Showing papers on "Total internal reflection published in 2002"

Goos-Hänchen shift in negatively refractive media

Abstract: The Goos-Hanchen shift is calculated when total internal reflection occurs at an interface between "normal" and negatively refractive media. The shift is negative, consistent with the direction of energy flow in the negatively refractive medium.

Large and negative Goos–Hänchen shift near the Brewster dip on reflection from weakly absorbing media

Abstract: Applying Artmann's formula to a light beam in the TM state of wave polarization, we show analytically the existence of a large and negative Goos-Hanchen shift near the angle of the Brewster dip on reflection from a weakly absorbing semi-infinite medium. The shift is opposite that in the case of total internal reflection, and it can be an order of magnitude larger than a wavelength if the absorption of the reflecting medium is sufficiently weak. Examples are given, and the detectibility of the shift is discussed.

Lens with refractive and reflective surfaces

Abstract: A lens mounted to a light emitting diode package internally redirects light within the lens so that a majority of light is emitted from the lens approximately perpendicular to a package axis of the light emitting diode package. In one embodiment, the light emitted by the light emitting diode package is refracted by a sawtooth portion of the lens and reflected by a total internal reflection portion of the lens.

Waves in the Magnetized Solar Atmosphere. I. Basic Processes and Internetwork Oscillations

Abstract: We have modeled numerically the propagation of waves through magnetic structures in a stratified atmosphere. We first simulate the propagation of waves through a number of simple, exemplary field geometries in order to obtain a better insight into the effect of differing field structures on the wave speeds, amplitudes, polarizations, direction of propagation, etc., with a view to understanding the wide variety of wavelike and oscillatory processes observed in the solar atmosphere. As a particular example, we then apply the method to oscillations in the chromospheric network and internetwork. We find that in regions where the field is significantly inclined to the vertical, refraction by the rapidly increasing phase speed of the fast modes results in total internal reflection of the waves at a surface whose altitude is highly variable. We conjecture a relationship between this phenomenon and the observed spatiotemporal intermittancy of the oscillations. By contrast, in regions where the field is close to vertical, the waves continue to propagate upward, channeled along the field lines but otherwise largely unaffected by the field.

Highly efficient LED lamp

Abstract: A highly efficient LED lamp includes an optical module and a housing. The optical module has at least one light emitting diode (LED) that emits light with a wide divergence, a non-imaging optical (NIO) element and a transparent window. The NIO element includes a refractive member located around a LED optical axis and a total internal reflection member located around the refractive member. The refractive member and the total internal reflection member are integrated in a single transparent element having a mutual focal point, wherein the NIO element collects a significant amount of light emitted by the LED with wide divergence located at the focal point, to compress the collected light with high efficiency into a beam with a generally different angular spread in a horizontal plane and a vertical plane and to direct the compressed light outside of the lamp.

Fresnel Filtering in Lasing Emission from Scarred Modes of Wave-Chaotic Optical Resonators

Abstract: We study lasing emission from asymmetric resonant cavity GaN microlasers. By comparing far-field intensity patterns with images of the microlaser we find that the lasing modes are concentrated on three-bounce unstable periodic ray orbits; i.e., the modes are scarred. The high-intensity emission directions of these scarred modes are completely different from those predicted by applying Snell's law to the ray orbit. This effect is due to the process of "Fresnel filtering" which occurs when a beam of finite angular spread is incident at the critical angle for total internal reflection.

Prism optical element, image observation apparatus and image display apparatus

Abstract: An extremely compact prism optical element, image observation apparatus and image display apparatus which are capable of providing an observation image that is clear and has minimal aberration and minimal distortion even at a wide field angle. Light rays emitted from an image display device (7) enter an ocular optical system (12) through a fourth surface (6) and are totally reflected toward an observer's pupil (1) by a third surface (5). The reflected light rays are reflected by a first surface (3) disposed immediately in front of the observer's pupil (1) and then reflected toward the observer's pupil (1) by a second surface (4). The reflected light rays pass through the first surface (3) and are projected into an observer's eyeball (15) with the observer's iris position as an exit pupil (1). When an external-scene image is observed, light rays from an object point in the external scene enter the ocular optical system (12) through the third surface (5), pass through the first surface (3) and are projected into the observer's eyeball (15). Assuming that the angle of internal reflection of an arbitrary light ray at the third surface (5) is θr3, the ocular optical system (12) satisfies the condition of sin−1(1/nd)≦θr3 ≦60°, where nd is the refractive index for the spectral d-line of the medium of the ocular optical system (12).

Polyimide-waveguide-based thermal optical switch using total-internal-reflection effect

Abstract: A total-internal-reflection waveguide switch with an X junction was designed and fabricated by using the thermo-optic effect of polyimide materials. Experimental results show that the crosstalk is below −28 dB at the wavelength of 1.55 μm. The switching power with the current electrode is 132 mW, which can be reduced to 20–30 mW with an optimized design together with electroplating to form a thick conducting path.

Optical switching by controllable frustration of total internal reflection

Abstract: An optical switch for controllably switching an interface between a reflective state in which incident light undergoes total internal reflection and a non-reflective state in which total internal reflection is prevented. In one such switch a cell contains a fluid. One side of the cell forms the light incident interface. A membrane is suspended in the fluid. One pair of electrodes is applied to opposite sides of the membrane. Another electrode pair is applied to the cell's interface side and to the cell's opposite side. A variable voltage potential is applied between selected ones of the electrodes. Application of the voltage potential between selected ones of the membrane and cell electrodes moves the membrane into optical contact with the interface, producing the non-reflective state. Application of the voltage potential between other selected ones of the membrane and cell electrodes moves the membrane away from optical contact with the interface, producing the reflective state.

Light-modulating element, display element, and exposure element

Abstract: Subjects for the invention are to provide a light-modulating element having an elevated energy efficiency while preventing a decrease in contrast at low cost without using a display technique employing a waveguide or lightguide plate, and to provide a display element capable of producing high-quality display images and an exposure element capable of exposure treatment. In the invention, the light-modulating element comprises: a total-reflection optical member 2 having such a property that at least part of planar incident light introduced into the light-modulating element is totally reflected at an interface (total reflection plane) 22 of a layer constituted by the light-modulating element and the incident light does not substantially go out through the side opposite to the incident-light introduction side; and light-coupling elements 6 which are disposed on the total reflection plane 22 side of the total-reflection optical member 2 and serve to selectively couple with the incident light and take out the same from the total reflection plane 22.

Influence of refractive index matching on the photon diffuse reflectance

Abstract: Photon migration in a randomly inhomogeneous, highly scattering and absorbing semi-infinite medium with a plane boundary is considered by a Monte Carlo (MC) technique. The employed MC technique combines the statistical weight scheme and real photon paths simulation, allowing the exclusion of the energy conservation problem. The internal reflection of the scattered radiation on the medium interface is taken into account by allowing the trajectories of photon packets to be split into reflected and transmitted parts. The spatial photon sensitivity profile (SPSP), spatially resolved diffuse reflectance and angular and spatial photon detector weight distributions are considered in terms of Fresnel's reflection/refraction on the boundary of the medium. The effect of the refractive index match is predicted correctly by the MC method and by the diffusion approximation. The results demonstrate that matching of the refractive index of the medium significantly improves the contrast and spatial resolution of the spatial photon sensitivity profile (SPSP). The results of simulation of the spatially resolved diffuse reflectance agree well with the results predicted by the diffusion approximation and the experimental results reported earlier.

Surface-mounted devices of light-emitting diodes with small lens

Abstract: The present invention is a surface-mounted device of light-emitting diodes (SMD LED) whose component typically has a plane on the surface Through the calculation of Snell's Law, most of light fails to be emitted directly from the component because of the difference in the refractive index of the epoxy resin and the atmosphere (the refractive index of the light in the atmosphere is 1, the refractive index of the epoxy resin is around 15) It takes several times of refraction and a waste of brightness to allow the light that fails to be emitted directly a chance to be emitted, while leaving some light that might never be emitted Therefore, the brightness reduces The surface-mounted devices of light-emitting diodes with small lens for the present invention attach several small lens or diffraction lens on the plane surface of the SMD LED The lens that enlarges the critical angle increases the direct light-emitting opportunity from the light-emitting chip, which in turn increases the brightness of LED Besides, the plane surface of the component under the vision of naked eyes wards off the influence on the pick and place operation, while prevents the volume of the component from getting large

Large eddy simulation of an Ahmed reference model

Abstract: This paper presents the first large eddy simulation (LES) of the Ahmed reference model. LES allows a much greater depth of analysis than most other turbulent simulation methods. Here the richness of information provided by LES is used to show a wide range of flow results such as: time averaged mean profiles, time-dependent traces, flow spectra and a number of two-dimensional and three-dimensional animations of the flowfield. The body geometry is analysed at a given slant angle of 28° using the PRICELES/TRIO_U code platform. This angle is chosen as it is close to the critical angle at which the flow changes between two different regimes. A non-structured tetrahedral grid is used which enables accurate modelling of the body geometry while avoiding the need for a prohibitively expensive mesh. The drag estimation and flow field visualizations indicate that the flow is in the regime corresponding to angles above the critical angle, although the geometry is just below the critical angle. The simulation revealed...

The role of surface-induced ordering in the crystallisation of PET films

Abstract: The molecular configuration and long-range order at the surface of spin-cast poly(ethylene terephthalate) (PET) thin films spin-cast onto an etched Si(001) surface during crystallisation from the amorphous state has been investigated for a range of annealing temperatures. The structural ordering at the surface of the film was compared directly with that in the bulk of the film by employing grazing-incidence X-ray diffraction with incident angles below, at and above the critical angle for total reflection. Ordering was observed at the surface at annealing temperatures of 80–95°C, lower than that in the bulk, involving local parallel alignment of chains in the plane of the surface with the benzene rings oriented preferentially with the ring plane parallel to the surface. Comparison with atomic-force microscopy images enables the fold configuration at the surface to be deduced.

Simple technique for measuring the Goos–Hänchen effect with polarization modulation and a position-sensitive detector

Abstract: An original approach to directly measuring the Goos-Hanchen longitudinal shift between TE and TM polarization states during a total internal reflection is introduced. The technique is based on the modulation of the polarization state of a laser by an electro-optic modulator combined with a precise measurement of the resulting spatial displacement with a position-sensitive detector. This method presents many advantages over other techniques and allows measurements at different wavelengths over a broad range for the incident angle.

Single optical element LED signal

Abstract: An LED signal using a single optical element. The single optical element designed with a generally smooth outer surface and an inner surface having Fresnel optical elements in an inner center region and total internal reflection elements in an outer periphery region. The single optical element may have an integral sealing surface for sealable connection to the signal housing and no countersinking so that it is capable of manufacture by injection molding.

Deviation from Snell's law for beams transmitted near the critical angle: application to microcavity lasers

Abstract: We show that when a narrow beam is incident upon a dielectric interface near the critical angle for total internal reflection it will be transmitted into the far field with an angular deflection from the direction predicted by Snell's law, because of a phenomenon that we call "Fresnel filtering" This effect can be quite large for the parameter range that is relevant to dielectric microcavity lasers

Total reflection X-ray fluorescence analysis

Abstract: The radical principle, equipment and peculiarity of total reflection X ray fluorescence are summarized. Application and perspective of tatal reflection X ray fluorescence are recommended.

Photocurrent Enhancement for Polymer Langmuir−Blodgett Monolayers Containing Ruthenium Complex by Surface Plasmon Resonance

Abstract: This paper describes effective photocurrent generation based on a polymer Langmuir−Blodgett (LB) monolayer containing ruthenium complex on a silver electrode excited by surface plasmon resonance (SPR). It was found that photocurrent generation is greatly enhanced at an incident angle where the electromagnetic field was most enhanced by SPR. At this angle, the photocurrent is enhanced by a factor of 23.6 compared with that at the critical angle for total internal reflection. The incident monochromatic photon-to-current conversion efficiency was 9.53 × 10-3%, higher than that of the corresponding polymer LB monolayer film on a transparent indium tin oxide electrode with conventional direct transmitted light (2.87 × 10-3%). Furthermore, it was demonstrated that precoating with poly(N-dodecylacrylamide) homopolymer ensures adequate separation of the Ru(bpy)32+ and silver surface, thereby suppressing the quenching of photoexcited Ru(bpy)32+ by the silver. Controlling the distance between the Ru(bpy)32+ layer a...

Solid State Light Source Fabricated with YAG:Ce Single Crystal

Abstract: A solid state, yellow-white emitting light source has been manufactured employing a YAG:Ce single crystal as a wavelength conversion material to analyze the conversion process quantitatively and also to explore the ultimate limit of the conversion efficiency. Excitation polarized coherent blue light is incident on to the crystal at the Brewster angle and is multiply reflected inside the crystal with internal total reflection. The generated light is shown to be efficiently extracted by providing a light guide with a suitable shape at the front surface of the crystal.

Surface light device, image display device and light guide plate

Abstract: An LED (5) as a light source is disposed so as to face the incident surface (4) of a light guide plate (3), a light from this LED (5) is incident into the light guide plate (3) from the incident surface (4) of the plate (3) and then propagates through the inside of the plate (3), and the light, having its incident angle with respect to an outgoing surface (6) changed to up to a critical angle during this propagation process, is output from the outgoing surface (6) of the plate (3). In addition, many prism projections (12) extending in a direction away from the vicinity of the incident surface (4) are formed in parallel on at least one of the outgoing surface (6) of the plate (3) and a surface (10) opposite to the former surface. The side-surface side portions (10b) of the prism projections (12) are so formed as to gradually reduce the heights of the projections toward the incident surface (4). Such arrangements restrict an abnormal light emission in the vicinity of the incident surface of the light guide plate and make uniform an output light luminance even when an LED is used as a light source.

Apparatus and method for total internal reflection spectroscopy

Abstract: An optical apparatus for total internal reflection spectroscopy comprises: a transparent body having an internally reflective surface; at least one source of electromagnetic radiation for providing at least one beam of collimated electromagnetic radiation; optical scanning means for directing the beam or beams to the transparent body so that the radiation is internally reflected at the reflective surface, and sequentially or continuously scanning the incident angle of the radiation over an angular range; at least one detector for detecting electromagnetic radiation exiting the transparent body, and means for counteracting variation of the irradiance in the illuminated area of the surface during the angular scan, or the effect of such variation on the reflected beam or beams. An optical apparatus for examining thin layer structures on a surface for differences in respect of optical thickness and/or refractive index, and a method for total internal reflection spectroscopy are also disclosed.

Optical properties of a total-reflection-type one-dimensional photonic crystal

Abstract: We produced an asymmetric Fabry-Perot microcavity using total reflection, and its optical properties were investigated. The structure is considered to be a total-reflection-type 1-D photonic crystal. An electric-field enhancement of incident light in a defect layer installed inside the photonic crystal was observed by fluorescence emission from dye molecules doped into the defect layer division. We confirmed that the incident light intensity was strengthened by about 63 times in the defect layer.

High Fidelity Surface Chemical Imaging at 1000 nm Levels: Internal Reflection IR Imaging (IRIRI) Approach

Abstract: This report presents how combination of internal reflection (IR) and infrared imaging (IRI) can reach a surface spatial resolution at 1000 nm levels in the middle infrared range. As a result, vibrational spectra from these size areas can be recorded at high signal-to-noise levels. A spatial calibration of this method was performed by correlating IRIRI data with SEM micrographs and optical images of geometrically well-defined polymeric photoresists as well as Nylon fibers imbedded into a polyester matrix. The IRIRI approach has the potential of obtaining even better surface spatial resolution of vibrational spectra when internal reflection elements with greater refractive index ratios in the middle IR range become available.

Planar display device and its driving method

Abstract: PROBLEM TO BE SOLVED: To provide a thin display device that has high resolution and high light utilization efficiency, that is inexpensive and drivable at high speed, and that is therefore free from flicker. SOLUTION: The display element is composed of: a light source 4 of a plurality of different wavelengths (blue, green, red) each being independently controllable; and a two-dimensional optical modulation array (optical coupling element 6 and total reflection optical member 2) that electro-mechanically controls transmittance of light from the light source. The light source is time-sequentially turned on within one field period and, synchronously with it, the two-dimensional optical modulation array is driven for optical modulation. COPYRIGHT: (C)2004,JPO&NCIPI

Omnidirectional elastic band gap in finite lamellar structures.

Abstract: This paper presents a comprehensive theoretical analysis of the occurrence of omnidirectional reflection in one-dimensional phononic crystal structures. We discuss the conditions for a one-dimensional layered structure, made of elastic materials, to exhibit total reflection of acoustic incident waves in a given frequency range, for all incident angles and all polarizations. The property of omnidirectional reflection can be fulfilled with a simple finite superlattice if the substrate from which the incident waves are launched is made of a material with high acoustic velocities (this is very similar to the case of omnidirectional optical mirror where the incident light is generated in vacuum). However, if the substrate is made of a material with low acoustic velocities, we propose two solutions to obtain an omnidirectional band gap, namely, the cladding of a superlattice with a layer of high acoustic velocities, which acts like a barrier for the propagation of phonons, or the association in tandem of two different superlattices in such a way that the superposition of their band structures exhibits an absolute acoustic band gap. We discuss the appropriate choices of the material and geometrical properties to realize such structures. The behavior of the transmission coefficients are discussed in relation with the dispersion curves of the finite structure embedded between two substrates. Both transmission coefficients and densities of states (from which we derive the dispersion curves) are calculated in the framework of a Green's function method.

Optical configuration and method for differential refractive index measurements

Abstract: An optical configuration for measuring a difference in refractive index between a first sample and a second sample comprises partitioned first and second optical interfaces symmetrically illuminated by an illumination beam to provide first and second partial beams defined by the refractive index of the first and second samples, respectively. A linear scanned array is aligned in a meridional plane of the optical configuration for detection purposes, and an optical multiplexor is provided upstream of the linear scanned array for receiving the first and second partial beams and defining first and second optical channels carrying optical signal information corresponding to the first and second partial beams. The optical multiplexor switches between optical channels, such that the linear scanned array detects either the first or second optical channel at a given time. Thus, differential measurements are possible using a single linear array. Embodiments for critical angle and surface plasmon resonance refractive index measurements are disclosed. The disclosure also relates to methods for measuring a difference in refractive index between a first sample and a second sample in accordance with the described optical configuration embodiments.

Image sensing apparatus

Abstract: An image detecting device according to the invention is provided with an optical fiber array substrate 101 , a circuit conductor layer 109 over it, an image sensor 106 arranged over the circuit conductor layer, first illuminating means 104 arranged so that the angle of incidence on the plane of incidence of the optical fiber be made greater than the critical angle and the direction of lights reflected by the plane of incidence relative to the direction of the optical axis of the optical fibers be made not greater than the critical angle of total reflection inside the optical fiber, second illuminating means 105 arranged so that the angle of incidence on the plane of incidence of the optical fiber be made smaller than the critical angle and the direction of lights reflected by the plane of incidence relative to the direction of the optical axis of the optical fibers be made not smaller than the critical angle of total reflection inside the optical fibers, and control means 110 which performs control for turning on or off each illuminating means, wherein the direction of the optical axes of the optical fibers is arranged with an inclination at a prescribed angle to the normal to said main face of said optical fiber array substrate.

On-chip absorption measurements using an integrated waveguide

Abstract: Square hollow waveguides are used to integrate measurement of absorption with chip-based electrophoresis. The 50×50 µm liquid channel and 50×50 µm waveguide are etched as a negative pattern into a silicon master and replicated as a positive in poly-dimethylsiloxane (PDMS). The uniform refractive index of the chip prevents guiding by total internal reflection. Instead, light at 488 nm is guided by reflection at the air-PDMS interface. The waveguide has a 60% efficiency over a distance of 3.2 cm. Separation of fluorescein and the dye BODIPY is demonstrated. A detection limit (S/N=3) of 200 µM fluorescein is obtained using a 50 µm pathlength and a simple photocell detector.

Grazing-incidence X-ray Absorption and Emission Spectroscopy

Abstract: ### Grazing-incidence X-ray methods Although the advantages of using grazing incidence (GI) techniques in X-ray scattering and spectroscopy have been known for a long time (Yoneda and Horiuchi 1971), the use of such geometry has only been developed fully with the advent of highly collimated X-ray sources, particularly synchrotrons. It is now possible to place the entire output of a synchrotron insertion device (wiggler or undulator) onto the surface of a flat crystal or analogous sample with minimal angular divergence at the critical angle for total external reflection. This allows the application of unprecedented X-ray intensity in a region confined within a few nm of the surface. Such intensity allows for measurement of the X-ray absorption and emission spectrum with sufficient counting statistics so that extremely small surface coverages of impurities, precipitates or sorbed species can be structurally probed. This is of value to environmental geochemistry, as the majority of toxic pollutants in the environment do not occupy mineral surfaces with anything like monolayer (ML) coverages. Hence the majority of X-ray experiments to date deal with unrealistically high surface loadings, relatively thick surface precipitates, or natural samples with high levels of contaminants. This is of special significance because small quantities of surface complexes may bind to defect or otherwise unrepresentative low density sites on a surface, and hence would not behave like species sorbed at higher densities. In addition, the use of single crystal samples allows the polarization of the synchrotron radiation to be used to probe specific directions with respect to the surface plane (for K and L1 edges), hence potentially obtaining additional crystallographic information about oriented adsorbates, precipitates or epitaxial layers. One can select the type of substrate, the plane (hkl) of the substrate, and the orientation of that plane with respect to the propagation direction and electric vector polarization of …