DESIGN CONSIDERATIONS FOR VERTICAL DELTA-KAPPA DIRECTIONAL COUPLER

Theoretical results relevant to the design of a vertical DELTAkappa switch are presented. The principle of a DELTAkappa switch is the modulation of the coupling length by the application of an even electrooptic perturbation on the coupling region. Power switching requires that DELTAkappaL = pi/2. The initial state Can be tuned electrically. The coupling length and the change with the index perturbation depend on many factors, such as the thickness and the refractive index of the coupling layer. Based on an analytic solution of the eigenmodes and eigenindices of the symmetric structure, we clarify many of these dependencies, and obtain the relationship between the switching length required for power crossover and the available index change. We also discuss the merits of the DELTAkappa switch, and compare its efficiency with the conventional DELTAbeta switch.