Power Coupling Efficiency for Electro-Optic Directional Coupler Switch

Abstract

The investigation of coupling between optical waveguides is important for many directional coupler-based devices. Optical directional couplers, made from electro-optic materials, are the basis of several guided-wave devices including switches and modulators. The refractive index of the waveguide material changes due to the applied modulating field, which in turn affects the propagation constants of the two individual guides, the phase matching between them and the coupling length. When the change of refractive indices in the two guides are not identical due to unequal change of refractive indices in two coupled guides, then the power transfer efficiency deteriorates due to lack of phase matching between the guides. All these effects, combined together, change the total power transfer from one guide to another as a function of the applied potential, for switches and modulators.