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Sample records for all-angle negative refraction

  1. Tunable all-angle negative refraction and photonic band gaps in two-dimensional plasma photonic crystals with square-like Archimedean lattices

    SciTech Connect

    Zhang, Hai-Feng E-mail: lsb@nuaa.edu.cn; Liu, Shao-Bin E-mail: lsb@nuaa.edu.cn; Jiang, Yu-Chi

    2014-09-15

    In this paper, the tunable all-angle negative refraction and photonic band gaps (PBGs) in two types of two-dimensional (2D) plasma photonic crystals (PPCs) composed of homogeneous plasma and dielectric (GaAs) with square-like Archimedean lattices (ladybug and bathroom lattices) for TM wave are theoretically investigated based on a modified plane wave expansion method. The type-1 structure is dielectric rods immersed in the plasma background, and the complementary structure is named as type-2 PPCs. Theoretical simulations demonstrate that the both types of PPCs with square-like Archimedean lattices have some advantages in obtaining the higher cut-off frequency, the larger PBGs, more number of PBGs, and the relative bandwidths compared to the conventional square lattices as the filling factor or radius of inserted rods is same. The influences of plasma frequency and radius of inserted rod on the properties of PBGs for both types of PPCs also are discussed in detail. The calculated results show that PBGs can be manipulated by the parameters as mentioned above. The possibilities of all-angle negative refraction in such two types of PPCs at low bands also are discussed. Our calculations reveal that the all-angle negative phenomena can be observed in the first two TM bands, and the frequency range of all-angle negative refraction can be tuned by changing plasma frequency. Those properties can be used to design the optical switching and sensor.

  2. Tunable all-angle negative refraction and photonic band gaps in two-dimensional plasma photonic crystals with square-like Archimedean lattices

    NASA Astrophysics Data System (ADS)

    Zhang, Hai-Feng; Liu, Shao-Bin; Jiang, Yu-Chi

    2014-09-01

    In this paper, the tunable all-angle negative refraction and photonic band gaps (PBGs) in two types of two-dimensional (2D) plasma photonic crystals (PPCs) composed of homogeneous plasma and dielectric (GaAs) with square-like Archimedean lattices (ladybug and bathroom lattices) for TM wave are theoretically investigated based on a modified plane wave expansion method. The type-1 structure is dielectric rods immersed in the plasma background, and the complementary structure is named as type-2 PPCs. Theoretical simulations demonstrate that the both types of PPCs with square-like Archimedean lattices have some advantages in obtaining the higher cut-off frequency, the larger PBGs, more number of PBGs, and the relative bandwidths compared to the conventional square lattices as the filling factor or radius of inserted rods is same. The influences of plasma frequency and radius of inserted rod on the properties of PBGs for both types of PPCs also are discussed in detail. The calculated results show that PBGs can be manipulated by the parameters as mentioned above. The possibilities of all-angle negative refraction in such two types of PPCs at low bands also are discussed. Our calculations reveal that the all-angle negative phenomena can be observed in the first two TM bands, and the frequency range of all-angle negative refraction can be tuned by changing plasma frequency. Those properties can be used to design the optical switching and sensor.

  3. Negative refraction and superconductivity

    NASA Astrophysics Data System (ADS)

    Amariti, Antonio; Forcella, Davide; Mariotti, Alberto; Siani, Massimo

    2011-10-01

    We discuss exotic properties of charged hydrodynamical systems, in the broken superconducting phase, probed by electromagnetic waves. Motivated by general arguments from hydrodynamics, we observe that negative refraction, namely the propagation in opposite directions of the phase velocities and of the energy flux, is expected for low enough frequencies. We corroborate this general idea by analyzing a holographic superconductor in the AdS/CFT correspondence, where the response functions can be explicitly computed. We study the dual gravitational theory both in the probe and in the backreacted case. We find that, while in the first case the refractive index is positive at every frequency, in the second case there is negative refraction at low enough frequencies. This is in agreement with hydrodynamic considerations.

  4. Acoustical Imaging with Negative Refraction

    NASA Astrophysics Data System (ADS)

    Gan, W. S.

    It is well known that the resolution limit of acoustical images is limited by diffraction to λ/2 where λ is the sound wavelength. Negative refraction proposed by Veselago in 1968 shows possibility of defeating the diffraction limit. His work is for electromagnetic waves. Recently it has been shown experimentally that negative refraction can be achieved for both electromagnetic waves and sound waves by using photonic crystals and phononic crystals respectively. John Pendry proposed the concept of `perfect lens' using negative refraction for electromagnetic waves. In this paper, we propose a `perfect lens' for sound waves and an acoustical imaging system incorporating the `perfect lens' is also outlined

  5. Negative refraction in molybdenum disulfide.

    PubMed

    Wang, Wenhui; Cui, Xudong; Yang, Erchan; Fan, Quanping; Xiang, Bin

    2015-08-24

    Recently, negative refractions have been demonstrated in uniaxial crystals with no necessary of negative permittivity and permeability. However, the small anisotropy parameterγin the uniaxial crystals limits the negative refraction occurrence only in a small range of the incident light angle, retarding its practical applications. In this paper, we report negative refraction induced by a pronounced anisotropic behavior in the bulk MoS(2). Using the first-principles, the dielectric function and refractive index calculations confirm a uniaxial trait of MoS(2) with a calculated anisotropy parameterγlarger than 2.5 in the entire range of visible wavelength. The critical incident angle to trigger a negative refraction in the bulk MoS(2) is calculated up to 90°. The finite-difference time-domain simulations prove that the incident light with a density of 59.5% can be negatively refracted in a MoS(2) slab with a thickness of 0.1 µm. Our results open up a new pathway for MoS(2)-like materials to a novel field of optical integration.

  6. Comparisons of Negative Refraction in Left-Handed Materials and Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Feng, Liang; Liu, Xiao-Ping; Ren, Jie; Chen, Yan-Feng; Zhu, Yong-Yuan

    Using the equifrequency surfaces (EFS) to describe negative refractions in left-handed materials (LHMs) and photonic crystals (PCs), negative phase and negative group refractive indexes in LHMs were compared with positive phase and negative group refractive indexes in PCs. The refractive indexes in PCs were dependent on frequencies and incident angles of electromagnetic wave, while indexes in LHMs were constant in the left-handed region. Furthermore, the phase compensating effect resulting from the negative phase refractive index was addressed to distinguish the perfect lens made of LHMs from the superlens realized in the all angle negative refraction (AANR) region of PCs.

  7. The Reality of Negative Refraction

    NASA Astrophysics Data System (ADS)

    Smith, David

    2004-03-01

    Negative refraction, a phenomenon first hypothesized by Victor Veselago in 1968 to occur in materials whose permittivity and permeability are simultaneously negative, has now been confirmed in several independent studies. These experiments demonstrate that it is indeed possible to design and fabricate an artificial material - now known as a "metamaterial" - having an index-of-refraction that is negative over some finite band of frequencies. The positive confirmations of the phenomenon of negative refraction represent an important first step. As applications are considered that take advantage of negative index materials, the ability to meet the needed specifications is the next step, since the viability of applications is ultimately tied to the quality, reproducibility and cost of the underlying materials. Some of the more striking or exotic wave propagation behavior predicted to occur in negative index materials, such as reflectionless compact lenses, near-field refocusing, "perfect" lensing, phase compensation and novel wave-guiding phenomena - place challenging demands on the material parameters. In this talk, I will discuss our efforts to fabricate and characterize negative index metamaterials, and how the current material limitations impact a variety of proposed applications.

  8. Nonlinear negative refraction by difference frequency generation

    NASA Astrophysics Data System (ADS)

    Cao, Jianjun; Shen, Dongyi; Feng, Yaming; Wan, Wenjie

    2016-05-01

    Negative refraction has attracted much interest for its promising capability in imaging applications. Such an effect can be implemented by negative index meta-materials, however, which are usually accompanied by high loss and demanding fabrication processes. Recently, alternative nonlinear approaches like phase conjugation and four wave mixing have shown advantages of low-loss and easy-to-implement, but associated problems like narrow accepting angles can still halt their practical applications. Here, we demonstrate theoretically and experimentally a scheme to realize negative refraction by nonlinear difference frequency generation with wide tunability, where a thin Beta barium borate slice serves as a negative refraction layer bending the input signal beam to the idler beam at a negative angle. Furthermore, we realize optical focusing effect using such nonlinear negative refraction, which may enable many potential applications in imaging science.

  9. 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.

  10. Electromagnetic waves: Negative refraction by photonic crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel

    2004-03-01

    Recently left-handed materials (LHM) attracted great attention since these materials exhibit negative effective index, which is due to simultaneously negative permeability and permittivity. Pendry proposed that negative effective index in left-handed materials can be used for constructing a perfect lens, which is not limited by diffraction(J. B. Pendry, Negative refraction makes a perfect lens, Phys. Rev. Lett. vol. 85, 3966 (2000)). Negative refraction is also achievable in a dielectric photonic crystal (PC) that has a periodically modulated positive permittivity and a permeability of unity. Luo et al. has studied negative refraction and subwavelength imaging in photonic crystals(C. Luo, S. G. Johnson, J. D. Joannopoulos, J. B. Pendry, Subwavelength Imaging in Photonic Crystals Phys. Rev. B 68, 045115 (2003)). In this presentation, we report our experimental and theoretical investigation of negative refraction and subwavelength focusing of electromagnetic waves in a 2D PC. Our structure consists of a square array of dielectric rods in air. Transmission measurements are performed for experimentally verifying the predicted negative refraction behavior in our structure. Negative index of refraction determined from the experiment is -1.94 which is very close to the theoretical value of -2.06. Negative refraction is observed for the incidence angles of > 20°(Ertugrul Cubukcu, Koray Aydin, Ekmel Ozbay, S. Foteinopolou, and Costas Soukoulis, Negative Refraction by Photonic Crystals, Nature, vol. 423, 604 (2003)). Since we know the optimum frequency for a broad angle negative refraction, we can use our crystal to test the superlensing effect that was predicted for negative refractive materials. Scanning transmission measurement technique is used to measure the spatial power distribution of the focused electromagnetic waves that radiate from a point source. Full width at half maximum of the focused beam is measured to be 0.21λ, which is in good agreement with the finite

  11. Negative Refraction experiments in Photonic Crystal prisms

    NASA Astrophysics Data System (ADS)

    Vodo, Plarenta; Parimi, Patanjali. V.; Lu, Wentao. T.; di Gennaro, Emiliano; Sridhar, Srinivas

    2004-03-01

    We have experimentally demonstrated negative refraction in metallic photonic crystal (PC) prisms [1]. The refracted fields in the parallel plate waveguide (PPW) are measured by an automated dipole antenna, which scans the desired area, while the free space (FS) measurements, performed in a anechoic chamber, are measured by a rectangular X-band horn that swings in an arc in far field area. Both TE and TM excitation modes are used in FS experiments. Numerical calculations of the band structure and equi-frequency surface simulations are used to determine frequency regions of negative refraction of the triangular lattice PC. Angle of refraction determined by theoretical simulations and experimental results, are in exceptional good agreement, yielding the negative refraction index. FS and PPW refraction experimental results agree remarkably with simulations. 1. "Negative Refraction and Left-handed electromagnetism in Microwave Photonic Crystals", P.V Parimi, W.T Lu, P.Vodo J. Sokoloff and S.Sridhar, cond-mat/0306109 (2003)

  12. Does negative refraction make a perfect lens?

    NASA Astrophysics Data System (ADS)

    Ramm, A. G.

    2008-10-01

    A discussion of a question, studied earlier by Veselago in 1967 and by Pendry in 2000, is given. The question is: can a slab of the material with negative refraction make a perfect lens? Pendry's conclusion was: yes, it can. Our conclusion is: no, in practice it cannot, because of the fluctuations of the refraction coefficient of the slab. Resolution ability of linear isoplanatic optical instruments is discussed.

  13. Negative Refraction and Imaging with Quasicrystals

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong; Feng, Zhifang; Wang, Yiquan; Li, Zhi-Yuan; Cheng, Bingying; Zhang, Dao-Zhong

    Recently, negative refraction of electromagnetic waves in photonic crystals was demonstrated experimentally and subwavelength images were observed. However, these investigations all focused on the periodic structure. In fact, the negative refraction exists not only in periodic structure, but also in nonperiodic structures such as quasicrystalline arrangement of dielectric. Here, we discuss the negative refraction and imaging based on some transparent quasicrystalline photonic structures. The high-symmetric photonic quasicrystals (PQCs) can exhibit an effective refractive index close to -1 in a certain frequency window. The index shows small spatial dispersion, consistent with the nearly homogeneous geometry of the quasicrystal. Thus, a flat lens based on the 2D PQCs can form a non-near-field image whose position varies with the thickness of the sample and the source distance. At the same time, the focus and image for both polarized waves at the same structure and parameters can also be realized by such a flat lens. In addition, the negative refraction behaviors of acoustic wave in phononic quasicrystal are also discussed.

  14. Negative refraction using Raman transitions and chirality

    SciTech Connect

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

    2011-11-15

    We present a scheme that achieves negative refraction with low absorption in far-off resonant atomic systems. The scheme utilizes Raman resonances and does not require the simultaneous presence of an electric-dipole transition and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman tran-sitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross-coupling. We confirm the validity of the analytical results with exact numerical simulations of the density matrix. We also discuss possible experimental implementations of the scheme in rare-earth metal atomic systems.

  15. Negative refraction in one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Lugo, J. E.; Doti, Rafael; Faubert, J.

    2012-10-01

    Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here, we discuss recent theoretical and simulation results that showed that negative refraction could be present near the low frequency edge of at least the second, fourth and sixth bandgaps of a lossless one-dimensional photonic crystals (1DPC) structure. That is, negative refraction is a multiband phenomenon. We also discuss the negative refraction correctness condition that gives the angular region where negative refraction occurs. We compare two current negative refraction theoretical models with recent experimental results. In order to succeed, an output refraction correction is utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theoretical models in the negative refraction zone.

  16. Nonlinear negative refraction in reorientational soft matter

    NASA Astrophysics Data System (ADS)

    Alberucci, Alessandro; Jisha, Chandroth P.; Assanto, Gaetano

    2015-09-01

    We analyze the propagation of self-trapped optical beams close to the Fréedericksz threshold in nematic liquid crystals. Accounting for power-dependent changes in walk-off due to the all-optical response, we demonstrate that light beams can switch from positive to negative refraction according to the excitation.

  17. Comment on 'Perfect imaging without negative refraction'

    NASA Astrophysics Data System (ADS)

    Blaikie, R. J.

    2010-05-01

    The prediction of 'perfect' imaging without negative refraction for Maxwell's fish-eye lens (Leonhardt U 2009 New J. Phys. 11 093040) is a consequence of imposing an active localized 'drain' at the image point rather than being a general property of the lens. This work then becomes analogous to other work using time-reversal symmetry and/or structured antennae to achieve super-resolution, which can be applied to many types of imaging system beyond the fish-eye lens.

  18. Electrically tunable negative refraction in core/shell-structured nanorod fluids.

    PubMed

    Su, Zhaoxian; Yin, Jianbo; Guan, Yanqing; Zhao, Xiaopeng

    2014-10-21

    We theoretically investigate optical refraction behavior in a fluid system which contains silica-coated gold nanorods dispersed in silicone oil under an external electric field. Because of the formation of a chain-like or lattice-like structure of dispersed nanorods along the electric field, the fluid shows a hyperbolic equifrequency contour characteristic and, as a result, all-angle broadband optical negative refraction for transverse magnetic wave propagation can be realized. We calculate the effective permittivity tensor of the fluid and verify the analysis using finite element simulations. We also find that the negative refractive index can vary with the electric field strength and external field distribution. Under a non-uniform external field, the gradient refraction behavior can be realized. PMID:25087913

  19. Ultrarefraction and negative refraction in metamaterials

    NASA Astrophysics Data System (ADS)

    Maystre, Daniel R.; Enoch, Stefan; Tayeb, Gerard

    2004-07-01

    In the recent years, many experimental and theoretical achievements have shown that meta-materials can simulate homogeneous materials with optical index less than unity or even negative. For example, a dielectric photonic crystal, used at the edge of a band gap, can generate phenomena of ultra-refraction (positive index less than unity) or negative refraction (negative index). Some applications of these phenomena will be shown, specially the design of directive antenna in the microwaves region. More recently, experimental and theoretical studies have been published on left-handed materials. These materials, which have a permittivity and a permeability equal to -1, have been the subject of controversies about their alleged property of making perfect lenses. It will be shown that such a perfect lens cannot exist. However, this kind of meta-material could be used for making better lenses than the best classical ones, a fact which could explain some experimental results. The vital influence of the size of the elementary cell on the performance of the lens will be pointed out. Finally, it will be shown that surprisingly, a left-handed material can be interpreted as a means to go through the mirror, as Alice in the novel of Lewis Carrol...

  20. Negative refraction makes a perfect lens

    PubMed

    Pendry

    2000-10-30

    With a conventional lens sharpness of the image is always limited by the wavelength of light. An unconventional alternative to a lens, a slab of negative refractive index material, has the power to focus all Fourier components of a 2D image, even those that do not propagate in a radiative manner. Such "superlenses" can be realized in the microwave band with current technology. Our simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver. This optical version resolves objects only a few nanometers across.

  1. Negative Refraction Makes a Perfect Lens

    NASA Astrophysics Data System (ADS)

    Pendry, J. B.

    2000-10-01

    With a conventional lens sharpness of the image is always limited by the wavelength of light. An unconventional alternative to a lens, a slab of negative refractive index material, has the power to focus all Fourier components of a 2D image, even those that do not propagate in a radiative manner. Such ``superlenses'' can be realized in the microwave band with current technology. Our simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver. This optical version resolves objects only a few nanometers across.

  2. Electrodynamics of moving media inducing positive and negative refraction

    SciTech Connect

    Grzegorczyk, Tomasz M.; Kong, Jin Au

    2006-07-15

    Negative refraction is a phenomenon that has been recently reported with left-handed media (either isotropic or not), photonic crystals, and rotated uniaxial media. In this Brief Report, we identify another origin of negative refraction, due to the motion of the transmitted medium parallel to the interface at which refraction occurs. Previous works in this domain have concentrated on media velocities that are above the Cerenkov limit, while we show here that negative refraction is in fact achievable at any velocities of the transmitted medium. A possible experimental implementation is proposed to verify this effect. Next, we consider an isotropic frequency-dispersive medium for which the index of refraction can take negative values, and we study the wave refraction phenomenon as a function of frequency and medium velocity. It is found that the motion of the medium induces a rotation of refraction, which can either enhance or attenuate the natural negative refraction of the medium.

  3. Negative-Refraction Metamaterials: Fundamental Principles and Applications

    NASA Astrophysics Data System (ADS)

    Eleftheriades, G. V.; Balmain, K. G.

    2005-06-01

    Learn about the revolutionary new technology of negative-refraction metamaterials Negative-Refraction Metamaterials: Fundamental Principles and Applications introduces artificial materials that support the unusual electromagnetic property of negative refraction. Readers will discover several classes of negative-refraction materials along with their exciting, groundbreaking applications, such as lenses and antennas, imaging with super-resolution, microwave devices, dispersion-compensating interconnects, radar, and defense. The book begins with a chapter describing the fundamentals of isotropic metamaterials in which a negative index of refraction is defined. In the following chapters, the text builds on the fundamentals by describing a range of useful microwave devices and antennas. Next, a broad spectrum of exciting new research and emerging applications is examined, including: Theory and experiments behind a super-resolving, negative-refractive-index transmission-line lens 3-D transmission-line metamaterials with a negative refractive index Numerical simulation studies of negative refraction of Gaussian beams and associated focusing phenomena Unique advantages and theory of shaped lenses made of negative-refractive-index metamaterials A new type of transmission-line metamaterial that is anisotropic and supports the formation of sharp steerable beams (resonance cones) Implementations of negative-refraction metamaterials at optical frequencies Unusual propagation phenomena in metallic waveguides partially filled with negative-refractive-index metamaterials Metamaterials in which the refractive index and the underlying group velocity are both negative This work brings together the best minds in this cutting-edge field. It is fascinating reading for scientists, engineers, and graduate-level students in physics, chemistry, materials science, photonics, and electrical engineering.

  4. Negative refraction characterization in one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Doti, R.; Lugo, J. E.; Faubert, J.

    2012-10-01

    In this work we present two experiments as evidence of negative refraction in one dimensional photonics crystals (1D PC). Particularly the porous silicon (p-Si) multilayer structure is used as 1D PC since this structure presents periodic dielectric components with specific refraction indexes and under certain conditions it can abnormally refract the light. In the first experiment we show the negative refraction for two different wavelengths, one in the visible, and the other in the infrared regions of the spectrum. In this experiment we use a fixed incidence angle for a conditioned white light beam and we look for the emerging negative refracted beam. In the second experiment we characterize de negative refraction observed for the same material by varying the incidence angle in a wide range. The obtained results are compared with a theoretic prediction according a model proposed by the authors [1]. We present a brief description of the material production and its properties, as well.

  5. Caustics in a field negatively refracted at a plane interface.

    PubMed

    Shendeleva, M L

    2008-03-01

    An electromagnetic field radiated by a line source situated near a plane interface between a medium with positive refractive index and a medium with negative refractive index is considered by using the geometrical optics approach. Rays and wave fronts of the refracted field are constructed using Fermat's principle. It is shown that the negatively refracted rays intersecting in pairs create 2-fold caustics that meet at a cusp point. The cusp of the caustic is directed towards the interface for |n| > 1 and away from the interface for |n| < 1, where n is the relative refractive index. It is also shown that wave fronts of the refracted field propagate towards the interface, in the direction from negative to positive optical path lengths. PMID:18331494

  6. A Newtonian approach to extraordinarily strong negative refraction.

    PubMed

    Yoon, Hosang; Yeung, Kitty Y M; Umansky, Vladimir; Ham, Donhee

    2012-08-01

    Metamaterials with negative refractive indices can manipulate electromagnetic waves in unusual ways, and can be used to achieve, for example, sub-diffraction-limit focusing, the bending of light in the 'wrong' direction, and reversed Doppler and Cerenkov effects. These counterintuitive and technologically useful behaviours have spurred considerable efforts to synthesize a broad array of negative-index metamaterials with engineered electric, magnetic or optical properties. Here we demonstrate another route to negative refraction by exploiting the inertia of electrons in semiconductor two-dimensional electron gases, collectively accelerated by electromagnetic waves according to Newton's second law of motion, where this acceleration effect manifests as kinetic inductance. Using kinetic inductance to attain negative refraction was theoretically proposed for three-dimensional metallic nanoparticles and seen experimentally with surface plasmons on the surface of a three-dimensional metal. The two-dimensional electron gas that we use at cryogenic temperatures has a larger kinetic inductance than three-dimensional metals, leading to extraordinarily strong negative refraction at gigahertz frequencies, with an index as large as -700. This pronounced negative refractive index and the corresponding reduction in the effective wavelength opens a path to miniaturization in the science and technology of negative refraction.

  7. Multiple scattering induced negative refraction of matter waves

    PubMed Central

    Pinsker, Florian

    2016-01-01

    Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to ‘untouchable’ quantum systems in analogy to cloaking devices for electromagnetic waves. PMID:26857266

  8. Chirality-induced negative refraction in magnetized plasma

    SciTech Connect

    Guo, B.

    2013-09-15

    Characteristic equations in magnetized plasma with chirality are derived in simple formulations and the dispersion relations for propagation parallel and perpendicular to the external magnetic field are studied in detail. With the help of the dispersion relations of each eigenwave, the author explores chirality-induced negative refraction in magnetized plasma and investigates the effects of parameters (i.e., chirality degree, external magnetic field, etc.) on the negative refraction. The results show that the chirality is the necessary and only one factor which leads to negative refraction without manipulating electrical permittivity and magnetic permeability. Both increasing the degree of chirality and reducing the external magnetic field can result in greater range negative refraction. Parameter dependence of the effects is calculated and discussed.

  9. Multiple scattering induced negative refraction of matter waves.

    PubMed

    Pinsker, Florian

    2016-02-09

    Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to 'untouchable' quantum systems in analogy to cloaking devices for electromagnetic waves.

  10. Multiple scattering induced negative refraction of matter waves.

    PubMed

    Pinsker, Florian

    2016-01-01

    Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to 'untouchable' quantum systems in analogy to cloaking devices for electromagnetic waves. PMID:26857266

  11. 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

  12. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal

    PubMed Central

    Sayem, Ayed Al; Rahman, Md. Masudur; Mahdy, M. R. C.; Jahangir, Ifat; Rahman, Md. Saifur

    2016-01-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene’s 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing. PMID:27146561

  13. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal.

    PubMed

    Sayem, Ayed Al; Rahman, Md Masudur; Mahdy, M R C; Jahangir, Ifat; Rahman, Md Saifur

    2016-05-05

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene's 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing.

  14. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal

    NASA Astrophysics Data System (ADS)

    Sayem, Ayed Al; Rahman, Md. Masudur; Mahdy, M. R. C.; Jahangir, Ifat; Rahman, Md. Saifur

    2016-05-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene’s 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing.

  15. Negative refraction at telecommunication wavelengths through plasmon-photon hybridization.

    PubMed

    Kalusniak, Sascha; Sadofev, Sergey; Henneberger, Fritz

    2015-11-16

    We demonstrate negative refraction at telecommunication wavelengths through plasmon-photon hybridization on a simple microcavity with metallic mirrors. Instead of using conventional metals, the plasmonic excitations are provided by a heavily doped semiconductor which enables us to tune them into resonance with the infrared photon modes of the cavity. In this way, the dispersion of the resultant hybrid cavity modes can be widely adjusted. In particular, negative dispersion and negative refraction at telecommunication wavelengths on an all-ZnO monolithical cavity are demonstrated.

  16. Negative Refraction of Electromagnetic and Electronic Waves in Uniform Media

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Mascarenhas, Angelo

    We discuss various schemes that have been used to realize negative refraction and zero reflection, and the underlying physics that dictates each scheme. The requirements for achieving both negative refraction and zero reflection are explicitly given for different arrangements of the material interface and different structures of the electric permittivity tensor ɛ. We point out that having a lefthanded medium is neither necessary nor sufficient for achieving negative refraction. The fundamental limitations are discussed for using these schemes to construct a perfect lens or "superlens," which is the primary context of the current interest in this field. The ability of an ideal "superlens" beyond diffraction-limit "focusing" is contrasted with that of a conventional lens or an immersion lens.

  17. Negative refraction, subwavelength focusing and beam formation by photonic crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel; Aydin, Koray; Bulu, Irfan; Guven, Kaan

    2007-05-01

    We present a review of our experimental and numerical studies on the negative refraction related phenomena in two-dimensional dielectric photonic crystals (PCs). By employing photonic bands with appropriate dispersion, the propagation of the electromagnetic wave through a PC can be controlled to a large extent, and diverse and completely novel electromagnetic phenomena can be generated. We perform the spectral analysis of the negative refraction arising from a convex TM polarized photonic band of a hexagonal PC. As a consequence of negative refraction, we demonstrate a photonic crystal flat lens, which has the ability to focus electromagnetic waves and provide subwavelength resolution laterally. Finally, a photonic crystal with an embedded source is shown to provide a highly directional beam, which can be utilized in certain antenna applications.

  18. 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.

  19. Dielectric Optical-Controllable Magnifying Lens by Nonlinear Negative Refraction

    PubMed Central

    Cao, Jianjun; Shang, Ce; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Liang, Xiaogan; Wan, Wenjie

    2015-01-01

    A simple optical lens plays an important role for exploring the microscopic world in science and technology by refracting light with tailored spatially varying refractive indices. Recent advancements in nanotechnology enable novel lenses, such as, superlens and hyperlens, with sub-wavelength resolution capabilities by specially designed materials’ refractive indices with meta-materials and transformation optics. However, these artificially nano- or micro-engineered lenses usually suffer high losses from metals and are highly demanding in fabrication. Here, we experimentally demonstrate, for the first time, a nonlinear dielectric magnifying lens using negative refraction by degenerate four-wave mixing in a plano-concave glass slide, obtaining magnified images. Moreover, we transform a nonlinear flat lens into a magnifying lens by introducing transformation optics into the nonlinear regime, achieving an all-optical controllable lensing effect through nonlinear wave mixing, which may have many potential applications in microscopy and imaging science. PMID:26149952

  20. Dielectric Optical-Controllable Magnifying Lens by Nonlinear Negative Refraction.

    PubMed

    Cao, Jianjun; Shang, Ce; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Liang, Xiaogan; Wan, Wenjie

    2015-01-01

    A simple optical lens plays an important role for exploring the microscopic world in science and technology by refracting light with tailored spatially varying refractive indices. Recent advancements in nanotechnology enable novel lenses, such as, superlens and hyperlens, with sub-wavelength resolution capabilities by specially designed materials' refractive indices with meta-materials and transformation optics. However, these artificially nano- or micro-engineered lenses usually suffer high losses from metals and are highly demanding in fabrication. Here, we experimentally demonstrate, for the first time, a nonlinear dielectric magnifying lens using negative refraction by degenerate four-wave mixing in a plano-concave glass slide, obtaining magnified images. Moreover, we transform a nonlinear flat lens into a magnifying lens by introducing transformation optics into the nonlinear regime, achieving an all-optical controllable lensing effect through nonlinear wave mixing, which may have many potential applications in microscopy and imaging science. PMID:26149952

  1. Dielectric Optical-Controllable Magnifying Lens by Nonlinear Negative Refraction

    NASA Astrophysics Data System (ADS)

    Cao, Jianjun; Shang, Ce; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Liang, Xiaogan; Wan, Wenjie

    2015-07-01

    A simple optical lens plays an important role for exploring the microscopic world in science and technology by refracting light with tailored spatially varying refractive indices. Recent advancements in nanotechnology enable novel lenses, such as, superlens and hyperlens, with sub-wavelength resolution capabilities by specially designed materials’ refractive indices with meta-materials and transformation optics. However, these artificially nano- or micro-engineered lenses usually suffer high losses from metals and are highly demanding in fabrication. Here, we experimentally demonstrate, for the first time, a nonlinear dielectric magnifying lens using negative refraction by degenerate four-wave mixing in a plano-concave glass slide, obtaining magnified images. Moreover, we transform a nonlinear flat lens into a magnifying lens by introducing transformation optics into the nonlinear regime, achieving an all-optical controllable lensing effect through nonlinear wave mixing, which may have many potential applications in microscopy and imaging science.

  2. Overlapping illusions by transformation optics without any negative refraction material.

    PubMed

    Sun, Fei; He, Sailing

    2016-01-11

    A novel method to achieve an overlapping illusion without any negative refraction index material is introduced with the help of the optic-null medium (ONM) designed by an extremely stretching spatial transformation. Unlike the previous methods to achieve such an optical illusion by transformation optics (TO), our method can achieve a power combination and reshape the radiation pattern at the same time. Unlike the overlapping illusion with some negative refraction index material, our method is not sensitive to the loss of the materials. Other advantages over existing methods are discussed. Numerical simulations are given to verify the performance of the proposed devices.

  3. 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.

  4. Overlapping illusions by transformation optics without any negative refraction material

    PubMed Central

    Sun, Fei; He, Sailing

    2016-01-01

    A novel method to achieve an overlapping illusion without any negative refraction index material is introduced with the help of the optic-null medium (ONM) designed by an extremely stretching spatial transformation. Unlike the previous methods to achieve such an optical illusion by transformation optics (TO), our method can achieve a power combination and reshape the radiation pattern at the same time. Unlike the overlapping illusion with some negative refraction index material, our method is not sensitive to the loss of the materials. Other advantages over existing methods are discussed. Numerical simulations are given to verify the performance of the proposed devices. PMID:26751285

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Ricci, Michael Christopher

    Artificial materials are media made of inclusions such that the sizes and spacing of the inclusions is much smaller than the incident electromagnetic radiation. This allows a medium to act as an effective bulk medium to electromagnetic radiation. Artificial materials can be tailored to produce desired values of the permittivity, permeability, and index of refraction at specific frequencies. The applications of this tailoring include electromagnetic cloaking, and, theoretically, subwavelength imaging resolution. However, the success of these applications depends on their sensitivity to loss. This research uses superconducting niobium (Nb) metals to create arrays of wires, split-ring resonators, and a combination of wires and split-ring resonators, with very low loss. These arrays are used to investigate properties of a medium with an index of refraction that contains a bandwidth of frequency where the real part is negative. The Nb wire arrays produce a frequency bandwidth with a negative real part of the permittivity, while the Nb split-ring resonators produce a frequency bandwidth with a negative real part of the permeability. The combination of Nb wires and Nb split-ring resonators creates an artificial medium with a negative real part of the index of refraction. The electromagnetic transmission of the wires, split-ring resonators, and combination medium is measured in a waveguide as a function of frequency, and models of the permittivity and permeability are used to fit this data. For a single Nb split-ring resonator, the change in the resonant frequency and quality factor with temperature is measured and fit with a two-fluid model of superconductivity. The change in the resonant frequency and quality factor with an applied dc H field and applied power is also measured and compared to, respectively, magneto-optical imaging and laser scanning photoresponse measurements. Bianisotropy and perturbations in the resonant frequency are investigated, and simulated with

  7. Focusing on Plates: Controlling Guided Waves using Negative Refraction

    PubMed Central

    Philippe, Franck D.; Murray, Todd W.; Prada, Claire

    2015-01-01

    Elastic waves are guided along finite structures such as cylinders, plates, or rods through reflection, refraction, and mode conversion at the interfaces. Such wave propagation is ubiquitous in the world around us, and studies of elastic waveguides first emerged in the later part of the 19th century. Early work on elastic waveguides revealed the presence of backward propagating waves, in which the phase velocity and group velocity are anti-parallel. While backward wave propagation exists naturally in very simple finite elastic media, there has been remarkably little attention paid to this phenomenon. Here we report the development of a tunable acoustic lens in an isotropic elastic plate showing negative refraction over a finite acoustic frequency bandwidth. As compared to engineered acoustic materials such as phononic crystals and metamaterials, the design of the acoustic lens is very simple, with negative refraction obtained through thickness changes rather than internal periodicity or sub-wavelength resonant structures. A new class of acoustic devices, including resonators, filters, lenses, and cloaks, may be possible through topography optimization of elastic waveguide structures to exploit the unique properties of backward waves. PMID:26053960

  8. Focusing on Plates: Controlling Guided Waves using Negative Refraction.

    PubMed

    Philippe, Franck D; Murray, Todd W; Prada, Claire

    2015-06-08

    Elastic waves are guided along finite structures such as cylinders, plates, or rods through reflection, refraction, and mode conversion at the interfaces. Such wave propagation is ubiquitous in the world around us, and studies of elastic waveguides first emerged in the later part of the 19(th) century. Early work on elastic waveguides revealed the presence of backward propagating waves, in which the phase velocity and group velocity are anti-parallel. While backward wave propagation exists naturally in very simple finite elastic media, there has been remarkably little attention paid to this phenomenon. Here we report the development of a tunable acoustic lens in an isotropic elastic plate showing negative refraction over a finite acoustic frequency bandwidth. As compared to engineered acoustic materials such as phononic crystals and metamaterials, the design of the acoustic lens is very simple, with negative refraction obtained through thickness changes rather than internal periodicity or sub-wavelength resonant structures. A new class of acoustic devices, including resonators, filters, lenses, and cloaks, may be possible through topography optimization of elastic waveguide structures to exploit the unique properties of backward waves.

  9. 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.

  10. Theoretical study of negative refractive electromagnetic and acoustic media

    NASA Astrophysics Data System (ADS)

    Li, Tsan Hang

    Negative refractive index material (NIM) is usually treated as a homogeneous medium characterized by a negative permittivity and a negative permeability. They are in fact derived from resonances and as such, their physical properties cannot be exactly identical to an effective homogeneous medium. To understand the importance of the underlying resonances, I constructed models in which negative permittivity and negative permeability can be derived in the long wavelength limit as accurate as one likes within the framework, and then I examined the slab focusing effect to unveil the subtle difference between a truly homogenous left-handed medium and that an effective medium carrying an underlying sub-wavelength structure. I showed that an effective medium that carries hidden microstructures can still serve as a "superlens", but the divergences disappeared and there will also be a natural limit of resolution, as dictated by the details of the underlying resonances (i.e. perfect lens is not possible). The superlens effect is also shown to be a near-field effect. I also showed for the first time that it is possible to have a "double negative" acoustic medium, which is the analog of left-handed electromagnetic medium. The generalization from EM wave to acoustic wave is in fact non-trivial. Such a medium is a composite which has negative mass density and negative bulk modulus, or in other words, it moves to the right when you push to the left and expands when it is compressed. We will see that the double negative acoustic medium may also be realized in practice. I also showed that by mixing NIM with ordinary materials, we can get a new type of photonic band gap which is scale-invariant and insensitive to disorder. Results are presented for 1D and generalized to 3D.

  11. Waves and negative refraction in magnetized plasma with ferrite grains

    SciTech Connect

    Mesfin, Belayneh; Mal'nev, V. N.; Martysh, E. V.; Rapoport, Yu. G.

    2010-11-15

    The propagation of high frequency electromagnetic waves in the low temperature magnetized plasma with ferrite grains (MPFG) is considered. The dispersion properties of MPFG are simultaneously characterized by the permittivity and permeability tensors. The dispersion of the permeability is caused by the high frequency magnetization of the grain subsystem and is important in the vicinity of the frequency of ferromagnetic resonance, which coincides with the electron cyclotron frequency {omega}{sub c}. The MPFG becomes transparent for the waves that cannot propagate in conventional electron-ion magnetized plasma. It is shown that the refractive index of the extraordinary wave propagating along and transversal to the external magnetic field with frequencies close to {omega}{sub c} can be negative as well as positive. For the typical parameters of MPFG, the group velocity of this wave is much smaller than the speed of light. The refractive index of MPFG matched with the free space is obtained for waves propagating at an arbitrary angle with respect to the applied constant magnetic field. The results obtained clearly shows that the dispersion properties of MPFG have all the known properties of left-handed media in the vicinity of {omega}{sub c}.

  12. Polarization beam splitters based on a two-dimensional photonic crystal of negative refraction.

    PubMed

    Ao, Xianyu; He, Sailing

    2005-08-15

    A two-dimensional metallo-dielectric photonic crystal of negative refraction was designed for the application of polarization beam splitters. To match the refractive index of air, the effective refractive index of the designed photonic crystal is -1 for TE polarization and +1 for TM polarization. Two types of polarization beam splitter are presented. PMID:16127940

  13. Negative refraction in one- and two-dimensional lossless plasma dielectric photonic crystals

    SciTech Connect

    Guo, B.

    2013-07-15

    Negative refraction in one- and two-dimensional lossless plasma dielectric photonic crystals consisting of plasma and background materials is theoretically investigated and the necessary conditions for negative refraction in these two structures are obtained. The critical frequency ω{sub 0} and the bandwidth Δω for negative refraction are explored, and the parameter dependence of effects such as plasma filling factor and the dielectric constant of background materials is also examined and discussed.

  14. 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.

  15. Left-handed metamaterials operating in the visible: negative refraction and negative radiation pressure

    NASA Astrophysics Data System (ADS)

    Lezec, Henri

    2009-03-01

    Forty years ago, V. Veselago derived the electromagnetic properties of a hypothetical material having simultaneously-negative values of electric permittivity and magnetic permeability [1]. Such a material, denominated ``left-handed'', was predicted to exhibit a negative index of refraction, as well as a number of other counter-intuitive optical properties. For example, it was hypothesized that a perfect mirror illuminated with a plane wave would experience a negative radiation pressure (pull) when immersed in a left-handed medium, as opposed to the usual positive radiation pressure experienced when facing a dielectric medium such as air or glass. Since left-handed materials are not available in nature, considerable efforts are currently under way to implement them under the form of artificial ``metamaterials'' -- composite media with tailored bulk optical characteristics resulting from constituent structures which are smaller in both size and density than the effective wavelength in the medium. Here we show how surface-plasmon modes propagating in a stacked array of metal-insulator-metal (MIM) waveguides can be harnessed to yield a volumetric left-handed metamaterial characterized by an in-plane-isotropic negative index of refraction over a broad frequency range spanning the blue and green. By sculpting this material with a focused-ion beam we realize prisms and micro-cantilevers which we use to demonstrate, for the first time, (a) in-plane isotropic negative-refraction at optical frequencies, and (b) negative radiation pressure. We predict and experimentally verify a negative ``superpressure'', the magnitude of which exceeds the photon pressure experienced by a perfect mirror by more than a factor of two. 1) V. Veselago, Sov. Phys. Usp. 10, p.509 (1968).

  16. Negative Refraction in a Uniaxial Absorbent Dielectric Material

    ERIC Educational Resources Information Center

    Jen, Yi-Jun; Lakhtakia, Akhlesh; Yu, Ching-Wei; Lin, Chin-Te

    2009-01-01

    Refraction of light from an isotropic dielectric medium to an anisotropic dielectric material is a complicated phenomenon that can have several different characteristics not usually discussed in electromagnetics textbooks for undergraduate students. With a simple problem wherein the refracting material is uniaxial with its optic axis normal to the…

  17. Optical negative refraction by four-wave mixing in thin metallic nanostructures.

    PubMed

    Palomba, Stefano; Zhang, Shuang; Park, Yongshik; Bartal, Guy; Yin, Xiaobo; Zhang, Xiang

    2012-01-01

    The law of refraction first derived by Snellius and later introduced as the Huygens-Fermat principle, states that the incidence and refracted angles of a light wave at the interface of two different materials are related to the ratio of the refractive indices in each medium. Whereas all natural materials have a positive refractive index and therefore exhibit refraction in the positive direction, artificially engineered negative index metamaterials have been shown capable of bending light waves negatively. Such a negative refractive index is the key to achieving a perfect lens that is capable of imaging well below the diffraction limit. However, negative index metamaterials are typically lossy, narrow band, and require complicated fabrication processes. Recently, an alternative approach to obtain negative refraction from a very thin nonlinear film has been proposed and experimentally demonstrated in the microwave region. However, such approaches use phase conjugation, which makes optical implementations difficult. Here, we report a simple but different scheme to demonstrate experimentally nonlinear negative refraction at optical frequencies using four-wave mixing in nanostructured metal films. The refractive index can be designed at will by simply tuning the wavelengths of the interacting waves, which could have potential impact on many important applications, such as superlens imaging.

  18. Optical negative refraction by four-wave mixing in thin metallic nanostructures

    NASA Astrophysics Data System (ADS)

    Palomba, Stefano; Zhang, Shuang; Park, Yongshik; Bartal, Guy; Yin, Xiaobo; Zhang, Xiang

    2012-01-01

    The law of refraction first derived by Snellius and later introduced as the Huygens-Fermat principle, states that the incidence and refracted angles of a light wave at the interface of two different materials are related to the ratio of the refractive indices in each medium. Whereas all natural materials have a positive refractive index and therefore exhibit refraction in the positive direction, artificially engineered negative index metamaterials have been shown capable of bending light waves negatively. Such a negative refractive index is the key to achieving a perfect lens that is capable of imaging well below the diffraction limit. However, negative index metamaterials are typically lossy, narrow band, and require complicated fabrication processes. Recently, an alternative approach to obtain negative refraction from a very thin nonlinear film has been proposed and experimentally demonstrated in the microwave region. However, such approaches use phase conjugation, which makes optical implementations difficult. Here, we report a simple but different scheme to demonstrate experimentally nonlinear negative refraction at optical frequencies using four-wave mixing in nanostructured metal films. The refractive index can be designed at will by simply tuning the wavelengths of the interacting waves, which could have potential impact on many important applications, such as superlens imaging.

  19. Negative refraction with low absorption using Raman transitions with magnetoelectric coupling

    SciTech Connect

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

    2010-07-15

    We suggest a scheme for obtaining negative refraction that does not require the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency. The key idea of the scheme is to obtain a strong electric response by using far-off-resonant Raman transitions. We propose to use a pair of electric-dipole Raman transitions and utilize magneto-electric cross coupling to achieve a negative index of refraction without requiring negative permeability. The interference of the two Raman transitions allows tunable negative refraction with low absorption.

  20. Negative refraction of ultra-cold atoms in optical lattices with nonuniform artificial gauge fields

    NASA Astrophysics Data System (ADS)

    Zhang, Ai-Xia; Xue, Ju-Kui

    2016-07-01

    We theoretically study the reflection and refraction of ultra-cold atoms in optical lattices exposed to a nonuniform artificial magnetic field. The introduction of the nonuniform artificial magnetic field to the optical lattice for suitable designer magnetic potential barrier can lead to a series of intriguing reflection and refraction phenomena of atoms, including reflection, positive refraction, negative refraction and atomic matter wave splitting. Both the occurrence and the distribution of these reflection and refraction scenarios can be coherently controlled by the nonuniform artificial magnetic field. In particular, the regions close to the boundary of reflection demonstrate two more interesting propagation modes, i.e., a reflected branch of atoms comprising a positive or negative refracted branch of atoms with almost same atom population will be excited simultaneously at the magnetic potential barrier. The results can be a guide for the coherent control of the matter waves in optical lattices and the design of new atom optics devices.

  1. Experimental validation of systematically designed acoustic hyperbolic meta material slab exhibiting negative refraction

    NASA Astrophysics Data System (ADS)

    Christiansen, Rasmus E.; Sigmund, Ole

    2016-09-01

    This Letter reports on the experimental validation of a two-dimensional acoustic hyperbolic metamaterial slab optimized to exhibit negative refractive behavior. The slab was designed using a topology optimization based systematic design method allowing for tailoring the refractive behavior. The experimental results confirm the predicted refractive capability as well as the predicted transmission at an interface. The study simultaneously provides an estimate of the attenuation inside the slab stemming from the boundary layer effects—insight which can be utilized in the further design of the metamaterial slabs. The capability of tailoring the refractive behavior opens possibilities for different applications. For instance, a slab exhibiting zero refraction across a wide angular range is capable of funneling acoustic energy through it, while a material exhibiting the negative refractive behavior across a wide angular range provides lensing and collimating capabilities.

  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. Analysis of tunable negative refraction in a lossy and extrinsic semiconductor.

    PubMed

    Chang, Tsung-Wen; Zeng, Yi Min; Wu, Chien-Jang

    2015-02-01

    In this work, within the framework of an inhomogeneous wave, we study the wave transmission at the boundary between air and a lossy extrinsic semiconductor of n-type indium antimonide. Transmission properties such as negative refraction are specifically investigated. The choice of such a semiconductor enables us to study the tunable features in the negative refraction because its permittivity is a function of the frequency, the temperature, and the doping concentration. It is found that there exist a threshold temperature and a threshold frequency in order to obtain the negative refraction. The dependence of threshold temperature on the doping concentration and the operating frequency will be numerically demonstrated. The analysis of negative refraction can be used to study the electromagnetic response for a lossy and extrinsic semiconductor.

  4. Observation of Negative Refraction and Focusing in Two-Dimensional Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel; Bulu, Irfan; Guven, Kaan; Caglayan, Humeyra; Aydin, Koray

    2006-08-01

    We experimentally and theoretically demonstrate the negative refraction and focusing of electromagnetic (EM) waves by two-dimensional photonic crystal slabs at microwave frequencies. The negative refraction is observed both for transverse magnetic (TM) and transverse electric (TE) polarized incident EM waves. Gaussian beam shifting method is used to verify the negative refractive index. The Subwavelength imaging and flat lens behavior of photonic crystals are succesfully demonstrated. We have been able to overcome the diffraction limit and focus the EM waves to a spot size of 0.21λ. Metallodielectric photonic crystals are employed to increase the range of angle of incidence that results in negative refraction. Experimental results and theoretical calculations are in good agreement throughout the work.

  5. Negative refraction and focusing of electromagnetic wave through two-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang-Dong

    2006-12-01

    The negative refraction of electromagnetic waves in photonic crystals was recently demonstrated experimentally, and the physical properties were analyzed. Microsuperlenses based on two-dimensional photonic crystals were designed and the subwavelength images were observed. In this review, after providing a brief history of the research related to the above phenomena, we will summarize our research works in this field including the method of creating a negative refraction region, generating an absolute negative refraction, the focusing of unpolarized electromagnetic waves, and the effect of interface and disorder on the image by the two-dimensional photonic crystal flat lens. The discussion on the negative refraction and the focusing by high symmetric quasicrystals is also presented.

  6. Negative Refraction and Subwavelength Focusing in Two-Dimensional Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel; Ozkan, Gonca

    We experimentally and theoretically demonstrate negative refraction and focusing on electromagnetic (EM) waves by using two-dimensional photonic crystal slabs at microwave frequencies. Negative refraction is observed both for transverse magnetic (TM) and transverse electric (TE) polarized incident EM waves. Gaussian beam shifting method is used to verify negative refractive index. Subwavelength imaging and flat lens behavior of photonic crystals are successfully demonstrated. We have been able to overcome the diffraction limit and focus the EM waves to a spot size of 0.21θ. Metallodielectric photonic crystals are employed to increase the range of angles of incidence that results in negative refraction. Experimental results and theoretical calculations are in good agreement throughout the work.

  7. 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

  8. Optical Refraction in Silver: Counterposition, Negative Phase Velocity and Orthogonal Phase Velocity

    ERIC Educational Resources Information Center

    Naqvi, Qaisar A.; Mackay, Tom G.; Lakhtakia, Akhlesh

    2011-01-01

    Complex behaviour associated with metamaterials can arise even in commonplace isotropic dielectric materials. We demonstrate how silver, for example, can support negative phase velocity and counterposition, but not negative refraction, at optical frequencies. The transition from positive to negative phase velocity is not accompanied by remarkable…

  9. Negative and near zero refraction metamaterials based on permanent magnetic ferrites.

    PubMed

    Bi, Ke; Guo, Yunsheng; Zhou, Ji; Dong, Guoyan; Zhao, Hongjie; Zhao, Qian; Xiao, Zongqi; Liu, Xiaoming; Lan, Chuwen

    2014-02-20

    Ferrite metamaterials based on the negative permeability of ferromagnetic resonance in ferrites are of great interest. However, such metamaterials face a limitation that the ferromagnetic resonance can only take place while an external magnetic field applied. Here, we demonstrate a metamaterial based on permanent magnetic ferrite which exhibits not only negative refraction but also near zero refraction without applied magnetic field. The wedge-shaped and slab-shaped structures of permanent magnetic ferrite-based metamaterials were prepared and the refraction properties were measured in a near-field scanning system. The negative and near zero refractive behaviors are confirmed by the measured spatial electric field maps. This work offers new opportunities for the development of ferrite-based metamaterials.

  10. Metal-Free Flat Lens Using Negative Refraction by Nonlinear Four-Wave Mixing

    NASA Astrophysics Data System (ADS)

    Cao, Jianjun; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Wan, Wenjie

    2014-11-01

    A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical metamaterials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered metamaterials are usually accompanied by high losses from metals and are extremely difficult to fabricate. An alternative proposal using negative refraction by four-wave mixing has attracted much interest recently, though most existing experiments still require metals and none of them have been implemented for an optical lens. Here, we experimentally demonstrate a metal-free flat lens for the first time using negative refraction by degenerate four-wave mixing with a thin glass slide. We realize an optical lensing effect utilizing a nonlinear refraction law, which may have potential applications in microscopy.

  11. Metal-free flat lens using negative refraction by nonlinear four-wave mixing

    NASA Astrophysics Data System (ADS)

    Cao, Jianjun; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Wan, Wenjie

    2014-09-01

    A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical meta-materials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered meta-materials usually company by high losses from metals and are extremely difficult to fabricate. An alternative proposal on using negative refraction by four-wave mixing has attracted much interests recently, though most of existing experiments still require metals and none of them has been implemented for an optical lens. Here we experimentally demonstrate a metalfree flat lens for the first time using negative refraction by degenerate four-wave mixing with a simple thin glass slide. We realize optical lensing utilizing a nonlinear refraction law, which may have potential applications in infrared microscopy and super-resolution imaging.

  12. Metal-free flat lens using negative refraction by nonlinear four-wave mixing.

    PubMed

    Cao, Jianjun; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Wan, Wenjie

    2014-11-21

    A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical metamaterials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered metamaterials are usually accompanied by high losses from metals and are extremely difficult to fabricate. An alternative proposal using negative refraction by four-wave mixing has attracted much interest recently, though most existing experiments still require metals and none of them have been implemented for an optical lens. Here, we experimentally demonstrate a metal-free flat lens for the first time using negative refraction by degenerate four-wave mixing with a thin glass slide. We realize an optical lensing effect utilizing a nonlinear refraction law, which may have potential applications in microscopy.

  13. Negative and near zero refraction metamaterials based on permanent magnetic ferrites

    PubMed Central

    Bi, Ke; Guo, Yunsheng; Zhou, Ji; Dong, Guoyan; Zhao, Hongjie; Zhao, Qian; Xiao, Zongqi; Liu, Xiaoming; Lan, Chuwen

    2014-01-01

    Ferrite metamaterials based on the negative permeability of ferromagnetic resonance in ferrites are of great interest. However, such metamaterials face a limitation that the ferromagnetic resonance can only take place while an external magnetic field applied. Here, we demonstrate a metamaterial based on permanent magnetic ferrite which exhibits not only negative refraction but also near zero refraction without applied magnetic field. The wedge-shaped and slab-shaped structures of permanent magnetic ferrite-based metamaterials were prepared and the refraction properties were measured in a near-field scanning system. The negative and near zero refractive behaviors are confirmed by the measured spatial electric field maps. This work offers new opportunities for the development of ferrite-based metamaterials. PMID:24553188

  14. Metal-free flat lens using negative refraction by nonlinear four-wave mixing.

    PubMed

    Cao, Jianjun; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Wan, Wenjie

    2014-11-21

    A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists. Recent developments in optical metamaterials promise an attractive approach towards perfect lenses using negative refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered metamaterials are usually accompanied by high losses from metals and are extremely difficult to fabricate. An alternative proposal using negative refraction by four-wave mixing has attracted much interest recently, though most existing experiments still require metals and none of them have been implemented for an optical lens. Here, we experimentally demonstrate a metal-free flat lens for the first time using negative refraction by degenerate four-wave mixing with a thin glass slide. We realize an optical lensing effect utilizing a nonlinear refraction law, which may have potential applications in microscopy. PMID:25479522

  15. Negative refractive index and acoustic superlens from multiple scattering in single negative metamaterials.

    PubMed

    Kaina, Nadège; Lemoult, Fabrice; Fink, Mathias; Lerosey, Geoffroy

    2015-09-01

    Metamaterials, man-made composite media structured on a scale much smaller than a wavelength, offer surprising possibilities for engineering the propagation of waves. One of the most interesting of these is the ability to achieve superlensing--that is, to focus or image beyond the diffraction limit. This originates from the left-handed behavior--the property of refracting waves negatively--that is typical of negative index metamaterials. Yet reaching this goal requires the design of 'double negative' metamaterials, which act simultaneously on the permittivity and permeability in electromagnetics, or on the density and compressibility in acoustics; this generally implies the use of two different kinds of building blocks or specific particles presenting multiple overlapping resonances. Such a requirement limits the applicability of double negative metamaterials, and has, for example, hampered any demonstration of subwavelength focusing using left-handed acoustic metamaterials. Here we show that these strict conditions can be largely relaxed by relying on media that consist of only one type of single resonant unit cell. Specifically, we show with a simple yet general semi-analytical model that judiciously breaking the symmetry of a single negative metamaterial is sufficient to turn it into a double negative one. We then demonstrate that this occurs solely because of multiple scattering of waves off the metamaterial resonant elements, a phenomenon often disregarded in these media owing to their subwavelength patterning. We apply our approach to acoustics and verify through numerical simulations that it allows the realization of negative index acoustic metamaterials based on Helmholtz resonators only. Finally, we demonstrate the operation of a negative index acoustic superlens, achieving subwavelength focusing and imaging with spot width and resolution 7 and 3.5 times better than the diffraction limit, respectively. Our findings have profound implications for the

  16. Tunable positive and negative refraction of infrared radiation in graphene-dielectric multilayers

    SciTech Connect

    Zhang, R. Z.; Zhang, Z. M.

    2015-11-09

    Graphene-dielectric multilayers consisting of alternating layers of atom-thick graphene and nanometer-scale dielectric films exhibit characteristics of hyperbolic metamaterials, in which one positive and one negative permittivity are defined for orthogonal directions. Negative permittivity for electric field polarized in the direction parallel to the conductive graphene sheets gives rise to a negative angle of refraction and low-loss transmission for the side-incidence perspective proposed in this work. The Poynting vector tracing demonstrates the switching between positive and negative refraction in the mid-infrared region by tuning the chemical potential of graphene. This adjustable dual-mode metamaterial holds promise for infrared imaging applications.

  17. Negative refraction in a photonic crystal with a metallic cross lattice basis

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

    A metamaterial with a negative effective index of refraction is made from a two-dimensional square lattice photonic crystal with a metallic cross lattice basis. A simple procedure is given to design a negative index band within a desired frequency range. The operating frequency is made sufficiently low so as to avoid high orders of diffraction from a slab. An effective index of -1 , which is a requirement for perfect lensing, is designed. In addition, the structure is optimized to exhibit the largest possible bandwidth of negative refraction, while ensuring an isotropic response and efficient coupling from free space. Simulation results show negative refraction of a Gaussian beam through a prism of such a metamaterial. The simplicity and versatility of the structure make it a suitable candidate for frequencies into the infrared region. The dispersive nature of the metallic crosses and planar fabrication are also discussed.

  18. Negative refraction imaging of acoustic metamaterial lens in the supersonic range

    SciTech Connect

    Han, Jianning; Wen, Tingdun; Yang, Peng; Zhang, Lu

    2014-05-15

    Acoustic metamaterials with negative refraction index is the most promising method to overcome the diffraction limit of acoustic imaging to achieve ultrahigh resolution. In this paper, we use localized resonant phononic crystal as the unit cell to construct the acoustic negative refraction lens. Based on the vibration model of the phononic crystal, negative quality parameters of the lens are obtained while excited near the system resonance frequency. Simulation results show that negative refraction of the acoustic lens can be achieved when a sound wave transmiting through the phononic crystal plate. The patterns of the imaging field agree well with that of the incident wave, while the dispersion is very weak. The unit cell size in the simulation is 0.0005 m and the wavelength of the sound source is 0.02 m, from which we show that acoustic signal can be manipulated through structures with dimensions much smaller than the wavelength of incident wave.

  19. Negative refraction and backward wave in pseudochiral mediums: illustrations of Gaussian beams.

    PubMed

    Chern, Ruey-Lin; Chang, Po-Han

    2013-02-11

    We investigate the phenomena of negative refraction and backward wave in pseudochiral mediums, with illustrations of Gaussian beams. Due to symmetry breaking intrinsic in pseudochiral mediums, there exist two elliptically polarized eigenwaves with different wave vectors. As the chirality parameter increases from zero, the two waves begin to split from each other. For a wave incident from vacuum onto a pseudochiral medium, negative refraction may occur for the right-handed wave, whereas backward wave may appear for the left-handed wave. These features are illustrated with Gaussian beams based on Fourier integral formulations for the incident, reflected, and transmitted waves. Negative refraction and backward wave are manifest, respectively, on the energy flow in space and wavefront movement in time.

  20. Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range

    NASA Astrophysics Data System (ADS)

    Daničić, A.; Radovanović, J.; Ramović, S.; Milanović, V.

    2016-03-01

    In order to avoid losses in metamaterial unit cells at frequencies of interest, caused by metallic inclusions, an active medium design has been proposed. As candidate structures for this active medium, we have chosen quantum cascade lasers because of their high output gain. Here we analyze and compare two quantum cascade structures that emit at 4.6 THz and 3.9 THz, respectively, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all relevant Landau levels, and obtain the necessary information about carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction of the structure. With these data one can determine the conditions under which negative refraction occurs, and calculate the values of the refractive index of the structure, as well as the range of frequencies at which the structure exhibits negative refraction for a predefined total electron sheet density.

  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. 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.

  3. Negative phase velocity and negative refraction in orthorhombic dielectric-magnetic lossy media with polarization along one of principal axes

    NASA Astrophysics Data System (ADS)

    Potisook, Chanin; Natenapit, Mayuree

    2014-05-01

    The characteristics of the TE plane wave propagations in orthorhombic dielectric-magnetic lossy media are investigated. The special case for the electric field being parallel to one principal axis and the wave vector lying wholly in the plane formed by the other two principal axes is considered. The dissipation is taken into account by letting the elements of the permittivity and the permeability tensors to be complex. The general condition on the negative phase velocity for uniform TE plane waves is provided in terms of material parameters and the propagation angle. The numerical calculations for the angles between the average Poynting vector and the phase velocity are performed in order to justify the theoretical analysis. In addition, the TE refraction between the free space and the orthorhombic dielectric-magnetic lossy media are also considered and the general condition on the negative refraction is derived.

  4. A cluster of many small holes with negative imaginary surface impedances may generate a negative refraction index

    NASA Astrophysics Data System (ADS)

    Alsaedi, Ahmed; Ahmad, Bashir; Challa, Durga Prasad; Kirane, Mokhtar; Sini, Mourad

    2016-09-01

    We deal with the scattering of an acoustic medium modeled by an index of refraction $n$ varying in a bounded region $\\Omega$ of $\\mathbb{R}^3$ and equal to unity outside $\\Omega$. This region is perforated with an extremely large number of small holes $D_m$'s of maximum radius $a$, $a<<1$, modeled by surface impedance functions. Precisely, we are in the regime described by the number of holes of the order $M:=O(a^{\\beta-2})$, the minimum distance between the holes is $d\\sim a^t$ and the surface impedance functions of the form $\\lambda_m \\sim \\lambda_{m,0} a^{-\\beta}$ with $\\beta >0$ and $\\lambda_{m,0}$ being constants and eventually complex numbers. Under some natural conditions on the parameters $\\beta, t$ and $\\lambda_{m,0}$, we characterize the equivalent medium generating, approximately, the same scattered waves as the original perforated acoustic medium. We give an explicit error estimate between the scattered waves generated by the perforated medium and the equivalent one respectively, as $a \\rightarrow 0$. As applications of these results, we discuss the following findings: 1. If we choose negative valued imaginary surface impedance functions, attached to each surface of the holes, then the equivalent medium behaves as a passive acoustic medium only if it is an acoustic metamaterial with index of refraction $\\tilde{n}(x)=-n(x),\\; x \\in \\Omega$ and $\\tilde{n}(x)=1,\\; x \\in \\mathbb{R}^3\\setminus{\\overline{\\Omega}}$. This means that, with this process, we can switch the sign of the index of the refraction from positive to negative values. 2. We can choose the surface impedance functions attached to each surface of the holes so that the equivalent index of refraction $\\tilde{n}$ is $\\tilde{n}(x)=1,\\; x \\in \\mathbb{R}^3$. This means that the region $\\Omega$ modeled by the original index of refraction $n$ is approximately cloaked.

  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. Brownian motion in a designer force field: dynamical effects of negative refraction on nanoparticles.

    PubMed

    Cuche, A; Stein, B; Canaguier-Durand, A; Devaux, E; Genet, C; Ebbesen, T W

    2012-08-01

    Photonic crystals (PC) have demonstrated unique features that have renewed the fields of classical and quantum optics. Although holding great promises, associated mechanical effects have proven challenging to observe. We demonstrate for the first time that one of the most salient properties of PC, namely negative refraction, can induce specific forces on metal nanoparticles. By integrating a periodically patterned metal film in a fluidic cell, we show that near-field optical forces associated with negatively refracted surface plasmons are capable of controlling particle trajectories. Coupling particle motions to PC band structures draws new approaches and strategies for parallel and high resolution all-optical control of particle flows with applications for micro- and nanofluidic systems.

  7. 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.

  8. Negative refraction and energy funneling by hyperbolic materials: an experimental demonstration in acoustics.

    PubMed

    García-Chocano, Victor M; Christensen, Johan; Sánchez-Dehesa, José

    2014-04-11

    This Letter reports the design, fabrication, and experimental characterization of hyperbolic materials showing negative refraction and energy funneling of airborne sound. Negative refraction is demonstrated using a stack of five holey Plexiglas plates where their thicknesses, layer separation, hole diameters, and lattice periodicity have been determined to show hyperbolic dispersion around 40 kHz. The resulting hyperbolic material shows a flat band profile in the equifrequency contour allowing the gathering of acoustic energy in a broad range of incident angles and its funneling through the material. Our demonstrations foresee interesting developments based on both phenomena. Acoustic imaging with subwavelength resolution and spot-size converters that harvest and squeeze sound waves irradiating from many directions into a collimated beam are just two possible applications among many.

  9. Negative refraction and localized states of a classical wave in high-symmetry quasicrystals

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong; Zhong, Wei; Feng, Zhifang; Wang, Yiquan; Li, Zhi-Yuan; Zhang, Dao-Zhong

    2011-07-01

    Recently, negative refraction of electromagnetic waves in periodic photonic crystals has been demonstrated experimentally and sub-wavelength images observed. A theoretical and experimental investigation is reported of the electromagnetic wave transport in high-symmetry photonic quasicrystals (QCs). It is shown that negative refraction can appear in these transparent quasicrystalline photonic structures. It is interesting that highly symmetric two-dimensional photonic QCs possess a universal feature for non-near-field focus of two kinds of polarized waves (S wave and P wave). That is, the non-near-field focus for two kinds of polarized waves can be realized by using flat lenses, which consist of some high-symmetric two-dimensional photonic QCs with the same structures and parameters. In addition, some two-dimensional and three-dimensional localized states in defect-free photonic QCs have been found. It is evident that these unusual localized states can be explored by means of electron energy loss spectroscopy.

  10. Negative refraction of elastic waves at the deep-subwavelength scale in a single-phase metamaterial.

    PubMed

    Zhu, R; Liu, X N; Hu, G K; Sun, C T; Huang, G L

    2014-11-24

    Negative refraction of elastic waves has been studied and experimentally demonstrated in three- and two-dimensional phononic crystals, but Bragg scattering is impractical for low-frequency wave control because of the need to scale the structures to manageable sizes. Here we present an elastic metamaterial with chiral microstructure made of a single-phase solid material that aims to achieve subwavelength negative refraction of elastic waves. Both negative effective mass density and modulus are observed owing to simultaneous translational and rotational resonances. We experimentally demonstrate negative refraction of the longitudinal elastic wave at the deep-subwavelength scale in the metamaterial fabricated in a stainless steel plate. The experimental measurements are in good agreement with numerical simulations. Moreover, wave mode conversion related with negative refraction is revealed and discussed. The proposed elastic metamaterial may thus be used as a flat lens for elastic wave focusing.

  11. Far-field self-focusing and -defocusing radiation behaviors of the electroluminescent light sources due to negative refraction.

    PubMed

    Yin, Yu-Feng; Lin, Yen-Chen; Tsai, Tsung-Han; Shen, Yi-Chun; Huang, Jianjang

    2013-01-15

    In recent years, researchers have demonstrated negative refraction theoretically and experimentally by pumping optical power into photonic crystal (PhC) or waveguide structures. The concept of negative refraction can be used to create a perfect lens that focuses an object smaller than the wavelength. By inserting two-dimensional PhCs into the peripheral of a semiconductor light emitting structure, this study presents an electroluminescent device with negative refraction in the visible wavelength range. This approach produces polarization dependent collimation behavior in far-field radiation patterns. The modal dispersion of negative refraction results in strong group velocity modulation, and self-focusing and -defocusing behaviors are apparent from light extraction. This study further verifies experimental results by using theoretic calculations based on equifrequency contours. PMID:23454956

  12. Left-handed materials and negative refraction: Transfer matrix and FDTD calculations

    NASA Astrophysics Data System (ADS)

    Soukoulis, Costas M.

    2004-03-01

    We will present transfer matrix calculations of metallic wires, split ring resonators (SRR) and left-handed materials (LHM). Our results [1] show that the transfer matrix method can capture all the details characteristics of the metamaterials. In particular the dependence of the resonance frequency and its width on the structural parameters of the SRR and the size of the unit cell is studied. Also the dependence of the imaginary part of effective permittivity of arrays of metallic wires is studied in detail. It is found [2,3] that the imaginary part of effective permittivity has small values even for wires as small as 20 micron in diameter. The transfer matrix is very useful in calculating both the amplitude and the phase of the transmission and reflection coefficient. These numerical data was used [4] in the determination of the effective parameters of the metamaterials. It was indeed found that the refractive index was unambiguously negative in the frequency region where both ɛ and μ were negative. Finally, we will show that SRR have a strong electric response, equivalent to that of cut wires [5], which dominates the response of LHM. A new criterion is introduced to clearly identify if an experimental expression peak is left- or right handed. Finite difference time domain (FDTD) simulations will be presented for the transmission of the EM wave through the interface of the positive and negative refraction index. It is found [6] that the wave is trapped temporarily at the interface and after a long time the wave front moves eventually in the direction of negative refraction. The differences between negative refraction in photonic crystals and left-handed materials will be also discussed. Work supported by US-DOE, DARPA, NSF and EU (DALHM project). References: [1] P. Markos and C. M. Soukoulis, Phys. Rev. B 65, 033401 (2002); Phys. Rev. E 65, 036622 (2002). [2] P. Markos, I. Rousochatzakis and C. M. Soukoulis, Phys. Rev. B 66, 045601 (2002). [3] P. Markos and C. M

  13. Optic-null space medium for cover-up cloaking without any negative refraction index materials

    PubMed Central

    Sun, Fei; He, Sailing

    2016-01-01

    With the help of optic-null medium, we propose a new way to achieve invisibility by covering up the scattering without using any negative refraction index materials. Compared with previous methods to achieve invisibility, the function of our cloak is to cover up the scattering of the objects to be concealed by a background object of strong scattering. The concealed object can receive information from the outside world without being detected. Numerical simulations verify the performance of our cloak. The proposed method will be a great addition to existing invisibility technology. PMID:27383833

  14. Optic-null space medium for cover-up cloaking without any negative refraction index materials.

    PubMed

    Sun, Fei; He, Sailing

    2016-01-01

    With the help of optic-null medium, we propose a new way to achieve invisibility by covering up the scattering without using any negative refraction index materials. Compared with previous methods to achieve invisibility, the function of our cloak is to cover up the scattering of the objects to be concealed by a background object of strong scattering. The concealed object can receive information from the outside world without being detected. Numerical simulations verify the performance of our cloak. The proposed method will be a great addition to existing invisibility technology.

  15. Triangular lattice of carbon nanotube arrays for negative index of refraction and subwavelength lensing effect

    SciTech Connect

    Wang, Y.; Wang, X.; Rybczynski, J.; Wang, D.Z.; Kempa, K.; Ren, Z.F.

    2005-04-11

    Self-assembly of polystyrene microspheres has been utilized in a two-step masking technique to prepare triangular lattices of catalytic nanodots at low cost. Subsequent triangular lattices of aligned carbon nanotubes on a silicon substrate are achieved by plasma-enhanced chemical vapor deposition. Nickel is used both in the nanodots and in the secondary mask. The triangular lattices of carbon nanotube arrays as two-dimensional photonic crystals show higher geometrical symmetry than the hexagonal lattices previously reported, enabling broader applications including negative index of refraction and subwavelength lensing effect.

  16. Low-loss and high-symmetry negative refractive index media by hybrid dielectric resonators.

    PubMed

    Lai, Yueh-Chun; Chen, Cheng-Kuang; Yang, Yu-Hang; Yen, Ta-Jen

    2012-01-30

    Based on Maxwell's equations and Mie theory, strong sub-wavelength artificial magnetic and electric dipole resonances can be excited within dielectric resonators, and their resonant frequencies can be tailored simply by scaling the size of the dielectric resonators. Therefore, in this work we hybridize commercially available zirconia and alumina structures to harvest their individual artificial magnetic and electric response simultaneously, presenting a negative refractive index medium (NRIM). Comparing with the conventional NRIM constructed by metallic structures, the demonstrated all-dielectric NRIM possesses low-loss and high-symmetry advantages, thus benefiting practical applications in communication components, perfect lenses, invisible cloaking and other novel electromagnetic devices. PMID:22330524

  17. Optic-null space medium for cover-up cloaking without any negative refraction index materials

    NASA Astrophysics Data System (ADS)

    Sun, Fei; He, Sailing

    2016-07-01

    With the help of optic-null medium, we propose a new way to achieve invisibility by covering up the scattering without using any negative refraction index materials. Compared with previous methods to achieve invisibility, the function of our cloak is to cover up the scattering of the objects to be concealed by a background object of strong scattering. The concealed object can receive information from the outside world without being detected. Numerical simulations verify the performance of our cloak. The proposed method will be a great addition to existing invisibility technology.

  18. 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.

  19. Hidden quantum mirage by negative refraction in semiconductor P-N junctions

    NASA Astrophysics Data System (ADS)

    Zhang, Shu-Hui; Zhu, Jia-Ji; Yang, Wen; Lin, Hai-Qing; Chang, Kai

    2016-08-01

    We predict a robust quantum interference phenomenon in a semiconductor P-N junction: with a local pump on one side of the junction, the response of a local probe on the other side behaves as if the disturbance emanates not from the pump but instead from its mirror image about the junction. This phenomenon follows from the matching of Fermi surfaces of the constituent materials, thus it is robust against the details of the junction (e.g., width, potential profile, and even disorder), in contrast to the widely studied anomalous focusing caused by negative refraction. The recently fabricated P-N junctions in 2D semiconductors provide ideal platforms to explore this phenomenon and its applications to dramatically enhance charge and spin transport as well as carrier-mediated long-range correlation.

  20. Negative Refraction, Light Pressure and Attraction, Equation E = mc2 and Wave-particle Dualism

    NASA Astrophysics Data System (ADS)

    Veselago, Victor G.

    2010-10-01

    The process of mass transfer from the emitter to the receiver is considered for different connection between energy and momentum. Shown, in particular, that in the case when the energy is transferred by radiation, this relationship has the form E = mvphvgr, where vph—phase velocity, and vgr -group velocity. From this equation immediately shows that in media with negative refraction radiation transfers the mass not from the transmitter to receiver, but rather from the receiver to the transmitter. It follows, that the mass transferred from the transmitter to the receiver is determined not only by transferred energy, but also by transferred linear momentum, which may be associated with energy in different ways. Thus, the well-known relation E = mc2 is a special case of E = mvphvgr.

  1. Nonlinear waves in an array of zigzag waveguides with alternating positive and negative refractive indices

    SciTech Connect

    Kazantseva, E V; Maimistov, A I

    2013-09-30

    Interaction of coupled waves propagating in a system of waveguides with alternating positive and negative refractive indices is studied theoretically. The zigzag configuration of the waveguides in the array allows communication not only between the nearest neighbours, but also with the waveguides beyond them. It is shown that the spectrum of linear waves in such a waveguide system has a bandgap. Partial solutions are found to the system of coupled waves corresponding to a stationary electromagnetic field pulse that propagates along the array of tunnel-coupled waveguides as a whole. Investigation of the interaction of nonlinear solitary waves has demonstrated numerically the stability of their relatively weak disturbances and collisions with each other. (nanogradient dielectric coatings and metamaterials)

  2. Nano-optic label-free biosensors based on photonic crystal platform with negative refraction

    NASA Astrophysics Data System (ADS)

    Aroua, W.; Haxha, S.; AbdelMalek, F.

    2012-04-01

    In this paper, a novel biosensor based on hetero photonic crystal (PC) structures is proposed. The biosensor consists of photonic crystals with negative refraction (PCNR) embedded between two ordinary PC structures. The PCNR is employed in order to produce an image that is as similar as the light source, which is located in the first ordinary PC. Significant enhancement of the image is achieved when a nanocavity is introduced into the PCNR. It is found that the transmission peak shifts when the nanocavity is filled with blood plasma, liquid and dry air. It is shown that by careful selection of the radius of the nanocavity, the sensitivity of the proposed biosensor can be enhanced. The presented PCNR biosensor is investigated by employing the finite-difference time-domain method (FDTD).

  3. Local decomposition of solid solutions, nanostructures and optical materials with negative refractive index

    NASA Astrophysics Data System (ADS)

    Ishchuk, Valeriy M.; Sobolev, Vladimir

    2016-03-01

    In this paper, a possibility of use of the controlled decomposition of solid solutions of oxides with perovskite structure in the state of coexisting domains of the antiferroelectric (AFE) and ferroelectric (FE) phases for manufacturing materials with the negative refractive index is demonstrated. The lead zirconate titanate-based solid solutions are considered as an example of substances suitable for creation of such materials. Manufactured composites constitute a dielectric AFE matrix with a structure of conducting interphase boundaries separating domains of the FE and AFE phases. The electric conductivity of the interphase boundaries occurs as a result of the local decomposition of the solid solutions in the vicinity of these boundaries. The decomposition process and consequently the conductivity of the interphase boundaries can be controlled by means of external influences.

  4. Influence of surface termination on inverse Goos–Hänchen shift of negatively refractive photonic crystals

    NASA Astrophysics Data System (ADS)

    Hu, Jinbing; Liang, Binming; Chen, Jiabi; Cai, Xiaoshu; Jiang, Qiang; Zhuang, Songlin

    2016-07-01

    The effect of surface termination on the inverse Goos–Hänchen (GH) shift of two-dimensional (2D) negatively refractive photonic crystals (NRPhCs) containing air holes arranged in a hexagonal lattice in a dielectric background is investigated for transverse magnetic (TM) polarization. Results show that the magnitude of the inverse GH shift of 2D-NRPhCs strongly depends on surface termination even for an incident beam with a fixed frequency and incidence angle. Calculation of dispersion of surface mode as a function of termination reveals that large inverse GH shift of 2D-NRPhCs results from the excitation of backward surface mode. In addition, the coupling coefficient of the incident field into the field of surface mode and energy flux around the interface are studied and demonstrate the above conclusion. This paper will provide technical information regarding the combination of various functional photonic elements in the design of integrated optical circuits.

  5. 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.

  6. Zero absorption and a large negative refractive index in a left-handed four-level atomic medium

    NASA Astrophysics Data System (ADS)

    Zhao, Shuncai; Liu, Zhengdong; Wu, Qixuan

    2010-02-01

    In this paper, we have investigated three external fields interacting with the four-level atomic system described by the density-matrix approach. The atomic system exhibits left-handedness with zero absorption and large negative refractive index. Varying the parameters of the three external fields, the properties of zero absorption and large negative refractive index from the atomic system remain unvarying. Our scheme proposes an approach to obtain a negative refractive medium with zero absorption. The zero absorption property of the atomic system may be used to amplify the evanescent waves that have been lost in the imaging by traditional lenses, and a slab fabricated by the left-handed atomic system may be an ideal candidate for designing perfect lenses.

  7. Negative Index Refraction in the Complex Ginzburg—Landau Equation in Connection with the Experimental CIMA Reaction

    NASA Astrophysics Data System (ADS)

    Yuan, Xu-Jin

    2012-09-01

    In comparison with the phenomenon of negative index refraction observed in artificial meta-materials, it is interesting to ask if this type of behavior also exists or not in reaction-diffusion systems that support nonlinear chemical waves. Previous studies indicate that the negative index refraction could occur on a interface between a medium of a normal wave and a medium that supports anti-waves. Here we investigate the phenomenon in the complex Ginzburg—Landau equation (CGLE) in a close relationship with the quantitative model for the chloriteiodide-malonic acid (CIMA) reaction. The amplitude equation CGLE is deduced from the CIMA reaction, and simulations with mapped parameters from the reaction-diffusion equation reveal that the competition between normal waves and anti-waves on the interface determines whether the negative index refraction occurs or not.

  8. 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

  9. Broad self-trapped and slow light bands based on negative refraction and interference of magnetic coupled modes.

    PubMed

    Fang, Yun-Tuan; Ni, Zhi-Yao; Zhu, Na; Zhou, Jun

    2016-01-13

    We propose a new mechanism to achieve light localization and slow light. Through the study on the coupling of two magnetic surface modes, we find a special convex band that takes on a negative refraction effect. The negative refraction results in an energy flow concellation effect from two degenerated modes on the convex band. The energy flow concellation effect leads to forming of the self-trapped and slow light bands. In the self-trapped band light is localized around the source without reflection wall in the waveguide direction, whereas in the slow light band, light becomes the standing-waves and moving standing-waves at the center and the two sides of the waveguide, respectively. PMID:26647772

  10. Negative index of refraction in a four-level system with magnetoelectric cross coupling and local field corrections

    SciTech Connect

    Bello, F.

    2011-07-15

    This research focuses on a coherently driven four-level atomic medium with the aim of inducing a negative index of refraction while taking into consideration local field corrections as well as magnetoelectric cross coupling (i.e.,chirality) within the material's response functions. Two control fields are used to render the medium transparent for a probe field which simultaneously couples to an electric and a magnetic dipole transition, thus allowing one to test the permittivity and permeability of the material at the same time. Numerical simulations show that a negative index of refraction with low absorption can be obtained for a range of probe detunings while depending on number density and the ratio between the intensities of the control fields.

  11. Broad self-trapped and slow light bands based on negative refraction and interference of magnetic coupled modes.

    PubMed

    Fang, Yun-Tuan; Ni, Zhi-Yao; Zhu, Na; Zhou, Jun

    2016-01-13

    We propose a new mechanism to achieve light localization and slow light. Through the study on the coupling of two magnetic surface modes, we find a special convex band that takes on a negative refraction effect. The negative refraction results in an energy flow concellation effect from two degenerated modes on the convex band. The energy flow concellation effect leads to forming of the self-trapped and slow light bands. In the self-trapped band light is localized around the source without reflection wall in the waveguide direction, whereas in the slow light band, light becomes the standing-waves and moving standing-waves at the center and the two sides of the waveguide, respectively.

  12. 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

  13. Modulation instability in a zigzag array of nonlinear waveguides with alternating positive and negative refractive indices

    SciTech Connect

    Dovgiy, A A

    2014-12-31

    The modulation instability is analytically investigated in a zigzag array of tunnel-coupled optical waveguides with alternating refractive indices and Kerr nonlinearity. Particular solutions to a system of coupled nonlinear equations are found. They describe the propagation of electromagnetic waves that are uniform along the waveguide and their instability is studied. It is shown that the coupling coefficient between the waveguides, which are non-nearest neighbours, has a significant effect on the instability of the waves in question. When the coupling coefficient exceeds a certain threshold, the modulation instability disappears regardless of the radiation power. The influence of the ratio of the wave amplitudes in adjacent waveguides to the instability of the particular solutions is studied. Different variants of the nonlinear response in waveguides are considered. The studies performed present a new unusual type of the modulation instability in nonlinear periodic systems. (metamaterials)

  14. Focusing analysis of a complex photonic crystal slab with negative refraction

    NASA Astrophysics Data System (ADS)

    Wang, Hung-Wen; Wu, Mei-Ling; Chen, Lien-Wen

    2010-10-01

    The electromagnetic wave propagation in a two-dimensional (2D) complex triangular photonic crystal (PC) consisting of dielectric cylinders of different radii in air is investigated. The plane wave expansion (PWE) and finite element (FE) methods are used to study the optical and focusing properties of the complex PC. Interestingly, in contrast to a triangular PC consisting of dielectric cylinders of the same radius, the complex PC can generate a focusing effect with an effective refractive index of -1. Furthermore, a design is proposed using antireflection structures to enhance the transmission efficiency of light at the interfaces between the air and the PC slab. Numerical simulations show that appropriately adding antireflection structures to the surface of the slab can greatly improve the focusing resolution.

  15. Quantum-interference and the concentration of Er3+ ion effect on left-handedness with zero absorption and large negative refractive index in Er3+:YAG crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Huifang; Ren, Haihong; Yan, Xiaona; Bai, Lihua

    2012-07-01

    The electromagnetically induced left-handedness with zero absorption and large negative refractive index was investigated in a solid Er3+:YAG crystal with a four-level system proposed for an atomic medium. It was found that the frequency region with simultaneous negative permittivity and negative permeability, the zero absorption intervals, and the maximum values of the negative refractive index can be adjusted by changing the signal field, the coherent field, as well as the concentration of Er3+ ion in crystal. It is shown that wider zero absorption intervals with a higher index of refraction can be easily obtained when the signal field is only off resonance. The slab fabricated by the left-handed solid medium Er3+:YAG crystal with zero absorption may be a practical candidate for designing perfect lenses.

  16. Simultaneous negative refraction and focusing of fundamental frequency and second-harmonic fields by two-dimensional photonic crystals

    SciTech Connect

    Zhang, Jun; Zhang, Xiangdong

    2015-09-28

    Simultaneous negative refraction for both the fundamental frequency (FF) and second-harmonic (SH) fields in two-dimensional nonlinear photonic crystals have been found through both the physical analysis and exact numerical simulation. By combining such a property with the phase-matching condition and strong second-order susceptibility, we have designed a SH lens to realize focusing for both the FF and SH fields at the same time. Good-quality non-near field images for both FF and SH fields have been observed. The physical mechanism for such SH focusing phenomena has been disclosed, which is different from the backward SH generation as has been pointed out in the previous investigations. In addition, the effect of absorption losses on the phenomena has also been discussed. Thus, potential applications of these phenomena to biphotonic microscopy technique are anticipated.

  17. Focus modulation of cylindrical vector beams by using 1D photonic crystal lens with negative refraction effect.

    PubMed

    Xu, Ji; Zhong, Yi; Wang, Shengming; Lu, Yunqing; Wan, Hongdan; Jiang, Jian; Wang, Jin

    2015-10-19

    Sub-wavelength focusing of cylindrical vector beams (CVBs) has attracted great attention due to the specific physical effects and the applications in many areas. More powerful, flexible and effective ways to modulate the focus transversally and also longitudinally are always being pursued. In this paper, cylindrically symmetric lens composed of negative-index one-dimensional photonic crystal is proposed to make a breakthrough. By revealing the relationship between focal length and the exit surface shape of the lens, a quite simple and effective principle of designing the lens structure is presented to realize specific focus modulation. Plano-concave lenses are parameterized to modulate the focal length and the number of focuses. An axicon constructed by one-dimensional photonic crystal is proposed for the first time to obtain a large depth of focus and an optical needle focal field with almost a theoretical minimum FWHM of 0.362λ is achieved under radially polarized incident light. Because of the almost identical negative refractive index for TE and TM polarization states, all the modulation methods can be applied for any arbitrary polarized CVBs. This work offers a promising methodology for designing negative-index lenses in related application areas. PMID:26480359

  18. Negative refraction induced acoustic concentrator and the effects of scattering cancellation, imaging, and mirage

    NASA Astrophysics Data System (ADS)

    Wei, Qi; Cheng, Ying; Liu, Xiao-jun

    2012-07-01

    We present a three-dimensional acoustic concentrator capable of significantly enhancing the sound intensity in the compressive region with scattering cancellation, imaging, and mirage effects. The concentrator shell is built by isotropic gradient negative-index materials, which together with an exterior host medium slab constructs a pair of complementary media. The enhancement factor, which can approach infinity by tuning the geometric parameters, is always much higher than that of a traditional concentrator made by positive-index materials with the same size. The acoustic scattering theory is applied to derive the pressure field distribution of the concentrator, which is consistent with the numerical full-wave simulations. The inherent acoustic impedance match at the interfaces of the shell as well as the inverse processes of “negative refraction—progressive curvature—negative refraction” for arbitrary sound rays can exactly cancel the scattering of the concentrator. In addition, the concentrator shell can also function as an acoustic spherical magnifying superlens, which produces a perfect image with the same shape, with bigger geometric and acoustic parameters located at a shifted position. Then some acoustic mirages are observed whereby the waves radiated from (scattered by) an object located in the center region may seem to be radiated from (scattered by) its image. Based on the mirage effect, we further propose an intriguing acoustic transformer which can transform the sound scattering pattern of one object into another object at will with arbitrary geometric, acoustic, and location parameters.

  19. Suppression of spontaneous emission and superradiance over macroscopic distances in media with negative refraction

    NASA Astrophysics Data System (ADS)

    Kästel, Jürgen; Fleischhauer, Michael

    2005-01-01

    The possibility of negative optical path length in left-handed media (LHM) is shown to lead to complete suppression of spontaneous emission of an atom in front of a mirror with a layer of LHM. For the same reason two atoms put at the foci of a perfect lens formed by a parallel LHM slab [J. B. Pendry, Phys. Rev. Lett.8520003966] exhibit perfect subradiance and superradiance. It is shown that these effects occur over distances that can be orders of magnitude larger than the transition wavelength and are only limited by the propagation length within the free-space decay time of the atoms. Single- and two-atom decay rates are calculated from the Greens function of the electric field in the presence of a LHM and limitations as well as potential applications are discussed.

  20. Transmission of evanescent wave modes through a slab of negative-refractive-index material.

    PubMed

    de Wolf, David A

    2011-02-01

    There has been a long-standing argument about Pendry's suggestion that a plane harmonic evanescent (surface) wave along the interface between free space and a slab of ɛ=-1, μ=-1 double-negative (DNG) medium will emerge on the far side with recovery of phase and amplitude. While this is possible, it is subject to parameter restrictions. This work generalizes previous work and now gives analytical criteria for when to expect such a recovery in a Smith-Kroll DNG medium. Basically this requires, among other things, a relatively narrow bandwidth and relatively small transverse-mode component. There also is a very strong dependence on the ratio of slabwidth to plasma wavelength.

  1. Suppression of spontaneous emission and superradiance over macroscopic distances in media with negative refraction

    SciTech Connect

    Kaestel, Juergen; Fleischhauer, Michael

    2005-01-01

    The possibility of negative optical path length in left-handed media (LHM) is shown to lead to complete suppression of spontaneous emission of an atom in front of a mirror with a layer of LHM. For the same reason two atoms put at the foci of a perfect lens formed by a parallel LHM slab [J. B. Pendry, Phys. Rev. Lett. 85, 3966 (2000)] exhibit perfect subradiance and superradiance. It is shown that these effects occur over distances that can be orders of magnitude larger than the transition wavelength and are only limited by the propagation length within the free-space decay time of the atoms. Single- and two-atom decay rates are calculated from the Greens function of the electric field in the presence of a LHM and limitations as well as potential applications are discussed.

  2. Refocusing resolution based on negative refractive-photonic crystal group with Ag defects for target detection and imaging

    NASA Astrophysics Data System (ADS)

    Lian, Yingfei; Zhu, Na; Fang, Yuntuan; Sun, Jiwen; Chen, Junlv; Qian, Huili

    2015-03-01

    Negative refractive-photonic crystal (NR-PC) lenses that can exceed the diffraction limit of focus resolution for imaging and target detection in the near field have gotten more and more special attention in recent years. Three flat lens groups with Ag defects based on NR-PC are designed, and the focusing imaging in the NR-PC three flat lens groups is concluded with the extension of Snell's law, and the influence on the resolution for a target detection dynamic scanning scheme is simulated by using the finite difference time domain method. An optimal-doped structure with Ag defects is achieved by different simulation combinations. The refocusing resolution 0.18834λ is achieved in the optimal structure and there is approximately a 0.06806λ improvement in the refocusing resolution compared to those undoped with Ag (0.2564λ) it also possesses distinct smaller side-lobes than a single flat lens doped with Ag. This means the optimal detecting ability for the three NR-PC flat lens groups with Ag defects is more improved than that for a single undoped and doped with Ag. This is significant for the perfect imaging being achieved for a particle structure.

  3. A physical explanation for the all-angle reflectionless property of transformation optics designs

    NASA Astrophysics Data System (ADS)

    Gok, Gurkan; Grbic, Anthony

    2016-04-01

    In this paper, the all-angle reflectionless property of transformation optics devices is analyzed, and a physical explanation is provided for it. To this end, plane wave propagation through a planar boundary separating two homogenous, lossless magnetically anisotropic media is studied. The general form of material parameters enabling an all-angle reflectionless transmission of electromagnetic waves through the boundary is derived. Similarities are drawn between this general form of all-angle reflectionless material parameters and those observed in transformation optics designs. The findings are verified through full-wave simulation. Furthermore, a physical explanation as to why the general form of anisotropic material parameters are reflectionless for all angle of incidences is provided. This work provides an intuitive understanding of the inherent reflectionless property of transformation optics devices, and may find applications in designing reflectionless media to control electromagnetic waves without the use of coordinate transformations.

  4. Fundamentals of negative refractive index optical trapping: forces and radiation pressures exerted by focused Gaussian beams using the generalized Lorenz-Mie theory

    PubMed Central

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

    2010-01-01

    Based on the generalized Lorenz-Mie theory (GLMT), this paper reveals, for the first time in the literature, the principal characteristics of the optical forces and radiation pressure cross-sections exerted on homogeneous, linear, isotropic and spherical hypothetical negative refractive index (NRI) particles under the influence of focused Gaussian beams in the Mie regime. Starting with ray optics considerations, the analysis is then extended through calculating the Mie coefficients and the beam-shape coefficients for incident focused Gaussian beams. Results reveal new and interesting trapping properties which are not observed for commonly positive refractive index particles and, in this way, new potential applications in biomedical optics can be devised. PMID:21258549

  5. Tailoring the negative-refractive-index metamaterials composed of semiconductor-metal-semiconductor gold ring/disk cavity heptamers to support strong Fano resonances in the visible spectrum.

    PubMed

    Ahmadivand, Arash; Pala, Nezih

    2015-02-01

    In this study, we investigated numerically the plasmon response of a planar negative-index metamaterial composed of symmetric molecular orientations of Au ring/disk nanocavities in a heptamer cluster. Using the plasmon hybridization theory and considering the optical response of an individual nanocluster, we determined the accurate geometrical sizes for a ring/disk nanocavity heptamer. It is shown that the proposed well-organized nanocluster can be tailored to support strong and sharp Fano resonances in the visible spectrum. Surrounding and filling the heptamer clusters by various metasurfaces with different chemical characteristics, and illuminating the structure with an incident light source, we proved that this configuration reflects low losses and isotropic features, including a pronounced Fano dip in the visible spectrum. Technically, employing numerical methods and tuning the geometrical sizes of the structure, we tuned and induced the Fano dip in the visible range, while the dark and bright plasmon resonance extremes are blueshifted to shorter wavelengths dramatically. Considering the calculated transmission window, we quantified the effective refractive index for the structure, while the substance of the substrate material was varied. Using Si, GaP, and InP semiconductors as substrate materials, we calculated and compared the corresponding figure of merit (FOM) for different regimes. The highest possible FOM was obtained for the GaP-Au-GaP negative-refractive-index metamaterial composed of ring/disk nanocavity heptamers as 62.4 at λ∼690  nm (arounnd the position of the Fano dip). Despite the outstanding symmetric nature of the suggested heptamer array, we provided sharp Fano dips by the appropriate tuning of the geometrical and chemical parameters. This study yields a method to employ ring/disk nanocavity heptamers as a negative-refractive-index metamaterial in designing highly accurate localization of surface plasmon resonance sensing devices and

  6. Negative refraction and focusing analysis in a left-handed material slab and realization with a 3D photonic crystal structure

    NASA Astrophysics Data System (ADS)

    Ahmadlou, Majid; Kamarei, Mahmoud; Sheikhi, Mohammad Hossein

    2006-02-01

    The increasing interest in metamaterials and structures with negative refraction index requires a formulation capable of a full analysis of wave propagation in such materials and structures. Since two-dimensional (2D) problems have been largely explored in the literature, the natural step is a three-dimensional (3D) formulation of these structures. In this paper, (3D) formulation and simulation of a left-handed metamaterial slab using the finite-difference time domain (FDTD) method in conjunction with perfectly matched layers (PMLs) is presented, and also a (3D) photonic crystal (PC) based structure is presented as a candidate for replacing the left-handed medium slab to realize the negative index of refraction on natural dielectric substrates. The results of these simulations are compared with each other, and the resulting outputs of the developed model are in good agreement. The results demonstrate numerically the focusing of the field emitted from an omnidirectional line source placed in front of the slab and crystal. Both the source and the focus pattern are away from the slab interfaces at two sides of the slab to have a real, negative perfect image. The dimensions of the simulation domain are set to have both source and image in the resulted plots. The focus pattern shows the ability of a photonic crystal structure in making a true flat lens.

  7. Perfect imaging with positive refraction

    NASA Astrophysics Data System (ADS)

    Leonhardt, Ulf; Tyc, Tomáš; Danner, Aaron

    2010-10-01

    We present several refractive index profiles for perfect imaging with positive refraction other than Maxwell's fish eye. Numerical simulations show that these profiles may transfer images with, in principle, unlimited resolution. Such profiles could overcome the fundamental limitations of perfect imaging with negative refraction and find practical applications in nanolithography.

  8. All-angle self-collimation in two-dimensional rhombic-lattice photonic crystals

    NASA Astrophysics Data System (ADS)

    Wu, Z. H.; Xie, K.; Yang, H. J.; Jiang, P.; He, X. J.

    2012-01-01

    In this work, the self-collimating phenomenon in two-dimensional rhombic-lattice photonic crystals is discussed in detail. The equi-frequency contours of a rhombic-lattice rod-type photonic crystal structure are calculated with the plane wave expansion method for different lattice angles and rod radii. A broad range of flat and open equi-frequency contours is found. A rhombic-lattice photonic crystal made of 301 × 21 silicon rods (n = 3.5) in air is presented as an illustration to demonstrate the broadband all-angle self-collimation. The bandwidth for all-angle self-collimation is verified to be 17.42% of the central frequency by simulations based on the finite-difference time-domain method. The all-angle self-collimation is found to be polarization-independent and the frequency for simultaneous TM and TE all-angle self-collimation is identified and verified by finite-difference time-domain simulations.

  9. Refractive Errors

    MedlinePlus

    ... and lens of your eye helps you focus. Refractive errors are vision problems that happen when the shape ... cornea, or aging of the lens. Four common refractive errors are Myopia, or nearsightedness - clear vision close up ...

  10. Refractive keratoplasty

    SciTech Connect

    Schwab, I.R. )

    1987-01-01

    This book contains 12 chapters. Some of the titles are: Perspectives on refractive surgery; Radial keratotomy; The refractive aspects of corneal transplantation; Wedge resection and relating incisions; Laser surgery of the cornea; and All plastic corneal lenses.

  11. Least-squares adjustment of triangles and quadrilaterals in which all angles and distances are observed.

    USGS Publications Warehouse

    Smith, W.K.; Varnes, D.J.

    1987-01-01

    The solutions for combined triangulation-trilateration least-squares adjustment of triangles and quadrilaterals, in which all angles and distances are observed, are developed. The triangle is adjusted by the method of observations only, and the quadrilateral is adjusted by the method of indirect observations. The problem of choosing the proper weight factor relating the angle measurements to the distance measurements is addressed. By changing the weight factor, the adjustment can vary from pure triangulation to pure trilateration.-from Authors

  12. Atmospheric microwave refractivity and refraction

    NASA Technical Reports Server (NTRS)

    Yu, E.; Hodge, D. B.

    1980-01-01

    The atmospheric refractivity can be expressed as a function of temperature, pressure, water vapor content, and operating frequency. Based on twenty-year meteorological data, statistics of the atmospheric refractivity were obtained. These statistics were used to estimate the variation of dispersion, attenuation, and refraction effects on microwave and millimeter wave signals propagating along atmospheric paths. Bending angle, elevation angle error, and range error were also developed for an exponentially tapered, spherical atmosphere.

  13. Evidence for subwavelength imaging with positive refraction

    NASA Astrophysics Data System (ADS)

    Gui Ma, Yun; Sahebdivan, Sahar; Ong, C. K.; Tyc, Tomáš; Leonhardt, Ulf

    2011-03-01

    The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction.

  14. The cylindrical air holes of the negative-refraction photonic crystal double flat lens group for lightwave target detection and imaging

    NASA Astrophysics Data System (ADS)

    Lu, Jian; Shen, Yang; Shen, TingGen; Lian, YingFei; Wang, FeiFei; Xu, Yang

    2013-06-01

    The influence of the cylindrical air holes of the negative-refraction photonic crystal (NR-PC) double flat lens group on the performance of lightwave target detection and imaging is studied in this paper using the finite-difference time-domain (FDTD) method. Numerical simulations indicate that significant enhancement of the scattering signal can be obtained by using a NR-PC flat lens; consequently, great improvement of the refocusing gain as well as the imaging resolution will be provided. We further research the effects of different positions for target detection by using a NR-PC double flat lens group with cylindrical air holes. Then we use defective air holes instead of perfect ones. By using a dynamic scanning scheme, we find that the distance between two flats could be changed flexibly. And it could improve the lateral resolution of target scanning and enlarge the distance between the target and flat greatly. In conclusion, our investigation optimized the performance of the detection and imaging system, and provided the basis for converting an idealized left-handed material lens into a physically realizable NR-PC double flat lens group.

  15. All-angle self-collimation in two-dimensional square array photonic crystals based on index contrast tailoring

    NASA Astrophysics Data System (ADS)

    Noori, Mina; Soroosh, Mohammad; Baghban, Hamed

    2015-03-01

    A comprehensive study has been performed to achieve all-angle self-collimation in basic two-dimensional square array photonic crystals with cylindrical scatterers. Based on plane wave expansion and finite difference time domain analysis for both rod- and hole-type structures, we report on all-angle self-collimation (SC) in the first band of the structure, which results in loss suppression due to out-of-plane scatterings. A lower threshold for index contrast has been obtained to achieve all-angle SC, which offers more design flexibility regarding structural parameters. Furthermore, it has been shown that a minimum and maximum coupling efficiency enhancement of ˜40% and 80% can be achieved for the proposed structure, respectively, by introducing a row of scatterers with proper radius at the input and the output air/photonic crystal interfaces.

  16. Emmetropisation and the aetiology of refractive errors

    PubMed Central

    Flitcroft, D I

    2014-01-01

    The distribution of human refractive errors displays features that are not commonly seen in other biological variables. Compared with the more typical Gaussian distribution, adult refraction within a population typically has a negative skew and increased kurtosis (ie is leptokurtotic). This distribution arises from two apparently conflicting tendencies, first, the existence of a mechanism to control eye growth during infancy so as to bring refraction towards emmetropia/low hyperopia (ie emmetropisation) and second, the tendency of many human populations to develop myopia during later childhood and into adulthood. The distribution of refraction therefore changes significantly with age. Analysis of the processes involved in shaping refractive development allows for the creation of a life course model of refractive development. Monte Carlo simulations based on such a model can recreate the variation of refractive distributions seen from birth to adulthood and the impact of increasing myopia prevalence on refractive error distributions in Asia. PMID:24406411

  17. Refraction characteristics of phononic crystals

    NASA Astrophysics Data System (ADS)

    Nemat-Nasser, Sia

    2015-08-01

    Some of the most interesting refraction properties of phononic crystals are revealed by examining the anti-plane shear waves in doubly periodic elastic composites with unit cells containing rectangular and/or elliptical multi-inclusions. The corresponding band structure, group velocity, and energy-flux vector are calculated using a powerful mixed variational method that accurately and efficiently yields all the field quantities over multiple frequency pass-bands. The background matrix and the inclusions can be anisotropic, each having distinct elastic moduli and mass densities. Equifrequency contours and energy-flux vectors are readily calculated as functions of the wave-vector components. By superimposing the energy-flux vectors on equifrequency contours in the plane of the wave-vector components, and supplementing this with a three-dimensional graph of the corresponding frequency surface, a wealth of information is extracted essentially at a glance. This way it is shown that a composite with even a simple square unit cell containing a central circular inclusion can display negative or positive energy and phase velocity refractions, or simply performs a harmonic vibration (standing wave), depending on the frequency and the wave-vector. Moreover, that the same composite when interfaced with a suitable homogeneous solid can display: (1) negative refraction with negative phase velocity refraction; (2) negative refraction with positive phase velocity refraction; (3) positive refraction with negative phase velocity refraction; (4) positive refraction with positive phase velocity refraction; or even (5) complete reflection with no energy transmission, depending on the frequency, and direction and the wavelength of the plane-wave that is incident from the homogeneous solid to the interface. For elliptical and rectangular inclusion geometries, analytical expressions are given for the key calculation quantities. Expressions for displacement, velocity, linear momentum

  18. Nonlinear refraction in aqueous colloidal gold

    NASA Astrophysics Data System (ADS)

    Mehendale, S. C.; Mishra, S. R.; Bindra, K. S.; Laghate, M.; Dhami, T. S.; Rustagi, K. C.

    1997-02-01

    Nonlinear refraction in aqueous colloidal gold at 527 nm was studied using the z-scan technique. While a z-scan with a 35 ns laser showed a large negative lensing, a z-scan with a 4 ps laser showed no measurable refraction. The observed nonlinear refraction is shown to be of thermal origin resulting from energy transfer from gold particles to the water molecules.

  19. Perfect imaging without refraction?

    NASA Astrophysics Data System (ADS)

    Blaikie, R. J.

    2011-12-01

    Recent work suggesting that ‘perfect’ far-field imaging is possible using Maxwell's fish-eye lens (Leonhardt 2009 New J. Phys. 11 093040) has raised a number of questions and controversies about the nature of imaging and field localization in inhomogeneous media. In this brief paper we present analogous results for a purely reflector-based imaging system—an elliptical cavity. With a source at one focus of the ellipse we show that sub-wavelength field localization can be achieved at the other focus when an active ‘drain’ is present there, but not without it. Does this show that far-field ‘perfect’ imaging is possible even without refraction (negative or positive)? Unfortunately not, giving further evidence that these are solely drain-induced effects.

  20. Refraction near the horizon

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.; Liller, William

    1990-01-01

    Variations in astronomical refraction near the horizon are examined. Sunset timings, a sextant mounted on a tripod, and a temperature profile are utilized to derive the variations in refraction data, collected from 7 locations. It is determined that the refraction ranges from 0.234 to 1.678 deg with an rms deviation of 0.16, and it is observed that the variation is larger than previously supposed. Some applications for the variation of refraction value are discussed.

  1. Refractive error blindness.

    PubMed Central

    Dandona, R.; Dandona, L.

    2001-01-01

    Recent data suggest that a large number of people are blind in different parts of the world due to high refractive error because they are not using appropriate refractive correction. Refractive error as a cause of blindness has been recognized only recently with the increasing use of presenting visual acuity for defining blindness. In addition to blindness due to naturally occurring high refractive error, inadequate refractive correction of aphakia after cataract surgery is also a significant cause of blindness in developing countries. Blindness due to refractive error in any population suggests that eye care services in general in that population are inadequate since treatment of refractive error is perhaps the simplest and most effective form of eye care. Strategies such as vision screening programmes need to be implemented on a large scale to detect individuals suffering from refractive error blindness. Sufficient numbers of personnel to perform reasonable quality refraction need to be trained in developing countries. Also adequate infrastructure has to be developed in underserved areas of the world to facilitate the logistics of providing affordable reasonable-quality spectacles to individuals suffering from refractive error blindness. Long-term success in reducing refractive error blindness worldwide will require attention to these issues within the context of comprehensive approaches to reduce all causes of avoidable blindness. PMID:11285669

  2. Design of Amphoteric Refraction Models Using WAVICA and RAYICA

    NASA Technical Reports Server (NTRS)

    Su, Richard

    2004-01-01

    The phenomenon of refraction of light is due to refractive index mismatches in two different media. However, to achieve this effect, a finite reflection loss is inevitable. A recent finding presented a unique type of interface, ferroelastic materials, that enables refraction without any reflection for either an electron or a light beam. This property is called total refraction. The same type of interface that yields total refraction can also yield amphoteric refraction, where the index of refraction can be either positive or negative depending on the incident angle. This interface could potentially be used to steer light without reflections which could have major applications in high power optics. My goal this summer is to first familiarize myself with the Mathematica software, especially the Wavica and Rayica packages. I will then model the amphoteric refraction by either modifying the Wavica and Rayica packages or using the built-in functions in these packages.

  3. An 'electromagnetic wiggler' originating from refraction of waves at the side edge of a Bragg reflector

    NASA Astrophysics Data System (ADS)

    Iorsh, I. V.; Kaliteevski, M. A.; Brand, S.; Abram, R. A.; Kaliteevskaya, N. A.

    2011-05-01

    Calculations are reported which predict that light incident on the side edge of a Bragg reflector can show varied and unusual refraction behaviour, including a rapid transition from positive to negative refraction. Although under certain conditions negative refraction can occur, it is concluded that perfect lensing based on it is unlikely to be realised in practice. However, it is shown that light incident obliquely on the structure can be made to propagate normal to the interface after refraction while exhibiting lateral oscillations of its Poynting vector, an effect that could possibly find application in an 'electromagnetic wiggler'. It is also shown that negative group velocity rather than negative effective mass is required for the observation of the negative refraction, and in the case of low refractive index contrast, negative refraction occurs only when the size of the illumination spot exceeds a critical value, which is inversely proportional to the contrast of the refractive indices.

  4. Atmospheric refraction: a history.

    PubMed

    Lehn, Waldemar H; van der Werf, Siebren

    2005-09-20

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of uniform density up to a sharp upper transition to the ether, at which the refraction occurred. Alhazen and Witelo transmitted his knowledge to medieval Europe. The first accurate measurements were made by Tycho Brahe in the 16th century. Finally, Kepler, who was aware of unusually strong refractions, used the Ptolemaic model to explain the first documented and recognized mirage (the Novaya Zemlya effect).

  5. Atmospheric refraction: a history

    NASA Astrophysics Data System (ADS)

    Lehn, Waldemar H.; van der Werf, Siebren

    2005-09-01

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of uniform density up to a sharp upper transition to the ether, at which the refraction occurred. Alhazen and Witelo transmitted his knowledge to medieval Europe. The first accurate measurements were made by Tycho Brahe in the 16th century. Finally, Kepler, who was aware of unusually strong refractions, used the Ptolemaic model to explain the first documented and recognized mirage (the Novaya Zemlya effect).

  6. 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)

  7. Uncorrected refractive errors.

    PubMed

    Naidoo, Kovin S; Jaggernath, Jyoti

    2012-01-01

    Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship. PMID:22944755

  8. Anomalous refraction, diffraction, and imaging in metamaterials

    NASA Astrophysics Data System (ADS)

    Paul, Thomas; Rockstuhl, Carsten; Menzel, Christoph; Lederer, Falk

    2009-03-01

    In the past several years, optical metamaterials (MMs) have attracted a considerable deal of interest because it may be anticipated that their properties can be shaped to an unprecedented extent relieving optics from some of its natural limitations. An inevitable first step toward this goal is the evaluation of the optical properties of specifically designed MMs. To date, apart from identifying chiral properties of very specific configurations, this is primarily done in retrieving an effective refractive index—mostly—only for normal incidence. On this basis suggestions for a perfect lens, exploiting this negative refractive index have been put forward by taking advantage of geometrical optics arguments. We show that this approach is pointless for realistic MMs. Instead we prove that the dispersion relation of normal modes in these MMs provides all the required information. Most of the relevant optical parameters, such as refraction and diffraction coefficients, can be derived from this relation. Imaging properties follow straightforwardly from that data. This general approach holds for any optical material, in particular, for all MMs in question. As an example, we apply it to the fishnet structure: one of the most prominent and best studied design approaches to date. We show that both refraction and diffraction properties are strongly spatially and temporally dispersive and they can even change sign. In detail, we study the effect of these peculiarities on imaging and refraction of finite beams. In particular, we discuss both the effect of the specific dispersion relation and the losses on the imaging properties. All our physical predictions are backed by rigorous numerical calculations and the agreement is almost perfect. Ultimately the main conclusion to be drawn is that a negative index of refraction is by no means a sufficient criterion to achieve negative refraction and/or perfect imaging.

  9. Refractive surgery for keratoconus.

    PubMed

    Ormonde, Sue

    2013-03-01

    Traditionally, keratoconus has been managed with glasses when mild, contact lenses when moderate and keratoplasty when severe. When cornea-based refractive surgery was first developed it appeared to be a useful option for keratoconus until reports of post-operative progressive ectasia emerged and thus keratoconus was considered a contraindication to refractive surgery. However, improvements in older techniques and the development of new techniques mean that there are now several viable options to avoid keratoplasty in contact lens-intolerant patients. This review discusses the risks and benefits of excimer laser refractive procedures, both with and without corneal collagen cross linking, as well as intra-corneal ring segments, phakic intraocular lenses and refractive lens exchange with toric intraocular lens implantation. PMID:23496655

  10. Atmospheric refraction: a history.

    PubMed

    Lehn, Waldemar H; van der Werf, Siebren

    2005-09-20

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of uniform density up to a sharp upper transition to the ether, at which the refraction occurred. Alhazen and Witelo transmitted his knowledge to medieval Europe. The first accurate measurements were made by Tycho Brahe in the 16th century. Finally, Kepler, who was aware of unusually strong refractions, used the Ptolemaic model to explain the first documented and recognized mirage (the Novaya Zemlya effect). PMID:16201423

  11. Nonlinear Refractive Properties

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.

    2001-01-01

    Using nonlinear refractive properties of a salt-water solution at two wavelengths, numerical analysis has been performed to extract temperature and concentration from interferometric fringe data. The theoretical study, using a commercially available equation solving software, starts with critical fringe counting needs and the role of nonlinear refractive properties in such measurements. Finally, methodology of the analysis, codes, fringe counting accuracy needs, etc. is described in detail.

  12. Refraction corrections for surveying

    NASA Technical Reports Server (NTRS)

    Lear, W. M.

    1979-01-01

    Optical measurements of range and elevation angle are distorted by the earth's atmosphere. High precision refraction correction equations are presented which are ideally suited for surveying because their inputs are optically measured range and optically measured elevation angle. The outputs are true straight line range and true geometric elevation angle. The 'short distances' used in surveying allow the calculations of true range and true elevation angle to be quickly made using a programmable pocket calculator. Topics covered include the spherical form of Snell's Law; ray path equations; and integrating the equations. Short-, medium-, and long-range refraction corrections are presented in tables.

  13. Refraction corrections for surveying

    NASA Technical Reports Server (NTRS)

    Lear, W. M.

    1980-01-01

    Optical measurements of range and elevation angles are distorted by refraction of Earth's atmosphere. Theoretical discussion of effect, along with equations for determining exact range and elevation corrections, is presented in report. Potentially useful in optical site surveying and related applications, analysis is easily programmed on pocket calculator. Input to equation is measured range and measured elevation; output is true range and true elevation.

  14. Conceptualization of Light Refraction

    ERIC Educational Resources Information Center

    Sokolowski, Andrzej

    2013-01-01

    There have been a number of papers dealing quantitatively with light refraction. Yet the conceptualization of the phenomenon that sets the foundation for a more rigorous math analysis is minimized. The purpose of this paper is to fill that gap. (Contains 3 figures.)

  15. Cloaking and imaging effects in plasmonic checkerboards of negative ɛ and μ and dielectric photonic crystal checkerboards

    NASA Astrophysics Data System (ADS)

    Guenneau, S.; Ramakrishna, S. Anantha; Enoch, S.; Chakrabarti, Sangeeta; Tayeb, G.; Gralak, B.

    2007-10-01

    Negative refractive index materials are known to be able to support a host of surface plasmon states for both polarizations of light. This makes possible unique effects such as a perfect lens. Checkerboards consisting of alternating cells of positive and negative refractive index represent a very singular situation in which the density of modes diverges at the corners. This raises the question as to whether such effects will still be observed in a real dissipative system of finite size. We have considered several aspects of such structures including these and symmetry aspects (rectangular against triangular checkerboards). We have also studied silver checkerboards whose transverse extent is finite. Negative refractive index checkerboards bring new electromagnetic paradigms both through the intriguing possibilities they appear to offer, and the challenges they present to our understanding of the diffraction process. Most intriguing of all is the possibility of a triangular checkerboard lens whose resolution is limited not by wavelength, but only by the losses in the constituent materials, while a ray picture suggests it behaves as a perfect mirror. The resolution of this lens increases without limit as the losses tend to zero as shown by the generalized lens theorem. We finally show that light confinement can be achieved to certain extent using dielectric triangular photonic crystal (PC) checkerboards displaying the all-angle-negative-refraction (AANR) within the Bragg regime in p polarization. Effectively even a single rectangular or triangular PC can act as an open resonator that confines light in its neighborhood. This cloaking effect has been previously observed in PC slabs displaying the AANR effect. We show that the cloaking is enhanced for three triangular PC wedges sharing a vertex and further improved for 12 triangular PC wedges arranged in a checkerboard fashion.

  16. 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.

  17. Comparison Between Radar and Automatic Weather Station Refractivity Variability

    NASA Astrophysics Data System (ADS)

    Hallali, Ruben; Dalaudier, Francis; Parent du Chatelet, Jacques

    2016-08-01

    Weather radars measure changes in the refractive index of air in the atmospheric boundary layer. The technique uses the phase of signals from ground targets located around the radar to provide information on atmospheric refractivity related to meteorological quantities such as temperature, pressure and humidity. The approach has been successfully implemented during several field campaigns using operational S-band radars in Canada, UK, USA and France. In order to better characterize the origins of errors, a recent study has simulated temporal variations of refractivity based on Automatic Weather Station (AWS) measurements. This reveals a stronger variability of the refractivity during the summer and in the afternoon when the refractivity is the most sensitive to humidity, probably because of turbulence close to the ground. This raises the possibility of retrieving information on the turbulent state of the atmosphere from the variability in radar refractivity. An analysis based on a 1-year dataset from the operational C-band radar at Trappes (near Paris, France) and AWS refractivity variability measurements was used to measure those temporal and spatial variabilities. Particularly during summer, a negative bias increasing with range is observed between radar and AWS estimations, and is well explained by a model based on Taylor's hypotheses. The results demonstrate the possibility of establishing, depending on season, a quantitative and qualitative link between radar and AWS refractivity variability that reflects low-level coherent turbulent structures.

  18. Black and gray Helmholtz-Kerr soliton refraction

    SciTech Connect

    Sanchez-Curto, Julio; Chamorro-Posada, Pedro; McDonald, Graham S.

    2011-01-15

    Refraction of black and gray solitons at boundaries separating different defocusing Kerr media is analyzed within a Helmholtz framework. A universal nonlinear Snell's law is derived that describes gray soliton refraction, in addition to capturing the behavior of bright and black Kerr solitons at interfaces. Key regimes, defined by beam and interface characteristics, are identified, and predictions are verified by full numerical simulations. The existence of a unique total nonrefraction angle for gray solitons is reported; both internal and external refraction at a single interface is shown possible (dependent only on incidence angle). This, in turn, leads to the proposal of positive or negative lensing operations on soliton arrays at planar boundaries.

  19. 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).

  20. Steering and collimating ballistic electrons with amphoteric refraction

    SciTech Connect

    Radu, A.; Dragoman, D.; Iftimie, S.

    2012-07-15

    We show that amphoteric refraction of ballistic electrons, i.e., positive or negative refraction depending on the incidence angle, occurs at an interface between an isotropic and an anisotropic medium and can be employed to steer and collimate electron beams. The steering angle is determined by the materials' parameters, but the degree of collimation can be tuned in a significant range by changing the energy of ballistic electrons.

  1. Refractive Error, Axial Length, and Relative Peripheral Refractive Error before and after the Onset of Myopia

    PubMed Central

    Mutti, Donald O.; Hayes, John R.; Mitchell, G. Lynn; Jones, Lisa A.; Moeschberger, Melvin L.; Cotter, Susan A.; Kleinstein, Robert N.; Manny, Ruth E.; Twelker, J. Daniel; Zadnik, Karla

    2009-01-01

    year after onset, whereas axial length and myopic refractive error continued to elongate and to progress, respectively, although at slower rates compared with the rate at onset. Conclusions A more negative refractive error, longer axial length, and more hyperopic relative peripheral refractive error in addition to faster rates of change in these variables may be useful for predicting the onset of myopia, but only within a span of 2 to 4 years before onset. Becoming myopic does not appear to be characterized by a consistent rate of increase in refractive error and expansion of the globe. Acceleration in myopia progression, axial elongation, and peripheral hyperopia in the year prior to onset followed by relatively slower, more stable rates of change after onset suggests that more than one factor may influence ocular expansion during myopia onset and progression. PMID:17525178

  2. Colored Flag by Double Refraction.

    ERIC Educational Resources Information Center

    Reid, Bill

    1994-01-01

    Describes various demonstrations that illustrate double refraction and rotation of the plane of polarization in stressed, transparent plastics, with the consequent production of colored designs. (ZWH)

  3. GRAVSAT/GEOPAUSE refraction study

    NASA Technical Reports Server (NTRS)

    Llewellyn, S. K.

    1977-01-01

    A ground station network tracked a high altitude spacecraft which in turn tracked a low orbiting satellite. Orbit data are relayed back to the ground stations. A refraction study was performed on this configuration to compute ionospheric and tropospheric refraction effects along the satellite and ground links.

  4. Effect of refractive error on temperament and character properties

    PubMed Central

    Kalkan Akcay, Emine; Canan, Fatih; Simavli, Huseyin; Dal, Derya; Yalniz, Hacer; Ugurlu, Nagihan; Gecici, Omer; Cagil, Nurullah

    2015-01-01

    AIM To determine the effect of refractive error on temperament and character properties using Cloninger's psychobiological model of personality. METHODS Using the Temperament and Character Inventory (TCI), the temperament and character profiles of 41 participants with refractive errors (17 with myopia, 12 with hyperopia, and 12 with myopic astigmatism) were compared to those of 30 healthy control participants. Here, temperament comprised the traits of novelty seeking, harm-avoidance, and reward dependence, while character comprised traits of self-directedness, cooperativeness, and self-transcendence. RESULTS Participants with refractive error showed significantly lower scores on purposefulness, cooperativeness, empathy, helpfulness, and compassion (P<0.05, P<0.01, P<0.05, P<0.05, and P<0.01, respectively). CONCLUSION Refractive error might have a negative influence on some character traits, and different types of refractive error might have different temperament and character properties. These personality traits may be implicated in the onset and/or perpetuation of refractive errors and may be a productive focus for psychotherapy. PMID:25709911

  5. Nonlinear refraction in vitreous humor.

    PubMed

    Rockwell, B A; Roach, W P; Rogers, M E; Mayo, M W; Toth, C A; Cain, C P; Noojin, G D

    1993-11-01

    We extend the application of the z-scan technique to determine the nonlinear refractive index (n(2)) for human and rabbit vitreous humor, water, and physiological saline. In these measurements there were nonlinear contributions to the measured signal from the aqueous samples and the quartz cell that held the sample. Measurements were made with 60-ps pulses at 532 nm. To our knowledge, this is the first measurement of the nonlinear refractive properties of biological material. PMID:19829406

  6. 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.

  7. Characterizing conical refraction optical tweezers.

    PubMed

    McDonald, C; McDougall, C; Rafailov, E; McGloin, D

    2014-12-01

    Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focusing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots, and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focusing on the trap stiffness, and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot, but benefit from rotational control. PMID:25490654

  8. Refraction of coastal ocean waves

    NASA Technical Reports Server (NTRS)

    Shuchman, R. A.; Kasischke, E. S.

    1981-01-01

    Refraction of gravity waves in the coastal area off Cape Hatteras, NC as documented by synthetic aperture radar (SAR) imagery from Seasat orbit 974 (collected on September 3, 1978) is discussed. An analysis of optical Fourier transforms (OFTs) from more than 70 geographical positions yields estimates of wavelength and wave direction for each position. In addition, independent estimates of the same two quantities are calculated using two simple theoretical wave-refraction models. The OFT results are then compared with the theoretical results. A statistical analysis shows a significant degree of linear correlation between the data sets. This is considered to indicate that the Seasat SAR produces imagery whose clarity is sufficient to show the refraction of gravity waves in shallow water.

  9. 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.

  10. The Optics of Refractive Substructure

    NASA Astrophysics Data System (ADS)

    Johnson, Michael D.; Narayan, Ramesh

    2016-08-01

    Newly recognized effects of refractive scattering in the ionized interstellar medium have broad implications for very long baseline interferometry (VLBI) at extreme angular resolutions. Building upon work by Blandford & Narayan, we present a simplified, geometrical optics framework, which enables rapid, semi-analytic estimates of refractive scattering effects. We show that these estimates exactly reproduce previous results based on a more rigorous statistical formulation. We then derive new expressions for the scattering-induced fluctuations of VLBI observables such as closure phase, and we demonstrate how to calculate the fluctuations for arbitrary quantities of interest using a Monte Carlo technique.

  11. Comment on ``Negative Refraction Makes a Perfect Lens''

    NASA Astrophysics Data System (ADS)

    't Hooft, G. W.

    2001-12-01

    A Comment on the Letter by J. B. Pendry, Phys. Rev. Lett. 85, 3966 (2000). The authors of the Letter offer a Reply. Issues similar to those made in the following two Comments were also raised in a paper by N. Garcia and M. Nieto-Vesperinas, Madrid, Spain.

  12. REFLECTION AND REFRACTION, VOLUME 2.

    ERIC Educational Resources Information Center

    KLAUS, DAVID J.; AND OTHERS

    THIS VOLUME 2 OF A TWO-VOLUME SET PROVIDES AUTOINSTRUCTION IN PHYSICS. THE UNITS COVERED IN THIS VOLUME ARE (1) REFLECTION OF LIGHT, (2) PHOTOMETRY, (3) POLARIZATION, (4) REFRACTION OF LIGHT, (5) SNELL'S LAW, (6) LENSES, FOCUS, AND FOCAL POINTS, (7) IMAGE FORMATION, AND (8) ABERRATIONS, THE EYE, AND MAGNIFICATION. THE INTRODUCTION AND UNITS ON…

  13. 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…

  14. 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.

  15. 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.

  16. Refractive Errors - Multiple Languages: MedlinePlus

    MedlinePlus

    ... Are Here: Home → Multiple Languages → All Health Topics → Refractive Errors URL of this page: https://medlineplus.gov/languages/ ... V W XYZ List of All Topics All Refractive Errors - Multiple Languages To use the sharing features on ...

  17. 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.

  18. Kramers-Kronig relation between nonlinear absorption and refraction of C(60) and C(70).

    PubMed

    Wu, Chen-Cheng; Liu, Tai-Min; Wei, Tai-Ying; Xin, Li; Li, Yi-Ci; Lee, Li-Shu; Chang, Che-Kai; Tang, Jaw-Luen; Yang, Sidney S; Wei, Tai-Huei

    2010-10-25

    Using the Z-scan technique with 532 nm 16 picosecond laser pulses, we observe reverse saturable absorption and positive nonlinear refraction of toluene solutions of both C(60) and C(70). By deducting the positive Kerr nonlinear refraction of the solvent, we notice that the solute molecules contribute to nonlinear refraction of opposite signs: positive for C(60) and negative for C(70). Attributing nonlinear absorption and refraction of both solutes to cascading one-photon excitations, we illustrate that they satisfy the Kramers-Kronig relation. Accordingly, we attest the signs and magnitudes of nonlinear refraction for both solutes at 532 nm by Kramers-Kronig transform of the corresponding nonlinear absorption spectra.

  19. Refractive evaluation in thalidomide embryopathy.

    PubMed

    Strömland, K; Miller, M T

    1992-01-01

    To evaluate the ocular findings associated with thalidomide embryopathy, we examined 86 of 100 Swedes who had a proven correlation between birth defects and the mother's intake of thalidomide during pregnancy. Cycloplegic refraction, keratometry, and axial length measurements were performed. The subjects were divided into four groups according to their physical malformations, giving a time frame for when in gestation the insult occurred (the sensitive phase for thalidomide is 20-36 days after conception). The results indicate a trend toward shorter and longer axial lengths, high refractive errors, and corneal astigmatism in thalidomide embryopathy compared to controls, and in addition there was a tendency for those anomalies to occur in the group with the earliest thalidomide-induced defects. It is suggested that thalidomide disturbs the growth and shape of the eye and that this effect is exerted early in its teratogenic period.

  20. Electro-refractive photonic device

    SciTech Connect

    Zortman, William A.; Watts, Michael R.

    2015-06-09

    The various technologies presented herein relate to phase shifting light to facilitate any of light switching, modulation, amplification, etc. Structures are presented where a second layer is juxtaposed between a first layer and a third layer with respective doping facilitating formation of p-n junctions at the interface between the first layer and the second layer, and between the second layer and the third layer. Application of a bias causes a carrier concentration change to occur at the p-n junctions which causes a shift in the effective refractive index per incremental change in an applied bias voltage. The effective refractive index enhancement can occur in both reverse bias and forward bias. The structure can be incorporated into a waveguide, an optical resonator, a vertical junction device, a horizontal junction device, a Mach-Zehnder interferometer, a tuneable optical filter, etc.

  1. Comment on ``Perfect imaging with positive refraction in three dimensions''

    NASA Astrophysics Data System (ADS)

    Merlin, R.

    2010-11-01

    Leonhardt and Philbin [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.81.011804 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit.

  2. Comment on ''Perfect imaging with positive refraction in three dimensions''

    SciTech Connect

    Merlin, R.

    2010-11-15

    Leonhardt and Philbin [Phys. Rev. A 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit.

  3. Laser refractive tomography of phase objects

    SciTech Connect

    Raskovskaya, I L

    2013-06-30

    The principles are outlined of laser refractive tomography - a method for reconstructing the values of the refractive index in the cross sections of phase objects, which involves the use of three-dimensional refractive images (3D refractograms) of structured laser radiation. A simulation algorithm is realised and examples are provided of characteristic 3D refractograms obtained by solving the direct problem of refraction of structured radiation. A method was developed for reconstructing the values of refractive index under conditions of strong refraction, which is based on the visualisation of ray trajectories inside an optically inhomogeneous medium. A classification is made of possible approaches to the solution of the inverse problem of refraction based on the visualisation of ray trajectories. Examples are given of cross section reconstruction and quantitative diagnostics of phase objects. (laser imaging)

  4. Anomalous refraction of light through slanted-nanoaperture arrays on metal surface

    SciTech Connect

    Kim, Myungji; Jung, Yun Suk; Xi, Yonggang; Kim, Hong Koo

    2015-09-07

    We report a nanoapertured metal surface that demonstrates anomalous refraction of light for a wide range of incident angles. A nanoslit aperture is designed to serve as a tilted vertical-dipole whose radiation pattern orients to a glancing angle direction to substrate. An array of such slanted nanoslits formed in a metal film redirects an incident beam into the direction of negative refraction angle: the aperture-transmitted wave makes a far-field propagation to the tilt-oriented direction of radiation pattern. The thus-designed nanoaperture array demonstrates the −1st order diffraction (i.e., to the negative refraction-angle direction) with well-suppressed background transmission (the zero-order direct transmission and other higher-order diffractions). Engineering the radiation pattern of nanoaperture offers an approach to overcoming the limits of conventional diffractive/refractive optics and complementing metasurface-based nano-optics.

  5. Zero refraction in natural materials and the mechanism of metal superlens

    NASA Astrophysics Data System (ADS)

    Zhou, Yun-Song; Wang, Huai-Yu; Wang, Hai

    2012-06-01

    We found that a single negative material has the characteristic of zero refraction in near field, and point out that the mechanism of a metal superlens to image with a resolution exceeding the diffraction limitation is different from that of a perfect lens made of a double negative material. The principle of metal superlens is disclosed. Our numerical results based on the zero-refraction characteristic is well in agreement with the experimental results. This work brings new understanding about the single negative materials and will lead to the applications of the superlens in the right direction.

  6. Centration axis in refractive surgery.

    PubMed

    Arba Mosquera, Samuel; Verma, Shwetabh; McAlinden, Colm

    2015-01-01

    The human eye is an asymmetric optical system and the real cornea is not a rotationally symmetrical volume. Each optical element in the eye has its own optical and neural axes. Defining the optimum center for laser ablation is difficult with many available approaches. We explain the various centration approaches (based on these reference axes) in refractive surgery and review their clinical outcomes. The line-of-sight (LOS) (the line joining the entrance pupil center with the fixation point) is often the recommended reference axis for representing wavefront aberrations of the whole eye (derived from the definition of chief ray in geometrical optics); however pupil centration can be unstable and change with the pupil size. The corneal vertex (CV) represents a stable preferable morphologic reference which is the best approximate for alignment to the visual axis. However, the corneal light reflex can be considered as non-constant, but dependent on the direction of gaze of the eye with respect to the light source. A compromise between the pupil and CV centered ablations is seen in the form of an asymmetric offset where the manifest refraction is referenced to the CV while the higher order aberrations are referenced to the pupil center. There is a need for a flexible choice of centration in excimer laser systems to design customized and non-customized treatments optimally. PMID:26605360

  7. 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.

  8. 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.

  9. Statistical Analysis of Refractivity in UAE

    NASA Astrophysics Data System (ADS)

    Al-Ansari, Kifah; Al-Mal, Abdulhadi Abu; Kamel, Rami

    2007-07-01

    This paper presents the results of the refractivity statistics in the UAE (United Arab Emirates) for a period of 14 years (1990-2003). Six sites have been considered using meteorological surface data (Abu Dhabi, Dubai, Sharjah, Al-Ain, Ras Al-Kaimah, and Al-Fujairah). Upper air (radiosonde) data were available at one site only, Abu Dhabi airport, which has been considered for the refractivity gradient statistics. Monthly and yearly averages are obtained for the two parameters, refractivity and refractivity gradient. Cumulative distributions are also provided.

  10. Measuring Variable Refractive Indices Using Digital Photos

    ERIC Educational Resources Information Center

    Lombardi, S.; Monroy, G.; Testa, I.; Sassi, E.

    2010-01-01

    A new procedure for performing quantitative measurements in teaching optics is presented. Application of the procedure to accurately measure the rate of change of the variable refractive index of a water-denatured alcohol mixture is described. The procedure can also be usefully exploited for measuring the constant refractive index of distilled…

  11. Determination of the anisotropy complex refractive indices of chicken tissues in vitro at 650 nm

    NASA Astrophysics Data System (ADS)

    Sun, P.; Sun, H.

    2010-07-01

    The anisotropy complex refractive index of tissue is an important parameter in understanding the behavior of light, including its transportation in and interaction with tissues. We used the specular reflection method to investigate the anisotropy complex refractive index of chicken tissue with fibrous structures in vitro at a wavelength of 650 nm. The measurement data were highly consistent with the Fesnell equations. The results showed that the real refractive index was higher along the orientation of the fibers than along the cross section, but the imaginary refractive index was nearly identical. Furthermore, the fiber orientation was in the direction of the optic axis of the chicken tissue and the chicken tissue section was similar to a negative uniaxial crystal wafer.

  12. Retinal Image Simulation of Subjective Refraction Techniques.

    PubMed

    Perches, Sara; Collados, M Victoria; Ares, Jorge

    2016-01-01

    Refraction techniques make it possible to determine the most appropriate sphero-cylindrical lens prescription to achieve the best possible visual quality. Among these techniques, subjective refraction (i.e., patient's response-guided refraction) is the most commonly used approach. In this context, this paper's main goal is to present a simulation software that implements in a virtual manner various subjective-refraction techniques--including Jackson's Cross-Cylinder test (JCC)--relying all on the observation of computer-generated retinal images. This software has also been used to evaluate visual quality when the JCC test is performed in multifocal-contact-lens wearers. The results reveal this software's usefulness to simulate the retinal image quality that a particular visual compensation provides. Moreover, it can help to gain a deeper insight and to improve existing refraction techniques and it can be used for simulated training.

  13. Refraction in electrically thin inhomogeneous media.

    PubMed

    Ruphuy, Miguel; Ramahi, Omar M

    2016-04-01

    This work presents a new formulation for refraction from flat electrically thin lenses and reflectors comprised of inhomogeneous material. Inhomogeneous electrically thin flat lenses and reflectors cannot make use of the Snell law since this classical formulation works solely at interfaces of planar homogeneous media. The refraction of a perpendicularly incident plane wave at a planar interface is physically explained through the phase advance of the rays within the medium. The Huygens principle is then used to construct the refracted wavefront. The formulation is validated using numerical full wave simulation for several examples where the refractive angle is predicted with good accuracy. Furthermore, the formulation gives a physical insight of the phenomenon of refraction from electrically thin inhomogeneous media.

  14. Retinal Image Simulation of Subjective Refraction Techniques

    PubMed Central

    Perches, Sara; Collados, M. Victoria; Ares, Jorge

    2016-01-01

    Refraction techniques make it possible to determine the most appropriate sphero-cylindrical lens prescription to achieve the best possible visual quality. Among these techniques, subjective refraction (i.e., patient’s response-guided refraction) is the most commonly used approach. In this context, this paper’s main goal is to present a simulation software that implements in a virtual manner various subjective-refraction techniques—including Jackson’s Cross-Cylinder test (JCC)—relying all on the observation of computer-generated retinal images. This software has also been used to evaluate visual quality when the JCC test is performed in multifocal-contact-lens wearers. The results reveal this software’s usefulness to simulate the retinal image quality that a particular visual compensation provides. Moreover, it can help to gain a deeper insight and to improve existing refraction techniques and it can be used for simulated training. PMID:26938648

  15. Fully 3D refraction correction dosimetry system

    NASA Astrophysics Data System (ADS)

    Manjappa, Rakesh; Sharath Makki, S.; Kumar, Rajesh; Mohan Vasu, Ram; Kanhirodan, Rajan

    2016-02-01

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  16. Fully 3D refraction correction dosimetry system.

    PubMed

    Manjappa, Rakesh; Makki, S Sharath; Kumar, Rajesh; Vasu, Ram Mohan; Kanhirodan, Rajan

    2016-02-21

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  17. The BHVI-EyeMapper: Peripheral Refraction and Aberration Profiles

    PubMed Central

    Fedtke, Cathleen; Ehrmann, Klaus; Falk, Darrin; Bakaraju, Ravi C.; Holden, Brien A.

    2014-01-01

    ABSTRACT Purpose The aim of this article was to present the optical design of a new instrument (BHVI-EyeMapper, EM), which is dedicated to rapid peripheral wavefront measurements across the visual field for distance and near, and to compare the peripheral refraction and higher-order aberration profiles obtained in myopic eyes with and without accommodation. Methods Central and peripheral refractive errors (M, J180, and J45) and higher-order aberrations (C[3, 1], C[3, 3], and C[4, 0]) were measured in 26 myopic participants (mean [±SD] age, 20.9 [±2.0] years; mean [±SD] spherical equivalent, −3.00 [±0.90] diopters [D]) corrected for distance. Measurements were performed along the horizontal visual field with (−2.00 to −5.00 D) and without (+1.00 D fogging) accommodation. Changes as a function of accommodation were compared using tilt and curvature coefficients of peripheral refraction and aberration profiles. Results As accommodation increased, the relative peripheral refraction profiles of M and J180 became significantly (p < 0.05) more negative and the profile of M became significantly (p < 0.05) more asymmetric. No significant differences were found for the J45 profiles (p > 0.05). The peripheral aberration profiles of C[3, 1], C[3, 3], and C[4, 0] became significantly (p < 0.05) less asymmetric as accommodation increased, but no differences were found in the curvature. Conclusions The current study showed that significant changes in peripheral refraction and higher-order aberration profiles occurred during accommodation in myopic eyes. With its extended measurement capabilities, that is, permitting rapid peripheral refraction and higher-order aberration measurements up to visual field angles of ±50 degrees for distance and near (up to −5.00 D), the EM is a new advanced instrument that may provide additional insights in the ongoing quest to understand and monitor myopia development. PMID:25105690

  18. J. B. Biot and Refraction Calculations

    NASA Astrophysics Data System (ADS)

    Young, A. T.

    2000-12-01

    The Auer-Standish (AJ 119, 2472, 2000) algorithm, recommended in the revised Explanatory Supplement for calculating refraction in an arbitrary model atmosphere, was derived and used by J. B. Biot (Conn. des Tems pour l'An 1839) a century and a half earlier, using Newton's (wrong) emission theory, and the clumsy notation of Laplace's Mécanique Céleste, which Biot had proof-read. Newton, Laplace, and Biot all describe refraction in terms of the trajectories of ``luminous molecules'' attracted by a central force exerted by the atmosphere; this explains why Laplace considered refraction a topic in celestial mechanics. Fortunately for these authors, the only optics required is Snel's law of refraction, which was discovered before Newton's birth, and which Newton's corpuscular optics was rigged to reproduce. Thus Biot's ``derivation'' of the refractive invariant nr sin z by Laplace's method is a circular and unnecessary argument. While Auer & Standish were reinventing Biot's method, the historian D. T. Whiteside (Centaurus 24, 288, 1980) noticed the mathematical similarity of the refraction theories of Newton and Biot to modern ones, and rashly concluded that ``working astronomers still find computational advantage in maintaining the fiction of a Newtonian emission theory'' --- which is absurd nonsense! Despite being an emissionist, Biot understood atmospheric refraction much better than most astronomers do today: he knew why refraction is almost independent of atmospheric structure, except within a few degrees of the horizon, and that refraction at the horizon depends mostly on the local temperature gradient. His work --- together with that of Lord Rayleigh, who derived his eponymous scattering law from the elastic-solid theory of the luminiferous \\ae ther --- reminds us that a theory's correct results do not make it true. This work was supported by NSF grant ATM-9714357.

  19. 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.

  20. The refraction in the atmospheric surface layer

    NASA Astrophysics Data System (ADS)

    Golitsyn, G. S.

    1982-12-01

    An analytical theory of refraction for the atmospheric layer is developed in which the vertical profiles of the refraction are calculated based on the theory of Monin and Obukhov (1954). A similarity parameter is found for the refraction in such conditions. These results are used to clarify the idea of Moroz (1976) that the nearness of the horizon as recorded by the automatic stations on the surface of Venus can be explained by the decrease in the temperature at the very surface of the planet. In addition, several other optical phenomena which occur near the surface of the earth are examined.

  1. Atmospheric refraction errors in laser ranging systems

    NASA Technical Reports Server (NTRS)

    Gardner, C. S.; Rowlett, J. R.

    1976-01-01

    The effects of horizontal refractivity gradients on the accuracy of laser ranging systems were investigated by ray tracing through three dimensional refractivity profiles. The profiles were generated by performing a multiple regression on measurements from seven or eight radiosondes, using a refractivity model which provided for both linear and quadratic variations in the horizontal direction. The range correction due to horizontal gradients was found to be an approximately sinusoidal function of azimuth having a minimum near 0 deg azimuth and a maximum near 180 deg azimuth. The peak to peak variation was approximately 5 centimeters at 10 deg elevation and decreased to less than 1 millimeter at 80 deg elevation.

  2. Negative-permittivity plasma generation in negative-permeability space with high-energy metamaterials

    NASA Astrophysics Data System (ADS)

    Sakai, Osamu; Nakamura, Yoshihiro; Iwai, Akinori; Iio, Satoshi

    2016-10-01

    Plasma generation by electromagnetic waves in negative-permeability space is analyzed using experimental results and theoretical models. Installation of negative-permeability metamaterials triggers drastic changes to the propagation of electromagnetic waves. Unlike usual cases in which permeability is  +1, negative permeability induces evanescent modes in a space without plasma. However, if permittivity becomes negative due to high-electron-density or overdense plasma, electromagnetic waves can propagate because negative-refractive-index states emerge. In this study, reviewing our previous experimental data, we study the underlying physical processes in plasma generation in terms of wave propagation and parameters of wave media. We confirm nonlinear (transition) processes in the phase of density evolution up to the negative permittivity state and negative-refractive-index states in the quasi-steady phase. We also note that such energetic metamaterials are built up when we use plasma, unlike conventional metamaterials composed of solid-state materials.

  3. 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.

  4. A New Expression for Astronomical Refraction

    NASA Astrophysics Data System (ADS)

    Yan, Haojian

    1996-09-01

    In this paper, new sophisticated computing formulas for astronomical refraction have been developed based on the generator function method of atmospheric refractive integrals proposed by Yan & Ping (1995, AJ, 110, 934). The accuracies of the expressions have been numerically improved about one order of magnitude in comparison with those commonly used. A significant advantage of using a calibrated continued fraction mapping function for the astronomical refraction correction is to extend the coverage of the formulas to rather lower elevation observations with high accuracy. The corrections related to the finite distances of objects have been considered in detail. We have briefly analyzed the influences of the errors of atmospheric profile and of the deviation of atmospheric parameters. in order to match different requirements in astrometry and geodesy, we have considered the corrections at both radio and optical frequencies, respectively. The dispersion of signals at optical frequencies plays a primary role in astronomical refraction computation.

  5. Isaac Newton and the astronomical refraction.

    PubMed

    Lehn, Waldemar H

    2008-12-01

    In a short interval toward the end of 1694, Isaac Newton developed two mathematical models for the theory of the astronomical refraction and calculated two refraction tables, but did not publish his theory. Much effort has been expended, starting with Biot in 1836, in the attempt to identify the methods and equations that Newton used. In contrast to previous work, a closed form solution is identified for the refraction integral that reproduces the table for his first model (in which density decays linearly with elevation). The parameters of his second model, which includes the exponential variation of pressure in an isothermal atmosphere, have also been identified by reproducing his results. The implication is clear that in each case Newton had derived exactly the correct equations for the astronomical refraction; furthermore, he was the first to do so.

  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. Influence of refractive correction on ocular dominance

    NASA Astrophysics Data System (ADS)

    Nakayama, Nanami; Kawamorita, Takushi; Uozato, Hiroshi

    2010-07-01

    We investigated the effects of refractive correction and refractive defocus on the assessment of sensory ocular dominance. In 25 healthy subjects (4 males and 21 females) aged between 20 and 31 years, a quantitative measurement of sensory ocular dominance was performed with refractive correction and the addition of a positive lens on the dominant eye. Sensory ocular dominance was measured with a chart using binocular rivalry targets. The reversal point changed after the addition of a +1.00 D lens on the dominant eye in all subjects. However, sighting ocular dominance and stereopsis did not change after the addition of a positive lens on the dominant eye ( P > 0:05, Wilcoxon test). These results suggest that refractive correction affects sensory ocular dominance, indicating the possible development of a new type of occlusion for amblyopia in the future.

  8. REFractions: The Representing Equivalent Fractions Game

    ERIC Educational Resources Information Center

    Tucker, Stephen I.

    2014-01-01

    Stephen Tucker presents a fractions game that addresses a range of fraction concepts including equivalence and computation. The REFractions game also improves students' fluency with representing, comparing and adding fractions.

  9. Two Color Interferometry with Nonlinear Refractive Properties

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.

    2002-01-01

    Using nonlinear refractive properties of salt-water solution at two wavelengths, numerical analysis has been performed to extract temperature and concentration from virtual interferometric fringe data. The theoretical study, using a commercially available equation solving tool, starts with critical fringe counting needs and the role of nonlinear refractive properties in such measurements. Finally, methodology of the analysis, developed codes, and fringe counting accuracy needs are described in detail.

  10. 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.

  11. Indices of refraction for the HITRAN compilation

    NASA Technical Reports Server (NTRS)

    Massie, S. T.

    1994-01-01

    Indices of refraction of sulfuric acid solutions, water, and ice, which will become part of the HITRAN database, are discussed. Representative calculations are presented for the sulfate aerosol, to illustrate the broadband spectral features of i.r. aerosol extinction spectra. Values of the sulfuric acid mass density are used in an application of the Lorentz-Lorenz equation, which is used to estimate the sensitivity of extinction coefficients to temperature dependent refractive indices.

  12. ON THE SOURCE OF ASTROMETRIC ANOMALOUS REFRACTION

    SciTech Connect

    Taylor, M. Suzanne; McGraw, John T.; Zimmer, Peter C.; Pier, Jeffrey R.

    2013-03-15

    More than a century ago, astronomers using transit telescopes to determine precise stellar positions were hampered by an unexplained periodic shifting of the stars they were observing. With the advent of CCD transit telescopes in the past three decades, this unexplained motion, termed 'anomalous refraction' by these early astronomers, is again being observed. Anomalous refraction is described as a low-frequency, large angular scale ({approx}2 Degree-Sign ) motion of the entire image plane with respect to the celestial coordinate system as observed and defined by astrometric catalogs. These motions, of typically several tenths of an arcsecond amplitude with timescales on the order of 10 minutes, are ubiquitous to ground-based drift-scan astrometric measurements regardless of location or telescopes used and have been attributed to the effect of tilting of equal-density layers of the atmosphere. The cause of this tilting has often been attributed to atmospheric gravity waves, but this cause has never been confirmed. Although theoretical models of atmospheric refraction show that atmospheric gravity waves are a plausible cause of anomalous refraction, an observational campaign specifically directed at defining this relationship provides clear evidence that anomalous refraction is not consistent with the passage of atmospheric gravity waves. The source of anomalous refraction is found to be meter-scale, slowly evolving quasi-coherent dynamical structures in the boundary layer below 60 m above ground level.

  13. Interferometric Methods of Measuring Refractive Indices and Double-Refraction of Fibres.

    ERIC Educational Resources Information Center

    Hamza, A. A.; El-Kader, H. I. Abd

    1986-01-01

    Presents two methods used to measure the refractive indices and double-refraction of fibers. Experiments are described, with one involving the use of Pluta microscope in the double-beam interference technique, the other employing the multiple-beam technique. Immersion liquids are discussed that can be used in the experiments. (TW)

  14. 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.

  15. Refractive error sensing from wavefront slopes.

    PubMed

    Navarro, Rafael

    2010-01-01

    The problem of measuring the objective refractive error with an aberrometer has shown to be more elusive than expected. Here, the formalism of differential geometry is applied to develop a theoretical framework of refractive error sensing. At each point of the pupil, the local refractive error is given by the wavefront curvature, which is a 2 × 2 symmetric matrix, whose elements are directly related to sphere, cylinder, and axis. Aberrometers usually measure the local gradient of the wavefront. Then refractive error sensing consists of differentiating the gradient, instead of integrating as in wavefront sensing. A statistical approach is proposed to pass from the local to the global (clinically meaningful) refractive error, in which the best correction is assumed to be the maximum likelihood estimation. In the practical implementation, this corresponds to the mode of the joint histogram of the 3 different elements of the curvature matrix. Results obtained both in computer simulations and with real data provide a close agreement and consistency with the main optical image quality metrics such as the Strehl ratio.

  16. Refractive error sensing from wavefront slopes.

    PubMed

    Navarro, Rafael

    2010-01-01

    The problem of measuring the objective refractive error with an aberrometer has shown to be more elusive than expected. Here, the formalism of differential geometry is applied to develop a theoretical framework of refractive error sensing. At each point of the pupil, the local refractive error is given by the wavefront curvature, which is a 2 × 2 symmetric matrix, whose elements are directly related to sphere, cylinder, and axis. Aberrometers usually measure the local gradient of the wavefront. Then refractive error sensing consists of differentiating the gradient, instead of integrating as in wavefront sensing. A statistical approach is proposed to pass from the local to the global (clinically meaningful) refractive error, in which the best correction is assumed to be the maximum likelihood estimation. In the practical implementation, this corresponds to the mode of the joint histogram of the 3 different elements of the curvature matrix. Results obtained both in computer simulations and with real data provide a close agreement and consistency with the main optical image quality metrics such as the Strehl ratio. PMID:21149305

  17. Refractive Secondary Concentrators for Solar Thermal Applications

    NASA Technical Reports Server (NTRS)

    Wong, Wayne A.; Macosko, Robert P.

    1999-01-01

    The NASA Glenn Research Center is developing technologies that utilize solar energy for various space applications including electrical power conversion, thermal propulsion, and furnaces. Common to all of these applications is the need for highly efficient, solar concentration systems. An effort is underway to develop the innovative single crystal refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. The refractive secondary offers very high throughput efficiencies (greater than 90%), and when used in combination with advanced primary concentrators, enables very high concentration ratios (10,0(X) to 1) and very high temperatures (greater than 2000 K). Presented is an overview of the refractive secondary concentrator development effort at the NASA Glenn Research Center, including optical design and analysis techniques, thermal modeling capabilities, crystal materials characterization testing, optical coatings evaluation, and component testing. Also presented is a discussion of potential future activity and technical issues yet to be resolved. Much of the work performed to date has been in support of the NASA Marshall Space Flight Center's Solar Thermal Propulsion Program. The many benefits of a refractive secondary concentrator that enable efficient, high temperature thermal propulsion system designs, apply equally well to other solar applications including furnaces and power generation systems such as solar dynamics, concentrated thermal photovoltaics, and thermionics.

  18. Adjustable hybrid diffractive/refractive achromatic lens.

    PubMed

    Valley, Pouria; Savidis, Nickolaos; Schwiegerling, Jim; Dodge, Mohammad Reza; Peyman, Gholam; Peyghambarian, N

    2011-04-11

    We demonstrate a variable focal length achromatic lens that consists of a flat liquid crystal diffractive lens and a pressure-controlled fluidic refractive lens. The diffractive lens is composed of a flat binary Fresnel zone structure and a thin liquid crystal layer, producing high efficiency and millisecond switching times while applying a low ac voltage input. The focusing power of the diffractive lens is adjusted by electrically modifying the sub-zones and re-establishing phase wrapping points. The refractive lens includes a fluid chamber with a flat glass surface and an opposing elastic polydimethylsiloxane (PDMS) membrane surface. Inserting fluid volume through a pump system into the clear aperture region alters the membrane curvature and adjusts the refractive lens' focal position. Primary chromatic aberration is remarkably reduced through the coupling of the fluidic and diffractive lenses at selected focal lengths. Potential applications include miniature color imaging systems, medical and ophthalmic devices, or any design that utilizes variable focal length achromats.

  19. Seismic refraction analysis: the path forward

    USGS Publications Warehouse

    Haines, Seth S.; Zelt, Colin; Doll, William

    2012-01-01

    Seismic Refraction Methods: Unleashing the Potential and Understanding the Limitations; Tucson, Arizona, 29 March 2012 A workshop focused on seismic refraction methods took place on 29 May 2012, associated with the 2012 Symposium on the Application of Geophysics to Engineering and Environmental Problems. This workshop was convened to assess the current state of the science and discuss paths forward, with a primary focus on near-surface problems but with an eye on all applications. The agenda included talks on these topics from a number of experts interspersed with discussion and a dedicated discussion period to finish the day. Discussion proved lively at times, and workshop participants delved into many topics central to seismic refraction work.

  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. 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.

  2. Refraction of microwave signals by water vapor

    NASA Technical Reports Server (NTRS)

    Goldfinger, A. D.

    1980-01-01

    Tropospheric water vapor causes a refractive path length effect which is typically 5-10% of the 'dry' tropospheric effect and as large as several meters at elevation angles below 5 deg. The vertical water vapor profile is quite variable, and measurements of intensive atmospheric parameters such as temperature and humidity limited to the surface do not adequately predict the refractive effect. It is suggested that a water vapor refraction model that is a function of the amount of precipitable water alone can be successful at low elevation angles. From an extensive study of numerical ray tracings through radiosonde balloon data, such a model has been constructed. The model predicts the effect at all latitudes and elevation angles between 2 and 10 deg to an accuracy of better than 4% (11 cm at 3 deg elevation angle).

  3. Removing singular refractive indices with sculpted surfaces

    PubMed Central

    Horsley, S. A. R.; Hooper, I. R.; Mitchell–Thomas, R. C.; Quevedo–Teruel, O.

    2014-01-01

    The advent of Transformation Optics established the link between geometry and material properties, and has resulted in a degree of control over electromagnetic fields that was previously impossible. For waves confined to a surface it is known that there is a simpler, but related, geometrical equivalence between the surface shape and the refractive index, and here we demonstrate that conventional devices possessing a singularity — that is, the requirement of an infinite refractive index — can be realised for waves confined to an appropriately sculpted surface. In particular, we redesign three singular omnidirectional devices: the Eaton lens, the generalized Maxwell Fish–Eye, and the invisible sphere. Our designs perfectly reproduce the behaviour of these singular devices, and can be achieved with simple isotropic media of low refractive index contrast. PMID:24786649

  4. 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.

  5. Evidence of local effects in anomalous refraction and focusing properties of dodecagonal photonic quasicrystals

    NASA Astrophysics Data System (ADS)

    di Gennaro, Emiliano; Miletto, Carlo; Savo, Salvatore; Andreone, Antonello; Morello, Davide; Galdi, Vincenzo; Castaldi, Giuseppe; Pierro, Vincenzo

    2008-05-01

    We present the key results from a comprehensive study of the refraction and focusing properties of a two-dimensional dodecagonal photonic “quasicrystal” (PQC), which was carried out via both full-wave numerical simulations and microwave measurements on a slab made of alumina rods inserted in a parallel-plate waveguide. We observe an anomalous refraction and focusing in several frequency regions, which confirm some recently published results. However, our interpretation, which is based on numerical and experimental evidence, substantially differs from the one in terms of “effective negative refractive index” that was originally proposed. Instead, our study highlights the critical role played by short-range interactions associated with local order and symmetry.

  6. Refractive acoustic devices for airborne sound.

    PubMed

    Cervera, F; Sanchis, L; Sánchez-Pérez, J V; Martínez-Sala, R; Rubio, C; Meseguer, F; López, C; Caballero, D; Sánchez-Dehesa, J

    2002-01-14

    We show that a sonic crystal made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. It is demonstrated that, in the long-wave regime, the crystal has low impedance and the sound is transmitted at subsonic velocities. Here, the fabrication and characterization of a convergent lens are presented. Also, an example of a Fabry-Perot interferometer based on this crystal is analyzed. It is concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems.

  7. 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.

  8. 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.

  9. Refractive acoustic devices for airborne sound.

    PubMed

    Cervera, F; Sanchis, L; Sánchez-Pérez, J V; Martínez-Sala, R; Rubio, C; Meseguer, F; López, C; Caballero, D; Sánchez-Dehesa, J

    2002-01-14

    We show that a sonic crystal made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. It is demonstrated that, in the long-wave regime, the crystal has low impedance and the sound is transmitted at subsonic velocities. Here, the fabrication and characterization of a convergent lens are presented. Also, an example of a Fabry-Perot interferometer based on this crystal is analyzed. It is concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems. PMID:11801014

  10. Implantable collamer lens for residual refractive error after corneal refractive surgery

    PubMed Central

    Chen, Xun; Wang, Xiao-Ying; Zhang, Xi; Chen, Zhi; Zhou, Xing-Tao

    2016-01-01

    AIM To assess the safety, efficacy, predictability and stability of implantable collamer lens (ICL) for residual refractive error after corneal refractive surgery. METHODS This study evaluated 19 eyes of 12 patients who underwent ICL implantation after corneal refractive surgeries. They were followed up for 1y to 5y of uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refractive error, flat and steep K value, axial length, intraocular pressure, corneal endothelial cell density, adverse events after ICL surgery. RESULTS The mean follow-up period was 39.05±19.22 mo (range, 1-5y). Spherical equivalent refractive error changed from -7.45±3.02 D preoperatively to -0.85±1.10 D 1wk to 1mo after ICL implantation, with the safety and efficacy indices being 1.12 and 1.15, respectively. A total of 52.63% of eyes were within ±0.5 D of the predicted spherical equivalents, 73.68% were within ±1.0 D. A trend of mild regression towards myopia with axial elongation after 5y was observed. One eye with mild anterior capsule opacity and retinal detachment 1y after surgery were observed. CONCLUSION ICL implantation is safe and effective for the correction of residual refractive error after corneal refractive surgeries, especially in moderate to high residual myopia. PMID:27803858

  11. 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.

  12. Calculations of atmospheric refraction for spacecraft remote-sensing applications

    NASA Technical Reports Server (NTRS)

    Chu, W. P.

    1983-01-01

    Analytical solutions to the refraction integrals appropriate for ray trajectories along slant paths through the atmosphere are derived in this paper. This type of geometry is commonly encountered in remote-sensing applications utilizing an occultation technique. The solutions are obtained by evaluating higher-order terms from expansion of the refraction integral and are dependent on the vertical temperature distributions. Refraction parameters such as total refraction angles, air masses, and path lengths can be accurately computed. It is also shown that the method can be used for computing refraction parameters in astronomical refraction geometry for large zenith angles.

  13. Joint analysis of refractions with surface waves: An inverse solution to the refraction-traveltime problem

    USGS Publications Warehouse

    Ivanov, J.; Miller, R.D.; Xia, J.; Steeples, D.; Park, C.B.

    2006-01-01

    We describe a possible solution to the inverse refraction-traveltime problem (IRTP) that reduces the range of possible solutions (nonuniqueness). This approach uses a reference model, derived from surface-wave shear-wave velocity estimates, as a constraint. The application of the joint analysis of refractions with surface waves (JARS) method provided a more realistic solution than the conventional refraction/tomography methods, which did not benefit from a reference model derived from real data. This confirmed our conclusion that the proposed method is an advancement in the IRTP analysis. The unique basic principles of the JARS method might be applicable to other inverse geophysical problems. ?? 2006 Society of Exploration Geophysicists.

  14. Broadband negative optical constants in composite materials

    NASA Astrophysics Data System (ADS)

    Khosravi, S.; Rostami, A.; Rostami, G.; Dolatyari, M.

    2015-04-01

    Capability of flexible composite substrates, consisting of randomly distributed nanoparticles in polymeric host medium, to illustrate negative effective permittivity and permeability in the mid infrared wavelengths (3-5 μm) is investigated. To produce negative permittivity in the desired wavelength range, we proposed a structure in which plasmonic nanoparticles (doped semiconductors or metallic nanoparticles) are inserted inside polytetrafluoroethylene as the low refractive index polymeric medium. Also, the optical properties of the structures including core/shell nanoparticles in polytetrafluoroethylene host (with polytetrafluoroethylene as core material and dielectric shells possessing higher refractive index compared to refractive index of the host medium) are investigated. It is shown that, high refractive index dielectric shells result in negative μeff in these structures. As a basic idea, to obtain negative optical constants in broad wavelength range, superposition of the mentioned nanoparticles in the polymeric host is examined. The advantages and limitations of the proposed structure are carefully investigated. Moreover, based on the simulation results, we will introduce flexible media that simultaneously display negative permittivity and permeability in the wavelength range of interest. Capability of two types of composites (the first one contains mixture of plasmonic nanoparticles with polymer-dielectric core-shell nanoparticles and the second one includes metal-dielectric core-shell nanoparticles in the polymeric host) to produce both negative effective parameters in the desired wavelength range are investigated and compared together. Finally a polymeric medium with random distribution of core-shell (metal-dielectric) nanoparticles and plasmonic nanoparticles is introduced as an optimal medium to illustrate negative optical constants in mid infrared wavelengths. Clausius-Mossotti formula is used to calculate the effective parameters.

  15. Refractive Indices of Gases at Microwave Frequencies

    ERIC Educational Resources Information Center

    Goodhead, D. T.; And Others

    1976-01-01

    Describes a simple microwave interferometer capable of measuring small phase shifts. Proposes laboratory exercises involving the use of the interferometer in the determination of refractive indices of gases and the analysis of the reflection in a test chamber. (Author/CP)

  16. Blending History with Physics: Acoustic Refraction.

    ERIC Educational Resources Information Center

    Ross, Charles D.

    2000-01-01

    Argues that the study of refraction of sound waves, although usually neglected, is an excellent ancillary to the normal optical approach in physics courses. Discusses the historical context of interest in the science behind outdoor sound propagation, particularly during the Civil War in the United States. (WRM)

  17. A Mechanical Analogue of the Refracting Telescope

    ERIC Educational Resources Information Center

    Vannoni, Maurizio; Molesini, Giuseppe; Sordini, Andrea; Straulino, Samuele

    2011-01-01

    The recent celebration of the discoveries made by Galileo four centuries ago has attracted new attention to the refracting telescope and to its use as an instrument for the observation of the night sky. This has offered the opportunity for addressing in the classroom the basic principles explaining the operation of the telescope. When doing so, a…

  18. Validation of Ray Tracing Code Refraction Effects

    NASA Technical Reports Server (NTRS)

    Heath, Stephanie L.; McAninch, Gerry L.; Smith, Charles D.; Conner, David A.

    2008-01-01

    NASA's current predictive capabilities using the ray tracing program (RTP) are validated using helicopter noise data taken at Eglin Air Force Base in 2007. By including refractive propagation effects due to wind and temperature, the ray tracing code is able to explain large variations in the data observed during the flight test.

  19. Compound refractive X-ray lens

    DOEpatents

    Nygren, David R.; Cahn, Robert; Cederstrom, Bjorn; Danielsson, Mats; Vestlund, Jonas

    2000-01-01

    An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point.

  20. Relocation of Groningen seismicity using refracted waves

    NASA Astrophysics Data System (ADS)

    Ruigrok, E.; Trampert, J.; Paulssen, H.; Dost, B.

    2015-12-01

    The Groningen gas field is a giant natural gas accumulation in the Northeast of the Netherlands. The gas is in a reservoir at a depth of about 3 km. The naturally-fractured gas-filled sandstone extends roughly 45 by 25 km laterally and 140 m vertically. Decades of production have led to significant compaction of the sandstone. The (differential) compaction is thought to have reactivated existing faults and being the main driver of induced seismicity. Precise earthquake location is difficult due to a complicated subsurface, and that is the likely reason, the current hypocentre estimates do not clearly correlate with the well-known fault network. The seismic velocity model down to reservoir depth is quite well known from extensive seismic surveys and borehole data. Most to date earthquake detections, however, were made with a sparse pre-2015 seismic network. For shallow seismicity (<5 km depth) horizontal source-receiver distances tend to be much larger than vertical distances. Consequently, preferred source-receiver travel paths are refractions over high-velocity layers below the reservoir. However, the seismic velocities of layers below the reservoir are poorly known. We estimated an effective velocity model of the main refracting layer below the reservoir and use this for relocating past seismicity. We took advantage of vertical-borehole recordings for estimating precise P-wave (refraction) onset times and used a tomographic approach to find the laterally varying velocity field of the refracting layer. This refracting layer is then added to the known velocity model, and the combined model is used to relocate the past seismicity. From the resulting relocations we assess which of the faults are being reactivated.

  1. Specific features of measuring the optical power of artificial refractive and diffractive-refractive eye lenses

    NASA Astrophysics Data System (ADS)

    Lenkova, G. A.

    2016-08-01

    Methods for monitoring the optical power of artificial refractive eye lenses (intraocular lenses) based on measuring focal lengths in air and in medium are analyzed. The methods for determining the refraction of diffractive-refractive lenses (in particular, of MIOL-Akkord type), with allowance for the specific features of the diffractive structure, are considered. A computer simulation of the measurement of the focal length of MIOL-Akkord lenses is performed. The effective optical power of the diffractive component of these lenses is shown to depend on the diaphragm diameter. The optimal diaphragm diameter, at which spherical aberrations do not affect the position of foci, is found to be 3 mm. Possible errors in measuring the focal lengths are analyzed, and the necessary corrections that must be introduced into measurement results and calculations of refractions are determined.

  2. 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.

  3. Automatic Refraction: How It Is Done: Some Clinical Results

    ERIC Educational Resources Information Center

    Safir, Aran; And Others

    1973-01-01

    Compaired are methods of determining visual refraction needs of young children or other unreliable observers by means of retinosocopy or the Opthalmetron, an automatic instrument which can be operated by a technician with no knowledge of refraction. (DB)

  4. Is LASIK for Me? A Patient's Guide to Refractive Surgery

    MedlinePlus

    ... were developed with the help of the Federal Trade Commission and the American Society of Cataract and Refractive Surgery. For the complete guidelines, see: www.aao.org/about/policy/upload/Guidelines-for-Refractive-Surgery- Advertising-3-26- ...

  5. Refractive Indices of Asian Dust in Mid-Infrared Region

    NASA Astrophysics Data System (ADS)

    Lee, K.; Park, J.

    2013-12-01

    Optical constants of Asian dust are determined based on mineral compositions of aerosols sampled at Seoul, Korea. Complex refractive index for labradorite (plagioclase) and orthoclase (K-feldspar), which are component minerals of Asian dust, are calculated from the dispersion theory using reflectance data of the Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER). The optical constants of Asian dust are compared with those of other dust aerosols. Simulated brightness temperatures of satellite measurement using the present optical constants for a typical loading of Asian dust aerosols show spectral features of the Atmospheric Infrared Sounder (AIRS) data for an Asian dust storm. Measured and simulated spectral locations of the maximum brightness temperature are in good agreement. Simulated data show the negative slope in the region of 800-1000 cm-1. Brightness temperature of AIRS near 1233 cm-1 being lower than the maximum near 832 cm-1 can also be simulated using the optical constants of Asian dust.

  6. [Results of refractive surgery in hyperopic and combined astigmatism].

    PubMed

    Vlaicu, Valeria

    2013-01-01

    The refractive surgery includes a lot of procedures for changing the refraction of the eye to obtain a better visual acuity with no glasses or contact lenses. LASIK is the most commonly performed laser refractive surgery today. The goal is to present the postoperative evolution of the refraction and visual acuity after LASIK for Mixed and Hyperopic Astigmatism. The results show that LASIK is safe and predictible if we have well performed interventions and well-selected patients.

  7. EDITORIAL: Sensitive structures: refractive indices in nanotechnology Sensitive structures: refractive indices in nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2012-12-01

    Refractive index effects using nanoscale systems are frequently applied in new imaging, sensing and even visibility cloaking technology. In this issue, researchers in Japan use simulations and experiments to describe the confinement of optical vortices in nanoscale fin structures and the sensitivity of these systems to the refractive index of the surrounding media [1]. The effects of refraction as light rays pass between different media were recorded as long ago as the first century AD, by Ptolemy [2]. Over the following centuries the phenomena inspired Ibn Sahl in 984 [3], Thomas Harriot in 1602 [4], Willebrord Snellius in 1621 [5] and Rene Descartes in 1637 [6] to independently derive the more accurate and elegant equation for refraction so familiar to us today. Recent studies of the interactions between light and matter continue to reveal a wealth of phenomena that originate in the effects of the refractive indices of materials. Nanostructures can be used to manipulate conditions that affect the refractive indices of materials, such as temperature. A E Aliev et al at the University of Texas reported a striking demonstration of temperature-dependent refractive index effects using a free-standing, highly aligned carbon nanotube aerogel sheet [7]. They used the extremely low thermal capacitance and high heat transfer ability of transparent carbon nanotube sheets to enable high-frequency modulation of the sheet temperature over an enormous temperature range. The resulting sharp, rapidly changing gradient of the refractive index in the surrounding liquid or gas makes objects seem to disappear and can be used for visibility cloaking. Light-matter interaction resonances, where light is confined at the nanoscale, can be extremely sensitive to changes in the refractive index of the surrounding media [8], even allowing single-molecule detection [9]. Plasmons, the collective oscillations of electrons in response to incident light, are a typical example. Researchers at Rice

  8. Shuttle program: Computing atmospheric scale height for refraction corrections

    NASA Technical Reports Server (NTRS)

    Lear, W. M.

    1980-01-01

    Methods for computing the atmospheric scale height to determine radio wave refraction were investigated for different atmospheres, and different angles of elevation. Tables of refractivity versus altitude are included. The equations used to compute the refraction corrections are given. It is concluded that very accurate corrections are determined with the assumption of an exponential atmosphere.

  9. Low-loss negative index metamaterials for X, Ku, and K microwave bands

    NASA Astrophysics Data System (ADS)

    Lee, David A.; Vedral, L. James; Smith, David A.; Musselman, Randall L.; Pinchuk, Anatoliy O.

    2015-04-01

    Low-loss, negative-index of refraction metamaterials were designed and tested for X, Ku, and K microwave frequency bands. An S-shaped, split-ring resonator was used as a unit cell to design homogeneous slabs of negative-index metamaterials. Then, the slabs of metamaterials were cut unto prisms to measure experimentally the negative index of refraction of a plane electromagnetic wave. Theoretical simulations using High-Frequency Structural Simulator, a finite element equation solver, were in good agreement with experimental measurements. The negative index of refraction was retrieved from the angle- and frequency-dependence of the transmitted intensity of the microwave beam through the metamaterial prism and compared well to simulations; in addition, near-field electromagnetic intensity mapping was conducted with an infrared camera, and there was also a good match with the simulations for expected frequency ranges for the negative index of refraction.

  10. Low-loss negative index metamaterials for X, Ku, and K microwave bands

    SciTech Connect

    Lee, David A.; Vedral, L. James; Smith, David A.; Pinchuk, Anatoliy O.; Musselman, Randall L.

    2015-04-15

    Low-loss, negative-index of refraction metamaterials were designed and tested for X, Ku, and K microwave frequency bands. An S-shaped, split-ring resonator was used as a unit cell to design homogeneous slabs of negative-index metamaterials. Then, the slabs of metamaterials were cut unto prisms to measure experimentally the negative index of refraction of a plane electromagnetic wave. Theoretical simulations using High-Frequency Structural Simulator, a finite element equation solver, were in good agreement with experimental measurements. The negative index of refraction was retrieved from the angle- and frequency-dependence of the transmitted intensity of the microwave beam through the metamaterial prism and compared well to simulations; in addition, near-field electromagnetic intensity mapping was conducted with an infrared camera, and there was also a good match with the simulations for expected frequency ranges for the negative index of refraction.

  11. 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

  12. Babinet's principle in double-refraction systems

    NASA Astrophysics Data System (ADS)

    Ropars, Guy; Le Floch, Albert

    2014-06-01

    Babinet's principle applied to systems with double refraction is shown to involve spatial interchanges between the ordinary and extraordinary patterns observed through two complementary screens. As in the case of metamaterials, the extraordinary beam does not follow the Snell-Descartes refraction law, the superposition principle has to be applied simultaneously at two points. Surprisingly, by contrast to the intuitive impression, in the presence of the screen with an opaque region, we observe that the emerging extraordinary photon pattern, which however has undergone a deviation, remains fixed when a natural birefringent crystal is rotated while the ordinary one rotates with the crystal. The twofold application of Babinet's principle implies intensity and polarization interchanges but also spatial and dynamic interchanges which should occur in birefringent metamaterials.

  13. Transverse chromatic aberration after corneal refractive surgery

    NASA Astrophysics Data System (ADS)

    Anera, R. G.; Jiménez, J. R.; Jiménez del Barco, L.; Hita, E.

    2005-05-01

    An expression has been deduced theoretically from a schematic-eye model, for the transverse or lateral chromatic aberration (TCA) after refractive surgery. The aim was to investigate analytically how chromatic aberration varies after the emmetropization process. These changes in the TCA have been characterized from changes in corneal asphericity. The results indicate that TCA after refractive surgery diminishes as the degree of myopia increases, a trend contrary to that occurring with monochromatic aberrations, such as spherical or coma. These results can explain the fact that the real deterioration of the visual function under photopic conditions detected in those operated on for myopia is less than expected when only monochromatic aberrations are taken into account.

  14. Refractive scintillation in the interstellar medium

    NASA Astrophysics Data System (ADS)

    Coles, W. A.; Rickett, B. J.; Codona, J. L.; Frehlich, R. G.

    1987-04-01

    The slow variation in the apparent intensity of pulsars on time scales of days to months was recently shown to be due to a large-scale component of interstellar scintillation (Rickett, Coles, and Bourgois). These variations are greater than one would expect if the turbulence spectrum were a simple Kolmogorov power law. It is shown that this large-scale component can be greatly enhanced when the turbulence spectrum has a limiting "inner scale" of the order of 109m. The authors present a solution for the covariance of refractive scintillation of an extended source in an extended medium. The results show that refractive scintillations are also responsible for slow variations in "low-frequency variables".

  15. 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.

  16. Neutrino refraction by the cosmic neutrino background

    NASA Astrophysics Data System (ADS)

    Díaz, J. S.; Klinkhamer, F. R.

    2016-03-01

    We have determined the dispersion relation of a neutrino test particle propagating in the cosmic neutrino background. Describing the relic neutrinos and antineutrinos from the hot big bang as a dense medium, a matter potential or refractive index is obtained. The vacuum neutrino mixing angles are unchanged, but the energy of each mass state is modified. Using a matrix in the space of neutrino species, the induced potential is decomposed into a part which produces signatures in beta-decay experiments and another part which modifies neutrino oscillations. The low temperature of the relic neutrinos makes a direct detection extremely challenging. From a different point of view, the identified refractive effects of the cosmic neutrino background constitute an ultralow background for future experimental studies of nonvanishing Lorentz violation in the neutrino sector.

  17. Determining the refractive index variation within panes of vehicle windshield glass.

    PubMed

    Munger, Crystal; Gates, Kris M; Hamburg, Christopher

    2014-09-01

    Refractive indices of seven double-paned vehicle windshields were measured to assess the variation across the pane of glass and to evaluate collection techniques for known glass standards by comparing false negative rates. Measurements were made using a Foster and Freeman GRIM3 instrument, and a minimum of 240 measurements were made per pane. The mean SD of the windshields was 0.00004. It was further determined that collecting a known sample from two different sections of a shattered windshield gave the lowest rate of false negatives when using ± 2 standard deviations to estimate the RI variation of the known glass. Additionally, refractive indices often were highest in the center of the windshield and decreased toward the left and right edges; in approximately half the sample set, the two panes of a single windshield were differentiated by one or more properties.

  18. Emerging Technology in Refractive Cataract Surgery

    PubMed Central

    Saraiva, João; Neatrour, Kristin; Waring IV, George O.

    2016-01-01

    Technology in cataract surgery is constantly evolving to meet the goals of both surgeons and patients. Recent major advances in refractive cataract surgery include innovations in preoperative and intraoperative diagnostics, femtosecond laser-assisted cataract surgery (FLACS), and a new generation of intraocular lenses (IOLs). This paper presents the latest technologies in each of these major categories and discusses how these contributions serve to improve cataract surgery outcomes in a safe, effective, and predictable manner. PMID:27433353

  19. Nonlinear refraction and reflection travel time tomography

    USGS Publications Warehouse

    Zhang, Jiahua; ten Brink, U.S.; Toksoz, M.N.

    1998-01-01

    We develop a rapid nonlinear travel time tomography method that simultaneously inverts refraction and reflection travel times on a regular velocity grid. For travel time and ray path calculations, we apply a wave front method employing graph theory. The first-arrival refraction travel times are calculated on the basis of cell velocities, and the later refraction and reflection travel times are computed using both cell velocities and given interfaces. We solve a regularized nonlinear inverse problem. A Laplacian operator is applied to regularize the model parameters (cell slownesses and reflector geometry) so that the inverse problem is valid for a continuum. The travel times are also regularized such that we invert travel time curves rather than travel time points. A conjugate gradient method is applied to minimize the nonlinear objective function. After obtaining a solution, we perform nonlinear Monte Carlo inversions for uncertainty analysis and compute the posterior model covariance. In numerical experiments, we demonstrate that combining the first arrival refraction travel times with later reflection travel times can better reconstruct the velocity field as well as the reflector geometry. This combination is particularly important for modeling crustal structures where large velocity variations occur in the upper crust. We apply this approach to model the crustal structure of the California Borderland using ocean bottom seismometer and land data collected during the Los Angeles Region Seismic Experiment along two marine survey lines. Details of our image include a high-velocity zone under the Catalina Ridge, but a smooth gradient zone between. Catalina Ridge and San Clemente Ridge. The Moho depth is about 22 km with lateral variations. Copyright 1998 by the American Geophysical Union.

  20. The ionospheric refraction at 38 MHz.

    NASA Astrophysics Data System (ADS)

    Milogradov-Turin, J.

    The investigation of the observed shift of the North Polar Spur (NPS) at the 38 MHz survey of Milogradov-Turin and Smith (1973) in respect to the position of the NPS on the survey at 408 MHz convolved to the same resolution (Haslam and Salter 1977) has shown that there is no dependence of the NPS position on frequency and that the ionospheric refraction should be larger than believed.

  1. 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.

  2. 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.

  3. Autonomous satellite navigation by stellar refraction

    NASA Technical Reports Server (NTRS)

    Gounley, R.; White, R.; Gai, E.

    1983-01-01

    This paper describes an error analysis of an autonomous navigator using refraction measurements of starlight passing through the upper atmosphere. The analysis is based on a discrete linear Kalman filter. The filter generated steady-state values of navigator performance for a variety of test cases. Results of these simulations show that in low-earth orbit position-error standard deviations of less than 0.100 km may be obtained using only 40 star sightings per orbit.

  4. Lens Design Using Group Indices of Refraction

    NASA Technical Reports Server (NTRS)

    Vaughan, A. H.

    1995-01-01

    An approach to lens design is described in which the ratio of the group velocity to the speed of light (the group index) in glass is used, in conjunction with the more familiar phase index of refraction, to control certain chromatic properties of a system of thin lenses in contact. The first-order design of thin-lens systems is illustrated by examples incorporating the methods described.

  5. Emerging Technology in Refractive Cataract Surgery.

    PubMed

    Saraiva, João; Neatrour, Kristin; Waring Iv, George O

    2016-01-01

    Technology in cataract surgery is constantly evolving to meet the goals of both surgeons and patients. Recent major advances in refractive cataract surgery include innovations in preoperative and intraoperative diagnostics, femtosecond laser-assisted cataract surgery (FLACS), and a new generation of intraocular lenses (IOLs). This paper presents the latest technologies in each of these major categories and discusses how these contributions serve to improve cataract surgery outcomes in a safe, effective, and predictable manner. PMID:27433353

  6. Refraction effects of atmosphere on geodetic measurements to celestial bodies

    NASA Technical Reports Server (NTRS)

    Joshi, C. S.

    1973-01-01

    The problem is considered of obtaining accurate values of refraction corrections for geodetic measurements of celestial bodies. The basic principles of optics governing the phenomenon of refraction are defined, and differential equations are derived for the refraction corrections. The corrections fall into two main categories: (1) refraction effects due to change in the direction of propagation, and (2) refraction effects mainly due to change in the velocity of propagation. The various assumptions made by earlier investigators are reviewed along with the basic principles of improved models designed by investigators of the twentieth century. The accuracy problem for various quantities is discussed, and the conclusions and recommendations are summarized.

  7. 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

  8. 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.

  9. Laser refractive surgery: a review and current status

    NASA Astrophysics Data System (ADS)

    Ren, Qiushi; Keates, Richard H.; Hill, Richard A.; Berns, Michael W.

    1995-03-01

    The aim of corneal refractive surgery is to modify the anterior surface of the cornea for the correction of myopia, hyperopia, and astigmatism. The air-tear film interface is a powerful refractive surface. Small changes in the curvature can induce large shifts in refractive power. The exquisite nature of laser-tissue interaction with corneal tissue allows successful application of lasers for refractive surgery. Numerous systems have been developed for clinical applications. An overview is provided of the current clinical and research status of laser refractive surgery.

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. Advanced interferometric profile measurements through refractive media

    SciTech Connect

    Koev, Stephan T.; Ghodssi, Reza

    2008-09-15

    Optical profilers are valuable tools for the characterization of microelectromechanical systems (MEMSs). They use phase sifting interferometry (PSI) or vertical scanning interferometry to measure the topography of microscale structures with nanometer resolution. However, for many emerging MEMS applications, the sample needs to be imaged while placed in a liquid or in a package with a glass window. The increased refractive index of the transparent medium degrades the interference image contrast and prevents any measurement of the sample. We report on the modification of a Veeco NT1100 optical profiler to enable PSI measurements through refractive media. This approach can be applied to any other optical profiler with PSI capability. The modification consists in replacing the original illumination source with a custom-built narrow linewidth source, which increases the coherence length of the light and the contrast of the interference image. We present measurements taken with the modified configuration on samples covered with 3 mm water or 500 {mu}m glass, and we compare them to measurements of uncovered samples. We show that the measurement precision is only slightly reduced by the water and glass, and that it is still sufficiently high for typical MEMS applications. The described method can be readily used for measuring through other types and thicknesses of refractive materials.

  15. Compound Refractive Lenses for Thermal Neutron Applications

    SciTech Connect

    Gary, Charles K.

    2013-11-12

    This project designed and built compound refractive lenses (CRLs) that are able to focus, collimate and image using thermal neutrons. Neutrons are difficult to manipulate compared to visible light or even x rays; however, CRLs can provide a powerful tool for focusing, collimating and imaging neutrons. Previous neutron CRLs were limited to long focal lengths, small fields of view and poor resolution due to the materials available and manufacturing techniques. By demonstrating a fabrication method that can produce accurate, small features, we have already dramatically improved the focal length of thermal neutron CRLs, and the manufacture of Fresnel lens CRLs that greatly increases the collection area, and thus efficiency, of neutron CRLs. Unlike a single lens, a compound lens is a row of N lenslets that combine to produce an N-fold increase in the refraction of neutrons. While CRLs can be made from a variety of materials, we have chosen to mold Teflon lenses. Teflon has excellent neutron refraction, yet can be molded into nearly arbitrary shapes. We designed, fabricated and tested Teflon CRLs for neutrons. We demonstrated imaging at wavelengths as short as 1.26 ? with large fields of view and achieved resolution finer than 250 μm which is better than has been previously shown. We have also determined designs for Fresnel CRLs that will greatly improve performance.

  16. Designing refractive beam shapers via aberration theory

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Shealy, David

    2014-10-01

    In this paper, we use aberration theory to design a refractive laser beam shaper in the configuration of two-aspheric lenses, whose analytical equations are known, but rather complicated. Specifically, we use results from third order aberration theory to obtain the parameters of the refracting laser beam shaper from the transverse aberration, which are then used as a starting point for further optimization by using optical design software. This approach was developed during the beginning of the twentieth century, works well for systems with a low numerical aperture, and allows one to define the following parameters of an optical system: radii of curvature, indices of refraction, thicknesses or air gaps, and conic constants of second order aspheric surfaces. We shall consider surfaces of the second-order spherical and conic sections and shall consider the example of designing of a two-lens beam shaper of the Keplerian 1-to-1 telescopic design providing a theoretical flat phase front and a flat-top irradiance profile of the output beam, where the ray mapping function from the input aperture to the output aperture is known from the literature. Explicit expression for third order longitudinal aberration and the Seidel coefficients are expressed in terms beam waist and input beam geometrical parameter, indices, lens radii and conic constants.

  17. 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).

  18. Negative necrotaxis.

    PubMed

    Ragot, R

    1993-01-01

    We studied necrotaxis in several strains of protists and compared the reaction of living cells in the vicinity of cells killed by a ruby laser. Negative necrotaxis was observed for the unicellular green alga Euglena gracilis, whereas Chlamydomonas was shown to exhibit positive necrotaxis. The cellular colony Pandorina morum exhibited no reaction to the killing of nearby colonies. Both the colorless cryptomonad Chilomonas paramecium and the ciliate Tetrahymena pyriformis exhibited negative necrotaxis following the lysis of vitally stained specimens of their own species. They also exhibited negative necrotaxis following the lysis of Euglena cells. It was also demonstrated that the cellular content of Euglena cells lysed by heat or by a mechanical procedure acts as a repellent to intact Euglena cells. These results suggest that the negative necrotaxis provoked in Euglena by the laser irradiation is probably due to the chemotactic effect produced by the release of cell content in the extracellular medium. This cell content could, according to its chemical composition, act either as a repellent, an attractant, or be inactive. The sensitivity of cells (specific or nonspecific ion channels or chemoreceptors) are also of prime importance in the process.

  19. Electromagnetic field energy density in homogeneous negative index materials.

    PubMed

    Shivanand; Webb, Kevin J

    2012-05-01

    An exact separation of both electric and magnetic energies into stored and lost energies is shown to be possible in the special case when the wave impedance is independent of frequency. A general expression for the electromagnetic energy density in such a dispersive medium having a negative refractive index is shown to be accurate in comparison with numerical results. Using an example metamaterial response that provides a negative refractive index, it is shown that negative time-averaged stored energy can occur. The physical meaning of this negative energy is explained as the energy temporarily borrowed by the field from the material. This observation for negative index materials is of interest when approaching properties for a perfect lens. In the broader context, the observation of negative stored energy is of consequence in the study of dispersive materials. PMID:22712096

  20. Deviations of Lambert-Beer's law affect corneal refractive parameters after refractive surgery.

    PubMed

    Jiménez, José R; Rodríguez-Marín, Francisco; Anera, Rosario G; Jiménez Del Barco, Luis

    2006-06-12

    We calculate whether deviations of Lambert-Beer's law, which regulates depth ablation during corneal ablation, significantly influence corneal refractive parameters after refractive surgery and whether they influence visual performance. For this, we compute a point-to-point correction on the cornea while assuming a non-linear (including a quadratic term) fit for depth ablation. Post-surgical equations for refractive parameters using a non-linear fit show significant differences with respect to parameters obtained from a linear fit (Lambert-Beer's law). Differences were also significant for corneal aberrations. These results show that corneal-ablation algorithms should include analytical information on deviations from Lambert-Beer's law for achieving an accurate eye correction.

  1. The measurement of patient-reported outcomes of refractive surgery: the refractive status and vision profile.

    PubMed Central

    Schein, O D

    2000-01-01

    PURPOSE: To develop a questionnaire, the Refractive Status and Vision Profile (RSVP), to assess health-related quality of life associated with refractive error and its correction. METHODS: The published literature on patient report of visual and overall function was reviewed, and the RSVP was self-administered by 550 participants with refractive error. Cross-sectional validation was performed using standard psychometric techniques. The responsiveness of the RSVP to surgical intervention was assessed prospectively in a subset of 176 patients. The principal outcomes measures were scores on the overall RSVP scale (S) and on 8 RSVP subscales (functioning, driving, concern, expectations, symptoms, glare, optical problems, problems with corrective lenses). RESULTS: The RSVP (S) and its subscales demonstrated very good internal consistency (Cronbach's alpha, 0.70-0.93). S and several subscale scores were independently associated with satisfaction with vision and were more correlated with satisfaction with vision than with either visual acuity or refractive error. Higher refractive error was associated with lower scores on S and on 5 subscales. In the prospective surgical cohort, 15% of patients had some worsening in their total RSVP score; however, substantial variation was seen in the individual subscales where worsening ranged from 7% (problems with corrective lenses) to 41% (driving). The effect size (measure of responsiveness) of the RSVP and most of its subscales was very high. Approximately 14% of patients had significant worsening in 3 or more subscales, and this outcome was found to be independently associated with being dissatisfied with vision following surgery (OR, 5.84; 95% CI, 1.88, 8.13). CONCLUSIONS: The RSVP has been validated as a questionnaire that measures patient-reported quality of life related to refractive error and its correction. It is responsive to surgical intervention and provides important information regarding patient outcomes not available

  2. 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.

  3. 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.

  4. EDITORIAL: Sensitive structures: refractive indices in nanotechnology Sensitive structures: refractive indices in nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2012-12-01

    Refractive index effects using nanoscale systems are frequently applied in new imaging, sensing and even visibility cloaking technology. In this issue, researchers in Japan use simulations and experiments to describe the confinement of optical vortices in nanoscale fin structures and the sensitivity of these systems to the refractive index of the surrounding media [1]. The effects of refraction as light rays pass between different media were recorded as long ago as the first century AD, by Ptolemy [2]. Over the following centuries the phenomena inspired Ibn Sahl in 984 [3], Thomas Harriot in 1602 [4], Willebrord Snellius in 1621 [5] and Rene Descartes in 1637 [6] to independently derive the more accurate and elegant equation for refraction so familiar to us today. Recent studies of the interactions between light and matter continue to reveal a wealth of phenomena that originate in the effects of the refractive indices of materials. Nanostructures can be used to manipulate conditions that affect the refractive indices of materials, such as temperature. A E Aliev et al at the University of Texas reported a striking demonstration of temperature-dependent refractive index effects using a free-standing, highly aligned carbon nanotube aerogel sheet [7]. They used the extremely low thermal capacitance and high heat transfer ability of transparent carbon nanotube sheets to enable high-frequency modulation of the sheet temperature over an enormous temperature range. The resulting sharp, rapidly changing gradient of the refractive index in the surrounding liquid or gas makes objects seem to disappear and can be used for visibility cloaking. Light-matter interaction resonances, where light is confined at the nanoscale, can be extremely sensitive to changes in the refractive index of the surrounding media [8], even allowing single-molecule detection [9]. Plasmons, the collective oscillations of electrons in response to incident light, are a typical example. Researchers at Rice

  5. 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.

  6. 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.

  7. Refraction and absorption of microwaves in wood

    NASA Astrophysics Data System (ADS)

    Ziherl, Saša; Bajc, Jurij; Čepič, Mojca

    2013-03-01

    A demonstration experiment for physics students showing the dependence of the refractive index and absorption coefficient of wood on the direction of microwaves is presented. Wood and microwaves enable study of anisotropic properties, which are typically found in crystals. Wood is used as the persuasive representative of uniaxial anisotropic materials due to its visible structure and its consequent anisotropic properties. Wood can be cut in a general direction and wooden plates a few centimetres thick with well-defined fibre orientation are easily prepared. Microwaves are used because wood is transparent for microwaves and their centimetre-scale wavelength is comparable to the wood structure.

  8. The Alvarez and Lohmann refractive lenses revisited.

    PubMed

    Barbero, Sergio

    2009-05-25

    Alvarez and Lohmann lenses are variable focus optical devices based on lateral shifts of two lenses with cubic-type surfaces. I analyzed the optical performance of these types of lenses computing the first order optical properties (applying wavefront refraction and propagation) without the restriction of the thin lens approximation, and the spot diagram using a ray tracing algorithm. I proposed an analytic and numerical method to select the most optimum coefficients and the specific configuration of these lenses. The results show that Lohmann composite lens is slightly superior to Alvarez one because the overall thickness and optical aberrations are smaller.

  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. Critical review on refractive surgical lasers

    NASA Astrophysics Data System (ADS)

    Lin, J. T.

    1995-03-01

    The current status of refractive surgical lasers (including excimer and nonexcimer lasers) is reviewed with an emphasis on photorefractive keratectomy (PRK). The correlation of engineering parameters and the clinical requirements with optimal conditions are presented. The fundamentals of corneal reshaping with formulas for ablation profiles and the advantages of the multizone method are discussed. Updated information on the Mini-Excimer PRK laser system, with an emphasis on the scanning delivery device, is presented. PMMA ablation profiles performed by standard diaphragm and scanning modes are compared for surface ablation quality. Scanning mode ablation patterns for myopia, hyperopia, and regular and irregular astigmatism are presented.

  11. 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

  12. Silica nanorod-array films with very low refractive indices.

    PubMed

    Xi, J Q; Kim, Jong Kyu; Schubert, E F

    2005-07-01

    The refractive-index contrast is an important figure of merit for dielectric multilayer structures, optical resonators, and photonic crystals. This represents a strong driving force for novel materials that have refractive indices lower than those of conventional optically transparent materials. Silica nanorod-array dielectric films with unprecedented low refractive indices of 1.08 are demonstrated and shown to have viable optical properties including enhanced reflectivity of a single-pair distributed Bragg reflector.

  13. 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.

  14. Two different looks at Kepler’s refraction experiment

    NASA Astrophysics Data System (ADS)

    Grusche, Sascha; Wagner, Steffen

    2016-11-01

    Most refraction experiments are theory-laden and far from everyday experience. Accordingly, many students fail to apply the law of refraction to phenomena. To guide students from phenomena to theory, teachers can use a refraction experiment proposed by Kepler, where measurements are based on shadow images. For a different look at Kepler’s experiment, one can use the principle of reversibility to get equivalent results, but based on apparent depth. For this reversal, rays of light are reinterpreted as lines of sight, and vice versa. The principle allows students to relate refracted rays to shifted images, and applies to other optical phenomena.

  15. Relationship between visual field progression and baseline refraction in primary open-angle glaucoma

    PubMed Central

    Naito, Tomoko; Yoshikawa, Keiji; Mizoue, Shiro; Nanno, Mami; Kimura, Tairo; Suzumura, Hirotaka; Umeda, Yuzo; Shiraga, Fumio

    2016-01-01

    Purpose To analyze the relationship between visual field (VF) progression and baseline refraction in Japanese patients with primary open-angle glaucoma (POAG) including normal-tension glaucoma. Patients and methods In this retrospective study, the subjects were patients with POAG who had undergone VF tests at least ten times with a Humphrey Field Analyzer (Swedish interactive thresholding algorithm standard, Central 30-2 program). VF progression was defined as a significantly negative value of mean deviation (MD) slope at the final VF test. Multivariate logistic regression models were applied to detect an association between MD slope deterioration and baseline refraction. Results A total of 156 eyes of 156 patients were included in this analysis. Significant deterioration of MD slope was observed in 70 eyes of 70 patients (44.9%), whereas no significant deterioration was evident in 86 eyes of 86 patients (55.1%). The eyes with VF progression had significantly higher baseline refraction compared to those without apparent VF progression (−1.9±3.8 diopter [D] vs −3.5±3.4 D, P=0.0048) (mean ± standard deviation). When subject eyes were classified into four groups by the level of baseline refraction applying spherical equivalent (SE): no myopia (SE > −1D), mild myopia (−1D ≥ SE > −3D), moderate myopia (−3D ≥ SE > −6D), and severe myopia (−6D ≥ SE), the Cochran–Armitage trend analysis showed a decreasing trend in the proportion of MD slope deterioration with increasing severity of myopia (P=0.0002). The multivariate analysis revealed that baseline refraction (P=0.0108, odds ratio [OR]: 1.13, 95% confidence interval [CI]: 1.03–1.25) and intraocular pressure reduction rate (P=0.0150, OR: 0.97, 95% CI: 0.94–0.99) had a significant association with MD slope deterioration. Conclusion In the current analysis of Japanese patients with POAG, baseline refraction was a factor significantly associated with MD slope deterioration as well as intraocular

  16. 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.

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

    PubMed

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

    2015-03-15

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  20. Baseline peripheral refractive error and changes in axial refraction during one year in a young adult population

    PubMed Central

    Hartwig, Andreas; Charman, William Neil; Radhakrishnan, Hema

    2015-01-01

    Purpose To determine whether the initial characteristics of individual patterns of peripheral refraction relate to subsequent changes in refraction over a one-year period. Methods 54 myopic and emmetropic subjects (mean age: 24.9 ± 5.1 years; median 24 years) with normal vision were recruited and underwent conventional non-cycloplegic subjective refraction. Peripheral refraction was also measured at 5° intervals over the central 60° of horizontal visual field, together with axial length. After one year, measurements of subjective refraction and axial length were repeated on the 43 subjects who were still available for examination. Results In agreement with earlier studies, higher myopes tended to show greater relative peripheral hyperopia. There was, however, considerable inter-subject variation in the pattern of relative peripheral refractive error (RPRE) at any level of axial refraction. Across the group, mean one-year changes in axial refraction and axial length did not differ significantly from zero. There was no correlation between changes in these parameters for individual subjects and any characteristic of their RPRE. Conclusion No evidence was found to support the hypothesis that the pattern of RPRE is predictive of subsequent refractive change in this age group. PMID:26188389

  1. Nanofocusing Parabolic Refractive X-Ray Lenses

    SciTech Connect

    Schroer, C.G.; Kuhlmann, M.; Hunger, U.T.; Guenzler, T.F.; Kurapova, O.; Feste, S.; Lengeler, B.; Drakopoulos, M.; Somogyi, A.; Simionovici, A. S.; Snigirev, A.; Snigireva, I.

    2004-05-12

    Parabolic refractive x-ray lenses with short focal distance can generate intensive hard x-ray microbeams with lateral extensions in the 100nm range even at short distance from a synchrotron radiation source. We have fabricated planar parabolic lenses made of silicon that have a focal distance in the range of a few millimeters at hard x-ray energies. In a crossed geometry, two lenses were used to generate a microbeam with a lateral size of 330nm by 110nm at 25keV in a distance of 41.8m from the synchrotron radiation source. First microdiffraction and fluorescence microtomography experiments were carried out with these lenses. Using diamond as lens material, microbeams with lateral size down to 20nm and below are conceivable in the energy range from 10 to 100keV.

  2. 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.

  3. Refraction in Terms of the Deviation of the Light.

    ERIC Educational Resources Information Center

    Goldberg, Fred M.

    1985-01-01

    Discusses refraction in terms of the deviation of light. Points out that in physics courses where very little mathematics is used, it might be more suitable to describe refraction entirely in terms of the deviation, rather than by introducing Snell's law. (DH)

  4. 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…

  5. Anterior segment surgery IOLs, lasers, and refractive keratoplasty

    SciTech Connect

    Stark, W.J.; Terry, A.C.; Maumenee, A.E.

    1987-01-01

    The contributors to this text combine their expertise to make this book available on intraocular lenses, refractive corneal surgery, and the use of the YAG laser. Included is information on; IOL power calculations; the use of the YAG laser; retinal damage by short wavelength light; reviews of corneal refractive surgery; possibilities for the medical prevention of cataracts; and more.

  6. Helping Secondary School Students Develop a Conceptual Understanding of Refraction

    ERIC Educational Resources Information Center

    Ashmann, Scott; Anderson, Charles W.; Boeckman, Heather

    2016-01-01

    Using real-world examples, ray diagrams, and a cognitive apprenticeship cycle, this paper focuses on developing students' conceptual (not mathematical) understanding of refraction. Refraction can be a difficult concept for students to comprehend if they do not have well-designed opportunities to practice explaining situations where reflection and…

  7. Surface refractivity measurements at NASA spacecraft tracking sites

    NASA Technical Reports Server (NTRS)

    Schmid, P. E.

    1972-01-01

    High-accuracy spacecraft tracking requires tropospheric modeling which is generally scaled by either estimated or measured values of surface refractivity. This report summarizes the results of a worldwide surface-refractivity test conducted in 1968 in support of the Apollo program. The results are directly applicable to all NASA radio-tracking systems.

  8. 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.

  9. Cylindrical radiant energy direction device with refractive medium

    DOEpatents

    Winston, Roland

    1978-01-01

    A device is provided for directing radiant energy and includes a refractive element and a reflective boundary. The reflective boundary is so contoured that incident energy directed thereto by the refractive element is directed to the exit surface thereof or onto the surface of an energy absorber positioned at the exit surface.

  10. 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)

  11. 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)

  12. 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.

  13. Modification of the DSN radio frequency angular tropospheric refraction model

    NASA Technical Reports Server (NTRS)

    Berman, A. L.

    1977-01-01

    The previously derived DSN Radio Frequency Angular Tropospheric Refraction Model contained an assumption which was subsequently seen to be at a variance with the theoretical basis of angular refraction. The modification necessary to correct the model is minor in that the value of a constant is changed.

  14. 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…

  15. 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.

  16. Atmospheric Refractive Electromagnetic Wave Bending and Propagation Delay

    NASA Astrophysics Data System (ADS)

    Mangum, Jeffrey G.; Wallace, Patrick

    2015-01-01

    In this tutorial we summarize the physics and mathematics behind refractive electromagnetic wave bending and delay. Refractive bending and delay through the Earth's atmosphere at both radio/millimetric and optical/IR wavelengths are discussed, but with most emphasis on the former, and with Atacama Large Millimeter Array (ALMA) applications in mind. As modern astronomical measurements often require subarcsecond position accuracy, care is required when selecting refractive bending and delay algorithms. For the spherically-uniform model atmospheres generally used for all refractive bending and delay algorithms, positional accuracies lsim1'' are achievable when observing at zenith angles lsim75°. A number of computationally economical approximate methods for atmospheric refractive bending and delay calculation are presented, appropriate for astronomical observations under these conditions. For observations under more realistic atmospheric conditions, for zenith angles lsim75°, or when higher positional accuracy is required, more rigorous refractive bending and delay algorithms must be employed. For accurate calculation of the refractive bending, we recommend the Auer and Standish method, using numerical integration to ray-trace through a two-layer model atmosphere, with an atmospheric model determination of the atmospheric refractivity. For the delay calculation we recommend numerical integration through a model atmosphere.

  17. Software for teaching refraction of light with the semicircle

    NASA Astrophysics Data System (ADS)

    Mihas, Pavlos

    2016-11-01

    Software is presented for teaching elementary optics using a transparent semicircle. We demonstrate the use of the semicircle to investigate Snell’s lawand students can are presented with the difficulties involved in experiments. An Excel spreadsheet can show to students that small errors in positioning of the semicircle can result in a non-constant index of refraction. Students can study the effect of changing some of the parameters of placement of a semicircle on the accuracy of the experimental results. They can see from the analysis of data that much better results are obtained by doing regression analysis rather than by just taking the average value of the index of refraction. Measuring the critical angle also gives a method of calculating the index of refraction. Another way to measure the index of refraction is the use of the semicircle as a lens and from its focal length we can deduce the index of refraction.

  18. CHARMS: The Cryogenic, High-Accuracy Refraction Measuring System

    NASA Technical Reports Server (NTRS)

    Frey, Bradley; Leviton, Douglas

    2004-01-01

    The success of numerous upcoming NASA infrared (IR) missions will rely critically on accurate knowledge of the IR refractive indices of their constituent optical components at design operating temperatures. To satisfy the demand for such data, we have built a Cryogenic, High-Accuracy Refraction Measuring System (CHARMS), which, for typical 1R materials. can measure the index of refraction accurate to (+ or -) 5 x 10sup -3 . This versatile, one-of-a-kind facility can also measure refractive index over a wide range of wavelengths, from 0.105 um in the far-ultraviolet to 6 um in the IR, and over a wide range of temperatures, from 10 K to 100 degrees C, all with comparable accuracies. We first summarize the technical challenges we faced and engineering solutions we developed during the construction of CHARMS. Next we present our "first light," index of refraction data for fused silica and compare our data to previously published results.

  19. Ducting and Boundary Layer Refractivity Bias Correction in GPS Radio Occultation Soundings with MODIS over the Subtropical Eastern Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Xie, F.; Ao, C. O.; Adhikari, L.; Yu, X.

    2015-12-01

    Over the subtropical eastern Pacific, a large stratus cloud deck is often trapped below a strong inversion layer resulting from the combination of strong free tropospheric subsidence and the cool sea surface temperature underneath. The stable inversion leads to a sharp moisture decrease and a large negative refractivity gradient that often causes ducting right above the cloudy boundary layer (CBL). The presence of duct results in systematically negative biases in the GPS radio occultation (RO) refractivity (i.e., N-bias) inside the CBL due to a non-unique retrieval problem. An independent physical constraint is required to extract a unique and bias-free RO refractivity observation. In the overcast scenario, the inversion base temperature corresponds well to the cloud-top-temperature (CTT) of the stratus, which can be precisely measured from MODIS (Moderate Resolution Imaging Spectroradiometer) longwave infrared window channel. In this presentation, the MODIS CTT measurements are used as an independent constraint to correct the systematic biases in the near co-incident RO refractivity soundings from COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate). The sensitivity analysis on the reconstruction technique and the comparison of the reconstructed (bias-free) RO profiles with the radiosonde and ECMWF reanalysis will be presented. The synergy of GPS RO and MODIS cloud measurements provides model-independent observation of CBL thermodynamic structures that are crucial for understanding the boundary layer and low cloud processes in global weather and climate model simulations.

  20. Influence of uncorrected refractive error and unmet refractive error on visual impairment in a Brazilian population

    PubMed Central

    2014-01-01

    Background The World Health Organization (WHO) definitions of blindness and visual impairment are widely based on best-corrected visual acuity excluding uncorrected refractive errors (URE) as a visual impairment cause. Recently, URE was included as a cause of visual impairment, thus emphasizing the burden of visual impairment due to refractive error (RE) worldwide is substantially higher. The purpose of the present study is to determine the reversal of visual impairment and blindness in the population correcting RE and possible associations between RE and individual characteristics. Methods A cross-sectional study was conducted in nine counties of the western region of state of São Paulo, using systematic and random sampling of households between March 2004 and July 2005. Individuals aged more than 1 year old were included and were evaluated for demographic data, eye complaints, history, and eye exam, including no corrected visual acuity (NCVA), best corrected vision acuity (BCVA), automatic and manual refractive examination. The definition adopted for URE was applied to individuals with NCVA > 0.15 logMAR and BCVA ≤ 0.15 logMAR after refractive correction and unmet refractive error (UREN), individuals who had visual impairment or blindness (NCVA > 0.5 logMAR) and BCVA ≤ 0.5 logMAR after optical correction. Results A total of 70.2% of subjects had normal NCVA. URE was detected in 13.8%. Prevalence of 4.6% of optically reversible low vision and 1.8% of blindness reversible by optical correction were found. UREN was detected in 6.5% of individuals, more frequently observed in women over the age of 50 and in higher RE carriers. Visual impairment related to eye diseases is not reversible with spectacles. Using multivariate analysis, associations between URE and UREN with regard to sex, age and RE was observed. Conclusion RE is an important cause of reversible blindness and low vision in the Brazilian population. PMID:24965318

  1. The inverse problem of refraction travel times, part II: Quantifying refraction nonuniqueness using a three-layer model

    USGS Publications Warehouse

    Ivanov, J.; Miller, R.D.; Xia, J.; Steeples, D.

    2005-01-01

    This paper is the second of a set of two papers in which we study the inverse refraction problem. The first paper, "Types of Geophysical Nonuniqueness through Minimization," studies and classifies the types of nonuniqueness that exist when solving inverse problems depending on the participation of a priori information required to obtain reliable solutions of inverse geophysical problems. In view of the classification developed, in this paper we study the type of nonuniqueness associated with the inverse refraction problem. An approach for obtaining a realistic solution to the inverse refraction problem is offered in a third paper that is in preparation. The nonuniqueness of the inverse refraction problem is examined by using a simple three-layer model. Like many other inverse geophysical problems, the inverse refraction problem does not have a unique solution. Conventionally, nonuniqueness is considered to be a result of insufficient data and/or error in the data, for any fixed number of model parameters. This study illustrates that even for overdetermined and error free data, nonlinear inverse refraction problems exhibit exact-data nonuniqueness, which further complicates the problem of nonuniqueness. By evaluating the nonuniqueness of the inverse refraction problem, this paper targets the improvement of refraction inversion algorithms, and as a result, the achievement of more realistic solutions. The nonuniqueness of the inverse refraction problem is examined initially by using a simple three-layer model. The observations and conclusions of the three-layer model nonuniqueness study are used to evaluate the nonuniqueness of more complicated n-layer models and multi-parameter cell models such as in refraction tomography. For any fixed number of model parameters, the inverse refraction problem exhibits continuous ranges of exact-data nonuniqueness. Such an unfavorable type of nonuniqueness can be uniquely solved only by providing abundant a priori information

  2. The Northern Walker Lane Seismic Refraction Experiment

    NASA Astrophysics Data System (ADS)

    Louie, J. N.; Smith, S. B.; Thelen, W.; Scott, J. B.; Clark, M.

    2002-12-01

    We are developing a three-dimensional reference seismic velocity model for the western Great Basin region of Nevada and eastern California. The northern Walker Lane had not been characterized well by previous work. In May 2002 we collected a new crustal refraction profile from Battle Mountain, Nev. across western Nevada, the Reno area, Lake Tahoe, and the northern Sierra to Auburn, Calif. Mine blasts and earthquakes were recorded by 199 Texan instruments (loaned by the PASSCAL Instrument Center) extending across this more than 450-km-long transect. The seismic sources at the eastern end were mining blasts at Barrick's GoldStrike pit. We recorded additional blasts at the Florida Canyon and other mines between Lovelock and Battle Mountain, Nevada. The GoldStrike mine produced several ripple-fired blasts using 10,000-40,000 kg of ANFO each. First arrivals from the larger blasts are obvious to distances exceeding 250 km in the raw records. A M2.4 earthquake near Bridgeport, Calif. also produced pickable P-wave arrivals across at least half the transect, providing fan-shot data. We recorded only during working hours, and so missed an M4 earthquake that occurred at night. Events of M2 occurred during our recording to the west on the San Andreas fault near Pinnacles, Calif.; M3 events occurred near Portola and Mammoth Lakes, Calif. Arrivals from M5 events in the Mariana and Kuril Islands also appear in the records. Time-picks from these earthquakes may be possible after more work on synthetic-time modeling, data filtering, and display. We plan to record blasts at quarries in the western Sierra in future experiments, for a direct refraction reversal. We will compare our time picks against times generated from regional velocity models, to identify potential crustal and upper-mantle velocity anomalies. Such anomalies may be associated with the Battle Mountain heat-flow high, the northern Walker Lane belt, or the northern Sierran block.

  3. 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.

  4. Experimental evidence of super-resolution better than λ/105 with positive refraction

    NASA Astrophysics Data System (ADS)

    Miñano, Juan C.; Sánchez-Dehesa, José; González, Juan C.; Benítez, P.; Grabovičkić, D.; Carbonell, Jorge; Ahmadpanahi, H.

    2014-03-01

    Super-resolution (SR) systems surpassing the Abbe diffraction limit have been theoretically and experimentally demonstrated using a number of different approaches and technologies: using materials with a negative refractive index, utilizing optical super-oscillation, using a resonant metalens, etc. However, recently it has been proved theoretically that in the Maxwell fish-eye lens (MFE), a device made of positive refractive index materials, the same phenomenon takes place. Moreover, using a simpler device equivalent to the MFE called the spherical geodesic waveguide (SGW), an SR of up to λ/3000 was simulated in COMSOL. Until now, only one piece of experimental evidence of SR with positive refraction has been reported (up to λ/5) for an MFE prototype working at microwave frequencies. Here, experimental results are presented for an SGW prototype showing an SR of up to λ/105. The SGW prototype consists of two concentric metallic spheres with an air space in between and two coaxial ports acting as an emitter and a receiver. The prototype has been analyzed in the range 1 GHz to 1.3 GHz.

  5. Cattle egrets are less able to cope with light refraction than are other herons.

    PubMed

    Katzir; Strod; Schechtman; Hareli; Arad

    1999-03-01

    The majority of heron species (Aves, Ardeidae) forage on aquatic prey in shallow water. Prey detection, aiming and the beginning of the capture strikes are performed while the heron's eyes are above water. For most angles, as a result of air/water light refraction, the apparent image available to a heron is vertically displaced from the prey's real position. Herons must therefore correct for refraction. We tested the hypothesis that species that forage in aquatic habitats should be more able to correct for image disparity than those of terrestrial habitats. The ability of hand-reared herons of four species to capture stationary prey (fish) underwater (submerged) or in air (aerial) was tested. Three species (little egret Egretta garzetta, squacco heron Ardeola ralloides, and night heron Nycticorax nycticorax) normally forage in aquatic habitats while the fourth (cattle egret Bubulcus ibis) forages in terrestrial habitats. No individuals missed aerial prey. Success rates of little egrets and of squacco herons with submerged prey were high, while night herons became less successful with increased prey depth and/or distance. In cattle egrets, success rate was low and negatively correlated with prey depth. The observed interspecific differences may thus be related to (1) differential ability to correct for air/water light refraction and (2) the species' foraging behaviour. We suggest that cattle egrets are in the process of losing their ability to cope with submerged prey. Copyright 1999 The Association for the Study of Animal Behaviour.

  6. The Effect of Age, Gender, Refractive Status and Axial Length on the Measurements of Hertel Exophthalmometry

    PubMed Central

    Karti, Omer; Selver, Ozlem B; Karahan, Eyyup; Zengin, Mehmet O; Uyar, Murat

    2015-01-01

    Purpose : To evaluate the normal distribution of exophthalmometric values in Turkish adult population and the effect of age, gender, refractive status and axial length on globe position. Methods : One hundred and twenty-two males and 114 healthy females with age ranging from 18 to 87 years were included in the study. The study population was recruited from patients presenting to our institution for routine refractive examination. Hertel exophthalmometer was used to measure the degree of ocular protrusion. Effect of age, refractive error, interpupillary distance, and axial length on globe position was detected with linear regression analyses. Results : The mean Hertel exophthalmometric size was 15.7+2.6 mm (range; 11 to 21 mm). The mean value for males was 16.1±2.6 mm (range; 11 to 21 mm), and for females 15.5±2.6 mm (range; 11 to 20 mm). The mean distance between the lateral rims of the orbit was 102 + 5.1 mm (range; 88 to 111mm). The mean exophthalmometric values were not statistically different in males and females. Age and mean spherical equivalents were negatively correlated with exophthalmometric measurements. Axial length was positively correlated with exophthalmometric measurements. Conclusion : The exophthalmometric measurement of the eye is affected by the age, spherical equivalent and the axial length. Standard normative values of the Hertel exophthalmometric measurements should be reevaluated with larger samples. PMID:26089994

  7. Influence of Biometric Variables on Refractive Outcomes after Cataract Surgery in Angle-closure Glaucoma Patients

    PubMed Central

    Kim, Kyoung Nam; Lim, Hyung Bin; Lee, Jong Joo

    2016-01-01

    Purpose To evaluate the influence of biometric variables on refractive outcomes after cataract surgery in angle-closure glaucoma (ACG) patients. Methods In this case-control study, 42 ACG patients, 40 open-angle glaucoma (OAG) patients, and 35 controls without glaucoma who had undergone conventional cataract surgery were enrolled consecutively. Electronic medical records, including preoperative biometric variables (keratometric diopter, axial length, anterior chamber depth, and lens thickness), the refractive change (RC), and the absolute value of refractive change (ARC) were reviewed. Results In the control and OAG patients, the anterior chamber depth was negatively correlated with the ARC (r = -0.344, p = 0.043 and r = -0.431, p = 0.006, respectively), whereas there was no correlation in the ACG patients. Lens thickness was positively correlated with the RC, but not with the ARC, in the control and OAG groups (r = 0.391, p = 0.020 and r = 0.501, p = 0.001, respectively). In contrast, lens thickness in the ACG group was not correlated with the RC but was positively correlated with the ARC (r = 0.331, p = 0.032). Conclusions In contrast with the anterior chamber depth, preoperatively measured lens thickness may be a useful predictor of the direction of the RC after cataract surgery in control and OAG patients. However, in ACG patients, a thicker lens was correlated with a larger RC, regardless of the direction of the shift (hyperopic or myopic). PMID:27478355

  8. 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.

  9. Refractive Errors Affect the Vividness of Visual Mental Images

    PubMed Central

    Palermo, Liana; Nori, Raffaella; Piccardi, Laura; Zeri, Fabrizio; Babino, Antonio; Giusberti, Fiorella; Guariglia, Cecilia

    2013-01-01

    The hypothesis that visual perception and mental imagery are equivalent has never been explored in individuals with vision defects not preventing the visual perception of the world, such as refractive errors. Refractive error (i.e., myopia, hyperopia or astigmatism) is a condition where the refracting system of the eye fails to focus objects sharply on the retina. As a consequence refractive errors cause blurred vision. We subdivided 84 individuals according to their spherical equivalent refraction into Emmetropes (control individuals without refractive errors) and Ametropes (individuals with refractive errors). Participants performed a vividness task and completed a questionnaire that explored their cognitive style of thinking before their vision was checked by an ophthalmologist. Although results showed that Ametropes had less vivid mental images than Emmetropes this did not affect the development of their cognitive style of thinking; in fact, Ametropes were able to use both verbal and visual strategies to acquire and retrieve information. Present data are consistent with the hypothesis of equivalence between imagery and perception. PMID:23755186

  10. Cycloplegic refraction is the gold standard for epidemiological studies.

    PubMed

    Morgan, Ian G; Iribarren, Rafael; Fotouhi, Akbar; Grzybowski, Andrzej

    2015-09-01

    Many studies on children have shown that lack of cycloplegia is associated with slight overestimation of myopia and marked errors in estimates of the prevalence of emmetropia and hyperopia. Non-cycloplegic refraction is particularly problematic for studies of associations with risk factors. The consensus around the importance of cycloplegia in children left undefined at what age, if any, cycloplegia became unnecessary. It was often implicitly assumed that cycloplegia is not necessary beyond childhood or early adulthood, and thus, the protocol for the classical studies of refraction in older adults did not include cycloplegia. Now that population studies of refractive error are beginning to fill the gap between schoolchildren and older adults, whether cycloplegia is required for measuring refractive error in this age range, needs to be defined. Data from the Tehran Eye Study show that, without cycloplegia, there are errors in the estimation of myopia, emmetropia and hyperopia in the age range 20-50, just as in children. Similar results have been reported in an analysis of data from the Beaver Dam Offspring Eye Study. If the only important outcome measure of a particular study is the prevalence of myopia, then cycloplegia may not be crucial in some cases. But, without cycloplegia, measurements of other refractive categories as well as spherical equivalent are unreliable. In summary, the current evidence suggests that cycloplegic refraction should be considered as the gold standard for epidemiological studies of refraction, not only in children, but in adults up to the age of 50.

  11. 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).

  12. Refractive Error Evaluation in Eccentric Photorefracation

    NASA Astrophysics Data System (ADS)

    Baker, K.; Tan, B.; Shi, L.; Chen, Y.; Lewis, J. W. L.

    2007-11-01

    Eccentric photorefraction (EPR) is a technique to measure eye refractive errors (RE) particularly in non-cooperative children. A camera and a decentered light source are used to illuminate eyes and photograph the reflex. Recently the National Eye Institute VIP study examined 10 methods to screen the crucial children eye disorders including RE. The 3 EPR based devices were found to have lower detection sensitivities. The deficiency is inherent in the current optical designs and a lack of knowledge of parameters that influence RE analysis. The new EPR experimental design includes multi-eccentric-meridian illuminations, pupil finding algorithm, and feedback loop data acquisition. NIR is used to prevent chromatic aberration. A novel integrated intensity analysis is developed to control multiple intraocular scattering/reflection. The RE is calculated from the 21 normalized related intensities of the 2-D array illuminations. Using computer eye modeling and simulations, error analysis is performed for monochromatic aberrations and eye orientation. Experimental data comparison is obtained from a physical model eye.

  13. Climate Absolute Radiance and Refractivity Observatory (CLARREO)

    NASA Technical Reports Server (NTRS)

    Leckey, John P.

    2015-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a mission, led and developed by NASA, that will measure a variety of climate variables with an unprecedented accuracy to quantify and attribute climate change. CLARREO consists of three separate instruments: an infrared (IR) spectrometer, a reflected solar (RS) spectrometer, and a radio occultation (RO) instrument. The mission will contain orbiting radiometers with sufficient accuracy, including on orbit verification, to calibrate other space-based instrumentation, increasing their respective accuracy by as much as an order of magnitude. The IR spectrometer is a Fourier Transform spectrometer (FTS) working in the 5 to 50 microns wavelength region with a goal of 0.1 K (k = 3) accuracy. The FTS will achieve this accuracy using phase change cells to verify thermistor accuracy and heated halos to verify blackbody emissivity, both on orbit. The RS spectrometer will measure the reflectance of the atmosphere in the 0.32 to 2.3 microns wavelength region with an accuracy of 0.3% (k = 2). The status of the instrumentation packages and potential mission options will be presented.

  14. Variable thickness double-refracting plate

    DOEpatents

    Hadeishi, Tetsuo

    1976-01-01

    This invention provides an A.C., cyclic, current-controlled, phase retardation plate that uses a magnetic clamp to produce stress birefringence. It was developed for an Isotope-Zeeman Atomic Absorption Spectrometer that uses polarization modulation to effect automatic background correction in atomic absorption trace-element measurements. To this end, the phase retardation plate of the invention is a variable thickness, photoelastic, double-refracting plate that is alternately stressed and released by the magnetic clamp selectively to modulate specific components selected from the group consisting of circularly and plane polarized Zeeman components that are produced in a dc magnetic field so that they correspond respectively to Zeeman reference and transmission-probe absorption components. The polarization modulation changes the phase of these polarized Zeeman components, designated as .sigma. reference and .pi. absorption components, so that every half cycle the components change from a transmission mode to a mode in which the .pi. component is blocked and the .sigma. components are transmitted. Thus, the Zeeman absorption component, which corresponds in amplitude to the amount of the trace element to be measured in a sample, is alternately transmitted and blocked by a linear polarizer, while the circularly polarized reference components are continuously transmitted thereby. The result is a sinusoidally varying output light amplitude whose average corresponds to the amount of the trace element present in the sample.

  15. Analysis of critically refracted longitudinal waves

    NASA Astrophysics Data System (ADS)

    Pei, Ning; Bond, Leonard J.

    2015-03-01

    Fabrication processes, such as, welding, forging, and rolling can induce residual stresses in metals that will impact product performance and phenomena such as cracking and corrosion. To better manage residual stress tools are needed to map their distribution. The critically refracted ultrasonic longitudinal (LCR) wave is one such approach that has been used for residual stress characterization. It has been shown to be sensitive to stress and less sensitive to the effects of the texture of the material. Although the LCR wave is increasingly widely applied, the factors that influence the formation of the LCR beam are seldom discussed. This paper reports a numerical model used to investigate the transducers' parameters that can contribute to the directionality of the LCR wave and hence enable performance optimization when used for industrial applications. An orthogonal test method is used to study the transducer parameters which influence the LCR wave beams. This method provides a design tool that can be used to study and optimize multiple parameter experiments and it can identify which parameter or parameters are of most significance. The simulation of the sound field in a 2-D "water-steel" model is obtained using a Spatial Fourier Analysis method. The effects of incident angle, standoff, the aperture and the center frequency of the transducer were studied. Results show that the aperture of the transducer, the center frequency and the incident angle are the most important factors in controlling the directivity of the resulting LCR wave fields.

  16. Failure Analysis of Sapphire Refractive Secondary Concentrators

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Quinn, George D.

    2009-01-01

    Failure analysis was performed on two sapphire, refractive secondary concentrators (RSC) that failed during elevated temperature testing. Both concentrators failed from machining/handling damage on the lens face. The first concentrator, which failed during testing to 1300 C, exhibited a large r-plane twin extending from the lens through much of the cone. The second concentrator, which was an attempt to reduce temperature gradients and failed during testing to 649 C, exhibited a few small twins on the lens face. The twins were not located at the origin, but represent another mode of failure that needs to be considered in the design of sapphire components. In order to estimate the fracture stress from fractographic evidence, branching constants were measured on sapphire strength specimens. The fractographic analysis indicated radial tensile stresses of 44 to 65 MPa on the lens faces near the origins. Finite element analysis indicated similar stresses for the first RSC, but lower stresses for the second RSC. Better machining and handling might have prevented the fractures, however, temperature gradients and resultant thermal stresses need to be reduced to prevent twinning.

  17. Analysis of critically refracted longitudinal waves

    SciTech Connect

    Pei, Ning Bond, Leonard J.

    2015-03-31

    Fabrication processes, such as, welding, forging, and rolling can induce residual stresses in metals that will impact product performance and phenomena such as cracking and corrosion. To better manage residual stress tools are needed to map their distribution. The critically refracted ultrasonic longitudinal (LCR) wave is one such approach that has been used for residual stress characterization. It has been shown to be sensitive to stress and less sensitive to the effects of the texture of the material. Although the LCR wave is increasingly widely applied, the factors that influence the formation of the LCR beam are seldom discussed. This paper reports a numerical model used to investigate the transducers' parameters that can contribute to the directionality of the LCR wave and hence enable performance optimization when used for industrial applications. An orthogonal test method is used to study the transducer parameters which influence the LCR wave beams. This method provides a design tool that can be used to study and optimize multiple parameter experiments and it can identify which parameter or parameters are of most significance. The simulation of the sound field in a 2-D 'water-steel' model is obtained using a Spatial Fourier Analysis method. The effects of incident angle, standoff, the aperture and the center frequency of the transducer were studied. Results show that the aperture of the transducer, the center frequency and the incident angle are the most important factors in controlling the directivity of the resulting LCR wave fields.

  18. 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.

  19. Correlation between Hertel exophthalmometric value and refraction in young Cameroonian adults aged 20 to 40 years

    PubMed Central

    Dohvoma, Viola A; Epée, Emilienne; Ebana Mvogo, Stève R; Lietcheu, N Sandra; Ebana Mvogo, Côme

    2016-01-01

    Purpose To study the relationship between exophthalmometric value (EV) and refractive error in Cameroonian young adults. Patients and methods A prospective descriptive study was carried out in the ophthalmic unit of the Yaoundé Central Hospital from March to May 2015. Consenting patients aged 20–40 years with no intraocular pathology who were seen for refractive errors were included. Ocular protrusion was measured using the Hertel exophthalmometer. Automatic refraction was done following cycloplegia with cyclopentolate and tropicamide. Results A total of 200 patients were included (68% females and 32% males). The mean age was 27.2±6 years. Hyperopia was the most common refractive error (51%), followed by hyperopic astigmatism (19.3%). EV varied between 9 mm and 23 mm, with a mean of 14.8±2.5 mm in the right eye and 15.0±2.5 mm in the left eye. The mean EVs were 17.10±2.80 mm in myopia, 14.24±1.92 mm in hyperopia, 16.72±2.58 mm in myopic astigmatism, 14.07±2.19 mm in hyperopic astigmatism, and 14.77±2.40 mm in mixed astigmatism. The spherical value had a negative correlation with EV (P=0.0000). Conclusion The mean EV of this Cameroonian population is smaller than that of other populations and is consistent with the known characteristic hyperopic status of the population. A study on a larger sample will determine the normative data of absolute and relative EV in our setting. PMID:27536057

  20. 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.

  1. Reflection and refraction of waves in oscillatory media

    NASA Astrophysics Data System (ADS)

    Gu, Guo-Feng; Lü, Yao-Ping; Tang, Guo-Ning

    2010-05-01

    This paper uses the two-dimensional Brusselator model to study reflection and refraction of chemical waves. It presents some boundary conditions of chemical waves, with which occurence of observed phenomena at interface as refraction and reflection of chemical waves can be interpreted. Moreover, the angle of reflection may be calculated by using the boundary conditions. It finds that reflection and refraction of chemical waves can occur simultaneously even if plane wave goes from a medium with higher speed to a medium with lower speed, provided the incident angle is larger than the critical angle.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Studies of atmospheric refraction effects on laser data

    NASA Technical Reports Server (NTRS)

    Dunn, P. J.; Pearce, W. A.; Johnson, T. S.

    1982-01-01

    The refraction effect from three perspectives was considered. An analysis of the axioms on which the accepted correction algorithms were based was the first priority. The integrity of the meteorological measurements on which the correction model is based was also considered and a large quantity of laser observations was processed in an effort to detect any serious anomalies in them. The effect of refraction errors on geodetic parameters estimated from laser data using the most recent analysis procedures was the focus of the third element of study. The results concentrate on refraction errors which were found to be critical in the eventual use of the data for measurements of crustal dynamics.

  7. Using neural nets to measure ocular refractive errors: a proposal

    NASA Astrophysics Data System (ADS)

    Netto, Antonio V.; Ferreira de Oliveira, Maria C.

    2002-12-01

    We propose the development of a functional system for diagnosing and measuring ocular refractive errors in the human eye (astigmatism, hypermetropia and myopia) by automatically analyzing images of the human ocular globe acquired with the Hartmann-Schack (HS) technique. HS images are to be input into a system capable of recognizing the presence of a refractive error and outputting a measure of such an error. The system should pre-process and image supplied by the acquisition technique and then use artificial neural networks combined with fuzzy logic to extract the necessary information and output an automated diagnosis of the refractive errors that may be present in the ocular globe under exam.

  8. 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.

  9. Comment on 'Reply to comment on "Perfect imaging without negative refraction"'

    NASA Astrophysics Data System (ADS)

    Kinsler, Paul; Favaro, Alberto

    2011-02-01

    Whether or not perfect imaging is obtained in the mirrored version of Maxwell's fisheye lens is debated in the comment/reply sequence (Blaikie 2010 New J. Phys. 12 058001; Leonhardt 2010 New J. Phys. 12 058002) discussing Leonhardt's original paper (Leonhardt 2009 New J. Phys. 11 093040). Here, we show that causal solutions can be obtained without the need for an 'active localized drain', contrary to the claims made by Leonhardt (2010 New J. Phys. 12 058002).

  10. Making waves round a structured cloak: lattices, negative refraction and fringes.

    PubMed

    Colquitt, D J; Jones, I S; Movchan, N V; Movchan, A B; Brun, M; McPhedran, R C

    2013-09-01

    Using the framework of transformation optics, this paper presents a detailed analysis of a non-singular square cloak for acoustic, out-of-plane shear elastic and electromagnetic waves. Analysis of wave propagation through the cloak is presented and accompanied by numerical illustrations. The efficacy of the regularized cloak is demonstrated and an objective numerical measure of the quality of the cloaking effect is provided. It is demonstrated that the cloaking effect persists over a wide range of frequencies. As a demonstration of the effectiveness of the regularized cloak, a Young's double slit experiment is presented. The stability of the interference pattern is examined when a cloaked and uncloaked obstacle are successively placed in front of one of the apertures. This novel link with a well-known quantum mechanical experiment provides an additional method through which the quality of cloaks may be examined. In the second half of the paper, it is shown that an approximate cloak may be constructed using a discrete lattice structure. The efficiency of the approximate lattice cloak is analysed and a series of illustrative simulations presented. It is demonstrated that effective cloaking may be obtained by using a relatively simple lattice structure, particularly, in the low-frequency regime.

  11. Making waves round a structured cloak: lattices, negative refraction and fringes

    PubMed Central

    Colquitt, D. J.; Jones, I. S.; Movchan, N. V.; Movchan, A. B.; Brun, M.; McPhedran, R. C.

    2013-01-01

    Using the framework of transformation optics, this paper presents a detailed analysis of a non-singular square cloak for acoustic, out-of-plane shear elastic and electromagnetic waves. Analysis of wave propagation through the cloak is presented and accompanied by numerical illustrations. The efficacy of the regularized cloak is demonstrated and an objective numerical measure of the quality of the cloaking effect is provided. It is demonstrated that the cloaking effect persists over a wide range of frequencies. As a demonstration of the effectiveness of the regularized cloak, a Young's double slit experiment is presented. The stability of the interference pattern is examined when a cloaked and uncloaked obstacle are successively placed in front of one of the apertures. This novel link with a well-known quantum mechanical experiment provides an additional method through which the quality of cloaks may be examined. In the second half of the paper, it is shown that an approximate cloak may be constructed using a discrete lattice structure. The efficiency of the approximate lattice cloak is analysed and a series of illustrative simulations presented. It is demonstrated that effective cloaking may be obtained by using a relatively simple lattice structure, particularly, in the low-frequency regime. PMID:24062625

  12. Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking

    PubMed Central

    Poo, Yin; He, Cheng; Xiao, Chao; Lu, Ming-Hui; Wu, Rui-Xin; Chen, Yan-Feng

    2016-01-01

    One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking. PMID:27387438

  13. Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking.

    PubMed

    Poo, Yin; He, Cheng; Xiao, Chao; Lu, Ming-Hui; Wu, Rui-Xin; Chen, Yan-Feng

    2016-07-08

    One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking.

  14. Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking

    NASA Astrophysics Data System (ADS)

    Poo, Yin; He, Cheng; Xiao, Chao; Lu, Ming-Hui; Wu, Rui-Xin; Chen, Yan-Feng

    2016-07-01

    One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking.

  15. Refractive cylinder outcomes after calculating toric intraocular lens cylinder power using total corneal refractive power

    PubMed Central

    Davison, James A; Potvin, Richard

    2015-01-01

    Purpose To determine whether the total corneal refractive power (TCRP) value, which is based on measurement of both anterior and posterior corneal astigmatism, is effective for toric intraocular lens (IOL) calculation with AcrySof® Toric IOLs. Patients and methods A consecutive series of cataract surgery cases with AcrySof toric IOL implantation was studied retrospectively. The IOLMaster® was used for calculation of IOL sphere, the Pentacam® TCRP 3.0 mm apex/ring value was used as the keratometry input to the AcrySof Toric IOL Calculator and the VERION™ Digital Marker for surgical orientation. The keratometry readings from the VERION reference unit were recorded but not used in the actual calculation. Vector differences between expected and actual residual refractive cylinder were calculated and compared to simulated vector errors using the collected VERION keratometry data. Results In total, 83 eyes of 56 patients were analyzed. Residual refractive cylinder was 0.25 D or lower in 58% of eyes and 0.5 D or lower in 80% of eyes. The TCRP-based calculation resulted in a statistically significantly lower vector error (P<0.01) and significantly more eyes with a vector error ≤0.5 D relative to the VERION-based calculation (P=0.02). The TCRP and VERION keratometry readings suggested a different IOL toric power in 53/83 eyes. In these 53 eyes the TCRP vector error was lower in 28 cases, the VERION error was lower in five cases, and the error was equal in 20 cases. When the anterior cornea had with-the-rule astigmatism, the VERION was more likely to suggest a higher toric power and when the anterior cornea had against-the-rule astigmatism, the VERION was less likely to suggest a higher toric power. Conclusion Using the TCRP keratometry measurement in the AcrySof toric calculator may improve overall postoperative refractive results. Consideration of measured posterior corneal astigmatism, rather than a population-averaged value, appears advantageous. PMID:26316693

  16. 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.

  17. Computational imaging using lightweight diffractive-refractive optics.

    PubMed

    Peng, Yifan; Fu, Qiang; Amata, Hadi; Su, Shuochen; Heide, Felix; Heidrich, Wolfgang

    2015-11-30

    Diffractive optical elements (DOE) show great promise for imaging optics that are thinner and more lightweight than conventional refractive lenses while preserving their light efficiency. Unfortunately, severe spectral dispersion currently limits the use of DOEs in consumer-level lens design. In this article, we jointly design lightweight diffractive-refractive optics and post-processing algorithms to enable imaging under white light illumination. Using the Fresnel lens as a general platform, we show three phase-plate designs, including a super-thin stacked plate design, a diffractive-refractive-hybrid lens, and a phase coded-aperture lens. Combined with cross-channel deconvolution algorithm, both spherical and chromatic aberrations are corrected. Experimental results indicate that using our computational imaging approach, diffractive-refractive optics is an alternative candidate to build light efficient and thin optics for white light imaging.

  18. 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.

  19. 2D seismic residual statics derived from refraction interferometry

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Zhang, Jie

    2016-07-01

    Refraction traveltimes have long been applied for deriving long-wavelength statics solutions. These traveltimes are also applied for the derivation of residual statics, but they must be sufficiently accurate at short wavelengths. In this study, we present a seismic residual statics method that applies interferometric theory to produce four stacked virtual refraction gathers with a significantly improved signal-to-noise ratio. These gathers are composed of forward and backward virtual refraction gathers for receivers and shots. By picking the first arrivals on these four gathers followed by the application of a set of refraction equations, reliable residual statics solutions can be derived. This approach can help deal with noisy data and also avoid using traveltime picks from shot gathers. We demonstrate the approach by applying it to synthetic data as well as real data.

  20. 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)

  1. 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)

  2. An Analogue Model for Teaching Reflection and Refraction of Waves.

    ERIC Educational Resources Information Center

    Bates, Harry E.

    1980-01-01

    Describes a concrete model for teaching the concepts of reflection and refraction without the use of formal mathematics. The model has been tested in five sections of a physics course for nonscience majors at Towson State University, Baltimore, Maryland. (HM)

  3. Asronomical refraction: Computational methods for all zenith angles

    NASA Technical Reports Server (NTRS)

    Auer, L. H.; Standish, E. M.

    2000-01-01

    It is shown that the problem of computing astronomical refraction for any value of the zenith angle may be reduced to a simple, nonsingular, numerical quadrature when the proper choice is made for the independent variable of integration.

  4. 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.

  5. A study on refractive errors among school children in Kolkata.

    PubMed

    Das, Angshuman; Dutta, Himadri; Bhaduri, Gautam; De Sarkar, Ajay; Sarkar, Krishnendu; Bannerjee, Manas

    2007-04-01

    Childhood visual impairment due to refractive errors is a significant problem in school children and has a considerable impact on public health. To assess the magnitude of the problem the present study was undertaken among the school children aged 5 to 10 years in Kolkata. Detailed ophthalmological examination was carried out in the schools as well as in the Regional Institute of Ophthalmology, Kolkata. Among 2317 students examined, 582 (25.11%) were suffering from refractive errors, myopia being the commonest (n = 325; 14.02%). Astigmatism affected 91 children (3.93%). There is an increase of prevalence of refractive errors with increase of age, but it is not statistically significant (p > 0.05). There is also no significant difference of refractive errors between boys and girls. PMID:17822183

  6. Helping secondary school students develop a conceptual understanding of refraction

    NASA Astrophysics Data System (ADS)

    Ashmann, Scott; Anderson, Charles W.; Boeckman, Heather

    2016-07-01

    Using real-world examples, ray diagrams, and a cognitive apprenticeship cycle, this paper focuses on developing students’ conceptual (not mathematical) understanding of refraction. Refraction can be a difficult concept for students to comprehend if they do not have well-designed opportunities to practice explaining situations where reflection and refraction occur. The use of ray diagrams can be useful in (a) the teacher modelling a correct explanation to a situation where refraction occurs and (b) for students to create as they practice other examples. This paper includes eight examples of increasing complexity that use a cognitive apprenticeship cycle approach to scaffold student learning. The first examples (rock fish, floating penny) are shown and a solution is modeled using a ray diagram. Three more examples (bent pencil, dropping an item in water, sunrise/sunset) are presented for students to practice, with each becoming more sophisticated. Three assessment exercises are then provided (two dots, three coins, broken tube).

  7. Ectasia risk factors in refractive surgery

    PubMed Central

    Santhiago, Marcony R; Giacomin, Natalia T; Smadja, David; Bechara, Samir J

    2016-01-01

    This review outlines risk factors of post-laser in situ keratomileusis (LASIK) ectasia that can be detected preoperatively and presents a new metric to be considered in the detection of ectasia risk. Relevant factors in refractive surgery screening include the analysis of intrinsic biomechanical properties (information obtained from corneal topography/tomography and patient’s age), as well as the analysis of alterable biomechanical properties (information obtained from the amount of tissue altered by surgery and the remaining load-bearing tissue). Corneal topography patterns of placido disk seem to play a pivotal role as a surrogate of corneal strength, and abnormal corneal topography remains to be the most important identifiable risk factor for ectasia. Information derived from tomography, such as pachymetric and epithelial maps as well as computational strategies, to help in the detection of keratoconus is additional and relevant. High percentage of tissue altered (PTA) is the most robust risk factor for ectasia after LASIK in patients with normal preoperative corneal topography. Compared to specific residual stromal bed (RSB) or central corneal thickness values, percentage of tissue altered likely provides a more individualized measure of biomechanical alteration because it considers the relationship between thickness, tissue altered through ablation and flap creation, and ultimate RSB thickness. Other recognized risk factors include low RSB, thin cornea, and high myopia. Age is also a very important risk factor and still remains as one of the most overlooked ones. A comprehensive screening approach with the Ectasia Risk Score System, which evaluates multiple risk factors simultaneously, is also a helpful tool in the screening strategy. PMID:27143849

  8. Light refraction in the Swiss-cheese model

    NASA Astrophysics Data System (ADS)

    Csapó, Adelinda; Bene, Gyula

    2012-08-01

    We investigate light propagation in the Swiss-cheese model. On both sides of Swiss-cheese sphere surfaces, observers resting in the flat Friedmann-Robertson-Walker (FRW) space and the Schwarzschild space respectively, see the same light ray enclosing different angles with the normal. We examine light refraction at each crossing of the boundary surfaces, showing that the angle of refraction is larger than the angle of incidence for both directions of the light.

  9. Recent developments in refractive concentrators for space photovoltaic power systems

    NASA Technical Reports Server (NTRS)

    Piszczor, Michael F.; Oneill, Mark J.

    1993-01-01

    Since SPRAT 11, significant progress has been made in the development of refractive concentrator elements and components designed specifically for space applications. The status of the mini-dome Fresnel lens concentrator array is discussed and then the results of work recently completed in the area of prismatic cell covers for concentrator systems are summarized. This is followed by a brief discussion of some work just starting in the area of line-focus refractive concentrators for space.

  10. Apparatus and method to compensate for refraction of radiation

    DOEpatents

    Allen, Gary R.; Moskowitz, Philip E.

    1990-01-01

    An apparatus to compensate for refraction of radiation passing through a curved wall of an article is provided. The apparatus of a preferred embodiment is particularly advantageous for use in arc tube discharge diagnostics. The apparatus of the preferred embodiment includes means for pre-refracting radiation on a predetermined path by an amount equal and inverse to refraction which occurs when radiation passes through a first wall of the arc tube such that, when the radiation passes through the first wall of the arc tube and into the cavity thereof, the radiation passes through the cavity approximately on the predetermined path; means for releasably holding the article such that the radiation passes through the cavity thereof; and means for post-refracting radiation emerging from a point of the arc tube opposite its point of entry by an amount equal and inverse to refraction which occurs when radiation emerges from the arc tube. In one embodiment the means for pre-refracting radiation includes a first half tube comprising a longitudinally bisected tube obtained from a tube which is approximately identical to the arc tube's cylindrical portion and a first cylindrical lens, the first half tube being mounted with its concave side facing the radiation source and the first cylindrical lens being mounted between the first half tube and the arc tube and the means for post-refracting radiation includes a second half tube comprising a longitudinally bisected tube obtained from a tube which is approximately identical to the arc tube's cylindrical portion and a second cylindrical lens, the second half tube being mounted with its convex side facing the radiation source and the second cylindrical lens being mounted between the arc tube and the second half tube. Methods to compensate for refraction of radiation passing into and out of an arc tube is also provided.

  11. Apparatus and method to compensate for refraction of radiation

    DOEpatents

    Allen, G.R.; Moskowitz, P.E.

    1990-03-27

    An apparatus to compensate for refraction of radiation passing through a curved wall of an article is provided. The apparatus of a preferred embodiment is particularly advantageous for use in arc tube discharge diagnostics. The apparatus of the preferred embodiment includes means for pre-refracting radiation on a predetermined path by an amount equal and inverse to refraction which occurs when radiation passes through a first wall of the arc tube such that, when the radiation passes through the first wall of the arc tube and into the cavity thereof, the radiation passes through the cavity approximately on the predetermined path; means for releasably holding the article such that the radiation passes through the cavity thereof; and means for post-refracting radiation emerging from a point of the arc tube opposite its point of entry by an amount equal and inverse to refraction which occurs when radiation emerges from the arc tube. In one embodiment the means for pre-refracting radiation includes a first half tube comprising a longitudinally bisected tube obtained from a tube which is approximately identical to the arc tube's cylindrical portion and a first cylindrical lens, the first half tube being mounted with its concave side facing the radiation source and the first cylindrical lens being mounted between the first half tube and the arc tube and the means for post-refracting radiation includes a second half tube comprising a longitudinally bisected tube obtained from a tube which is approximately identical to the arc tube's cylindrical portion and a second cylindrical lens, the second half tube being mounted with its convex side facing the radiation source and the second cylindrical lens being mounted between the arc tube and the second half tube. Methods to compensate for refraction of radiation passing into and out of an arc tube is also provided. 4 figs.

  12. Effective refractive indices of three-phase optical coatings

    NASA Astrophysics Data System (ADS)

    Ma, Yushieh; Varadan, Vijay K.; Varadan, Vasundara V.

    1991-11-01

    To obtain the effective refractive indices of three-phase coating materials, in which multiple scattering can also occur between the two different discrete phases, a multiple scattering formalism for two-phase systems is modified to include the third phase. Numerical results for different refractive indices of various arrangements are presented for a paint coating in which some of the TiO2 pigment particles are replaced by microbubbles.

  13. 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.

  14. Seismic refraction survey of the ANS preferred site

    SciTech Connect

    Davis, R.K. ); Hopkins, R.A. ); Doll, W.E. )

    1992-02-01

    Between September 19, 1991 and October 8, 1991 personnel from Martin Marietta Energy Systems, Inc. (Energy Systems), Automated Sciences Group, Inc., and Marrich, Inc. performed a seismic refraction survey at the Advanced Neutron Source (ANS) preferred site. The purpose of this survey was to provide estimates of top-of-rock topography, based on seismic velocities, and to delineate variations in rock and soil velocities. Forty-four seismic refraction spreads were shot to determine top-of-rock depths at 42 locations. Nine of the seismic spreads were shot with long offsets to provide 216 top-of-rock depths for 4 seismic refraction profiles. The refraction spread locations were based on the grid for the ANS Phase I drilling program. Interpretation of the seismic refraction data supports the assumption that the top-of-rock surface generally follows the local topography. The shallow top-of-rock interface interpreted from the seismic refraction data is also supported by limited drill information at the site. Some zones of anomalous data are present that could be the result of locally variable weathering, a localized variation in shale content, or depth to top-of-rock greater than the site norm.

  15. Low-repetition rate femtosecond laser writing of optical waveguides in KTP crystals: analysis of anisotropic refractive index changes.

    PubMed

    Butt, Muhammad Ali; Nguyen, Huu-Dat; Ródenas, Airán; Romero, Carolina; Moreno, Pablo; Vázquez de Aldana, Javier R; Aguiló, Magdalena; Solé, Rosa Maria; Pujol, Maria Cinta; Díaz, Francesc

    2015-06-15

    We report on the direct low-repetition rate femtosecond pulse laser microfabrication of optical waveguides in KTP crystals and the characterization of refractive index changes after the thermal annealing of the sample, with the focus on studying the potential for direct laser fabricating Mach-Zehnder optical modulators. We have fabricated square cladding waveguides by means of stacking damage tracks, and found that the refractive index decrease is large for vertically polarized light (c-axis; TM polarized) but rather weak for horizontally polarized light (a-axis; TE polarized), this leading to good near-infrared light confinement for TM modes but poor for TE modes. However, after performing a sample thermal annealing we have found that the thermal process enables a refractive index increment of around 1.5x10(-3) for TE polarized light, while maintaining the negative index change of around -1x10(-2) for TM polarized light. In order to evaluate the local refractive index changes we have followed a multistep procedure: We have first characterized the waveguide cross-sections by means of Raman micro-mapping to access the lattice micro-modifications and their spatial extent. Secondly we have modeled the waveguides following the modified region sizes obtained by micro-Raman with finite element method software to obtain a best match between the experimental propagation modes and the simulated ones. Furthermore we also report the fabrication of Mach-Zehnder structures and the evaluation of propagation losses. PMID:26193514

  16. Low-repetition rate femtosecond laser writing of optical waveguides in KTP crystals: analysis of anisotropic refractive index changes.

    PubMed

    Butt, Muhammad Ali; Nguyen, Huu-Dat; Ródenas, Airán; Romero, Carolina; Moreno, Pablo; Vázquez de Aldana, Javier R; Aguiló, Magdalena; Solé, Rosa Maria; Pujol, Maria Cinta; Díaz, Francesc

    2015-06-15

    We report on the direct low-repetition rate femtosecond pulse laser microfabrication of optical waveguides in KTP crystals and the characterization of refractive index changes after the thermal annealing of the sample, with the focus on studying the potential for direct laser fabricating Mach-Zehnder optical modulators. We have fabricated square cladding waveguides by means of stacking damage tracks, and found that the refractive index decrease is large for vertically polarized light (c-axis; TM polarized) but rather weak for horizontally polarized light (a-axis; TE polarized), this leading to good near-infrared light confinement for TM modes but poor for TE modes. However, after performing a sample thermal annealing we have found that the thermal process enables a refractive index increment of around 1.5x10(-3) for TE polarized light, while maintaining the negative index change of around -1x10(-2) for TM polarized light. In order to evaluate the local refractive index changes we have followed a multistep procedure: We have first characterized the waveguide cross-sections by means of Raman micro-mapping to access the lattice micro-modifications and their spatial extent. Secondly we have modeled the waveguides following the modified region sizes obtained by micro-Raman with finite element method software to obtain a best match between the experimental propagation modes and the simulated ones. Furthermore we also report the fabrication of Mach-Zehnder structures and the evaluation of propagation losses.

  17. Assembly and alignment of infrared refractive system

    NASA Astrophysics Data System (ADS)

    Yang, Lin; Lin, Jian-chun; Wang, Ya-jing; Chen, Fan-sheng

    2013-09-01

    Optical systems for scientific instrumentation frequently include lens or mirrors with critical mechanical requirements. Position issues of those components are inextricably bound to the efficiency of the instrument. The position referring to the lens system mainly means spacer and rotation of all elements concerned. Instrument could not be completed without the accuracy assembly even the previous design was top one. The alignment of infrared optical system always is a tough thing due to the IR material being opaque to visible light which hardly effect on the imaging ability of the system. In this paper a large-aperture IR refractive system was described in details and the alignment of this system was presented. The brief work describes the assembly and integration of the camera barrel in lab. First of all, all the mechanical elements must be manufactured with high accuracy requirements to meet alignment tolerances and minimum errors mostly could be ignored. The rotations relative to the optical axis were hardy restricted by the space between barrel and cells. The lens vertex displacements were determined through high accuracy titanium alloy spacer. So the actual shape data of the optical lenses were obtained by coordinate measuring machining (CMM) to calculate the real space between lenses after alignment1 done. All the measured results were critical for instruction of the practical assemble. Based on the properties and tolerances of the system, the camera barrel includes sets of six lenses with their respective supports and cells which are composed of two parts: the flied lens group and the relay lenses group. The first one was aligned by the geometry centering used CMM. And the relay lenses were integrated one by one after centered individually with a classical centering instrument. Then the two separate components were assembled under the monitor of the CMM with micron precision. Three parameters on the opti-mechanical elements which include decenter, tilt and

  18. Wave propagation in negative index materials

    NASA Astrophysics Data System (ADS)

    Aylo, Rola

    Properties of electromagnetic propagation in materials with negative permittivities and permeabilities were first studied in 1968. In such metamaterials, the electric field vector, the magnetic field vector, and the propagation vector form a left hand triad, thus the name left hand materials. Research in this area was practically non-existent, until about 10 years ago, a composite material consisting of periodic metallic rods and split-ring resonators showed left-handed properties. Because the dimension of the constituents of the metamaterial are small compared to the operating wavelength, it is possible to describe the electromagnetic properties of the composite using the concept of effective permittivity and permeability. In this dissertation, the basic properties of electromagnetic propagation through homogenous left hand materials are first studied. Many of the basic properties of left hand materials are in contrast to those in right hand materials, viz., negative refraction, perfect lensing, and the inverse Doppler effect. Dispersion relations are used to study wave propagation in negative index materials. For the first time to the best of our knowledge, we show that a reduced dispersion relation, obtained from the frequency dependence of the propagation constant by neglecting a linear frequency dependent term, obeys causality. Causality of the propagation constant enables us to use a novel and simple operator formalism approach to derive the underlying partial differential equations for baseband and envelope wave propagation. Various tools for understanding and characterizing left-handed materials are thereafter presented. The transfer matrix method is used to analyze periodic and random structures composed of positive and negative index materials. By random structures we mean randomness in layer position, index of refraction, and thickness. As an application of alternating periodic negative index and positive index structures, we propose a novel sensor using

  19. Global cost of correcting vision impairment from uncorrected refractive error

    PubMed Central

    Fricke, TR; Wilson, DA; Schlenther, G; Naidoo, KS; Resnikoff, S; Frick, KD

    2012-01-01

    Abstract Objective To estimate the global cost of establishing and operating the educational and refractive care facilities required to provide care to all individuals who currently have vision impairment resulting from uncorrected refractive error (URE). Methods The global cost of correcting URE was estimated using data on the population, the prevalence of URE and the number of existing refractive care practitioners in individual countries, the cost of establishing and operating educational programmes for practitioners and the cost of establishing and operating refractive care facilities. The assumptions made ensured that costs were not underestimated and an upper limit to the costs was derived using the most expensive extreme for each assumption. Findings There were an estimated 158 million cases of distance vision impairment and 544 million cases of near vision impairment caused by URE worldwide in 2007. Approximately 47 000 additional full-time functional clinical refractionists and 18 000 ophthalmic dispensers would be required to provide refractive care services for these individuals. The global cost of educating the additional personnel and of establishing, maintaining and operating the refractive care facilities needed was estimated to be around 20 000 million United States dollars (US$) and the upper-limit cost was US$ 28 000 million. The estimated loss in global gross domestic product due to distance vision impairment caused by URE was US$ 202 000 million annually. Conclusion The cost of establishing and operating the educational and refractive care facilities required to deal with vision impairment resulting from URE was a small proportion of the global loss in productivity associated with that vision impairment. PMID:23109740

  20. Refraction near the horizon-an empirical approach. Part 1: terrestrial refraction of the dip.

    PubMed

    Tschudin, Marcel E

    2016-04-20

    This study aims at providing improved closed-form refraction estimates for observations near the horizon. In this first part, over 1800 previously published direct measurements of the horizon's depression (dip) over the sea are reanalyzed using a nonconventional robust procedure for coping with numerous real, large, and asymmetric outliers from abnormal dips. The derived 1-parameter function agrees with those proposed in modern almanacs and for land surveying. It is found that the dips of warmer and colder sea surfaces vs. air are best described with two different functions. The two proposed 3-parameter functions, also using temperature difference between air and sea and wind speed, reduce the estimated error of the 1-parameter function by ∼⅓ and the number of outliers by ∼⅔.

  1. 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

  2. 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

  3. Application of seismic-refraction techniques to hydrologic studies

    USGS Publications Warehouse

    Haeni, F.P.

    1988-01-01

    During the past 30 years, seismic-refraction methods have been used extensively in petroleum, mineral, and engineering investigations and to some extent for hydrologic applications. Recent advances in equipment, sound sources, and computer interpretation techniques make seismic refraction a highly effective and economical means of obtaining subsurface data in hydrologic studies. Aquifers that can be defined by one or more high-seismic-velocity surface, such as (1) alluvial or glacial deposits in consolidated rock valleys, (2) limestone or sandstone underlain by metamorphic or igneous rock, or (3) saturated unconsolidated deposits overlain by unsaturated unconsolidated deposits, are ideally suited for seismic-refraction methods. These methods allow economical collection of subsurface data, provide the basis for more efficient collection of data by test drilling or aquifer tests, and result in improved hydrologic studies. This manual briefly reviews the basics of seismic-refraction theory and principles. It emphasizes the use of these techniques in hydrologic investigations and describes the planning, equipment, field procedures, and interpretation techniques needed for this type of study. Further-more, examples of the use of seismic-refraction techniques in a wide variety of hydrologic studies are presented.

  4. Application of seismic-refraction techniques to hydrologic studies

    USGS Publications Warehouse

    Haeni, F.P.

    1986-01-01

    Seismic-refraction methods have been extensively used in petroleum, mineral, and engineering investigations and to some extent, for hydrologic applications during the past 30 years. Recent advances in equipment, sound sources, and computer-interpretation techniques make seismic-refraction methods a highly effective and economical means of obtaining subsurface data in hydrologic studies. Aquifers that can be defined by one or more high seismic-velocity surfaces, such as alluvial or glacial deposits in consolidated rock valleys, limestone or sandstone underlain by metamorphic or igneous rock, or saturated unconsolidated deposits overlain by unsaturated unconsolidated deposits, are ideally suited for applying seismic-refraction methods. These methods allow the economical collection of subsurface data and provide the basis for more efficient collection of subsurface data by test drilling or aquifer tests and results in improved hydrologic studies. This manual briefly reviews the basics of seismic refraction theory and principles. It emphasizes the use of this technique in hydrologic investigations and describes the planning, equipment, field procedures, and interpretation techniques needed for this type of study. Examples of the use of seismic refraction techniques in a wide variety of hydrologic studies are presented. (USGS)

  5. Modeling refractive metasurfaces in series as a single metasurface

    NASA Astrophysics Data System (ADS)

    Toor, Fatima; Guneratne, Ananda C.

    2016-03-01

    Metasurfaces are boundaries between two media that are engineered to induce an abrupt phase shift in propagating light over a distance comparable to the wavelength of the light. Metasurface applications exploit this rapid phase shift to allow for precise control of wavefronts. The phase gradient is used to compute the angle at which light is refracted using the generalized Snell's Law. [1] In practice, refractive metasurfaces are designed using a relatively small number of phaseshifting elements such that the phase gradient is discrete rather than continuous. Designing such a metasurface requires finding phase-shifting elements that cover a full range of phases (a phase range) from 0 to 360 degrees. We demonstrate an analytical technique to calculate the refraction angle due to multiple metasurfaces arranged in series without needing to account for the effect of each individual metasurface. The phase gradients of refractive metasurfaces in series may be summed to obtain the phase gradient of a single equivalent refractive metasurface. This result is relevant to any application that requires a system with multiple metasurfaces, such as biomedical imaging [2], wavefront correctors [3], and beam shaping [4].

  6. 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.

  7. 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.

  8. On the refraction of longitudinal waves in compressible media

    SciTech Connect

    Henderson, L.F.

    1988-07-01

    The refraction of plane shock waves in media with arbitrary equations of state is discussed. Previous work is reviewed briefly, and a rigorous definition of wave impedance is formulated. Earlier definitions are shown to be unsatisfactory. The impedance is combined with the boundary conditions at the media interface in order to study both head-on and oblique shock incidence. The impedance determines the nature of the reflected and transmitted waves, their intensities, and the fractions of energy and power that are reflected and transmitted. The refractive index is also defined; it determines whether or not a wave will be refracted and also helps to determine whether the wave system will be regular or irregular. The fundamental law of refraction is derived and shown to be a consequence of the fact that an arbitrary point on a shock or an expansion wave follows a ray path of minimum time between any points on the path. This is a generalization of Fermat's principle to media that are deformed and convected by the waves propagating through them. There is also a detailed discussion of a wide variety of refractions at head-on and at glancing incidence. 40 refs., 19 figs.

  9. Transient Thermal Analysis of a Refractive Secondary Solar Concentrator

    NASA Technical Reports Server (NTRS)

    Geng, Steven M.; Macosko, Robert P.

    1999-01-01

    A secondary concentrator is an optical device that accepts solar energy from a primary concentrator and further intensifies and directs the solar flux. The refractive secondary is one such device; fabricated from an optically clear solid material that can efficiently transmit the solar energy by way of refraction and total internal reflection. When combined with a large state-of-the-art rigid or inflatable primary concentrator, the refractive secondary enables solar concentration ratios of 10,000 to 1. In support of potential space solar thermal power and propulsion applications, the NASA Glenn Research Center is developing a single-crystal refractive secondary concentrator for use at temperatures exceeding 2000K. Candidate optically clear single-crystal materials like sapphire and zirconia are being evaluated for this application. To support this evaluation, a three-dimensional transient thermal model of a refractive secondary concentrator in a typical solar thermal propulsion application was developed. This paper describes the model and presents thermal predictions for both sapphire and zirconia prototypes. These predictions are then used to establish parameters for analyzing and testing the materials for their ability to survive thermal shock and stress.

  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. 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.

  13. A pitfall in shallow shear-wave refraction surveying

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Park, C.B.; Wightman, E.; Nigbor, R.

    2002-01-01

    The shallow shear-wave refraction method works successfully in an area with a series of horizontal layers. However, complex near-surface geology may not fit into the assumption of a series of horizontal layers. That a plane SH-wave undergoes wave-type conversion along an interface in an area of nonhorizontal layers is theoretically inevitable. One real example shows that the shallow shear-wave refraction method provides velocities of a converted wave rather than an SH- wave. Moreover, it is impossible to identify the converted wave by refraction data itself. As most geophysical engineering firms have limited resources, an additional P-wave refraction survey is necessary to verify if velocities calculated from a shear-wave refraction survey are velocities of converted waves. The alternative at this time may be the surface wave method, which can provide reliable S-wave velocities, even in an area of velocity inversion (a higher velocity layer underlain by a lower velocity layer). ?? 2002 Elsevier Science B.V. All rights reserved.

  14. Symmetry breaking and optical negative index of closed nanorings

    NASA Astrophysics Data System (ADS)

    Kanté, Boubacar; Park, Yong-Shik; O'Brien, Kevin; Shuldman, Daniel; Lanzillotti-Kimura, Norberto D.; Jing Wong, Zi; Yin, Xiaobo; Zhang, Xiang

    2012-11-01

    Metamaterials have extraordinary abilities, such as imaging beyond the diffraction limit and invisibility. Many metamaterials are based on split-ring structures, however, like atomic orbital currents, it has long been believed that closed rings cannot produce negative refractive index. Here we report a low-loss and polarization-independent negative-index metamaterial made solely of closed metallic nanorings. Using symmetry breaking that negatively couples the discrete nanorings, we measured negative phase delay in our composite ‘chess metamaterial’. The formation of an ultra-broad Fano-resonance-induced optical negative-index band, spanning wavelengths from 1.3 to 2.3 μm, is experimentally observed in this structure. This discrete and mono-particle negative-index approach opens exciting avenues towards symmetry-controlled topological nanophotonics with on-demand linear and nonlinear responses.

  15. Anomalous refraction of guided waves via embedded acoustic metasurfaces

    NASA Astrophysics Data System (ADS)

    Zhu, Hongfei; Semperlotti, Fabio

    2016-04-01

    We illustrate the design of acoustic metasurfaces based on geometric tapers and embedded in thin-plate structures. The metasurface is an engineered discontinuity that enables anomalous refraction of guided wave modes according to the Generalized Snell's Law. Locally-resonant geometric torus-like tapers are designed in order to achieve metasurfaces having discrete phase-shift profiles that enable a high level of control of refraction of the wavefronts. Results of numerical simulations show that anomalous refraction can be achieved on transmitted anti-symmetric modes (A0) either when using a symmetric (S0) or anti-symmetric (A0) incident wave, where the former case clearly involves mode conversion mechanisms.

  16. Interpretation of the Faust equation for a conventional refracting prism

    NASA Astrophysics Data System (ADS)

    Tewari, R. D.; Ghodgaonkar, A. M.; Gokhale, V. D.

    1995-10-01

    The Faust formula for a conventional refracting prism is interpreted in terms of the angle of incidence ( i1) and the angle of deviation (δ). Three new possibilities emerge, namely: (a) keeping the angle of incidence ( i1) constant and varying the angle of deviation (δ); (b) keeping the angle of deviation constant and varying the angle of incidence ( i1); (c) modification of the closed forms of Murty's expression and its equivalence to (b). Using paraxial approximation and keeping the angle of incidence ( i1) and angle of deviation (δ) constant we obtain a relation between the refractive index and the base length ( b) of a prism and, in principle, this is equivalent to the Marcuse variation for optical fibres. The condition for a Littrow prism, as well as for polarized radiation is derived. An expression to estimate the spectral bandwidth (SBW) of the instrument is also derived. Experimental values of refractive index at different wavelengths are within confidence limits.

  17. SH-wave refraction/reflection and site characterization

    USGS Publications Warehouse

    Wang, Z.; Street, R.L.; Woolery, E.W.; Madin, I.P.

    2000-01-01

    Traditionally, nonintrusive techniques used to characterize soils have been based on P-wave refraction/reflection methods. However, near-surface unconsolidated soils are oftentimes water-saturated, and when groundwater is present at a site, the velocity of the P-waves is more related to the compressibility of the pore water than to the matrix of the unconsolidated soils. Conversely, SH-waves are directly relatable to the soil matrix. This makes SH-wave refraction/reflection methods effective in site characterizations where groundwater is present. SH-wave methods have been used extensively in site characterization and subsurface imaging for earthquake hazard assessments in the central United States and western Oregon. Comparison of SH-wave investigations with geotechnical investigations shows that SH-wave refraction/reflection techniques are viable and cost-effective for engineering site characterization.

  18. Underwater optical wireless communications: depth-dependent beam refraction.

    PubMed

    Johnson, Laura J; Green, Roger J; Leeson, Mark S

    2014-11-01

    Global refractive gradients in seawater cause pointing problems for optical wireless communications. A refractive index depth profile of the Pacific Ocean was calculated from measured salinity, temperature, and pressure, determining the end points of a refracted and nonrefracted 200 m communication link. Numerical ray tracing was used with a point source for angles between 10° and 80° and transmission wavelengths of 500-650 nm; the maximum end-point difference found was 0.23 m. A 500 nm laser with a 0.57° full-angle FOV was traced; the nonrefracted receiver location was outside the FOV for all links angled >15° to the vertical. However, most pointing issues underwater are unlikely to be significant with suitable FOV choice and natural scattering of the source.

  19. An open magnet utilizing ferro-refraction current magnification.

    PubMed

    Pulyer, Yuly; Hrovat, Mirko I

    2002-02-01

    Ferro-refraction is the field magnification that is obtained when a current segment is near a high magnetic permeable boundary. It is shown that ferro-refraction may be used in the design of magnets for NMR or MRI to increase the efficiency of these magnets. The field may be modeled analytically with the Biot--Savart law and the inclusion of mirror image currents. Ferro-refraction is particularly useful in the design of monohedral magnets, magnets producing a remote homogeneous region which have the magnetic sources arranged to one side. These magnets have also been called planar magnets. Two designs for a monohedral magnet which produce good agreement between experimental and analytic results are presented. PMID:11846587

  20. 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.

  1. Refraction effects on the Galileo probe telemetry carrier frequency

    NASA Technical Reports Server (NTRS)

    Atkinson, D. H.; Spilker, T. R.

    1991-01-01

    As the Galileo probe relay radio link (RRL) signal propagates outward through the Jovian atmosphere, the atmosphere will manifest itself in two ways. First, the geometric path length of the signal is increased, resulting in a small change of the RRL signal departure angle from the proble (transmitter). Secondly, the velocity of the signal is decreased. For a spherical, static atmosphere with a known profile of refractivity versus altitude the effects of refraction on the RRL frequency can be found using a variation of standard ray-tracing techniques, whereby the ray departure angle is found by an iterative process. From the dispersive characteristics of a mixture of hydrogen and helium with trace amounts of methane and ammonia a simple model of the Jovian atmosphere is constructed assuming spherical symmetry and uniform mixing. The contribution to the RRL Doppler frequency arising from refraction is calculated, and its effect on the Doppler wind measurements is discussed.

  2. 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.

  3. 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.

  4. How To Prepare Materials With a Desired Refraction Coefficient?

    SciTech Connect

    Ramm, A. G.

    2010-05-21

    In this talk a method is described for preparing materials with a desired refraction coefficient. The method consists of embedding into a material with known refraction coefficient many small particles of size a. The number of particles per unit volume around any point is prescribed, the distance between neighboring particles is O(a{sup (2-kappa/3)}) as a->0, 00. The refraction coefficient is the coefficient n{sup 2}(x) in the wave equation [nabla{sup 2}+kappa{sup 2}n{sup 2}(x)]u = 0.

  5. The posterior chamber phakic refractive lens (PRL): a review

    PubMed Central

    Pérez-Cambrodí, R J; Piñero, D P; Ferrer-Blasco, T; Cerviño, A; Brautaset, R

    2013-01-01

    Implantation of phakic intraocular lenses (pIOLs) is a reversible refractive procedure, preserving the patient's accommodative function with minimal induction of higher order aberrations compared with corneal photoablative procedures. Despite this, as an intraocular procedure, it has potential risks such as cataracts, chronic uveitis, pupil ovalization, corneal endothelial cell loss, pigmentary dispersion syndrome, pupillary block glaucoma, astigmatism, or endophthalmitis. Currently, only two models of posterior chamber pIOLs are commercially available, the implantable collammer lens (STAAR Surgical Co.) and the phakic refractive lens (PRL; Zeiss Meditec). The number of published reports on the latter is very low, and some concerns still remain about its long-term safety. The present article reviews the published literature on the outcomes after PRL implantation in order to provide a general overview and evaluate its real potential as a surgical refractive option. PMID:23222559

  6. Remediation of refractive amblyopia by optical correction alone.

    PubMed

    Moseley, Merrick J; Neufeld, Meir; McCarry, Bernadette; Charnock, Avril; McNamara, Rowena; Rice, Tricia; Fielder, Alistair

    2002-07-01

    Amblyopia--the commonest vision abnormality of childhood--is characterized by a loss of visual acuity usually of one eye only. Treatment aims to promote function of the amblyopic eye and does this by restricting, usually through occlusion, the competitive advantage of the fellow eye. Recent experimental evidence demonstrates that the recovery of vision following early deprivation is facilitated by increasing visually evoked activity. An analogous approach in humans is to minimise image blur by correcting refractive error prior to treatment--a practice which may account for the poorly quantified improvements in visual acuity sometimes attributed to 'spectacle adaptation'. Here we describe clinically significant gains in visual acuity obtained over a period of 4-24 weeks in a group of amblyopic children arising solely in response to the correction of refractive error. Consequences for the clinical management of refractive amblyopia are discussed. PMID:12162480

  7. Calculation of turbulence effects in an upward-refracting atmosphere

    NASA Astrophysics Data System (ADS)

    Gilbert, Kenneth E.; di, Xiao; Raspet, Richard

    1990-06-01

    The effect of atmospheric turbulence on sound propagation was investigated for both nonrefractive and refractive atmospheres, using the parabolic equation method of Gilbert and White (1989) in conjunction with a two-dimensional atmospheric turbulence model. The calculations for a nonrefractive atmosphere gave good agreement with experimental data and with Daigle's (1979) theory, while calculations for an upward-refractive atmosphere gave reasonable agreement with the data of Weiner and Keast (1959). It is concluded that, for a receiver deep in a shadow zone and for frequencies greater than a few hundred hertz, the measured sound-pressure level is due almost entirely to the sound scattered into the shadow zone by atmospheric turbulence. Consequently, for upward refraction and frequencies above a few hundred hertz, turbulence must be included in long-range propagation calculations.

  8. 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

  9. Ionic control of ocular growth and refractive change

    PubMed Central

    Crewther, Sheila G.; Liang, Helena; Junghans, Barbara M.; Crewther, David P.

    2006-01-01

    The physiological mechanisms underlying the abnormal vitreal and ocular growth and myopic refractive errors induced under conditions of visual form deprivation in many animal species, including humans, are unknown. This study demonstrates, using energy dispersive x-ray microanalysis, a systematic pattern of changes in the elemental distribution of K, Na, and Cl across the entire retina in experimental form deprivation myopia and in the 5 days required for refractive normalization after occluder removal. In our report we link the ionic environment associated with physiological activity of the retina under a translucent occluder to refractive change and describe large but reversible environmentally driven increases in potassium, sodium, and chloride abundances in the neural retina. Our results are consistent with the notion of ionically driven fluid movements as the vector underlying the myopic increase in ocular size. New treatments for myopia, which currently affects nearly half of the human population, may result. PMID:17023537

  10. Refractive errors in Cameroonians diagnosed with complete oculocutaneous albinism

    PubMed Central

    Eballé, André Omgbwa; Mvogo, Côme Ebana; Noche, Christelle; Zoua, Marie Evodie Akono; Dohvoma, Andin Viola

    2013-01-01

    Background Albinism causes significant eye morbidity and amblyopia in children. The aim of this study was to determine the refractive state in patients with complete oculocutaneous albinism who were treated at the Gynaeco-Obstetric and Paediatric Hospital, Yaoundé, Cameroon and evaluate its effect on vision. Methods We carried out this retrospective study at the ophthalmology unit of our hospital. All oculocutaneous albino patients who were treated between March 1, 2003 and December 31, 2011 were included. Results Thirty-five patients (70 eyes) diagnosed with complete oculocutaneous albinism were enrolled. Myopic astigmatism was the most common refractive error (40%). Compared with myopic patients, those with myopic astigmatism and hypermetropic astigmatism were four and ten times less likely, respectively, to demonstrate significant improvement in distance visual acuity following optical correction. Conclusion Managing refractive errors is an important way to reduce eye morbidity-associated low vision in oculocutaneous albino patients. PMID:23901257

  11. Barren Acidic Soil Assessment using Seismic Refraction Survey

    NASA Astrophysics Data System (ADS)

    Tajudin, S. A. A.; Abidin, M. H. Z.; Madun, A.; Zawawi, M. H.

    2016-07-01

    Seismic refraction method is one of the geophysics subsurface exploration techniques used to determine subsurface profile characteristics. From past experience, seismic refraction method is commonly used to detect soil layers, overburden, bedrock, etc. However, the application of this method on barren geomaterials remains limited due to several reasons. Hence, this study was performed to evaluate the subsurface profile characteristics of barren acidic soil located in Ayer Hitam, Batu Pahat, Johor using seismic refraction survey. The seismic refraction survey was conducted using ABEM Terraloc MK 8 (seismograph), a sledge hammer weighing 7 kg (source) and 24 units of 10 Hz geophones (receiver). Seismic data processing was performed using OPTIM software which consists of SeisOpt@picker (picking the first arrival and seismic configureuration data input) and SeisOpt@2D (generating 2D image of barren acidic soil based on seismic velocity (primary velocity, Vp) distribution). It was found that the barren acidic soil profile consists of three layers representing residual soil (Vp= 200-400 m/s) at 0-2 m, highly to completely weathered soil (Vp= 500-1800 m/s) at 3-8 m and shale (Vp= 2100-6200 m/s) at 9-20 m depth. Furthermore, result verification was successfully done through the correlation of seismic refraction data based on physical mapping and the geological map of the study area. Finally, it was found that the seismic refraction survey was applicable for subsurface profiling of barren acidic soil as it was very efficient in terms of time, cost, large data coverage and sustainable.

  12. Barriers to Use of Refractive Services in Mozambique

    PubMed Central

    Thompson, Stephen; Naidoo, Kovin; Gonzalez-Alvarez, Carmen; Harris, Geoff; Chinanayi, Farai; Loughman, James

    2015-01-01

    ABSTRACT Purpose Uncorrected refractive error remains a leading cause of visual impairment (VI) across the globe with Mozambique being no exception. The establishment of an optometry profession in Mozambique that is integrated into the public health system denotes significant progress with refractive services becoming available to the population. As the foundations of a comprehensive refractive service have now been established, this article seeks to understand what barriers may limit their uptake by the general population and inform decision making on improved service delivery. Methods A community-based cross-sectional study using two-stage cluster sampling was conducted. Participants with VI were asked to identify barriers that were reflective of their experiences and perceptions of accessing refractive services. A total of 4601 participants were enumerated from 76 clusters in Nampula, Mozambique. Results A total of 1087 visually impaired participants were identified (884 with near and 203 with distance impairment). Cost was the most frequently cited barrier, identified by more than one in every two participants (53%). Other barriers identified included lack of felt need (20%), distance to travel (15%), and lack of awareness (13%). In general, no significant influence of sex or type of VI on barrier selection was found. Location had a significant impact on the selection of several barriers. Pearson χ2 analysis indicated that participants from rural areas were found to feel disadvantaged regarding the distance to services (p ≤ 0.001) and adequacy of hospital services (p = 0.001). Conclusions For a comprehensive public sector refractive service to be successful in Mozambique, those planning its implementation must consider cost and affordability. A clear strategy for overcoming lack of felt need will also be needed, possibly in the form of improved advocacy and health promotion. The delivery of refractive services in more remote rural areas merits careful and

  13. Peripheral Refraction with and without Contact Lens Correction

    PubMed Central

    Shen, Jie; Clark, Christopher A.; Soni, P. Sarita; Thibos, Larry N.

    2011-01-01

    Purpose Peripheral refractive error degrades the quality of retinal images and has been hypothesized to be a stimulus for the development of refractive error. The purpose of this study was to investigate the changes in refractive error across the horizontal visual field produced by contact lenses (CLs) and to quantify the effect of CLs on peripheral image blur. Methods A commercial Shack-Hartmann aberrometer measured ocular wavefront aberrations in 5° steps across the central 60° of visual field along the horizontal meridian before and after CLs correction. Wavefront refractions for peripheral lines-of-sight were based on the full elliptical pupil encountered in peripheral measurements. Curvature of field is the change in peripheral spherical equivalent relative to the eye’s optical axis. Results Hyperopic curvature of field in the naked eye increases with increasing amounts central myopic refractive error as predicted by Atchison (2006). For an eccentricity of E degrees, field curvature is approximately E percent of foveal refractive error. Rigid gas permeable (RGP) lenses changed field curvature in the myopic direction twice as much as soft contact lenses (SCLs). Both of these effects varied with CLs power. For all lens powers, SCL cut the degree of hyperopic field curvature in half whereas RGP lenses nearly eliminated field curvature. The benefit of reduced field curvature was partially offset by increased oblique astigmatism. The net reduction of retinal blur due to CLs is approximately constant across the visual field. Conclusions Both SCL and RGP lenses reduced the degree of hyperopic field curvature present in myopic eyes, with RGP lenses having greater effect. The tradeoff between field curvature and off-axis astigmatism with RGP lenses may limit their effectiveness for control of myopia progression. These results suggest that axial growth mechanisms that depend on retinal image quality will be affected more by RGP than by SCL lenses. PMID:20601913

  14. Low-threshold Optical limiting and Nonlinear refraction in Nanocomposite films of Light Green dye-polymer system

    NASA Astrophysics Data System (ADS)

    Sreeja, S.; Louie Frobel, P. G.; Mayadevi, S.; Suresh, S. R.; Muneera, C. I.

    2015-02-01

    Poly(vinyl alcohol) (PVA) /Light Green (LG) dye nanocomposites were fabricated and their structure, microstructure, linear and nonlinear optical properties were investigated. The samples were characterized as nanocomposites with dye molecules encapsulated between the larger molecules (molecular chains) of the polymer host PVA. The nonlinear refraction behaviour was investigated employing the Z-scan technique, using a continuous wave (cw) He- Ne laser operating at 632.8 nm, as the excitation source. The samples displayed negative nonlinear refraction (self-defocusing) under the experimental conditions. Low-threshold optical limiting behaviour exhibited by the PVA based nanocomposites was demonstrated using an aperture limited geometry. The low limiting thresholds (~4 mW and ~2.4 mW) observed for the samples indicate that these low cost and durable nanocomposite films are potential media for optical limiting application under cw laser light excitation.

  15. Spatial and temporal dissociation of AQP4 and Kir4.1 expression during induction of refractive errors

    PubMed Central

    Goodyear, Melinda J.; Crewther, Sheila G.; Murphy, Melanie J.; Giummarra, Loretta; Hazi, Agnes; Junghans, Barbara M.; Crewther, David P.

    2010-01-01

    Purpose Spatial co-localization of aquaporin water channels (AQP4) and inwardly rectifying potassium ion channels (Kir4.1) on the endfeet regions of glial cells has been suggested as the basis of functionally interrelated mechanisms of osmoregulation in brain edema. The aim of this study was to investigate the spatial and temporal changes in the expression of AQP4 and Kir4.1 channels in an avascular retina during the first week of the optical induction of refractive errors. Methods Three-day-old hatchling chicks were randomly assigned to three groups and either did not wear lenses or were monocularly goggled with ±10D lenses for varying times up to 7 days before biometric assessment. Retinal tissue was prepared either for western blot analysis to show the presence of the AQP4 and Kir4.1 protein in the chick retina or for immunolocalization using AQP4 and Kir4.1 antibodies to determine the regional distribution and intensity of labeling during the induction of refractive errors. Results As expected, ultrasonography demonstrated that all eyes showed rapid elongation post hatching. Negative lens-wearing eyes elongated faster than fellow eyes or normal non goggled eyes and became progressively more myopic with time post lensing. Positive lens-wearing eyes showed reduced ocular growth compared to normal controls and developed a hyperopic refraction. Quantitative immunohistochemistry revealed the upregulation of AQP4 channel expression on Müller cells in the retinal nerve fiber layer during the first 2 days of negative lens wear. Kir4.1 channel upregulation in the inner plexiform layer was only found on day 4 of positive lens wear during the development of refractive hyperopia. Conclusions These results indicate that the expression of AQP4 and Kir4.1 channels on Müller cells is associated with the changes in ocular volume seen during the induction of refractive errors. However, the sites of greatest expression and the temporal pattern of the upregulation of AQP4 and

  16. Inter-tester Agreement in Refractive Error Measurements

    PubMed Central

    Huang, Jiayan; Maguire, Maureen G.; Ciner, Elise; Kulp, Marjean T.; Quinn, Graham E.; Orel-Bixler, Deborah; Cyert, Lynn A.; Moore, Bruce; Ying, Gui-Shuang

    2014-01-01

    Purpose To determine the inter-tester agreement of refractive error measurements between lay and nurse screeners using the Retinomax Autorefractor (Retinomax) and the SureSight Vision Screener (SureSight). Methods Trained lay and nurse screeners measured refractive error in 1452 preschoolers (3- to 5-years old) using the Retinomax and the SureSight in a random order for screeners and instruments. Inter-tester agreement between lay and nurse screeners was assessed for sphere, cylinder and spherical equivalent (SE) using the mean difference and the 95% limits of agreement. The mean inter-tester difference (lay minus nurse) was compared between groups defined based on child’s age, cycloplegic refractive error, and the reading’s confidence number using analysis of variance. The limits of agreement were compared between groups using the Brown-Forsythe test. Inter-eye correlation was accounted for in all analyses. Results The mean inter-tester differences (95% limits of agreement) were −0.04 (−1.63, 1.54) Diopter (D) sphere, 0.00 (−0.52, 0.51) D cylinder, and −0.04 (1.65, 1.56) D SE for the Retinomax; and 0.05 (−1.48, 1.58) D sphere, 0.01 (−0.58, 0.60) D cylinder, and 0.06 (−1.45, 1.57) D SE for the SureSight. For either instrument, the mean inter-tester differences in sphere and SE did not differ by the child’s age, cycloplegic refractive error, or the reading’s confidence number. However, for both instruments, the limits of agreement were wider when eyes had significant refractive error or the reading’s confidence number was below the manufacturer’s recommended value. Conclusions Among Head Start preschool children, trained lay and nurse screeners agree well in measuring refractive error using the Retinomax or the SureSight. Both instruments had similar inter-tester agreement in refractive error measurements independent of the child’s age. Significant refractive error and a reading with low confidence number were associated with worse inter

  17. Experimental verification of electro-refractive phase modulation in graphene

    PubMed Central

    Mohsin, Muhammad; Neumaier, Daniel; Schall, Daniel; Otto, Martin; Matheisen, Christopher; Lena Giesecke, Anna; Sagade, Abhay A.; Kurz, Heinrich

    2015-01-01

    Graphene has been considered as a promising material for opto-electronic devices, because of its tunable and wideband optical properties. In this work, we demonstrate electro-refractive phase modulation in graphene at wavelengths from 1530 to 1570 nm. By integrating a gated graphene layer in a silicon-waveguide based Mach-Zehnder interferometer, the key parameters of a phase modulator like change in effective refractive index, insertion loss and absorption change are extracted. These experimentally obtained values are well reproduced by simulations and design guidelines are provided to make graphene devices competitive to contemporary silicon based phase modulators for on-chip applications. PMID:26061415

  18. Additive manufacturing of a trifocal diffractive-refractive lens

    NASA Astrophysics Data System (ADS)

    Hinze, Ulf; El-Tamer, Ayman; Doskolovich, Leonid L.; Bezus, Evgeni A.; Reiß, Stefan; Stolz, Heinrich; Guthoff, Rudolf F.; Stachs, Oliver; Chichkov, Boris

    2016-08-01

    The application of two-photon polymerization and molding for the fabrication of a multifocal diffractive-refractive lens operating in water is studied. The fabricated lens is of aspheric shape and combines diffractive and refractive parts in a single element to generate three foci. The lens performance is characterized by visualization of the beam propagation in a transparent basin filled with water containing fluorescein. The experimental measurements are in good agreement with the theoretical description. The obtained results are promising for the realization of trifocal intraocular lenses with predetermined light intensity distribution between the foci.

  19. Refraction of sound by a shear layer - Experimental assessment

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1979-01-01

    An experimental study was conducted to determine the refraction angle and amplitude changes associated with sound transmission through a circular, open jet shear layer. Both on-axis and off-axis acoustic source locations were used. Source frequency varied from 1 kHz to 10 kHz while freestream Mach number varied from 0.1 to 0.4. The experimental results were compared with an existing refraction theory which was extended to account for off-axis source positions. A simple experiment was also conducted to assess the importance of turbulence scattering between 1 kHz and 25 kHz.

  20. 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

  1. 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.

  2. Analysis of ionospheric refraction error corrections for GRARR systems

    NASA Technical Reports Server (NTRS)

    Mallinckrodt, A. J.; Parker, H. C.; Berbert, J. H.

    1971-01-01

    A determination is presented of the ionospheric refraction correction requirements for the Goddard range and range rate (GRARR) S-band, modified S-band, very high frequency (VHF), and modified VHF systems. The relation ships within these four systems are analyzed to show that the refraction corrections are the same for all four systems and to clarify the group and phase nature of these corrections. The analysis is simplified by recognizing that the range rate is equivalent to a carrier phase range change measurement. The equation for the range errors are given.

  3. Meningitis - gram-negative

    MedlinePlus

    Gram-negative meningitis ... Acute bacterial meningitis can be caused by Gram-negative bacteria. Meningococcal and H. influenzae meningitis are caused by Gram-negative bacteria and are covered in detail in other articles. This article ...

  4. 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)

  5. 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.

  6. Measurement of nonlinear refractive index of organic materials by z-scan

    NASA Astrophysics Data System (ADS)

    Fontalvo, M.; Garcia, A.; Valbuena, S.; Racedo, F.

    2016-02-01

    The nonlinear effects characterization by using the Z-Scan transmission technique in many materials has generated great in forest according to the technological necessities. The majority part of the nonlinear effects can be described by the classic electromagnetic theory, with the electrical susceptibility in the constitutive equation that relates the electrical polarization with the electrical field. In this work the sign and refractive index magnitude and the nonlinear absorption coefficient of the following organic substance were determined: methylene-blue, rodamine LD, vegetable powder and gentian violet a hundred percent pure dissolved in isopropyl alcohol, a laser Nd: YAG was used as a source excitation. The bunch of laser was focused with a lens of ten centimeters of focal length; by using a displacement system the sweeping of twenty centimeters was realized. The following results of the normalized curves of the transmittance in function of the z position were obtained applying the Sheik- Bahae theory: The nonlinear refractive index of the dye shows an increase in function of its concentration and the power of exciting of the laser with negative nonlinear sign in the majority of the sample.

  7. 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.

  8. Studies of the Reflection, Refraction and Internal Reflection of Light

    ERIC Educational Resources Information Center

    Lanchester, P. C.

    2014-01-01

    An inexpensive apparatus and associated experiments are described for studying the basic laws of reflection and refraction of light at an air-glass interface, and multiple internal reflections within a glass block. In order to motivate students and encourage their active participation, a novel technique is described for determining the refractive…

  9. 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.

  10. 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.

  11. Refractive and diffractive neutron optics with reduced chromatic aberration

    NASA Astrophysics Data System (ADS)

    Poulsen, S. O.; Poulsen, H. F.; Bentley, P. M.

    2014-12-01

    Thermal neutron beams are an indispensable tool in physics research. The spatial and the temporal resolution attainable in experiments are dependent on the flux and collimation of the neutron beam which remain relatively poor, even for modern neutron sources. These difficulties may be mitigated by the use of optics for focusing and imaging. Refractive and diffractive optical elements, e.g. compound refractive lenses and Fresnel zone plates, are attractive due to their low cost, and simple alignment. These optical elements, however, suffer from chromatic aberration, which limit their effectiveness to highly monochromatic beams. This paper presents two novel concepts for focusing and imaging non-monochromatic thermal neutron beams with well-known optical elements: (1) a fast mechanical transfocator based on a compound refractive lens, which actively varies the number of individual lenses in the beam path to focus and image a time-of-flight beam, and (2) a passive optical element consisting of a compound refractive lens, and a Fresnel zone plate, which may focus and image both continuous and pulsed neutron beams.

  12. 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.

  13. 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.

  14. 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.

  15. VOCAR: An experiment in Variability of Coastal Atmospheric Refractivity

    NASA Astrophysics Data System (ADS)

    Paulus, Richard A.

    1994-10-01

    A previous radio-meteorological experiment conducted along the coast of southern California showed a high correlation between UHF signals and the base of the elevated temperature inversion. A reanalysis of this experimental data with a recently developed hybrid propagation model confirmed this correlation and a method to remotely sense the refractive structure was proposed. An experiment called Variability of Coastal Atmospheric Refractivity (VOCAR) was designed under a larger program called Coastal Variability Analysis, Measurements, and Prediction. VOCAR is a multi-year experimental effort to investigate the variability of atmospheric refractivity with emphasis on the coastal zone. The experiment is being conducted by the Naval Command, Control and Ocean Surveillance Center RDT&E Division jointly with the Naval Air Warfare Center Weapons Division, Point Mugu, CA, the Naval Research Laboratory (Washington, DC and Monterey), and the Naval Postgraduate School. In addition, the National Oceanic and Atmospheric Administration Environmental Technology Laboratory, Penn State University Applied Research Laboratory and Johns Hopkins University Applied Physics Laboratory participated in the intensive measurement phase of VOCAR. The objectives of VOCAR are to provide an assessment capability for horizontally varying refractivity conditions in a coastal environment and to develop a remote sensing capability. The propagation measurements being made during VOCAR consist of monitoring signal strength variations of VHF/UHF transmitters in the southern California coastal region. Corresponding meteorological measurements are made during routine, special, and intensive observation periods. Measurements began in May 1993 and will be conducted periodically through 1994.

  16. S-wave refraction survey of alluvial aggregate

    USGS Publications Warehouse

    Ellefsen, Karl J.; Tuttle, Gary J.; Williams, Jackie M.; Lucius, Jeffrey E.

    2005-01-01

    An S-wave refraction survey was conducted in the Yampa River valley near Steamboat Springs, Colo., to determine how well this method could map alluvium, a major source of construction aggregate. At the field site, about 1 m of soil overlaid 8 m of alluvium that, in turn, overlaid sedimentary bedrock. The traveltimes of the direct and refracted S-waves were used to construct velocity cross sections whose various regions were directly related to the soil, alluvium, and bed-rock. The cross sections were constrained to match geologic logs that were developed from drill-hole data. This constraint minimized the ambiguity in estimates of the thickness and the velocity of the alluvium, an ambiguity that is inherent to the S-wave refraction method. In the cross sections, the estimated S-wave velocity of the alluvium changed in the horizontal direction, and these changes were attributed to changes in composition of the alluvium. The estimated S-wave velocity of the alluvium was practically constant in the vertical direc-tion, indicating that the fine layering observed in the geologic logs could not be detected. The S-wave refraction survey, in conjunction with independent information such as geologic logs, was found to be suitable for mapping the thickness of the alluvium.

  17. Refraction effects in soft x-ray multilayer blazed gratings.

    PubMed

    Voronov, D L; Salmassi, F; Meyer-Ilse, J; Gullikson, E M; Warwick, T; Padmore, H A

    2016-05-30

    A 2500 lines/mm Multilayer Blazed Grating (MBG) optimized for the soft x-ray wavelength range was fabricated and tested. The grating coated with a W/B4C multilayer demonstrated a record diffraction efficiency in the 2nd blazed diffraction order in the energy range from 500 to 1200 eV. Detailed investigation of the diffraction properties of the grating demonstrated that the diffraction efficiency of high groove density MBGs is not limited by the normal shadowing effects that limits grazing incidence x-ray grating performance. Refraction effects inherent in asymmetrical Bragg diffraction were experimentally confirmed for MBGs. The refraction affects the blazing properties of the MBGs and results in a shift of the resonance wavelength of the gratings and broadening or narrowing of the grating bandwidth depending on diffraction geometry. The true blaze angle of the MBGs is defined by both the real structure of the multilayer stack and by asymmetrical refraction effects. Refraction effects can be used as a powerful tool in providing highly efficient suppression of high order harmonics.

  18. 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.

  19. 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.

  20. Calculation of refraction indices of triple chalcogenide crystals

    NASA Astrophysics Data System (ADS)

    Kamenshchikov, V. N.; Suslikov, L. M.

    2015-04-01

    We use Harrison's bond-orbital method to calculate high frequency refraction indices of AgGaS2, CdGa2S4, and CdGa2Se4 crystals. We demonstrate a satisfactory agreement between obtained results and experimental data.

  1. Statistics of the residual refraction errors in laser ranging data

    NASA Technical Reports Server (NTRS)

    Gardner, C. S.

    1977-01-01

    A theoretical model for the range error covariance was derived by assuming that the residual refraction errors are due entirely to errors in the meteorological data which are used to calculate the atmospheric correction. The properties of the covariance function are illustrated by evaluating the theoretical model for the special case of a dense network of weather stations uniformly distributed within a circle.

  2. Automatic diagnostic system for measuring ocular refractive errors

    NASA Astrophysics Data System (ADS)

    Ventura, Liliane; Chiaradia, Caio; de Sousa, Sidney J. F.; de Castro, Jarbas C.

    1996-05-01

    Ocular refractive errors (myopia, hyperopia and astigmatism) are automatic and objectively determined by projecting a light target onto the retina using an infra-red (850 nm) diode laser. The light vergence which emerges from the eye (light scattered from the retina) is evaluated in order to determine the corresponding ametropia. The system basically consists of projecting a target (ring) onto the retina and analyzing the scattered light with a CCD camera. The light scattered by the eye is divided into six portions (3 meridians) by using a mask and a set of six prisms. The distance between the two images provided by each of the meridians, leads to the refractive error of the referred meridian. Hence, it is possible to determine the refractive error at three different meridians, which gives the exact solution for the eye's refractive error (spherical and cylindrical components and the axis of the astigmatism). The computational basis used for the image analysis is a heuristic search, which provides satisfactory calculation times for our purposes. The peculiar shape of the target, a ring, provides a wider range of measurement and also saves parts of the retina from unnecessary laser irradiation. Measurements were done in artificial and in vivo eyes (using cicloplegics) and the results were in good agreement with the retinoscopic measurements.

  3. Intraocular lens calculations status after corneal refractive surgery.

    PubMed

    Seitz, B; Langenbucher, A

    2000-02-01

    With the increasing number of keratorefractive surgical procedures, an increasing number of cataract surgeries in eyes after keratorefractive surgery is anticipated within a few decades. Although cataract extraction seems to be feasible without major technical obstacles, intraocular lens (IOL) power calculation turned out to be problematic. Insertion of the measured average K-readings (= "central corneal power" = keratometric diopters) after myopic radial keratotomy (RK), photorefractive keratectomy (PRK), or laser in situ keratomileusis (LASIK) into standard IOL power-predictive formulas commonly results in substantial undercorrection and postoperative hyperopic refraction or anisometropia. In this article, the major reasons for IOL power miscalculations (which are different for RK versus RRK/LASIK) are discussed based on model calculations and based on case series of cataract surgeries, methods for improved assessment of keratometric diopters as the major underlying problem are exemplary illustrated, and finally a clinical step-by-step approach to minimize IOL power miscalculations status after corneal refractive surgery is suggested. The "clinical history method" (i.e., subtraction of the spherical equivalent [SEQ] change after refractive surgery from the original K-reading) should be applied whenever refraction and K-reading before the keratorefractive procedure are available to cataract surgeons. In addition, more than one modern third-generation formula (e.g., Haigis, Hoffer Q, Holladay 2, or SRK/T) but not a regression formula (e.g., SRK I or SRK II) should be applied and the highest resulting IOL power should be used for the implant.

  4. Ultra low-loss, isotropic optical negative-index metamaterial based on hybrid metal-semiconductor nanowires

    PubMed Central

    Paniagua-Domínguez, R.; Abujetas, D. R.; Sánchez-Gil, J. A.

    2013-01-01

    Recently, many fascinating properties predicted for metamaterials (negative refraction, superlensing, electromagnetic cloaking,…) were experimentally demonstrated. Unfortunately, the best achievements have no direct translation to the optical domain, without being burdened by technological and conceptual difficulties. Of particular importance within the realm of optical negative-index metamaterials (NIM), is the issue of simultaneously achieving strong electric and magnetic responses and low associated losses. Here, hybrid metal-semiconductor nanowires are proposed as building blocks of optical NIMs. The metamaterial thus obtained, highly isotropic in the plane normal to the nanowires, presents a negative index of refraction in the near-infrared, with values of the real part well below −1, and extremely low losses (an order of magnitude better than present optical NIMs). Tunability of the system allows to select the operating range in the whole telecom spectrum. The design is proven in configurations such as prisms and slabs, directly observing negative refraction. PMID:23514968

  5. Novel high refractive index, thermally conductive additives for high brightness white LEDs

    NASA Astrophysics Data System (ADS)

    Hutchison, Richard Stephen

    making this decrease in transparency important to note. This decrease in transparency may be partially or wholly why a decrease in light extraction efficiency is observed at the 33.5 wt% zirconia loading fraction used for the LED samples. Preliminary aging studies under full and enhanced power conditions were conducted over 500 and 1000 hours to observe any changes in the spectral output power and phosphor conversion efficiency of the LEDs due to inclusion of the zirconia nanoparticles. It was found that the nanoparticles have no negative effect on the aging properties but also show no enhancement in relative output power over a preliminary aging study. However, their inclusion did result in increased phosphor conversion efficiency over the use of an unfilled silicone. This increase was seen as around a 10% or greater enhancement for the nanocomposite over that for the base Sylgard silicone. These experiments were originally conducted on the commercially available methylated Sylgard 184 silicone and then again on a higher refractive index methyl-phenyl silicone from Momentive. While some of the results from the Momentive silicone were perplexing, it was seen that, even without the inclusion of nanoparticles, the Momentive silicone had a higher refractive index, better aging properties, and a higher phosphor conversion efficiency over 500 hours under enhanced power conditions, warranting further studies into methyl-phenyl silicone nanocomposites.

  6. Optical propagation through a homogeneous mixture of positive and negative index materials

    NASA Astrophysics Data System (ADS)

    Aylo, Rola; Banerjee, Partha P.; Nehmetallah, George

    2008-08-01

    Metamaterials, which maybe the answer to "perfect lensing", are often fabricated as a periodic array of elements which exhibit negative refractive index or negative permeability/permittivity. In this work, we outline and illustrate a framework that can model propagation through a homogeneous and random mixture of positive and negative index materials. We achieve this by using a matrix-based multilayered approach, and a random sequence of positive and negative index materials, and by incorporating all possible combinations of such layers. Plane wave propagation is investigated, and aggregated transmittivity is calculated. We show that near-zero net refractive index maybe achieved through a random homogeneous mixture of positive and negative index materials.

  7. 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

  8. DISCRIMINATING BETWEEN CLOUDY, HAZY, AND CLEAR SKY EXOPLANETS USING REFRACTION

    SciTech Connect

    Misra, Amit K.; Meadows, Victoria S.

    2014-11-01

    We propose a method to distinguish between cloudy, hazy, and clear sky (free of clouds and hazes) exoplanet atmospheres that could be applicable to upcoming large aperture space- and ground-based telescopes such as the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT). These facilities will be powerful tools for characterizing transiting exoplanets, but only after a considerable amount of telescope time is devoted to a single planet. A technique that could provide a relatively rapid means of identifying haze-free targets (which may be more valuable targets for characterization) could potentially increase the science return for these telescopes. Our proposed method utilizes broadband observations of refracted light in the out-of-transit spectrum. Light refracted through an exoplanet atmosphere can lead to an increase of flux prior to ingress and subsequent to egress. Because this light is transmitted at pressures greater than those for typical cloud and haze layers, the detection of refracted light could indicate a cloud- or haze-free atmosphere. A detection of refracted light could be accomplished in <10 hr for Jovian exoplanets with JWST and <5 hr for super-Earths/mini-Neptunes with E-ELT. We find that this technique is most effective for planets with equilibrium temperatures between 200 and 500 K, which may include potentially habitable planets. A detection of refracted light for a potentially habitable planet would strongly suggest the planet was free of a global cloud or haze layer, and therefore a promising candidate for follow-up observations.

  9. 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.

  10. Refractive Secondary Solar Concentrator Demonstrated High-Temperature Operation

    NASA Technical Reports Server (NTRS)

    Wong, Wayne A.

    2002-01-01

    Space applications that utilize solar thermal energy--such as electric power conversion systems, thermal propulsion systems, and furnaces--require highly efficient solar concentration systems. The NASA Glenn Research Center is developing the refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. When used in combination with advanced lightweight primary concentrators, such as inflatable thin films, the refractive secondary concentrator enables very high system concentration ratios and very high temperatures. Last year, Glenn successfully demonstrated a secondary concentrator throughput efficiency of 87 percent, with a projected efficiency of 93 percent using an antireflective coating. Building on this achievement, Glenn recently successfully demonstrated high-temperature operation of the secondary concentrator when it was used to heat a rhenium receiver to 2330 F. The high-temperature demonstration of the concentrator was conducted in Glenn's 68-ft long Tank 6 thermal vacuum facility equipped with a solar simulator. The facility has a rigid panel primary concentrator that was used to concentrate the light from the solar simulator onto the refractive secondary concentrator. NASA Marshall Space Flight Center provided a rhenium cavity, part of a solar thermal propulsion engine, to serve as the high-temperature receiver. The prototype refractive secondary concentrator, measuring 3.5 in. in diameter and 11.2 in. long, is made of single-crystal sapphire. A water-cooled splash shield absorbs spillage light outside of the 3.5-in. concentrator aperture. Multilayer foil insulation composed of tungsten, molybdenum, and niobium is used to minimize heat loss from the hightemperature receiver. A liquid-cooled canister calorimeter is used to measure the heat loss through the multilayer foil insulation.

  11. Predicted and measured boundary layer refraction for advanced turboprop propeller noise

    NASA Technical Reports Server (NTRS)

    Dittmar, James H.; Krejsa, Eugene A.

    1990-01-01

    Currently, boundary layer refraction presents a limitation to the measurement of forward arc propeller noise measured on an acoustic plate in the NASA Lewis 8- by 6-Foot Supersonic Wind Tunnel. The use of a validated boundary layer refraction model to adjust the data could remove this limitation. An existing boundary layer refraction model is used to predict the refraction for cases where boundary layer refraction was measured. In general, the model exhibits the same qualitative behavior as the measured refraction. However, the prediction method does not show quantitative agreement with the data. In general, it overpredicts the amount of refraction for the far forward angles at axial Mach number of 0.85 and 0.80 and underpredicts the refraction at axial Mach numbers of 0.75 and 0.70. A more complete propeller source description is suggested as a way to improve the prediction method.

  12. Double Negativity in 3D Space Coiling Metamaterials.

    PubMed

    Maurya, Santosh K; Pandey, Abhishek; Shukla, Shobha; Saxena, Sumit

    2016-09-21

    Metamaterials displaying negative refractive index has remarkable potential to facilitate the manipulation of incident waves for wide variety of applications such as cloaking, superlensing and the like. Space-coiling approach is a recently explored technique to achieve extreme properties. The space coiling phenomena cause less energy absorption as compared to local resonating phenomena for obtaining extreme parameters. Here we show extreme properties in doubly negative 3D space coiling acoustic metamaterials. Frequency dispersive spectrum of extreme constitutive parameters has been calculated for 2D maze and 3D space coiling labyrinthine structure. This is in good agreement to the calculated acoustic band dispersion.

  13. Double Negativity in 3D Space Coiling Metamaterials

    NASA Astrophysics Data System (ADS)

    Maurya, Santosh K.; Pandey, Abhishek; Shukla, Shobha; Saxena, Sumit

    2016-09-01

    Metamaterials displaying negative refractive index has remarkable potential to facilitate the manipulation of incident waves for wide variety of applications such as cloaking, superlensing and the like. Space-coiling approach is a recently explored technique to achieve extreme properties. The space coiling phenomena cause less energy absorption as compared to local resonating phenomena for obtaining extreme parameters. Here we show extreme properties in doubly negative 3D space coiling acoustic metamaterials. Frequency dispersive spectrum of extreme constitutive parameters has been calculated for 2D maze and 3D space coiling labyrinthine structure. This is in good agreement to the calculated acoustic band dispersion.

  14. Double Negativity in 3D Space Coiling Metamaterials

    PubMed Central

    Maurya, Santosh K.; Pandey, Abhishek; Shukla, Shobha; Saxena, Sumit

    2016-01-01

    Metamaterials displaying negative refractive index has remarkable potential to facilitate the manipulation of incident waves for wide variety of applications such as cloaking, superlensing and the like. Space-coiling approach is a recently explored technique to achieve extreme properties. The space coiling phenomena cause less energy absorption as compared to local resonating phenomena for obtaining extreme parameters. Here we show extreme properties in doubly negative 3D space coiling acoustic metamaterials. Frequency dispersive spectrum of extreme constitutive parameters has been calculated for 2D maze and 3D space coiling labyrinthine structure. This is in good agreement to the calculated acoustic band dispersion. PMID:27649966

  15. Negative-index media for matter-wave optics.

    PubMed

    Baudon, J; Hamamda, M; Grucker, J; Boustimi, M; Perales, F; Dutier, G; Ducloy, M

    2009-04-10

    We consider the extension of optical metamaterials to matter waves and then the down scaling of metaoptics to nanometric wavelengths. We show that the generic property of pulsed comoving magnetic fields allows us to fashion the wave-number dependence of the atomic phase shift. It can be used to produce a transient negative group velocity of an atomic wave packet, which results into a negative refraction of the matter wave. Application to slow metastable argon atoms Ar(3P2) shows that the device is able to operate either as an efficient beam splitter or an atomic metalens. PMID:19392417

  16. Double Negativity in 3D Space Coiling Metamaterials.

    PubMed

    Maurya, Santosh K; Pandey, Abhishek; Shukla, Shobha; Saxena, Sumit

    2016-01-01

    Metamaterials displaying negative refractive index has remarkable potential to facilitate the manipulation of incident waves for wide variety of applications such as cloaking, superlensing and the like. Space-coiling approach is a recently explored technique to achieve extreme properties. The space coiling phenomena cause less energy absorption as compared to local resonating phenomena for obtaining extreme parameters. Here we show extreme properties in doubly negative 3D space coiling acoustic metamaterials. Frequency dispersive spectrum of extreme constitutive parameters has been calculated for 2D maze and 3D space coiling labyrinthine structure. This is in good agreement to the calculated acoustic band dispersion. PMID:27649966

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  19. Ambient illuminance, retinal dopamine release and refractive development in chicks.

    PubMed

    Cohen, Yuval; Peleg, Edna; Belkin, Michael; Polat, Uri; Solomon, Arieh S

    2012-10-01

    Form deprivation and low illuminance of ambient light are known to induce myopia in chicks. Low concentrations of retinal dopamine, a light-driven neurohormone, was previously shown to be associated with form deprivation myopia. In the present study we examined the dependence of retinal dopamine release in chicks on illuminance during light-dark cycles and in continuous light, and the role of retinal dopamine release in illuminance dependent refractive development. Newly hatched chicks (n = 166) were divided into two experimental groups, a dopamine (n = 88) and a refraction group (n = 78). Both groups were further divided into six illumination groups for exposure of chicks to illuminances of 50, 500 or 10,000 lux of incandescent illumination (referred to throughout as low, medium, and high illuminance, respectively), either under a light-dark cycle with lights on between 7 AM and 7 PM or under continuous illumination. For the dopamine experiment, chicks were euthanized and vitreous was extracted on day 14 post-hatching at 7, 8 AM and 1 PM. Vitreal dihydroxyphenylacetic acid (DOPAC) and dopamine concentrations were quantified by high-performance liquid chromatography coupled to electrochemical detection. For the refraction experiment, chicks underwent refraction, keratometry and A-scan ultrasonography on days 30, 60 and 90 post-hatching, and each of those measurements was correlated with vitreal DOPAC concentration measured at 1 PM (representing the index of retinal dopamine release). The results showed that under light-dark cycles, vitreal DOPAC concentration was strongly correlated with log illuminance, and was significantly correlated with the developing refraction, corneal radius of curvature, and axial length values. On day 90, low vitreal DOPAC concentrations were associated with myopia (-2.41 ± 1.23 D), flat cornea, deep anterior and vitreous chambers, and thin lens. Under continuous light, vitreal DOPAC concentrations measured at 1 PM in the low, medium

  20. Empirical estimates of cumulative refraction errors associated with procedurally constrained levelings based on the Gaithersburg- Tucson refraction tests of the National Geodetic Survey.

    USGS Publications Warehouse

    Castle, R.O.; Gilmore, T.D.; Mark, R.K.; Shaw, R.H.

    1985-01-01

    Analyses of results of the National Geodetic Survey's leveling refraction tests indicate that the standard deviation about the mean (sigma) for high-scale minus low-scale rod readings closely correlates with measured refraction error. Use of this relation in conjunction with values for sigma obtained from routinely constrainted surveys provides a basis for estimating the refraction error associated with levelings of stipulated order and class. -Authors

  1. Nonlinear refraction of silver hydrosols during their aggregation

    SciTech Connect

    Karpov, S V; Kodirov, M K; Ryasnyansky, A I; Slabko, V V

    2001-10-31

    The relation between the degree of aggregation of silver hydrosols and their nonlinear refractive index n{sub 2} is studied experimentally. It is found that the sign of n{sub 2} at a wavelength of 1.064 {mu}m changes with increasing the aggregation degree, which corresponds to the replacing of self-focusing by self-defocusing. The observed effects are explained based on the analysis of a change in nonlinear dispersion of the medium, taking into account the interaction between phases and the photochromic effects, which are typical for colloidal structures with fractal geometry. It is shown that the change in the sign of the nonlinear refractive index of hydrosols upon irradiation by laser pulses of duration of less than 10{sup -7} s is caused by the perturbation of resonances of silver and water and by the competition between Kerr nonlinear polarisations involving these resonances. (nonlinear optical phenomena and devices)

  2. 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.

  3. Optical refractive synchronization: bit error rate analysis and measurement

    NASA Astrophysics Data System (ADS)

    Palmer, James R.

    1999-11-01

    The direction of this paper is to describe the analytical tools and measurement techniques used at SilkRoad to evaluate the optical and electrical signals used in Optical Refractive Synchronization for transporting SONET signals across the transmission fiber. Fundamentally, the direction of this paper is to provide an outline of how SilkRoad, Inc., transports a multiplicity of SONET signals across a distance of fiber > 100 Km without amplification or regeneration of the optical signal, i.e., one laser over one fiber. Test and measurement data are presented to reflect how the SilkRoad technique of Optical Refractive Synchronization is employed to provide a zero bit error rate for transmission of multiple OC-12 and OC-48 SONET signals that are sent over a fiber optical cable which is > 100Km. The recovery and transformation modules are described for the modification and transportation of these SONET signals.

  4. Diamond refractive lens for hard x-ray focusing

    NASA Astrophysics Data System (ADS)

    Snigirev, Anatoly A.; Yunkin, Vecheslav; Snigireva, Irina; Di Michiel, Marco; Drakopoulos, Michael; Kouznetsov, Sergey; Shabel'nikov, Leonid; Grigoriev, Michail; Ralchenko, Victor; Sychov, I.; Hoffmann, Martin; Voges, Edgar I.

    2002-11-01

    We report the manufacture and experimental tests of first diamond refractive lenses for hard X-ray focusing. A transfer molding technique based on diamond growth on a pre-patterned silicon mould was employed to fabricate diamond refractive lenses. Diamond films were produced by microwave plasma enhanced chemical vapor deposition. The lenses were designed for 50 cm focal length at energy 9 keV. Experimental tests were performed at the ESRF ID15 (wiggler) and ID22 (undulator) beamlines using monochromatic, "pink" and white X-ray radiation in the energy range from 6 to 40 keV. Focusing in the order of 1-2 microns was achieved. To evaluate the lens microstructure properties phase contrast imaging and diffraction techniques (SAXS and WAXS) were applied.

  5. 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.

  6. Shock wave refraction enhancing conditions on an extended interface

    SciTech Connect

    Markhotok, A.; Popovic, S.

    2013-04-15

    We determined the law of shock wave refraction for a class of extended interfaces with continuously variable gradients. When the interface is extended or when the gas parameters vary fast enough, the interface cannot be considered as sharp or smooth and the existing calculation methods cannot be applied. The expressions we derived are general enough to cover all three types of the interface and are valid for any law of continuously varying parameters. We apply the equations to the case of exponentially increasing temperature on the boundary and compare the results for all three types of interfaces. We have demonstrated that the type of interface can increase or inhibit the shock wave refraction. Our findings can be helpful in understanding the results obtained in energy deposition experiments as well as for controlling the shock-plasma interaction in other settings.

  7. 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.

  8. 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.

  9. Effect of parallel refraction on magnetospheric upper hybrid waves

    NASA Technical Reports Server (NTRS)

    Engel, J.; Kennel, C. F.

    1984-01-01

    Large amplitude (not less than 10 mV/m) electrostatic plasma waves near the upper hybrid (UH) frequency have been observed from 0 to 50 deg magnetic latitude (MLAT) during satellite plasma-pause crossings. A three-dimensional numerical ray-tracing calculation, based on an electron distribution measured during a GEOS 1 dayside intense upper-hybrid wave event, suggests how UH waves might achieve such large amplitudes away from the geomagnetic equator. Refractive effects largely control the wave amplification and, in particular, the unavoidable refraction due to parallel geomagnetic field gradients restricts growth to levels below those observed. However, a cold electron density gradient parallel to the field can lead to upper hybrid wave growth that can account for the observed emission levels.

  10. The increasing importance of translational vision research in refractive surgery.

    PubMed

    Hafezi, Farhad; Kristoffersen-Hafezi, Nikki

    2012-02-01

    Addressing these business and financial components of research, we believe that including a section on translational vision research especially for refractive surgery will be a welcome addition to the readership of the Journal. Although the section "Translational Science" is new, the Journal has published a number of articles in past years that would have been ideal candidates for such a section. The inaugural Translational Science article in this month's issue is fron Santhiago and colleagues on short-term cell death and inflammation after intracorneal inlay implantation in rabbits. Although not all scientists are in agreement with the promotion of this term, the Journal aims to provide different outlooks and modern usage of translational research in this way to advance the field of refractive surgery.

  11. 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.

  12. Negative ion generator

    DOEpatents

    Stinnett, Regan W.

    1984-01-01

    A negative ion generator is formed from a magnetically insulated transmission line having a coating of graphite on the cathode for producing negative ions and a plurality of apertures on the opposed anode for the release of negative ions. Magnetic insulation keeps electrons from flowing from the cathode to the anode. A transverse magnetic field removes electrons which do escape through the apertures from the trajectory of the negative ions.

  13. Negative ion generator

    DOEpatents

    Stinnett, R.W.

    1984-05-08

    A negative ion generator is formed from a magnetically insulated transmission line having a coating of graphite on the cathode for producing negative ions and a plurality of apertures on the opposed anode for the release of negative ions. Magnetic insulation keeps electrons from flowing from the cathode to the anode. A transverse magnetic field removes electrons which do escape through the apertures from the trajectory of the negative ions. 8 figs.

  14. Sentential Negation in English

    ERIC Educational Resources Information Center

    Mowarin, Macaulay

    2009-01-01

    This paper undertakes a detailed analysis of sentential negation in the English language with Chomsky's Government-Binding theory of Transformational Grammar as theoretical model. It distinguishes between constituent and sentential negation in English. The essay identifies the exact position of Negation phrase in an English clause structure. It…

  15. Low scatter edge blackening compounds for refractive optical elements

    SciTech Connect

    Lewis, I.T.; Telkamp, A.R. ); Ledebuhr, A.G. )

    1989-07-25

    Perkin-Elmer's Applied Optics Operation recently delivered several prototype wide-field-of-view (WFOV), F/2.8, 250 mm efl, near diffraction limited, concentric refractive lenses to Lawrence Livermore National Laboratory (LLNL). In these lenses, special attention was paid to reducing stray light to allow viewing of very dim objects. Because of the very large FOV, the use of a long baffle to eliminate direct illumination of lens edges was not practical. With the existing relatively short baffle design, one-bounce stray light paths off the element edges are possible. The scattering off the inside edges thus had to be kept to an absolute minimum. While common means for blackening the edges of optical elements are easy to apply and quite cost effective for normal lens assemblies, their blackening effect is limited by the Fresnel reflection due to the index of refraction mismatch at the glass boundary. At high angles of incidence, total internal reflection (TIR) might occur ruining the effect of the blackening process. An index-matched absorbing medium applied to the edges of such elements is the most effective approach for reducing the amount of undesired light reflected or scattered off these edges. The presence of such a medium provides an extended path outside the glass boundary in which an absorptive non-scattering dye can be used to eliminate light that might otherwise have propagated to the focal plane. Perkin-Elmer and LLNL undertook a program to develop epoxy-based dye carrier compounds with refractive indices corresponding to the glass types used in the WFOV lens. This program involved the measuring of the refractive index of a number of epoxy compounds and catalysts, the experimental combination of epoxies to match our glass indices, and the identification of a suitable non-scattering absorptive dye. 10 figs., 3 tabs.

  16. Computed estimation of visual acuity after laser refractive keratectomy

    NASA Astrophysics Data System (ADS)

    Rol, Pascal O.; Parel, Jean-Marie A.; Hanna, Khalil

    1991-06-01

    A number of surgical techniques has been developed to correct ametropia (refractive defaults) of the eye by changing the anterior corneal radius. Because the air-cornea interface makes up for about two-third of the refractive power of the eye, a refractive correction is obtained by a suitable photoablation of the cornea. For this purpose, e.g., an ArF excimer laser which emits a wavelength of 193 nm is being used. After a mechanical removal of the epithelium, the Bowman's layer and the corneal stroma are photoablated on typically 50% of the central surface of the cornea with various precomputed shapes. Methods using a variable diaphragm1 or a scanning slit2 are being utilized. After regrowth of the epithelium, a smooth interface with air develops itself, which can be attributed to a mechanical equilibration. Yet, SEM studies have shown that with such kind of treatments, irregularities can remain in the new stromal surface (Fig. 1). A possible explanation for this effect is associated with an inhomogeneous energy distribution of the laser beam profile3. To some extent, the stromal surface is equalized by the epithelial layer during healing& However, as the corneal epithelium and stroma have different refractive indices, a scatter of the incident light may result causing a haze in the cornea and a blur of the image at the retina. In such a case the resolution and the contrast performance of the eye which is expected from a successful operation, may be reduced. This study is an attempt to quantify the vision blur as a function of the deformation observed at the epithelium-stroma interface.

  17. 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.

  18. 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

  19. Refraction data survey: 2nd generation correlation of myopia.

    PubMed

    Greene, Peter R; Medina, Antonio

    2016-10-01

    The objective herein is to provide refraction data, myopia progression rate, prevalence, and 1st and 2nd generation correlations, relevant to whether myopia is random or inherited. First- and second-generation ocular refraction data are assembled from N = 34 families, average of 2.8 children per family. From this group, data are available from N = 165 subjects. Inter-generation regressions are performed on all the data sets, including correlation coefficient r, and myopia prevalence [%]. Prevalence of myopia is [M] = 38.5 %. Prevalence of high myopes with |R| >6 D is [M-] = 20.5 %. Average refraction is  = -1.84 D ± 3.22 (N = 165). For the high myopes, |R| >6 D, prevalence for the parents is [M-] = 25 %, for the 2nd generation [M-] = 16.5 %. Average myopia level for the high myopes, both generations, is  = -7.52 D ± 1.31 D (N = 33). Regression parameters are calculated for all the data sets, yielding correlation coefficients in the range r = 0.48-0.72 for some groups of myopes and high myopes, fathers to daughters, and mothers to sons. Also of interest, some categories show essentially no correlation, -0.20 < r < 0.20, indicating that the refractive errors occur randomly. Time series results show myopia diopter rates = -0.50 D/year.

  20. Controllable nonlinear refraction characteristics in hydrogenated nanocrystalline silicon

    SciTech Connect

    Zheng, D. Q.; Ye, Q. H.; Shen, W. Z.; Su, W. A.

    2014-02-07

    Nonlinear refraction (NLR) of hydrogenated nanocrystalline silicon (nc-Si:H) has been investigated through the close aperture Z-scan method. We demonstrate a significant NLR and a unique feature of controllable NLR characteristics between saturable and Kerr NLR with the incident photon energy. We numerically evaluate the proportion of these two mechanisms in different wavelengths by a modified NLR equation. The band tail of nc-Si:H appears to play a crucial role in such NLR responses.

  1. Digital elevation model visibility including Earth's curvature and atmosphere refraction

    NASA Astrophysics Data System (ADS)

    Santossilva, Ewerton; Vieiradias, Luiz Alberto

    1990-03-01

    There are some instances in which the Earth's curvature and the atmospheric refraction, optical or electronic, are important factors when digital elevation models are used for visibility calculations. This work deals with this subject, suggesting a practical approach to solve this problem. Some examples, from real terrain data, are presented. The equipment used was an IBM-PC like computer with a SITIM graphic card.

  2. Lithium metal for x-ray refractive optics

    NASA Astrophysics Data System (ADS)

    Pereira, Nino R.; Arms, Dohn A.; Clarke, Roy; Dierker, Steve B.; Dufresne, Eric; Foster, D.

    2001-12-01

    Lithium is the best material for refractive x-ray lenses, with peak performance around 8 keV. To date we have built a prototype of Cederstrom's so-called alligator lens, and have tested the lens with beamline 7ID's 10 keV x-rays on the Advanced Photon Source at Argonne National Laboratories. To date we have attained only a threefold gain, most likely limited by surface roughness that is avoidable with more careful manufacturing techniques.

  3. Association between Ocular Sensory Dominance and Refractive Error Asymmetry

    PubMed Central

    Bi, Hua; Ekure, Edgar; Su, Binbin; Wu, Haoran; Huang, Yifei; Zhang, Bin; Jiang, Jun

    2015-01-01

    Purpose To investigate the association between ocular sensory dominance and interocular refractive error difference (IRED). Methods A total of 219 subjects were recruited. The refractive errors were determined by objective refraction with a fixation target located 6 meters away. 176 subjects were myopic, with 83 being anisometropic (IRED ≥ 0.75 D). 43 subjects were hyperopic, with 22 being anisometropic. Sensory dominance was measured with a continuous flashing technique with the tested eye viewing a Gabor increasing in contrast and the fellow eye viewing a Mondrian noise decreasing in contrast. The log ratio of Mondrian to Gabor’s contrasts was recorded when a subject just detected the tilting direction of the Gabor during each trial. T-test was used to compare the 50 values collected from each eye, and the t-value was used as a subject’s ocular dominance index (ODI) to quantify the degree of ocular dominance. A subject with ODI ≥ 2 (p < 0.05) had clear dominance and the eye with larger mean ratio was the dominant one. Otherwise, a subject had an unclear dominance. Results The anisometropic subjects had stronger ocular dominance in comparison to non-anisometropic subjects (rank-sum test, p < 0.01 for both myopic and hyperopic subjects). In anisometropic subjects with clear dominance, the amplitude of the anisometropia was correlated with ODI values (R = 0.42, p < 0.01 in myopic anisometropic subjects; R = 0.62, p < 0.01 in hyperopic anisometropic subjects). Moreover, the dominant eyes were more myopic in myopic anisometropic subjects (sign-test, p < 0.05) and less hyperopic in hyperopic anisometropic subjects (sign-test, p < 0.05). Conclusion The degree of ocular sensory dominance is associated with interocular refractive error difference. PMID:26295803

  4. Prevalence of Amblyopia and Refractive Errors Among Primary School Children

    PubMed Central

    Rajavi, Zhale; Sabbaghi, Hamideh; Baghini, Ahmad Shojaei; Yaseri, Mehdi; Moein, Hamidreza; Akbarian, Shadi; Behradfar, Narges; Hosseini, Simin; Rabei, Hossein Mohammad; Sheibani, Kourosh

    2015-01-01

    Purpose: To determine the prevalence of amblyopia and refractive errors among 7 to 12-year-old primary school children in Tehran, Iran. Methods: This population-based cross-sectional study included 2,410 randomly selected students. Visual acuity was tested using an E-chart on Yang vision tester. Refractive errors were measured by photorefractometry and cycloautorefraction. Strabismus was checked using cover test. Direct ophthalmoscopy was used to assess the anterior segment, lens opacities, red reflex and fundus. Functional amblyopia was defined as best corrected visual acuity ≤20/40 in one or both eyes with no anatomical problems. Results: Amblyopia was present in 2.3% (95% CI: 1.8% to 2.9%) of participants with no difference between the genders. Amblyopic subjects were significantly younger than non-amblyopic children (P=0.004). Overall, 15.9% of hyperopic and 5.9% of myopic cases had amblyopia. The prevalence of hyperopia ≥+2.00D, myopia ≤-0.50D, astigmatism ≥0.75D, and anisometropia (≥1.00D) was 3.5%, 4.9%, 22.6%, and 3.9%, respectively. With increasing age, the prevalence of myopia increased (P<0.001), that of hyperopia decreased (P=0.007), but astigmatism showed no change. Strabismus was found in 2.3% of cases. Strabismus (OR=17.9) and refractive errors, especially anisometropia (OR=12.87) and hyperopia (OR=11.87), were important amblyogenic risk factors. Conclusion: The high prevalence of amblyopia in our subjects in comparison to developed countries reveals the necessity of timely and sensitive screening methods. Due to the high prevalence of amblyopia among children with refractive errors, particularly high hyperopia and anisometropia, provision of glasses should be specifically attended by parents and supported by the Ministry of Health and insurance organizations. PMID:27051485

  5. Refractive Errors and Strabismus in Down's Syndrome in Korea

    PubMed Central

    Han, Dae Heon; Kim, Kyun Hyung

    2012-01-01

    Purpose The aims of this study were to examine the distribution of refractive errors and clinical characteristics of strabismus in Korean patients with Down's syndrome. Methods A total of 41 Korean patients with Down's syndrome were screened for strabismus and refractive errors in 2009. Results A total of 41 patients with an average age of 11.9 years (range, 2 to 36 years) were screened. Eighteen patients (43.9%) had strabismus. Ten (23.4%) of 18 patients exhibited esotropia and the others had intermittent exotropia. The most frequently detected type of esotropia was acquired non-accommodative esotropia, and that of exotropia was the basic type. Fifteen patients (36.6%) had hypermetropia and 20 (48.8%) had myopia. The patients with esotropia had refractive errors of +4.89 diopters (D, ±3.73) and the patients with exotropia had refractive errors of -0.31 D (±1.78). Six of ten patients with esotropia had an accommodation weakness. Twenty one patients (63.4%) had astigmatism. Eleven (28.6%) of 21 patients had anisometropia and six (14.6%) of those had clinically significant anisometropia. Conclusions In Korean patients with Down's syndrome, esotropia was more common than exotropia and hypermetropia more common than myopia. Especially, Down's syndrome patients with esotropia generally exhibit clinically significant hyperopic errors (>+3.00 D) and evidence of under-accommodation. Thus, hypermetropia and accommodation weakness could be possible factors in esotropia when it occurs in Down's syndrome patients. Based on the results of this study, eye examinations of Down's syndrome patients should routinely include a measure of accommodation at near distances, and bifocals should be considered for those with evidence of under-accommodation. PMID:23204801

  6. Peripheral refractive errors in myopic, emmetropic, and hyperopic young subjects

    NASA Astrophysics Data System (ADS)

    Seidemann, Anne; Schaeffel, Frank; Guirao, Antonio; Lopez-Gil, Noberto; Artal, Pablo

    2002-12-01

    To gain more insight into the relationship between foveal and peripheral refractive errors in humans, spheres, cylinders, and their axes were binocularly measured across the visual field in myopic, emmetropic, and hyperopic groups of young subjects. Both automated infrared photorefraction (the ``PowerRefractor'' www. plusoptix.de) and a double-pass technique were used because the PowerRefractor provided extensive data from the central 44 deg of the visual field in a very convenient and fast way. Two-dimensional maps for the average cross cylinders and spherical equivalents, as well as for the axes of the power meridians of the cylinders, were created. A small amount of lower-field myopia was detected with a significant vertical gradient in spherical equivalents. In the central visual field there was little difference among the three refractive groups. The established double-pass technique provided complementary data also from the far periphery. At 45 deg eccentricity the double-pass technique revealed relatively more hyperopic spherical equivalents in myopic subjects than in emmetropic subjects [+/-2.73+/-2.85 D relative to the fovea, p<0.01 (+/-standard deviation)] and more myopic spherical equivalents in hyperopic subjects (-3.84+/-2.86 D relative to the fovea, p<0.01). Owing to the pronounced peripheral astigmatism, spherical equivalents (refractions with respect to the plane of the circle of least confusion) became myopic relative to the fovea in all three groups. The finding of general peripheral myopia was unexpected. Its possible roles in foveal refractive development are discussed.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Association between Refractive Errors and Ocular Biometry in Iranian Adults

    PubMed Central

    Hashemi, Hassan; Khabazkhoob, Mehdi; Emamian, Mohammad Hassan; Shariati, Mohammad; Miraftab, Mohammad; Yekta, Abbasali; Ostadimoghaddam, Hadi; Fotouhi, Akbar

    2015-01-01

    Purpose: To investigate the association between ocular biometrics such as axial length (AL), anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD) and corneal power (CP) with different refractive errors. Methods: In a cross-sectional study on the 40 to 64-year-old population of Shahroud, random cluster sampling was performed. Ocular biometrics were measured using the Allegro Biograph (WaveLight AG, Erlangen, Germany) for all participants. Refractive errors were determined using cycloplegic refraction. Results: In the first model, the strongest correlations were found between spherical equivalent with axial length and corneal power. Spherical equivalent was strongly correlated with axial length in high myopic and high hyperopic cases, and with corneal power in high hyperopic cases; 69.5% of variability in spherical equivalent was attributed to changes in these variables. In the second model, the correlations between vitreous chamber depth and corneal power with spherical equivalent were stronger in myopes than hyperopes, while the correlations between lens thickness and anterior chamber depth with spherical equivalent were stronger in hyperopic cases than myopic ones. In the third model, anterior chamber depth + lens thickness correlated with spherical equivalent only in moderate and severe cases of hyperopia, and this index was not correlated with spherical equivalent in moderate to severe myopia. Conclusion: In individuals aged 40-64 years, corneal power and axial length make the greatest contribution to spherical equivalent in high hyperopia and high myopia. Anterior segment biometric components have a more important role in hyperopia than myopia. PMID:26730304

  12. Intraocular camera for retinal prostheses: Refractive and diffractive lens systems

    NASA Astrophysics Data System (ADS)

    Hauer, Michelle Christine

    The focus of this thesis is on the design and analysis of refractive, diffractive, and hybrid refractive/diffractive lens systems for a miniaturized camera that can be surgically implanted in the crystalline lens sac and is designed to work in conjunction with current and future generation retinal prostheses. The development of such an intraocular camera (IOC) would eliminate the need for an external head-mounted or eyeglass-mounted camera. Placing the camera inside the eye would allow subjects to use their natural eye movements for foveation (attention) instead of more cumbersome head tracking, would notably aid in personal navigation and mobility, and would also be significantly more psychologically appealing from the standpoint of personal appearances. The capability for accommodation with no moving parts or feedback control is incorporated by employing camera designs that exhibit nearly infinite depth of field. Such an ultracompact optical imaging system requires a unique combination of refractive and diffractive optical elements and relaxed system constraints derived from human psychophysics. This configuration necessitates an extremely compact, short focal-length lens system with an f-number close to unity. Initially, these constraints appear highly aggressive from an optical design perspective. However, after careful analysis of the unique imaging requirements of a camera intended to work in conjunction with the relatively low pixellation levels of a retinal microstimulator array, it becomes clear that such a design is not only feasible, but could possibly be implemented with a single lens system.

  13. 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.

  14. Refractive Secondary Solar Concentrator Being Designed and Developed

    NASA Technical Reports Server (NTRS)

    Macosko, Robert P.; Donovan, Richard M.

    1998-01-01

    As the need for achieving super high temperatures (2000 K and above) in solar heat receivers has developed so has the need for secondary concentrators. These concentrators refocus the already highly concentrated solar energy provided by a primary solar collector, thereby significantly reducing the light entrance aperture of the heat receiver and the resulting infrared radiation heat loss from the receiver cavity. Although a significant amount of research and development has been done on nonimaging hollow reflective concentrators, there has been no other research or development to date on solid, single crystal, refractive concentrators that can operate at temperatures above 2000 K. The NASA Lewis Research Center recently initiated the development of single-crystal, optically clear, refractive secondary concentrators that, combined with a flux extractor, offer a number of significant advantages over the more conventional, hollow, reflective concentrators at elevated temperatures. Such concentrators could potentially provide higher throughput (efficiency), require no special cooling device, block heat receiver material boiloff from the receiver cavity, provide for flux tailoring in the cavity via the extractor, and potentially reduce infrared heat loss via an infrared block coating.The many technical challenges of designing and fabricating high-temperature refractive secondary concentrators and flux extractors include identifying optical materials that can survive the environment (high-temperature, vacuum and/or hydrogen atmosphere), developing coatings for enhanced optical and thermal performance, and developing crystal joining techniques and hardware that can survive launch loads.

  15. 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

  16. 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.

  17. Sound propagation in a refracting atmosphere above an impedance discontinuity

    NASA Astrophysics Data System (ADS)

    Taherzadeh, Shahram; Harrop, Nick

    2002-11-01

    de Jongs formulation of sound propagation above a ground with a single impedance change has been extended to include effects of a refracting atmosphere and atmospheric turbulence. The theory is compared with a numerical algorithm based on a hybrid Boundary Integral Equation/Fast Field Program developed for predicting the propagation of sound in a refracting atmosphere above an uneven, discontinuous terrain. By using the analogy of sound diffraction over curved surfaces to atmospheric refraction over flat ground surfaces, the effect of temperature and wind velocity gradients in the presence of flat ground surfaces can be studied. Measurements of the excess attenuation of sound from a point source over a mixed impedance curved surface are carried out in an anechoic chamber as well as outdoor measurements over a tarmac-grass discontinuity. These measurements are compared with predictions based on the extended de Jong theory and the hybrid BIE/FFP algorithm in the nonturbulent case. Results show that where there is a single discontinuity between acoustically hard and finite impedance surfaces both models are found to give satisfactory agreement with measured data except when the discontinuity is midway between the source and the detector.

  18. On refractive processes in strong laser field quantum electrodynamics

    SciTech Connect

    Di Piazza, A.

    2013-11-15

    Refractive processes in strong-field QED are pure quantum processes, which involve only external photons and the background electromagnetic field. We show analytically that such processes occurring in a plane-wave field and involving external real photons are all characterized by a surprisingly modest net exchange of energy and momentum with the laser field, corresponding to a few laser photons, even in the limit of ultra-relativistic laser intensities. We obtain this result by a direct calculation of the transition matrix element of an arbitrary refractive QED process and accounting exactly for the background plane-wave field. A simple physical explanation of this modest net exchange of laser photons is provided, based on the fact that the laser field couples with the external photons only indirectly through virtual electron–positron pairs. For stronger and stronger laser fields, the pairs cover a shorter and shorter distance before they annihilate again, such that the laser can transfer to them an energy corresponding to only a few photons. These results can be relevant for the future experiments aiming to test strong-field QED at present and next-generation facilities. -- Highlights: •Investigation of the one-loop amplitude of refractive QED processes in a laser field. •The amplitude is suppressed for a large number of net-exchanged laser photons. •Suggestion for first observation of high-nonlinear vacuum effects in a laser field.

  19. Refraction and scattering of sound by a shear layer

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1980-01-01

    The angle and amplitude changes for acoustic waves refracted by a circular open jet shear layer were determined. The generalized refraction theory was assessed experimentally for on axis and off axis acoustic source locations as source frequency varied from 1 kHz to 10 kHz and free stream Mach number varied from 0.1 to 0.4. Angle and amplitude changes across the shear layer show good agreement with theory. Experiments confirm that the refraction theory is independent of shear layer thickness, acoustic source frequency, and source type. A generalized theory is, thus, available for correcting far field noise data acquired in open jet test facilities. The effect of discrete tone scattering by the open jet turbulent shear layer was also studied. Scattering effects were investigated over the same Mach number range as frequency varied from 5 kHz to 15 kHz. Attenuation of discrete tone amplitude and tone broadening were measured as a function of acoustic source position and radiation angle. Scattering was found to be stronger at angles close to the open jet axis than at 90 deg, and becomes stronger as the acoustic source position shifts downstream. A scattering analysis provided an estimate of the onset of discrete tone scattering.

  20. Interferometric analysis of the ablation profile in refractive surgery

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rodríguez, M. I.; López-Olazagasti, E.; Rosales, M. A.; Ramírez-Zavaleta, G.; Cantú, R.; Tepichín, E.

    2008-08-01

    In ophthalmology, the laser excimer corneal surface ablation used to correct the refractive eye defects, such as myopia, astigmatism and hyperopia and, more recently, presbyopia is known as refractive surgery. Typically, the characterization of the corresponding technique, as well as the laser accuracy, is performed by analyzing standard ablation profiles made on PMMA (polymethylmethacrylate) plates. A drawback of this technique is that those plates do not necessarily represent the dimensions of the cornea during the ablation. On the other hand, due to the time varying process of the eye aberrations, the direct eye refractometric measurements can produce some errors. We report in this work the interferometric analysis of the ablation profile obtained with refractive surgery, applied directly on a contact lens. In this case, the resultant ablation profile might be closer to the real profile as well as time invariant. We use, as a reference, a similar contact lens without ablation. The preliminary results of the characterization of the corresponding ablation profile are also presented.