Showing papers on "Total internal reflection published in 1969"

Dielectric rectangular waveguide and directional coupler for integrated optics

Abstract: We study the transmission properties of a guide consisting of a dielectric rod with rectangular cross section, surrounded by several dielectrics of smaller refractive indices. This guide is suitable for integrated optical circuitry because of its size, single-mode operation, mechanical stability, simplicity, and precise construction. After making some simplifying assumptions, we solve Maxwell's equations in closed form and find, that, because of total internal reflection, the guide supports two types of hybrid modes which are essentially of the TEM kind polarized at right angles. Their attenuations are comparable to that of a plane wave traveling in the material of which the rod is made. If the refractive indexes are chosen properly, the guide can support only the fundamental modes of each family with any aspect ratio of the guide cross section. By adding thin lossy layers, the guide presents higher loss to one of those modes. As an alternative, the guide can be made to support only one of the modes if part of the surrounding dielectrics is made a low impedance medium. Finally, we determine the coupling between parallel guiding rods of slightly different sizes and dielectrics; at wavelengths around one micron, 3-dB directional couplers, a few hundred microns long, can be achieved with separations of the guides about the same as their widths (a few microns).

High‐Frequency Scattering by a Transparent Sphere. I. Direct Reflection and Transmission

Abstract: This is Paper I of a series on high‐frequency scattering of a scalar plane wave by a transparent sphere (square potential well or barrier). It is assumed that (ka)⅓≫1,|N−1|½(ka)⅓≫1, where k is the wave‐number, a is the radius of the sphere, and N is the refractive index. By applying the modified Watson transformation, previously employed for an impenetrable sphere, the asymptotic behavior of the exact scattering amplitude in any direction is obtained, including several angular regions not treated before. The distribution of Regge poles is determined and their physical interpretation is given. The results are helpful in explaining the reason for the difference in the analytic properties of scattering amplitudes for cutoff potentials and potentials with tails. Following Debye, the scattering amplitude is expanded in a series, corresponding to a description in terms of multiple internal reflections. In Paper I, the first term of the Debye expansion, associated with direct reflection from the surface, and the second term, associated with direct transmission (without any internal reflection), are treated, both for N > 1 and for N 1, the behavior of the first term is similar to that found for an impenetrable sphere, with a forward diffraction peak, a lit (geometrical reflection) region, and a transition region where the amplitude is reduced to generalized Fock functions. For N 1 and for N < 1. In the former case, surface waves make shortcuts across the sphere, by critical refraction. In the latter one, they excite new surface waves by internal diffraction.

Surface roughening of electroluminescent diodes

Abstract: THE EMISSION OF LIGHT FROM A HIGH INDEX OF REFRACTION ELECTROLUMINESCENT BODY IS LIMITED BY THE PHENOMENON OF TOTAL INTERNAL REFLECTION. IT HAS BEEN FOUND THAT, FOR DEVICES OF THOSE MATERIALS WHICH ARE TRANSPARENT TO THEIR OWN RADIATION, SUCH AS GAP, THE EMISSION FROM A SURFACE CAN BE SIGNIFICANTLY INCREASED BY MAKING THAT SURFACE ROUGH. ALSO, THE SPACIAL DISTRIBUTION OF THE EMITTED LIGHT CAN BE INFLUENCED BY THE SELECTION OF ROUGH AND SMOOTH SURFACES. CHEMICAL AND ALTERNATIVE MECHANICAL ROUGHENING PROCESSES ARE DISCLOSED.

Electro-luminescent device

Abstract: Increased light output results from certain design modifications in a GaAs infrared emitting diode coated with a phosphor for converting this emission to visible light. These design modifications include shape and dimensional considerations for minimizing internal reflection and absorption of infrared emission within the diode as well as dimensional and compositional considerations as applied to the coating for reducing scattering losses and minimizing internal reflection of its emission.

Reflection and Transmission of Light by Diffusing Suspensions

Abstract: The diffuse reflection and transmission of light by a plane-parallel suspension of randomly oriented particles, scattering independently, are treated using radiative-transfer theory. Exact allowance is made for external and internal reflection at the plane surfaces of the matrix. General equations are derived in a form suitable for automatic computation. Some comparisons made between theoretical predictions and experimental measurements of the total transmittance of an optically thick diffusing suspension show satisfactory agreement with radiative-transfer theory and also with the Eddington approximation.

Excitation by light of ω + and ω − surface plasma waves in thin metal layers

Abstract: Calculations with the extended Fresnel formulae show, thatω+ andω− surface plasma waves can be excited by light, using the following optical arrangement: The metal foil is embedded between two dielectric layers of low index of refraction and equal thickness. Both sides of this 3-layer packet are in optical contact with a high index prism. Total reflection is broken byω+ andω− resonances in reflectivity, transmission and absorption. Theω+ resonance is mainly transmissive, (transmission through a 800 A thick silver foil greater than 50% at a wavelength of 5,461 A) theω− resonance is mainly absorptive. The polarization of the transmitted light exceeds 99%-theω+ resonance is proposed as a principle for a new optical polarizer.

Holography with Evanescent Waves

Abstract: Information contained in evanescent wave fields was recorded by holographic techniques. Internal reflection within a highly refractive liquid was used to create evanescent surface waves in the emulsion of immersed high-resolution photographic plates. The holograms have unique properties. When reconstructed by an evanescent wave, two mirror images of the same kind were formed; however, two conjugate images were obtained by reversing the direction of the surface wave. Although the holograms are very thin with fringes confined to the surface of the emulsion, they reconstruct in white light and exhibit frequency-selection properties similar to thick holograms.

Effect of a Shear Layer on Plane Waves of Sound in a Fluid

Abstract: Available theory indicates that plane waves of sound are reflected and refracted at an interface of relative motion (a velocity discontinuity) between two regions of fluid. If the relative velocity is sufficiently great, three types of reflection occur, ordinary, total, and amplified, depending on the incident wave angle. In the amplification regime, theory predicts resonances. Here the velocity discontinuity replaced by a transition layer of finite thickness separating the two fluid regions. This layer is approximated by two equal velocity discontinuities (Model I) and by a linear velocity profile shear layer (Model II). For one example in the regime of ordinary reflection, the effects of thickness are negligible for thicknesses up to 1/10 of the incident wavelength. For the chosen examples in amplified reflection, extreme reductions in transmission and reflection coefficients occur for a thickness as little as 1/50 of a wavelength. The two models approach (at unequal rates) total reflection and zero transmission at larger thicknesses. These effects are produced by layers of fluid traveling at or near the apparent wave speed parallel to the shear layer. Such layers tend to “insulate” the two fluid regions from each other.

Thin-film optical devices

Abstract: Thin-film optical devices are disclosed which function within the plane of a thin-film as lenses or prisms. They function in two dimensions, since the thin dimension of the film serves to guide the beam with respect to the third dimension. The devices are formed integrally from the body of the thin-film by variations in its thickness either along the path of the light beam or by such variations both along the path of the beam and transversely thereto, with contours of constant thickness intersecting the light path in an orientation affecting change of the direction of propagation of at least a portion of the light. Lenses of increased thickness are convergent if provided with convex contours or divergent if provided with concave contours; but lenses of decreased thickness with respect to the surrounding film are convergent if provided with concave contours and divergent if provided with convex contours. The prisms change the path of the entire beam. They can also be made to provide total internal reflection within the prism or frustrated internal reflection if disposed sufficiently close to another thin-film optical device. It is advantageous for the efficient operation of these devices if the mentioned changes in the film thickness are not abrupt but rather are tapered smoothly over a distance of several wavelengths of the light. This minimizes reflection losses and conversion to other modes.

Light wave coupling into thin films

Abstract: Coupling of light waves through a major surface of a thin film for propagation therein is achieved by means of a distributed action of the evanescent field of a light wave in an internalreflection prism disposed so close to the film that internal reflection is partially frustrated. Phase-matching of the evanescent wave and the wave propagating in the thin film is obtained by directing the input light beam at the proper angle within the prism toward the internal reflection surface and by providing appropriate indices of refraction of the components. Light-utilizing integrated circuits, including dielectric waveguides, modulators, parametric devices and amplifiers are provided with input and output coupling in this fashion. Systems employing directional coupling and channel dropping and adding are also disclosed.

Beugung thermischer Neutronen an einem Strichgitter

Abstract: The diffraction of thermal neutrons by a plane Ni covered ruled grating was investigated at various angles of incidence. A 54 lines per mm grating was used in the reflection case. The diffraction pattern was observed on both sides of the beam reflected in zero order (total reflection). Measured and calculated intensities are compared.

Role of the Lateral Wave in Total Reflection of Light

Abstract: The diffraction effects produced by light incident upon an interface at the critical angle of total reflection are examined for the purpose of explaining the weak illumination recently detected by Acloque and Guillemet, and by Osterberg and Smith. This illumination accompanies the rays reflected from the interface, but it occurs in a manner that cannot be interpreted in conventional geometric-optical terms. We show that a rigorous but simple approach that accounts for first-order-diffraction effects is capable of explaining the experimental results in terms of a lateral wave which in fact may provide the dominant field under certain circumstances. In particular, we examine the special case of a collimated light beam and show that the lateral wave is strongest, and accounts for the observed illumination, when the beam is incident at the critical angle of total reflection. The quasi-optical properties of this wave are emphasized and they are shown to provide straightforward physical interpretations for the various features of the weak-illumination field.

Critical‐Angle Reflectivity

Abstract: A method that predicts the observed critical‐angle reflection minimum for a liquid‐solid interface is presented. Confirmation between calculated and observed values is shown. Shear‐wave attenuation was found to be the most significant parameter in determining the depth of the minimum.

Oblique reflection of a plane impulsive electromagnetic wave from a plasma half-space.

Abstract: Using the known steady‐state solution, the transient response of the reflected wave for an incident wave of impulse wave shape is derived. It is indicated that the response “rings” at the plasma frequency divided by the cosine of the angle of incidence.

Highly Refractive Glasses to lmprove Electroluminescent Diode Efficiencies

Abstract: A series of low‐melting arsenic‐chalcogen‐halogen glasses were developed, with refractive indexes between 2.4 and 2.9. Despite severe thermal expansion mismatch, it was possible to form stable glass domes on planar electroluminescent diodes by using glass compositions which permit strain relief by thermoplastic flow. By reducing internal reflection losses, external efficiencies were routinely increased by factors from 4–6 for , , and diodes, resulting in external efficiencies as high as 7.2% for a solution‐grown diode.

The diffraction accompanying the regular reflexion of a plane obliquely impinging shock wave from the walls of an obtuse wedge

Abstract: The diffraction problem of a plane shock wave at the apex of an obtuse wedge treated by Lighthill (1950) is extended by assuming that the shock wave strikes the walls of the obtuse wedge at some finite oblique angle of incidence (not exceeding the critical angle). Transformations similar to that performed in the above-mentioned paper lead to a non-symmetrical boundary-value problem for an analytic function of a complex variable having a non-homogeneity in the form of a delta-function. It was found possible to extend, for the case considered, the method developed by Lighthill and construct the solution in almost as simple a form as given in the above-mentioned paper. The case of three-dimensional stationary flow is considered when the line of reflexion makes a finite angle with the edge of the wedge.

A Special Method for Precise Refractive Index Measurement of Uniaxial Optical Media

Abstract: A method was developed for measuring the refractive index of optical glasses and uniaxial crystalline solids when established refractometric methods are not feasible. A synthetic ruby cuboid was contacted to a prism of known refractive index and a spectrometer was used to measure the angles describing the optical path through the ruby-glass combination. Ray tracing equations were derived to compute the refractive index accurate within 3 × 10−5. Index values for both polarizations of ruby are given at selected wavelengths from 0.4358 μm to 0.7065 μm.

Switchable total internal reflection light deflector

Abstract: A new digital light deflector, capable of being switched in less than 35 µsec with less than 300 V, uses the principle of switchable total internal reflection. The deflector produces high-quality, high-contrast images and its low cost and high light transmittance make it potentially well suited for use in optical-beam-addressable memory systems as well as for other applications in which random deflection is desirable.

Distortion of electromagnetic pulses at totally reflecting layers

Abstract: The plane-wave reflection of electromagnetic pulses from homogeneous and inhomogeneous layered media is discussed. Special attention is given to the case of total reflection which is characterized in the frequency domain by phase distortion without amplitude distortion. For this case it is shown that the waveform in the time domain undergoes a rather remarkable change.

Versatile coupler for internal reflection spectrometry

Abstract: A versatile coupler for optically coupling a beam of radiation into or out of an internal reflection element for internal reflection spectroscopy is described. The coupler comprises a generally right-triangular member which is optically transparent and two of whose sides are bevelled but in opposite directions. In use, the vertically oriented beam enters at one side of the triangular coupler, internally reflects off its major surfaces and the hypotenuse and exits from the coupler at the opposite side from whence it enters the internal reflection element which is in optical contact with said opposite side.

Optical readout of electric fields by detecting reflected and/or refracted radiation which is incident within the range of variation of the critical angle

Abstract: An apparatus and method are disclosed for reading out information represented by variations in the intensity of an electric field by sensing the variations in the intensity of radiation deflected from a boundary of an electro-optic medium whose index of refraction varies with variations in the intensity of an associated electric field.

Reflection coefficient of a parallel-plate waveguide illuminating a conducting sheet

Abstract: The TEM mode reflection coefficient is analyzed for a symmetric parallel-plate waveguide composed of adjacent conducting wedges and radiating into a perfectly reflecting sheet oriented normal to the guide axis. Using the wedge diffraction method, the reflection from the conducting sheet is treated in terms of successive contributions or bounces that describe the interacting waves between the waveguide wedges and the reflecting sheet. For guides with small wedge angles (less than 75 degrees), the interacting waves can be treated as plane waves, and thus the reflection coefficient can be obtained through what is referred to as the self-consistent procedure. For guides with large wedge angles each of the interacting bounce waves can be resolved into component cylindrical waves. The total reflection from the sheet is then obtained by summing these iterative contributions. Calculated results from this analysis are in good agreement with measurements.

Selective collector for the wide-angle portion of a radiation beam

Abstract: Radiation-translating devices such as resonance backscatter cells and other fluorescent bodies receive incident radiation in a concentrated beam and emit processed radiation in diffuse form. The present system separates such processed radiation from any unprocessed incident radiation specularly reflected from the cell window by receiving both in an optical light pipe coaxial with the unwanted radiation. The light pipe is laterally immersed in an optical medium of such index that the unwanted radiation is retained by total reflection in the pipe and a major portion of the initially diffuse processed radiation is transmitted through the sidewalls to form an annular beam of moderate solid angle suitable for further processing by conventional optics. The same light pipe may also supply the beam of incident radiation to the translating device.

Apparatus for detecting small rotations

Abstract: Slight rotations are detected by the variation, according to the angle of incidence, of dephasing introduced by a total reflection between the light polarized perpendicularly to the plane of incidence, and that which is polarized parallel to this plane. The apparatus includes a polarized light source, a prism with a parallelogram-shaped section in which the light undergoes four total reflections, a dephasing plate, an analysis polarizer, and a light detector.

Cell Design for the Measurement of Transmission Spectra of Liquids at Very Long Infrared Wavelengths

Abstract: Measurements of the infrared transmission spectra of solids and liquids at moderate to high resolution are often troubled by undesirable interference effects caused by multiple internal reflection in parallelsided materials (commonly known as “channel spectra ”), which usually become increasingly pronounced at longer wavelengths. The purpose of this communication is to describe how a commercial vacuumtight liquid cell1 may be modified to minimize such interference effects arising both in the cell windows and in the liquid cavity, and to present liquid transmission spectra recorded in the range 7–70 cm−1 using such a cell in conjunction with a small commercial lamellar grating interferometer.2,3 Briefly, the amplitude of “channel spectra” observed in the transmission spectrum of a material layer depends4,5 directly upon the transparency of the medium, the effective reflection co-efficient at the material boundaries, and the degree of parallelism of the layer-thickness compared to the ir wavelength of observation.