Tolerance analysis for efficient MMI devices in silicon photonics

Abstract

Silicon is considered a promising platform for photonic integrated circuits as they can be fabricated in state-of-the-art electronics foundaries with integrated CMOS electronics. While much of the existing work on CMOS photonics has used directional couplers for power splitting, multimode interference (MMI) devices may have relaxed fabrication requirements and smaller footprints, potentially energy efficient designs. They have already been used as 1x2 splitters, 2x1 combiners in Quadrature Phase Shift Keying modulators, and 3-dB couplers among others. In this work, 3-dB, butterfly and cross MMI couplers are realized on bulk CMOS technology. Footprints from around 40um2 to 200 um2 are obtained. MMI tolerances to manufacturing process and bandwidth are analyzed and tested showing the robustness of the MMI devices.