MEMS-tunable polarization management in photonic integrated circuits

Abstract

Optical fibers are generally polarization-insensitive while photonic integrated circuits (PICs) often exhibit a large polarization dependence due to the high-aspect-ratio and high-index-contrast of integrated waveguides. As PICs become more mature there is an increasing need for tunable polarization management on-chip. Although micro-electro-mechanical systems (MEMS) are increasingly finding application in PICs for optical switching and phase shifting, they have so far not found wide application for polarization management. In this work we propose two optical MEMS architectures for polarization management enabling tunable polarization splitting and rotation – key functions so far lacking in PICs. The first structure consists of a directional coupler with a MEMS-tunable gap enabling a continuously-variable polarization splitting ratio. A second architecture consists of a symmetry-breaking MEMS perturber suspended over an air-cladded waveguide enabling tunable polarization rotation. For both architectures we simulate a polarization extinction exceeding 25 dB, and the operating bandwidth can be as large as 100 nm. We conclude with a discussion of actuation schemes and examine fabrication considerations for implementation in PIC foundries.