GaAs homojunction rib waveguide directional coupler switch

Abstract

An electro‐optic directional coupler switch has been fabricated with a GaAs homojunction structure and tested at 1.15 μm. Each single mode guide is made in a n‐LPE layer grown on a n⁺ substrate, the p⁺ rib used to confine the light being obtained by Zn diffusion and chemical etching. A calculation of the losses in the planar approximation roughly yields the large values of attenuation measured for TE and TM modes (∼8 cm⁻¹). By reversely biasing the ’’stepped Δβ’’ junctions with less than 17 V, more than 13 dB power isolation has been achieved for both switching states on a 6.3‐mm‐long device. Large improvements of the characteristics are expected from the additional design parameters provided by GaAs‐GaAlAs double heterostructure.