Abstract

The design for a new velocity matched traveling wave directional coupler modulator (DCM) in AlGaAs/GaAs material is proposed. The DCM characteristics are compared with those of the n-i-n modulator proposed by Kim et al.¹ and the GaAs superstate modulator proposed by Nees et al² In this paper, velocity matching in the DCM is achieved by covering the modulator and its electrode structure with a dielectric material of high dielectric constant which reduces the micro wave phase velocity to match the lightweight velocity. The dielectric materials used for the velocity matching analysis are alumina (Al₂O₃) and tantalum pentoxide (Ta₂O₅), whose relative dielectric constants at microwave frequencies are 10.0 and 27.0, respectively. The optical and microwave characteristics of the modulator are analyzed using the effective index method (EIM) and the finite difference method (FDM) repectively.

© 1991 Optical Society of America