Abstract

The planar prism has been considered as a passive component for high-density integration of optical devices. It may be fabricated by evaporating Si₃N₄ on a glass waveguide or grafting a semiconductor overlay on a dielectric waveguide. The planar prism is analyzed using a modified Suchoski’s exact numerical method,¹ including the case when the input beam is at oblique incidence to the endface of the prism. The Gauss-Legendre integral method is adopted instead of Suchoski’s Simpson’s rule approximation to discretize the continuous radiation modes. This method reduces the calculation time, which allows us to select a denser nodal set for the more important spectral region. In order to get a large-angle directional change of the beam, the critical angle at the endface should be less than 45°. As the thickness of the overlay increases, both the critical angle and the power of the fundamental mode decrease. Thus, an optimal thickness can be obtained when the power in the radiation modes is minimized. Numerous calculations have been performed with various thicknesses and indices of the overlay and main film. As an application, a finite-impulse-response filter is presented.

© 1993 Optical Society of America