Abstract: We report for the first time switching and modulation of light in a magneto‐optic waveguide that is a single‐crystal epitaxially grown iron‐garnet film. These experiments involve the Faraday rotation of the magnetic film and the motion of magnetization in the plane of the film. We have modulated light from a 1.152‐μm laser up to 80 MHz. We were also able to switch light between two waveguide modes by applying a magnetic field as small as 0.2 Oe.

Abstract: A new form of waveguide is described which can support propagation of electromagnetic waves in the dipole mode. The waveguide is coaxial with inner and outer members having cylindrical surfaces separated by a dielectric. The longitudinal and transverse impedances of these surfaces and the dielectric material are such that propagation in the dipole mode is possible. Structures having the necessary surface impedances are described. Apparatus for launching the dipole mode and extracting power from it are also described.

Abstract: A method of forming an article such as a light focusing fiber waveguide by applying to a substantially cylindrical starting member a layer of soot having a radially varying composition by means of flame hydrolysis. The starting member is removed and the resulting substantially cylindrical hollow cylinder is heated and drawn to reduce the cross-sectional area and to collapse the hole to form a fiber having a solid cross-sectional area with a radially varying composition.

Abstract: Guided modes of multimode waveguides exchange power if the waveguide deviates in any way from its perfect geometry. The power exchange problem is studied for a multimode slab waveguide under the assumption that the power coupling is caused by irregularities of the core-cladding interfaces. The problem is treated by means of coupled power equations. The main result of this study is the realization that the power distribution versus mode number settles down to a steady state distribution if the waveguide is sufficiently long. The shape of the steady state distribution depends on the correlation length of the function describing the core-cladding interface irregularities. For very short correlation length only the lowest-order mode carries an appreciable amount of power while the power carried by all the other modes is orders of magnitude smaller. For very long correlation length, on the other hand, all guided modes carry equal amounts of power. The steady state distribution is achieved regardless of the way in which the power was distributed over all the modes at the beginning of the guide. However, the total power in the steady state mode distribution is dependent on the initial power distribution.

Abstract: A modal-matching method is used to evaluate the transmission and reflection coefficients at a junction between two planar surface waveguides. Results are obtained for parameters which represent the junction between a solid-state laser and a planar optical waveguide. Favourable comparison is made with results obtained from an integral-equation method.

Abstract: Summary For a structure containing even a slight low-velocity channel in the upper mantle, the collection of higher mode Rayleigh waves decomposes naturally into a family of LVC channel waves and a family of crustal waves. Only the fundamental mode and the crustal waves need be considered as exciting Rayleigh waves significantly, since the channel waves do not generate significant amplitudes at the free surface. The broad properties of the interrelationship among the phase velocities of Rayleigh waves for the higher modes in the presence of a low-velocity channel (LVC) have been discussed a number of times heretofore. In this paper, we discuss the amplitude relationships among the eigenvectors for the first few higher modes without regard to the relative excitation of these eigenvectors by a particular source. We shall do so with the aid of an example taken from a particular model which has a LVC. The excitation of the modes will be treated separately. The example chosen is a shield structure taken from the literature (Harkrider 1970), to which two sedimentary layers have been added. The presence of sediments will be important even at long periods in the excitation functions; they are not overwhelmingly significant in this discussion. The structure is given in Table 1. The phase velocity of Rayleigh waves for the fundamental and the first three higher modes for this structure are shown in Fig. 1, for relatively short periods. The dispersion has been obtained using Knopoffs (1964) method as optimized by Schwab (1970); complete details are given by Schwab & Knopoff (1972). 2. Channel Rayleigh waves The apparent continuity of the phase velocities for adjacent modes is well known to be associated with the presence of a waveguide (Tolstoy & Usdin 1957; Tolstoy 1956; Mindlin & Deresiewicz 1955). Andrianova et al. (1967) have shown that such continuity from mode to mode occurs for Love waves in the presence of a lowvelocity channel. Below we show that this also occurs for Rayleigh waves in the presence of a low-velocity channel. Even with the poorly developed LVC present

Abstract: An acousto-optically coupled asymmetric waveguide pair and method of operation is disclosed. A pair of dielectric optic waveguides are defined in close proximity. Each waveguide is characterized by a propagation constant at which it can support propagation of a signal. An acoustic surface wave is effective to vary the propagation constant of the waveguides such that the signal is switched from one waveguide to the other.

Abstract: Motivated by recent developments in acoustic surface waves, a new approach is presented for the systematic analysis and description of acoustic wave phenomena in isotropic solids. This approach employs certain microwave network techniques developed in the context of electromagnetic waveguides. Acoustic wave structures are viewed as being composed of constituent waveguide regions coupled by junctions or ending in terminations; the waveguide regions are described in terms of equivalent transmission lines and the junctions or terminations by lumped equivalent networks. These transmission lines and equivalent networks contain electrical symbols and are cast into pictorial forms familiar in electrical engineering, but they represent purely acoustical quantities and effects. A rigorous transmission-line formalism is presented for acoustic wave propagation in uniform isotropic regions, which takes account of the translational invariance, reflection symmetry, and power orthogonality of the modal fields. This formalism is much more than a rephrasing of acoustic wave phenomena in terms appealing to electrical engineers; it forms the basis for a rigorous and practical procedure for solving complicated acoustic wave problems, and it yields pictorial insight into wave interactions. Despite its recent development, the method has already been applied successfully to several problems of current interest.

Abstract: The propagation of acoustic waves through a plane waveguide consisting of two rigid sinusoidal walls, is examined analytically. It is found that the phase difference between the walls, the wall wavenumber, and the mode number strongly influence both the form of the disturbances generated by the walls, and the conditions under which these disturbances become very large.

Abstract: The electromagnetic boundary value problem of two waveguides coupled by an aperture or an aperture in a waveguide radiating into free space may be described by an integral equation. An analytical solution to this integral equation cannot be readily found due to the complexity of the kernel. However, extremely useful results may be obtained if the method of moments is employed to reduce the integral equation to a matrix equation which can be solved by known methods. In this short paper, series and shunt slots in a rectangular waveguide are analyzed using this technique.

Abstract: An antenna array having two repetitive radiator systems in a single aperture, operating in two distinct frequency ranges. Each radiator system includes an open-ended, circular waveguide and a parallel plate waveguide. A monopole or a dipole is situated between the plates of the parallel plate waveguide and normal to them. The dimensions of the waveguides and the spacings between them are chosen to provide isolation between the frequency ranges.

Abstract: The mechanism of optical absorption from thin-film waveguides is investigated analytically for three cases: ideal waveguides, scattering in waveguides, and surface phenomena associated with molecular adsorption. Preliminary experimental results with methylene-blue dye placed on a waveguide surface show absorption magnitudes approximately ten times greater than is predicted for an ideal waveguide. Enhanced absorption based on modal variation is shown to be attributed to both scattering and molecular-adsorption effects.

Abstract: A model of double-heterostructure lasers is developed which gives the far-field pattern of the laser in terms of such waveguide parameters as the active region width and the dielectric constants of the layers forming the waveguide. For symmetrical waveguides an explicit expression is given. Experimental results are presented which show a close agreement between the theory and the measured far-field patterns. By adding an extra passive layer to the conventional double heterostructure laser a structure is produced in which the measured half-power width of the far-field distribution is reduced from 55° to 32°. It is shown in this case that the model is useful for estimating the near-field pattern from the measured far-field pattern and hence determining the unknown waveguide parameters.

Abstract: The results of experiments with dielectric obstacles of various geometries placed directly upon the apertures of circular and rectangular waveguides are presented. It is found that dielectric spheres, and in some instances dielectric cubes, two to four wavelengths in dimension produce directive patterns with low sidelobe levels. For some cross sections, the measured gain of these antennas is greater (6 dB in some cases) than that produced by optimum horns having apertures of identical cross section. The linearity of the polarization of these antennas is essentially the same as that of an open-end waveguide antenna.

Abstract: The results of an earlier paper, describing pulse propagation in multimode dielectric waveguides with random coupling, are specialized to the two-mode case. Because of their greater simplicity, the results for this special case provide more insight into the mechanism of pulse shortening due to mode coupling. The two-mode theory yields a formula for the width of a pulse carried by coupled guided modes that is found to hold also for four modes, so that it may be true for an arbitrary number of modes. This formula [eq. (23)] contains only the measurable distance required to establish the steady-state power distribution and the length of uncoupled pulses. The pulse length formula is identical with Personick's important result. Our treatment suggests that the characteristic length appearing in this formula may be accessible to measurement.

Abstract: The waveguide region of a double heterostructure junction laser is terminated at a point distant from a remote monolithic mirror. A passive region, which extends axially between the end of the waveguide region and the remote mirror, comprises a material having low absorption loss and is substantially impedance matched to the waveguide region.

Abstract: A no-load sensor is disclosed for protection of the electromagnetic wave energy generator in an electronic heating apparatus including a magnetized body of a ferrimagnetic material disposed within the waveguide launching section. Improved magnetic field producing means include a field concentrator associated with a permanent magnet member. Embodiments are also provided within a waveguide launching section having a reduced cross-sectional area adjacent to the ferrimagnetic body to concentrate propagated electromagnetic waves with a resultant decrease in the material requirements for exciting electron spin action to direct reflected energy from a load to energy absorbing means.

Abstract: Operations such as modulation, switching, mode conversion and the like are performed on light propagating in a thin film waveguide by a liquid crystal member overlaying a portion of the waveguide. The material of the crystal is such that its index of refraction in the direction of wave propagation, and normal thereto, is varied by application of an electric field, thereby producing a variation in the waveguiding properties of the waveguide. Using the same principles, mode filtering is achieved by overlaying a portion of the waveguide with an anisotropic material.

Abstract: : The frequency domain behavior of lossless, uniform, dispersive coupled transmission line systems and of lossless waveguides uniform in the direction of propagation but not necessarily in the transverse direction are investigated. Some frequency domain properties of the propagation constants of such systems implied by losslessness and uniformity are explored, and ways of approximating waveguide propagation constants are developed. (Author)

Abstract: The introduction of metallic ridges in waveguides allows much greater flexibility in the design of waveguide applicators for industrial microwave systems. Ridges can be used to increase, decrease, or redistribute the electric field in the workpiece. Several examples of such uses of ridged waveguides are described in a qualitative sense in this paper.

Abstract: A theoretical study of tapping a Love wave in an isotropic microacoustic surface waveguide is given. The surface Love wave is tapped by partial transduction into a bulk wave at a discontinuity. It is shown here that, by careful design of the discontinuity, the converted bulk wave power and the radiation pattern may be controlled. General formulas are derived for the calculation of these important characteristics from a relatively general surface contour deformation.

Abstract: Waveguides for use with guided elastic waves and guided optical waves wherein the lateral leakage rate of the waveguides is very small. The decreased leakage rate is effected by longitudinal strip regions or gratings periodically spaced on either side of the main waveguide region. These periodically spaced gratings rapidly decrease the rate of the evanescant portion of the wave according to a geometric law. Further, by controlling the amount of discontinuity presented by the periodic gratings the rate of evanescance may be controlled.

Abstract: A mode coupler useful in ranging systems for evaluating higher waveguide wave modes resulting from aperture deviations of an antenna exciter for determining angular deviation in the azimuth plane as well as in the elevation plane. Waves of the useful mode are separated from waves of a higher mode. A first waveguide section for propagating all evaluatable wave modes is adapted to be coupled to an antenna. A second waveguide section for propagating exclusively the useful wave mode is connected in series with the first waveguide section. A gap is provided between the first waveguide section and the second waveguide section and is provided with a plurality of apertures for the higher wave modes in the direction of propagation of the waves. New modes corresponding to the higher wave modes are substantially excited by the useful mode containing the ranging signal.

Abstract: There is a constant need for diode circuits employing rectangular waveguide. Coupling of the diode to the guide by using an inductive post is a popular method. The microwave circuit analysis of the equivalent circuit has been explored by complete theoretical analyses in the literature, but the results have been sufficiently difficult to apply that, in practice, recourse is often made to empiric characterization. This paper derives a simplified equivalent circuit based on a small perturbation approximation. The method is verified by experiment and is then used to evaluate a practical Gunn oscillator cavity.

Abstract: Numerical solutions for the problem of radiation from an infinite planar array of waveguide horns loaded at the aperture with a thick partially dielectric filled inductive step plus an external radome are presented. The analysis is applied to the problem of matching a practical array over a specified scan volume and frequency band. A technique from which the best possible initial match is obtained by varying the step width and thickness is presented. The final broad-band match is obtained with the aid of two thin capacitive irises located inside the waveguides. Experimental verification of the analysis and resultant computer program used for the design is presented in the form of waveguide simulator results. Three H -plane simulators are used and comparison of theory and experiment is presented for different combinations of external and internal matching structures.

Abstract: High-frequency tubes, such as klystrons or travelling wave tubes for example, producing high-power outputs within wide frequency bands by means of output devices comprising a dielectric window which ensures a seal between the evacuated enclosure of the tube and the load circuits which take the form of pressurized waveguides. This window is arranged in a waveguide section whose advantageously circular cross-section is larger than that of the output waveguide of the tube and that of the load waveguides, the connections between the waveguides being effected through junctions. The invention provides means which ensure to the thus constituted output device a resonance frequency equal to the centre frequency of the operating band of the tube, and means which effect impedance-matching throughout this band.

Abstract: Broad-band CW amplification with Gunn diodes in waveguide circuits has been obtained, with power gains typically between 10 and 15 dB and half-power bandwidths of more than 1 GHz. It is found that amplifier performance can be modeled with fair accuracy using a rough characterization for the diode parameters.

Abstract: The solutions of the dispersion equations for waves in plane and circular (symmetrical waves) dielectric waveguides are investigated. Thermal losses in the internal and external media are taken into account. Special attention is devoted to an analysis of the arrangement of the solutions in the complex plane of transverse wave numbers relative to the branchcut that separates the domains of physical and nonphysical solutions. It is shown that for both waveguides the solutions corresponding to backward non-natural waves are situated on the nonphysical sheet of the complex plane. Fundamental differences are noted for plane and circular waveguides in terms of the behavior of the wave numbers for a variation of the field frequency or waveguide parameters.

Abstract: Experimental tests on a new type of beam waveguide constituted by a series of equispaced dielectric frames are described. Field-pattern and power-loss measurements have been performed on short-circuited sections of the waveguide working at 10 GHz and on the 37-GHz prototype constituted by Teflon square frames. In comparison with the more common iris and lens beam waveguides, it presents advantages concerning diffraction, reflection, and dissipation losses. In addition, it is lightweight and compact. The experimental results confirm these advantages, along with a low sensitivity to assembling and constructive imperfections. Design criteria are suggested as a result of the optimization for the lowest losses obtained through numerical computations performed on the equivalent open resonator.