Abstract

Intersection waveguides are now a fundamental waveguiding structure for integrated optics. It has, therefore, become essential to find an accurate predictive theory or model for this geometry. Electro-optic switch arrays, for example, have been demonstrated by using this waveguide configuration, but insertion losses limit the performance of large arrays.¹ A recently developed theory based on a multiple scattering analysis has, for the first time, correctly predicted both the coupling and the radiative loss behavior for intersecting waveguides.^2,3 In this theory radiation loss can be represented by a coupling coefficient between guided and radiation modes of the waveguides. The contribution to this coupling coefficient from the waveguide arms and the intersection region can be made to interfere destructively, dramatically reducing the light coupled from guided to radiation modes.⁴ By adjusting the permittivity of the intersection region the relative magnitudes of the two coupling coefficients can be adjusted, thereby lending a processing degree of freedom with which to minimize radiative losses without restricting design parameters such as intersection angle.

© 1990 Optical Society of America