Ultra-Compact Coupling Structures for Heterogeneously Integrated Silicon Lasers

Heterogeneous integration of III-V lasers on Silicon on Insulator (SOI) is crucial for next-generation optical interconnects. However, reducing the footprint of the couplers between III-V laser sources and silicon chips has been a challenge for dense photonic integrated circuit (PIC). Here, we propose a slot coupler and a bridge-SWG coupler with coupling lengths of only 5.5 and 5 μm respectively, to heterogeneously integrate III-V lasers on silicon chips. For such compact coupling structures, they also show high coupling efficiencies. At the wavelength of 1550 nm, the coupling efficiencies of the fundamental TE mode can reach 93.7% and 95.5% for the slot coupler and the bridge-SWG coupler, respectively. Moreover, these coupling structures possess excellent fabrication tolerance. In addition, we optimize the taper adiabatic coupler with a total coupling length of only 4 μm.