A finite element program for the analysis of anisotropic optical waveguides is described. The appearance of spurious numerical modes, due to the fact that the functional is nonpositive definite is discussed and a possible solution to the problem is presented. For isotropic waveguides it is shown that both EH- and HE-type modes can be very accurately approximated by two different scalar finite element programs. Finally, a method for calculating the attenuation of leaky modes in a single material integrated optic waveguide using this scalar finite element method is proposed.

Finite Element Analysis Waveguides of Optical

The effective-index method for determining waveguide dispersion is derived from the scalar wave equation and applied to optical fibers of arbitrary cross-sectional shapes. In the simplest use of the method, the optical fiber is replaced by an equivalent slab waveguide with an index profile derived from the geometrical shape of the fiber. Results from analyzing circular, elliptical, and cusp-shaped fibers are used to illustrate the general features of the method. A procedure is also given for improving the accuracy of the method applied to a class of single-mode fiber.

Analysis of optical fibers by the effective-index method

Dielectric image-guide Gunn oscillator using fused quartz as the guide material has been investigated at frequencies around 94 GHz. Computer-controlled CO/sub 2/ laser cutting of quartz to the designed image-guide patterns has also been achieved. A resonant disk and pin bias circuit was used to tune the oscillator to an output power of 5 mW at the oscillation frequency of 94.2 GHz. An electronic frequency tuning of 350 MHz was measured with the oscillation characteristics similar to waveguide cavity oscillators. By varying the bias circuit disk and pin parameters, the Gunn-oscillator tuning characteristics have also been recorded for the future circuit performance optimization.

Millimeter-Wave (W-Band) Quartz Image Guide Gunn Oscillator

All-dielectric ridge waveguides may be useful as elements of millimeter- and submillimeter-wave integrated circuits; A planar metallic V-coupler can be used to couple energy between the guide and small circuit elements such as diodes. Desirable characteristics in such a guide/coupler system are a) quasi-single mode propagation; b) low radiation loss in bendy c) low coupling loss between guide and devices and d) adequate physical strength. In this paper, we discuss the general problem of designing guides and couplers to obtain the desired characteristics. The principal method used is simulation in the range 2-7 GHz. We find that with good compromise designs, typical coupling loss between waveguide and a small device is about 1.4 dB, exclusive of dielectric loss and ohmic loss in the coupler.

Design of Dielectric Ridge Waveguides for Millimeter-Wave Integrated Circuits

Equivalent Network Analysis of Dielectric Thin-Film Waveguides for Optical Integrated Circuits

The mode dispersion of dielectric optical waveguides is calculated by the effective-index method and is compared with previously reported experimental and theoretical finite-element results for trapezoidal cross-section waveguides. Agreement between experimental and predicted results is very good. This is significant because it means that stripe waveguides can be designed with specific modal propagation properties using the much simpler effective-index method even though the waveguide cross-section is not rectangular.

J.G. Gallagher

Papers

Mode dispersion of trapezoidal cross-section dielectric optical waveguides by the effective-index method