Science.gov

Sample records for refractive index dispersion

  1. Extraction of complex refractive index dispersion from SPR data

    NASA Astrophysics Data System (ADS)

    Nakkach, Mohamed; Moreau, Julien; Canva, Michael

    2010-02-01

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

  2. Refractive index and dispersion variation in precision optical glass molding by computed tomography.

    PubMed

    Zhao, Wei; Chen, Yang; Shen, Lianguan; Yi, Allen Y

    2009-07-01

    Glass compression molding is an alternative manufacturing method for efficient, high-quality, low-cost optical component manufacturing. However, in compression molding, refractive index variation is inadvertently introduced to glass, which can influence optical performance of molded glass lenses, especially for lenses used in high precision applications. In order to study refractive index variation and dispersion in molded glass lenses after cooling, a group of BK7 cylindrical glass lenses were thermally treated with various heating and cooling conditions. The molded glass lenses were measured by use of an optical setup based on a Mach-Zehnder interferometer with red, green, and blue lasers separately. Using the wavefront information extracted from fringe patterns, refractive index and dispersion variation in molded glass lenses were reconstructed using a filtered backprojection algorithm. Furthermore, refractive index and dispersion variation at different cooling rates and different soaking temperatures were investigated.

  3. Influence of refractive index dispersion on pulse shaping in white-light interferometry

    NASA Astrophysics Data System (ADS)

    Lychagov, Vladislav V.; Sdobnov, Anton Y.; Ryabukho, Vladimir P.

    2015-03-01

    Particularities of interference signal shaping in white-light interferometer with uncompensated dispersive layer are discussed. We especially attended to dependence of interference pulse position on the dispersive layer properties. Phase refractive index of the layer tends to be substantially nonlinear function of wavelength within the wide emission band of ultra-low coherence thermal light source. In this case, it is the group refractive index dispersion that is beginning to exert an influence on interference signal formation. It is shown experimentally that influence consists in nonlinear dependence of interference pulse position on geometrical thickness of the dispersive layer. The results show that mismatch of the dispersive layer and compensator refractive indices in the third place can produce interference signal shift on the order of pulse width.

  4. Influence of the refractive index and dispersion of spectacle lens on its imaging properties

    NASA Astrophysics Data System (ADS)

    Miks, Antonin; Novak, Jiri; Novak, Pavel

    2007-12-01

    The paper shows an influence of the refractive index and dispersion of the spectacle lens on its imaging properties. Relations are presented for calculation of radii of curvature of anastigmatic spectacle lenses and their chromatic aberration. Moreover, the formulas are derived for calculation of the change of astigmatism of spectacle lens due to dispersion of spectacle lens material.

  5. Efficient approximations of dispersion relations in optical waveguides with varying refractive-index profiles.

    PubMed

    Li, Yutian; Zhu, Jianxin

    2015-05-01

    In this paper we consider the problem of computing the eigen-modes for the varying refractive-index profile in an open waveguide. We first approximate the refractive-index by a piecewise polynomial of degree two, and the corresponding Sturm-Liouville problem (eigenvalue problem) of the Helmholtz operator in each layer can be solved analytically by the Kummer functions. Then, analytical approximate dispersion equations are established for both TE and TM cases. Furthermore, the approximate dispersion equations converge fast to the exact ones for the continuous refractive-index function as the maximum value of the subinterval sizes tends to zero. Suitable numerical methods, such as Müller's method or the chord secant method, may be applied to the dispersion relations to compute the eigenmodes. Numerical simulations show that our method is very practical and efficient for computing eigenmodes. PMID:25969285

  6. Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

    SciTech Connect

    Hermannsson, Pétur G.; Vannahme, Christoph; Smith, Cameron L. C.; Sørensen, Kristian T.; Kristensen, Anders

    2015-08-10

    Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown that by covering the array with a sample liquid and measuring the resonance wavelength associated with transverse electric polarized quasi guided modes as a function of period, the refractive index dispersion of the liquid can be accurately obtained using an analytical expression. This method is compact, can perform measurements at arbitrary number of wavelengths, and requires only a minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications.

  7. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals

    PubMed Central

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-01-01

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals. PMID:26956377

  8. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals.

    PubMed

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-03-09

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals.

  9. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals

    NASA Astrophysics Data System (ADS)

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-03-01

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    PubMed

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

    2013-10-15

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

  12. Interband and intraband contributions to refractive index and dispersion in narrow-gap semiconductors

    NASA Astrophysics Data System (ADS)

    Herrmann, K. H.; Melzer, V.; Müller, U.

    1993-04-01

    This review covers experimental methods and results for the determination of refractive index. It discusses various empirical relations between refractive index and energy gap (Moss relation, Ravindra and Gopal formulae and the Wemple DiDomenico approach). Effects of free carriers and temperature are included. Finally, the Kramers-Kronig transformation of absorption or reflection spectra is considered.

  13. Refractive index dispersion of swift heavy ion irradiated BFO thin films using Surface Plasmon Resonance technique

    NASA Astrophysics Data System (ADS)

    Paliwal, Ayushi; Sharma, Savita; Tomar, Monika; Singh, Fouran; Gupta, Vinay

    2016-07-01

    Swift heavy ion irradiation (SHI) is an effective technique to induce defects for possible modifications in the material properties. There is growing interest in studying the optical properties of multiferroic BiFeO3 (BFO) thin films for optoelectronic applications. In the present work, BFO thin films were prepared by sol-gel spin coating technique and were irradiated using the 15 UD Pelletron accelerator with 100 MeV Au9+ ions at a fluence of 1 × 1012 ions cm-2. The as-grown films became rough and porous on ion irradiation. Surface Plasmon Resonance (SPR) technique has been identified as a highly sensitive and powerful technique for studying the optical properties of a dielectric material. Optical properties of BFO thin films, before and after irradiation were studied using SPR technique in Otto configuration. Refractive index is found to be decreasing from 2.27 to 2.14 on ion irradiation at a wavelength of 633 nm. Refractive index dispersion of BFO thin film (from 405 nm to 633 nm) before and after ion radiation was examined.

  14. Refractive index determination using the central focal masking technique with dispersion colors.

    USGS Publications Warehouse

    Wilcox, R.E.

    1983-01-01

    The procedures, precision, advantages and limitations of central focal masking ("dispersion staining'), a technique for determining the refractive indices of microfragments by the immersion method and for distinguishing between minerals in an immersion mount, are described. -J.A.Z.

  15. Colossal Light-Induced Refractive-Index Modulation for Neutrons in Holographic Polymer-Dispersed Liquid Crystals

    SciTech Connect

    Fally, Martin; Ellabban, Mostafa A.; Drevensek-Olenik, Irena; Pranzas, Klaus P.; Vollbrandt, Juergen

    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.

  16. Tunable effective nonlinear refractive index of graphene dispersions during the distortion of spatial self-phase modulation

    SciTech Connect

    Wang, Gaozhong; Zhang, Saifeng E-mail: jwang@siom.ac.cn; Cheng, Xin; Dong, Ningning; Zhang, Long; Wang, Jun E-mail: jwang@siom.ac.cn; Umran, Fadhil A.; Coghlan, Darragh; Blau, Werner J.; Cheng, Ya

    2014-04-07

    Spatial self-phase modulation (SSPM) was observed directly when a focused He-Ne laser beam at 633 nm went through liquid-phase-exfoliated graphene dispersions. The diffraction pattern of SSPM was found to be distorted rapidly right after the incident beam horizontally passing through the dispersions, while no distortion for the vertically incident geometry. We show that the distortion is originated mainly from the non-axis-symmetrical thermal convections of the graphene nanosheets induced by laser heating, and the relative change of nonlinear refractive index can be determined by the ratio of the distortion angle to the half-cone angle. Therefore, the effective nonlinear refractive index of graphene dispersions can be tuned by changing the incident intensity and the temperature of the dispersions.

  17. Determination of refractive index dispersion using fiber-optic low-coherence Fabry-Perot interferometer: implementation and validation

    NASA Astrophysics Data System (ADS)

    Karpienko, Katarzyna; Wróbel, Maciej S.; Jędrzejewska-Szczerska, Małgorzata

    2014-07-01

    We present the implementation and validation of low-coherence Fabry-Perot interferometer for refractive index dispersion measurements of liquids. A measurement system has been created with the use of four superluminescent diodes with different optical parameters, a fiber-optic coupler and an optical spectrum analyzer. The Fabry-Perot interferometer cavity has been formed by the fiber-optic end and mirror surfaces mounted on a micromechanical stage. The positive result of the validation procedure has been determined through statistical analysis. All obtained results were 99.999% statistically significant and were characterized by a strong positive correlation (r>0.98). The accuracy of the measured result of implemented low-coherence Fabry-Perot interferometer sensor is from 83% to 94%, which proves that the sensor can be used in the measurement of refractive index dispersion of liquids.

  18. 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)

  19. 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.

  20. Refractive index of air. 2. Group index.

    PubMed

    Ciddor, P E; Hill, R J

    1999-03-20

    In a previous paper [Appl. Opt. 35, 1566 (1996)] one of us presented new equations for evaluation of the phase refractive index of air over a range of wavelengths and atmospheric parameters. That paper also gave an incorrect, although sufficiently accurate, procedure for calculating the group refractive index. Here we describe the results of a more rigorous derivation of the group index that takes proper account of the Lorentz-Lorenz formula, and we demonstrate that deviations from the Lorentz-Lorenz formula are insignificant to within a foreseeable precision of dispersion measurements for atmospheric conditions. We also derive and evaluate a simplification of the resultant equation that is useful for exploratory calculations. We clarify the limits of validity of the standard equation for the group refractive index and correct some minor errors in the previous paper.

  1. Measurement of refractive index dispersion of a fused silica plate using Fabry-Perot interference.

    PubMed

    Lee, Choonghwan; Choi, Heejoo; Jin, Jonghan; Cha, Myoungsik

    2016-08-10

    We used Fabry-Perot interferometry to measure the refractive indices of a fused silica plate at four different wavelengths ranging from 544 to 1550 nm, giving a detailed analysis on the uncertainty of this experimental method. Because of a small expanded uncertainty of 2.7×10-5(k=1.96) obtained using the experimental method, it was possible to make corrections to the existing Sellmeier formula [J. Opt. Soc. Am.55, 1205 (1965)JOSAAH0030-394110.1364/JOSA.55.001205] for our fused silica sample. The corrected Sellmeier formula resulted in a group index value larger than that evaluated using the Malitson's Sellmeier formula by 3×10-4. We verified this by comparing it with the group index measured with spectral domain interferometry at 1530 nm. PMID:27534471

  2. Measurement of refractive index dispersion of a fused silica plate using Fabry-Perot interference.

    PubMed

    Lee, Choonghwan; Choi, Heejoo; Jin, Jonghan; Cha, Myoungsik

    2016-08-10

    We used Fabry-Perot interferometry to measure the refractive indices of a fused silica plate at four different wavelengths ranging from 544 to 1550 nm, giving a detailed analysis on the uncertainty of this experimental method. Because of a small expanded uncertainty of 2.7×10-5(k=1.96) obtained using the experimental method, it was possible to make corrections to the existing Sellmeier formula [J. Opt. Soc. Am.55, 1205 (1965)JOSAAH0030-394110.1364/JOSA.55.001205] for our fused silica sample. The corrected Sellmeier formula resulted in a group index value larger than that evaluated using the Malitson's Sellmeier formula by 3×10-4. We verified this by comparing it with the group index measured with spectral domain interferometry at 1530 nm.

  3. Infrared refractive index dispersion of polymethyl methacrylate spheres from Mie ripples in Fourier-transform infrared microscopy extinction spectra.

    PubMed

    Blümel, R; Bağcioğlu, M; Lukacs, R; Kohler, A

    2016-09-01

    We performed high-resolution Fourier-transform infrared (FTIR) spectroscopy of a polymethyl methacrylate (PMMA) sphere of unknown size in the Mie scattering region. Apart from a slow, oscillatory structure (wiggles), which is due to an interference effect, the measured FTIR extinction spectrum exhibits a ripple structure, which is due to electromagnetic resonances. We fully characterize the underlying electromagnetic mode structure of the spectrum by assigning mode numbers to each of the ripples in the measured spectrum. We show that analyzing the ripple structure in the spectrum in the wavenumber region from about 3000  cm-1 to 8000  cm-1 allows us to determine both the unknown radius of the sphere and the PMMA index of refraction, which shows a strong frequency dependence in this infrared spectral region. While in this paper we focus on examining a PMMA sphere as an example, our method of determining the refractive index and its dispersion from infrared extinction spectra is generally applicable for the determination of the index of refraction of any transparent substance that can be shaped into micron-sized spheres. PMID:27607489

  4. Infrared refractive index dispersion of polymethyl methacrylate spheres from Mie ripples in Fourier-transform infrared microscopy extinction spectra.

    PubMed

    Blümel, R; Bağcioğlu, M; Lukacs, R; Kohler, A

    2016-09-01

    We performed high-resolution Fourier-transform infrared (FTIR) spectroscopy of a polymethyl methacrylate (PMMA) sphere of unknown size in the Mie scattering region. Apart from a slow, oscillatory structure (wiggles), which is due to an interference effect, the measured FTIR extinction spectrum exhibits a ripple structure, which is due to electromagnetic resonances. We fully characterize the underlying electromagnetic mode structure of the spectrum by assigning mode numbers to each of the ripples in the measured spectrum. We show that analyzing the ripple structure in the spectrum in the wavenumber region from about 3000  cm-1 to 8000  cm-1 allows us to determine both the unknown radius of the sphere and the PMMA index of refraction, which shows a strong frequency dependence in this infrared spectral region. While in this paper we focus on examining a PMMA sphere as an example, our method of determining the refractive index and its dispersion from infrared extinction spectra is generally applicable for the determination of the index of refraction of any transparent substance that can be shaped into micron-sized spheres.

  5. Theoretical determination of the polarizability dispersion and the refractive index of helium

    NASA Astrophysics Data System (ADS)

    Puchalski, Mariusz; Piszczatowski, Konrad; Komasa, Jacek; Jeziorski, Bogumił; Szalewicz, Krzysztof

    2016-03-01

    The refractive index n of gaseous helium can be measured by optical interferometry so accurately that it can be used to establish a pressure standard which is expected to be superior to the current standard based on the height of a mercury column. The new standard requires knowledge of the dynamic polarizability of helium atom with accuracy significantly higher than obtainable in the best experiments, but possible to achieve computationally. Calculations of this quantity are presented at relativistic and quantum electrodynamics levels of theory including relativistic nuclear recoil effects. The uncertainties of the results are carefully estimated. Our recommended value of the dynamic polarizability at the He-Ne laser wavelength of 6329.908 Å, equal 1.39181197(14) a.u., has uncertainty at least two orders of magnitude smaller than that of recent measurements and is sufficiently accurate to establish a new pressure standard. Purely ab initio values of the refraction coefficient n are computed using our polarizability, literature values of magnetic susceptibility, and dielectric virial coefficients. It is shown that n -1 can be predicted by theory as a function of density and temperature with uncertainty of 1 ppm for pressures up to 3 MPa.

  6. Fiber optic refractive index monitor

    DOEpatents

    Weiss, Jonathan David

    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 and dispersion control of ultrafast laser inscribed waveguides in gallium lanthanum sulphide for near and mid-infrared applications.

    PubMed

    Demetriou, Giorgos; Bérubé, Jean-Philippe; Vallée, Réal; Messaddeq, Younès; Petersen, Christian R; Jain, Deepak; Bang, Ole; Craig, Chris; Hewak, Daniel W; Kar, Ajoy K

    2016-03-21

    The powerful ultrafast laser inscription technique is used to fabricate optical waveguides in gallium lanthanum sulphide substrates. For the first time the refractive index profile and the dispersion of such ultrafast laser inscribed waveguides are experimentally measured. In addition the Zero Dispersion Wavelength of both the waveguides and bulk substrate is experimentally determined. The Zero Dispersion Wavelength was determined to be between 3.66 and 3.71 μm for the waveguides and about 3.61 μm for the bulk. This work paves the way for realizing ultrafast laser inscribed waveguide devices in gallium lanthanum sulphide glasses for near and mid-IR applications. PMID:27136826

  8. Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption.

    PubMed

    Dong, Ningning; Li, Yuanxin; Zhang, Saifeng; McEvoy, Niall; Zhang, Xiaoyan; Cui, Yun; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2016-09-01

    Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of ∼103  cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials. PMID:27607941

  9. Nanosphere dispersed liquid crystals for tunable negative-zero-positive index of refraction in the optical and terahertz regimes.

    PubMed

    Khoo, I C; Werner, D H; Liang, X; Diaz, A; Weiner, B

    2006-09-01

    An analysis of aligned nematic liquid crystal cells containing core-shell nanospheres shows that it is possible to devise a new type of metamaterial whose index of refraction is tunable from negative, through zero, to positive values. The design parameters for the constituents can be scaled for application in the optical as well as very long wavelength (e.g., terahertz and microwave) regions. PMID:16902629

  10. Plasmonic crystal enhanced refractive index sensing

    SciTech Connect

    Stein, Benedikt; Devaux, Eloïse; Genet, Cyriaque Ebbesen, Thomas W.

    2014-06-23

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

  11. Index of Refraction without Geometry

    ERIC Educational Resources Information Center

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

    2006-01-01

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

  12. Physics of negative refractive index materials

    NASA Astrophysics Data System (ADS)

    Ramakrishna, S. Anantha

    2005-02-01

    In the past few years, new developments in structured electromagnetic materials have given rise to negative refractive index materials which have both negative dielectric permittivity and negative magnetic permeability in some frequency ranges. The idea of a negative refractive index opens up new conceptual frontiers in photonics. One much-debated example is the concept of a perfect lens that enables imaging with sub-wavelength image resolution. Here we review the fundamental concepts and ideas of negative refractive index materials. First we present the ideas of structured materials or meta-materials that enable the design of new materials with a negative dielectric permittivity, negative magnetic permeability and negative refractive index. We discuss how a variety of resonance phenomena can be utilized to obtain these materials in various frequency ranges over the electromagnetic spectrum. The choice of the wave-vector in negative refractive index materials and the issues of dispersion, causality and energy transport are analysed. Various issues of wave propagation including nonlinear effects and surface modes in negative refractive materials (NRMs) are discussed. In the latter part of the review, we discuss the concept of a perfect lens consisting of a slab of a NRM. This perfect lens can image the far-field radiative components as well as the near-field evanescent components, and is not subject to the traditional diffraction limit. Different aspects of this lens such as the surface modes acting as the mechanism for the imaging of the evanescent waves, the limitations imposed by dissipation and dispersion in the negative refractive media, the generalization of this lens to optically complementary media and the possibility of magnification of the near-field images are discussed. Recent experimental developments verifying these ideas are briefly covered.

  13. Refractive Index of Sodium Iodide

    SciTech Connect

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

    2012-01-01

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

  14. Refractive-index measurements by moire deflectometry.

    PubMed

    Karny, Z; Kafri, O

    1982-09-15

    A novel method for measuring refractive index of gases and liquids is presented based on moire deflectometry. We demonstrate this technique by measuring the refractive index of diluted sucrose solutions and of air at atmospheric pressure.

  15. Refractive index sensitivity characteristics near the dispersion turning point of the multimode microfiber-based Mach-Zehnder interferometer.

    PubMed

    Luo, Haipeng; Sun, Qizhen; Li, Xiaolei; Yan, Zhijun; Li, Yanpeng; Liu, Deming; Zhang, Lin

    2015-11-01

    The turning point of the refractive index (RI) sensitivity based on the multimode microfiber (MMMF) in-line Mach-Zehnder interferometer (MZI) is observed. By tracking the resonant wavelength shift of the MZI generated between the HE(11) and HE(12) modes in the MMMF, the surrounding RI (SRI) could be detected. Theoretical analysis demonstrates that the RI sensitivity will reach ±∞ on either side of the turning point due to the group effective RI difference (G) approaching zero. Significantly, the positive sensitivity exists in a very wide fiber diameter range, while the negative sensitivity can be achieved in a narrow diameter range of only 0.3 μm. Meanwhile, the experimental sensitivities and variation trend at different diameters exhibit high consistency with the theoretical results. High RI sensitivity of 10777.8 nm/RIU (RI unit) at the fiber diameter of 4.6 μm and the RI around 1.3334 is realized. The discovery of the sensitivity turning points has great significance on trace detection due to the possibility of ultrahigh RI sensitivity. PMID:26512514

  16. Urban aerosol refractive index prediction by partial molar refraction approach

    SciTech Connect

    Stelson, A.W. )

    1990-11-01

    The ambient aerosol of the polluted troposphere is a complex mixture of water, electrolytes, ionic solids, metal oxides and glasses, and carbonaceous material. Prediction of the refractive indexes of these inhomogeneous mixtures can be a formidable task. Contained within this paper is the necessary parameterization to estimate the mean real aerosol refractive index based on aerosol chemical composition and the partial molar refraction approach. This approach assumes all chemical constituents are homogeneously distributed throughout the aerosol phase. Consistency of the data is discussed, and this approach is verified by prediction of refractive indexes of NaOH-Si-O{sub 2}-H{sub 2}O mixtures. Finally, aerosol chemical composition data from the Los Angeles Basin are used to predict mean real aerosol refractive indexes. These values are compared to urban aerosol refractive indexes calculated via other techniques (light scattering).

  17. Refractive index determination by coherence scanning interferometry.

    PubMed

    Yoshino, H; Kaminski, P M; Smith, R; Walls, J M; Mansfield, D

    2016-05-20

    Coherence scanning interferometry is established as a powerful noncontact, three-dimensional, metrology technique used to determine accurate surface roughness and topography measurements with subnanometer precision. The helical complex field (HCF) function is a topographically defined helix modulated by the electrical field reflectance, originally developed for the measurement of thin films. An approach to extend the capability of the HCF function to determine the spectral refractive index of a substrate or absorbing film has recently been proposed. In this paper, we confirm this new capability, demonstrating it on surfaces of silicon, gold, and a gold/palladium alloy using silica and zirconia oxide thin films. These refractive index dispersion measurements show good agreement with those obtained by spectroscopic ellipsometry. PMID:27411157

  18. Measurement of the refractive index dispersion of As2Se3 bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range

    SciTech Connect

    Carlie, Nathan; Anheier, Norman C.; Qiao, Hong; Bernacki, Bruce E.; Phillips, Mark C.; Petit, Laticia; Musgraves, Jonathan D.; Richardson, Kathleen

    2011-05-01

    The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5–10.6 μm range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.

  19. Measurement of the refractive index dispersion of As{sub 2}Se{sub 3} bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range

    SciTech Connect

    Carlie, N.; Petit, L.; Musgraves, J. D.; Richardson, K.

    2011-05-15

    The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 {mu}m range. The instrumental error was found to be {+-}0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.

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

    PubMed

    Ciddor, Philip E

    2002-04-20

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

  1. Refractive index of plant cell walls

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  2. 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.

  3. Refractive index of rigid contact lens materials.

    PubMed

    Tranoudis, I; Efron, N

    1998-01-01

    A simple hand-held refractometer was used to measure the refractive index of 27 rigid gas permeable contact lens materials. As a general rule, lenses with refractive indices lower than 1.458 are made from fluorosilicone acrylates; lenses with refractive indices in the range of 1.458 to 1.469 are made from either fluorosilicone acrylates or silicone acrylates; and lenses with refractive indices greater than 1.469 are made from silicone acrylates. It is demonstrated how refractometry can be used by contact lens practitioners for the identification and verification of rigid contact lenses.

  4. Refractive index of the CuAlO2 delafossite

    NASA Astrophysics Data System (ADS)

    Pellicer-Porres, J.; Segura, A.; Kim, D.

    2009-01-01

    The refractive index of the CuAlO2 delafossite has been determined from interference measurements in single crystals performed in the visible, near and mid infrared regions of the spectrum. The analysis of the refractive index dispersion corresponding to light polarization perpendicular to the c-axis (P ⊥ c) yields a static dielectric constant of epsilon0 = 7.7 ± 0.8 and a low frequency electronic constant epsilon∞ = 5.1 ± 0.1. The relevant infrared active E^{\\uparrow}_u(\\rm TO) mode is found to be at 550 ± 25 cm-1. The electronic contribution can be well described by a Penn gap at 39 000 ± 1000 cm-1. Both the refractive index and its dispersion are found to be smaller for P||c than for P ⊥ c.

  5. 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.

  6. The refractive index of relic gravitons

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2016-06-01

    The dynamical evolution of the refractive index of the tensor modes of the geometry produces a specific class of power spectra characterized by a blue (i.e. slightly increasing) slope which is directly determined by the competition of the slow-roll parameter and of the rate of variation of the refractive index. Throughout the conventional stages of the inflationary and post-inflationary evolution, the microwave background anisotropies measurements, the pulsar timing limits and the big-bang nucleosynthesis constraints set stringent bounds on the refractive index and on its rate of variation. Within the physically allowed region of the parameter space the cosmic background of relic gravitons leads to a potentially large signal for the ground-based detectors (in their advanced version) and for the proposed space-borne interferometers. Conversely, the lack of direct detection of the signal will set a qualitatively new bound on the dynamical variation of the refractive index.

  7. Refractive index measurement by prism autocollimation

    NASA Astrophysics Data System (ADS)

    Cheng, Chao-Chia

    2014-03-01

    An autocollimation-based method for measuring the refractive indices of solid or liquids using a Littrow prism is presented. Measurement accuracy is enhanced by use of a telescope. In solids, the refractive index is accurate to three decimal places. Similar accuracy is obtained in liquids by correcting for the wedge angle of the liquid container window. The proposed prismatic method confers high accuracy, compactness, and automation. It is suitable for index measurement applications in undergraduate laboratories.

  8. Fiber optic liquid refractive index sensor

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Vanita; Gangwar, Rahul Kumar; Singh, Vinod Kumar

    2015-08-01

    In this present work we report fabrication of fiber optic liquid refractive index (RI) measurement sensor based on Michelson Interferometer method. This sensor was assembled by using graded index multimode (MM) fiber with core diameter 50 µm and the cladding of fiber was removed by simple chemical method. To perform this experiment a 2×2 3dB coupler is used. The fiber ends are then immersed in solvent and solution to provide reference and refractive index measurements, respectively. This method was successfully used to measure refractive index of Sodium Chloride (NaCl)-Water solution at different concentrations. The fringe contrast sensitivity of device is 92.90 dB/RIU measured in the RI range from 1.34 to 1.42 which is better than Mach-Zehnder Interferometer sensor [1] and Fabry perot based sensor [2]. The fabrication of sensor is simple, low cost and highly sensitive.

  9. 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.

  10. A Liquid Prism for Refractive Index Studies

    NASA Astrophysics Data System (ADS)

    Edmiston, Michael D.

    2001-11-01

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

  11. 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.

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

    SciTech Connect

    Smith, D. Y.; Karstens, W.

    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.

  13. Dispersion of the refractive index of a samarium-doped Se{sup 95}Te{sup 5} chalcogenide glassy semiconductor

    SciTech Connect

    Atayeva, S. U. Mekhtiyeva, S. I.; Isayev, A. I.

    2015-07-15

    The transmission spectrum of a Se{sup 95}Te{sup 5} chalcogenide glassy semiconductor doped with samarium (0.05, 0.1, 0.25, 0.5, and 1 at %) is studied; the Swanepoel method and the single-oscillator model are used to determine the oscillator energy E{sup 0}, dispersion energy E{sup d}, optical width of the band gap E{sup g}, and linear (n) and nonlinear (n{sup 2}) refractive indices. The changes in the values of these parameters as a result of doping are attributed to modification of the local structure and to a change in the concentration of defect states.

  14. Two-dimensional refractive index profiling of optical fibers by modified refractive near-field technique

    NASA Astrophysics Data System (ADS)

    El Sayed, A.; Pilz, Soenke; Ryser, Manuel; Romano, Valerio

    2016-02-01

    The refractive index distribution in the core-cladding region of an optical fiber plays an important role in determining the transmission and dispersion properties of the waveguide. The refracted near-field technique (RNF) is among the most widespread techniques used for measuring the refractive index profile of optical fibers and is based on illuminating the end-facet of a fiber with a focused beam whose vertex angle greatly exceeds the acceptance angle of the fiber, which is immersed in an index matching liquid. What one observes are then the refracted unguided rays rather than the guided rays. Nevertheless, the standard refracted near-field technique cannot be applied to a wide range of optical fibers e.g. if their shapes are not axially symmetric. In this work we demonstrate a modified method which allows 2-D imaging of the refractive index profile and thereby overcoming the axial symmetric limitation of the standard RNF. The new system is operating at 630 nm and based on the same principle of the RNF, but the optical path is reversed so that the light at the fiber end-facet is collected by an objective lens and detected by a CCD camera. The method does not require scanning over the fiber end-facet. Thus the system is faster and less sensitive to vibrations and external conditions compared to the standard RNF, furthermore it allows averaging to improve the signal to noise ratio. The spatial resolution of the system is determined by the numerical aperture of the objective and by the resolution of the CCD camera. To calibrate the setup, a reference multi-step index fiber provided by National Physical Laboratory was used.

  15. Two-dimensional refractive index profiling of optical fibers by modified refractive near-field technique

    NASA Astrophysics Data System (ADS)

    El Sayed, A.; Pilz, Soenke; Ryser, Manuel; Romano, Valerio

    2016-04-01

    The refractive index distribution in the core-cladding region of an optical fiber plays an important role in determining the transmission and dispersion properties of the waveguide. The refracted near-field technique (RNF) is among the most widespread techniques used for measuring the refractive index profile of optical fibers and is based on illuminating the end-facet of a fiber with a focused beam whose vertex angle greatly exceeds the acceptance angle of the fiber, which is immersed in an index matching liquid. What one observes are then the refracted unguided rays rather than the guided rays. Nevertheless, the standard refracted near-field technique cannot be applied to a wide range of optical fibers e.g. if their shapes are not axially symmetric. In this work we demonstrate a modified method which allows 2-D imaging of the refractive index profile and thereby overcoming the axial symmetric limitation of the standard RNF. The new system is operating at 630 nm and based on the same principle of the RNF, but the optical path is reversed so that the light at the fiber end-facet is collected by an objective lens and detected by a CCD camera. The method does not require scanning over the fiber end-facet. Thus the system is faster and less sensitive to vibrations and external conditions compared to the standard RNF, furthermore it allows averaging to improve the signal to noise ratio. The spatial resolution of the system is determined by the numerical aperture of the objective and by the resolution of the CCD camera. To calibrate the setup, a reference multi-step index fiber provided by National Physical Laboratory was used.

  16. Interferometric atmospheric refractive-index environmental monitor.

    PubMed

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

    1995-06-20

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

  17. A FORTRAN Program for Computing Refractive Index Using the Double Variation Method.

    ERIC Educational Resources Information Center

    Blanchard, Frank N.

    1984-01-01

    Describes a computer program which calculates a best estimate of refractive index and dispersion from a large number of observations using the double variation method of measuring refractive index along with Sellmeier constants of the immersion oils. Program listing with examples will be provided on written request to the author. (Author/JM)

  18. Matched Index of Refraction Flow Facility

    SciTech Connect

    Mcllroy, Hugh

    2010-01-01

    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.

  19. Matched Index of Refraction Flow Facility

    ScienceCinema

    Mcllroy, Hugh

    2016-07-12

    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.

  20. 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.

  1. Scanning focused refractive-index microscopy

    PubMed Central

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

    2014-01-01

    We present a novel scanning focused refractive-index microscopy (SFRIM) technique to obtain the refractive index (RI) profiles of objects. The method uses a focused laser as the light source, and combines the derivative total reflection method (DTRM), projection magnification, and scanning technique together. SFRIM is able to determine RIs with an accuracy of 0.002, and the central spatial resolution achieved is 1 µm, which is smaller than the size of the focal spot. The results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, verifying the accuracy of SFRIM. Furthermore, using SFRIM, to the best of our knowledge we have extracted for the first time the RI profile of a periodically modulated photosensitive gelatin sample. SFRIM is the first RI profile-resolved reflected light microscopy technique that can be applied to scattering and absorbing samples. SFRIM enables the possibility of performing RI profile measurements in a variety of applications, including optical waveguides, photosensitive materials and devices, photorefractive effect studies, and RI imaging in biomedical fields. PMID:25008374

  2. Scanning focused refractive-index microscopy.

    PubMed

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

    2014-01-01

    We present a novel scanning focused refractive-index microscopy (SFRIM) technique to obtain the refractive index (RI) profiles of objects. The method uses a focused laser as the light source, and combines the derivative total reflection method (DTRM), projection magnification, and scanning technique together. SFRIM is able to determine RIs with an accuracy of 0.002, and the central spatial resolution achieved is 1 µm, which is smaller than the size of the focal spot. The results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, verifying the accuracy of SFRIM. Furthermore, using SFRIM, to the best of our knowledge we have extracted for the first time the RI profile of a periodically modulated photosensitive gelatin sample. SFRIM is the first RI profile-resolved reflected light microscopy technique that can be applied to scattering and absorbing samples. SFRIM enables the possibility of performing RI profile measurements in a variety of applications, including optical waveguides, photosensitive materials and devices, photorefractive effect studies, and RI imaging in biomedical fields. PMID:25008374

  3. Tissue refractive index as marker of disease

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  4. Experimental determination of the refractive index of metamaterials

    NASA Astrophysics Data System (ADS)

    Nielsen, Michael G.; Pors, Anders; Albrektsen, Ole; Willatzen, Morten; Bozhevolnyi, Sergey I.

    2011-05-01

    We present a simple experimental technique based on diffraction for determining the complex refractive index of metamaterials, and demonstrate it with metamaterials that consist of detuned electrical dipoles (DEDs), mimicking the dressed-state picture of electromagnetically induced transparency (EIT). The metamaterials are realized by fabricating lithographically defined gold nanorods on a silica substrate, covered with a ~ 15 µm thick polymer layer, and feature EIT-like transmission spectra with transparency windows centered at wavelengths near ~ 800 nm. The refractive indices are determined for wavelengths where the DED metamaterials exhibit enhanced transmission. Thereby, we experimentally demonstrate normal dispersion in the transmission window and estimate the group refractive index to ~ 3.6. Furthermore, finite-element simulations are conducted on a monolayer of DED unit cells, which similarly exhibit the EIT-like behavior in terms of enhanced transmission revealed in the transmission spectra. Simulated transmission and reflection spectra are utilized for calculations of the real and imaginary parts of the metamaterial refractive index, showing consistent trends with those obtained experimentally.

  5. Measurement of refractive index distribution of biotissue by scanning focused refractive index microscopy

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    A novel scanning focused refractive-index microscopy (SFRIM) technique are presented. With a focused laser serves as the light source, we combine the derivative total reflection method (DTRM), microscopy and the scanning technique together to obtain the refractive-index profiles (RIP) of objects. The refractive index (RI) accuracy is 0.002. The central spatial resolution of SFRIM achieves 1 μm , smaller than the size of the focal spot. Results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, thereby verifying the accuracy of SFRIM. Refractive index distribution of biotissue are measured by this microscopy. The use of SFRIM opens up possibilities for RIP measurement in many applications, including optical waveguides, photosensitive materials and devices, the study of the photorefractive effect, and RI imaging in biomedical fields. This research is supported by the Chinese National Key Basic Research Special Fund (Grant No.2011CB922003), Science and Technology Program of Tianjin (Grant No.11ZCKFSY00500).

  6. Optical electronegativity and refractive index of materials

    NASA Astrophysics Data System (ADS)

    Reddy, R. R.; Nazeer Ahammed, Y.; Rama Gopal, K.; Raghuram, D. V.

    1998-05-01

    Simple correlations between the energy gap, optical electronegativity and the refractive index are given for various classes of materials such as semiconductors, insulators and oxides. There has been no report in the literature on the direct estimation of optical electronegativity for the wide variety of materials using energy gap values. The present method performance is compared with Moss and Ravindra's relationships. A simple analysis on the average percentage deviation for low and high n value materials is also presented. The average percentage deviation in the present approach reveals that the method proposed proves its identity and soundness compared to that of Moss and Ravindra's relationships. A good agreement is observed between the computed and literature values of refractive indices.

  7. Measurement of complex refractive index of turbid media by scanning focused refractive index.

    PubMed

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

    2016-08-15

    We present the application of scanning focused refractive index microscopy in the complex refractive index measurement of turbid media. An extra standard scattering layer is placed in front of the detector to perform scattering transformation on the reflected light. The principle of the scattering transformation is elaborated theoretically. The influence of the sample scattering is deeply and effectively suppressed experimentally. As a proof of the feasibility and accuracy of the proposed method, we demonstrate experimental data of 20% and 30% Intralipid solutions that are commonly used as phantom media for light propagation studies.

  8. Effects of refractive index on glories.

    PubMed

    Laven, Philip

    2008-12-01

    Atmospheric glories are caused by backscattering of sunlight from spherical droplets of water (e.g., from fog or clouds). But what would glories look like if they were caused by scattering from more exotic substances, such as clouds of ethane as found on Titan? Examining backscattering as a function of the refractive index n of spherical droplets leads to the surprising conclusion that a glory's appearance is almost independent of n (at least for 1.03

  9. Effects of refractive index on glories.

    PubMed

    Laven, Philip

    2008-12-01

    Atmospheric glories are caused by backscattering of sunlight from spherical droplets of water (e.g., from fog or clouds). But what would glories look like if they were caused by scattering from more exotic substances, such as clouds of ethane as found on Titan? Examining backscattering as a function of the refractive index n of spherical droplets leads to the surprising conclusion that a glory's appearance is almost independent of n (at least for 1.03

  10. Methods for Prediction of Refractive Index in Glasses for the Infrared

    SciTech Connect

    McCloy, John S.

    2011-06-14

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

  11. Optofluidic two-dimensional grating volume refractive index sensor.

    PubMed

    Sarkar, Anirban; Shivakiran Bhaktha, B N; Khastgir, Sugata Pratik

    2016-09-10

    We present an optofluidic reservoir with a two-dimensional grating for a lab-on-a-chip volume refractive index sensor. The observed diffraction pattern from the device resembles the analytically obtained fringe pattern. The change in the diffraction pattern has been monitored in the far-field for fluids with different refractive indices. Reliable measurements of refractive index variations, with an accuracy of 6×10-3 refractive index units, for different fluids establishes the optofluidic device as a potential on-chip tool for monitoring dynamic refractive index changes. PMID:27661360

  12. Optofluidic two-dimensional grating volume refractive index sensor.

    PubMed

    Sarkar, Anirban; Shivakiran Bhaktha, B N; Khastgir, Sugata Pratik

    2016-09-10

    We present an optofluidic reservoir with a two-dimensional grating for a lab-on-a-chip volume refractive index sensor. The observed diffraction pattern from the device resembles the analytically obtained fringe pattern. The change in the diffraction pattern has been monitored in the far-field for fluids with different refractive indices. Reliable measurements of refractive index variations, with an accuracy of 6×10-3 refractive index units, for different fluids establishes the optofluidic device as a potential on-chip tool for monitoring dynamic refractive index changes.

  13. Infrared refractive index of atmospheric aerosol substances.

    PubMed

    Volz, F E

    1972-04-01

    The optical constants in the ir from lambda2.5 microm to 40 microm (4000-250 cm(-1)) of dry natural aerosol substances and of sea salt are presented. The aerosol substances were obtained from rain and snow water: dust and soot by sedimentation, and water soluble salts by evaporation. The spectra of the absorption index n' were derived from our published transmittance measurements of potassium bromide disks. The real part n of the refractive index was calculated from the specular reflectance at near normal incidence of disks of pure aerosol substance. The observed spectral features are being related to chemical constituents, notably sulfates and alcohol soluble organics. Optical constants of composite and wet aerosol are discussed. A simple model confirms the measured transmission of a coarse dry powder of water solubles and shows that the extinction by natural aerosol should have a minimum near 8 microm and a strong maximum near 9 microm.

  14. Imaging based refractometer for hyperspectral refractive index detection

    SciTech Connect

    Baba, Justin S.; Boudreaux, Philip R.

    2015-11-24

    Refractometers for simultaneously measuring refractive index of a sample over a range of wavelengths of light include dispersive and focusing optical systems. An optical beam including the range of wavelengths is spectrally spread along a first axis and focused along a second axis so as to be incident to an interface between the sample and a prism at a range of angles of incidence including a critical angle for at least one wavelength. An imaging detector is situated to receive the spectrally spread and focused light from the interface and form an image corresponding to angle of incidence as a function of wavelength. One or more critical angles are identified and corresponding refractive indices are determined.

  15. A Simple Method to Determine the Refractive Index of Glass.

    ERIC Educational Resources Information Center

    Mak, Se-yuen

    1988-01-01

    Describes an experiment for determining the refractive index. Discusses the experiment procedure and mathematical expression for calculating the index. Provides two geometrical diagrams and a graph for determining the index with a typical data. (YP)

  16. Determination of the refractive index of glucose-ethanol-water mixtures using spectroscopic refractometry near the critical angle.

    PubMed

    Sobral, H; Peña-Gomar, M

    2015-10-01

    A spectroscopic refractometer was used to investigate the dispersion curves of ethanol and D-glucose solutions in water near the critical angle; here, the reflectivity was measured using a white source. Dispersion curves were obtained in the 320-1000 nm wavelength range with a resolution better than 10(-4) for the refractive index, n. The differential refractive index is measured as a function of wavelength, and a simple expression is proposed to obtain the refractive index of the glucose-ethanol-water ternary system. Using this expression, combined with the experimental differential refractive index values, the concentrations of individual components can be calculated.

  17. Determination of the refractive index of glucose-ethanol-water mixtures using spectroscopic refractometry near the critical angle.

    PubMed

    Sobral, H; Peña-Gomar, M

    2015-10-01

    A spectroscopic refractometer was used to investigate the dispersion curves of ethanol and D-glucose solutions in water near the critical angle; here, the reflectivity was measured using a white source. Dispersion curves were obtained in the 320-1000 nm wavelength range with a resolution better than 10(-4) for the refractive index, n. The differential refractive index is measured as a function of wavelength, and a simple expression is proposed to obtain the refractive index of the glucose-ethanol-water ternary system. Using this expression, combined with the experimental differential refractive index values, the concentrations of individual components can be calculated. PMID:26479623

  18. Calculation of electron wave functions and refractive index of Ne

    NASA Astrophysics Data System (ADS)

    Zhu, Min; Liu, Wei; Zhang, Tao

    2008-10-01

    The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical method and tested by calculating the ground state energy of the Ne atom. The equivalent volume of electron cloud and the refractive index of Ne were calculated. The calculated refractive index agrees well with the experimental result. Relationship between the refractive index and the wave function of Ne was discovered.

  19. Refractive index of Al3C2B48 aluminum borocarbide crystals

    NASA Astrophysics Data System (ADS)

    Shelykh, A. I.; Gurin, V. N.; Nikanorov, S. P.

    2008-07-01

    Aluminum borocarbide single crystals have been grown from an Al-based solution melt. The crystal lattice parameters have been determined, the dispersion of the refractive index in a 0.55 1.3 μm wavelength interval has been studied, and the temperature coefficient of the refractive index in a 300 600 K range has been measured. The crystals are characterized by a high refractive index in the visible spectral range in combination with at a high hardness, which makes them of interest for jewelry, as well as for both traditional and X-ray optics.

  20. Refractive phenomena in the shock wave dispersion with variable gradients

    SciTech Connect

    Markhotok, A.; Popovic, S.

    2010-06-15

    In this article the refraction effects in the weak shock wave (SW) dispersion on an interface with a temperature variation between two mediums are described. In the case of a finite-gradient boundary, the effect of the SW dispersion is remarkably stronger than in the case of a step change in parameters. In the former case the vertical component of velocity for the transmitted SW (the refraction effect) must be taken into account. Results of comparative calculations based on the two-dimensional model corrected for the refraction effect show significant differences in the shapes of the dispersed SW fronts.

  1. Quantum radiation from superluminal refractive-index perturbations.

    PubMed

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

    2010-04-01

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

  2. String and Sticky Tape Experiments: Refractive Index of Liquids.

    ERIC Educational Resources Information Center

    Edge, R. D., Ed.

    1979-01-01

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

  3. Measurement of Refractive Index Using a Michelson Interferometer.

    ERIC Educational Resources Information Center

    Fendley, J. J.

    1982-01-01

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

  4. A covariant approach to the gravitational refractive index

    NASA Astrophysics Data System (ADS)

    Simaciu, I.; Ionescu-Pallas, N.

    A covariant formulation of the Maxwell's field equations in a gravitational field, based on the bimetric interpretation of general relativity Theory, is given. The purpose of the work is in adequate definition of the gravitational refractive index in agreement with both wave equations propagation and a relationship between refractive index and the Minkovskian tensor of gravitational permitivity.

  5. Development of high refractive index Cherenkov detectors

    NASA Astrophysics Data System (ADS)

    Nazzal, Samah Suheil

    High refractive index materials have been investigated for use as Cherenkov media in order to develop a Cherenkov detector with a lower energy threshold. Several materials were surveyed and cubic zirconium was selected for further study. Samples of cubic zirconium were prepared and mated with photomultiplier tubes to form Cherenkov detectors. These detectors were tested using radioactive sources and muons in the laboratory and using protons at the Indiana Cyclotron in order to determine the Cherenkov light yield and to investigate contamination of the Cherenkov signal by scintillation. The results of the experimental tests were analyzed and compared to detailed numerical simulations. It was found that while some scintillation light was produced by ionizing particles in the cubic zirconium, Cherenkov light was detected at levels that make cubic zirconium usable as a Cherenkov detector. During this investigation, it was discovered that while the Cherenkov light signal was prompt with a rapid decay time, the scintillation light signal was slower both in rise time and in decay. This discovery offers the possibility to distinguish the Cherenkov and Scintillation signals.

  6. Precise determination of the refractive index of suspended particles: light transmission as a function of refractive index mismatch

    NASA Astrophysics Data System (ADS)

    McClymer, J. P.

    2016-08-01

    Many fluids appear white because refractive index differences lead to multiple scattering. In this paper, we use safe, low-cost commercial index matching fluids to quantitatively study light transmission as a function of index mismatch, reduce multiple scattering to allow single scattering probes, and to precisely determine the index of refraction of suspended material. The transmission profile is compared with Rayleigh-Gans and Mie theory predictions. The procedure is accessible as a student laboratory project, while providing advantages over other standard methods of measuring the refractive index of an unknown nanoparticle, making it valuable to researchers.

  7. Effect of refractive dispersion on the trichromatic correlation of irradiances for atmospheric scintillation.

    PubMed

    Hill, R J; Lataitis, R J

    1989-10-01

    Formulations of the trichromatic correlation of scintillating irradiance are corrected by introducing the cospectrum of the two different refractive indices in place of the refractive index power spectrum. Receiver aperture averaging is included in the formulation. The effect of dispersion on the bichromatic correlation coefficient is studied and quantified for four specific experimental cases. Dispersion of the water vapor refractive index between wavelengths in the visible and 10 microm window is of particular significance in this study. In most cases, the effect of dispersion on the bichromatic correlation coefficient is much less than on the ratio of monochromatic irradiance correlations, and is negligible for practical considerations. The exception is the case of such strong humidity fluctuations that they (as opposed to temperature fluctuations) cause most of the scintillation of the midinfrared radiation.

  8. 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.

  9. 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.

  10. Dependence of the Radiation Pressure on the Background Refractive Index

    NASA Astrophysics Data System (ADS)

    Webb, Kevin J.

    2013-07-01

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

  11. Optical tomography for smooth-changing refraction index distribution

    NASA Astrophysics Data System (ADS)

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

    2002-06-01

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

  12. Refractive index gratings in electro-optic polymer thin films.

    PubMed

    Bogunovic, D; Raymond, S G; Janssens, S; Clarke, D; Bodley, O; Ashforth, S; Simpson, M C; Quilty, J W

    2016-06-10

    Refractive index gratings have been inscribed in polymer thin films by permanently photobleaching the organic chromophore PYR-3 dopant. The grating inscription process was investigated in detail for the purpose of improving the diffraction efficiency (η) of the PYR-3 doped polymer gratings. Three processes were identified that contributed to the η of the first diffracted order: a periodic change in the refractive index due to photobleaching of the PYR-3, formation of the surface relief grating as a consequence of free volume change during bleaching, and the introduction of periodic, strain-induced changes in the refractive index.

  13. Charged-particle acceleration through decreasing refractive index

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  14. Refractive index and temperature nanosensor with plasmonic waveguide system

    NASA Astrophysics Data System (ADS)

    Kong, Yan; Qiu, Peng; Wei, Qi; Quan, Wei; Wang, Shouyu; Qian, Weiying

    2016-07-01

    A surface plasmon polariton sensor consisting of two metal-insulator-metal waveguides and a transverse rectangular resonator is proposed. Both refractive index and temperature sensing characteristics are analyzed by investigating the transmission spectra which demonstrates that the transmission peak wavelength shifting satisfies linear relation with environmental refractive index and temperature, respectively. The proposed design provides high refractive index and temperature sensitivity as 3.38×106%/RIU and 82%/K estimated by integrated response of the sensor, and owns the potentials for high-throughput array sensing. It is believed that the nanoscale sensor can be applied in spot detection for high speed multi-parameter sensing and accurate measurements.

  15. Mechanism of the photoinduced refractive index increase in polymethyl methacrylate.

    PubMed

    Bowden, M J; Chandross, E A; Kaminow, I P

    1974-01-01

    Polymethyl methacrylate prepared under special circumstances exhibits a substantial increase in refractive index after irradiation with uv light. The essential step in the preparation is peroxidation of the monomer prior to polymerization. This increase in refractive index results from a photoinduced polymerization of unreacted monomer (1-2%) within the film which produces an increase in density (and hence refractive index) in the irradiated region. It is believed that peroxides, both polymeric and monomeric, act as photoinitiators. Sensitivity depends on the concentration of photoinitiator, but the absolute value of Deltan depends on the amount of unreacte monomer.

  16. 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

  17. 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…

  18. Media with zero refractive index at a preset frequency

    NASA Astrophysics Data System (ADS)

    Averbukh, B. B.

    2015-12-01

    The refraction of a plane s-polarized electromagnetic wave on the vacuum-metamaterial interface is considered. It is established that, under certain conditions, a medium consisting of electric and magnetic dipoles or entirely of electric dipoles can behave as possessing a zero refractive index at a preset frequency.

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

    ERIC Educational Resources Information Center

    Krueger, David A.

    1980-01-01

    Presents an experiment on the bending of light in a medium with a continuously varying index of refraction. Several theoretical approaches for the analysis of this experiment, designed for college physics students, are also presented. (HM)

  20. 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.

  1. 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.

  2. Theoretical schemes for negative refraction and enhanced refractive index in atomic systems

    NASA Astrophysics Data System (ADS)

    Sikes, Daniel E.

    In this thesis we present a scheme for negative refraction in atomic systems. Negative refraction was predicted over 4 decades ago and recently experimentally demonstrated in the field of metamaterials. We seek a new approach for negative refraction using laser driven transition resonances in atomic systems. By utilizing atomic resonances we hope to achieve negative refraction in short wavelength regimes, such as visible and ultra-violet, and eliminate absorption by quantum interference. This scheme is based on the experimentally demonstrated "refractive index enhancement with vanishing absorption" technique, in which closely spaced absorptive and amplifying transitions are interfered. Our scheme utilizes Raman transitions and is able to drive an electric resonance while far-detuned from an electric-dipole transition. This far-off resonance feature allows our scheme to be adaptable to various atomic energy level structures, in that it does not require the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman transitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross coupling. Analytical predictions have been made for a model atomic system and their validity has been confirmed with exact numerical simulations of the density matrix. We consider possible experimental implementations of the scheme in rare-earth atomic systems, such as ultracold vapors and doped crystals. We also discuss applications of negative and enhanced refractive index for imaging. A fundamental challenge of imaging systems is the diffraction limit, which causes spatial features of an object smaller than the light wavelength to be lost in the image. Achieving negative refraction with vanishing absorption is important for near-perfect imaging systems based on Pendry's suggestion for a negative index perfect lens. A perfect lens is

  3. Photoresist Exposure Parameter Extraction from Refractive Index Change during Exposure

    NASA Astrophysics Data System (ADS)

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

    1998-12-01

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

  4. Plasmas with index of refraction greater than one

    SciTech Connect

    Nilsen, J; Scofield, J H

    2004-06-23

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

  5. 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.

  6. High-precision broadband measurement of refractive index by picosecond real-time interferometry.

    PubMed

    Tan, Zheng Jie; Jin, Dafei; Fang, Nicholas X

    2016-08-20

    The refractive index is one of the most important quantities that characterize a material's optical properties. However, it is hard to measure this value over a wide range of wavelengths. Here, we demonstrate a new technique to achieve a spectrally broad refractive index measurement. When a broadband pulse passes through a sample, different wavelengths experience different delays. By comparing the delayed pulse to a reference pulse, the zero path difference position for each wavelength can be obtained and the material's dispersion can be retrieved. Our technique is highly robust and accurate, and can be miniaturized in a straightforward manner. PMID:27556980

  7. High-precision broadband measurement of refractive index by picosecond real-time interferometry.

    PubMed

    Tan, Zheng Jie; Jin, Dafei; Fang, Nicholas X

    2016-08-20

    The refractive index is one of the most important quantities that characterize a material's optical properties. However, it is hard to measure this value over a wide range of wavelengths. Here, we demonstrate a new technique to achieve a spectrally broad refractive index measurement. When a broadband pulse passes through a sample, different wavelengths experience different delays. By comparing the delayed pulse to a reference pulse, the zero path difference position for each wavelength can be obtained and the material's dispersion can be retrieved. Our technique is highly robust and accurate, and can be miniaturized in a straightforward manner.

  8. Measuring cylindrically symmetric refractive-index profiles: a method.

    PubMed

    Gregoris, D; Iizuka, K

    1983-02-01

    This paper describes a new nondestructive method to measure cylindrically symmetric refractive-index profiles of transparent cylinders. The technique is based on the measurement of the axial displacement of rays that are refracted within the cylinder. Three different types of index profile were experimentally determined. Profile errors of better than one part in 10(3) were achieved using very modest equipment. The effects of certain experimental parameters on the profile accuracy are noted. The technique may be applied to the characterization of optical fiber preforms and graded-index rod lenses. PMID:18195804

  9. Perfect control of reflection and refraction using spatially dispersive metasurfaces

    NASA Astrophysics Data System (ADS)

    Asadchy, V. S.; Albooyeh, M.; Tcvetkova, S. N.; Díaz-Rubio, A.; Ra'di, Y.; Tretyakov, S. A.

    2016-08-01

    Nonuniform metasurfaces (electrically thin composite layers) can be used for shaping refracted and reflected electromagnetic waves. However, known design approaches based on the generalized refraction and reflection laws do not allow realization of perfectly performing devices: there are always some parasitic reflections into undesired directions. In this paper we introduce and discuss a general approach to the synthesis of metasurfaces for full control of transmitted and reflected plane waves and show that perfect performance can be realized. The method is based on the use of an equivalent impedance matrix model which connects the tangential field components at the two sides on the metasurface. With this approach we are able to understand what physical properties of the metasurface are needed in order to perfectly realize the desired response. Furthermore, we determine the required polarizabilities of the metasurface unit cells and discuss suitable cell structures. It appears that only spatially dispersive metasurfaces allow realization of perfect refraction and reflection of incident plane waves into arbitrary directions. In particular, ideal refraction is possible only if the metasurface is bianisotropic (weak spatial dispersion), and ideal reflection without polarization transformation requires spatial dispersion with a specific, strongly nonlocal response to the fields.

  10. Refractive index dependence of Papilio Ulysses butterfly wings reflectance spectra

    NASA Astrophysics Data System (ADS)

    Isnaeni, Muslimin, Ahmad Novi; Birowosuto, Muhammad Danang

    2016-02-01

    We have observed and utilized butterfly wings of Papilio Ulysses for refractive index sensor. We noticed this butterfly wings have photonic crystal structure, which causes blue color appearance on the wings. The photonic crystal structure, which consists of cuticle and air void, is approximated as one dimensional photonic crystal structure. This photonic crystal structure opens potential to several optical devices application, such as refractive index sensor. We have utilized small piece of Papilio Ulysses butterfly wings to characterize refractive index of several liquid base on reflectance spectrum of butterfly wings in the presence of sample liquid. For comparison, we simulated reflectance spectrum of one dimensional photonic crystal structure having material parameter based on real structure of butterfly wings. We found that reflectance spectrum peaks shifted as refractive index of sample changes. Although there is a slight difference in reflectance spectrum peaks between measured spectrum and calculated spectrum, the trend of reflectance spectrum peaks as function of sample's refractive index is the similar. We assume that during the measurement, the air void that filled by sample liquid is expanded due to liquid pressure. This change of void shape causes non-similarity between measured spectrum and calculated spectrum.

  11. On the anodic aluminium oxide refractive index of nanoporous templates

    NASA Astrophysics Data System (ADS)

    Hierro-Rodriguez, A.; Rocha-Rodrigues, P.; Valdés-Bango, F.; Alameda, J. M.; Jorge, P. A. S.; Santos, J. L.; Araujo, J. P.; Teixeira, J. M.; Guerreiro, A.

    2015-11-01

    In the present study, we have determined the intrinsic refractive index of anodic aluminium oxide, which is originated by the formation of nanoporous alumina templates. Different templates have been fabricated by the conventional two-step anodization procedure in oxalic acid. Their porosities were modified by chemical wet etching allowing the tuning of their effective refractive indexes (air-filled nanopores  +  anodic aluminium oxide). By standard spectroscopic light transmission measurements, the effective refractive index for each different template was extracted in the VIS-NIR region. The determination of the intrinsic anodic aluminium oxide refractive index was performed by using the Maxwell-Garnett homogenization theory. The results are coincident for all the fabricated samples. The obtained refractive index (~1.55) is quite lower (~22%) than the commonly used Al2O3 handbook value (~1.75), showing that the amorphous nature of the anodic oxide structure strongly conditions its optical properties. This difference is critical for the correct design and modeling of optical plasmonic metamaterials based on anodic aluminium oxide nanoporous templates.

  12. Measurement of the refractive index of hemoglobin solutions for a continuous spectral region

    PubMed Central

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

    2015-01-01

    Determination of the refractive index of hemoglobin solutions over a wide wavelength range remains challenging. A famous detour approach is the Kramers-Kronig (KK) analysis which can resolve the real part of complex refractive index from the imaginary part. However, KK analysis is limited by the contradiction between the requirement of semi-infinite frequency range and limited measured range. In this paper, based on the Multi-curve fitting method (MFM), continuous refractive index dispersion (CRID) of oxygenated and deoxygenated hemoglobin solutions are measured using a homemade symmetrical arm-linked apparatus in the continuous wavelength range with spectral resolution of about 0.259nm. A novel method to obtain the CRID is proposed. PMID:26203379

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  15. Development and characterization of high refractive index and high scattering acrylate polymer layers

    NASA Astrophysics Data System (ADS)

    Eiselt, Thomas; Gomard, Guillaume; Preinfalk, Jan; Gleissner, Uwe; Lemmer, Uli; Hanemann, Thomas

    2016-04-01

    The aim is to develop a polymer layer which has the ability to diffuse light homogeneously and exhibit a high refractive index. The mixtures are containing an acrylate casting resin, benzylmethacrylate, phenanthrene and other additives. Phenanthrene is employed to increase the refractive index. The mixtures are first rheologically characterized and then polymerized with heat and UV radiation. For the refractive index measurements the polymerized samples require a planar surface without air bubbles. To produce flat samples a special construction consisting of a glass plate, a teflon sheet, a silicone ring (PDMS mold), another teflon sheet and another glass plate is developed. Glue clamps are used to fix this construction together. Selected samples have a refractive index of 1.585 at 20°C at a wavelength of 589nm. A master mixture with a high refractive index is taken for further experiments. Nano scaled titanium dioxide is added and dispersed into the master mixture and then spin coated on a glass substrate. These layers are optically characterized. The specular transmission and the overall transmission are measured to investigate the degree of scattering, which is defined as the haze. Most of the presented layers express the expected haze of over 50%.

  16. Enhanced Nonlinear Refractive Index in ε-Near-Zero Materials.

    PubMed

    Caspani, L; Kaipurath, R P M; Clerici, M; Ferrera, M; Roger, T; Kim, J; Kinsey, N; Pietrzyk, M; Di Falco, A; Shalaev, V M; Boltasseva, A; Faccio, D

    2016-06-10

    New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n_{2}) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.

  17. Enhanced Nonlinear Refractive Index in ε-Near-Zero Materials.

    PubMed

    Caspani, L; Kaipurath, R P M; Clerici, M; Ferrera, M; Roger, T; Kim, J; Kinsey, N; Pietrzyk, M; Di Falco, A; Shalaev, V M; Boltasseva, A; Faccio, D

    2016-06-10

    New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n_{2}) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics. PMID:27341234

  18. Empirical modelling to predict the refractive index of human blood

    NASA Astrophysics Data System (ADS)

    Yahya, M.; Saghir, M. Z.

    2016-02-01

    Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient’s condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy.

  19. Empirical modelling to predict the refractive index of human blood.

    PubMed

    Yahya, M; Saghir, M Z

    2016-02-21

    Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient's condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy.

  20. 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

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

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Frey, Bradley J.

    2006-01-01

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

  2. Overcoming losses with gain in a negative refractive index metamaterial.

    PubMed

    Wuestner, Sebastian; Pusch, Andreas; Tsakmakidis, Kosmas L; Hamm, Joachim M; Hess, Ortwin

    2010-09-17

    On the basis of a full-vectorial three-dimensional Maxwell-Bloch approach we investigate the possibility of using gain to overcome losses in a negative refractive index fishnet metamaterial. We show that appropriate placing of optically pumped laser dyes (gain) into the metamaterial structure results in a frequency band where the nonbianisotropic metamaterial becomes amplifying. In that region both the real and the imaginary part of the effective refractive index become simultaneously negative and the figure of merit diverges at two distinct frequency points.

  3. Low-loss polymer films with adjustable refractive index.

    PubMed

    Ramaswamy, V; Weber, H P

    1973-07-01

    Solution-deposited polymer films with continuously adjustable refractive index (1.489-1.563) are made by blending in solution two polymers: polymethyl methacrylate (PMMA) and styrene-acrylonitrile copolymer (SAN). The dependence of index of refraction on composition was found to be linear, indicating the compatibility of the two polymers on a molecular basis. In films ~2 microm thick losses less than 0.2 dB/cm were measured. For thicker films (3.5 microm) an increased scattering loss was observed in high SAN content films.

  4. Imaging Potential of a Negative Refractive Index Lens

    NASA Astrophysics Data System (ADS)

    Webb, Kevin; Ward, David

    2005-03-01

    Negative refractive index or left-handed (LH) material has been proposed as a perfect lens, whereby evanescent fields in a lossless LH slab would be amplified. Negative permittivity and permeability imply frequency dispersion and, through the Kramers-Kronig relations, loss. Expressing the fields in the object plane by plane wave expansion and assuming some degree of loss in the LH slab, the transfer function of the imaging system for each plane wave component can be obtained. We show that even minute loss has a drastic impact on the support of the plane wave transfer function. This means that for a realistic low-loss LH slab, achieving high resolution implies a near-field restriction, which in turn dictates the slab thickness. An imaging example considers a one-wavelength-thick LH slab, and an incident sub-wavelength transverse magnetic field which is a pulse in space. An approximate image forms in the center of the slab and at the image plane. In addition, the Poynting vector plot of the imaging system shows vortices forming at the surfaces of the LH material as well as at the image plane.

  5. Polymer-based composite with outstanding mechanically tunable refractive index

    NASA Astrophysics Data System (ADS)

    Mohamed-Noriega, Nasser; Hinojosa, Moisés; González, Virgilio; Rodil, Sandra. E.

    2016-08-01

    A composite with high visible light transmittance, mechanically tunable refractive index (RI) and rubber-like mechanical properties, based on poly(dimethylsiloxane) (PDMS) and barium titanate nanoparticles (BT) was prepared on three steps. First, BT nanoparticles were obtained by high-energy milling. Second, the nanoparticles were embedded in PDMS by in-situ polymerization; the BT content was varied up to 1.0 wt% (0.17 vol%). Finally, ∼0.5 mm membranes were prepared by solvent casting. The effect of the BT concentration was examined. Powder XRD and Raman spectroscopy revealed a tetragonal crystal structure for the nanoparticles. SEM images confirmed a mean particle size of ∼64 nm and together with EDX mappings showed a moderate dispersion of the nanoparticles in some membranes, whereas other exhibited agglomerates at the surface. The normal transmittance of the membranes was measured with a spectroscopic ellipsometer while they were stretched in-situ at different percentages. The RI variations as a function of strain were calculated from the transmittance spectra. The results exhibit surprising variations in the RI, up to ∼5 times higher than those associated to PDMS alone, implying that the presence of BT significantly influences the optical response of the PDMS when stretched. However, the response is neither linear nor well understood; further studies must be performed to clarify this new interaction.

  6. 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.

  7. 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.

  8. Refractive index determination in axially symmetric oprtically inhomogeneous media

    NASA Astrophysics Data System (ADS)

    Ionescu-Pallas, Nicholas; Vlad, Valentin I.; Bociort, Florian

    The focussing method from transversally light, put forward by Dietrich Marcuse in view of determining the refractive index profile (RIP) in optical fibers and fiber performs, is revised. A more rigorous derivation of the Marcuse formula is given, establishing the conditions of its validity and a simplified version is initially proposed, able to avoid the systematic errors in the processing of light intensity data.

  9. Nano-imprint gold grating as refractive index sensor

    NASA Astrophysics Data System (ADS)

    Kumari, Sudha; Mohapatra, Saswat; Moirangthem, Rakesh S.

    2016-05-01

    Large scale of fabrication of plasmonic nanostructures has been a challenging task due to time consuming process and requirement of expensive nanofabrication tools such as electron beam lithography system, focused ion beam system, and extreme UV photolithography system. Here, we present a cost-effective fabrication technique so called soft nanoimprinting to fabricate nanostructures on the larger sample area. In our fabrication process, a commercially available optical DVD disc was used as a template which was imprinted on a polymer glass substrate to prepare 1D polymer nano-grating. A homemade nanoimprinting setup was used in this fabrication process. Further, a label-free refractive index sensor was developed by utilizing the properties of surface plasmon resonance (SPR) of a gold coated 1D polymer nano-grating. Refractive index sensing was tested by exposing different solutions of glycerol-water mixture on the surface of gold nano-grating. The calculated bulk refractive index sensitivity was found to be 751nm/RIU. We believed that our proposed SPR sensor could be a promising candidate for developing low-cost refractive index sensor with high sensitivity on a large scale.

  10. X-ray tomographic imaging of the complex refractive index

    NASA Astrophysics Data System (ADS)

    McMahon, P. J.; Peele, A. G.; Paterson, D.; Nugent, K. A.; Snigirev, A.; Weitkamp, T.; Rau, C.

    2003-08-01

    We present a quantitative three-dimensional reconstruction of the complex refractive index of boron clad tungsten fiber using 35 keV x rays. The reconstruction provides a quantitatively accurate measurement with a three-dimensional spatial resolution of approximately 2 μm.

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

    SciTech Connect

    Fu, Yangyang; Xu, Lin; Hong Hang, Zhi; Chen, Huanyang

    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.

  12. Structures with negative index of refraction

    DOEpatents

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

    2011-11-08

    The invention provides simplified negative index materials (NIMs) using wire-pair structures, 4-gap single ring split-ring resonator (SRR), fishnet structures and overleaf capacitor SRR. In the wire-pair arrangement, a pair of short parallel wires and continuous wires are used. In the 4-gap single-ring SRR, the SRRs are centered on the faces of a cubic unit cell combined with a continuous wire type resonator. Combining both elements creates a frequency band where the metamaterial is transparent with simultaneously negative .di-elect cons. and .mu.. In the fishnet structure, a metallic mesh on both sides of the dielectric spacer is used. The overleaf capacitor SRR changes the gap capacities to small plate capacitors by making the sections of the SRR ring overlap at the gaps separated by a thin dielectric film. This technique is applicable to conventional SRR gaps but it best deploys for the 4-gap single-ring structures.

  13. Porous anodic alumina with low refractive index for broadband graded-index antireflection coatings.

    PubMed

    Chen, Junwu; Wang, Biao; Yang, Yi; Shi, Yuanyuan; Xu, Gaojie; Cui, Ping

    2012-10-01

    Materials with very low refractive index are essential to prepare broadband graded-index antireflection (AR) coatings. However, the availability of such materials is very limited. In this study, large-area (4 cm×4 cm) low refractive index porous anodic alumina (PAA) coatings on glass substrate were prepared successfully by electron-beam evaporation, electrochemical oxidation, and chemical etching method. The nanopore size of PAA film is smaller than 40 nm, and the refractive index of PAA film is n=1.08. Besides, five-layered graded-index broadband PAA coatings with refractive indices following the Gaussian profile were also prepared to noticeably eliminate the reflectance of glass over a broadband wavelength, and the lowest reflectivity is 0.64% at the wavelength of 534 nm at normal incidence. The PAA AR coatings having an omnidirectional nature are likely to have practical applications in photovoltaic cells and optical devices.

  14. Refractive index and birefringence of 2H silicon carbide

    NASA Technical Reports Server (NTRS)

    Powell, J. A.

    1972-01-01

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

  15. Temperature-dependent Refractive Index of Silicon and Germanium

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    Silicon and germanium are perhaps the two most well-understood semiconductor materials in the context of solid state device technologies and more recently micromachining and nanotechnology. Meanwhile, these two materials are also important in the field of infrared lens design. Optical instruments designed for the wavelength range where these two materials are transmissive achieve best performance when cooled to cryogenic temperatures to enhance signal from the scene over instrument background radiation. In order to enable high quality lens designs using silicon and germanium at cryogenic temperatures, we have measured the absolute refractive index of multiple prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For silicon, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 1.1 to 5.6 pin, while for germanium, we cover temperatures ranging from 20 to 300 K and wavelengths from 1.9 to 5.5 microns. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. Citing the wide variety of values for the refractive indices of these two materials found in the literature, we reiterate the importance of measuring the refractive index of a sample from the same batch of raw material from which final optical components are cut when absolute accuracy greater than k5 x 10" is desired.

  16. Fabrication of Tunable, High-Refractive-Index Titanate-Silk Nanocomposites on the Micro- and Nanoscale.

    PubMed

    Perotto, Giovanni; Cittadini, Michela; Tao, Hu; Kim, Sunghwan; Yang, Miaomiao; Kaplan, David L; Martucci, Alessandro; Omenetto, Fiorenzo G

    2015-11-01

    The combination of water-based titanate nanosheets dispersion and silk fibroin solution allows the realization of a versatile nanocomposite. Different fabrication techniques can be easily applied on these nanocomposites to manipulate the end form of these materials on the micro- and nanoscale. Easy tunability of the refractive index from n = 1.55 up to n = 1.97 is achieved, making it attractive for flexible, biopolymer-based optical devices. PMID:26414278

  17. Microwave Focusing Using Negative Index of Refraction Materials

    NASA Astrophysics Data System (ADS)

    Brock, Jeffrey; Houck, Andrew; Chuang, Isaac

    2003-03-01

    We present experimental results testing the theoretical prediction that a flat slab of negative index material can act as a perfect lens, focusing propagating waves. Our data gives two-dimensional profiles of the electromagnetic field transmitted from a 10 GHz point source in a 2D waveguide through composite wire and split-ring resonator rectangular prisms. Prior experiments show that these structures have a negative index of refraction in a narrow frequency regime. We measure transmission through prisms of various thicknesses in both the negative index and positive index regimes, and observe a spatial concentration of power when the material has a negative index that is absent in the positive index measurements.

  18. Modelling refractive index changes due to molecular interactions

    NASA Astrophysics Data System (ADS)

    Varma, Manoj

    2016-03-01

    There are a large number of sensing techniques which use optical changes to monitor interactions between molecules. In the absence of fluorophores or other labels, the basic signal transduction mechanism relies on refractive index changes arising from the interactions of the molecules involved. A quantitative model incorporating molecular transport, reaction kinetics and optical mixing is presented which reveals important insights concerning the optimal detection of molecular interactions optically. Although conceptually simple, a comprehensive model such as this has not been reported anywhere. Specifically, we investigate the pros and cons of detecting molecular interactions in free solution relative to detecting molecular interactions on surfaces using surface bound receptor molecules such as antibodies. The model reveals that the refractive index change produced in surface based sensors is 2-3 orders of magnitude higher than that from interactions in free solution. On the other hand, the model also reveals that it is indeed possible to distinguish specific molecular interactions from non-specific ones based on free-solution bulk refractometry without any washing step necessary in surface based sensors. However, the refractive index change for free solution interactions predicted by the model is smaller than 10-7 RIU, even for large proteins such as IgG in sufficiently high concentrations. This value is smaller than the typical 10-6 RIU detection limit of most state of the art optical sensing techniques therefore requiring techniques with substantially higher index sensitivity such as Back Scattering Interferometry.

  19. 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.

  20. Analytical modelling of a refractive index sensor based on an intrinsic micro Fabry-Perot interferometer.

    PubMed

    Vargas-Rodriguez, Everardo; Guzman-Chavez, Ana D; Cano-Contreras, Martin; Gallegos-Arellano, Eloisa; Jauregui-Vazquez, Daniel; Hernández-García, Juan C; Estudillo-Ayala, Julian M; Rojas-Laguna, Roberto

    2015-10-15

    In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10(-4) RIU can be implemented by using a couple of standard and low cost photodetectors.

  1. Analytical Modelling of a Refractive Index Sensor Based on an Intrinsic Micro Fabry-Perot Interferometer

    PubMed Central

    Vargas-Rodriguez, Everardo; Guzman-Chavez, Ana D.; Cano-Contreras, Martin; Gallegos-Arellano, Eloisa; Jauregui-Vazquez, Daniel; Hernández-García, Juan C.; Estudillo-Ayala, Julian M.; Rojas-Laguna, Roberto

    2015-01-01

    In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10−4 RIU can be implemented by using a couple of standard and low cost photodetectors. PMID:26501277

  2. Analytical modelling of a refractive index sensor based on an intrinsic micro Fabry-Perot interferometer.

    PubMed

    Vargas-Rodriguez, Everardo; Guzman-Chavez, Ana D; Cano-Contreras, Martin; Gallegos-Arellano, Eloisa; Jauregui-Vazquez, Daniel; Hernández-García, Juan C; Estudillo-Ayala, Julian M; Rojas-Laguna, Roberto

    2015-01-01

    In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10(-4) RIU can be implemented by using a couple of standard and low cost photodetectors. PMID:26501277

  3. 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

  4. INDEX OF REFRACTION OF SHOCK LOADED SODA-LIME GLASS

    SciTech Connect

    Alexander, C. S.

    2009-12-28

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

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

    PubMed

    Lazar, Josef; Holá, Miroslava; Číp, Ondřej; Čížek, Martin; Hrabina, Jan; Buchta, Zdeněk

    2012-10-19

    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.

  6. Perfect conformal invisible device with feasible refractive indexes

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Chen, Huanyang; Tyc, Tomáš; Xie, Yangbo; Cummer, Steven A.

    2016-01-01

    Optical conformal mapping has been used to construct several isotropic devices with novel functionalities. In particular, a conformal cloak could confer omnidirectional invisibility. However, the maximum values of the refractive indexes needed for current designs are too large to implement, even in microwave experiments. Furthermore, most devices designed so far have had imperfect impedance matching and therefore incomplete invisibility functionalities. Here we describe a perfect conformal invisible device with full impedance matching everywhere. The maximum value of refractive index required by our device is just about five, which is feasible for microwave and terahertz experiments using current metamaterial techniques. To construct the device, we use a logarithmic conformal mapping and a Mikaelian lens. Our results should enable a conformal invisible device with almost perfect invisibility to be made soon.

  7. Fiber probe microcavities for refractive index and temperature discrimination

    NASA Astrophysics Data System (ADS)

    André, Ricardo M.; Warren-Smith, Stephen C.; Becker, Martin; Dellith, Jan; Rothhardt, Manfred; Zibaii, M. I.; Latifi, H.; Marques, Manuel B.; Bartelt, Hartmut; Frazão, Orlando

    2016-05-01

    Fiber probe structures composed of two physical microcavities were created using focused ion beam technology. These structures have a tip-like shape as they were milled in preciously etched tapered fiber tips. The microprobes are then characterized for temperature and refractive index sensing using a signal filtering technique to discriminate signals from distinct microcavities. Using fast Fourier transforms combined with band-pass filters, it is possible to reconstruct the spectra of each cavity independently and thus measure their individual spectral shifts.

  8. Fiber Optic-Based Refractive Index Sensing at INESC Porto

    PubMed Central

    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

  9. Energy gap refractive index relations in semiconductors An overview

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

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

  10. 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 Δn ~ −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

  11. Ultrafast refractive index control of a terahertz graphene metamaterial.

    PubMed

    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 Δn ~ -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. 3D refractive index measurements of special optical fibers

    NASA Astrophysics Data System (ADS)

    Yan, Cheng; Huang, Su-Juan; Miao, Zhuang; Chang, Zheng; Zeng, Jun-Zhang; Wang, Ting-Yun

    2016-09-01

    A digital holographic microscopic chromatography-based approach with considerably improved accuracy, simplified configuration and performance stability is proposed to measure three dimensional refractive index of special optical fibers. Based on the approach, a measurement system is established incorporating a modified Mach-Zehnder interferometer and lab-developed supporting software for data processing. In the system, a phase projection distribution of an optical fiber is utilized to obtain an optimal digital hologram recorded by a CCD, and then an angular spectrum theory-based algorithm is adopted to extract the phase distribution information of an object wave. The rotation of the optic fiber enables the experimental measurements of multi-angle phase information. Based on the filtered back projection algorithm, a 3D refraction index of the optical fiber is thus obtained at high accuracy. To evaluate the proposed approach, both PANDA fibers and special elliptical optical fiber are considered in the system. The results measured in PANDA fibers agree well with those measured using S14 Refractive Index Profiler, which is, however, not suitable for measuring the property of a special elliptical fiber.

  13. Microvolume index of refraction determinations by interferometric backscatter

    NASA Astrophysics Data System (ADS)

    Bornhop, Darryl J.

    1995-06-01

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

  14. Evanescent field sensing: cavity-coupled refractive index sensor (CRIS)

    NASA Astrophysics Data System (ADS)

    Lindvold, Lars R.; Lading, Lars

    1998-03-01

    A new concept for the detection of very small changes in the refractive index of a small sample of transparent material is given. The concept is based on measuring the frequency difference between two modes of a laser (possibly a twin- laser), where the evanescent field of one mode is affected by small refractive index changes. Intracavity sensing allows for orders of magnitude greater sensitivity than with external sensing. The frequency difference is obtained by light beating of the two modes. An imbedded diffractive element ensures proper modematching for the light beating. The relative frequency change is equal to the relative change in refractive index properly averaged over the waveguide. The performance of the intracavity system is compared with a system based on a Mach-Zehnder interferometer. The intracavity system may achieve a resolution that is 104 - 106 higher than the sensitivity of a system based on an external interferometer. The effect of thermal instability is investigated and it is discussed how the required very low thermal off-set can be maintained. Injection locking can be a problem. The problem may be solved by either introducing a fixed frequency off- set or by proper design of the cavity structure. An implementation based on III-V materials with a waveguide configuration and Bragg-mirrors is possible with existing technologies. A concept based on a polymer configuration is proposed.

  15. Origami with negative refractive index to generate super-lenses

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  16. Determining index of refraction from polarimetric hyperspectral radiance measurements

    NASA Astrophysics Data System (ADS)

    Martin, Jacob A.; Gross, Kevin C.

    2015-09-01

    Polarimetric hyperspectral imaging (P-HSI) combines two of the most common remote sensing modalities. This work leverages the combination of these techniques to improve material classification. Classifying and identifying materials requires parameters which are invariant to changing viewing conditions, and most often a material's reflectivity or emissivity is used. Measuring these most often requires assumptions be made about the material and atmospheric conditions. Combining both polarimetric and hyperspectral imaging, we propose a method to remotely estimate the index of refraction of a material. In general, this is an underdetermined problem because both the real and imaginary components of index of refraction are unknown at every spectral point. By modeling the spectral variation of the index of refraction using a few parameters, however, the problem can be made overdetermined. A number of different functions can be used to describe this spectral variation, and some are discussed here. Reducing the number of spectral parameters to fit allows us to add parameters which estimate atmospheric downwelling radiance and transmittance. Additionally, the object temperature is added as a fit parameter. The set of these parameters that best replicate the measured data is then found using a bounded Nelder-Mead simplex search algorithm. Other search algorithms are also examined and discussed. Results show that this technique has promise but also some limitations, which are the subject of ongoing work.

  17. Turbulent nature of refractive-index variations in biological tissue

    NASA Astrophysics Data System (ADS)

    Schmitt, J. M.; Kumar, G.

    1996-08-01

    Phase-contrast microscopy shows that the structure of the refractive-index inhomogeneities in a variety of mammalian tissues resembles that of frozen turbulence. Viewed over a range of scales, the spectrum of index variations exhibits a power-law behavior for spatial frequencies spanning at least a decade (5-50 mu m-1 ) and has an outer scale in the range of 4-10 mu m , above which correlations are no longer seen. The observed structure function fits the classical Kolmogorov model of turbulence. These observations are fundamental to understanding light propagation in tissue and may provide clues about how tissues develop and organize.

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

    SciTech Connect

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

    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)

  19. Lattice and electronic contributions to the refractive index of CuWO₄

    SciTech Connect

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

    2014-09-14

    We report an investigation of the refractive index dispersion and anisotropy in CuWO₄ by means of interference measurements in two extinction directions from mid infrared to the visible region of the energy spectrum. The analysis of the refractive index dispersion yields ϵ(∞)=4.5(1) for light polarization parallel to the c-axis and ϵ(∞)=5.3(1) with respect to the other extinction axis. In addition, we report reflectance measurements carried out from the far infrared to the near ultraviolet to study the lattice and electronic contributions to the refractive index of CuWO₄. We have determined the wavenumbers of nine infrared active lattice modes and compared them with previous ab initio calculations. The value of the Penn gap, 7eV, as well as the origin of a structure observed at 4.4 eV in the reflectance spectrum, is discussed in the context of the CuWO₄ electronic structure.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    A nanolayered polymer films approach to designing and fabricating gradient refractive index (GRIN) lenses with designer refractive index distribution profiles and an independently prescribed lens surface geometry have been demonstrated to produce a new class of optics. This approach utilized nanolayered polymer materials, constructed with polymethylmethacrylate and a styrene-co-acrylonitrile copolymer with a tailorable refractive index intermediate to bulk materials, to fabricate discrete GRIN profile materials. A process to fabricate nanolayered polymer GRIN optics from these materials through thermoforming and finishing steps is reviewed. A collection of technology-demonstrating previously reported nanolayered GRIN case studies is presented that include: (1) the optical performance of a f/# 2.25 spherical GRIN plano-convex singlet with one quarter (2) the weight of a similar BK7 lens and a bio-inspired aspheric human eye GRIN lens. Original research on the fabrication and characterization of a Luneburg inspired GRIN ball lens is presented as a developing application of the nanolayered polymer technology.

  1. Foldable antibacterial acrylic intraocular lenses of high refractive index.

    PubMed

    Parra, F; Vázquez, B; Benito, L; Barcenilla, J; San Román, J

    2009-11-01

    Hydrophilic copolymers with high refractive index and bactericide properties based on quaternary ammonium salts monomers and methacrylates bearing benzothiazole moieties have been developed for application as foldable intraocular lenses. Composition of the systems was adjusted to get materials with optimized flexibility, wettability, and refractive properties. All the materials have been characterized in terms of optical properties, glass transition temperature, water content, and wettability. Water contact values oscillated between 37 and 15% and refractive index values in the wet state between 1.49 and 1.53, depending on composition. Glass transition temperature interval was 63-77 degrees C. Values of surface free energy of the solid ranged from 49 to 54 mN/m, characteristic of IOL hydrogel materials. Bactericide properties of the quaternary ammonium salts methacrylates were higher than that of the benzothiazole derivative, showing inhibition halos as high as 23-25 mm in antibiogram tests against S. epidermidis and P. aeruginosa , strains found in the ocular cavity and responsible for most postsurgical endolphthalmitis. Biocompatibility of the systems was evaluated in cell cultures using human fibroblasts. Cellular viability was higher than 90%, and close to 100% in many cases, for the extracts of selected formulations collected at different periods of time. PMID:19795830

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

    SciTech Connect

    Qiao, Hong; 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.

  3. Index of Refraction and Absorption Coefficient Spectra of Paratellurite in the Terahertz Region

    NASA Astrophysics Data System (ADS)

    Unferdorben, Márta; Buzády, Andrea; Hebling, János; Kiss, Krisztián; Hajdara, Ivett; Kovács, László; Péter, Ágnes; Pálfalvi, László

    2016-07-01

    Index of refraction and absorption coefficient spectra of pure paratellurite (α-TeO2) crystal as a potential material for terahertz (THz) applications were determined in the 0.25-2 THz frequency range at room temperature by THz time domain spectroscopy (THz-TDS). The investigation was performed with beam polarization both parallel (extraordinary polarization) and perpendicular (ordinary polarization) to the optical axis [001] of the crystal. Similarly to the visible spectral range, positive birefringence was observed in the THz range as well. It was shown that the values of the refractive index for extraordinary polarization are higher and show significantly larger dispersion than for the ordinary one. The absorption coefficient values are also larger for extraordinary polarization. The measured values were fitted by theoretical curves derived from the complex dielectric function containing independent terms of Lorentz oscillators due to phonon-polariton resonances. The results are compared with earlier publications, and the observed significant discrepancies are discussed.

  4. 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.

  5. CO2 laser induced refractive index changes in optical polymers.

    PubMed

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

    2012-01-01

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

  6. Wavelength dependence of refractive index in lead-free Na0.5Bi0.5TiO3-BaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    He, Chongjun; Yi, Xiujie; Wu, Tong; Wang, Jiming; Zhu, Kongjun; Liu, Youwen

    2014-10-01

    Refractive indices of (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (NBT-xBT, x = 0, 0.06 and 0.08) single crystals were measured at room temperature after poled along pseudo-cubic crystallographic direction [0 0 1]. The refractive indices decrease dramatically when the wavelength increases for all crystals. At the same wavelength, refractive indices of NBT-xBT single crystals decrease with increasing BT content. Sellmeier dispersion equations were obtained by least square fitting, which can be used to calculate the refractive indices in low absorption wavelength range. Parameters connected to the energy band structure were determined by fitting single-oscillator dispersion equation. Similar to most oxygen-octahedral ferroelectrics, NBT-xBT crystals have the same dispersion behavior described by the refractive-index dispersion parameter. Dispersion energies take on covalent crystal values.

  7. Cryogenic Refractive Index and Coefficient of Thermal Expansion for the S-TIH1 Glass

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    Using the CHARMS facility at NASA GSFC, we have measured the cryogenic refractive index of the Ohara S-TIH1 glass from 0.40 to 2.53 micrometers and from 120 to 300 K. We have also examined the spectral dispersion and thermo-optic coefficients (dn/dT). We also derived temperature-dependent Sellmeier models from which refractive index may be calculated for any wavelength and temperature within the stated ranges of each model. The S-TIH1 glass we tested exhibited unusual behavior in the thermo-optic coefficient. We found that for delta < 0.5 micrometers, the index of refraction decrease with a decrease in temperature (positive dn/dT). However, the situation was reversed for delta larger than 0.63 micrometers, where the index will increase with a decrease in temperature (negative dn/dT). We also measured the coefficient of thermal expansion (CTE) for the similar batch of S-TIH1 glass in order to understand its thermal properties. The CTE showed a monotonic change with a decrease in temperature.

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

    PubMed

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

    2015-02-15

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

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

    PubMed

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

    2011-05-29

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

  10. Refractive index change detection based on porous silicon microarray

    NASA Astrophysics Data System (ADS)

    Chen, Weirong; Jia, Zhenhong; Li, Peng; Lv, Guodong; Lv, Xiaoyi

    2016-05-01

    By combining photolithography with the electrochemical anodization method, a microarray device of porous silicon (PS) photonic crystal was fabricated on the crystalline silicon substrate. The optical properties of the microarray were analyzed with the transfer matrix method. The relationship between refractive index and reflectivity of each array element of the microarray at 633 nm was also studied, and the array surface reflectivity changes were observed through digital imaging. By means of the reflectivity measurement method, reflectivity changes below 10-3 can be observed based on PS microarray. The results of this study can be applied to the detection of biosensor arrays.

  11. 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

  12. Compensation for refractive-index variations in laser Doppler anemometry.

    PubMed

    Kehoe, A B; Desai, P V

    1987-07-01

    Techniques to compensate for index of refraction variations in the application of a laser Doppler anemometer are examined. For discontinuous plane-layered media a method of discrete elements is employed. An alternative set of equations is derived for continuous cylindrically layered media and simplified to make comparisons with available results for a single cylinder. Results of velocity measurements in a Plexiglas model of a cylindrically layered nuclear fuel assembly are presented to establish a positioning accuracy of the method to within 0.025 cm. PMID:20489924

  13. Compensation for refractive-index variations in laser Doppler anemometry.

    PubMed

    Kehoe, A B; Desai, P V

    1987-07-01

    Techniques to compensate for index of refraction variations in the application of a laser Doppler anemometer are examined. For discontinuous plane-layered media a method of discrete elements is employed. An alternative set of equations is derived for continuous cylindrically layered media and simplified to make comparisons with available results for a single cylinder. Results of velocity measurements in a Plexiglas model of a cylindrically layered nuclear fuel assembly are presented to establish a positioning accuracy of the method to within 0.025 cm.

  14. Double cavity refractive index photonic crystal sensor temperature calibrated

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  15. Refractive index of erbium doped GaN thin films

    SciTech Connect

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

    2014-08-25

    GaN is an excellent host for erbium (Er) to provide optical emission in the technologically important as well as eye-safe 1540 nm wavelength window. Er doped GaN (GaN:Er) epilayers were synthesized on c-plane sapphire substrates using metal organic chemical vapor deposition. By employing a pulsed growth scheme, the crystalline quality of GaN:Er epilayers was significantly improved over those obtained by conventional growth method of continuous flow of reaction precursors. X-ray diffraction rocking curve linewidths of less than 300 arc sec were achieved for the GaN (0002) diffraction peak, which is comparable to the typical results of undoped high quality GaN epilayers and represents a major improvement over previously reported results for GaN:Er. Spectroscopic ellipsometry was used to determine the refractive index of the GaN:Er epilayers in the 1540 nm wavelength window and a linear dependence on Er concentration was found. The observed refractive index increase with Er incorporation and the improved crystalline quality of the GaN:Er epilayers indicate that low loss GaN:Er optical waveguiding structures are feasible.

  16. Variation of refractive index in strained In(x)Ga(1-x)As-GaAs heterostructures

    NASA Technical Reports Server (NTRS)

    Das, U.; Bhattacharya, P. K.

    1986-01-01

    In(x)Ga(1-x)As-GaAs heterostructures and strained-layer superlattices can be used as optical waveguides. For such applications it is important to know explicitly the refractive index variation with mismatch strain and with alloying in the ternary layer. Starting from the Kramers-Kronig integral dispersion relations, a model has been developed from which the refractive index change in the ternary layer of In(x)Ga(1-x)As-GaAs heterojunctions can be calculated. The results are presented and discussed. The expected changes in a superlattice have been qualitatively predicted.

  17. Superlensing effect for surface acoustic waves in a pillar-based phononic crystal with negative refractive index

    SciTech Connect

    Addouche, Mahmoud Al-Lethawe, Mohammed A. Choujaa, Abdelkrim Khelif, Abdelkrim

    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 (λ)/3 , overcoming the Rayleigh diffraction limit.

  18. Terahertz metasurfaces with a high refractive index enhanced by the strong nearest neighbor coupling.

    PubMed

    Tan, Siyu; Yan, Fengping; Singh, Leena; Cao, Wei; Xu, Ningning; Hu, Xiang; Singh, Ranjan; Wang, Mingwei; Zhang, Weili

    2015-11-01

    The realization of high refractive index is of significant interest in optical imaging with enhanced resolution. Strongly coupled subwavelength resonators were proposed and demonstrated at both optical and terahertz frequencies to enhance the refractive index due to large induced dipole moment in meta-atoms. Here, we report an alternative design for flexible free-standing terahertz metasurface in the strong coupling regime where we experimentally achieve a peak refractive index value of 14.36. We also investigate the impact of the nearest neighbor coupling in the form of frequency tuning and enhancement of the peak refractive index. We provide an analytical circuit model to explain the impact of geometrical parameters and coupling on the effective refractive index of the metasurface. The proposed meta-atom structure enables tailoring of the peak refractive index based on nearest neighbor coupling and this property offers tremendous design flexibility for transformation optics and other index-gradient devices at terahertz frequencies.

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

    PubMed

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

    2014-05-19

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

  20. Refractive index of air: new equations for the visible and near infrared.

    PubMed

    Ciddor, P E

    1996-03-20

    The precision of modern length interferometry and geodetic surveying far exceeds the accuracy, which is ultimately limited by the inadequacy of currently used equations for the refractive index of the atmosphere. I have critically reviewed recent research at the National Physical Laboratory, the International Bureau of Weights and Measures, and elsewhere that has led to revised formulas and data for the dispersion and density of the major components of the atmosphere. I have combined selected formulas from these sources to yield a set of equations that match recently reported measurements to within the experimental error, and that are expected to be reliable over very wide ranges of atmospheric parameters and wavelength.

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

    PubMed Central

    Li, Xiangping; Zhang, Qiming; Chen, Xi; Gu, Min

    2013-01-01

    Graphene oxides (GOs) have emerged as precursors offering the potential of a cost-effective and large-scale production of graphene-based materials. Despite that their intrinsic fluorescence property has already brought interest of researchers for optical applications, to date, refractive-index modulation as one of the fundamental aspects of optical properties of GOs has received less attention. Here we reported on a giant refractive-index modulation on the order of 10−2 to 10−1, accompanied by a fluorescence intensity change, through the two-photon reduction of GOs. These features enabled a mechanism for multimode optical recording with the fluorescence contrast and the hologram-encoded refractive-index modulation in GO-dispersed polymers for security-enhanced high-capacity information technologies. Our results show that GO-polymer composites may provide a new material platform enabling flexible micro-/nano-photonic information devices. PMID:24085266

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

    van der Horst, Astrid

    2006-09-01

    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.

  4. Gradient Refractive Index Optics IOL: Theoretical Background and Clinical Results

    PubMed Central

    Malyugin, Boris; Morozova, Tatiana; Cherednik, Valentin

    2014-01-01

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

  5. Optical Enhancement in Optoelectronic Devices Using Refractive Index Grading Layers.

    PubMed

    Lee, Illhwan; Park, Jae Yong; Gim, Seungo; Kim, Kisoo; Cho, Sang-Hwan; Choi, Chung Sock; Song, Seung-Yong; Lee, Jong-Lam

    2016-02-10

    We enhanced the optical transmittance of a multilayer barrier film by inserting a refractive index grading layer (RIGL). The result indicates that the Fresnel reflection, induced by the difference of refractive indices between Si(x)N(y) and SiO2, is reduced by the RIGL. To eliminate the Fresnel reflection while maintaining high transmittance, the optimized design of grading structures with the RIGL was conducted using an optical simulator. With the RIGL, we achieved averaged transmittance in the visible wavelength region by 89.6%. It is found that the optimized grading structure inserting the multilayer barrier film has a higher optical transmittance (89.6%) in the visible region than that of a no grading sample (82.6%). Furthermore, luminance is enhanced by 14.5% (from 10,190 to 11,670 cd m(-2) at 30 mA cm(-2)) when the grading structure is applied to organic light-emitting diodes. Finally, the results offer new opportunities in development of multilayer barrier films, which assist industrialization of very cost-effective flexible organic electronic devices.

  6. Refractive-index measurement and inverse correction using optical coherence tomography.

    PubMed

    Stritzel, Jenny; Rahlves, Maik; Roth, Bernhard

    2015-12-01

    We describe a novel technique for determination of the refractive index of hard biological tissue as well as nonopaque technical samples based on optical coherence tomography (OCT). Our method relies on an inverse refractive-index correction (I-RIC), which matches a measured feature geometry distorted due to refractive-index boundaries to its real geometry. For known feature geometry, the refractive index can be determined with high precision from the best match between the distorted and corrected images. We provide experimental data for refractive-index measurements on a polymethylmethacrylate (PMMA) and on an ex vivo porcine cranial-bone, which are compared to reference measurements and previously published data. Our method is potentially capable of in vivo measurements on rigid biological tissue such as bone as, for example, is required to improve guidance in robot-aided surgical interventions and also for retrieving complex refractive-index profiles of compound materials.

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

    SciTech Connect

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

    2011-07-01

    The relationship between refractive index and nanoparticle radii of cadmium selenide (CdSe) nanoparticles embedded within glass matrixes was investigated experimentally and by simulations. A homemade automated Michelson interferometer arrangement employing a rotating table and a He-Ne laser source at a wavelength of 632.8 nm determined the refractive index versus nanoparticle radii of embedded cadmium selenide (CdSe) nanoparticles. The refractive index was found to decrease linearly with nanoparticle radius increase. However, one sample showed a step increase in refractive index; on spectroscopic analysis, it was found that its resonant wavelength matched that of the He-Ne source wavelength. The simulations showed that two conditions caused the step increase in refractive index: low plasma frequency and matched sample and source resonances. This simple interferometer setup defines a new method of determining the radii of nanoparticles embedded in substrates and enables refractive index tailoring by modification of exact annealing conditions.

  8. Anomalous behavior of group velocity and index of refraction in a defect photonic band gap structure

    NASA Astrophysics Data System (ADS)

    Srivastava, Sanjeev K.; Pandey, G. N.; Ojha, S. P.

    2008-02-01

    In the present paper, we have made an analysis to observe the effect of introduction of defect on dispersion relation, group velocity, and effective group index in a conventional photonic band gap (PBG) structure. The study shows that inside the PBG materials group velocity and effective group index becomes negative in both types (conventional as well as defect PBG structure) of structure at a certain range of frequencies. Also, near the edges of the bands it attains very high values of index of refraction. A defect PBG structure gives a very unique feature that group velocity becomes exactly zero at a particular value of frequency and also becomes several hundred times greater than the velocity of light which is not attainable with the conventional PBG structure. Defect PBG structures with such peculiar characteristics are seen in lasing without inversion, in construction of perfect lens, in trapping of photon and other optical devices.

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

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

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

  10. Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity

    NASA Astrophysics Data System (ADS)

    Borrero-Echeverry, D.; Morrison, B. C. A.

    2016-07-01

    We show that aqueous solutions of ammonium thiocyanate ({NH}4{SCN}) can be used to match the index of refraction of several transparent materials commonly used in experiments, while maintaining low viscosity and density compared to other common refractive index-matching liquids. We present empirical models for estimating the index of refraction, density, and kinematic viscosity of these solutions as a function of temperature and concentration. Finally, we summarize the chemical compatibility of ammonium thiocyanate with materials commonly used in apparatus.

  11. Enhancing the sensitivity of liquid refractive index sensor based on slow light photonic crystal waveguide

    NASA Astrophysics Data System (ADS)

    Zhao, Yong; Huang, He; Wang, Qi

    2011-05-01

    This paper designed a high sensitivity refractive index sensor based on two-dimensional square-lattice slow light photonic crystal waveguide. This structure based on Mach-Zehnder interferometer (MZI) which can be widely used in measuring the refractive index of liquid. The resolution of this sample structure can reach 7×10-7 RIU. This kind of sensor can be integrated with electronic systems to measure the refractive index of gas or fluid.

  12. Semiconductor laser devices having lateral refractive index tailoring

    DOEpatents

    Ashby, Carol I. H.; Hadley, G. Ronald; Hohimer, John P.; Owyoung, Adelbert

    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.

  13. Loop-mirror-based slot waveguide refractive index sensor

    NASA Astrophysics Data System (ADS)

    Kou, Jun-long; Xu, Fei; Lu, Yan-qing

    2012-12-01

    Loop mirror has been widely used in fiber optical devices and systems for it provides a smart way to make use of the fiber birefringence properties and can enhance the sensitivity greatly. On the other hand, slot waveguide is very promising for optical sensing applications because of their peculiar spatial mode profile. In this paper, we propose and analyze a loop-mirror-based slot waveguide (LMSW) sensor which can be routinely fabricated in modern high-volume complementary metal-oxide-semiconductor (CMOS) process. The finite element method (FEM) simulation results show that the birefringence can be as high as 0.8 which is orders of magnitude than that in conventional birefringent fiber loop mirror. High sensitivity up to 6 × 103 nm/RIU (refractive index unit) is achieved by this scheme.

  14. Group refractive index reconstruction with broadband interferometric confocal microscopy

    PubMed Central

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

    2010-01-01

    We propose a novel method of measuring the group refractive index of biological tissues at the micrometer scale. The technique utilizes a broadband confocal microscope embedded into a Mach–Zehnder interferometer, with which spectral interferograms are measured as the sample is translated through the focus of the beam. The method does not require phase unwrapping and is insensitive to vibrations in the sample and reference arms. High measurement stability is achieved because a single spectral interferogram contains all the information necessary to compute the optical path delay of the beam transmitted through the sample. Included are a physical framework defining the forward problem, linear solutions to the inverse problem, and simulated images of biologically relevant phantoms. PMID:18451922

  15. Spatially varying index of refraction: An open ended undergraduate topic

    SciTech Connect

    Krueger, D.A.

    1980-03-01

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

  16. Controlling a microdisk laser by local refractive index perturbation

    NASA Astrophysics Data System (ADS)

    Liew, Seng Fatt; Ge, Li; Redding, Brandon; Solomon, Glenn S.; Cao, Hui

    2016-02-01

    We demonstrate a simple yet effective approach of controlling lasing in a semiconductor microdisk by photo-thermal effect. A continuous wave green laser beam, focused onto the microdisk perimeter, can enhance or suppress lasing in different cavity modes, depending on the position of the focused beam. Its main effect is a local modification of the refractive index of the disk, which results in an increase in the power slope of some lasing modes and a decrease of others. The boundary roughness breaks the rotational symmetry of a circular disk, allowing the lasing process to be tuned by varying the green beam position. Using the same approach, we can also fine tune the relative intensity of a quasi-degenerate pair of lasing modes. Such post-fabrication control, enabled by an additional laser beam, is flexible and reversible, thus enhancing the functionality of semiconductor microdisk lasers.

  17. Imprinting the nanostructures on the high refractive index semiconductor glass

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  18. Full field imaging based instantaneous hyperspectral absolute refractive index measurement

    SciTech Connect

    Baba, Justin S; Boudreaux, Philip R

    2012-01-01

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

  19. Laser-induced refractive index changes in nanocrystalline diamond membranes.

    PubMed

    Preclíková, Jana; Kromka, Alexander; Rezek, Bohuslav; Malý, Petr

    2010-02-15

    We have observed what we believe to be a new phenomenon in nanocrystalline diamond membranes. The optical thickness of the membrane is changed under laser irradiation, which leads to a spectral shift of interference fringes in the transmission and photoluminescence spectra of high-quality thin self-supporting nanocrystalline membranes. The direction of the spectral shift (red/blue) can be tuned by the ambient air pressure. The effect is reversible and is accompanied by changes in photoluminescence intensity. We interpret the results in terms of the changes in the index of refraction caused by the photoinduced adsorption/desorption of air molecules that subsequently affect the properties of subgap energy states related to the surface and the grain boundaries of the nanocrystals.

  20. Refractive index measurement of nanoparticles by immersion refractometry based on a surface plasmon resonance sensor

    NASA Astrophysics Data System (ADS)

    Kano, Hiroshi; Iseda, Ayumu; Ohenoja, Katja; Niskanen, Ilpo

    2016-06-01

    Accurate determination of the refractive index of nanoparticles has important ramifications for applications, such as pharmaceuticals, cosmetics, paints, textiles, and inks. We describe a new method to determine the refractive index of nanoparticles by immersion refractometry with a surface plasmon resonance sensor. With this method, the refractive index of the nanoparticles is perfectly matched with that of the surrounding liquid. We demonstrate this method for calcium fluoride nanoparticles that have an average diameter of 100 nm; the results achieve an accuracy of better than 0.002 refractive index units.

  1. On-chip integrated optofluidic complex refractive index sensing using silicon photonic crystal nanobeam cavities.

    PubMed

    Zhang, Xingwang; Zhou, Guangya; Shi, Peng; Du, Han; Lin, Tong; Teng, Jinghua; Chau, Fook Siong

    2016-03-15

    Complex refractive index sensing is proposed and experimentally demonstrated in optofluidic sensors based on silicon photonic crystal nanobeam cavities. The sensitivities are 58 and 139 nm/RIU, respectively, for the real part (n) and the imaginary part (κ) of the complex refractive index, and the corresponding detection limits are 1.8×10(-5) RIU for n and 4.1×10(-6) RIU for κ. Moreover, the capability of the complex refractive index sensing method to detect the concentration composition of the ternary mixture is demonstrated without the surface immobilization of functional groups, which is impossible to realize with the conventional refractive index sensing scheme.

  2. 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.

  3. Coexistence of positive and negative refractive index sensitivity in the liquid-core photonic crystal fiber based plasmonic sensor.

    PubMed

    Shuai, Binbin; Xia, Li; Liu, Deming

    2012-11-01

    We present and numerically characterize a liquid-core photonic crystal fiber based plasmonic sensor. The coupling properties and sensing performance are investigated by the finite element method. It is found that not only the plasmonic mode dispersion relation but also the fundamental mode dispersion relation is rather sensitive to the analyte refractive index (RI). The positive and negative RI sensitivity coexist in the proposed design. It features a positive RI sensitivity when the increment of the SPP mode effective index is larger than that of the fundamental mode, but the sensor shows a negative RI sensitivity once the increment of the fundamental mode gets larger. A maximum negative RI sensitivity of -5500nm/RIU (Refractive Index Unit) is achieved in the sensing range of 1.50-1.53. The effects of the structural parameters on the plasmonic excitations are also studied, with a view of tuning and optimizing the resonant spectrum. PMID:23187403

  4. Widely tunable and ultrasensitive leaky-guided multimode fiber interferometer based on refractive-index-matched coupling.

    PubMed

    Lee, Cheng-Ling; Lin, Kuo-Hsiang; Lin, Yuanyao; Hsu, Jui-Ming

    2012-02-01

    This investigation presents a simple, widely tunable, and ultrasensitive sensor that is based on a leaky-guided multimode fiber interferometer (MMFI) operated under refractive-index-matched coupling. By use of a material with an appropriate dispersion profile around the MMFI as a cladding yields strong index-matched coupling, which performs ultrasensitive sensing in variations of the surroundings. Index matching at a single wavelength yields a coupling wavelength dip with a narrow bandwidth and a high extinction ratio of over 25 dB. The wavelength dip can also be effectively tuned, greatly shifting with a variation in temperature (T) or refractive index (RI), when the index-matched condition is satisfied. This work demonstrates that the proposed sensor responds sensitively to T with an extremely high tuning efficiency of 50 nm/°C and an excellent sensitivity to RI of 113,500 nm per RI unit.

  5. Temperature-Dependent Refractive Index Measurements of L-BBH2 Glass for the Subaru CHARIS Integral Field Spectrograph

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Groff, Tyler D.

    2015-01-01

    Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have made the first cryogenic measurements of absolute refractive index for Ohara L-BBH2 glass to enable the design of a prism for the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) at the Subaru telescope. L-BBH2 is employed in CHARIS's prism design for improving the spectrograph's dispersion uniformity. Index measurements were made at temperatures from 110 to 305 K at wavelengths from 0.46 to 3.16 micron. We report absolute refractive index (n), dispersion (dn/d(lambda), and thermo-optic coefficient (dn/dT) for this material along with estimated single measurement uncertainties as a function of wavelength and temperature. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures within applicable ranges. This paper also speaks of the challenges in measuring index for a material which is not available in sufficient thickness to fabricate a typical prism for measurement in CHARMS, the tailoring of the index prism design that allowed these index measurements to be made, and the remarkable results obtained from that prism for this practical infrared material.

  6. Temperature-dependent refractive index measurements of L-BBH2 glass for the Subaru CHARIS integral field spectrograph

    NASA Astrophysics Data System (ADS)

    Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Groff, Tyler D.

    2015-09-01

    Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we have made the first cryogenic measurements of absolute refractive index for Ohara L-BBH2 glass to enable the design of a prism for the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) at the Subaru telescope. L-BBH2 is employed in CHARIS's prism design for improving the spectrograph's dispersion uniformity. Index measurements were made at temperatures from 110 to 305 K at wavelengths from 0.46 to 3.16 μm. We report absolute refractive index (n), dispersion (dn/dλ), and thermo-optic coefficient (dn/dT) for this material along with estimated single measurement uncertainties as a function of wavelength and temperature. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures within applicable ranges. This paper also speaks of the challenges in measuring index for a material which is not available in sufficient thickness to fabricate a typical prism for measurement in CHARMS, the tailoring of the index prism design that allowed these index measurements to be made, and the remarkable results obtained from that prism for this practical infrared material.

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

    DOEpatents

    Potter, Jr., Barrett George; Potter, Kelly Simmons

    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. Highly tunable refractive index visible-light metasurface from block copolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Kim, Ju Young; Kim, Hyowook; Kim, Bong Hoon; Chang, Taeyong; Lim, Joonwon; Jin, Hyeong Min; Mun, Jeong Ho; Choi, Young Joo; Chung, Kyungjae; Shin, Jonghwa; Fan, Shanhui; Kim, Sang Ouk

    2016-09-01

    The refractive index of natural transparent materials is limited to 2-3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification.

  9. Highly tunable refractive index visible-light metasurface from block copolymer self-assembly

    PubMed Central

    Kim, Ju Young; Kim, Hyowook; Kim, Bong Hoon; Chang, Taeyong; Lim, Joonwon; Jin, Hyeong Min; Mun, Jeong Ho; Choi, Young Joo; Chung, Kyungjae; Shin, Jonghwa; Fan, Shanhui; Kim, Sang Ouk

    2016-01-01

    The refractive index of natural transparent materials is limited to 2–3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification. PMID:27683077

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

    PubMed

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

    2009-02-01

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

  11. Study on measurement of refractive index profile of GI-POF by light scattering

    NASA Astrophysics Data System (ADS)

    Huifen, Jiang; Xiang'e, Han

    2009-04-01

    This paper is devoted to the study on measurement of refractive index profile of graded-index polymer optical fiber (GI-POF) by light scattering. Using Generalized Airy theory and Debye series of an inhomogeneous cylinder, the scattering intensity distributions are obtained of Airy structure of rainbows for different refractive index profile. The results show that positions of Airy peaks depend closely on refractive index profile of GI-POF. Since each order of rainbow penetrates it to different depths, such methods could be used to provide information of the refractive index profile of GI-POF. For GI-POF with given diameter, positions of Airy peaks of rainbows are simulated as a function of refractive index profile, which can be used to inverse unknown parameters of refractive index profile. The least square method is used in inversion of refractive index profile with the given refractive index of the cladding. The results obtained agree with theoretical values with high precision. The method has the advantages of non-instructive and on-line measurement, and can be used for the measurement of other inhomogeneous droplets.

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

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi

    2005-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

  14. Construction of Lines of Constant Density and Constant Refractive Index for Ternary Liquid Mixtures.

    ERIC Educational Resources Information Center

    Tasic, Aleksandar Z.; Djordjevic, Bojan D.

    1983-01-01

    Demonstrates construction of density constant and refractive index constant lines in triangular coordinate system on basis of systematic experimental determinations of density and refractive index for both homogeneous (single-phase) ternary liquid mixtures (of known composition) and the corresponding binary compositions. Background information,…

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

    PubMed

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

    2014-05-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    In this paper we propose a new approach to using reflectance spectrometry in connection with the Kramers-Kronig analysis for the determination of the complex refractive index of biological cells. Applying this procedure, the real and imaginary parts of the refractive index (refractive index and extinction coefficient) can be simultaneously determined. The accuracy of this procedure in the determination of the refractive index and extinction coefficient of culture media proved to be comparable with spectroscopic ellipsometry. Applying this procedure on the human umbilical vein endothelial cells (HUVEC), the results obtained from time-series measurements showed significant changes in the complex refractive index of cell cultures within 72h, the most important increases for both real and imaginary parts of the refractive index being recorded in the first 24h, when synthesis processes are happening. Thus, the analysis of the time-dependent changes in the complex refractive index provides information about the frequencies of the modifications that occur on both organizational structure and cells composition during the cell cycle. In conclusion, the combination of reflectance spectrometry with the Kramers-Kronig analysis is a feasible way to determine the complex refractive index of biological cells and to assess the events taking place during the cell cycle.

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  18. Measurement of the refractive index of distilled water from the near-infrared region to the ultraviolet region

    NASA Astrophysics Data System (ADS)

    Daimon, Masahiko; Masumura, Akira

    2007-06-01

    By the minimum deviation method using a prism shaped cell, the absolute refractive indices of high-performance liquid chromatography distilled water were measured at the wavelengths from 1129 to 182 nm, at the temperature of 19 °C, 21.5 °C, and 24 °C, and then dn/dt at 21.5 °C was calculated. The coefficients of the four-term Sellmeier dispersion formula were determined by using the refractive indices at each temperature. As a result of the comparison of our refractive index data in the visible wavelength region with the formula by Tilton et al. at the National Bureau of Standards in 1938, both the refractive index data corresponded within 6×10-6. In the UV region, the absolute refractive index at 193.39 nm calculated by the data measured nearby the wavelengths from 200 to 190 nm was 1.436517 (21.5 °C). The value was lower by 9×10-5 or 10×10-5 than the data measured by Burnett et al. at the National Institute of Standards and Technology.

  19. Refractive-index profiling of optical fibers with axial symmetry by use of quantitative phase microscopy.

    PubMed

    Roberts, A; Ampem-Lassen, E; Barty, A; Nugent, K A; Baxter, G W; Dragomir, N M; Huntington, S T

    2002-12-01

    The application of quantitative phase microscopy to refractive-index profiling of optical fibers is demonstrated. Phase images of axially symmetric optical fibers immersed in index-matching fluid are obtained, and the inverse Abel transform is used to obtain the radial refractive-index profile. This technique is straightforward, nondestructive, repeatable, and accurate. Excellent agreement, to within approximately 0.0005, between this method and the index profile obtained with a commercial profiler is obtained.

  20. Refractive index variation in compression molding of precision glass optical components.

    PubMed

    Su, Lijuan; Chen, Yang; Yi, Allen Y; Klocke, Fritz; Pongs, Guido

    2008-04-01

    Compression molding of glass optical components is a high volume near net-shape precision fabrication method. In a compression molding process, a variation of the refractive index occurs along the radial direction of the glass component due to thermal treatment. The variation of refractive index is an important parameter that can affect the performance of optical lenses, especially lenses used for high precision optical systems. Refractive index variations in molded glass lenses under different cooling conditions were investigated using both an experimental approach and a numerical simulation. Specifically, refractive index variations inside molded glass lenses were evaluated by measuring optical wavefront variations with a Shack-Hartmann sensor system. The measured refractive index variations of the molded glass lenses were compared with the numerical simulation as a validation of the modeling approach.

  1. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices

    NASA Astrophysics Data System (ADS)

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó.; Smith, Christopher M.; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V.; Fleischer, Karsten

    2016-09-01

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales.

  2. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices

    PubMed Central

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó; Smith, Christopher M.; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V.; Fleischer, Karsten

    2016-01-01

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales. PMID:27623228

  3. 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.

  4. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices.

    PubMed

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó; Smith, Christopher M; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V; Fleischer, Karsten

    2016-09-13

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales.

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

    PubMed

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

    2014-12-29

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

  6. The role of refractive index gradient on sensitivity and limit of detection of microdisk sensors

    NASA Astrophysics Data System (ADS)

    Najafi, Zohreh; Vahedi, Mohammad; Behjat, Abbas

    2016-09-01

    This paper presents a new type of microdisk resonator sensor with a gradient refractive index (GRIN) that can achieve higher sensitivity with respect to constant refractive index disks. The behavior of the microdisk resonator is simulated by 2D-FDTD method. The shift in the resonance frequency for different thicknesses of the absorbed layer and different refractive index gradients of the microdisks are studied. The best refractive index gradient function is found that leads to the largest sensitivity and smallest limit of detection. The sensitivity of a GRIN microresonator sensor (GMS) with a convex quadratic refractive index function is approximately 11 times as much as that of homogeneous microdisk sensor, which is the best record among GMSs.

  7. [The refractive index sensing characteristics of polarization maintaining microstructured optical fiber chirped grating].

    PubMed

    Guo, Xuan; Bi, Wei-Hong; Liu, Feng

    2013-01-01

    The refractive index sensing characteristics of the polarization maintaining (PM) microstructured optical fiber (MOF) chirped grating was systematically investigated based on finite element method (FEM) and transfer matrix method (TMM). The chirp Bragg grating reflection spectrum was numerically analyzed with the fiber air holes injected with different refractive index medium, and the relation between the reflection spectrum area and the analyte refractive index is discussed here. The analysis results show that when the analyte refractive index increases, the reflection spectrum area will be reduced; and the detection demodulation is simplified with the light intensity demodulation. Moreover, the dependence of the reflection spectrum on the center big holes size, the chirp coefficient and the site function was studied. Since two polarization modes respond similarly to the outside perturbation, the fiber possesses high stability. The results provide the theoretical basis for the application of PM-MOF grating in the optical fiber refractive index sensor and the optical fiber label-free biosensing. PMID:23586270

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

    PubMed

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

    2014-12-29

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

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

    SciTech Connect

    Smith, Charlene M.; Borrelli, Nicholas F.

    2006-09-15

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

  10. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices.

    PubMed

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó; Smith, Christopher M; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V; Fleischer, Karsten

    2016-01-01

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales. PMID:27623228

  11. Refractive index matching improves optical object detection in paper

    NASA Astrophysics Data System (ADS)

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

    2008-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Bahrami, Mehdi; Goncharov, Alexander V.

    2012-05-01

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

  13. Silica Bottle Resonator Sensor for Refractive Index and Temperature Measurements

    PubMed Central

    Nemova, Galina; Kashyap, Raman

    2016-01-01

    We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity ~150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 μm. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be ~10 pm/K. The temperature sensitivity can decrease ~10% for a fiber with a radius rco = 10 μm instead of a fiber with a radius rco = 100 μm. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme. PMID:26761011

  14. Silica Bottle Resonator Sensor for Refractive Index and Temperature Measurements.

    PubMed

    Nemova, Galina; Kashyap, Raman

    2016-01-01

    We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity ~150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 μm. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be ~10 pm/K. The temperature sensitivity can decrease ~10% for a fiber with a radius r(co) = 10 μm instead of a fiber with a radius r(co) = 100 μm. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme. PMID:26761011

  15. Estimating index of refraction from polarimetric hyperspectral imaging measurements.

    PubMed

    Martin, Jacob A; Gross, Kevin C

    2016-08-01

    Current material identification techniques rely on estimating reflectivity or emissivity which vary with viewing angle. As off-nadir remote sensing platforms become increasingly prevalent, techniques robust to changing viewing geometries are desired. A technique leveraging polarimetric hyperspectral imaging (P-HSI), to estimate complex index of refraction, N̂(ν̃), an inherent material property, is presented. The imaginary component of N̂(ν̃) is modeled using a small number of "knot" points and interpolation at in-between frequencies ν̃. The real component is derived via the Kramers-Kronig relationship. P-HSI measurements of blackbody radiation scattered off of a smooth quartz window show that N̂(ν̃) can be retrieved to within 0.08 RMS error between 875 cm-1 ≤ ν̃ ≤ 1250 cm-1. P-HSI emission measurements of a heated smooth Pyrex beaker also enable successful N̂(ν̃) estimates, which are also invariant to object temperature. PMID:27505760

  16. Gradient shadow pattern reveals refractive index of liquid

    NASA Astrophysics Data System (ADS)

    Kim, Wonkyoung; Kim, Dong Sung

    2016-06-01

    We propose a simple method that uses a gradient shadow pattern (GSP) to measure the refractive index nL of liquids. A light source generates a “dark-bright-dark” GSP when it is projected through through the back of a transparent, rectangular block with a cylindrical chamber that is filled with a liquid sample. We found that there is a linear relationship between nL and the proportion of the bright region in a GSP, which provides the basic principle of the proposed method. A wide range 1.33 ≤ nL ≤ 1.46 of liquids was measured in the single measurement setup with error <0.01. The proposed method is simple but robust to illuminating conditions, and does not require for any expensive or precise optical components, so we expect that it will be useful in many portable measurement systems that use nL to estimate attributes of liquid samples.

  17. Gradient shadow pattern reveals refractive index of liquid.

    PubMed

    Kim, Wonkyoung; Kim, Dong Sung

    2016-01-01

    We propose a simple method that uses a gradient shadow pattern (GSP) to measure the refractive index nL of liquids. A light source generates a "dark-bright-dark" GSP when it is projected through through the back of a transparent, rectangular block with a cylindrical chamber that is filled with a liquid sample. We found that there is a linear relationship between nL and the proportion of the bright region in a GSP, which provides the basic principle of the proposed method. A wide range 1.33 ≤ nL ≤ 1.46 of liquids was measured in the single measurement setup with error <0.01. The proposed method is simple but robust to illuminating conditions, and does not require for any expensive or precise optical components, so we expect that it will be useful in many portable measurement systems that use nL to estimate attributes of liquid samples. PMID:27302603

  18. Silica Bottle Resonator Sensor for Refractive Index and Temperature Measurements.

    PubMed

    Nemova, Galina; Kashyap, Raman

    2016-01-09

    We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity ~150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 μm. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be ~10 pm/K. The temperature sensitivity can decrease ~10% for a fiber with a radius r(co) = 10 μm instead of a fiber with a radius r(co) = 100 μm. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme.

  19. Optical measurement of atmospheric refractive index structure constants

    NASA Astrophysics Data System (ADS)

    Qiang, Xiwen; Liu, Jingru; Song, Jianping; Zong, Fei; Zhao, Junwei; Li, Yan

    2009-11-01

    Atmospheric turbulence increases bit error rate and degrades beams quality for wireless laser communication links as laser light propagation in the turbulent atmosphere, and atmospheric refractive index structure constant is an important parameter for statistics of atmospheric turbulence. Characteristics of atmospheric turbulence in the atmosphere varies randomly and the experiments in the real atmosphere are expensive, so it is an important way to simulate atmospheric turbulence in laboratory for investigation on laser beams propagation in through the atmosphere. The structure parameter of the atmospheric turbulence in laboratory was measured based on measurement of angle-of-arrival (AOA) fluctuations of centroids as laser beam through the simulated-turbulence. The results shows a good agreement with the previous result measured by thermal method, the strength of simulated-turbulence was 1000 times stronger than that in the real atmosphere. The characteristics of turbulence varies temporally with air temperature and wind velocity, and statistics of atmospheric turbulence was presented for various air temperature and wind velocity along the propagation path.

  20. Gradient shadow pattern reveals refractive index of liquid

    PubMed Central

    Kim, Wonkyoung; Kim, Dong Sung

    2016-01-01

    We propose a simple method that uses a gradient shadow pattern (GSP) to measure the refractive index nL of liquids. A light source generates a “dark-bright-dark” GSP when it is projected through through the back of a transparent, rectangular block with a cylindrical chamber that is filled with a liquid sample. We found that there is a linear relationship between nL and the proportion of the bright region in a GSP, which provides the basic principle of the proposed method. A wide range 1.33 ≤ nL ≤ 1.46 of liquids was measured in the single measurement setup with error <0.01. The proposed method is simple but robust to illuminating conditions, and does not require for any expensive or precise optical components, so we expect that it will be useful in many portable measurement systems that use nL to estimate attributes of liquid samples. PMID:27302603

  1. Estimating index of refraction from polarimetric hyperspectral imaging measurements.

    PubMed

    Martin, Jacob A; Gross, Kevin C

    2016-08-01

    Current material identification techniques rely on estimating reflectivity or emissivity which vary with viewing angle. As off-nadir remote sensing platforms become increasingly prevalent, techniques robust to changing viewing geometries are desired. A technique leveraging polarimetric hyperspectral imaging (P-HSI), to estimate complex index of refraction, N̂(ν̃), an inherent material property, is presented. The imaginary component of N̂(ν̃) is modeled using a small number of "knot" points and interpolation at in-between frequencies ν̃. The real component is derived via the Kramers-Kronig relationship. P-HSI measurements of blackbody radiation scattered off of a smooth quartz window show that N̂(ν̃) can be retrieved to within 0.08 RMS error between 875 cm-1 ≤ ν̃ ≤ 1250 cm-1. P-HSI emission measurements of a heated smooth Pyrex beaker also enable successful N̂(ν̃) estimates, which are also invariant to object temperature.

  2. Determination of the index of refraction for [alpha]-NTO and DAAF using the Becke test

    SciTech Connect

    Oldenborg, M. R.; Peterson, P. D.; Lee, K. Y.

    2004-01-01

    NTO and DAAF are insensitive high explosives developed at Los Alamos National Laboratory. Both the defense and civilian sectors have particular interest in these types of materials for applications ranging from weapons to air bag design. The performance of explosives is highly dependent on particle size. Many common techniques for measuring particle size distributions require knowledge of the material's index of refraction. To-date the principle refractive indices of {alpha}-NTO and DAAF have not been determined. We present the three principle indices of refraction for the triclinic explosive {alpha}-NTO and an averaged index of refraction for DAAF found using the Becke Test. In addition, by comparing particle size distributions based on different refractive indices we show the importance of using the true index of refraction in measuring fine particles.

  3. 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…

  4. 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.

  5. Effective group index of refraction in non-thermal plasma photonic crystals

    NASA Astrophysics Data System (ADS)

    Mousavi, A.; Sadegzadeh, S.

    2015-11-01

    Plasma photonic crystals (PPCs) are periodic arrays that consist of alternate layers of micro-plasma and dielectric. These structures are used to control the propagation of electromagnetic waves. This paper presents a survey of research on the effect of non-thermal plasma with bi-Maxwellian distribution function on one dimensional PPC. A plasma with temperature anisotropy is not in thermodynamic equilibrium and can be described by the bi-Maxwellian distribution function. By using Kronig-Penny's model, the dispersion relation of electromagnetic modes in one dimensional non-thermal PPC (NPPC) is derived. The band structure, group velocity vg, and effective group index of refraction neff(g) of such NPPC structure with TeO2 as the material of dielectric layers have been studied. The concept of negative group velocity and negative neff(g), which indicates an anomalous behaviour of the PPCs, are also observed in the NPPC structures. Our numerical results provide confirmatory evidence that unlike PPCs there are finite group velocity and non-zero effective group indexes of refraction in photonic band gaps (PBGs) that lie in certain ranges of normalized frequency. In other words, inside the PBGs of NPPCs, neff(g) becomes non-zero and photons travel with a finite group velocity. In this special case, this velocity varies alternately between 20c and negative values of the order 103c (c is the speed of light in vacuum).

  6. Refractive index of solutions of human hemoglobin from the near-infrared to the ultraviolet range: Kramers-Kronig analysis.

    PubMed

    Sydoruk, Oleksiy; Zhernovaya, Olga; Tuchin, Valery; Douplik, Alexandre

    2012-11-01

    Because direct measurements of the refractive index of hemoglobin over a large wavelength range are challenging, indirect methods deserve particular attention. Among them, the Kramers-Kronig relations are a powerful tool often used to derive the real part of a refractive index from its imaginary part. However, previous attempts to apply the relations to solutions of human hemoglobin have been somewhat controversial, resulting in disagreement between several studies. We show that this controversy can be resolved when careful attention is paid not only to the absorption of hemoglobin but also to the dispersion of the refractive index of the nonabsorbing solvent. We present a Kramers-Kroning analysis taking both contributions into account and compare the results with the data from several studies. Good agreement with experiments is found across the visible and parts of near-infrared and ultraviolet regions. These results reinstate the use of the Kramers-Kronig relations for hemoglobin solutions and provide an additional source of information about their refractive index.

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

    NASA Astrophysics Data System (ADS)

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

    1999-06-01

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

  8. Detection of analyte refractive index and concentration using liquid-core photonic Bragg fibers

    NASA Astrophysics Data System (ADS)

    Li, Jingwen; Qu, Hang; Skorobogatiy, Maksim

    2016-03-01

    We demonstrate detection of liquid analyte refractive index by using a hollow-core photonic Bragg fiber. We apply this fiber sensor to monitor concentrations of commercial cooling oil. The sensor operates on a spectral modality. Variation in the analyte refractive index modifies the bandgap guidance of a fiber, leading to spectral shifts in the fiber transmission spectrum. The sensitivity of the sensor to changes in the analyte refractive index filling in the fiber core is found to be 1460nm/Refractive index unit (RIU). By using the spectral modality and effective medium theory, we determine the concentrations of commercial fluid from the measured refractive indices with an accuracy of ~0.42%. The presented fiber sensor can be used for on-line monitoring of concentration of many industrial fluids and dilutions with sub-1%v accuracy.

  9. Terahertz multi-metal-wire hybrid-cladding hollow waveguide for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Ying-Ying, Yu; Xu-You, Li; Kun-Peng, He; Bo, Sun

    2016-02-01

    We propose a design of terahertz refractive index sensing based on the multi-metal-wire (MMW) hybrid-cladding hollow waveguide. The proposed terahertz hybrid-cladding hollow waveguide comprises one air core in the center surrounding MMW surrounded dielectric. The central air core is used for filling lossless measurands and transmitting terahertz light. In particular, the refractive index sensing is realized by measuring the mode field area (MFA) variation of radially polarized mode. The modal effective refractive index, mode field intensity distribution, and mode field area properties responding to the measurand refractive indexes for different operating frequencies and structure dimensions are investigated, respectively. Simulations show that the proposed terahertz refractive index sensor can realize easily the measurement of the measurand refractive index. Meanwhile, the effects of operating frequency and structure parameters on sensitivity and measurement accuracy are also studied. In view of the trade-off between sensitivity and measurement accuracy, the reasonable choice of the operating frequency and structure parameters can optimize appropriately the sensitivity and measurement accuracy, and the sensitivity can reach approximately 0.585 mm2/RIU (RIU is short for refraction index units) with the proper frequency and structure parameter. Project supported by the National Natural Science Foundation of China (Grant No. 51309059).

  10. Effects of refractive index on near-infrared tomography of the breast.

    PubMed

    Dehghani, Hamid; Brooksby, Ben A; Pogue, Brian W; Paulsen, Keith D

    2005-04-01

    Near infrared (NIR) optical tomography is an imaging technique in which internal images of optical properties are reconstructed with the boundary measurements of light propagation through the medium. Recent advances in instrumentation and theory have led to the use of this method for the detection and characterization of tumors within the female breast tissue. Most image reconstruction approaches have used the diffusion approximation and have assumed that the refractive index of the breast is constant, with a bulk value of approximately 1.4. We have applied a previously reported modified diffusion approximation, in which the refractive index for different tissues can be modeled. The model was used to generate NIR data from a realistic breast geometry containing a localized anomaly. Using this simulated data, we have reconstructed optical images, both with and without correct knowledge of the refractive-index distribution to show that the modified diffusion approximation can accurately recover the anomaly given a priori knowledge of refractive index. But using a reconstruction algorithm without the use of correct a priori information regarding the refractive-index distribution is shown as recovering the anomaly but with a degraded quality, depending on the degree of refractive index mismatch. The results suggest that provided the refractive index of breast tissue is approximately 1.3-1.4, their exclusion will have minimal effect on the reconstructed images.

  11. Cell refractive index for cell biology and disease diagnosis: past, present and future.

    PubMed

    Liu, P Y; Chin, L K; Ser, W; Chen, H F; Hsieh, C-M; Lee, C-H; Sung, K-B; Ayi, T C; Yap, P H; Liedberg, B; Wang, K; Bourouina, T; Leprince-Wang, Y

    2016-02-21

    Cell refractive index is a key biophysical parameter, which has been extensively studied. It is correlated with other cell biophysical properties including mechanical, electrical and optical properties, and not only represents the intracellular mass and concentration of a cell, but also provides important insight for various biological models. Measurement techniques developed earlier only measure the effective refractive index of a cell or a cell suspension, providing only limited information on cell refractive index and hence hindering its in-depth analysis and correlation. Recently, the emergence of microfluidic, photonic and imaging technologies has enabled the manipulation of a single cell and the 3D refractive index of a single cell down to sub-micron resolution, providing powerful tools to study cells based on refractive index. In this review, we provide an overview of cell refractive index models and measurement techniques including microfluidic chip-based techniques for the last 50 years, present the applications and significance of cell refractive index in cell biology, hematology, and pathology, and discuss future research trends in the field, including 3D imaging methods, integration with microfluidics and potential applications in new and breakthrough research areas.

  12. Determination of the Dispersion of the Principal Refractive Indices for Birefringent Polypropylene Films

    NASA Astrophysics Data System (ADS)

    Bezruchenko, V. S.; Murauski, An. A.; Muravsky, Al. A.

    2014-07-01

    We present a novel method for determining the dispersion of the refractive indices of birefringent films, based on treatment of transmission spectra, in which we observe interference of light. The dispersion curves n x (λ) and n y (λ) were determined by treatment of transmission spectra obtained for normal incidence of radiation on a P2-25 birefringent fi lm, and n z (λ) was determined for oblique incidence of radiation. From the results of determination of the dispersions of the principal refractive indices of a birefringent P2-25 polypropylene film (Mogilevkhimvolokno OAO, Belarus), we established that the sample is a negative biaxial retarder with N z = 2.9.

  13. Efficient One-Pot Synthesis of Colloidal Zirconium Oxide Nanoparticles for High-Refractive-Index Nanocomposites.

    PubMed

    Liu, Chao; Hajagos, Tibor Jacob; Chen, Dustin; Chen, Yi; Kishpaugh, David; Pei, Qibing

    2016-02-01

    Zirconium oxide nanoparticles are promising candidates for optical engineering, photocatalysis, and high-κ dielectrics. However, reported synthetic methods for the colloidal zirconium oxide nanoparticles use unstable alkoxide precursors and have various other drawbacks, limiting their wide application. Here, we report a facile one-pot method for the synthesis of colloidally stable zirconium oxide nanoparticles. Using a simple solution of zirconium trifluoroacetate in oleylamine, highly stable zirconium oxide nanoparticles have been synthesized with high yield, following a proposed amidization-assisted sol-gel mechanism. The nanoparticles can be readily dispersed in nonpolar solvents, forming a long-term stable transparent solution, which can be further used to fabricate high-refractive-index nanocomposites in both monolith and thin-film forms. In addition, the same method has also been extended to the synthesis of titanium oxide nanoparticles, demonstrating its general applicability to all group IVB metal oxide nanoparticles. PMID:26824518

  14. Efficient One-Pot Synthesis of Colloidal Zirconium Oxide Nanoparticles for High-Refractive-Index Nanocomposites.

    PubMed

    Liu, Chao; Hajagos, Tibor Jacob; Chen, Dustin; Chen, Yi; Kishpaugh, David; Pei, Qibing

    2016-02-01

    Zirconium oxide nanoparticles are promising candidates for optical engineering, photocatalysis, and high-κ dielectrics. However, reported synthetic methods for the colloidal zirconium oxide nanoparticles use unstable alkoxide precursors and have various other drawbacks, limiting their wide application. Here, we report a facile one-pot method for the synthesis of colloidally stable zirconium oxide nanoparticles. Using a simple solution of zirconium trifluoroacetate in oleylamine, highly stable zirconium oxide nanoparticles have been synthesized with high yield, following a proposed amidization-assisted sol-gel mechanism. The nanoparticles can be readily dispersed in nonpolar solvents, forming a long-term stable transparent solution, which can be further used to fabricate high-refractive-index nanocomposites in both monolith and thin-film forms. In addition, the same method has also been extended to the synthesis of titanium oxide nanoparticles, demonstrating its general applicability to all group IVB metal oxide nanoparticles.

  15. Water-Soluble Gold Nanoparticles: From Catalytic Selective Nitroarene Reduction in Water to Refractive Index Sensing.

    PubMed

    Guo, Wusheng; Pleixats, Roser; Shafir, Alexandr

    2015-11-01

    Water-soluble gold nanoparticles (Au NPs) stabilized by a nitrogen-rich poly(ethylene glycol) (PEG)-tagged substrate have been prepared by reduction of HAuCl4 with NaBH4 in water at room temperature. The morphology and size of the nanoparticles can be controlled by simply varying the gold/stabilizer ratio. The nanoparticles have been fully characterized by TEM, high-resolution (HR) TEM, electron diffraction (ED), energy-dispersive X-ray spectroscopy (EDS), UV/Vis, powder XRD, and elemental analysis. The material is efficient as a recyclable catalyst for the selective reduction of nitroarenes with NaBH4 to yield the corresponding anilines in water at room temperature. Furthermore, the potential ability of the Au NPs as a refractive index sensor owing to their localized surface plasmon resonance (LSPR) effect has also been assessed.

  16. Refractive index modulation in polymer film doped with diazo Meldrum's acid

    NASA Astrophysics Data System (ADS)

    Zanutta, Alessio; Villa, Filippo; Bertarelli, Chiara; Bianco, Andrea

    2016-08-01

    Diazo Meldrum's acid undergoes a photoreaction induced by UV light and it is used as photosensitizer in photoresists. Upon photoreaction, a change in refractive index occurs, which makes this system interesting for volume holography. We report on the sublimation effect at room temperature and the effect of photoirradiation on the refractive index in thin films of CAB (Cellulose acetate butyrate) doped with different amount of diazo Meldrum's acid. A net modulation of the refractive index of 0.01 is achieved with 40% of doping ratio together with a reduction of the film thickness.

  17. Reflectivity of a disordered monolayer estimated by graded refractive index and scattering models.

    PubMed

    Diamant, Ruth; Garcí-Valenzuela, Augusto; Fernández-Guasti, Manuel

    2012-09-01

    Reflectivity of a random monolayer, consisting of transparent spherical particles, is estimated using a graded refractive index model, an effective medium approach, and two scattering models. Two cases, a self-standing film and one with a substrate, are considered. Neither the surrounding medium nor the substrate are absorbing materials. Results at normal incidence, with different particle sizes, covering ratios and refractive indexes, are compared. The purpose of this work is to find under which circumstances, for reflectivity at normal incidence, a particle monolayer behaves as a graded refractive index film. PMID:23201948

  18. 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.

  19. The temperature dependence of refractive index of hemoglobin at the wavelengths 930 and 1100 nm

    NASA Astrophysics Data System (ADS)

    Lazareva, Ekaterina N.; Tuchin, Valery V.

    2016-04-01

    In this study, the refractive index of hemoglobin was measured at different temperatures within a physiological range and above that is characteristic to light-blood interaction at laser therapy. Measurements were carried out using the multi-wavelength Abbe refractometer (Atago, Japan). The refractive index was measured at two NIR wavelengths of 930 nm and 1100 nm. Samples of hemoglobin solutions with concentration of 80, 120 and 160 g/l were investigated. The temperature was varied between 25 and 55 °C. It was shown that the dependence of the refractive index of hemoglobin is nonlinear with temperature, which may be associated with changes in molecular structure of hemoglobin.

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

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1992-01-01

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

  1. Photoinduced anisotropy of the refractive index of an azopolymer with liquid-crystal properties

    SciTech Connect

    Andreeva, M S; Shmalgauzen, V I

    2004-01-31

    The formation of a photoinduced refractive-index grating in a photosensitive azopolymer with liquid-crystal (LC) properties is theoretically studied. Equations for photoinduced additions to the refractive index of the LC and amorphous polymers are obtained from balance equations for the distribution densities of trans- and cis-isomers of azodyes. The frequency characteristics of the response of the refractive index to a harmonic perturbation are calculated for different values of the LC order parameter. (interaction of laser radiation with matter. laser plasma)

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

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

  3. Method of producing optical quality glass having a selected refractive index

    DOEpatents

    Poco, John F.; Hrubesh, Lawrence W.

    2000-01-01

    Optical quality glass having a selected refractive index is produced by a two stage drying process. A gel is produced using sol-gel chemistry techniques and first dried by controlled evaporation until the gel volume reaches a pre-selected value. This pre-selected volume determines the density and refractive index of the finally dried gel. The gel is refilled with solvent in a saturated vapor environment, and then dried again by supercritical extraction of the solvent to form a glass. The glass has a refractive index less than the full density of glass, and the range of achievable refractive indices depends on the composition of the glass. Glasses having different refractive indices chosen from an uninterrupted range of values can be produced from a single precursor solution.

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

    SciTech Connect

    Hattori, Koichi; Itakura, Kazunori

    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.

  5. Refractive index dependence on optical gap in amorphous silicon—Part I. Si prepared by glow discharge

    NASA Astrophysics Data System (ADS)

    Ravindra, N. M.; Ance, C.; Coulibaly, S. P.; Chelle, F. De; Berger, J. M.; Ferraton, J. P.; Donnadieu, A.

    1983-03-01

    We present here our studies concerning the variation of refractive index with the optical gap in amorphous silicon prepared by glow discharge decomposition of silane. The study has been carried out in the light of the models of Penn, Wemple-Didomenico, Ravindra et al., Moss and Bahl-Bhagat. It is essentially seen that the model of Bahl-Bhagat is good enough to explain the relative shifts in the refractive indices in terms of the changes in the gaps on introduction of hydrogen into amorphous silicon. However, because of weaknesses associated with the fitting parameters, we propose here an alternate model which explains fairly well the dependence of the index of refraction on the optical gap. Furthermore, to explain the gradient of the refractive index vs optical gap plots, we see that a simple model like that of Moss would suffice. This is all the more interesting by virtue of the fact that the Moss formula is basically representative of the atomic picture. Of course, the constant depends on conditions during formation of the sample. Under some limiting conditions, the Bahl-Bhagat relation is shown to reduce to the linear form like that of Ravindra et al. We also attempt to analyse qualitatively the dependence of dispersion energy and the average excitation energy on temperature in the light of the Wemple-Didomenico model. The present study has been carried out for samples prepared by glow discharge at different substrate temperatures and with different hydrogen concentrations.

  6. Simulation of imperfections in plastic lenses - transferring local refractive index changes into surface shape modifications

    NASA Astrophysics Data System (ADS)

    Arasa, Josep; Pizarro, Carles; Blanco, Patricia

    2016-06-01

    Injection molded plastic lenses have continuously improved their performance regarding optical quality and nowadays are as usual as glass lenses in image forming devices. However, during the manufacturing process unavoidable fluctuations in material density occur, resulting in local changes in the distribution of refractive index, which degrade the imaging properties of the polymer lens. Such material density fluctuations correlate to phase delays, which opens a path for their mapping. However, it is difficult to transfer the measured variations in refractive index into conventional optical simulation tool. Thus, we propose a method to convert the local variations in refractive index into local changes of one surface of the lens, which can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method was tested on a commercial gradient index (GRIN) lens for a set of six different object positions, using the MTF sagittal and tangential cuts to compare the differences between the real lens and a lens with homogenous refractive index, and the last surface converted into a free-form shape containing the internal refractive index changes. The same procedure was used to reproduce the local refractive index changes of an injected plastic lens with local index changes measured using an in-house built polariscopic arrangement, showing the capability of the method to provide successful results.

  7. 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.

  8. Measurement of Refractive Index Gradients by Deflection of a Laser Beam

    ERIC Educational Resources Information Center

    Barnard, A. J.; Ahlborn, B.

    1975-01-01

    In this simple experiment for an undergraduate laboratory a laser beam is passed through the mixing zone of two liquids with different refractive indices. The spatial variation of the refractive index, at different times during the mixing, can be determined from the observed deflection of the beam. (Author)

  9. Temperature-Dependent Refractive Index of Cleartran® ZnS to Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Leviton, Doug; Frey, Brad

    2013-01-01

    First, let's talk about the CHARMS facility at NASA's Goddard Space Flight Center: Cryogenic, High-Accuracy Refraction Measuring System (CHARMS); design features for highest accuracy and precision; technologies we rely on; data products and examples; optical materials for which we've measured cryogenic refractive index.

  10. Refractive Index for Atomic Waves: Theory and Detailed Calculations

    NASA Astrophysics Data System (ADS)

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

    1997-04-01

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

  11. Nonlinear optics in high refractive index contrast photonic crystal microcavities

    NASA Astrophysics Data System (ADS)

    Cowan, Allan Ralph

    2005-07-01

    This thesis describes theoretical and experimental research on the nonlinear response of high refractive index contrast (HRIC) optical microcavities. An intuitive, numerically efficient model of second harmonic reflection from two dimensional (2D), planar photonic crystals made of sub-wavelength thick, non-centrosymmetric semiconductors is developed. It predicts that appropriate 2D texture can result in orders of magnitude enhancement of the reflected second order signal when harmonic plane waves are used to excite leaky photonic crystal eigenmodes. Local field enhancement in the textured slab, and other physical processes responsible for these enhancements are explained. A different formalism is developed to treat the Kerr-related bistable response of a 3D microcavity coupled to a single mode waveguide. This model predicts that optical bistability should be observed using only milliwatts of power to excite a cavity fabricated in Al0.18 Ga0.82As, having a quality factor of Q = 4000 and a mode volume of 0.05 mum 3. Two-photon absorption is shown to only slightly hinder the performance in Al0.18Ga0.82 As. By including nonresonant downstream reflections in the model, novel hysteresis loops are predicted, and their stability is analyzed. A coupled waveguide-microcavity structure is fabricated by selectively cladding a silicon ridge-Bragg grating waveguide with photoresist. Three-dimensionally localized optical modes are realized with Q values ranging from 200 to 1200, at ˜1.5 mum. Using 100 fs pulses, the transmission spectra of these structures is studied as a function of input power. The output power saturates when the cavity mode and pulse centre frequencies are resonant, and the output exhibits superlinear growth when they are appropriately detuned. These results are explained in terms of the filtering action of the microcavity on the nonlinear spectral distortion of the input pulse as it propagates through the waveguide. PbSe nanocrystals are deposited on a

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

    SciTech Connect

    Assanto, Gaetano; Minzoni, Antonmaria A.; Smyth, Noel F.; Worthy, Annette L.

    2010-11-15

    The propagation of solitary waves in nematic liquid crystals in the presence of localized nonuniformities is studied. These nonuniformities can be caused by external electric fields, other light beams, or any other mechanism which results in a modified director orientation in a localized region of the liquid-crystal cell. The net effect is that the solitary wave undergoes refraction and trajectory bending. A general modulation theory for this refraction is developed, and particular cases of circular, elliptical, and rectangular perturbations are considered. The results are found to be in excellent agreement with numerical solutions.

  13. Accurate measurement of refraction and dispersion of a solid by a double-layer interferometer.

    PubMed

    Nassif, A Y

    1997-02-01

    A silica plate of plane-parallel faces is inserted into one gap of a double-layer interferometer that transmits white light to a prism spectrograph in order to produce elliptic rings of equal chromatic order (RECO's). The silica plate is rotated and the expanding RECO's are counted at their center while this center is coincident with a standard wavelength. An analytic formula that relates the fringe count to the rotated angle enables the refractive index of the rotated plate to be accurately determined for different wavelengths. The results are fitted to a single-term Sellmeier dispersion function to find the peak wavelength of the ultraviolet absorption band and the atomic number density for such a transition. The variation of either the dispersion coefficient or the group-velocity factor with wavelength is determined from either the displacement of the RECO center across the visible spectrum if one of the double-layer interferometer's mirrors is displaced parallel to itself or from measurements on the RECO diameters. PMID:18250738

  14. Contribution of Delbrück scattering to the refractive index of substances at mega-electronvolt photon energies

    NASA Astrophysics Data System (ADS)

    Garanin, Sergey F.; Kravets, Ekaterina M.

    2016-10-01

    Recent work by Habs et al. [1] posits that for MeV photons, the contribution of Delbrück scattering to the refractive index of a substance δD becomes dominant as compared with the ordinary polarization contribution due to free electrons. Using the same method suggested Habs et al., we have calculated the contribution of Delbrück scattering using the dispersion relation between δD and the pair creation cross section in the nuclear Coulomb field σp. We have also considered the corrections related to the near-threshold behavior of σp and estimated the contribution of higher-order Delbrück scattering corrections. Our results indicate that δD for MeV photons is small and cannot be responsible for making the index of refraction for silicon larger than unity.

  15. Effect of Ta concentration on the refractive index of TiO2:Ta studied by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Nurfani, Eka; Kurniawan, Robi; Muhammady, Shibghatullah; Marlina, Resti; Sutjahja, Inge M.; Winata, Toto; Rusydi, Andrivo; Darma, Yudi

    2016-04-01

    We have investigated optical properties of Ta-doped TiO2 thin film on LaAlO3 (LAO) substrate using Spectroscopic Ellipsometry (SE) at room temperature. Amplitude ratio Ψ and phase difference L1 between p- and s- polarized light waves are obtained by multiple incident angles measurement (60°, 70°, and 80°) at energy range of 0.5 - 6.5 eV. In order to obtain optical properties for every Ta concentrations (0.01, 0.4, and 5 at. %), multilayer modelling was performed simultaneously by using Drude-Lorentz model. Refractive index and optical dispersion parameters were determined by Wemple-DiDomenico relation. In general, refractive index at zero photon energy n(0) increases by increasing Ta concentration. Furthermore, optical band gap shows a significant increasing due to presence of Ta dopant. In addition, other optical constants are discussed as well.

  16. Nanofluidic refractive-index sensors formed by nanocavity resonators in metals without plasmons.

    PubMed

    Tsai, Shih-Pin; Ma, Yao-Feng; Sung, Ming-Je; Huang, Ding-Wei

    2011-01-01

    Nanocavity resonators in metals acting as nanofluidic refractive-index sensors were analyzed theoretically. With the illumination of transverse electric polarized light, the proposed refractive index sensor structure acts as a pure electromagnetic resonator without the excitation of surface plasmons. The reflected signal from the nanocavity resonators can be very sensitive to the refractive index of the fluids inside the nanocavities due to the enhancement of the electric field of the resonant mode inside the cavities. Such a sensor configuration can be a useful tool for probing the refractive index change of the fluid inside the nanocavities using the spectral, angular or intensity interrogation schemes. The wavelength sensitivity of 430 nm/RIU, angular sensitivity of 200-1,000 deg/RIU and intensity sensitivity of 25.5 RIU(-1) can be achieved in the proposed sensor configuration.

  17. Equivalent refractive-index structure constant of non-Kolmogorov turbulence.

    PubMed

    Li, Yujie; Zhu, Wenyue; Wu, Xiaoqing; Rao, Ruizhong

    2015-09-01

    The relationship between the non-Kolmogorov refractive-index structure constant and the Kolmogorov refractive-index structure constant is derived by using the refractive-index structure function and the variance of refractive-index fluctuations. It shows that the non-Kolmogorov structure constant is proportional to the Kolmogorov structure constant and the scaling factor depends on the outer scale and the spectral power law. For a fixed Kolmogorov structure constant, the non-Kolmogorov structure constant increases with a increasing outer scale for the power law less than 11/3, the trend is opposite for the power law greater than 11/3. This equivalent relation provides a way of obtaining the non-Kolmogorov structure constant by using the Kolmogorov structure constant.

  18. Determining the size and refractive index of microspheres using the mode assignments from Mie resonances.

    PubMed

    Preston, Thomas C; Reid, Jonathan P

    2015-11-01

    A new method for determining the radius and refractive index of microspheres using Mie resonances is presented. Previous methods have relied on searching multidimensional space to find the radius and refractive index that minimize the difference between observed and calculated Mie resonances. For anything but simple refractive index functions, this process can be very time consuming. Here, we demonstrate that once the mode assignment for the observed Mie resonances is known, no search is necessary, and the radius and refractive index of best-fit can be found immediately. This superior and faster way to characterize microspheres using Mie resonances should supplant previous fitting algorithms. The derivation and implementation of the equations that give the parameters of best-fit are shown and discussed. Testing is performed on systems of physical interest, and the effect of noise on measured peak positions is investigated.

  19. Simultaneous determination of refractive index and size of spherical dielectric particles from light scattering data.

    PubMed

    Chylek, P; Ramaswamy, V; Ashkin, A; Dziedzic, J M

    1983-08-01

    The diameter and refractive index of micrometer sized spherical dielectric particles are simultaneously deduced using the wavelength dependence of backscattering data from optically levitated particles. The accuracy of the results is set by experimental errors in the determination of the wavelength of backscatter resonance peaks and the ratio of slopes of specified peaks. At present the refractive index and diameter can be deduced with relative errors of 5 x 10(-5). This represents the most accurate determination of absolute size and refractive index yet made by light scattering. A reduction of these errors by an order of magnitude is possible. We assume a priori knowledge of diameter and refractive index with accuracy of 10(-1) and 5 x 10(-3), respectively.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  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.

  2. 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.

  3. 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.

  4. 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

  5. Characterization and simulation on antireflective coating of amorphous silicon oxide thin films with gradient refractive index

    NASA Astrophysics Data System (ADS)

    Huang, Lu; Jin, Qi; Qu, Xingling; Jin, Jing; Jiang, Chaochao; Yang, Weiguang; Wang, Linjun; Shi, Weimin

    2016-08-01

    The optical reflective properties of silicon oxide (SixOy) thin films with gradient refractive index are studied both theoretically and experimentally. The thin films are widely used in photovoltaic as antireflective coatings (ARCs). An effective finite difference time domain (FDTD) model is built to find the optimized reflection spectra corresponding to structure of SixOy ARCs with gradient refractive index. Based on the simulation analysis, it shows the variation of reflection spectra with gradient refractive index distribution. The gradient refractive index of SixOy ARCs can be obtained in adjustment of SiH4 to N2O ratio by plasma-enhanced chemical vapor deposition (PECVD) system. The optimized reflection spectra measured by UV-visible spectroscopy confirms to agree well with that simulated by FDTD method.

  6. The eye lens: age-related trends and individual variations in refractive index and shape parameters

    PubMed Central

    Pierscionek, Barbara; Bahrami, Mehdi; Hoshino, Masato; Uesugi, Kentaro; Regini, Justyn; Yagi, Naoto

    2015-01-01

    The eye lens grows throughout life by cell accrual on its surface and can change shape to adjust the focussing power of the eye. Varying concentrations of proteins in successive cell layers create a refractive index gradient. The continued growth of the lens and age-related changes in proteins render it less able to alter shape with loss of capacity by the end of the sixth decade of life. Growth and protein ageing alter the refractive index but as accurate measurement of this parameter is difficult, the nature of such alterations remains uncertain. The most accurate method to date for measuring refractive index in intact lenses has been developed at the SPring-8 synchrotron. The technique, based on Talbot interferometry, has an X-ray source and was used to measure refractive index in sixty-six human lenses, aged from 16 to 91 years. Height and width were measured for forty-five lenses. Refractive index contours show decentration in some older lenses but individual variations mask age-related trends. Refractive index profiles along the optic axis have relatively flat central sections with distinct micro-fluctuations and a steep gradient in the cortex but do not exhibit an age-related trend. The refractive index profiles in the equatorial aspect show statistical significance with age, particularly for lenses below the age of sixty that had capacity to alter shape in vivo. The maximum refractive index in the lens centre decreases slightly with age with considerable scatter in the data and there are age-related variations in sagittal thickness and equatorial height. PMID:26416418

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

    PubMed

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

    2014-05-21

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

  9. Femtosecond laser induced refractive index structures in polymer optical fibre (POF) for sensing

    NASA Astrophysics Data System (ADS)

    Liang, S. J.; Scully, P. J.; Schille, J.; Vaughan, J.; Perrie, W.

    2009-10-01

    Techniques to directly write localised refractive index structures in polymer optical fibres (POF) are presented, using UV (400nm) ultrafast laser with pulse lengths of 100 fs to create in-fibre gratings for sensing. No doping is necessary for photosensitisation so commercially available POF is used. An in-fibre grating consisting of a 1.8 μm wide refractive index structure with a periodicity of 189 nm was demonstrated in single mode polymer fibre with optimised laser processing parameters.

  10. The eye lens: age-related trends and individual variations in refractive index and shape parameters.

    PubMed

    Pierscionek, Barbara; Bahrami, Mehdi; Hoshino, Masato; Uesugi, Kentaro; Regini, Justyn; Yagi, Naoto

    2015-10-13

    The eye lens grows throughout life by cell accrual on its surface and can change shape to adjust the focussing power of the eye. Varying concentrations of proteins in successive cell layers create a refractive index gradient. The continued growth of the lens and age-related changes in proteins render it less able to alter shape with loss of capacity by the end of the sixth decade of life. Growth and protein ageing alter the refractive index but as accurate measurement of this parameter is difficult, the nature of such alterations remains uncertain. The most accurate method to date for measuring refractive index in intact lenses has been developed at the SPring-8 synchrotron. The technique, based on Talbot interferometry, has an X-ray source and was used to measure refractive index in sixty-six human lenses, aged from 16 to 91 years. Height and width were measured for forty-five lenses. Refractive index contours show decentration in some older lenses but individual variations mask age-related trends. Refractive index profiles along the optic axis have relatively flat central sections with distinct micro-fluctuations and a steep gradient in the cortex but do not exhibit an age-related trend. The refractive index profiles in the equatorial aspect show statistical significance with age, particularly for lenses below the age of sixty that had capacity to alter shape in vivo. The maximum refractive index in the lens centre decreases slightly with age with considerable scatter in the data and there are age-related variations in sagittal thickness and equatorial height.

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

    DOEpatents

    Veligdan, James T.

    2001-01-01

    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.

  12. The eye lens: age-related trends and individual variations in refractive index and shape parameters.

    PubMed

    Pierscionek, Barbara; Bahrami, Mehdi; Hoshino, Masato; Uesugi, Kentaro; Regini, Justyn; Yagi, Naoto

    2015-10-13

    The eye lens grows throughout life by cell accrual on its surface and can change shape to adjust the focussing power of the eye. Varying concentrations of proteins in successive cell layers create a refractive index gradient. The continued growth of the lens and age-related changes in proteins render it less able to alter shape with loss of capacity by the end of the sixth decade of life. Growth and protein ageing alter the refractive index but as accurate measurement of this parameter is difficult, the nature of such alterations remains uncertain. The most accurate method to date for measuring refractive index in intact lenses has been developed at the SPring-8 synchrotron. The technique, based on Talbot interferometry, has an X-ray source and was used to measure refractive index in sixty-six human lenses, aged from 16 to 91 years. Height and width were measured for forty-five lenses. Refractive index contours show decentration in some older lenses but individual variations mask age-related trends. Refractive index profiles along the optic axis have relatively flat central sections with distinct micro-fluctuations and a steep gradient in the cortex but do not exhibit an age-related trend. The refractive index profiles in the equatorial aspect show statistical significance with age, particularly for lenses below the age of sixty that had capacity to alter shape in vivo. The maximum refractive index in the lens centre decreases slightly with age with considerable scatter in the data and there are age-related variations in sagittal thickness and equatorial height. PMID:26416418

  13. Refraction index of shock compressed water in the megabar pressure range

    NASA Astrophysics Data System (ADS)

    Batani, D.; Jakubowska, K.; Benuzzi-Mounaix, A.; Cavazzoni, C.; Danson, C.; Hall, T.; Kimpel, M.; Neely, D.; Pasley, J.; Rabec Le Gloahec, M.; Telaro, B.

    2015-11-01

    We compressed water to megabar pressures by laser-driven shock waves and evidenced transparent, opaque and reflecting phases as pressure increases. The refraction index of water in the first two states was measured using a VISAR system. At high compression a sharp increase of the real and imaginary part of the refraction index is observed. Experiments were performed at the LULI and RAL laboratories.

  14. Investigation of negative index in dispersive, chiral materials via contra-propagating velocities under second-order dispersion (GVD)

    NASA Astrophysics Data System (ADS)

    Chatterjee, Monish R.; Algadey, Tarig

    2013-09-01

    Negative refractive index arises typically in metamaterials via multiple routes. One such avenue is the condition where the Poynting vector of the electromagnetic wave is in opposition to the group velocity in the material. An earlier work along this route in a chiral material led to the well-known result of requiring very large (non-realizable) chirality. Thereafter, a combination of chirality together with first-order dispersion was examined using plane wave electromagnetic analysis. To arrive at the conclusions in that approach, the three wave velocities (energy, group and phase) were derived under first-order dispersion in permittivity, permeability and chirality. Negative index in this approach was established under the condition of contra-propagating group and phase velocities. Regions of negative index were found analytically by assuming standard dispersive models (such as Condon). In this paper, we will re-visit the negative index problem under higher-order dispersion. In addition, we will re-examine the plane wave propagation model under parametric dispersion where each material parameter (ɛ, μ, κ) is dispersively expanded up to the second order in frequency. Such a physical effect may be traced to group velocity dispersion (GVD) in the material. Field solutions are then obtained under the GVD effect, and extended to the evaluation of the energy, phase and group velocities.

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

    DOEpatents

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

    1984-06-19

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

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

    DOEpatents

    Yeung, Edward S.; Woodruff, Steven D.

    1984-06-19

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

  17. Polarimetry of moonlight: A new method for determining the refractive index of the lunar regolith

    NASA Astrophysics Data System (ADS)

    Fearnside, Andrew; Masding, Philip; Hooker, Chris

    2016-04-01

    We present a new method for remotely measuring the refractive index of the lunar regolith, using polarised moonlight. Umov's Law correlates the polarisation (Pmax) of scattered moonlight and the albedo (A) of the scattering lunar regolith. We discuss how deviations from this correlation have previously been linked to the so-called 'Polarimetric Anomaly Parameter', (Pmax)aA, which was proposed by Shkuratov and others as being related to variations in regolith grain size. We propose a reinterpretation of that parameter. We develop models of light scattering by regolith grains which predict that variation in the refractive index of regolith grains causes deviations from Umov's Law. Variations in other grain parameters such as grain size and degree of space weathering do not produce this deviation. The models are supported by polarimetric measurements on powdered terrestrial materials of differing refractive index. We derive a simple formula to express the relationship between refractive index and the deviation from Umov's Law and apply it to telescopic measurements of regions of the lunar surface. We show that the Aristarchus Plateau and the Marius Hills regions both comprise materials of unusually low refractive index. These results are consistent with recent estimates of the mineralogy of those areas. Picard and Peirce craters, in Mare Crisium, are shown to contain material of low refractive index similar to highland regions, as has been suggested by earlier studies of these craters.

  18. Refractive index measurements of single, spherical cells using digital holographic microscopy.

    PubMed

    Schürmann, Mirjam; Scholze, Jana; Müller, Paul; Chan, Chii J; Ekpenyong, Andrew E; Chalut, Kevin J; Guck, Jochen

    2015-01-01

    In this chapter, we introduce digital holographic microscopy (DHM) as a marker-free method to determine the refractive index of single, spherical cells in suspension. The refractive index is a conclusive measure in a biological context. Cell conditions, such as differentiation or infection, are known to yield significant changes in the refractive index. Furthermore, the refractive index of biological tissue determines the way it interacts with light. Besides the biological relevance of this interaction in the retina, a lot of methods used in biology, including microscopy, rely on light-tissue or light-cell interactions. Hence, determining the refractive index of cells using DHM is valuable in many biological applications. This chapter covers the main topics that are important for the implementation of DHM: setup, sample preparation, and analysis. First, the optical setup is described in detail including notes and suggestions for the implementation. Following that, a protocol for the sample and measurement preparation is explained. In the analysis section, an algorithm for the determination of quantitative phase maps is described. Subsequently, all intermediate steps for the calculation of the refractive index of suspended cells are presented, exploiting their spherical shape. In the last section, a discussion of possible extensions to the setup, further measurement configurations, and additional analysis methods are given. Throughout this chapter, we describe a simple, robust, and thus easily reproducible implementation of DHM. The different possibilities for extensions show the diverse fields of application for this technique.

  19. Method of determining effects of heat-induced irregular refractive index on an optical system.

    PubMed

    Song, Xifa; Li, Lin; Huang, Yifan

    2015-09-01

    The effects of an irregular refractive index on optical performance are examined. A method was developed to express a lens's irregular refractive index distribution. An optical system and its mountings were modeled by a thermomechanical finite element (FE) program in the predicted operating temperature range, -45°C-50°C. FE outputs were elaborated using a MATLAB optimization routine; a nonlinear least squares algorithm was adopted to determine which gradient equation best fit each lens's refractive index distribution. The obtained gradient data were imported into Zemax for sequential ray-tracing analysis. The root mean square spot diameter, modulation transfer function, and diffraction ensquared energy were computed for an optical system under an irregular refractive index and under thermoelastic deformation. These properties are greatly reduced by the irregular refractive index effect, which is one-third to five-sevenths the size of the thermoelastic deformation effect. Thus, thermal analyses of optical systems should consider not only thermoelastic deformation but also refractive index irregularities caused by inhomogeneous temperature.

  20. Refractive index measurements of single, spherical cells using digital holographic microscopy.

    PubMed

    Schürmann, Mirjam; Scholze, Jana; Müller, Paul; Chan, Chii J; Ekpenyong, Andrew E; Chalut, Kevin J; Guck, Jochen

    2015-01-01

    In this chapter, we introduce digital holographic microscopy (DHM) as a marker-free method to determine the refractive index of single, spherical cells in suspension. The refractive index is a conclusive measure in a biological context. Cell conditions, such as differentiation or infection, are known to yield significant changes in the refractive index. Furthermore, the refractive index of biological tissue determines the way it interacts with light. Besides the biological relevance of this interaction in the retina, a lot of methods used in biology, including microscopy, rely on light-tissue or light-cell interactions. Hence, determining the refractive index of cells using DHM is valuable in many biological applications. This chapter covers the main topics that are important for the implementation of DHM: setup, sample preparation, and analysis. First, the optical setup is described in detail including notes and suggestions for the implementation. Following that, a protocol for the sample and measurement preparation is explained. In the analysis section, an algorithm for the determination of quantitative phase maps is described. Subsequently, all intermediate steps for the calculation of the refractive index of suspended cells are presented, exploiting their spherical shape. In the last section, a discussion of possible extensions to the setup, further measurement configurations, and additional analysis methods are given. Throughout this chapter, we describe a simple, robust, and thus easily reproducible implementation of DHM. The different possibilities for extensions show the diverse fields of application for this technique. PMID:25640428

  1. 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.

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

    SciTech Connect

    Petrin, A. B.

    2008-09-15

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

  3. Effects of refractive index mismatch in optical CT imaging of polymer gel dosimeters

    SciTech Connect

    Manjappa, Rakesh; Makki S, Sharath; Kanhirodan, Rajan; Kumar, Rajesh

    2015-02-15

    Purpose: Proposing an image reconstruction technique, algebraic reconstruction technique-refraction correction (ART-rc). The proposed method takes care of refractive index mismatches present in gel dosimeter scanner at the boundary, and also corrects for the interior ray refraction. Polymer gel dosimeters with high dose regions have higher refractive index and optical density compared to the background medium, these changes in refractive index at high dose results in interior ray bending. Methods: The inclusion of the effects of refraction is an important step in reconstruction of optical density in gel dosimeters. The proposed ray tracing algorithm models the interior multiple refraction at the inhomogeneities. Jacob’s ray tracing algorithm has been modified to calculate the pathlengths of the ray that traverses through the higher dose regions. The algorithm computes the length of the ray in each pixel along its path and is used as the weight matrix. Algebraic reconstruction technique and pixel based reconstruction algorithms are used for solving the reconstruction problem. The proposed method is tested with numerical phantoms for various noise levels. The experimental dosimetric results are also presented. Results: The results show that the proposed scheme ART-rc is able to reconstruct optical density inside the dosimeter better than the results obtained using filtered backprojection and conventional algebraic reconstruction approaches. The quantitative improvement using ART-rc is evaluated using gamma-index. The refraction errors due to regions of different refractive indices are discussed. The effects of modeling of interior refraction in the dose region are presented. Conclusions: The errors propagated due to multiple refraction effects have been modeled and the improvements in reconstruction using proposed model is presented. The refractive index of the dosimeter has a mismatch with the surrounding medium (for dry air or water scanning). The algorithm

  4. 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

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  7. Effective group index of refraction in non-thermal plasma photonic crystals

    SciTech Connect

    Mousavi, A.; Sadegzadeh, S.

    2015-11-15

    Plasma photonic crystals (PPCs) are periodic arrays that consist of alternate layers of micro-plasma and dielectric. These structures are used to control the propagation of electromagnetic waves. This paper presents a survey of research on the effect of non-thermal plasma with bi-Maxwellian distribution function on one dimensional PPC. A plasma with temperature anisotropy is not in thermodynamic equilibrium and can be described by the bi-Maxwellian distribution function. By using Kronig-Penny's model, the dispersion relation of electromagnetic modes in one dimensional non-thermal PPC (NPPC) is derived. The band structure, group velocity v{sub g}, and effective group index of refraction n{sub eff}(g) of such NPPC structure with TeO{sub 2} as the material of dielectric layers have been studied. The concept of negative group velocity and negative n{sub eff}(g), which indicates an anomalous behaviour of the PPCs, are also observed in the NPPC structures. Our numerical results provide confirmatory evidence that unlike PPCs there are finite group velocity and non-zero effective group indexes of refraction in photonic band gaps (PBGs) that lie in certain ranges of normalized frequency. In other words, inside the PBGs of NPPCs, n{sub eff}(g) becomes non-zero and photons travel with a finite group velocity. In this special case, this velocity varies alternately between 20c and negative values of the order 10{sup 3}c (c is the speed of light in vacuum)

  8. Flat band degeneracy and near-zero refractive index materials in acoustic crystals

    NASA Astrophysics Data System (ADS)

    Wu, Shiqiao; Mei, Jun

    2016-01-01

    A Dirac-like cone is formed by utilizing the flat bands associated with localized modes in an acoustic crystal (AC) composed of a square array of core-shell-structure cylinders in a water host. Although the triply-degeneracy seems to arise from two almost-overlapping flat bands touching another curved band, the enlarged view of the band structure around the degenerate point reveals that there are actually two linear bands intersecting each other at the Brillouin zone center, with another flat band passing through the same crossing point. The linearity of dispersion relations is achieved by tuning the geometrical parameters of the cylindrical scatterers. A perturbation method is used to not only accurately predict the linear slopes of the dispersions, but also confirm the linearity of the bands from first principles. An effective medium theory based on coherent potential approximation is developed, and it shows that a slab made of the AC carries a near-zero refractive index around the Dirac-like point. Full-wave simulations are performed to unambiguously demonstrate the wave manipulating properties of the AC structures such as perfect transmission, unidirectional transmission and wave front shaping.

  9. Interferometric determination of refraction and dispersion of human blood-serum, saliva, sweat and urine

    NASA Astrophysics Data System (ADS)

    El-Zaiat, S. Y.

    2003-02-01

    Multiple-beam interference fringes of equal chromatic order are produced in air and liquid sample interferometric gaps. The two gaps are of the same thickness and simultaneously enclosed in a wedge interferometer. A single shot interferogram containing fringes in the two gaps is sufficient to deduce the needed experimental data. Locations of the fringe maxima, in the two gaps, are introduced in a non-numerical procedure for determining the gap thickness and the liquid-phase refractive indices across the visible spectrum. The method has been used for measuring the phase refractive indices of human blood-serum, saliva, sweat, urine and water liquids. A third-order polynomial dispersion relation is applied for fitting the measured phase indices. Group refractive indices have been derived and fitted to the same dispersion formula.

  10. Simultaneous estimation of thickness and refractive index of layered gradient refractive index optics using a hybrid confocal-scan swept-source optical coherence tomography system.

    PubMed

    Yao, Jianing; Huang, Jinxin; Meemon, Panomsak; Ponting, Michael; Rolland, Jannick P

    2015-11-16

    A hybrid confocal-scan swept-source optical coherence tomography metrology system was conceived for simultaneous measurements of the refractive index and thickness profiles of polymeric layered gradient refractive index (GRIN) optics. An uncertainty analysis predicts the metrology capability of the system and guides the selection of an optimum working numerical aperture. Experimental results on both a monolithic and a GRIN layered sheet are demonstrated to be in close agreement with theoretical predictions. Index measurement precision reached 0.0001 and 0.0008 for measuring 2.8 mm and ~300 µm thick layers, respectively. The thicknesses of these layers were simultaneously measured with a precision of 0.28 and 0.17 µm, respectively.

  11. High Refraction Index Polysiloxanes via Organometallic Routes - An Overview

    NASA Astrophysics Data System (ADS)

    Stańzyk, Włodzimierz A.; Czech, Anna; Duczmal, Wojciech; Ganicz, Tomasz; Noskowska, Małgorzata; Szeląg, Anna

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

  12. Integrated microsphere whispering gallery mode probe for highly sensitive refractive index measurement

    NASA Astrophysics Data System (ADS)

    Wang, Hanzheng; Yuan, Lei; Kim, Cheol-Woon; Huang, Jie; Lan, Xinwei; Xiao, Hai

    2016-06-01

    We report an integrated whispering gallery mode microresonator-based sensor probe for refractive index sensing. The probe was made by sealing a borosilicate glass microsphere into a thin-wall glass capillary pigtailed with a multimode optical fiber. The intensities of the resonant peaks were found decreasing exponentially (linearly in a log scale) with the increasing refractive index of the medium surrounding the capillary. The sensing capability of the integrated probe was tested using sucrose solutions of different concentrations and the resolution was estimated to be about 2.5×10-5 in the index range of 1.3458 to 1.3847. The integrated sensor probe may prove useful in many chemical and biological sensing applications where highly sensitive refractive index monitoring is needed.

  13. Arc-discharge effects on residual stress and refractive index in single-mode optical fibers.

    PubMed

    Wang, Pengfei; Jenkins, Micah H; Gaylord, Thomas K

    2016-03-20

    Arc-discharge effects on the residual stress and refractive index in single-mode optical fibers are investigated using a previously developed three-dimensional concurrent stress-index measurement method. Using commercial optical fibers and a commercial fusion splicer, the residual stress and refractive index perturbations caused by weak electrical arc discharges in single-mode fibers were measured. Refractive index changes greater than 10-4 and longitudinal perturbation lengths of less than 500 μm were shown to be possible. The subsequent prospects for arc-induced long-period fiber gratings are analyzed, and a typical transmission resonance is predicted to have a depth of 56 dB and a bandwidth of 0.08 nm at a wavelength of 1585 nm. The results of this investigation will be useful in modeling device performance and optimization of arc-induced long-period fiber grating fabrication.

  14. 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…

  15. 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.

  16. Towards refractive index sensitivity of long-period gratings at level of tens of µm per refractive index unit: fiber cladding etching and nano-coating deposition.

    PubMed

    Śmietana, Mateusz; Koba, Marcin; Mikulic, Predrag; Bock, Wojtek J

    2016-05-30

    In this work we report experimental results on optimizing the refractive index (RI) sensitivity of long-period gratings (LPGs) by fiber cladding etching and thin aluminum oxide (Al2O3) overlay deposition. The presented LPG takes advantage of work in the dispersion turning point (DTP) regime as well as the mode transition (MT) effect for higher-order cladding modes (LP09 and LP010). The MT was obtained by depositing Al2O3 overlays with single-nanometer precision using the Atomic Layer Deposition method (ALD). Etching of both the overlay and the fiber cladding was performed using hydrofluoric acid (HF). For shallow etching of the cladding, i.e., DTP observed at next = 1.429 and 1.439 RIU for an LPG with no overlay, followed by deposition of an overlay of up to 167 nm in thickness, HF etching allowed for post-deposition fine-tuning of the overlay thickness resulting in a significant increase in RI sensitivity mainly at the DTP of the LP09 cladding mode. However, at an external RI (next) above 1.39 RIU, the DTP of LP010 was noticed, and its RI sensitivity exceeded 9,000 nm/RIU. Deeper etching of the cladding, i.e., DTP observed for next above 1.45 RIU, followed by the deposition of thicker overlays (up to 201 nm in thickness) allowed the sensitivity to reach values of over 40,000 nm/RIU in a narrow RI range. Sensitivity exceeding 20,000 nm/RIU was obtained in an RI range suitable for label-free biosensing applications. PMID:27410112

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

    SciTech Connect

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

    2003-07-24

    A new method was developed to determine both diameters and indices of refraction and hence the birefringence of cylindrical textile and industrial fibers and bundles by measuring intensity patterns of the scattered light over an interval of scattering angles. The measured intensity patterns are compared with theoretical predictions (Mie theory) to determine fiber diameter and index of refraction. It is shown that the method is simple and accurate and may be useful as an on-line, noncontact diagnostic tool in real time.

  18. 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.

  19. Control of Refractive Index of Fluorinated Polyimide by Proton Beam Irradiation

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    The refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, the refractive index contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving-parts approach that provides three-dimensional refractive-index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate refractive-index maps of the samples from the measured spectra. Using this method, we demonstrate label-free three-dimensional imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass, and density of these cells from the measured three-dimensional refractive-index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, shows promise as a quantitative tool for stain-free characterization of a large number of cells.

  1. Using a laser source to measure the refractive index of glass beads and Debye theory analysis.

    PubMed

    Li, Shui-Yan; Qin, Shuang; Li, Da-Hai; Wang, Qiong-Hua

    2015-11-20

    Using a monochromatic laser beam to illuminate a homogeneous glass bead, some rainbows will appear around it. This paper concentrates on the study of the scattering intensity distribution and the method of measuring the refractive index for glass beads based on the Debye theory. It is found that the first rainbow due to the scattering superposition of backward light of the low-refractive-index glass beads can be explained approximately with the diffraction, the external reflection plus the one internal reflection, while the second rainbow of high-refractive-index glass beads is due to the contribution from the diffraction, the external reflection, the direct transmission, and the two internal reflections. The scattering intensity distribution is affected by the refractive index, the radius of the glass bead, and the incident beam width. The effects of the refractive index and the glass bead size on the first and second minimum deviation angle position are analyzed in this paper. The results of the measurements agree very well with the specifications.

  2. Needle-probe system for the measurement of tissue refractive index

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

    Needle-based devices, which are in wide clinical use for needle biopsy procedures, may be augmented by suitable optical techniques for the localization and diagnosis of diseased tissue. Tissue refractive index is one optical contrast mechanism with diagnostic potential. In the case of mammary tissue, for example, recent research indicates that refractive index variations between tissue types may be useful for the identification of cancerous tissue. While many coherence-based forward-sensing devices have been developed to detect scattering changes, none have demonstrated refractive index measurement capabilities. We present a novel needle-based device that is capable of simultaneously measuring refractive index and scattering. Coupled to the sample arm of an optical coherence tomography system, the needle device detects the scattering response and optical pathlength through tissue residing in a fixed-width channel. Near-infrared measurements of tissues and materials with known optical properties using a prototype device will be presented. This work demonstrates the feasibility of integrated in vivo measurement of refractive index and scattering in conjunction with existing clinical needle-based devices.

  3. 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.

  4. Infrared non-planar plasmonic perfect absorber for enhanced sensitive refractive index sensing

    NASA Astrophysics Data System (ADS)

    Cheng, Yongzhi; Mao, Xue Song; Wu, Chenjun; Wu, Lin; Gong, RongZhou

    2016-03-01

    We present a non-planar all-metal plasmonic perfect absorber (PA) with response polarization independent in infrared region, which can be served as a sensor for enhanced refractive index sensing. Distinct from previous designs, the proposed PA consisted of all metal structured film constructed with an assembly of four-tined rod resonators (FRRs). The PA with a high quality-factor (Q-factor) of 41.2 and an absorbance of 99.9% at 142.6 THz has been demonstrated numerically. The resonance behavior occurs in the space between the rods of the FRRs, which is remarkable different conventional sandwiched structural PAs. Based on equivalent LC circuit theory, the absorption peak can be finely tuned by varying the geometrical dimensions of the FRRs. Furthermore, the resonance frequency shows highly sensitive response to the change of refractive index in the surrounding medium. A careful design for refractive index sensor can yield a sensitivity of 1445 nm/refractive index unit (RIU) and a figure of merit (FOM) of 28.8. The demonstrated design of the plasmonic PA for sensing provides great potential application in enhancing refractive index sensors and the enhanced infrared spectroscopy.

  5. 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

  6. 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.

  7. Using a laser source to measure the refractive index of glass beads and Debye theory analysis.

    PubMed

    Li, Shui-Yan; Qin, Shuang; Li, Da-Hai; Wang, Qiong-Hua

    2015-11-20

    Using a monochromatic laser beam to illuminate a homogeneous glass bead, some rainbows will appear around it. This paper concentrates on the study of the scattering intensity distribution and the method of measuring the refractive index for glass beads based on the Debye theory. It is found that the first rainbow due to the scattering superposition of backward light of the low-refractive-index glass beads can be explained approximately with the diffraction, the external reflection plus the one internal reflection, while the second rainbow of high-refractive-index glass beads is due to the contribution from the diffraction, the external reflection, the direct transmission, and the two internal reflections. The scattering intensity distribution is affected by the refractive index, the radius of the glass bead, and the incident beam width. The effects of the refractive index and the glass bead size on the first and second minimum deviation angle position are analyzed in this paper. The results of the measurements agree very well with the specifications. PMID:26836524

  8. Electrospray deposition of chalcogenide glass films for gradient refractive index and quantum dot incorporation

    NASA Astrophysics Data System (ADS)

    Novak, Spencer

    -to-roll processing whereby (theoretically) 100% of starting solution can be utilized in a continuous process. The present effort has shown that electrospray offers the advantage of spatially defined, localized deposition, which enables direct 2-D and 3-D printing, though with limited (unoptimized) spatial resolution on the order of millimeters. Knowledge of processing protocols were exploited to fabricate multi-layer films from two different glass compositions to yield an effective refractive index gradient (GRIN). GRIN coatings were fabricated and refractive index variations were predicted. The advantages of electrospray deposition were also explored for the enhancement of quantum dot doping in ChG films. A hypothesis whereby electrospray would enable deposition of films based on consolidation of many, single QD doped aerosol droplets was developed and evaluated. Experimental validation of this premise in CdSe and PbS doped ChG films was shown, indicating that electrospray offers a kinetic barrier to QD movement preventing aggregation from occurring, not seen in spin-coating. Two types of organic ligands were found to enhance dispersion of QDs in amine solvents, octadecylamine and mercaptopropionic acid. Utilizing TEM characterization, evidence that electrospray may be more suitable than spin-coating for the dispersion of QDs in solution-derived ChG films was confirmed. However, the ultimate effectiveness of this approach was limited due to the ability to quantify direct loading levels of the QD and surrounding glass matrix. This work demonstrates that electrospray offers additional flexibility over spin-coating and other evaporation methods for the deposition of ChG coatings. Electrospray processing of doped and undoped ChG solutions for microphotonic applications has been shown as a viable alternative in the processing and material toolbox where spatially defined index and dopant control is required.

  9. Enhanced contrast ratio and viewing angle of polymer-stabilized liquid crystal via refractive index matching between liquid crystal and polymer network.

    PubMed

    Lee, Ji-Hoon; Lee, Jung Jin; Lim, Young Jin; Kundu, Sudarshan; Kang, Shin-Woong; Lee, Seung Hee

    2013-11-01

    Long standing electro-optic problems of a polymer-dispersed liquid crystal (PDLC) such as low contrast ratio and transmittances decrease in oblique viewing angle have been challenged with a mixture of dual frequency liquid crystal (DFLC) and reactive mesogen (RM). The DFLC and RM molecules were vertically aligned and then photo-polymerized using a UV light. At scattering state under 50 kHz electric field, DFLC was switched to planar state, giving greater extraordinary refractive index than the normal PDLC cell. Consequently, the scattering intensity and the contrast ratio were increased compared to the conventional PDLC cell. At transparent state under 1 kHz electric field, the extraordinary refractive index of DFLC was simultaneously matched with the refractive index of vertically aligned RM so that the light scattering in oblique viewing angles was minimized, giving rise to high transmittance in all viewing angles.

  10. Enhanced contrast ratio and viewing angle of polymer-stabilized liquid crystal via refractive index matching between liquid crystal and polymer network.

    PubMed

    Lee, Ji-Hoon; Lee, Jung Jin; Lim, Young Jin; Kundu, Sudarshan; Kang, Shin-Woong; Lee, Seung Hee

    2013-11-01

    Long standing electro-optic problems of a polymer-dispersed liquid crystal (PDLC) such as low contrast ratio and transmittances decrease in oblique viewing angle have been challenged with a mixture of dual frequency liquid crystal (DFLC) and reactive mesogen (RM). The DFLC and RM molecules were vertically aligned and then photo-polymerized using a UV light. At scattering state under 50 kHz electric field, DFLC was switched to planar state, giving greater extraordinary refractive index than the normal PDLC cell. Consequently, the scattering intensity and the contrast ratio were increased compared to the conventional PDLC cell. At transparent state under 1 kHz electric field, the extraordinary refractive index of DFLC was simultaneously matched with the refractive index of vertically aligned RM so that the light scattering in oblique viewing angles was minimized, giving rise to high transmittance in all viewing angles. PMID:24216913

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  12. Diffuse light propagation in a turbid medium with varying refractive index: Monte Carlo modeling in a spherically symmetrical geometry.

    PubMed

    Shendeleva, Margarita L; Molloy, John A

    2006-09-20

    We report on the development of Monte Carlo software that can model media with spatially varying scattering coefficient, absorption, and refractive index. The varying refractive index is implemented by calculating curved photon paths in the medium. The results of the numerical simulations are compared with analytical solutions obtained using the diffusion approximation. The model under investigation is a scattering medium that contains a spherically symmetrical inclusion (inhomogeneity) created by variation in optical properties and having no sharp boundaries. The following steady-state cases are considered: (a) a nonabsorbing medium with a spherically symmetrical varying refractive index, (b) an inclusion with varying absorption and scattering coefficients and constant refractive index, and (c) an inclusion with varying absorption, scattering, and refractive index. In the latter case it is shown that the interplay between the absorption coefficient and the refractive index may create the effect of a hidden inclusion.

  13. Negative refractive index, perfect lenses and checkerboards: Trapping and imaging effects in folded optical spaces

    NASA Astrophysics Data System (ADS)

    Guenneau, Sébastien; Ramakrishna, S. Anantha

    2009-06-01

    Newly discovered metamaterials have opened new vistas for better control of light via negative refraction, whereby light refracts in the "wrong" manner. These are dielectric and metallic composite materials structured at subwavelength lengthscales. Their building blocks consist of local resonators such as conducting thin bars and split rings driving the material parameters such as the dielectric permittivity and magnetic permeability to negative (complex) values. Combined together, these structural elements can bring about a (complex valued) negative effective refractive index for the Snell-Descartes law and result in negative refraction of radiation. Negative refractive index materials can support a host of surface plasmon states for both polarizations of light. This makes possible unique effects such as imaging with subwavelength image resolution through the Pendry-Veselago slab lens. Other geometries have also been investigated, such as cylindrical or spherical lenses that enable a magnification of images with subwavelength resolution. Superlenses of three-fold (equilateral triangle), four-fold (square) and six-fold (hexagonal) geometry allow for multiple images, respectively two, three, and five. Generalization to rectangular and triangular checkerboards consisting of alternating cells of positive and negative refractive index represents a very singular situation in which the density of modes diverges at the corners, with an infinity of images. Sine-cosecant anisotropic heterogeneous square and triangular checkerboards can be respectively mapped onto three-dimensional cubic and icosahedral corner lenses consisting of alternating positive and negative refractive regions. All such systems with corners between negative and positive refractive media display very singular behavior with the local density of states becoming infinitely large at the corner, in the limit of no dissipation. We investigate all of these, using the unifying viewpoint of transformation optics

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  15. Perturbation theory for the refractive index mismatch between the inclusion and the surrounding tissues

    NASA Astrophysics Data System (ADS)

    Chai, Chenggang; Liu, Quan

    2016-08-01

    Tissue refractive index is one optical contrast mechanism with diagnostic potential, it is very important to investigate the effect of the refractive index mismatch on light propagation through diffusive regions. Here, we present a new analytical solution of perturbation theory for the refractive index mismatch between the small spherical inclusion and the surrounding tissues. The solution has been used to implement fitting procedures in order to obtain the optical properties of a heterogeneous sphere in semi-infinite medium from measurements of diffuse reflectance. Finally, perturbation theory has been validated by comparisons with the results of Monte Carlo simulation. The new perturbation theory would provide a basis for allowing early disease diagnosis and automatic screening.

  16. A naked eye refractive index sensor with a visible multiple peak metamaterial absorber.

    PubMed

    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

  17. Refractive index measurement based on fiber Bragg grating connected with a multimode fiber core

    NASA Astrophysics Data System (ADS)

    Shao, Min; Qiao, Xueguang; Jiasurname, Zhenan; Fusurname, Haiwei; Liu, Yinggang; Li, Huidong; Zhao, Xue

    2015-09-01

    A novel fiber refractive index sensor based on a fiber-Bragg grating (FBG) connected with a section of multimode fiber core (MMFC) is proposed and demonstrated. The MMFC excites high-order modes to form modal interference, and the core mode reflected by the FBG is sensitive to the surrounding refractive index (SRI) for the power of the core mode within MMFC is dependent on SRI. Measuring the reflective power variation of the core mode could realize the refractive index (RI) detection. Experimental results show that the core mode of FBG has a linear response to RI with enhanced sensitivity of 193.55 dB/RIU in the RI range of 1.3350-1.4042 RIU. The temperature effect of the sensor is also discussed.

  18. Electrically tunable refractive index in the dark conglomerate phase of a bent-core liquid crystal

    NASA Astrophysics Data System (ADS)

    Nagaraj, M.; Görtz, V.; Goodby, J. W.; Gleeson, H. F.

    2014-01-01

    Here we report an electrically tunable refractive index observed in an isotropic liquid crystal phase known as the dark conglomerate (DC) phase. This unusual change in the refractive index which has not been reported before in the DC phase of other bent-core liquid crystals occurs because of a series of electric-field-driven transformations that take place in the DC phase of the studied bent-core liquid crystal. These transformations give rise to a decrease in the refractive index of the system, when an electric field is applied across the device, and no change in the birefringence is seen during such behavior. The electro-optic phenomenon is described in detail and the possibility of exploiting this for a number of liquid crystal based device applications is discussed.

  19. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  20. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-30

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

  1. Printable photonic crystals with high refractive index for applications in visible light.

    PubMed

    Calafiore, Giuseppe; Fillot, Quentin; Dhuey, Scott; Sassolini, Simone; Salvadori, Filippo; Mejia, Camilo A; Munechika, Keiko; Peroz, Christophe; Cabrini, Stefano; Piña-Hernandez, Carlos

    2016-03-18

    Nanoimprint lithography (NIL) of functional high-refractive index materials has proved to be a powerful candidate for the inexpensive manufacturing of high-resolution photonic devices. In this paper, we demonstrate the fabrication of printable photonic crystals (PhCs) with high refractive index working in the visible wavelengths. The PhCs are replicated on a titanium dioxide-based high-refractive index hybrid material by reverse NIL with almost zero shrinkage and high-fidelity reproducibility between mold and printed devices. The optical responses of the imprinted PhCs compare very well with those fabricated by conventional nanofabrication methods. This study opens the road for a low-cost manufacturing of PhCs and other nanophotonic devices for applications in visible light.

  2. 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

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

    PubMed

    Kozacki, Tomasz; Krajewski, Rafal; Kujawińska, Małgorzata

    2009-08-01

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

  4. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    NASA Astrophysics Data System (ADS)

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

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

    SciTech Connect

    Rybaltovsky, A A; Sokolov, V O; Plotnichenko, V G; Lanin, Aleksei V; Semenov, S L; Dianov, Evgenii M; Gur'yanov, A N; Khopin, V F

    2007-04-30

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

  6. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    PubMed Central

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  7. In-line fiber-optic Fabry-Perot refractive-index tip sensors

    NASA Astrophysics Data System (ADS)

    Rao, Yun-Jiang

    2008-10-01

    We propose and demonstrate two novel in-line fiber-optic tip sensors for practical refractive-index (RI) measurement, which are based on an intrinsic Fabry-Perot interferometer (IFPI) formed by a section of conventional single-mode fiber or endlessly single-mode photonic crystal fiber (EPCF), respectively. Such an IFPI sensor has the advantages of easy fabrication, low joint and transmission losses, low-cost and good fringe visibility. Simultaneous measurement of RI and temperature can be realized by determination of the cavity length change and the fringe visibility of such an IFPI, respectively. In addition, it is found that the fringe visibility of the IFPI is insensitive to temperature change, providing a practical way to measure refractive index with self temperature compensation and offers a refractive-index resolution of ~10-5 in its linear operating range. The experimental data agree well with the theoretical results.

  8. Spoof plasmon resonance with 1D periodic grooves for terahertz refractive index sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Yusheng; Hong, Zhi; Han, Zhanghua

    2015-04-01

    We analyze the use of spoof plasmon resonance due to the excitation of spoof surface plasmons in a 1D array of rectangular grooves for terahertz refractive index sensing in an Otto configuration. The dependence of the resonant angle on the change of the refractive index is numerically investigated and a high angular sensitivity about S=320°/RIU is demonstrated, which leads to a high resolution of 3×10-7 RIU assuming 1×10-4 degree for angular resolution. We further show that by using a slanted geometry an even higher sensitivity up to 452°/RIU can be achieved. These results provide a novel method for terahertz refractive index sensing.

  9. 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.

  10. Estimating index of refraction for material identification in comparison to existing temperature emissivity separation algorithms

    NASA Astrophysics Data System (ADS)

    Martin, Jacob A.; Gross, Kevin C.

    2016-05-01

    As off-nadir viewing platforms become increasingly prevalent in remote sensing, material identification techniques must be robust to changing viewing geometries. Current identification strategies generally rely on estimating reflectivity or emissivity, both of which vary with viewing angle. Presented here is a technique, leveraging polarimetric and hyperspectral imaging (P-HSI), to estimate index of refraction which is invariant to viewing geometry. Results from a quartz window show that index of refraction can be retrieved to within 0.08 rms error from 875-1250 cm-1 for an amorphous material. Results from a silicon carbide (SiC) wafer, which has much sharper features than quartz glass, show the index of refraction can be retrieved to within 0.07 rms error. The results from each of these datasets show an improvement when compared with a maximum smoothness TES algorithm.

  11. Refractive index measurement of the mouse crystalline lens using optical coherence tomography.

    PubMed

    Chakraborty, Ranjay; Lacy, Kip D; Tan, Christopher C; Park, Han Na; Pardue, Machelle T

    2014-08-01

    In recent years, there has been a growing interest for using mouse models in refractive development and myopia research. The crystalline lens is a critical optical component of the mouse eye that occupies greater than 50% of the ocular space, and significant increases in thickness with age. However, changes in refractive index of the mouse crystalline lens are less known. In this study, we examined the changes in thickness and refractive index of the mouse crystalline lens for two different strains, wild-type (WT) and a nyx mutant (nob) over the course of normal visual development or after form deprivation. Refractive index and lens thickness measurements were made on ex vivo lenses using spectral domain optical coherence tomography (SD-OCT). Comparison of refractive index measurements on 5 standard ball lenses using the SD-OCT and their known refractive indices (manufacturer provided) indicated good precision (intra-class correlation coefficient, 0.998 and Bland-Altman coefficient of repeatability, 0.116) of the SD-OCT to calculate mouse lens refractive index ex vivo. During normal visual development, lens thickness increased significantly with age for three different cohorts of mice, aged 4 (average thickness from both eyes; WT: 1.78 ± 0.03, nob: 1.79 ± 0.08 mm), 10 (WT: 2.02 ± 0.05, nob: 2.01 ± 0.04 mm) and 16 weeks (WT: 2.12 ± 0.06, nob: 2.09 ± 0.06 mm, p < 0.001). Lens thickness was not significantly different between the two strains at any age (p = 0.557). For mice with normal vision, refractive index for isolated crystalline lenses in nob mice was significantly greater than WT mice (mean for all ages; WT: 1.42 ± 0.01, nob: 1.44 ± 0.001, p < 0.001). After 4 weeks of form deprivation to the right eye using a skull-mounted goggling apparatus, a thinning of the crystalline lens was observed in both right and left eyes of goggled animals compared to their naïve controls (average from both the right and the left eye) for both

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

    PubMed

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

    2012-08-23

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

  13. Atmospheric refraction: Applied image analysis and experimental example for index profile with curvature

    NASA Astrophysics Data System (ADS)

    Short, Daniel; Voelz, David; Barraza, Jose; Dragulin, Ivan

    2016-05-01

    In this work we consider atmospheric refractive bending and its effects on long-range imaging along a horizontal path. Refraction can impact the ability of a remote sensing or image system to accurately locate objects and determine their apparent proportions. We use a low-cost commercial camera operating in a time-lapse mode for refraction studies and have been recording images of a building that is 15.3 km west of the camera. Based on the paraxial ray equation, a solution for ray height and angle is obtained for a refractive index profile with curvature. A curved index profile can produce the effects of towering (stretching) and stooping (compression). The curvature parameter for the average atmospheric index profile between the camera and target can be derived from an analysis of the images collected by the camera system. We show example images where the building (33 m height) appears to stretch by 5.1 m and calculate a refractive index curvature parameter of 6.0x10-5 m-2.

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

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

  15. Full-field measurement of surface reflectivity using a microscopy for refractive index profiling of GRIN lenses

    NASA Astrophysics Data System (ADS)

    Weng, Chun-Jen; Chen, Chih-Yen; Hwang, Chi-Hung; Liu, Da-Ren

    2016-07-01

    This paper outlines an improved technique for profiling the refractive index of Graded-index (GRIN) lenses based on the measurements obtained from a reflectivity image. Reflective cross-sectional image of the GRIN lens were compared with a reflectance reference target under illumination at small incidence angles to obtain the full-field refractive index distribution of the GRIN lens quickly and easily.

  16. Retrieval of refractive index fields in two-dimensional gradient-index elements from external deflectometry data.

    PubMed

    Lin, Di; Leger, James R

    2016-03-01

    In a previous work, we presented a numerical method for retrieving inhomogeneous refractive index fields in rectangular gradient-index elements from boundary positions and internal boundary slopes associated with a set of interrogating probe beams that transit the medium. The present work extends this method to external boundary beam slopes without knowledge of the refractive index along the surface of the optical element, requiring minimal additional information (outside of beam position and slope data) such as a single known index point inside the medium. The inverse problem is cast as a linear algebraic system describing the deflection of probe beams inside the optical material, and an iterative inversion algorithm is used to generate an index field that produces the boundary value data. By incorporating Snell's law into the system equation through surface values derived from tentative reconstructions of the refractive index, we show in simulation that a series of inversion cycles applied to the system equation accurately recovers the index profile used to generate the test data.

  17. Compositional dependence of optical band gap and refractive index in lead and bismuth borate glasses

    SciTech Connect

    Mallur, Saisudha B.; Czarnecki, Tyler; Adhikari, Ashish; Babu, Panakkattu K.

    2015-08-15

    Highlights: • Refractive indices increase with increasing PbO/Bi{sub 2}O{sub 3} content. • Optical band gap arises due to direct forbidden transition. • Optical band gaps decrease with increasing PbO/Bi{sub 2}O{sub 3} content. • New empirical relation between the optical band gap and the refractive index. - Abstract: We prepared a series of lead and bismuth borate glasses by varying PbO/Bi{sub 2}O{sub 3} content and studied refractive index and optical band gap as a function of glass composition. Refractive indices were measured very accurately using a Brewster’s angle set up while the optical band gaps were determined by analyzing the optical absorption edge using the Mott–Davis model. Using the Lorentz–Lorentz method and the effective medium theory, we calculated the refractive indices and then compared them with the measured values. Bismuth borate glasses show better agreement between the calculated values of the refractive index and experimental values. We used a differential method based on Mott–Davis model to obtain the type of transition and optical band gap (E{sub opt}) which in turn was compared with the value of E{sub opt} obtained using the extinction coefficient. Our analysis shows that in both lead and bismuth borate glasses, the optical band gap arises due to direct forbidden transition. With increasing PbO/Bi{sub 2}O{sub 3} content, the absorption edge shifts toward longer wavelengths and the optical band gap decreases. This behavior can be explained in terms of changes to the Pb−O/Bi−O chemical bonds with glass composition. We obtained a new empirical relation between the optical band gap and the refractive index which can be used to accurately determine the electronic oxide polarizability in lead and bismuth oxide glasses.

  18. Physicochemical and catalytic properties of Au nanorods micro-assembled in solvents of varying dipole moment and refractive index

    SciTech Connect

    Kaur, Rupinder; Pal, Bonamali

    2015-02-15

    Highlights: • Physicochemical activities of Au nanorods in water largely differ from organic solvents. • Au nanorods agglomeration increased with dipole moments of different polar solvents. • Refractive indexes of Au nanorods dispersion in various polar solvents are enhanced. • Electrokinetics significantly altered depending on agglomerated size of Au nanorods. • Catalysis or co-catalysis activity is varied as per the extent of Au nanorods coagulation. - Abstract: This paper deals with the impact of dipole moment (1.66–3.96 D) and refractive index (1.333–1.422) of the dispersion solvent on the plasmon absorption, surface charge, zeta potential, and adsorption properties of Au nanorods (AuNRs). AuNRs (length ≈ 53 nm and width ≈ 20 nm) undergo agglomeration (size 50–180 nm) with increase in the dipole moment of solvent (iPrOH < MeOH < DMF < DMSO). Whereas, no such coagulation occurs in H{sub 2}O and CCl{sub 4} suspension as confirmed by DLS and TEM size distribution. The electrostatic interaction of AuNRs with its surface adsorbed solvent dipoles leads to alteration of the their ionic state, absolute electronic charge and zeta potential (+49.79 mV in H{sub 2}O, +8.99 mV in DMF and −4.65 mV in MeOH dispersion) to a greater extent. This interaction distinctly modifies the adsorption behavior of polar molecules like p-nitrophenol and salicylic acid on AuNRs surface, as evidenced by the measured changes in their electro-kinetic parameters. As a result, we observe a substantial difference in catalytic and co-catalytic activities of AuNRs dispersed in various solvents as mentioned above because the catalytic properties of AuNRs are strongly dependent on the type of solvent in which they are dispersed.

  19. Multilayered optical memory with bits stored as refractive index change. I. Electromagnetic theory.

    PubMed

    Guo, Hanming; Zhuang, Songlin; Chen, Jiabi; Liang, Zhongcheng

    2007-06-01

    With the Lippman-Schwinger equation, dyadic Green's functions, and the vector coherent transfer function method, an electromagnetic theory of a waveguide multilayered optical memory is first developed for the static case, from which a theory describing a conventional multilayered optical memory with bits stored as a refractive index change is also derived. In addition, the formulas for readout signals and cross talk are given, and some problems of numerical calculations are discussed. The theories can be used effectively for optimum design of a multilayered optical memory with bits stored as a refractive index change.

  20. 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.

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

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1992-01-01

    The index of refraction can considerably influence the temperature distribution and radiative heat flow in semitransparent materials such as some ceramics. For external radiant heating, the refractive index influences the amount of energy transmitted into the interior of the material. Emission within a material depends on the square of its refractive index, and hence this emission can be many times that for a biackbody radiating into a vacuum. Since radiation exiting through an interface into a vacuum cannot exceed that of a blackbody, there is extensive reflection at the internal surface of an interface, mostly by total internal reflection. This redistributes energy within the layer and tends to make its temperature distribution more uniform. The purpose of the present analysis is to show that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained very simply from the results for an index of refraction of unity. For the situation studied here, the layer is subjected to external radiative heating incident on each of its surfaces. The material emits, absorbs, and isotropically scatters radiation. For simplicity the index of refraction is unity in the medium surrounding the layer. The surfaces of the layer are assumed diffuse. This is probably a reasonable approximation for a ceramic layer that has not been polished. When transmitted radiation or radiation emitted from the interior reaches the inner surface of an interface, the radiation is diffused and some of it thereby placed into angular directions for which there is total internal reflection. This provides a trapping effect for retaining energy within the layer and tends to equalize its temperature distribution. An analysis of temperature distributions in absorbing-emitting layers, including index of refraction effects, was developed by Gardon (1958) to predict cooling and heat treating of glass plates

  2. Seasonal and geographic variations in imaginary refractive index of atmospheric particulate matter.

    PubMed

    Gillespie, J B; Lindberg, J D

    1992-04-20

    Samples of atmospheric particulate matter were collected on cellulose membrane filters at selected locations in Europe during 1976 and 1977 as part of an international cooperative atmospheric characterization program. These samples are analyzed for imaginary refractive index in the 0.3-1.7-microm spectral region. These data are used to determine the range of variability of the imaginary refractive index and are examined for seasonal variations. These data are discussed in the light of results of analysis of samples collected from other parts of the world and samples that were analyzed as a function of particle size.

  3. In situ measurement of group refractive index using tandem low-coherence interferometer

    NASA Astrophysics Data System (ADS)

    Matsumoto, H.; Sasaki, K.; Hirai, A.

    2006-10-01

    The group refractive index of BK-7 glass material is accurately measured using a tandem low-coherence interferometer, which is composed of a Mychelson interferometer and a Fizeau interferometer, within a combined standard uncertainty of 8.4 ppm. The experimental results are compared with the value calculated from the conventional data base on the phase refractive index, within a difference of about 4.7 ppm. This new method is applicable to in situ measurement due to the principle of its common optical path.

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

    NASA Astrophysics Data System (ADS)

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

    1998-03-01

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

  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

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

    SciTech Connect

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

    2001-06-18

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

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

    PubMed

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

    2010-09-27

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

  8. Time-resolved measurement of the refractive index for photopolymerization processes

    NASA Astrophysics Data System (ADS)

    Dorkenoo, Kokou; van Wonderen, A. J.; Bulou, Hervé; Romeo, Michelangelo; Crégut, Olivier; Fort, Alain

    2003-09-01

    A double-interferometer technique is employed to examine the dynamics of a photopolymerization process. The dye molecule is eosine Y. The refractive index and the thickness of the photopolymerizable film are measured as a function of time. During the photopolymerization process, the first quantity increases by 2%, while the second quantity decreases by more than 4%. Therefore, the refractive index cannot be measured by means of single-interferometer techniques. By fitting our experimental curves to a rate equation, the quantum yield and the absorption coefficient of the sample can be determined with good accuracy.

  9. 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.

  10. Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

    SciTech Connect

    Vargas, Mirella; Murphy, N. R.; Ramana, C. V.

    2014-03-10

    Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s} = 25–700 °C). HfO{sub 2} films grown at T{sub s} < 200 °C were amorphous, while those grown at T{sub s} ≥ 200 °C were monoclinic, nanocrystalline with (1{sup ¯}11) texturing. X-ray reflectivity (XRR) analyses indicate that the film-density (ρ) increases with increasing T{sub s}. The index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (λ)} = 550 nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-ρ-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and the microstructure of HfO{sub 2} films.

  11. Methods for estimating the refractive index profile at near infrared wavelengths of polymers for optical waveguides

    NASA Astrophysics Data System (ADS)

    Guenthner, Andrew J.; Lindsay, Geoffrey A.; Zarras, Peter; Fallis, Stephen; Pentony, Joni M.; Herman, Warren N.

    2002-12-01

    Methods that successfully predict the refractive index at near-infrared wavelengths of negatively birefringent polymer films for optical waveguide applications are presented. The starting point for these methods is a correlation based on connectivity indexes originally developed by Bicerano for the refractive index of isotropic polymers at visible wavelengths. This correlation is applied to a set of polyimides at near infrared wavelengths with modifications in order to improve its predictive power. The polyimides were synthesized by condensation of monomers to form the precursor poly(amic acid)s followed by imidization in solution. Solutions of the polyimides were then spin coated onto glass substrates and baked to produce films of 2-3 microns in thickness with a variable negative birefringence. The refractive index profiles of these films near 1320 nm were then measured in both the TE- and TM- modes using a prism-coupling technique. The average refractive index of these films was then compared to the prediction generated by the model. The agreement between the predicted and observed values has been sufficient to enable the rapid development of materials for optical waveguides without the need for many rounds of trial-and-error investigation. These techniques facilitate the development of specialized polymers for optical waveguide applications.

  12. Single-mode optical waveguides on native high-refractive-index substrates

    NASA Astrophysics Data System (ADS)

    Grote, Richard R.; Bassett, Lee C.

    2016-10-01

    High-refractive-index semiconductor optical waveguides form the basis for modern photonic integrated circuits (PICs). However, conventional methods for achieving optical confinement require a thick lower-refractive-index support layer that impedes large-scale co-integration with electronics and limits the materials on which PICs can be fabricated. To address this challenge, we present a general architecture for single-mode waveguides that confine light in a high-refractive-index material on a native substrate. The waveguide consists of a high-aspect-ratio fin of the guiding material surrounded by lower-refractive-index dielectrics and is compatible with standard top-down fabrication techniques. This letter describes a physically intuitive, semi-analytical, effective index model for designing fin waveguides, which is confirmed with fully vectorial numerical simulations. Design examples are presented for diamond and silicon at visible and telecommunications wavelengths, respectively, along with calculations of propagation loss due to bending, scattering, and substrate leakage. Potential methods of fabrication are also discussed. The proposed waveguide geometry allows PICs to be fabricated alongside silicon CMOS electronics on the same wafer, removes the need for heteroepitaxy in III-V PICs, and will enable wafer-scale photonic integration on emerging material platforms such as diamond and SiC.

  13. Length and refractive index measurement by Fourier transform interferometry and frequency comb spectroscopy

    NASA Astrophysics Data System (ADS)

    Balling, Petr; Mašika, Pavel; Křen, 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.

  14. Band structure and reflectivity of omnidirectional Si-based mirrors with a Gaussian profile refractive index

    NASA Astrophysics Data System (ADS)

    Arriaga, J.; Saldaña, X. I.

    2006-08-01

    Using the transfer matrix method we calculate the band structure for a one-dimensional photonic crystal consisting of alternating layers of two dielectric materials A and B with refractive indices nA and nB, respectively. The refractive index of layer A is constant and the refractive index for layer B varies according to the envelope of a Gaussian function. We find that under certain circumstances it is possible to obtain a 100% reflectivity for both polarizations (TE and TM) and any value of the incident angle of the electromagnetic waves. The interval of maximum reflectivity coincides with the photonic band gap of the structure. By an adequate selection of the parameters forming the structure, it is possible to tune the interval of frequencies with maximum reflectivity. This could be used in the fabrication of the so-called omnidirectional mirrors.

  15. Internal characteristics of refractive-index matched debris flows

    NASA Astrophysics Data System (ADS)

    Gollin, Devis; Bowman, Elisabeth; Sanvitale, Nicoletta

    2016-04-01

    Debris flows are channelized masses of granular material saturated with water that travel at high speeds downslope. Their destructive character represents a hazard to lives and properties, especially in regions of high relief and runoff. The characteristics that distinguish their heterogeneous, multi-phase, nature are numerous: non-uniform surge formation, particle size ranging from clay to boulders, flow segregation with larger particles concentrating at the flow front and fluid at the tail making the composition and volume of the bulk varying with time and space. These aspects render these events very difficult to characterise and predict, in particular in the area of the deposit spread or runout - zones which are generally of most interest in terms of human risk. At present, considerable gaps exist in our understanding of the flow dynamics of debris flows, which originates from their complex motion and relatively poor observations available. Flume studies offer the potential to examine in detail the behaviour of model debris flows, however, the opaque nature of these flows is a major obstacle in gaining insight of their internal behaviour. Measurements taken at the sidewalls may be poorly representative leading to incomplete or misleading results. To probe internally to the bulk of the flow, alternative, nonintrusive techniques can be used, enabling, for instance, velocities and solid concentrations within the flowing material to be determined. We present experimental investigations into polydisperse granular flows of spherical immersed particles down an inclined flume, with specific attention directed to their internal behavior. To this end, the refractive indices of solids and liquid are closely matched allowing the two phases to be distinguished. Measurements are then made internally at a point in the channel via Plane Laser Induced Fluorescence, Particle Tracking Velocimetry, PTV and Particle Image Velocimetry, PIV. The objective is to to increase our

  16. Refractive index and solubility control of para-cymene solutions for index-matched fluid-structure interaction studies

    NASA Astrophysics Data System (ADS)

    Fort, Charles; Fu, Christopher D.; Weichselbaum, Noah A.; Bardet, Philippe M.

    2015-12-01

    To deploy optical diagnostics such as particle image velocimetry or planar laser-induced fluorescence (PLIF) in complex geometries, it is beneficial to use index-matched facilities. A binary mixture of para-cymene and cinnamaldehyde provides a viable option for matching the refractive index of acrylic, a common material for scaled models and test sections. This fluid is particularly appropriate for large-scale facilities and when a low-density and low-viscosity fluid is sought, such as in fluid-structure interaction studies. This binary solution has relatively low kinematic viscosity and density; its use enables the experimentalist to select operating temperature and to increase fluorescence signal in PLIF experiments. Measurements of spectral and temperature dependence of refractive index, density, and kinematic viscosity are reported. The effect of the binary mixture on solubility control of Rhodamine 6G is also characterized.

  17. 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

  18. Laplace-Gauss and Helmholtz-Gauss paraxial modes in media with quadratic refraction index.

    PubMed

    Kiselev, Aleksei P; Plachenov, Alexandr B

    2016-04-01

    The scalar theory of paraxial wave propagation in an axisymmetric medium where the refraction index quadratically depends on transverse variables is addressed. Exact solutions of the corresponding parabolic equation are presented, generalizing the Laplace-Gauss and Helmholtz-Gauss modes earlier known for homogeneous media. Also, a generalization of a zero-order asymmetric Bessel-Gauss beam is given.

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

    DOEpatents

    Faulstich, Marga; Jahn, Walter; Krolla, Georg; Neuroth, Norbert

    1980-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

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

    SciTech Connect

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

    2010-08-23

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  3. Antireflection nanocomposite thick film coatings with quasi-zero refractive index for solar cells

    NASA Astrophysics Data System (ADS)

    Gadomsky, O. N.; Shchukarev, I. A.; Pereskokov, E. A.

    2016-08-01

    Application of nanostructured composite coatings with a quasi-zero refractive index synthesized using the proposed patented technology provides a 25-30% increase in the efficiency of solar cells as compared to that of analogous solar cells with traditional (e.g., silicon nitride) single-layer interference antireflection coating.

  4. Variable Refractive Index Effects on Radiation in Semitransparent Scattering Multilayered Regions

    NASA Technical Reports Server (NTRS)

    Siegel, R.; Spuckler, C. M.

    1993-01-01

    A simple set of equations is derived for predicting the temperature distribution and radiative energy flow in a semitransparent layer consisting of an arbitrary number of laminated sublayers that absorb, emit, and scatter radiation. Each sublayer can have a different refractive index and optical thickness. The plane composite region is heated on each exterior side by a different amount of incident radiation. The results are for the limiting case where heat conduction within the layers is very small relative to radiative transfer, and is neglected. The interfaces are assumed diffuse, and all interface reflections are included in the analysis. The thermal behavior is readily calculated from the analytical expressions that are obtained. By using many sublayers, the analytical expressions provide the temperature distribution and heat flow for a diffusing medium with a continuously varying refractive index, including internal reflection effects caused by refractive index gradients. Temperature and heat flux results are given to show the effect of variations in refractive index and optical thickness through the multilayer laminate.

  5. Integrating Whispering Gallery Mode Refractive Index Sensing with Capillary Electrophoresis Separations Using Phase Sensitive Detection.

    PubMed

    Kim, Daniel C; Dunn, Robert C

    2016-01-19

    Whispering gallery mode (WGM) resonators are small, radially symmetric dielectrics that recirculate light through continuous total internal reflection. High-Q resonances are observed that shift in response to changes in surrounding refractive index, leading to many applications in label-free sensing. Surface binding measurements with WGM resonators have demonstrated competitive analytical detection metrics compared to other sensing schemes. Similar figures of merit for detecting bulk refractive index changes, however, have proven more challenging. This has limited their use in applications such as capillary electrophoresis (CE), where their compact footprint and refractive index sensitivity offers advantages in nondestructive, universal detection. Here we couple WGM detection with CE by introducing a modulation scheme to improve detection limits. Phase sensitive WGM (PS-WGM) detection is developed to monitor real-time shifts in the WGM spectrum due to changes in surrounding refractive index. We directly compare phase sensitive detection with spectral measurements normally used to track WGM shifts. We report an improvement in detection limits by almost 300-fold using the PS-WGM method. The integrated CE with PS-WGM approach is demonstrated by detecting the separation of a three-component mixture of cations (Na(+), Li(+), and K(+)).

  6. Single tapered fiber tip for simultaneous measurements of thickness, refractive index and distance to a sample.

    PubMed

    Moreno-Hernández, Carlos; Monzón-Hernández, David; Hernández-Romano, Iván; Villatoro, Joel

    2015-08-24

    We demonstrate the capability of an air cavity Fabry-Perot interferometer (FPI), built with a tapered lead-in fiber tip, to measure three parameters simultaneously, distance, group refractive index and thickness of transparent samples introduced in the cavity. Tapering the lead-in fiber enhances the light coupling back efficiency, therefore is possible to enlarge the air cavity without a significant deterioration of the fringe visibility. Fourier transformation, used to analyze the reflected optical spectrum of our FPI, simplify the calculus to determine the position, thickness and refractive index. Samples made of 7 different glasses; fused silica, BK7, BalF5, SF2, BaF51, SF15, and glass slides were used to test our FPI. Each sample was measured nine times and the results for position, thickness and refractive index showed differences of ± 0.7%, ± 0.1%, and ± 0.16% respectively. The evolution of thickness and refractive index of a block of polydimethylsiloxane (PDMS) elastomer due to temperature changes in the range of 25°C to 90°C were also measured. The coefficients of the thermal expansion and thermo-optic estimated were α = 4.71x10(-4)/°C and dn/dT = -4.66 x10(-4) RIU/°C, respectively.

  7. Ultraviolet and visible imaginary refractive index of strongly absorbing atmospheric particulate matter.

    PubMed

    Gillespie, J B; Lindberg, J D

    1992-04-20

    Determinations of the imaginary refractive index in the ultraviolet and visible spectral regions as determined from diffuse reflectance measurements are presented. Materials examined are carbon black and oxides of iron, lead, mercury, copper, manganese, and vanadium along with lead iodide and iron sulfide.

  8. Single scattering albedo, asymmetry parameter, apparent refractive index, and apparent soot content of dry atmospheric particles.

    PubMed

    Hänel, G

    1988-06-01

    Mean shortwave values of the single scattering albedo and the asymmetry parameter of dry atmospheric particles have been measured photometrically. From the single scattering albedo the mean shortwave value of the apparent complex refractive index and the apparent volume fraction of soot within the particulate matter are derived. From 275 measurements the mean value of the single scattering albedo is 0.835, the mean value of the apparent complex refractive index is 1.51-0.026i, and the mean value of the apparent volume fraction of soot is 5.8%. For seventy-seven cases of mostly urban particles the mean value of the asymmetry parameter is 0.39. The term apparent stands for appearing (but not necessarily) real or true. Reasons for this attribute are the idealizations necessary to get a value of the refractive index of atmospheric particles. Consequently the use of an apparent refractive index for modeling purposes is restricted as described in the concluding section.

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

    PubMed

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

    2011-04-01

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

  10. The refractive index of krypton for lambda in the closed interval 168-288 nm

    NASA Technical Reports Server (NTRS)

    Smith, P. L.; Parkinson, W. H.; Huber, M. C. E.

    1975-01-01

    The index of refraction of krypton has been measured at 27 wavelengths between and including 168 and 288 nm. The probable error of each measurement is plus or minus 0.1%. Our results are compared with other measurements. Our data are about 3.8% smaller than those of Abjean et al.

  11. Single tapered fiber tip for simultaneous measurements of thickness, refractive index and distance to a sample.

    PubMed

    Moreno-Hernández, Carlos; Monzón-Hernández, David; Hernández-Romano, Iván; Villatoro, Joel

    2015-08-24

    We demonstrate the capability of an air cavity Fabry-Perot interferometer (FPI), built with a tapered lead-in fiber tip, to measure three parameters simultaneously, distance, group refractive index and thickness of transparent samples introduced in the cavity. Tapering the lead-in fiber enhances the light coupling back efficiency, therefore is possible to enlarge the air cavity without a significant deterioration of the fringe visibility. Fourier transformation, used to analyze the reflected optical spectrum of our FPI, simplify the calculus to determine the position, thickness and refractive index. Samples made of 7 different glasses; fused silica, BK7, BalF5, SF2, BaF51, SF15, and glass slides were used to test our FPI. Each sample was measured nine times and the results for position, thickness and refractive index showed differences of ± 0.7%, ± 0.1%, and ± 0.16% respectively. The evolution of thickness and refractive index of a block of polydimethylsiloxane (PDMS) elastomer due to temperature changes in the range of 25°C to 90°C were also measured. The coefficients of the thermal expansion and thermo-optic estimated were α = 4.71x10(-4)/°C and dn/dT = -4.66 x10(-4) RIU/°C, respectively. PMID:26368188

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

    NASA Technical Reports Server (NTRS)

    Rubinstein, R.; Greenberg, P. S.

    1994-01-01

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

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

    SciTech Connect

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

    2011-11-01

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

  14. Surface Wave Cloak from Graded Refractive Index Nanocomposites

    PubMed Central

    La Spada, L.; McManus, T. M.; Dyke, A.; Haq, S.; Zhang, L.; Cheng, Q.; Hao, Y.

    2016-01-01

    Recently, a great deal of interest has been re-emerged on the possibility to manipulate surface waves, in particular, towards the THz and optical regime. Both concepts of Transformation Optics (TO) and metamaterials have been regarded as one of key enablers for such applications in applied electromagnetics. In this paper, we experimentally demonstrate for the first time a dielectric surface wave cloak from engineered gradient index materials to illustrate the possibility of using nanocomposites to control surface wave propagation through advanced additive manufacturing. The device is designed analytically and validated through numerical simulations and measurements, showing good agreement and performance as an effective surface wave cloak. The underlying design approach has much wider applications, which span from microwave to optics for the control of surface plasmon polaritons (SPPs) and radiation of nanoantennas. PMID:27416815

  15. Surface Wave Cloak from Graded Refractive Index Nanocomposites

    NASA Astrophysics Data System (ADS)

    La Spada, L.; McManus, T. M.; Dyke, A.; Haq, S.; Zhang, L.; Cheng, Q.; Hao, Y.

    2016-07-01

    Recently, a great deal of interest has been re-emerged on the possibility to manipulate surface waves, in particular, towards the THz and optical regime. Both concepts of Transformation Optics (TO) and metamaterials have been regarded as one of key enablers for such applications in applied electromagnetics. In this paper, we experimentally demonstrate for the first time a dielectric surface wave cloak from engineered gradient index materials to illustrate the possibility of using nanocomposites to control surface wave propagation through advanced additive manufacturing. The device is designed analytically and validated through numerical simulations and measurements, showing good agreement and performance as an effective surface wave cloak. The underlying design approach has much wider applications, which span from microwave to optics for the control of surface plasmon polaritons (SPPs) and radiation of nanoantennas.

  16. Surface Wave Cloak from Graded Refractive Index Nanocomposites.

    PubMed

    La Spada, L; McManus, T M; Dyke, A; Haq, S; Zhang, L; Cheng, Q; Hao, Y

    2016-01-01

    Recently, a great deal of interest has been re-emerged on the possibility to manipulate surface waves, in particular, towards the THz and optical regime. Both concepts of Transformation Optics (TO) and metamaterials have been regarded as one of key enablers for such applications in applied electromagnetics. In this paper, we experimentally demonstrate for the first time a dielectric surface wave cloak from engineered gradient index materials to illustrate the possibility of using nanocomposites to control surface wave propagation through advanced additive manufacturing. The device is designed analytically and validated through numerical simulations and measurements, showing good agreement and performance as an effective surface wave cloak. The underlying design approach has much wider applications, which span from microwave to optics for the control of surface plasmon polaritons (SPPs) and radiation of nanoantennas. PMID:27416815

  17. Analysis of Refractive Index Distributions in Cylindrical, Graded-Index Glass Rods (GRIN Rods) Used as Image Relays.

    PubMed

    Rawson, E G; Herriott, D R; McKenna, J

    1970-03-01

    Cylindrical transparent media whose refractive index decreases with increasing cylinder radius have been investigated in connection with coherent light propagation in gas waveguides. Recently, graded index glass rods (trade named SELFOC rods) have been used as imaging devices. We report here on a geometrical optical study of graded index systems used for relaying images at unit magnification. We have found that two index distributions previously studied result in large image aberrations when the presence of skew rays is taken into account. We have derived an index distribution which is "ideal" for helical skew rays. Using ray tracing methods we have examined image aberrations for various index distributions and for various rod geometries. We find that (1) no one refractive index distribution can be "ideal" for both meridional and skew rays, (2) image resolution is generally low, reaching about 1000 spots per field, and (3) the optimal index distribution varies with the ratio of rod length to radius and the relative aperture and is intermediate between the helically ideal and the meridionally ideal distributions. PMID:20076273

  18. Monitoring of high refractive index edible oils using coated long period fiber grating sensors

    NASA Astrophysics Data System (ADS)

    Coelho, Luís.; Viegas, Diana; Santos, José Luís.; de Almeida, Jose Manuel M. M.

    2015-05-01

    Monitoring the quality of high refractive index edible oils is of great importance for the human health. Uncooked edible oils in general are healthy foodstuff, olive oil in particular, however, they are frequently used for baking and cooking. High quality edible oils are made from seeds, nuts or fruits by mechanical processes. Nevertheless, once the mechanical extraction is complete, up to 15% of the oil remains in oil pomace and in the mill wastewater, which can be extracted using organic solvents, often hexane. Optical fiber sensors based on long period fiber gratings (LPFG) have very low wavelength sensitivity when the surround refractive index is higher than the refractive index of the cladding. Titanium dioxide (TiO2) coated LPFG could lead to the realization of high sensitivity chemical sensor for the food industry. In this work LPFG coated with a TiO2 thin film were successfully used for to detect small levels of hexane diluted in edible oils and for real time monitoring the thermal deterioration of edible oils. For a TiO2 coating of 30 nm a wavelength sensitivity of 1361.7 nm/RIU (or 0.97 nm / % V/V) in the 1.4610-1.4670 refractive index range was achieved, corresponding to 0 to 12 % V/V of hexane in olive oil. A sensitivity higher than 638 nm/RIU at 225 ºC was calculated, in the 1.4670-1.4735 refractive index range with a detection limit of thermal deterioration of about 1 minute.

  19. Optimization of torque on an optically driven micromotor by manipulation of the index of refraction

    NASA Astrophysics Data System (ADS)

    Wing, Frank M., III; Mahajan, Satish; Collett, Walter

    2004-12-01

    Since the 1970"s, the focused laser beam has become a familiar tool to manipulate neutral, dielectric micro-objects. A number of authors, including Higurashi and Gauthier, have described the effects of radiation pressure from laser light on microrotors. Collett, et al. developed a wave, rather than a ray optic, approach in the calculation of such forces on a microrotor for the first time. This paper describes a modification to the design of a laser driven, radiation pressure microrotor, intended to improve the optically generated torque. Employing the wave approach, the electric and magnetic fields in the vicinity of the rotor are calculated using the finite difference time domain (FDTD) method, which takes into account the wave nature of the incident light. Forces are calculated from the application of Maxwell"s stress tensor over the surfaces of the rotor. Results indicate a significant increase in torque when the index of refraction of the microrotor is changed from a single value to an inhomogeneous profile. The optical fiber industry has successfully employed a variation in the index of refraction across the cross section of a fiber for the purpose of increasing the efficiency of light transmission. Therefore, it is hoped that various fabrication methods can be utilized for causing desired changes in the index of refraction of an optically driven microrotor. Various profiles of the index of refraction inside a microrotor are considered for optimization of torque. Simulation methodology and results of torque on a microrotor for various profiles of the index of refraction are presented. Guidelines for improvised fabrication of efficient microrotors may then be obtained from these profiles.

  20. Investigation of the nonlinear refractive index of single-crystalline thin gold films and plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Goetz, Sebastian; Razinskas, Gary; Krauss, Enno; Dreher, Christian; Wurdack, Matthias; Geisler, Peter; Pawłowska, Monika; Hecht, Bert; Brixner, Tobias

    2016-04-01

    The nonlinear refractive index of plasmonic materials may be used to obtain nonlinear functionality, e.g., power-dependent switching. Here, we investigate the nonlinear refractive index of single-crystalline gold in thin layers and nanostructures on dielectric substrates. In a first step, we implement a z-scan setup to investigate ~100-µm-sized thin-film samples. We determine the nonlinear refractive index of fused silica, n 2(SiO2) = 2.9 × 10-20 m2/W, in agreement with literature values. Subsequent z-scan measurements of single-crystalline gold films reveal a damage threshold of 0.22 TW/cm2 and approximate upper limits of the real and imaginary parts of the nonlinear refractive index, | n 2'(Au)| < 1.2 × 10-16 m2/W and | n 2″(Au)| < 0.6 × 10-16 m2/W, respectively. To further determine possible effects of a nonlinear refractive index in plasmonic circuitry, interferometry is proposed as a phase-sensitive probe. In corresponding nanostructures, relative phase changes between two propagating near-field modes are converted to amplitude changes by mode interference. Power-dependent experiments using sub-10-fs near-infrared pulses and diffraction-limited resolution (NA = 1.4) reveal linear behavior up to the damage threshold (0.23 times relative to that of a solid single-crystalline gold film). An upper limit for the nonlinear power-dependent phase change between two propagating near-field modes is determined to Δ φ < 0.07 rad.

  1. Determination of the refractive index difference caused by the birefringence of FA (II) centers in KCl:Li

    NASA Astrophysics Data System (ADS)

    Silfsten, Pertti; Ketolainen, Pertti

    1991-11-01

    A method is described for determining the refractive index difference caused by the birefringence of oriented FA (II) centers in KCl:Li crystals. It is shown that the portion induced by the birefringence can be separated from an absorption spectrum measured through a polarizer-analyzer system. From this portion the refractive index difference can then be calculated with ease.

  2. Refractive index sensitivity of long-period fiber gratings written in thinned cladding fiber by CO2 laser

    NASA Astrophysics Data System (ADS)

    Zhao, Yunhe; Liu, Yunqi; Guo, Qiang; Wang, Tingyun

    2014-05-01

    We demonstrate the fabrication of the long-period fiber gratings (LPFGs) in the thinned cladding fiber (TCF) using CO2 laser. The sensing response of the gratings to surrounding refractive index has been investigated experimentally. The LPFGs written in the TCF could be used as the high sensitive refractive index sensors.

  3. The Effect of the Refractive Index of the Medium in Fluorescence Correlation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cha, Seoncheol; Kim, Sung Hyun; Kim, Doseok

    2010-03-01

    Fluorescence correlation spectroscopy (FCS) is a useful tool to study diffusional motion in liquids as it measures resident time of a dye molecule in a small excitation volume made by confocal microscopy. Some reports recently predicted that the measurement result of FCS is affected sensitively by the refractive index of liquid medium. To check for this possibility, several liquids having the same viscosity values but different refractive indices were chosen to dissolve dye molecules. The change in the observed diffusion coefficients in solutions having the same viscosity value manifests that care needs to be taken in the common practice of using sucrose to change the viscosity in the FCS experiment.

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

  6. On the Determination of Refractive Index and Thickness of Thin Dielectric Films from Measurement of Transmittance

    NASA Astrophysics Data System (ADS)

    Shah, Z. H.; Ahmad, I.; Tahir, Q. A.; Khawaja, E. E.

    2012-12-01

    Refractive index and thickness of a transparent film (ZnS) on a transparent substrate (BK-7 glass) have been determined from measurement of normal incidence transmittance, using different methods. Some of the methods considered here are most widely used, as is apparent from the literature. The outcome of this study could help a researcher in selecting an appropriate method for such an application. The values of the refractive indices determined by different methods were found to be close to each other (within 0.5%). However, large (up to 4.4%) differences existed in the values of the thickness determined by different methods.

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

    NASA Astrophysics Data System (ADS)

    Ince, R.; Sınır, E.; Feeney, M.; Yükselici, M. H.; Ince, A. T.

    2008-07-01

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

  8. Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection.

    PubMed

    Zhang, Jiwei; Di, Jianglei; Li, Ying; Xi, Teli; Zhao, Jianlin

    2015-10-19

    We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes. PMID:26480394

  9. 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 Δn ˜ 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 Δn ˜ 0.039. These results are in good agreement with simulations, which are 21.3 and 7.39 nm for the same index changes.

  10. Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity

    NASA Astrophysics Data System (ADS)

    Morrison, Benjamin C.; Borrero-Echeverry, Daniel

    2015-11-01

    Index-matching fluids play an important role in many fluid dynamics experiments, particularly those involving particle tracking, as they can be used to minimize errors due to distortion from the refraction of light across interfaces of the apparatus. Common index-matching fluids, such as sodium iodide solutions or mineral oils, often have densities or viscosities very different from those of water. This can make them undesirable for use as a working fluid when using commercially available tracer particles or at high Reynolds numbers. A solution of ammonium thiocyanate (NH4SCN) can be used for index-matching common materials such as borosilicate glass and acrylic, and has material properties similar to those of water (ν ~ 1 . 6 cSt and ρ ~ 1 . 1 g/cc). We present an empirical model for predicting the refractive index of aqueous NH4SCN solutions as a function of temperature and NH4SCN concentration that allows experimenters to develop refractive index matching solutions for various common materials. This work was supported by the National Science Foundation (CBET-0853691) and by the James Borders Physics Student Fellowship at Reed College.

  11. Improving axial resolution in confocal microscopy with new high refractive index mounting media.

    PubMed

    Fouquet, Coralie; Gilles, Jean-François; Heck, Nicolas; Dos Santos, Marc; Schwartzmann, Richard; Cannaya, Vidjeacoumary; Morel, Marie-Pierre; Davidson, Robert Stephen; Trembleau, Alain; Bolte, Susanne

    2015-01-01

    Resolution, high signal intensity and elevated signal to noise ratio (SNR) are key issues for biologists who aim at studying the localisation of biological structures at the cellular and subcellular levels using confocal microscopy. The resolution required to separate sub-cellular biological structures is often near to the resolving power of the microscope. When optimally used, confocal microscopes may reach resolutions of 180 nm laterally and 500 nm axially, however, axial resolution in depth is often impaired by spherical aberration that may occur due to refractive index mismatches. Spherical aberration results in broadening of the point-spread function (PSF), a decrease in peak signal intensity when imaging in depth and a focal shift that leads to the distortion of the image along the z-axis and thus in a scaling error. In this study, we use the novel mounting medium CFM3 (Citifluor Ltd., UK) with a refractive index of 1.518 to minimize the effects of spherical aberration. This mounting medium is compatible with most common fluorochromes and fluorescent proteins. We compare its performance with established mounting media, harbouring refractive indices below 1.500, by estimating lateral and axial resolution with sub-resolution fluorescent beads. We show furthermore that the use of the high refractive index media renders the tissue transparent and improves considerably the axial resolution and imaging depth in immuno-labelled or fluorescent protein labelled fixed mouse brain tissue. We thus propose to use those novel high refractive index mounting media, whenever optimal axial resolution is required.

  12. Improving Axial Resolution in Confocal Microscopy with New High Refractive Index Mounting Media

    PubMed Central

    Fouquet, Coralie; Gilles, Jean-François; Heck, Nicolas; Dos Santos, Marc; Schwartzmann, Richard; Cannaya, Vidjeacoumary; Morel, Marie-Pierre; Davidson, Robert Stephen; Trembleau, Alain; Bolte, Susanne

    2015-01-01

    Resolution, high signal intensity and elevated signal to noise ratio (SNR) are key issues for biologists who aim at studying the localisation of biological structures at the cellular and subcellular levels using confocal microscopy. The resolution required to separate sub-cellular biological structures is often near to the resolving power of the microscope. When optimally used, confocal microscopes may reach resolutions of 180 nm laterally and 500 nm axially, however, axial resolution in depth is often impaired by spherical aberration that may occur due to refractive index mismatches. Spherical aberration results in broadening of the point-spread function (PSF), a decrease in peak signal intensity when imaging in depth and a focal shift that leads to the distortion of the image along the z-axis and thus in a scaling error. In this study, we use the novel mounting medium CFM3 (Citifluor Ltd., UK) with a refractive index of 1.518 to minimize the effects of spherical aberration. This mounting medium is compatible with most common fluorochromes and fluorescent proteins. We compare its performance with established mounting media, harbouring refractive indices below 1.500, by estimating lateral and axial resolution with sub-resolution fluorescent beads. We show furthermore that the use of the high refractive index media renders the tissue transparent and improves considerably the axial resolution and imaging depth in immuno-labelled or fluorescent protein labelled fixed mouse brain tissue. We thus propose to use those novel high refractive index mounting media, whenever optimal axial resolution is required. PMID:25822785

  13. Methods to retrieve the complex refractive index of aquatic suspended particles: going beyond simple shapes

    NASA Astrophysics Data System (ADS)

    Sánchez, Albert-Miquel; Piera, Jaume

    2016-07-01

    The scattering properties of aquatic suspended particles have many optical applications. Several data inversion methods have been proposed to estimate important features of particles, such as their size distribution or their refractive index. Most of the proposed methods are based on the Lorenz-Mie theory to solve Maxwell's equations, where particles are considered homogeneous spheres. A generalization that allows consideration of more complex-shaped particles is the T-matrix method. Although this approach imposes some geometrical restrictions (particles must be rotationally symmetrical) it is applicable to many life forms of phytoplankton. In this paper, three different scenarios are considered in order to compare the performance of several inversion methods for retrieving refractive indices. The error associated with each method is discussed and analyzed. The results suggest that inverse methods using the T-matrix approach are useful to accurately retrieve the refractive indices of particles with complex shapes, such as for many phytoplankton organisms.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  15. On the mechanism of photoinduced refractive index changes in phosphosilicate glass

    SciTech Connect

    Larionov, Yu V; Sokolov, V O; Plotnichenko, V G

    2010-05-26

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

  16. Sub-wavelength imaging of photo-induced refractive index pattern in chalcogenide glass films

    NASA Astrophysics Data System (ADS)

    Yang, Zhiyong; Anheier, Norman C.; Qiao, Hong A.; Lucas, Pierre

    2009-11-01

    Mapping of refractive index patterns with sub-wavelength resolution is achieved using Near-field Scanning Optical Microscopy (NSOM) in reflection mode. Imaging of index pattern is performed on surface gratings photo-imprinted in As 2S 3 films. The NSOM is adapted with a near infrared laser which wavelength (785 nm) is chosen to be within the transparency window of the glass film therefore allowing consistent measure of reflected light. Quantitative measurements of photo-induced index changes can then be obtained from knowledge of the initial film index. Images of gratings with a period of 0.5 micron are easily collected therefore demonstrating sub-wavelength spatial resolution. The technique permits to concurrently obtain a topographic image and index image of the gratings thereby permitting to quantify the extent of photodarkening and photoexpansion simultaneously. It is shown that relief gratings tend to vanish in films aged in air for several months however the index gratings remain.

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

    PubMed

    Besseling, T H; Jose, J; Van Blaaderen, A

    2015-02-01

    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.

  18. 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

  19. Measuring the Refractive Index of Bovine Corneal Stromal Cells Using Quantitative Phase Imaging

    PubMed Central

    Gardner, Steven J.; White, Nick; Albon, Julie; Knupp, Carlo; Kamma-Lorger, Christina S.; Meek, Keith M.

    2015-01-01

    The cornea is the primary refractive lens in the eye and transmits >90% of incident visible light. It has been suggested that the development of postoperative corneal haze could be due to an increase in light scattering from activated corneal stromal cells. Quiescent keratocytes are thought to produce crystallins that match the refractive index of their cytoplasm to the surrounding extracellular material, reducing the amount of light scattering. To test this, we measured the refractive index (RI) of bovine corneal stromal cells, using quantitative phase imaging of live cells in vitro, together with confocal microscopy. The RI of quiescent keratocytes (RI = 1.381 ± 0.004) matched the surrounding matrix, thus supporting the hypothesis that keratocyte cytoplasm does not scatter light in the normal cornea. We also observed that the RI drops after keratocyte activation (RI = 1.365 ± 0.003), leading to a mismatch with the surrounding intercellular matrix. Theoretical scattering models showed that this mismatch would reduce light transmission in the cornea. We conclude that corneal transparency depends on the matching of refractive indices between quiescent keratocytes and the surrounding tissue, and that after surgery or wounding, the resulting RI mismatch between the activated cells and their surrounds significantly contributes to light scattering. PMID:26488650

  20. Measuring the Refractive Index of Bovine Corneal Stromal Cells Using Quantitative Phase Imaging.

    PubMed

    Gardner, Steven J; White, Nick; Albon, Julie; Knupp, Carlo; Kamma-Lorger, Christina S; Meek, Keith M

    2015-10-20

    The cornea is the primary refractive lens in the eye and transmits >90% of incident visible light. It has been suggested that the development of postoperative corneal haze could be due to an increase in light scattering from activated corneal stromal cells. Quiescent keratocytes are thought to produce crystallins that match the refractive index of their cytoplasm to the surrounding extracellular material, reducing the amount of light scattering. To test this, we measured the refractive index (RI) of bovine corneal stromal cells, using quantitative phase imaging of live cells in vitro, together with confocal microscopy. The RI of quiescent keratocytes (RI = 1.381 ± 0.004) matched the surrounding matrix, thus supporting the hypothesis that keratocyte cytoplasm does not scatter light in the normal cornea. We also observed that the RI drops after keratocyte activation (RI = 1.365 ± 0.003), leading to a mismatch with the surrounding intercellular matrix. Theoretical scattering models showed that this mismatch would reduce light transmission in the cornea. We conclude that corneal transparency depends on the matching of refractive indices between quiescent keratocytes and the surrounding tissue, and that after surgery or wounding, the resulting RI mismatch between the activated cells and their surrounds significantly contributes to light scattering.

  1. Theoretical analysis on the refractive-index distribution and bandwidth of gradient-index polymer optical fibers from a centrifugal field

    NASA Astrophysics Data System (ADS)

    Wei, Ming-Hsin; Chen, Wen-Chang

    2003-04-01

    Theoretical analysis was applied to analyze the refractive-index distribution (RID) and bandwidth (BW) of gradient-index polymer optical fibers (GI POFs) prepared by a centrifugal field process. The RID of the prepared GI POF could be represented by the equation of n(r) = n1[1 - 2δ(r/a)g]1/2. The studied material systems were poly(hexafluoroisopropyl 2-fluoroacrylate) (PHFIP 2-FA)/dibutyl phthalate (DBP) and poly(methyl methacrylate) (PMMA)/benzyl benzoate (BEN). The RID and the BW were significantly affected by an essential parameter k, which was related to the material properties (density difference and molecular weight) and processing properties (rotating speed, temperature, and radius). As k increased, the characteristic constant of RID, g, decreased to a minimum and then increased sharply, owing to the separation of the polymer and the dopant. On the other hand, the relative refractive-index difference of RID, δ, increased to a steady value after k increased to a certain value. The variation of RID with k resulted in a local minimum of intermodal dispersion, and thus a maximum bandwidth was obtained. The maximum BW of the PHFIP 2-FA/DBP and PMMA/BEN systems at 1550 nm (100-m fiber length and 2-nm spectral width) for the case of k ≠ 0 were 6.7 and 3.2 Gb/s, respectively. The wavelength of light source affects the BW significantly only at k around zero because of the importance of the intramodal dispersion in this case.

  2. Band gap and refractive index tunability in thallium based layered mixed crystals

    NASA Astrophysics Data System (ADS)

    Gasanly, N. M.

    2015-07-01

    Compositional variation of the band gap energy and refractive index of TlMeX2-type (Me = Ga or In and X = S or Se) layered mixed crystals have been studied by the transmission and reflection measurements in the wavelength range of 400-1100 nm. The analysis of absorption data of TlGa1-xInxSe2, TlGa(S1-xSex)2, TlGa1-xInxS2, and TlIn(Se1-xSx)2 mixed crystals revealed the presence of both optical indirect and direct transitions. It was found that the energy band gaps of mixed crystals decrease at the replacing of gallium atoms by indium and of sulfur atoms by selenium ones. Through the similar replacing of atoms (smaller atoms by larger ones) in the studied mixed crystals, the refractive index shows the quite opposite behavior.

  3. Quantum Enhancement of the Index of Refraction in a Bose-Einstein Condensate.

    PubMed

    Bons, P C; de Haas, R; de Jong, D; Groot, A; van der Straten, P

    2016-04-29

    We study the index of refraction of an ultracold bosonic gas in the dilute regime. Using phase-contrast imaging with light detuned from resonance by several tens of linewidths, we image a single cloud of ultracold atoms for 100 consecutive shots, which enables the study of the scattering rate as a function of temperature and density using only a single cloud. We observe that the scattering rate is increased below the critical temperature for Bose-Einstein condensation by a factor of 3 compared to the single-atom scattering rate. We show that current atom-light interaction models to second order of the density show a similar increase, where the magnitude of the effect depends on the model that is used to calculate the pair-correlation function. This confirms that the effect of quantum statistics on the index of refraction is dominant in this regime. PMID:27176521

  4. Symmetry relations in the generalized Lorenz-Mie theory for lossless negative refractive index media

    NASA Astrophysics Data System (ADS)

    André Ambrosio, Leonardo

    2016-09-01

    In this paper we present a theoretical analysis of the generalized Lorenz-Mie theory for negative refractive index (NRI) media and spherical scatterers, extending the well-known concepts and definitions found in the literature involving dielectric or positive refractive index (PRI) particles. The consequences of a negative phase velocity and an anti-parallelism of the wave vector with respect to the Poynting vector are investigated and interpreted in this framework and, together with the symmetries found for the beam-shape coefficients when compared to the conventional PRI case, it is shown that the description of plane waves, Gaussian beams and, more generally, on-axis azimuthally symmetric waves along a NRI medium, their fields and all physical properties can be conveniently correlated with that of dielectric media once the electromagnetic response functions are replaced by their corresponding dielectric counterparts.

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

    NASA Astrophysics Data System (ADS)

    Zubko, Evgenij; Videen, Gorden; Shkuratov, Yuriy

    2015-01-01

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

  6. D-shaped fiber grating refractive index sensor induced by an ultrashort pulse laser.

    PubMed

    Liao, Changrui; Wang, Qiao; Xu, Lei; Liu, Shen; He, Jun; Zhao, Jing; Li, Zhengyong; Wang, Yiping

    2016-03-01

    The fabrication of fiber Bragg gratings was here demonstrated using ultrashort pulse laser point-by-point inscription. This is a very convenient means of creating fiber Bragg gratings with different grating periods and works by changing the translation speed of the fiber. The laser energy was first optimized in order to improve the spectral properties of the fiber gratings. Then, fiber Bragg gratings were formed into D-shaped fibers for use as refractive index sensors. A nonlinear relationship was observed between the Bragg wavelength and liquid refractive index, and a sensitivity of ∼30  nm/RIU was observed at 1.450. This shows that D-shaped fiber Bragg gratings might be used to develop promising biochemical sensors. PMID:26974608

  7. High refractive index Fresnel lens on a fiber fabricated by nanoimprint lithography for immersion applications.

    PubMed

    Koshelev, Alexander; Calafiore, Giuseppe; Piña-Hernandez, Carlos; Allen, Frances I; Dhuey, Scott; Sassolini, Simone; Wong, Edward; Lum, Paul; Munechika, Keiko; Cabrini, Stefano

    2016-08-01

    In this Letter, we present a Fresnel lens fabricated on the end of an optical fiber. The lens is fabricated using nanoimprint lithography of a functional high refractive index material, which is suitable for mass production. The main advantage of the presented Fresnel lens compared to a conventional fiber lens is its high refractive index (n=1.68), which enables efficient light focusing even inside other media, such as water or an adhesive. Measurement of the lens performance in an immersion liquid (n=1.51) shows a near diffraction limited focal spot of 810 nm in diameter at the 1/e2 intensity level for a wavelength of 660 nm. Applications of such fiber lenses include integrated optics, optical trapping, and fiber probes.

  8. Diffractive Optical Analysis for Refractive Index Sensing using Transparent Phase Gratings.

    PubMed

    Kumawat, Nityanand; Pal, Parama; Varma, Manoj

    2015-01-01

    We report the implementation of a micro-patterned, glass-based photonic sensing element that is capable of label-free biosensing. The diffractive optical analyzer is based on the differential response of diffracted orders to bulk as well as surface refractive index changes. The differential read-out suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6 × 10(-7) was achieved with this technique with scope for further improvement. PMID:26578408

  9. High refractive index Fresnel lens on a fiber fabricated by nanoimprint lithography for immersion applications

    NASA Astrophysics Data System (ADS)

    Koshelev, Alexander; Calafiore, Giuseppe; Piña-Hernandez, Carlos; Allen, Frances I.; Dhuey, Scott; Sassolini, Simone; Wong, Edward; Lum, Paul; Munechika, Keiko; Cabrini, Stefano

    2016-08-01

    In this Letter we present a Fresnel lens fabricated on the end of an optical fiber. The lens is fabricated using nanoimprint lithography of a functional high refractive index material, which is suitable for mass production. The main advantage of the presented Fresnel lens compared to a conventional fiber lens is its high refractive index (n=1.69), which enables efficient light focusing even inside other media such as water or adhesive. Measurement of the lens performance in an immersion liquid (n=1.51) shows a near diffraction limited focal spot of 810 nm in diameter at the 1/e2 intensity level for a wavelength of 660 nm. Applications of such fiber lenses include integrated optics, optical trapping and fiber probes.

  10. High refractive index Fresnel lens on a fiber fabricated by nanoimprint lithography for immersion applications.

    PubMed

    Koshelev, Alexander; Calafiore, Giuseppe; Piña-Hernandez, Carlos; Allen, Frances I; Dhuey, Scott; Sassolini, Simone; Wong, Edward; Lum, Paul; Munechika, Keiko; Cabrini, Stefano

    2016-08-01

    In this Letter, we present a Fresnel lens fabricated on the end of an optical fiber. The lens is fabricated using nanoimprint lithography of a functional high refractive index material, which is suitable for mass production. The main advantage of the presented Fresnel lens compared to a conventional fiber lens is its high refractive index (n=1.68), which enables efficient light focusing even inside other media, such as water or an adhesive. Measurement of the lens performance in an immersion liquid (n=1.51) shows a near diffraction limited focal spot of 810 nm in diameter at the 1/e2 intensity level for a wavelength of 660 nm. Applications of such fiber lenses include integrated optics, optical trapping, and fiber probes. PMID:27472584

  11. 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 ((Δn/n)=0.394).

  12. Analysis of thermo-optic effect-based refractive index dynamic modulation in microspherical resonator.

    PubMed

    Wang, Yue; Wang, Quan-Long; Zhou, Song; Wu, Jun-Feng; Wu, Yi-Hui

    2015-10-01

    The thermo-optic effect has been utilized to modulate the refractive index dynamically within a whispering gallery mode resonator. Modulation with a large tuning range is mostly performed for mode locking and dynamic control of the optical path at a modulation frequency as low as several hertz, while high-frequency modulation up to megahertz is mainly exploited in optical switching devices with small tuning range. Here, we introduce the response functions theoretically to describe the dynamic response of temperature changes in the mode volume and the resonator body, respectively. This result is verified experimentally in silica microspherical resonators. The dependence of the tuning range on the modulation frequency is achieved. This knowledge could pave the way toward more practical control of refractive index in microresonators. PMID:26479610

  13. Femtosecond laser fabrication of long period fiber gratings and applications in refractive index sensing

    NASA Astrophysics Data System (ADS)

    Li, Benye; Jiang, Lan; Wang, Sumei; Tsai, Hai-Lung; Xiao, Hai

    2011-11-01

    An improved point-by-point inscription method is proposed to fabricate long period fiber gratings (LPFGs) by using a laser operating at 800 nm with 35 fs duration pulses. The sensitivity to misalignment between the core and the focus is reduced by scanning a rectangular part on the fiber. LPFGs with an attenuation depth of 20 dB are achieved within the wavelength range of 1465-1575 nm. Characterization of the temperature sensitivity and thermal stability of the LPFGs is presented. A 5.6 nm wavelength shift and a 1.2 dB decrease in the attenuation peak are observed following heat treatment at 600 °C for 4 h. The fabricated LPFGs are used as refractive index sensors. The effect of heat treatment on the response of the LPFGs to refractive index changes is also studied.

  14. Refractive index matching to develop transparent polyaphrons: Characterization of immobilized proteins.

    PubMed

    Ward, Keeran; Stuckey, David C

    2016-06-01

    Refractive index matching was used to create optically transparent polyaphrons to enable proteins adsorbed to the aphron surface to be characterized. Due to the significant light scattering created by polyaphrons, refractive index matching allowed for representative circular dichroism (CD) spectra and acceptable structural characterization. The method utilized n-hexane as the solvent phase, a mixture of glycerol and phosphate buffer (30% [w/v]) as the aqueous phase, and the non-ionic surfactants, Laureth-4 and Kolliphor P-188. Deconvolution of CD spectra revealed that the immobilized protein adapted its native conformation, showing that the adsorbed protein interacted only with the bound water layer ("soapy shell") of the aphron. Isothermal calorimetry further demonstrated that non-ionic surfactant interactions were virtually non-existent, even at the high concentrations used (5% [w/v]), proving that non-ionic surfactants can preserve protein conformation.

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

    SciTech Connect

    Oliva, R.; Yamaguchi, T.; Nanishi, Y.

    2014-12-08

    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 ε{sub ∞}. Negative pressure coefficients of −8.8 × 10{sup −2 }GPa{sup −1} and −14.8 × 10{sup −2 }GPa{sup −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.

  16. Quantum Enhancement of the Index of Refraction in a Bose-Einstein Condensate.

    PubMed

    Bons, P C; de Haas, R; de Jong, D; Groot, A; van der Straten, P

    2016-04-29

    We study the index of refraction of an ultracold bosonic gas in the dilute regime. Using phase-contrast imaging with light detuned from resonance by several tens of linewidths, we image a single cloud of ultracold atoms for 100 consecutive shots, which enables the study of the scattering rate as a function of temperature and density using only a single cloud. We observe that the scattering rate is increased below the critical temperature for Bose-Einstein condensation by a factor of 3 compared to the single-atom scattering rate. We show that current atom-light interaction models to second order of the density show a similar increase, where the magnitude of the effect depends on the model that is used to calculate the pair-correlation function. This confirms that the effect of quantum statistics on the index of refraction is dominant in this regime.

  17. Binary and Ternary Mixtures of Biopolymers and Water: Viscosity, Refractive Index, and Density

    NASA Astrophysics Data System (ADS)

    Silva, Bárbara Louise L. D.; Costa, Bernardo S.; Garcia-Rojas, Edwin E.

    2016-08-01

    Biopolymers have been the focus of intense research because of their wide applicability. The thermophysical properties of solutions containing biopolymers have fundamental importance for engineering calculations, as well as for thermal load calculations, energy expenditure, and development of new products. In this work, the thermophysical properties of binary and ternary solutions of carboxymethylcellulose and/or high methoxylation pectin and water at different temperatures have been investigated taking into consideration different biopolymer concentrations. The experimental data related to the thermophysical properties were correlated to obtain empirical models that can describe the temperature-concentration combined effect on the density, refractive index, and dynamic viscosity. From data obtained from the experiments, the density, refractive index, and dynamic viscosity increase with increasing biopolymer concentration and decrease with increasing temperature. The polynomial models showed a good fit to the experimental data and high correlation coefficients (R2ge 0.98) for each studied system.

  18. Omnidirectional reflector using nanoporous SiO2 as a low-refractive-index material.

    PubMed

    Xi, J Q; Ojha, Manas; Cho, Woojin; Plawsky, J L; Gill, W N; Gessmann, Th; Schubert, E F

    2005-06-15

    Triple-layer omnidirectional reflectors (ODRs) consisting of a semiconductor, a quarter-wavelength transparent dielectric layer, and a metal have high reflectivities for all angles of incidence. Internal ODRs (ambient material's refractive index n > 1.0) are demonstrated that incorporate nanoporous SiO2, a low-refractive-index material (n = 1.23), as well as dense SiO2 (n = 1.46). GaP and Ag serve as the semiconductor and the metal layer, respectively. Reflectivity measurements, including angular dependence, are presented. Calculated angle-integrated TE and TM reflectivities for ODRs employing nanoporous SiO2 are R(int)/TE = 99.9% and R(int)/TM = 98.9%, respectively, indicating the high potential of the ODRs for low-loss waveguide structures.

  19. A model for the influence of granularity in a negative refractive index metamaterial lens

    NASA Astrophysics Data System (ADS)

    Webb, Kevin; Li, Jia-Han

    2006-03-01

    An important goal in building a negative refractive index metamaterial lens at optical frequencies is the achievement of sub-wavelength image resolution. In assigning an effective medium negative refractive index, the electric and magnetic dipoles (which give rise to negative permittivity and permeability) need to be dense relative to the wavelength, i.e., operation near the center of the first Brillouin zone is a prerequisite. Sub-wavelength imaging requires good performance for a significant portion of the evanescent plane wave spectrum. We use a model comprised of discrete regions with negative permittivity and permeability, calculate the effective medium parameters, and show the impact of granularity level (scatterer density) on the performance of a discrete lens, using the slab lens as a reference. We thus arrive at a measure of metamaterial density required to achieve significant improvement over traditional lensing approaches.

  20. Refractive index detection of liquid based on magneto-optical surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Zhang, Yanfen; Tang, Tingting; Li, Jie; Luo, Li

    2016-09-01

    We propose a refractive index sensor applied in liquid detection based on magneto-optical surface plasmon resonance. The device is made of a prism-coupling system, which consists of a prism and a CeYIG/Au/liquid waveguide. Systematic simulations using the finite element method and 4  ×  4 transfer matrix methods are implemented to calculate the figure of merit (FOM) of sensitivity. Calculation results show that a FOM of 5.022/RIU for refractive index variation from 1.330 to 1.345 can be obtained when the incident wavelength is 980 nm. The proposed structure can achieve high angular sensitivity for the magnetic field of the proposed structure concentrated in the sensing medium. Meanwhile, our sensor, with gold as the bottom layer, is a better hydrophily for the molecular self-assembly technique compared with other conventional sensors, which makes it more practical in applications.

  1. 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

  2. Bend and refractive index sensing based on the tuning fork fiber

    NASA Astrophysics Data System (ADS)

    Sun, Bo; Li, Xuyou; Yu, Yingying; He, Kunpeng

    2015-08-01

    A fiber-optic based on the tuning fork structure is investigated for bend and refractive index (RI). The new bend/RI sensor based on the tuning fork structure is ease of fabrication, low cost, and simple signal acquisition. The operation principle relies on the power coupling of two cores inputted into light simultaneously. The beam-propagation method (BPM) is employed for modeling the propagation of light along the optical fiber sensing device proposed. The simulation results show that it exhibits very high sensitivity, accuracy and wide dynamic range in making curvature and RI measurements. The bending sensitivity is about 0.01184 W/m-1 at curvatures ranging from 0 to 50 m-1, the RI sensitivity is about -1.5557, -22.3031 and -102.44878 W/RIU at refractive indexes ranging from 1.33-1.418, 1.418-1.45 and 1.45-1.456, respectively.

  3. Refractive index sensitivity enhancement of optical fiber cladding mode by depositing nanofilm via ALD technology.

    PubMed

    Zhao, Ying; Pang, Fufei; Dong, Yanhua; Wen, Jianxiang; Chen, Zhenyi; Wang, Tingyun

    2013-11-01

    The atomic layer deposition (ALD) technology is introduced to enhance the sensitivity of optical fiber cladding mode to surrounding refractive index (SRI) variation. The highly uniform Al2O nanofilm was deposited around the double cladding fiber (DCF) which presents cladding mode resonant feature. With the high refractive index coating, the cladding mode resonant spectrum was tuned. And the sensitivity enhancement for SRI sensor was demonstrated. Through adjusting the deposition cycles, a maximum sensitivity of 723 nm/RIU was demonstrated in the DCF with 2500 deposition cycles at the SRI of 1.34. Based on the analysis of cladding modes reorganization, the cladding modes transition of the coated DCF was investigated theoretically. With the high performance nanofilm coating, the proposed SRI sensor is expected to have wide applications in chemical sensors and biosensors.

  4. 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.

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

    NASA Technical Reports Server (NTRS)

    Lally, J.; Meister, R.

    1983-01-01

    The Properties of Materials in the Submillimeter Wave Region study was initiated to instrument a system and to make measurements of the complex index of refraction in the wavelength region between 0.1 to 1.0 millimeters. While refractive index data is available for a number of solids and liquids there still exists a need for an additional systematic study of dielectric properties to add to the existing data, to consider the accuracy of the existing data, and to extend measurements in this wavelength region for other selected mateials. The materials chosen for consideration would be those with useful thermal, mechanical, and electrical characteristics. The data is necessary for development of optical components which, for example, include beamsplitters, attenuators, lenses, grids, all useful for development of instrumentation in this relatively unexploited portion of the spectrum.

  6. Intersubband transitions and refractive index changes in coupled double quantum well with different well shapes

    NASA Astrophysics Data System (ADS)

    Ozturk, Emine; Sokmen, Ismail

    2011-10-01

    In this study, both the linear intersubband transitions and the refractive index changes in coupled double quantum well (DQW) with different well shapes for different electric fields are theoretically calculated within framework of the effective mass approximation. Results obtained show that intersubband transitions and the energy levels in coupled DQW can importantly be modified and controlled by the electric field strength and direction. By considering the variation of the energy differences, it should point out that by varying electric field we can obtain a blue or red shift in the intersubband optical transitions. The modulation of the absorption coefficients and the refractive index changes which can be suitable for good performance optical modulators and various infrared optical device applications can be easy obtained by tuning applied electric field strength and direction.

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

    PubMed

    Krug, Peter A; Rogojan, Rodica Matei; 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/cm2. 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 6 x 10(-5) were formed at cumulative fluences of 1 kJ/cm2 and above.

  8. Diffractive Optical Analysis for Refractive Index Sensing using Transparent Phase Gratings

    PubMed Central

    Kumawat, Nityanand; Pal, Parama; Varma, Manoj

    2015-01-01

    We report the implementation of a micro-patterned, glass-based photonic sensing element that is capable of label-free biosensing. The diffractive optical analyzer is based on the differential response of diffracted orders to bulk as well as surface refractive index changes. The differential read-out suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6 × 10−7 was achieved with this technique with scope for further improvement. PMID:26578408

  9. 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.

  10. Determination of refractive index and concentration of iodine solutions using opals

    NASA Astrophysics Data System (ADS)

    Kępińska, Mirosława; Starczewska, Anna; Szala, Janusz

    2014-03-01

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

  11. Refractive index degeneration in older lenses: A potential functional correlate to structural changes that underlie cataract formation.

    PubMed

    Bahrami, Mehdi; Hoshino, Masato; Pierscionek, Barbara; Yagi, Naoto; Regini, Justyn; Uesugi, Kentaro

    2015-11-01

    A major structure/function relationship in the eye lens is that between the constituent proteins, the crystallins and the optical property of refractive index. Structural breakdown that leads to cataract has been investigated in a number of studies; the concomitant changes in the optics, namely increases in light attenuation have also been well documented. Specific changes in the refractive index gradient that cause such attenuation, however, are not well studied because previous methods of measuring refractive index require transparent samples. The X-ray Talbot interferometric method using synchrotron radiation allows for measurement of fine changes in refractive index through lenses with opacities. The findings of this study on older human lenses show disruptions to the refractive index gradient and in the refractive index contours. These disruptions are linked to location in the lens and occur in polar regions, along or close to the equatorial plane or in lamellar-like formations. The disruptions that are seen in the polar regions manifest branching formations that alter with progression through the lens with some similarity to lens sutures. This study shows how the refractive index gradient, which is needed to maintain image quality of the eye, may be disturbed and that this can occur in a number of distinct ways. These findings offer insight into functional changes to a major optical parameter in older lenses. Further studies are needed to elicit how these may be related to structural degenerations reported in the literature. PMID:26297613

  12. Refractive index degeneration in older lenses: A potential functional correlate to structural changes that underlie cataract formation.

    PubMed

    Bahrami, Mehdi; Hoshino, Masato; Pierscionek, Barbara; Yagi, Naoto; Regini, Justyn; Uesugi, Kentaro

    2015-11-01

    A major structure/function relationship in the eye lens is that between the constituent proteins, the crystallins and the optical property of refractive index. Structural breakdown that leads to cataract has been investigated in a number of studies; the concomitant changes in the optics, namely increases in light attenuation have also been well documented. Specific changes in the refractive index gradient that cause such attenuation, however, are not well studied because previous methods of measuring refractive index require transparent samples. The X-ray Talbot interferometric method using synchrotron radiation allows for measurement of fine changes in refractive index through lenses with opacities. The findings of this study on older human lenses show disruptions to the refractive index gradient and in the refractive index contours. These disruptions are linked to location in the lens and occur in polar regions, along or close to the equatorial plane or in lamellar-like formations. The disruptions that are seen in the polar regions manifest branching formations that alter with progression through the lens with some similarity to lens sutures. This study shows how the refractive index gradient, which is needed to maintain image quality of the eye, may be disturbed and that this can occur in a number of distinct ways. These findings offer insight into functional changes to a major optical parameter in older lenses. Further studies are needed to elicit how these may be related to structural degenerations reported in the literature.

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

    PubMed

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

    2014-06-15

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

  14. Block Copolymer Nanocomposites with High Refractive Index Contrast for One-Step Photonics.

    PubMed

    Song, Dong-Po; Li, Cheng; Li, Wenhao; Watkins, James J

    2016-01-26

    Photonic crystals (PhCs) prepared using the self-assembly of block copolymers (BCPs) offer the potential for simple and rapid device fabrication but typically suffer from low refractive index contrast (Δn ≤ 0.1) between the phase-segregated domains. Here, we report the simple fabrication of BCP-based photonic nanocomposites with large differences in refractive index (Δn > 0.27). Zirconium oxide (ZrO2) nanoparticles coated with gallic acid are used to tune the optical constants of the target domains of self-assembled (polynorbornene-graft-poly(tert-butyl acrylate))-block-(polynorbornene-graft-poly(ethylene oxide)) (PtBA-b-PEO) brush block copolymers (BBCPs). Strong hydrogen-bonding interactions between the ligands on ZrO2 and PEO brushes of the BBCPs enable selective incorporation and high loading of up to 70 wt % (42 vol %) of the ZrO2 nanoparticles within the PEO domain, resulting in a significant increase of refractive index from 1.45 to up to 1.70. Consequently, greatly enhanced reflection at approximately 398 nm (increases of ∼250%) was observed for the photonic nanocomposites (domain spacing = 137 nm) relative to that of the unmodified BBCPs, which is consistent with numeric modeling results using transfer matrix methods. This work provides a simple strategy for a wide range tuning of optical constants of BCP domains, thereby enabling the design and creation of high-performance photonic coatings for various applications. The large refractive index contrast enables high reflectivity while simultaneously reducing the coating thickness necessary, compared to pure BCP systems.

  15. Simultaneous determination of size and refractive index of red blood cells by light scattering measurements

    SciTech Connect

    Ghosh, N.; Buddhiwant, P.; Uppal, A.; Majumder, S.K.; Patel, H.S.; Gupta, P.K.

    2006-02-20

    We present a fast and accurate approach for simultaneous determination of both the mean diameter and refractive index of a collection of red blood cells (RBCs). The approach uses the peak frequency of the power spectrum and the corresponding phase angle obtained by performing Fourier transform on the measured angular distribution of scattered light to determine these parameters. Results on the measurement of two important clinical parameters, the mean cell volume and mean cell hemoglobin concentration of a collection of RBCs, are presented.

  16. 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.

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

    PubMed

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

    2007-10-20

    A passive-polarization-based imaging system records the polarization state of light reflected by objects that are illuminated with an unpolarized and generally uncontrolled source. Such systems can be useful in many remote sensing applications including target detection, object segmentation, and material classification. We present a method to jointly estimate the complex index of refraction and the reflection angle (reflected zenith angle) of a target from multiple measurements collected by a passive polarimeter. An expression for the degree of polarization is derived from the microfacet polarimetric bidirectional reflectance model for the case of scattering in the plane of incidence. Using this expression, we develop a nonlinear least-squares estimation algorithm for extracting an apparent index of refraction and the reflection angle from a set of polarization measurements collected from multiple source positions. Computer simulation results show that the estimation accuracy generally improves with an increasing number of source position measurements. Laboratory results indicate that the proposed method is effective for recovering the reflection angle and that the estimated index of refraction provides a feature vector that is robust to the reflection angle. PMID:17952192

  18. 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.

  19. 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

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    For any technique to be adopted into a clinical setting, it is imperative that it seamlessly integrates with well-established clinical diagnostic workflow. We recently developed an optical microscopy technique--spatial-domain low-coherence quantitative phase microscopy (SL-QPM) that can extract the refractive index of the cell nucleus from the standard histology specimens on glass slides prepared via standard clinical protocols. This technique has shown great potential in detecting cancer with a better sensitivity than conventional pathology. A major hurdle in the clinical translation of this technique is the intrinsic variation among staining agents used in histology specimens, which limits the accuracy of refractive index measurements of clinical samples. In this paper, we present a simple and easily generalizable method to remove the effect of variations in staining levels on nuclear refractive index obtained with SL-QPM. We illustrate the efficacy of our correction method by applying it to variously stained histology samples from animal model and clinical specimens.

  1. Polarimetric techniques for determining morphology and optical features of high refractive index dielectric nanoparticle size

    NASA Astrophysics Data System (ADS)

    Barreda, Ángela I.; Sanz, Juan M.; Alcaraz de la Osa, Rodrigo; Saiz, José M.; Moreno, Fernando; González, Francisco

    2016-03-01

    The spectral evolution of the degree of linear polarization (PL) at a scattering angle of 90° is studied numerically for high refractive index (HRI) dielectric spherical nanoparticles. The behaviour of PL(90°) is analyzed as a function of the refractive index of the surrounding medium and the particle radius. We focus on the spectral region where both electric and magnetic resonances of order not higher than two are located for various semiconductor materials with low absorption. The spectral behavior of PL(90°) has only a small, linear dependence on nanoparticle size R. This weak dependence makes it experimentally feasible to perform real-time retrievals of both the refractive index of the external medium and the NP size R. From an industrial point of view, pure materials are nonrealistic, since they can only be provided under certain conditions. For this reason, we also study the effect of contaminants on the resonances of silicon NPs by considering the spectral evolution of PL(90°).

  2. Imaginary refractive index and other microphysical properties of volcanic ash, Sarahan dust, and other mineral aerosols

    NASA Astrophysics Data System (ADS)

    Rocha Lima, A.; Martins, J.; Krotkov, N. A.; Artaxo, P.; Todd, M.; Ben Ami, Y.; Dolgos, G.; Espinosa, R.

    2013-12-01

    Aerosol properties are essential to support remote sensing measurements, atmospheric circulation and climate models. This research aims to improve the understanding of the optical and microphysical properties of different types of aerosols particles. Samples of volcanic ash, Saharan dust and other mineral aerosols particles were analyzed by different techniques. Ground samples were sieved down to 45um, de-agglomerated and resuspended in the laboratory using a Fluidized Bed Aerosol Generator (FBAG). Particles were collected on Nuclepore filters into PM10, PM2.5, or PM1.0. and analyzed by different techniques, such as Scanning Electron Microscopy (SEM) for determination of size distribution and shape, spectral reflectance for determination of the optical absorption properties as a function of the wavelength, material density, and X-Ray fluorescence for the elemental composition. The spectral imaginary part of refractive index from the UV to the short wave infrared (SWIR) wavelength was derived empirically from the measurements of the spectral mass absorption coefficient, size distribution and density of the material. Some selected samples were also analyzed with the Polarized Imaging Nephelometer (PI-Neph) instrument for the characterization of the aerosol polarized phase function. This work compares results of the spectral refractive index of different materials obtained by our methodology with those available in the literature. In some cases there are significant differences both in magnitude and spectral dependence of the imaginary refractive index. These differences are evaluated and discussed in this work.

  3. Highly sensitive multi-core flat fiber surface plasmon resonance refractive index sensor.

    PubMed

    Rifat, Ahmmed A; Mahdiraji, G A; Sua, Yong Meng; Ahmed, Rajib; Shee, Y G; Adikan, F R Mahamd

    2016-02-01

    A simple multi-core flat fiber (MCFF) based surface plasmon resonance (SPR) sensor operating in telecommunication wavelengths is proposed for refractive index sensing. Chemically stable gold (Au) and titanium dioxide (TiO(2)) layers are used outside the fiber structure to realize a simple detection mechanism. The modeled sensor shows average wavelength interrogation sensitivity of 9,600 nm/RIU (Refractive Index Unit) and maximum sensitivity of 23,000 nm/RIU in the sensing range of 1.46-1.485 and 1.47-1.475, respectively. Moreover, the refractive index resolution of 4.35 × 10(-6) is demonstrated. Additionally, proposed sensor had shown the maximum amplitude interrogation sensitivity of 820 RIU(-1), with the sensor resolution of 1.22 × 10(-5) RIU. To the best of our knowledge, the proposed sensor achieved the highest wavelength interrogation sensitivity among the reported fiber based SPR sensors. Finally we anticipate that, this novel and highly sensitive MCFF SPR sensor will find the potential applications in real time remote sensing and monitoring, ultimately enabling inexpensive and accurate chemical and biochemical analytes detection. PMID:26906823

  4. On a quasi-wavelet model of refractive index fluctuations due to atmospheric turbulence.

    PubMed

    Pérez, Darío G; Funes, Gustavo

    2015-12-14

    When studying light propagation through the atmosphere, it is usual to rely on widely used spectra such as the modified von Kármán or Andrews-Hill. These are relatively tractable models for the fluctuations of the refractive index, and are primarily used because of their mathematical convenience. They correctly describe the fluctuations behaviour at the inertial range yet lack any physical basis outside this range. In recent years, deviations from the Obukhov-Kolmogorov theory (e. g. interminttency, partially developed turbulence, etc.) have been built upon these models through the introduction of arbitrary spectral power laws. Here we introduce a quasi-wavelet model for the refractive index fluctuations which is based on a phenomenological representation of the Richardson cascade. Under this model, the atmospheric refractive index has a correct spectral representation for the inertial range, behaves as expected outside it, and even accounts for non-Kolmogorov behaviour; moreover, it has non-Gaussian statistics. Finally, we are able to produce second order moments under the Rytov approximation for the complex phase; we estimate the angle-of-arrival as an example of application.

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

    PubMed

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

    2014-02-27

    Refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, RI contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving parts approach that provides three-dimensional refractive index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate RI maps of the samples from the measured spectra. Using this method, we demonstrate label-free 3-D imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass and density of these cells from the measured 3-D refractive index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, promises as a quantitative tool for stain-free characterization of large number of cells.

  6. Highly sensitive multi-core flat fiber surface plasmon resonance refractive index sensor.

    PubMed

    Rifat, Ahmmed A; Mahdiraji, G A; Sua, Yong Meng; Ahmed, Rajib; Shee, Y G; Adikan, F R Mahamd

    2016-02-01

    A simple multi-core flat fiber (MCFF) based surface plasmon resonance (SPR) sensor operating in telecommunication wavelengths is proposed for refractive index sensing. Chemically stable gold (Au) and titanium dioxide (TiO(2)) layers are used outside the fiber structure to realize a simple detection mechanism. The modeled sensor shows average wavelength interrogation sensitivity of 9,600 nm/RIU (Refractive Index Unit) and maximum sensitivity of 23,000 nm/RIU in the sensing range of 1.46-1.485 and 1.47-1.475, respectively. Moreover, the refractive index resolution of 4.35 × 10(-6) is demonstrated. Additionally, proposed sensor had shown the maximum amplitude interrogation sensitivity of 820 RIU(-1), with the sensor resolution of 1.22 × 10(-5) RIU. To the best of our knowledge, the proposed sensor achieved the highest wavelength interrogation sensitivity among the reported fiber based SPR sensors. Finally we anticipate that, this novel and highly sensitive MCFF SPR sensor will find the potential applications in real time remote sensing and monitoring, ultimately enabling inexpensive and accurate chemical and biochemical analytes detection.

  7. Retrieving the real refractive index of mono- and polydisperse colloids from reflectance near the critical angle.

    PubMed

    Reed, Benjamin E; Grainger, Roy G; Peters, Daniel M; Smith, Andrew J A

    2016-02-01

    We investigate the accuracy in retrieving the real refractive index of submicron aerosol particles, at a visible wavelength, from near critical angle reflectance measurements of a dilute suspension of the aerosol. A coherent scattering model (CSM) is used to model the coherent reflectance from the colloidal suspension. We use an extension of the model for polydisperse particles to properly account for the modified size distribution close to the incident medium to colloid interface. We perform a rigorous sensitivity analysis, for both the monodisperse and polydisperse models, to determine how experimental uncertainties propagate into uncertainty in the retrieval of real refractive index. The effect of non-spherical scattering was included in the sensitivity analysis by using T-matrix methods. Experimental reflectance data, at a wavelength of 635 nm, were obtained for monodisperse spherical latex particles, a polydisperse sand sample and a polydisperse volcanic ash sample. We show that the retrieved real refractive index for these particles is consistent with values obtained using other techniques.

  8. Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range.

    PubMed

    Wu, Xiaojun; Zhou, Chun; Huang, Wenqian Ronny; Ahr, Frederike; Kärtner, Franz X

    2015-11-16

    Optical rectification with tilted pulse fronts in lithium niobate crystals is one of the most promising methods to generate terahertz (THz) radiation. In order to achieve higher optical-to-THz energy efficiency, it is necessary to cryogenically cool the crystal not only to decrease the linear phonon absorption for the generated THz wave but also to lengthen the effective interaction length between infrared pump pulses and THz waves. However, the refractive index of lithium niobate crystal at lower temperature is not the same as that at room temperature, resulting in the necessity to re-optimize or even re-build the tilted pulse front setup. Here, we performed a temperature dependent measurement of refractive index and absorption coefficient on a 6.0 mol% MgO-doped congruent lithium niobate wafer by using a THz time-domain spectrometer (THz-TDS). When the crystal temperature was decreased from 300 K to 50 K, the refractive index of the crystal in the extraordinary polarization decreased from 5.05 to 4.88 at 0.4 THz, resulting in ~1° change for the tilt angle inside the lithium niobate crystal. The angle of incidence on the grating for the tilted pulse front setup at 1030 nm with demagnification factor of -0.5 needs to be changed by 3°. The absorption coefficient decreased by 60% at 0.4 THz. These results are crucial for designing an optimum tilted pulse front setup based on lithium niobate crystals.

  9. Retrieval of dust particle refractive index from scattering data using ellipsoid ensembles

    NASA Astrophysics Data System (ADS)

    Kemppinen, Osku; Nousiainen, Timo; Merikallio, Sini; Räisänen, Petri

    2016-04-01

    Retrieval of aerosol microphysical properties, such as dust particle refractive index, from remote sensing data is a key problem. Even when full scattering matrix data is available, the problem is challenging to solve due to the large number of possible particle property combinations, and the non-linear response of scattering data to changes in these properties. One approach is to perform a mathematical fit of a pre-defined shape class, such as ellipsoids, varying the free parameter, and evaluating the goodness of the fit for each free parameter value. It is known that a shape ensemble of ellipsoids can replicate dust particle scattering data with good accuracy, but it is less known if the good match guarantees that the microphysical properties used in the ensemble correspond to those of the real particle. Essentially, it is unclear if a small fit residue guarantees that the parameter is retrieved accurately. In this work, we test how accurate the refractive index retrieval with shape ensembles of ellipsoids is by using computational scattering data. Using the computational data allows us to know with certainty what is the true refractive index of the particle in question, and thus to quantify the retrieval accuracy. We test multiple realistic dust-like particle shapes that have been inverted from real dust particles by using electron microscopy stereogrammetry.

  10. Measurement of air refractive index fluctuation based on interferometry with two different reference cavity lengths.

    PubMed

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

    2012-09-01

    A measurement method based on interferometry with two different reference cavity lengths is presented and applied in air refractive index measurement in which the two cavity lengths and a laser wavelength are combined to generate two wavelength equivalents of cavity. Corresponding calculation equations are derived, and the optical path configuration is designed, which is inspired by the traditional synthetic wavelength method. Theoretical analyses indicate that the measurement uncertainty of the determined index of refraction is about 2.3×10(-8), which is mainly affected by the length precision of the long vacuum cavity and the ellipticity of polarization components of the dual-frequency laser, and the range of nonambiguity is 3.0×10(-5), which is decided by the length difference of the two cavities. Experiment results show that the accuracy of air refractive index measurement is better than 5.0×10(-8) when the laboratory conditions changes slowly. The merit of the presented method is that the classical refractometry can be also used without evacuation of the gas cavity during the experiment. Furthermore, the application of the traditional synthetic wavelength method may be extended by using the wavelength equivalents of cavity, any value of which can be easily acquired by changing cavity length rather than using actual wavelengths whose number is limited. PMID:22945157

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    In order to enable high quality lens design using calcium fluoride (CaF2) and Heraeus Infrasil 30 (Infrasil) at cryogenic temperatures, we have measured the absolute refractive index of prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For CaF2, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 25 to 300 K at wavelengths from 0.4 to 5.6 micrometers; for Infrasil we cover temperatures ranging from 35 to 300K and wavelengths from 0.4 to 3.6 micrometers. We investigate the interspecimen variability between measurements of two unrelated samples of CaF2, and we also compare our results for Infrasil to previous measurements fo Corning 7980 fused silica. Finally, we provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures and compare those results to other data found in the literature.

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

    SciTech Connect

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

    2014-03-28

    A zoned fishnet metamaterial lens is designed, fabricated, and experimentally demonstrated at millimeter wavelengths to work as a negative near-zero refractive index lens suitable for compact lens antenna configurations. At the design frequency f = 56.7 GHz (λ{sub 0} = 5.29 mm), the zoned fishnet metamaterial lens, designed to have a focal length FL = 9λ{sub 0}, exhibits a refractive index n = −0.25. The focusing performance of the diffractive optical element is briefly compared with that of a non-zoned fishnet metamaterial lens and an isotropic homogeneous zoned lens made of a material with the same refractive index. Experimental and numerically-computed radiation diagrams of the fabricated zoned lens are presented and compared in detail with that of a simulated non-zoned lens. Simulation and experimental results are in good agreement, demonstrating an enhancement generated by the zoned lens of 10.7 dB, corresponding to a gain of 12.26 dB. Moreover, beam steering capability of the structure by shifting the feeder on the xz-plane is demonstrated.

  13. Standing-wave resonances in plasmonic nanoumbrella cavities for color generation and colorimetric refractive index sensor

    NASA Astrophysics Data System (ADS)

    Fan, Jiaorong; Li, Zhongyuan; Chen, Zhuojie; Wu, Wengang

    2016-10-01

    We theoretically investigate the hybridization of the elemental surface plasmons in umbrella-shape plasmonic nanostructures and experimentally demonstrate the implementation of plasmonic multicolor metasurfaces as well as their application in colorimetric sensing. The three-dimension metallic umbrella arrays consist of a periodic canopy-capped-nanopillars with metal-coated sidewall and a backplane metal-film to form vertical nanocavity of canopy and film. Plasmonic coupling and energy confinement in nanocavity induce a noticeably resonance narrowing of multispectral reflection. The metasurfaced nanostructures appeared in vibrant and tunable colors with broad gamut derived from color blending mechanism due to multiple, narrow-band resonances. Vivid colors varied from red, yellow, green, blue to violet are easily achieved. It is also shown that such plasmonic metasurfaces can work as the feasible and real-time colorimetric refractive index sensor by measuring the distinct color variation to glucose concentration changes. Our sensor scheme shows its spectral sensitivity in the periodic umbrella array with respect to the refractive index change to be 242.5 nm/RIU with a figure of merit of 7.3. Furthermore, a refractive index resolution of colorimetric sensing up to 0.025 RIU has been accomplished.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  16. 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.

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

    SciTech Connect

    Lemeshko, Mikhail; Friedrich, Bretislav

    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.

  18. Highly compact refractive index sensor based on stripe waveguides for lab-on-a-chip sensing applications.

    PubMed

    Perera, Chamanei; Vernon, Kristy; Cheng, Elliot; Sathian, Juna; Jaatinen, Esa; Davis, Timothy

    2016-01-01

    In this paper we report the design and experimental realisation of a novel refractive index sensor based on coupling between three nanoscale stripe waveguides. The sensor is highly compact and designed to operate at a single wavelength. We demonstrate that the sensor exhibits linear response with a resolution of 6 × 10(-4) RIU (refractive index unit) for a change in relative output intensity of 1%. Authors expect that the outcome of this paper will prove beneficial in highly compact, label-free and highly sensitive refractive index analysis.

  19. Highly compact refractive index sensor based on stripe waveguides for lab-on-a-chip sensing applications

    PubMed Central

    Perera, Chamanei; Cheng, Elliot; Sathian, Juna; Jaatinen, Esa; Davis, Timothy

    2016-01-01

    Summary In this paper we report the design and experimental realisation of a novel refractive index sensor based on coupling between three nanoscale stripe waveguides. The sensor is highly compact and designed to operate at a single wavelength. We demonstrate that the sensor exhibits linear response with a resolution of 6 × 10−4 RIU (refractive index unit) for a change in relative output intensity of 1%. Authors expect that the outcome of this paper will prove beneficial in highly compact, label-free and highly sensitive refractive index analysis. PMID:27335763

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  1. Retrieval of aerosol refractive index from extinction spectra with a damped harmonic-oscillator band model.

    PubMed

    Thomas, Gareth E; Bass, Stephen F; Grainger, Roy G; Lambert, Alyn

    2005-03-01

    A new method for the retrieval of the spectral refractive indices of micrometer-sized particles from infrared aerosol extinction spectra has been developed. With this method we use a classical damped harmonic-oscillator model of molecular absorption in conjunction with Mie scattering to model extinction spectra, which we then fit to the measurements using a numerical optimal estimation algorithm. The main advantage of this method over the more traditional Kramers-Kronig approach is that it allows the full complex refractive-index spectra, along with the parameters of the particle size distribution, to be retrieved from a single extinction spectrum. The retrieval scheme has been extensively characterized and has been found to provide refractive indices with a maximum uncertainty of approximately 10% (with a minimum of approximately 0.1%). Comparison of refractive indices calculated from measurements of a ternary solution of HNO3, H2SO4, and H2O with those published in J. Phys. Chem. A 104, 783 (2000) show similar differences as found by other authors.

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

    PubMed

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

    2014-01-15

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

  3. Threshold for permanent refractive index change in crystalline silicon by femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Bachman, D.; Chen, Z.; Fedosejevs, R.; Tsui, Y. Y.; Van, V.

    2016-08-01

    An optical damage threshold for crystalline silicon from single femtosecond laser pulses was determined by detecting a permanent change in the refractive index of the material. This index change could be detected with unprecedented sensitivity by measuring the resonant wavelength shift of silicon integrated optics microring resonators irradiated with femtosecond laser pulses at 400 nm and 800 nm wavelengths. The threshold for permanent index change at 400 nm wavelength was determined to be 0.053 ± 0.007 J/cm2, which agrees with previously reported threshold values for femtosecond laser modification of crystalline silicon. However, the threshold for index change at 800 nm wavelength was found to be 0.044 ± 0.005 J/cm2, which is five times lower than the previously reported threshold values for visual change on the silicon surface. The discrepancy is attributed to possible modification of the crystallinity of silicon below the melting temperature that has not been detected before.

  4. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  6. Asymmetric Mach-Zehnder interferometers without an interaction window in polymer foils for refractive index sensing.

    PubMed

    Hofmann, Meike; Xiao, Yanfen; Sherman, Stanislav; Gleissner, Uwe; Schmidt, Thomas; Zappe, Hans

    2016-02-10

    We report on the fabrication and characterization of integrated Mach-Zehnder interferometers in polymer foil without an interaction window. The interferometers are based on inverted rib waveguides, which allow single mode behavior even for waveguide widths larger than a few micrometers. The phase change between the two interferometer arms upon a refractive index change of the analyte that serves as the upper cladding is generated by the asymmetricity of the two interferometer arms. A difference of the waveguide width in the straight part of the interferometer leads to different effective refractive indices and thus to a change in the interference signal. We show in small scale the process chain, which is compatible with a cost-effective roll-to-roll fabrication process. For a proof of principle we apply deionized water and a glucose solution as analytes to the sensor foils and detect the transmitted intensity as a measure of the induced phase change. A detection limit of 3·10⁻³ refractive index units is reached for homogeneous sensing at a total system length of 9.3 mm and a total waveguide core thickness of 3 μm.

  7. Cladding modes in photonic crystal fiber: characteristics and sensitivity to surrounding refractive index

    NASA Astrophysics Data System (ADS)

    Jiang, Xiuli; Gu, Zhengtian; Zheng, Li

    2016-01-01

    Characteristics of cladding modes in a photonic crystal fiber (PCF) with triangular air-hole lattice in the cladding are numerically analyzed using a finite element method. The transition for LP11 cladding mode to core mode with variation of the normalized wavelength has been shown. The transition of the LP01 cladding mode to the outer silica mode and reorganization of the LP0m cladding modes caused by varying the fiber radius has been investigated. By choosing the optimized fiber radius, which is located in the cladding modes' reorganization region, the sensitivity of the coupled wavelength between the core mode LP01 and cladding mode LP03 to surrounding refractive index is increased by a factor of five and reaches to 2660 nm/refractive index unit over the range of 1.40 to 1.42. The sensitivity is competitive with that of long-period grating in PCF in response to changes in refractive indices of the medium contained in the cladding air channels.

  8. The Cryogenic, High-Accuracy, Refraction Measuring System (CHARMS): A New Facility for Cryogenic Infrared through Vacuum Far-Ultraviolet Refractive Index Measurements

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.

    2004-01-01

    The optical designs of future NASA infrared (IR) missions and instruments, such as the James Webb Space Telescope's (JWST) Near-Mixed Camera (NIRCam), will rely on accurate knowledge of the index of refraction of various IR optical materials at cryogenic temperatures. To meet this need, we have developed a Cryogenic, High-Accuracy Refraction Measuring System (CHARMS). In this paper we discuss the completion of the design and construction of CHARMS as well as the engineering details that constrained the final design and hardware implementation. In addition, we will present our first light, cryogenic, IR index of refraction data for LiF, BaF2, and CaF2, and compare our results to previously published data for these materials.

  9. Finite frequency f-sum rule for assessment of number density of gold nanoparticles (AuNPs) and Kramers-Kronig relation for refractive index of colloidal gold.

    PubMed

    Kontturi, Ville; Silfsten, Pertti; Peiponen, Kai-Erik

    2011-07-01

    Absorption spectra from colloids containing different concentrations of spherical gold nanoparticles in water were measured with a spectrophotometer. The absorption spectra were used to calculate the number density of nanoparticles (NPs) with the aid of an unconventional finite spectral band f-sum rule applied for gold colloid. Good correlation between the number density of dispersion electrons, obtained from the f-sum rule, and the number density of nanoparticles was found. The effective absolute refractive index of the gold colloid was obtained with the aid of a singly subtractive Kramers-Kronig relation, and in addition the refractive index change due to the nanoparticles was obtained with the aid of a conventional Kramers-Kronig relation. Such optical properties are valuable in studies of light interaction with nanoparticles.

  10. 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 Δn is about 0.0002, the performances of the former are super to the latter.

  11. A Simple Accurate Alternative to the Minimum-Deviation Method for the Determination of the Refractive Index of a Prism.

    ERIC Educational Resources Information Center

    Waldenstrom, S.; Naqvi, K. Razi

    1978-01-01

    Proposes an alternative to the classical minimum-deviation method for determining the refractive index of a prism. This new "fixed angle of incidence method" may find applications in research. (Author/GA)

  12. Design of acid-lead battery stage-of-charge detection system based on refractive index detection technology

    NASA Astrophysics Data System (ADS)

    Chen, Junyao; Yang, Kecheng; Xia, Min; Li, Lei; Zeng, Xianjiang

    2015-10-01

    Based on optical total reflection critical Angle method, we have designed a refractive index measurement system. It adopted a divergent light source and a CCD camera as the occurrence and receiver of the signal. The divergent light source sent out a bunch of tapered beam, exposure to the interface of optical medium and sulfuric acid solution. Light intensity reflected from the interface could be detected by the CCD camera and then sent to the embedded system. In the DSP embedded system, we could obtain the critical edge position through the light intensity distribution curve and converted it to critical angle. Through experiment, we concluded the relation between liquid refractive index and the critical angle edge position. In this system, the detecting precision of the refractive index of sulfuric acid solution reached 10-4. Finally, through the conversion of the refractive index and density, we achieved high accuracy online measurement of electrolyte density in lead-acid battery.

  13. 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; Zhou, Xianming

    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 (ρ) for shock stress above the Hugoniot elastic limit (HEL): n = 2.0485 (± 0.0197) − 0.0729 (± 0.0043)ρ, 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.

  14. Material Structure of a Graded Refractive Index Lens in Decapod Squid

    NASA Astrophysics Data System (ADS)

    Cai, Jing; Heiney, Paul; Sweeney, Alison

    2013-03-01

    Underwater vision with a camera-type eye that is simultaneously acute and sensitive requires a spherical lens with a graded distribution of refractive index. Squids have this type of lens, and our previous work has shown that its optical properties are likely achieved with radially variable densities of a single protein with multiple isoforms. Here we measure the spatial organization of this novel protein material in concentric layers of the lens and use these data to suggest possible mechanisms of self-assembly of the proteins into a graded refractive index structure. First, we performed small angle x-ray scattering (SAXS) to study how the protein is spatially organized. Then, molecular dynamic simulation allowed us to correlate structure to the possible dynamics of the system in different regions of the lens. The combination of simulation and SAXS data in this system revealed the likely protein-protein interactions, resulting material structure and its relationship to the observed and variable optical properties of this graded index system. We believe insights into the material properties of the squid lens system will inform the invention of self-assembling graded index devices.

  15. Spatial Resolution and Refractive Index Contrast of Resonant Photonic Crystal Surfaces for Biosensing

    PubMed Central

    Triggs, G. J.; Fischer, M.; Stellinga, D.; Scullion, M. G.; Evans, G. J. O.; Krauss, T. F.

    2015-01-01

    By depositing a resolution test pattern on top of a Si3N4 photonic crystal resonant surface, we have measured the dependence of spatial resolution on refractive index contrast Δn. Our experimental results and finite-difference time-domain (FDTD) simulations at different refractive index contrasts show that the spatial resolution of our device reduces with reduced contrast, which is an important consideration in biosensing, where the contrast may be of order 10−2. We also compare 1-D and 2-D gratings, taking into account different incidence polarizations, leading to a better understanding of the excitation and propagation of the resonant modes in these structures, as well as how this contributes to the spatial resolution. At Δn = 0.077, we observe resolutions of 2 and 6 μm parallel to and perpendicular to the grooves of a 1-D grating, respectively, and show that for polarized illumination of a 2-D grating, resolution remains asymmetrical. Illumination of a 2-D grating at 45° results in symmetric resolution. At very low index contrast, the resolution worsens dramatically, particularly for Δn < 0.01, where we observe a resolution exceeding 10 μm for our device. In addition, we measure a reduction in the resonance linewidth as the index contrast becomes lower, corresponding to a longer resonant mode propagation length in the structure and contributing to the change in spatial resolution. PMID:26356353

  16. Concentration dependent refractive index of CO2/CH4 mixture in gaseous and supercritical phase

    NASA Astrophysics Data System (ADS)

    Giraudet, C.; Marlin, L.; Bégué, D.; Croccolo, F.; Bataller, H.

    2016-04-01

    Carbon dioxide (CO2)/methane (CH4) binary mixtures are investigated at pressure values up to 20 MPa at 303 K in order to investigate the pressure dependence of the optical concentration contrast factor, (" separators=" ∂ n / ∂ c ) P , T , through gaseous and supercritical phase. Refractive index is measured by means of a Michelson interferometer. Refractivities of the mixtures are found in good agreement with Lorentz-Lorenz predictions after density calculations by means of the AGA8-DC92 equation of state. Experimental polarizabilities of pure fluids are compared to quantum calculations of monomers and dimers for each pressure; it results that the quantity of dimers is small in the investigated thermodynamic conditions. Finally, by extending our experimental database with numerical simulations, we evidence that (" separators=" ∂ n / ∂ c ) P , T presents a critical enhancement similar to heat capacity.

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

    PubMed Central

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

    2013-01-01

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

  18. 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 μm, 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 μm, 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

  19. 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

    2013-03-26

    This study investigates the CO2 laser-stripped partial cladding of silica-based optic fibers with a core diameter of 400 μm, 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 μm, 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.

  20. Sky-Blue Phosphorescent OLEDs with 34.1% External Quantum Efficiency Using a Low Refractive Index Electron Transporting Layer.

    PubMed

    Shin, Hyun; Lee, Jeong-Hwan; Moon, Chang-Ki; Huh, Jin-Suk; Sim, Bomi; Kim, Jang-Joo

    2016-06-01

    Blue-phosphorescent organic light-emitting diodes (OLEDs) with 34.1% external quantum efficiency (EQE) and 79.6 lm W(-1) are demonstrated using a hole-transporting layer and electron-transporting layer with low refractive index values. Using optical simulations, it is predicted that outcoupling efficiencies with EQEs > 60% can be achieved if organic layers with a refractive index of 1.5 are used for OLEDs.