Numerical analysis of α parameters and extinction ratios in InGaAsP-InP optical modulators

Abstract

The /spl alpha/ parameters and extinction ratios of InGaAsP-InP electroabsorption (EA) modulators and Mach-Zehnder (MZ) modulators are theoretically investigated. The bound states of excitons in quantum wells (QWs) under electric field are calculated through the finite-difference method, and quasi-bound states are obtained by the transfer-matrix method. Reducing the heights of the potential barriers of the QWs is prerequisite to achieving small values of the /spl alpha/ parameter for EA modulators and low driving voltages for MZ modulators. Bulk EA modulators are shown to inherently have relatively small /spl alpha/ parameters; however, they also require a tradeoff between the extinction ratio and the insertion loss. The /spl alpha/ parameters of symmetrical and /spl pi/-phase-shifted MZ modulators in the single- and dual-drive cases are also discussed.