Ultra-Compact Coupling Structures for Heterogeneously Integrated Silicon Lasers

TL;DR

This paper introduces ultra-compact, highly efficient, and fabrication-tolerant coupling structures for heterogeneously integrating III-V lasers with silicon chips, achieving over 90% coupling efficiency with minimal length.

Contribution

The authors redesign and propose three novel ultra-compact couplers with lengths of 4-7 μm, significantly shorter than existing solutions, and demonstrate their high efficiency and fabrication tolerance.

Findings

Coupling efficiencies over 90%, up to 95.7%.

Couplers are the shortest reported at 4-7 μm.

Structures show excellent fabrication tolerance.

Abstract

Due to the inherent in-direct bandgap nature of Silicon, heterogeneous integration of semiconductor lasers on Silicon on Insulator (SOI) is crucial for next-generation on-chip optical interconnects. Compact, high-efficient and high-tolerant couplers between III-V light source and silicon chips have been the challenge for photonic integrated circuit (PIC). Here, we redesign the taper adiabatic coupler with the total coupling length of only 4 {\mu}m, and propose another two novel slot coupler and bridge-SWG coupler with both coupling length of 7 {\mu}m, to heterogeneously integrate III-V lasers and silicon chips. We study theoretically the optical mode coupling process through the redesigned taper coupler, the final coupling results match well with the simulation in 3D-FDTD. The three compact couplers represent fundamental TE mode coupling efficiencies all over 90%, even 95.7% for bridge-SWG coupler, to the best of our knowledge, are also the shortest coupling structures (7 um). Moreover, these coupling structures also possess excellent fabrication tolerance.