MODAL-ANALYSIS OF A DIELECTRIC WAVE-GUIDE WITH PLANAR GUIDING-NONGUIDING BOUNDARIES WITH A FLARE IN THE DIRECTION OF PROPAGATION

We make an analytical study of the modal characteristic equation of a slab waveguide with a flare bounded by two planes. We choose cylindric al polar coordinates (rho, phi, z), and assume that the two bounding p lanes are extended infinitely in the z-direction, and are represented by phi = phi(1) and phi = phi(2) so that phi(2) - phi(1) is very small . The field in the z-direction is assumed to be uniform, and we consid er propagation along the rho-direction. Using the weak guidance approx imation, the characteristic equation is obtained. Numerical computatio ns show that only one global mode can be sustained in such a structure for the model nu = 0, corresponding to the coordinate phi. There is a n attenuation in this supported mode, and this is because of the flare . (C) 1998 John Wiley & Sons, Inc.