calibration and estimation of sensible heat fluxes. Measurements of wind speed, air temperature, and relative humidity were used with Cn2 data to derive sensible heat fluxes. Latent heat fluxes were estimated as a residual from the energy balance and compared with lysimeter data. Results of cross calibration and effects of scintillometer height on the estimation of latent heat fluxes were reported and discussed.

  2. Direct method of determination of the equivalent refractive index profile of the multimode optical fiber by measured impulse responses due to scanning output fiber end

    NASA Astrophysics Data System (ADS)

    Burdin, Vladimir A.; Bourdine, Anton V.; Praporshchikov, Denis E.

    2015-03-01

    This paper demonstrates the possibility of determining the equivalent, in terms of the coincidence of differential mode delay diagram, refractive index profile of the multimode optical fiber by direct method and responses to pulse action, which are measured at the output through single-mode optical fiber. As an example, by using the measured data of the refractive index profile of the sample of multimode optical fiber and based on Gaussian approximation model impulse responses at the output of a short length single mode fiber, which was jointed with multimode fiber, were calculated. Multimode and single mode fibers were jointed with axial misalignment. Responses to impulse action were calculated for several values of axial misalignment of single-mode and multimode fiber. From the responses by the direct method the equivalent refractive index profile was determined. Comparison of the results of calculations of the differential-mode delay diagram for the investigated and the equivalent refractive index profiles showed their good agreement.

  3. Theoretical analysis of guided mode and effective refractive index at 1.53 ?m in Ti:LiNbO3 strip waveguides

    Microsoft Academic Search

    Delong Zhang; Guilan Ding; Caihe Chen

    1998-01-01

    An analysis of guided modes and effective refractive indexes in c-cut Ti-diffused LiNbO3 strip waveguides has been performed at the wavelength 1.53 ?m by the variational method. Dependences of mode size and effective refractive index on initial Ti-strip width W, diffusion temperature T and initial Ti-strip thickness H have been calculated for several lower order modes. As compared the plots

  4. Refractive-Index Sensing With Inline Core-Cladding Intermodal Interferometer Based on Silicon Nitride Nano-Coated Photonic Crystal Fiber

    Microsoft Academic Search

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

    2012-01-01

    This paper presents a modification of the refractive-index (RI) response of an intermodal interferometer based on photonic crystal fiber (PCF) using a thin plasma-deposited silicon nitride (SiN $_{\\\\rm x}$) 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

  5. Properties of defect mode and optical enhancement of 1D photonic crystals with a defect layer of negative refractive index material

    Microsoft Academic Search

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

    2005-01-01

    The band gap properties of one-dimensional photonic crystals with a defect layer of negative refractive index materials are\\u000a studied. The defect mode width is bigger than that of conventional one-dimensional photonic crystals with a defect layer of\\u000a positive refractive index materials. The defect mode of the former is different from that of the latter, shifts towards the\\u000a direction of high

  6. Method for measuring the refractive index and the thickness of transparent plates with a lateral-shear, wavelength-scanning interferometer

    Microsoft Academic Search

    Giuseppe Coppola; Pietro Ferraro; Mario Iodice; Sergio de Nicola

    2003-01-01

    A new method for measuring simultaneously the thickness and the refractive index of a transparent plate is proposed. The method is based on a simple, variable lateral-shear, wavelength-scanning interferometer. To achieve highly accurate measurements of both refractive index n and thickness d we use several means to determine these two quantities. We finely tune a distributed-feedback diode laser light source

  7. Refractive indexes and electronic polarizabilities of molten HoCl 3–NaCl and HoCl 3–KCl mixtures

    Microsoft Academic Search

    Kazuya Shirao; Takuma Iida; Kazuko Fukushima; Yasuhiko Iwadate

    1998-01-01

    The refractive indexes of molten HoCl3–NaCl and HoCl3–KCl mixtures were measured by goniometry using visible light at eight wavelengths and expressed as functions of both temperature and wavelength into empirical formulas by a least-squares method. The electronic polarizabilities of ions in the mixture melts were obtained from the data of refractive indexes and molar volumes, and the polarizability of a

  8. Sol-gel preparation of hydrophobic silica antireflective coatings with low refractive index by base/acid two-step catalysis.

    PubMed

    Cai, Shuang; Zhang, Yulu; Zhang, Hongli; Yan, Hongwei; Lv, Haibing; Jiang, Bo

    2014-07-23

    Hydrophobic antireflective coatings with a low refractive index were prepared via a base/acid-catalyzed two-step sol-gel process using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors, respectively. The base-catalyzed hydrolysis of TEOS leads to the formation of a sol with spherical silica particles in the first step. In the second step, the acid-catalyzed MTES hydrolysis and condensation occur at the surface of the initial base-catalyzed spherical silica particles, which enlarge the silica particle size from 12.9 to 35.0 nm. By a dip-coating process, this hybrid sol gives an antireflective coating with a refractive index of about 1.15. Moreover, the water contact angles of the resulted coatings increase from 22.4 to 108.7° with the increases of MTES content, which affords the coatings an excellent hydrophobicity. A "core-shell" particle growth mechanism of the hybrid sol was proposed and the relationship between the microstructure of silica sols and the properties of AR coatings was investigated. PMID:24979297

  9. Refractive-index dispersion for BaF2-GdF3-ZrF4-AlF3 glasses.

    PubMed

    Mitachi, S; Miyashita, T

    1983-08-15

    Refractive-index dispersion measurements were performed on bulk specimens of 2-, 4-, or 6-mol % AlF(3) doped 33BaF(2)-4GdF(3)-63ZrF(4) (mol %) glass and 4-mol % LiF, CsF, YF(3), CdF(2), SnF(2), or PbF(2) doped 31.68BaF(2)-3.84GdF(3)-60.48ZrF(4)-4AIF(3) (mol %) glass in the wavelength region from 0.4047 to 5.3036 microm. The material dispersion curve and zero material dispersion wavelength were estimated on the basis of refractive- index dispersion measurements. The slope of the material dispersion curve for these fluoride glasses was less steep than that for SiO2 glass in the wavelength range estimated. The zero material wavelength lambda(0) shifted to a shorter wavelength with increasing AlF3 concentration. The lambda(0) is 1.675 microm for 31.68BaF(2)- 3.84GdF(3)-60.48ZrF(4)-4AlF(3) (mol %) glass. When 4-mol % LiF, CsF, YF(3), CdF(2), SnF(2), or PbF(2) were doped into these glasses, each lambda(0) shifted from 1.675 to 1.670, 1.668, 1.673, 1.681, 1.683, or 1.704 microm, respectively. The temperature dependence values of the refractive-index dispersion and material dispersion for 31.68BaF(2)-3.84GdF(3) -60.48ZrF(4)-4AIF(3) (mol %) glass were also obtained. The temperature coefficients of the refractive index were negative values (dn/dT(relative) = -1.0 X 10(-5)/degrees C) and the wavelength dependence of dn/dT was small. The wavelength lambda(0) shifted from 1.675 to 1.605 microm, due to the rise in the measurement temperature from 25 degrees C to 250 degrees C. PMID:18196149

  10. Gradient refractive index of the crystalline lens of the Black Oreo Dory (Allocyttus Niger): comparison of magnetic resonance imaging (MRI) and laser ray-trace methods.

    PubMed

    Garner, L F; Smith, G; Yao, S; Augusteyn, R C

    2001-04-01

    The gradient refractive index of the crystalline lens in the Black Oreo Dory (Allocyttus Niger) was determined using two methods; an optimisation program based on finite ray-tracing and the path of laser beams through the lens, and magnetic resonance imaging (MRI) and the linear relationship between refractive index and nuclear transverse relaxation rates. The methods showed good agreement in the cortical zone of the lens, but the lack of free water in the core of the lens made MRI measurement impossible in this region. The laser-optimisation method gave mean values of 1.368 and 1.543 for the surface and core refractive indices respectively, with a radial distribution for the gradient refractive index given by n(r)=1.543-0.121r2-0.033r4-0.021r6. PMID:11301072

  11. Characterization of the stress and refractive-index distributions in optical fibers and fiber-based devices

    NASA Astrophysics Data System (ADS)

    Hebenstreit, Florian

    2011-07-01

    Optical fiber technology continues to advance rapidly as a result of the increasing demands on communication systems and the expanding use of fiber-based sensing. New optical fiber types and fiber-based communications components are required to permit higher data rates, an increased number of channels, and more flexible installation requirements. Fiber-based sensors are continually being developed for a broad range of sensing applications, including environmental, medical, structural, industrial, and military. As optical fibers and fiber-based devices continue to advance, the need to understand their fundamental physical properties increases. The residual-stress distribution (RSD) and the refractive-index distribution (RID) play fundamental roles in the operation and performance of optical fibers. Custom RIDs are used to tailor the transmission properties of fibers used for long-distance transmission and to enable fiber-based devices such as long-period fiber gratings (LPFGs). The introduction and modification of RSDs enable specialty fibers, such as polarization-maintaining fiber, and contribute to the operation of fiber-based devices. Furthermore, the RSD and the RID are inherently linked through the photoelastic effect. Therefore, both the RSD and the RID need to be characterized because these fundamental properties are coupled and affect the fabrication, operation, and performance of fibers and fiber-based devices. To characterize effectively the physical properties of optical fibers, the RSD and the RID must be measured without perturbing or destroying the optical fiber. Furthermore, the techniques used must not be limited in detecting small variations and asymmetries in all directions through the fiber. Finally, the RSD and the RID must be characterized concurrently without moving the fiber to enable the analysis of the relationship between the RSD and the RID. Although many techniques exist for characterizing the residual stress and the refractive index in optical fibers, there is no existing methodology that meets all of these requirements. Therefore, the primary objective of the research presented in this thesis was to provide a methodology that is capable of characterizing concurrently the three-dimensional RSD and RID in optical fibers and fiber-based devices. This research represents a detailed study of the requirements for characterizing optical fibers and how these requirements are met through appropriate data analysis and experimental apparatus design and implementation. To validate the developed methodology, the secondary objective of this research was to characterize both unperturbed and modified optical fibers. The RSD and the RID were measured in a standard telecommunications-grade optical fiber, Corning SMF-28. The effects of cleaving this fiber were also analyzed and the longitudinal variations that result from cleaving were explored for the first time. The fabrication of carbon-dioxide-laser-induced (CO2 -laser-induced) LPFGs was also examined. These devices provide many of the functionalities required for fiber-based communications components as well as fiber-based sensors, and they offer relaxed fabrication requirements when compared to LPFGs fabricated by other methods. The developed methodology was used to perform the first measurements of the changes that occur in the RSD and the RID during LPFG fabrication. The analysis of these measurements ties together many of the existing theories of CO2-laser-induced LPFG fabrication to present a more coherent understanding of the processes that occur. In addition, new evidence provides detailed information on the functional form of the RSD and the RID in LPFGs. This information is crucial for the modeling of LPFG behavior, for the design of LPFGs for specific applications, for the tailoring of fabrication parameters to meet design requirements, and for understanding the limitations of LPFG fabrication in commercial optical fibers. Future areas of research concerning the improvement of the developed methodology, the need to characterize other fibers and f

  12. Quantifying Refraction

    NSDL National Science Digital Library

    2014-09-18

    Students learn the relevant equations for refraction (index of refraction, Snell's law) and how to use them to predict the behavior of light waves in specified scenarios. After a brief review of the concept of refraction (as learned in the previous lesson), the equations along with their units and variable definitions, are introduced. Student groups work through a few example conceptual and mathematical problems and receive feedback on their work. Then students conduct the associated activity during which they practice using the equations in a problem set, examine data from a porous film like those used in biosensors, and apply the equations they learned to a hypothetical scenario involving biosensors.

  13. Mismatch Consideration in Circular Core Mono-mode Graded Index Fiber of Triangular Refractive Index Profile Excitation via Hemispherical Microlens on the Fiber Tip

    NASA Astrophysics Data System (ADS)

    Bose, Ashima; Gangopadhyay, Sankar; Saha, Subhas Chandra

    2012-12-01

    We report what, as per our knowledge, is the first theoretical investigation of the excitation efficiency in presence of possible transverse and angular misalignments in case of single-mode circular core triangular refractive index profile fiber excitation by laser diode via hemispherical microlens on the fiber tip. The present analysis takes into consideration limited aperture allowable by the hemispherical lens. Using ABCD matrix for refraction of paraxial rays by a hemispherical microlens, we prescribe analytical expressions for the coupling efficiencies in presence of the said mismatches. The evaluation of the concerned efficiencies and associated losses will require little computations. The results found will be extremely useful in the field of optimum launch optics involving such coupler.

  14. Evaluation of a quantitative structure-property relationship (QSPR) for predicting mid-visible refractive index of secondary organic aerosol (SOA).

    PubMed

    Redmond, Haley; Thompson, Jonathan E

    2011-04-21

    In this work we describe and evaluate a simple scheme by which the refractive index (? = 589 nm) of non-absorbing components common to secondary organic aerosols (SOA) may be predicted from molecular formula and density (g cm(-3)). The QSPR approach described is based on three parameters linked to refractive index-molecular polarizability, the ratio of mass density to molecular weight, and degree of unsaturation. After computing these quantities for a training set of 111 compounds common to atmospheric aerosols, multi-linear regression analysis was conducted to establish a quantitative relationship between the parameters and accepted value of refractive index. The resulting quantitative relationship can often estimate refractive index to ±0.01 when averaged across a variety of compound classes. A notable exception is for alcohols for which the model consistently underestimates refractive index. Homogenous internal mixtures can conceivably be addressed through use of either the volume or mole fraction mixing rules commonly used in the aerosol community. Predicted refractive indices reconstructed from chemical composition data presented in the literature generally agree with previous reports of SOA refractive index. Additionally, the predicted refractive indices lie near measured values we report for ? = 532 nm for SOA generated from vapors of ?-pinene (R.I. 1.49-1.51) and toluene (R.I. 1.49-1.50). We envision the QSPR method may find use in reconstructing optical scattering of organic aerosols if mass composition data is known. Alternatively, the method described could be incorporated into in models of organic aerosol formation/phase partitioning to better constrain organic aerosol optical properties. PMID:21399787

  15. Phase refractive index dispersions of organic oligomer crystals with different molecular alignments

    NASA Astrophysics Data System (ADS)

    Sakurai, Yusaku; Hayashi, Waka; Yamao, Takeshi; Hotta, Shu

    2014-02-01

    We grew slab crystals of end-capped oligothiophenes with phenyl, biphenyl, or methyl groups and unsubstituted oligophenyls. These crystals were grown in the vapor and liquid phases. We determined their dispersions and anisotropic refractive indices from interference fringes in the emission and reflectance spectra. To do this, we used pairs of parallel facets, which were naturally formed during the crystal growth or cleaved from wide crystals, as optical resonators. The unsubstituted oligophenyls indicated blue-shifted dispersions compared with the end-capped oligothiophenes. We discussed refractive indices in connection with molecular alignments in the crystals and compared them with computational results.

  16. Long Period Gratings in Random Hole Optical Fibers for Refractive Index Sensing

    PubMed Central

    Wang, Ke; Pickrell, Gary

    2011-01-01

    We have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO2 laser. The gratings with a periodicity of 450 ?m are fabricated and a maximum coupling efficiency of ?9.81 dB has been achieved. Sensing of different refractive indices in the surrounding mediums is demonstrated by applying standard liquids with refractive indices from 1.400 to 1.440 to the long period grating. PMID:22319368

  17. Long period gratings in random hole optical fibers for refractive index sensing.

    PubMed

    Wang, Ke; Pickrell, Gary

    2011-01-01

    We have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO(2) laser. The gratings with a periodicity of 450 ?m are fabricated and a maximum coupling efficiency of -9.81 dB has been achieved. Sensing of different refractive indices in the surrounding mediums is demonstrated by applying standard liquids with refractive indices from 1.400 to 1.440 to the long period grating. PMID:22319368

  18. A new bottom-up methodology to produce silicon layers with a closed porosity nanostructure and reduced refractive index.

    PubMed

    Godinho, V; Caballero-Hernández, J; Jamon, D; Rojas, T C; Schierholz, R; García-López, J; Ferrer, F J; Fernández, A

    2013-07-12

    A new approach is presented to produce amorphous porous silicon coatings (a-pSi) with closed porosity by magnetron sputtering of a silicon target. It is shown how the use of He as the process gas at moderated power (50-150 W RF) promotes the formation of closed nanometric pores during the growth of the silicon films. The use of oblique-angle deposition demonstrates the possibility of aligning and orientating the pores in one direction. The control of the deposition power allows the control of the pore size distribution. The films have been characterized by a variety of techniques, including scanning and transmission electron microscopy, electron energy loss spectroscopy, Rutherford back scattering and x-ray photoelectron spectroscopy, showing the incorporation of He into the films (most probably inside the closed pores) and limited surface oxidation of the silicon coating. The ellipsometry measurements show a significant decrease in the refractive index of porous coatings (n(500 nm) = 3.75) in comparison to dense coatings (n(500 nm) = 4.75). The capability of the method to prepare coatings with a tailored refractive index is therefore demonstrated. The versatility of the methodology is shown in this paper by preparing intrinsic or doped silicon and also depositing (under DC or RF discharge) a-pSi films on a variety of substrates, including flexible materials, with good chemical and mechanical stability. The fabrication of multilayers of silicon films of controlled refractive index in a simple (one-target chamber) deposition methodology is also presented. PMID:23764615

  19. A Method to Retrieve the Complex Refractive Index and Single Scattering Optical Properties of Dust Deposited in Mountain Snow Cover

    NASA Astrophysics Data System (ADS)

    Skiles, M.; Painter, T. H.; Okin, G. S.

    2014-12-01

    Dust on snow can have regionally important climatic and hydrologic impacts resulting from direct reduction of surface albedo and indirectly from the initiation of snow albedo feedbacks. Modeling the radiative impacts of dust deposited in snow requires knowledge of the optical properties of both components. Here we present an inversion technique to retrieve the effective optical properties of dust deposited in mountain snow cover from measurements of hemispherical dust reflectance and particle size distributions using radiative transfer modeling. First, modeled reflectance is produced from single scattering properties modeled with Mie theory for a specified grain size distribution over a range of values for the imaginary part of the complex refractive index (k=-0.00001 to -0.1). Then, a multi-step look-up table process is employed to retrieve the imaginary part of the complex index of refraction and single scattering optical properties by matching measured to modeled reflectance between 0.35 and 2.5 ?m at 10 nm resolution. The real part of the complex refractive index for dust aerosols ranges between 1.5 and 1.6 and a sensitivity analysis shows the method is relatively insensitive to the choice of n within this range, 1.525 was used here. Using the values retrieved by this method to update dust optical properties in a snow+aerosol radiative transfer model reduces errors in spring time albedo modeling by 50% to 70%, matching measured albedo to within 2% on average in the visible wavelengths and 5% over the full range of snow reflectance.

  20. Capability for Fine Tuning of the Refractive Index Sensing Properties of Long-Period Gratings by Atomic Layer Deposited Al2O3 Overlays

    PubMed Central

    ?mietana, Mateusz; My?liwiec, Marcin; Mikulic, Predrag; Witkowski, Bart?omiej S.; Bock, Wojtek J.

    2013-01-01

    This work presents an application of thin aluminum oxide (Al2O3) films obtained using atomic layer deposition (ALD) for fine tuning the spectral response and refractive-index (RI) sensitivity of long-period gratings (LPGs) induced in optical fibers. The technique allows for an efficient and well controlled deposition at monolayer level (resolution ? 0.12 nm) of excellent quality nano-films as required for optical sensors. The effect of Al2O3 deposition on the spectral properties of the LPGs is demonstrated experimentally and numerically. We correlated both the increase in Al2O3 thickness and changes in optical properties of the film with the shift of the LPG resonance wavelength and proved that similar films are deposited on fibers and oxidized silicon reference samples in the same process run. Since the thin overlay effectively changes the distribution of the cladding modes and thus also tunes the device's RI sensitivity, the tuning can be simply realized by varying number of cycles, which is proportional to thickness of the high-refractive-index (n > 1.6 in infrared spectral range) Al2O3 film. The advantage of this approach is the precision in determining the film properties resulting in RI sensitivity of the LPGs. To the best of our knowledge, this is the first time that an ultra-precise method for overlay deposition has been applied on LPGs for RI tuning purposes and the results have been compared with numerical simulations based on LP mode approximation.