D.M. Bolle’s research while affiliated with Worcester Polytechnic Institute and other places

Propagation characteristics and modal field distributions are obtained for an embossed rectangular waveguide employing isotropic n -type semiconductor material. A finite-element formulation utilising eight-noded quadrilateral elements was used to derive the dispersion spectrum with spurious solutions rigorously eliminated. The canonical model analysed here employs surface plasmons in a doped semiconducting medium as interface guided waves in the near millimetre wave range. Such structures have potential use in the guidance and control of millimetre waves and have applications in the design of planar quasi-optical integrated devices

This report presents the progress made during the period of June 1985 to June 1988 on experimental and theoretical investigations of waveguiding structures utilizing surface waves on high quality semiconducting substrates. When exposed to a d.c. biasing magnetic field, these structures display nonreciprocal behavior which can be used to design nonreciprocal devices such as circulators, isolators, and phase shifters in the millimeter and submillimeter wave frequency ranges. Reasonable losses can be achieved for device purposes when operated at cryogenic temperatures. Various experimental techniques were explored to achieve surface plasmon excitation on n-type semiconducting materials in the near-millimeter wave ranges. Although some limited studies have been carried out on this topic in the optical frequency range, very little work is available on experimental derivation of propagation characteristics of surface plasmon on III-V semiconductor compounds. For our purposes, most of the theory was deduced from optics with numerous experiments conducted to obtain a reasonable interpretation for the quasi-optical theory applied to the millimeter wave range. The quasi-optical method employed both the prism coupling and grating coupling techniques to generate surface plasmon on highly doped semiconductor materials in the frequency range of 110-160 GHz. (rrh)

The dispersion relation and electromagnetic field distributions for a gyroelectrically loaded waveguiding structure are obtained utilizing finite-element techniques. The structure considered consists of two layers, one a dielectric and the other a semiconductor, bounded by two perfectly conducting planes. The finite-element solution for the lowest real branches in the dispersion spectrum was compared against a numerical solution of the exact dispersion equation, and excellent agreement was found between the two. The structure, exhibiting nonreciprocal behavior, provides a suitable canonical model for the design of circuit components such as circulators, isolators, and phase shifters.

Recently, we have become aware of increased publication activity by authors who refer to the above early paper. We felt that it is particularly timely, therefore, to inform those concerned that in the above paper a few formulas, unfortunately, are in error.

A finite element formulation has been used to obtain the dispersion relation for a single dielectric-semiconductor interface bounded by two perfectly conducting planes. This system represents a suitable canonical problem for the design of non-reciprocal devices such as circulators, isolators, and phase shifters. The finite element solution for the dispersive behavior was compared against the exact solution for the lowest real branches, and excellent agreement was found between the two.

We consider an interface between dielectric and semiconductor semispaces, curved along the direction of propagation and infinite in the transverse direction. The semiconductor is magnetically polarized in the Voigt configuration. We give approximate expressions for the loss due to curvature.

An investigation is made of the dispersion characteristic for an H-guide structure where the two parallel plates are taken to be electric walls and the rectangular slab of either infinite width (single-interface structure) or finite width (slab structure). The material here is taken to be high quality, moderately doped n-type GaAs. The biasing magnetic field is perpendicular to the electric walls and is parallel to the normal of the sagittal plane (Voigt structure). The electric walls introduce coupling between TE and TM mode waves. It is pointed out that the hybrid surface wave mode must be at frequencies above its cutoff value. The nonreciprocal propagation characteristics are examined with a view to designing nonreciprocal devices.

Results are presented for planar insulated image guide structures modelling surface magnetoplasmon based non-reciprocal devices for the near-millimeter wave range. Sample results using GaAs substrates show acceptable performance for isolators over a bandwidth of 65 GHz in the 400 GHz range and differential phase shifters over a bandwidth of 30 GHz in the 550 GHz range with a 10% phase shift variation.