Abstract: In a gyrotron (amplifier or oscillator) having an electrodynamic system in the form of a slightly irregular waveguide having a low effective Q, the frequency of the variable field is close to the critical frequency of one of the natural waves of the waveguide in operating modes having a high efficiency; as consequence of this: 1) a fairly accurate determination of the optimal parameters of the system may be accomplished by extrapolation of the results of the theory based on the fixed-variable-field-structure approximation; 2) a constraint on the output power exists which is caused on the one hand by mode competition and on the other hand by rebunching of electrons in an excessively powerful variable field, which according to the constraint imposed by the diffraction Q(1), may develop in the electrodynamic system of a gyrotron when a powerful electron beam is injected into it.

Abstract: There is disclosed an arrangement for coupling guided optical waves from thin-film waveguides to fiber waveguides, and vice versa. The thin film in the former type of guide is provided with an end region which is gradually tapered in thickness along the path of the wave to be guided therein to a cut-off value for the wave. This tapered region of the film causes the wave to propagate out of the film into the lower refractive index substrate of the guide along a small angle with respect to the film-substrate interface. Situated in the substrate slightly below the film-substrate interface is a cavity having a crosssectional shape and cross-sectional dimensions adapted for receiving an end of the fiber waveguide. By properly selecting the orientation and position of the cavity in the substrate, and of the fiber in the cavity, the fiber can be made to intercept the wave coupled out of the film. To insure efficient coupling of the wave into the fiber, the cavity is provided with a hemispherical end shape and is filled with a transparent material having a refractive index exceeding that of the substrate. A hemispherical lens is thereby formed which focuses and directs the wave into the fiber. Efficient coupling of the guided wave from the thin film to the fiber, or from the fiber to the thin film, is thus possible.

Abstract: A novel design procedure for diplexers built in waveguides below cutoff is presented. The design permits the integral construction of a diplexer--the whole unit is built in a single waveguide, thereby dispensing with the T junction and connecting flanges--if coaxial termination is used at the common junction. The design utilizes foreshortened bandpass filters, and is valid for bandwidths of up to a few percent. Simple expressions on calculating the connecting lengths are arrived at. A satellite telemetry diplexer designed using the derived expressions yields results which are in agreement with computed values.

Abstract: We describe a miniature transverse‐excitation CO2 laser in which the 10.6‐μm laser radiation is confined within a hollow rectangular‐cross‐section dielectric and metal waveguide. Using a flowing mixture of CO2, N2, and He we have obtained laser action at pressures up to 1 atm, and pulse repetition rates as high as 4 kHz.

Abstract: Electro‐optic intensity modulation is demonstrated in three‐dimensional (channel) waveguides fabricated by diffusion techniques in ZnSe and CdS. Typical diffused guide dimensions are 1.6 μm × 19 μm × 2 mm. Two electrode configurations giving two field orientations are used. Waveguide modulators with Vπ (voltage for π radians phase shift) of 72 V with rise times less than 5 nsec are described. Waveguide modulation in epitaxial layers of ZnS and ZnSe on GaAs is also described.

Abstract: A finite element method for the analysis of the mode spectrum of an anisotropic piezoelectric elastic wave- guide with arbitrary cross section is described. An assessment of the accuracy is given and the method is then used to com- pute the modes of a few typical waveguide structures.

Abstract: Fundamental (TE00 and TM00) transverse mode operation has been obtained from stripe‐geometry GaAs double‐heterostructure injection lasers with optical waveguides which are 2 μm thick Selection of the zero‐order mode perpendicular to the junction plane is achieved by providing a spatially nonuniform gain distribution within the waveguide The nonuniformity is realized by locating the p‐n junction within the waveguide such that the ratio of the thicknesses of the p and n regions is 2/1 For this choice of gain profile, the electronic gain of the zero‐order mode is greater than that for higher‐order modes by an amount sufficient to overcome the higher mirror loss of the zero‐order mode Along the junction plane, the stripe‐geometry configuration provides zero‐order mode operation As a result, pure fundamental mode operation has been obtained at current levels up to 22 times threshold Measurements are also reported for the internal stimulated efficiency, the bulk loss, and the electronic gain at threshold of the zero‐order mode relative to the higher‐order modes Single‐ended pulse output powers as high as 07 W (4×106 W/cm2 at the mirror) have been obtained from AR‐coated devices without observable mirror damage

Abstract: An asymptotic method based upon the principles of geometrical optics, which has been used for linear problems, is extended to nonlinear wave propagation in a rotating fluid of variable depth. It yields the same modes, the same phase function, and the same rays as does the linear theory. However along each ray the amplitude satisfies a nonlinear equation of Korteweg‐DeVries form. Thus, the theory combines certain features of the linear theory of short waves and the nonlinear theory of long waves. The theory is developed for a layer of fluid with a free surface or for an atmosphere which extends upward to infinity, and also for fluid in a channel or a waveguide. It may be useful in dealing with problems of geophysical interest.

Abstract: The transmission-line-matrix method of numerical analysis is developed to account for losses in the walls of a waveguide. Results are given in terms of the wave impedance of a waveguide with losses and also in terms of the power decay due to losses in the walls of a resonant rectangular cavity.

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: We describe the waveguide properties of the asymmetric dielectric slab formed by a very‐high‐index film on a low‐index substrate. The analysis is appropriate for Pb‐salt films grown on fluorite structure substrates. The mode reflectivities, surface scattering losses, and gain enhancements for the low‐order TE and TM modes are considered. The stronger confinement of the TM modes leads to larger gain enhancements than for the TE modes. For the film thicknesses of interest, 2–4 μm, the TE and TM mode reflectivities are comparable. Using the theory of Tien, the TE modes show substantially lower surface scattering losses than TM modes of the same order. The magnitude of this loss, however, depends on an unknown parameter σ, the variance of the surface height. Experimental results are presented for thin‐film diode lasers made with Pb Schottky barriers on p‐type PbTe (index 6.4) grown epitaxially on BaF2 substrates (index 1.42). The spontaneous emission at 77°K is shown to agree with the band‐band recombination ...

Abstract: A mechanism for frequency generation which can occur in waveguide distributed‐feedback lasers on anisotropic substrates is discussed. The proposed mechanism is a hybrid Bragg scattering between oppositely travelling waves with orthogonal polarizations. It explains the frequency spectrum observed in the preceding letter, which occurs as a result of the simultaneous presence of two coupled‐wave phenomena: mode conversion due to the anisotropic substrate, and backward Bragg scattering due to the periodic waveguide structure.

Abstract: It has been found experimentally that the conventional optimization of waveguide tapers for the interconnection of circular waveguides with different diameters fails if the ratio in the diameters becomes too large. With the aid of an accurate numerical analysis program, the reason for the failure was found to be the reconversion from the unwanted mode to the main mode, which is neglected in all known synthesis procedures. The performance of tapers can be considerably improved by the implementation of other design equations and establishing new design criteria. This results in somewhat longer tapers. Various tapers were designed according to these procedures for a maximum of -40-dB H/sub 02/-mode level between 40 and 110 GHz, and preliminary measurements on fabricated units substantiate the improvement. It is further shown that the mode conversion at cutoff does not exhibit any singularity.

Abstract: The transmission-line-matrix method of numerical analysis is modified to allow boundary points to fall anywhere between nodes on the mesh. Results are obtained for circular and elliptical waveguide cross-sections on a cartesian mesh.

Abstract: A radial waveguide-3dB hybrid coupler in a circular configuration comprises two coaxial radial wave-guides, one with an input port and one with an output port, having a branch-guide hybrid coupler formed in the common broad wall. Dual arrays of one-port, reflective type, power amplifying modules are mounted at the periphery of the waveguide structure. Input power is coupled to both module arrays and reflected to the output port to provide gain-enhanced output power over broad bandwidths.

Abstract: The attenuation in a waveguide partially filled with absorbing material can become larger than that of the same waveguide completely filled with that same material. Theoretical and experimental results are presented together with field distributions showing that this excess loss is due to a large concentration of electric field within the lossy dielectric in the partially filled configuration.

Abstract: A coupler is described for coupling two microwave transmitters or receivers in one frequency band and two microwave receivers or transmitters in a second frequency band to a common central wave guide. The device provides high isolation between the four ports. Energy in a first band of frequencies is coupled to feed wave guides which are dimensioned to transmit this first band of frequencies. These feed wave guides are arranged to handle a pair of separate channels for the first band of frequencies, the signals in one of the channels having the same frequencies but a polarization which is orthogonal to that of the signals of the other channel. A pair of channels in the second band of frequencies, the signals in one channel having the same frequencies but a polarization orthogonal to that in the other channel, may be fed directly to the central wave guide. A branch wave guide is interposed between each of the feed wave guides and the central wave guide for coupling the energy in the first band of frequencies to the central waveguide, the branch wave guides being dimensioned to operate as a cutoff filter at the second band of frequencies (thus preventing such signals from entering the feed wave guides) and a high pass filter at the first band of frequencies.

Abstract: A circuit model is used to present the basis forthe existence of complex propagation constants and backward wave modes in lossless coupled dispersive transmission lines. In particular, for the 2-line lossless case, conditions for realizing complex modes, as well as the possible forms for the \omega-\beta diagram are given. Methods for approximating the mode behavior of lossless waveguide systems, uniform in the propagation direction, but with transverse plane inhomogeneities, are presented using coupled-line models. These methods are derived from the Schelkunoff representation of such a waveguide structure by an infinite set of coupled TE and TM dispersive transmission lines. The techniques used in this paper depend on an approximation which reduces the infinite number of lines to a finite number. One approximation method interpolates the parameters of a realizable 2-line system to approximate the behavior of the infinite line system up to a frequency in the vicinity of the secondlowest eigenmode. A second method is a systematic network procedure for eliminating coupling ports of the infinite structure so as to obtain a finite number of coupled lines to approximate the mode behavior. These two methods are illustrated by 2-line models for round waveguide loaded with a dielectric rod. The mode behavior of the loaded guide is surprisingly well approximated by both the 2-line models.

Abstract: On the boundary vacuum — a dense magnetoactive plasma, an incident RHCP (right hand circularly polarized) wave is strongly reflected ifω 0 2 /ω 2 ≫ 1 andω ce/ω > 1;ω, ω 0,ω ce are the ncident wave frequency, the plasma frequency and the electron cyclotron frequency, respectively. This reflection strongly lowers the efficiency of the plasma heating by microwaves. Our experimental study shows that a suitable matching system consisting of dielectric plates, placed in front of the plasma, can ensure practically complete transfer of the RHCP wave energy into a dense plasma. The experiment was carried out in the S band waveguide (λ=12·7 cm) with the power of the order of l kW.

Abstract: A new calculable standard of voltage-reflection coefficient and voltage standing-wave ratio consists of a quarter-guide-wavelength section of waveguide having cross-sectional dimensions different from those of the waveguide system into which it is inserted. Design equations are given for waveguide of rectangular and coaxial cross-sections.

Abstract: In a process for the production of integrated optical circuits in particular waveguides, radiation-sensitive material is exposed to electromagnetic surface waves. The refractive index of the exposed layer may be changed by physical or chemical processing which is carried out either during or after exposure. Preferably the surface waves are produced by total reflection.

Abstract: The attenuation of the HE11 mode in a brass corrugated circular waveguide of internal diameter 8 cm is measured in the frequency range 8-10 GHz by means of a resonant-cavity technique. Attenuation values of the order of 4 dB/m are observed. The mean attenuation level exceeds the theoretical value for a perfect corrugated waveguide by about 25%, which is within the experimental accuracy. The attenuation measured is substantially less than that predicted for the H11 mode in a smooth-wall waveguide of comparable size and is, in fact, close to that predicted for the H01 mode.

Abstract: An approximate analytical model has been developed for predicting the radiation attenuation in curved rectangular dielectric image waveguide. The radiation is shown to depend on radius of curvature, dielectric constant, and cross-sectional dimensions. Correlation of experimental measurements-with theory was good.

Abstract: A mounting assembly for mounting a rectangular ferrimagnetic toroid core longitudinally within a rectangular waveguide of a low-power-mode ferrite-core phase shifter comprising: A. FOUR PEGS INSERTED INTO FOUR HOLES POSITIONED IN THE WAVEGUIDE WALLS SO THAT ONE PEG IS POSITIONED ON EACH SIDE OF THE WAVEGUIDE AT EACH END OF THE CORE AND ACTING TO RESTRICT LATERAL MOVEMENT OF THE CORE WITH RESPECT TO THE WAVEGUIDE; B. DIELECTRIC TRANSFORMERS AT EACH END OF THE CORE PARTIALLY OVERLAPPING EACH OF THE FOUR PEGS AND ACTING TO RESTRICT MOVEMENT IN THE LONGITUDINAL DIRECTION OF THE CORE WITH RESPECT TO THE PEGS.

Abstract: An improved arrangement for an automatic direction finding system for resetting microwave antennas when signals are received from a moving transmitter wherein the higher waveguide wave modes produced in the azimuth plane and in the elevational plane are utilized as deviation information, whereby the advantages of mode couplers for square waveguides may be used with antenna exciter having a circular, octogonal or cross-shaped cross section. The arrangement includes a junction or transition section between an antenna exciter having one of the above mentioned cross section and a waveguide with a square cross section. A mode coupler, which is provided with a microwave network, is connected to the waveguide with a square cross section to separate the deviation information of the received signal from the useful signal and the H20-H02 signal containing the deviation information is fed to a comparator network for further processing to provide resetting signals for the antenna.

Abstract: Coupled-mode theory and numerical methods for solving uniform waveguides are combined to analyse the transition of a waveguide of slowly varying arbitrary cross-section. The technique has been applied to the design of the broadband Marie mode transducer. Theoretical and experimental results are given.

Abstract: An experimental study of pulsed transferred-electron oscillators operating in waveguide circuits is reported. Quenched-domain mode operation is shown to be present for short (less than 20-/spl mu/m) supercritically doped GaAs samples operating at X-band frequencies (8.2-12.4 GHz) and for bias-voltage values up to six times threshold value. Analysis of the waveguide circuit shows that the chip sees a parallel resonant circuit, and theoretical computations with a sinusoidal voltage waveform are shown to be reasonably accurate. The load admittance presented to the chip is experimentally evaluated.

Abstract: It is shown experimentally that the straight edge between two intersecting planes on Bi12 GeO20 acts, in accordance with the diffraction scaling theorem, as an acoustic-surface-wave lens. A helical delay line can be treated as a repetitive stack of edge lenses. Under certain conditions, the ‘beam waveguide’ may be metastable.