Highly efficient grating coupler between optical fiber and silicon photonic circuit

We report on a highly efficient grating coupler between an optical fiber and a silicon photonic circuit. Using layers of Si/SiO₂ as a Bragg mirror and amorphous Si we have measured a coupling efficiency of 69.5%.

Introduction

Due to the high refractive index contrast, Silicon-on-Insulator (SOI) technology is an attractive platform for compact integrated photonic circuits. SOI is also CMOS-compatible and has created widespread interest not only in the photonics community, but also in the electronics world to integrate photonic functions in the next generation of high speed processors. However, efficient coupling in and out of a silicon circuit remains a challenge, due to a huge mismatch between the optical fiber mode and the nanophotonic waveguide mode.