Grating couplers for efficient integration of surface-emitting blue lasers and silicon nitride waveguide

We report here a theoretical investigation on high efficiency grating coupling for surface emitting blue lasers integrated with silicon nitride (Si3N4) waveguide. DBRs (distributed Bragg reflectors) were introduced into the design which located at the upper and one side of the Si3N4 grating coupler region, and oxide buffer layers was also incorporated simultaneously. By optimizing the grating coupler parameters and the DBR structure, the configuration can be adapted for single polarization or TE/TM simultaneous coupling. The coupling efficiency for TE polarization can reach 72.4 %, and the polarization-independent coupling efficiency of 48 % at vertical incidence was also achieved. This work presents a PIC (photonic integrated circuits) on III-V laser strategy for visible light PICs and innovative applications based on blue laser integrated devices.