Analysis of InP-based guided-wave electro-optically rotatable wave plates for polarization transformers

Abstract

In many optical systems with critical polarization control there is a need for compact, electrically driven polarization transformers, preferably with endless and reset-free control.1 To date, there has been little work on monolithically integrated structures that perform this function. Most configurations of electro-optic retarders and polarization transformers in III-V materials are based on passive and constant-polarization rotation2 or use a fixed direction of the static electric field.3,4 This leads to a limited range of the polarization transformation. Recently, a guided-wave LiNbO3 device was reported in which electro-optically induced rotatable wave plates were realized.5 A combination of rotatable quarter- and half-wave plates does permit full- range and endless polarization control. In this paper we show by numerical simulation that this concept can be transferred to InP-based waveguides, which would permit integration of the polarization transformer with a local-oscillator laser. In particular, we show that it is possible to rotate the polarization of waveguide modes by a rotatable electric field, even for waveguides with an intrinsic (low) modal birefringence.