Showing papers on "Total internal reflection published in 1998"

Omnidirectional reflection from a one-dimensional photonic crystal.

Abstract: We demonstrate that one-dimensional photonic crystal structures (such as multilayer films) can exhibit complete reflection of radiation in a given frequency range for all incident angles and polarizations. We derive a general criterion for this behavior that does not require materials with very large indices. We perform numerical studies that illustrate this effect.

Ray and wave chaos in asymmetric resonant optical cavities

Abstract: Optical resonators are essential components of lasers and other wavelength-sensitive optical devices. A resonator is characterized by a set of modes, each with a resonant frequency omega and resonance width Delta omega=1/tau, where tau is the lifetime of a photon in the mode. In a cylindrical or spherical dielectric resonator, extremely long-lived resonances are due to `whispering gallery' modes in which light circulates around the perimeter trapped by total internal reflection. These resonators emit light isotropically. Recently, a new category of asymmetric resonant cavities (ARCs) has been proposed in which substantial shape deformation leads to partially chaotic ray dynamics. This has been predicted to give rise to a universal, frequency-independent broadening of the whispering-gallery resonances, and highly anisotropic emission. Here we present solutions of the wave equation for ARCs which confirm many aspects of the earlier ray-optics model, but also reveal interesting frequency-dependent effects characteristic of quantum chaos. For small deformations the lifetime is controlled by evanescent leakage, the optical analogue of quantum tunneling. We find that the lifetime is much shortened by a process known as `chaos-assisted tunneling'. In contrast, for large deformations (~10%) some resonances are found to have longer lifetimes than predicted by the ray chaos model due to `dynamical localization'.

Simulation of light emission from thin-film microcavities

Abstract: In light-emitting devices based on thin-film technology, light waves that are partially or totally reflected at interfaces between different materials interfere and influence the angular distribution of the emitted light. For an electrical dipole transition, the radiation pattern is equivalent to that of an electrical dipole antenna. New theoretical expressions are provided for the radiation, discriminating for polarization, emission angle, absorption, and transmission; and the numerical calculation of discrete modes, narrow modes, and evanescent waves near absorbing media is discussed.

Method of source terms for dipole emission modification in modes of arbitrary planar structures

Abstract: Modification of dipole emission that is due to its optical environment is calculated for planar layered structures. The layers are optically described by standard matrix techniques, and the dipole is included by using additive source terms for the electric field that depend on dipole orientation and wave polarization. These source terms also allow coupling through evanescent waves. We emphasize the applicability of this method to cases in which the power distribution into various modes is affected: dipole emission into guided modes and emission distribution into the various modes of structures that contain multilayer reflectors, such as microcavities.

Surface light source device of side light type

Abstract: A surface light source device comprises a primary light source, a reflection sheet, a scattering transmission sheet, a guide plate and prism sheet functioning as a light control member. The scattering transmission sheet is provided with scattering power which is given through roughening both faces, uniform containing of fine particles or other means. Light leaked from a back face of the guide plate is reflected and return to the guide plate, being scattered by the scattering transmission sheet on the way. The reflection sheet is a reflection member of high reflectance. A fluorescent lamp emits illumination light which enters into the guide plate and propagates as repeating reflections between the back face and an emission face. Meanwhile, light components having incidence angles smaller than the critical angle with respect to the emission face is emitted from the emission face. The prism sheet and the back face of the guide plate are provided with projections (arrows B, C) which are repeatedly arranged to correct directivity toward the frontal direction in planes parallel and perpendicular with respect to an incidence face of the guide plate. The scattering transmission sheet may be removed, if the reflection sheet is provided with scattering power.

High-order effective-medium theory of subwavelength gratings in classical mounting: application to volume holograms

Abstract: We derive closed-form expressions for the effective index of subwavelength gratings up to the fourth and the second order for TE and TM polarization, respectively. These expressions are valid for arbitrary grating structures and are a generalization of previous results obtained for lamellar gratings with one groove per period (a structure often called a two-component layered medium). The effective-medium-theory predictions are carefully validated with exact electromagnetic theories for slanted and unslanted sinusoidally modulated volume gratings and for classical mounting. It is shown that, even for large period-to-wavelength ratios near the cutoff value, the form birefringence is accurately predicted at any angle of incidence.

Ultraviolet irradiation device of the optical path division type

Abstract: An ultraviolet irradiation device of the optical path division type for treating a workpiece which is often subject to deformations and color changes due to heat, and in which the distribution of radiance is good and the average irradiance on the surface irradiated with light can be increased which can be achieved with light emitted from a rod-shaped lamp and reflected by a trough=shaped cold mirror being incident in cold mirrors which split the optical path. This light is thus divided into two parts and is incident in total reflection mirrors. On the other hand, the direct light emitted by the rod-shaped lamp is incident in second optical path splitting cold mirrors which divides this light and causes it to be incident in the total reflection mirrors. The light reflected by the total reflection mirrors is incident in heat reflection filters, and is transmitted by the heat reflection filters so as to be radiated onto a workpiece. On the workpiece the light divided into two parts is radiated such that the two beams of light come to lie partially superimposed one on top of the other. This improves the radiance distribution. Furthermore, light shielding components can also be used instead of the second optical path splitting mirrors.

Optical switching device and image display device

Abstract: An optical switching device comprises: a light guide including a total reflection plane capable of totally reflecting light thereby transmitting the light; a switching part capable of, at a position where its extraction plane is in close contact with the total reflection plane, capturing evanescent light and reflecting the captured light thereby outputting it; and a driving part for driving the optical switching part. The light guide, the switching part, and the driving part are laminated in this order into a multilayer structure. The employment of the multilayer structure makes it possible to optimize the respective layers independently of one another. The extracted light does not pass through the driving part. This allows the driving part to be optimized so as to achieve an optical switching device capable of operating at a high speed with low power consumption. Thus, it is possible to provide a low-loss and high-contrast optical switching device using an evanescent wave, which can respond at a high speed.

Modal reflectivity in finite-depth two-dimensional photonic-crystal microcavities

Abstract: We present finite-difference time-domain calculations of the Q factor for an optical microcavity defined by a slab waveguide and two-dimensional photonic-crystal end mirrors. The effect of the finite depth of the photonic crystal on the cavity s optical modes is examined. From these calculations, we can optimize the performance of the photonic-crystal mirrors and determine the loss mechanisms within optical cavities defined by these structures. The Q of the cavity modes is shown to be strongly dependent on the depth of the holes defining the photonic crystal, as well as the refractive index of the material surrounding the waveguide core.

Internal wave reflection and mixing at Fieberling Guyot

Abstract: The structure of internal wave reflection off a sloping bottom on the steep flank of a tall North Pacific Ocean seamount is observed in year-long moored array records to differ substantially from the form predicted by linear theory, although linear theory accounts for several qualitative features of the process. This study documents new features of wave reflection as described below. Wave reflection is detectable as far as 750 m above the bottom. Motions are dominated by a single empirical mode whose phase structure obeys linear internal wave dispersion but whose amplitude decays with a scale comparable to the wavenumber. While the dominant mode has scales appropriate to the reflection of a first baroclinic mode wave incident from the open ocean, its decay from the bottom is such that current vectors in the vertical plane rotate clockwise in time when viewed with shallow water to the right. This flow resembles the lower half of the deepest cell pattern predicted by linear reflection from a uniform slope. At the local internal wave critical frequency, the dominant mode has nearly a vanishing wavenumber rather than the infinite wavenumber predicted by linear reflection. Reflected waves are aligned parallel to the bottom slope measured on wave spatial scales, rather than shorter ones. Wave reflection causes large, frequent density overturns, implying mixing. The rate and strength of these overturns imply a local vertical eddy viscosity of 2–6 × 10−4 m2/s over the bottom few hundred meters. The contribution of bottom-intensified mixing to the open deep ocean is roughly equivalent to that found in situ, although reflection from gentler slopes or at lower latitude may produce greater contribution from internal wave-reflection-induced mixing.

Optical switch mechanism

Abstract: An optical switch mechanism for reflecting an input light beam from an input port to a reflection output port in a first state and for transmitting an input light beam to a transmission output port in a second state is disclosed. The switch mechanism comprises a block made of a light transmissive substrate. The block contains a cavity, which is divided by a light transmissive diaphragm into a reflective portion and a transmissive portion. At the input port a light beam is coupled into the block such that the light beam encounters a reflective surface at an angle greater than a critical angle determined by the refractive indices of the substrate and a reflective fluid retained in the reflective portion of the cavity. When the reflective fluid is in contact with the reflective surface the light beam is totally reflected to a reflection output port. Changing hydrostatic pressure moves the transmissive diaphragm into a position where it is in a touching relationship with the reflective surface and the light beam is then transmitted to a transmission output port. The switch mechanism is simple, reliable, fast and easy to manufacture.

Converging device and photovoltaic power generation system utilizing the device

Abstract: PROBLEM TO BE SOLVED: To provide a photovaltaic power generation system utilizing a converging device and capable of improving the efficiency of power generation while reducing installation cost and capable of sufficiently resisting wind pressure even when the system is installed on the roof of a building. SOLUTION: The system is constituted by arranging an optical transmission layer 10 having a rectangular plate-like shape, using its upper surface as a light receiving surface 10a and capable of transmitting solar light downward, a light deflection layer 14 integrally joined with the lower surface of the layer 10 as a rectangular plate which is approximately the same shape as the layer 10 and solar battery cells 18 arranged on both the ends of the layer 10 in the longitudinal direction so that their cell faces are opposed to each other. A sowtooth-like angled face 14a is continuously formed on the lower surface of the layer 14 in its longitudinal direction and a light reflection film 16 is formed on the whole area of the angle face 14a. Solar light transmitted from the face 10a through the layer 10 and fully reflected on the film 16 is made incident on the layer 10 again at an incident angle less than a critical angle, propagated through the layer 10 while repeating refraction and reflection in the layer 10 and made incident upon the cell 18.

Quasi-phase-matched second-harmonic generation by use of a total-internal-reflection phase shift in gallium arsenide and zinc selenide plates.

Abstract: We fabricated a novel quasi-phase-matched frequency converter, using a zigzag optical beam path in a thin, polished parallel plate. Second-harmonic generation experiments demonstrated angle-tuned output at 4.6 to 5.3 µm in GaAs and 1.7 to 2.0 µm in ZnSe crystals when pulsed infrared laser sources were used.

Transmission-type screen

Abstract: PROBLEM TO BE SOLVED: To provide a transmission type screen preventing the deterioration of contrast due to external light rays such as indoor illumination. SOLUTION: The transmission type screen comprises a Fresnel lens sheet formed with a Fresnel lens element on the surface of observer side and a light shielding sheet 13 arranged on the observer side of the Fresnel lens sheet. Light shielding elements 22 absorbing the external light ray which undergoes total reflection on the surface of projection light source side of the Fresnel lens sheet among the external light rays 2 made incident from the observer side and exits the light rays to the observer side are formed on the light shielding sheet 13 and, thereby, the deterioration of contrast due to external light rays is prevented. Therein, it is preferable that the light shielding elements transmit the external light rays transmitted/reflected in the light shielding sheet at an angle θ which satisfies at least θ COPYRIGHT: (C)2005,JPO&NCIPI

Optical switching element and image display device

Abstract: The present invention provides an optical switching element causing less loss of light and permitting high response, thinning of an optical system for illumination, and the realization of an image display device exhibiting precise grayscale properties. In the optical switching element, an extraction surface of a light extraction unit mounted to a thin film is brought into contact with the total reflection surface of a light guide serving as a light guide unit comprising a glass plate or the like for transmitting light by total reflection, or near at a distance from the total reflection, surface for allowing extraction of evanescent waves, to extract the incident light transmitted through the light guide and emit the extracted light to the outside through an emission member. Such optical switching permits the light extract unit to be operated in a range of approximately a wavelength or half a wavelength, thereby providing an optical switching element capable of high-speed operation and having high contrast because the incident light does not leak due to total reflection during an off time.

Double-cone internal reflection as a basis for polarization detection in fish

Abstract: Some species of fish are able to discriminate, in addition to intensity and wavelength (color), the direction of polarization of visible light. Optical experiments on axially oriented retinal cones from trout and sunfish with use of two types of polarization microscope indicate anisotropic light transmission through paired cones. The measured linear birefringence of paired cone ellipsoids is consistent with the presence of membranous partitions. It is proposed that the partition between the two members of a paired cone, which often appears extensive and flat, functions as a dielectric mirror and that polarization-dependent reflection and refraction at this partition constitutes the underlying mechanism in the transduction of polarization into intensity variation at the photoreceptor’s outer segments. We support this hypothesis with linear birefringence and linear dichroism measurements, histological evidence, large-scale optical model measurements, and theoretical calculations based on Fresnel’s formulas.

Electrophoretic, dual refraction frustration of total internal reflection in high efficiency variable reflectivity image displays

Abstract: A display device and method in which electrophoresis and/or dual prismatic surfaces are used to controllably frustrate total internal reflection at an interface between materials having different refractive indices. In one embodiment, an array of solid dielectric light fibers is surrounded by an electrophoretic medium such as acetonitrile. In the absence of electrophoretic activity, the fibers totally internally reflect light which passes into the fibers, and a reflector returns the light for diffuse emission through the fibers ends. If the fibers are subjected to electrophoretic activity their TIR capability is frustrated. A second embodiment redirects light through two prismatic surfaces in a manner which permits the TIR phenomenon to occur and to be controlled at a flat surface. A third embodiment uses both electrophoresis and dual prismatic surfaces to achieve gapless control of the TIR phenomenon at a flat surface.

Interferometer for small-angle measurement based on total internal reflection

Abstract: We describe a new method for angle measurement based on the internal-reflection effect and heterodyne interferometry. A novel prism assembly is designed that can always parallel retroreflect the incoming light beams so the optical configuration is compact. As a differential common-path optical configuration is integrated into the design, the linearity of the method is greatly improved. Details of theoretical analysis of the method and experimental verification of the principle are presented. The resolution can be better than 0.3 arc sec. The experimental results and further improvements of the proposed method are also addressed.

Total internal reflection fluorescence correlation spectroscopy for counting molecules at solid/liquid interfaces.

Abstract: Fluorescence correlation spectroscopy, using tota internal reflection excitation (TIRFCS), is developed as a method to allow quantitative determination of molecular populations at solid/liquid interfaces. Population fluctuations of fluorescent molecules at the interface are observed as excess low-frequency noise on a fluorescence signal. Since the noise arises from molecular origins, its magnitude can be evaluated by Poisson statistics to determine the number of molecules in the interface volume. This quantitative information is available without sensitivity calibration or the preparation of standards and without fitting the transients to a kinetic model. Unlike single-molecule counting measurements, TIRFCS can produce these quantitative results even when the number of photoelectrons detected per molecule is small. Surface populations of rhodamine 6G dye molecules were measured at C-18-derivatized, flat silica surfaces in contact with aqueous solutions and compared with predicted values derived from chrom...

Effects of attenuation and anisotropy on reflection amplitude versus offset

Abstract: To investigate the effects that attenuation and anisotropy have on reflection coefficients, we consider a homogeneous and viscoelastic wave incident on an interface between two transversely isotropic and lossy media with the symmetry axis perpendicular to the interface. Analysis of PP and PS reflection coefficients shows that anisotropy should be taken into account in amplitude variation with offset (AVO) studies involving shales. Different anisotropic characteristics may reverse the reflection trend and substantially influence the position of the critical angle versus offset. The analysis of a shale-chalk interface indicates that when the critical distance is close to the near offsets, the AVO response is substantially affected by the presence of dissipation. In a second example, we compute reflection coefficients and synthetic seismograms for a limestone/black shale interface with different rheological properties of the underlying shale. This case shows reversal of the reflection trend with increasing offset and compensation between the anisotropic and anelastic effects.

Phase diagram for avalanche stratification of granular media

Abstract: When a binary mixture of granular materials is poured into a quasi-two-dimensional Hele-Shaw cell, alternating stratified layers of large and small particles are formed along the top surface. This effect is studied as the plate separation of the cell and the flow rate at which the granular mixture is poured are systematically varied. A nontrivial ``phase diagram'' is found, with pairing of the stratification layers occurring for a finite range of plate separation and flow rate values. Numerical simulations based upon a model involving periodic avalanching of a metastable wedge of granular material above the critical angle of repose reproduce both the observed stratification pattern and the flow rate dependence.

Evanescent Bessel beams

Abstract: Bessel beams of the evanescent kind are presented and analyzed. They rapidly decay with propagation but retain their original transversal shape. A physical method of generation is proposed in the form of propagation of an ordinary (nonevanescent) Bessel beam across an interface between two different dielectric media. Transmission and reflection coefficients are calculated for this type of beam. The analysis is vectorial and is fully consistent with Maxwell’s equations. Apodized beams of Gauss–Bessel and Circ–Bessel types are propagated by numerical simulation and are shown also to retain a narrow central lobe. Beams of these types have evident advantages in near-field applications, microscopy, and high-density data storage with subwavelength resolution.

Influence of detection conditions on near-field optical imaging

Abstract: The process of image formation in transmission mode scanning near-field optical microscopy is analyzed both theoretically and experimentally. Changes in the dielectric and topographic properties of the sample influence not only the total transmitted intensity, but also its angular distribution in the far field. This opens up an additional source of optical information about the sample. Some of this additional information is retrieved by separate but simultaneous detection of the radiation emitted at angles smaller (allowed light) and larger (forbidden light) than the critical angle of total internal reflection, respectively. Different experimental setups and their respective advantages are discussed. High resolution, constant height mode optical images of test structures are compared with theoretical predictions. Forbidden-light optical images frequently provide enhanced resolution and/or contrast as compared to allowed light images. For small phase objects, in contrast to amplitude objects, a contrast reversal between forbidden and allowed light images is observed.

Imaging ATR spectrometer

Abstract: Method and apparatus for providing an imaging attenuated total reflection (ATR) spectrometer which provides faster measurement speed and better spatial resolution than systems collecting an equivalent amount of data using conventional, non-imaging ATR methods and systems. Apparatus includes a radiation source, an interferometer coupled to the radiation source which produces a spectrally-multiplexed input beam of radiation, an internal reflection element (IRE) engaging a sample-under-test, a focal plane array detector, a first optical system adapted and positioned to direct and concentrate the input beam through the rear surface of the IRE towards a contact area of the sample such that an angle of incidence of said input beam at the front surface is equal to or greater than the critical angle for the IRE, and a second optical system adapted and positioned to collect reflected radiation from the contact area and image the same onto the focal plane array detector.

Total internal reflection electromagnetic radiation beam entry to, and exit from, ellipsometer, polarimeter, reflectometer and the like systems

Abstract: Disclosed are laterally compact ellipsometer, polarimeter, reflectometer and the like material system investigating systems, and methods for their use. Input and output optical elements effect changes in orientation, (propagation direction), of a beam of electromagnetic radiation caused to pass therethrough by an essentially total internal reflection therein. In addition, a propagation direction diverted beam of electromagnetic radiation can be simultaneously, optionally, caused to have a phase retardation entered between orthogonal polarization components thereof by at least one of the input and output optical elements. The present invention enables relatively simple investigation of a sample system with a polarized beam of electromagnetic radiation which impinges thereupon at a less than Brewster Angle, small "spot" size effecting angle-of-incidence, with respect to a normal to a surface of an investigated material system.

A compact, scalable cross-connect switch using total internal reflection due to thermally-generated bubbles

Abstract: The authors present a novel, compact single mode fiber cross-connect switch which diverts light from one waveguide to a crossing waveguide in a silica planar lightwave circuit (PLC) using total internal reflection (TIR) off the interface between a waveguide and a thermally-generated bubble.

A Comparison of Fluorescence Inner-Filter Effects for Different Cell Configurations

Abstract: In conventional fluorescence spectroscopy, fluorescence intensity at high fluorophore concentration is often not proportional to fluorophore concentration, owing to primary and secondary absorption (inner-filter effects). In this paper, fluorescence calibration curves for anthracene solutions were obtained using a conventional right angle cell, a frontal reflection cell, a short pass cell, and a total internal reflection fluorescence (TIRF) cell for comparing the observed primary inner-filter effects. Measurements were also made of a two-component mixture using the nonfluorescent 9-nitrofluorene with anthracene for comparing primary and secondary inner-filter effects. A conventional right angle cell exhibited the widest linear dynamic range and lowest detectable anthracene concentration, whereas the TIRF cell provided the best linearity at high concentrations. The TIRF cell was determined to have significant potential for quantitative analysis of highly concentrated and/or turbid solutions.

Element and apparatus for attenuated total reflection measurement, and method for measuring specific component using the same

Abstract: An improved attenuated total reflection (ATR) element and the measurement apparatus employing the element capable of performing a measurement with a high accuracy at a low operating cost is disclosed. An ATR element of the present invention permits an incident beam to have an internal total reflection at the surface, and comprises a projection protruded at the portion where the incident beam has the internal total reflection.

Polarization effects in the optical interaction between a nanoparticle and a corrugated surface: implications for apertureless near-field microscopy

Abstract: We put forward rigorous two-dimensional numerical calculations of the electromagnetic interaction between a nanometric tip and a corrugated dielectric interface when the tip scans the surface at nanometric distance. The surface is illuminated from its dielectric side by a p-polarized wave at normal incidence or under total internal reflection. Large tip–substrate optical interactions appear for small distances between these two bodies. The far-field images produced by recording the intensity scattered by either the tip or the sample are analyzed in terms of several experimental parameters, namely, the angles of incidence and observation, the dielectric permittivities of the tip and the surface, and the tip–sample distance. The influence of the component of the electric field normal to the surface is discussed. The role of periodic modulation of the vertical position of the tip is also investigated.

High-quality Brewster’s angle polarizer for broadband infrared application

Abstract: We have designed and constructed a linear polarizer for use with visible and infrared radiation. The broadband polarizer consists of four germanium plates arranged in a chevron geometry. Input radiation is incident near Brewster’s angle for the first plate such that the reflected beam is preferentially s-wave polarized. This reflected beam is steered subsequently to the successive plates, always intersecting near Brewster’s angle. The beam polarization at the output of the device is almost completely s-wave polarized. The ratio of the paraxial flux of the nearly extinguished p-wave polarized light to the s-wave polarized light transmitted through the device is found to be less than 10-5 for laser illumination at wavelengths of 0.633, 1.32, 3.39, and 10.6 μm. Calculations predict that extinction ratios less than 10-5 are achievable over the wavelength range from 0.4 μm to beyond 500 μm. Alternative design geometries involving fewer plates are also described along with their advantages and disadvantages.