Heterogeneous interconnection of low-loss and dense material platforms using adiabatic tapering coupler

Recently, we successfully realized amorphous silicon carbide (a-SiC) integrated photonics with optical losses as low as 0.78 dB/cm. Moreover, the deposition of a-SiC was done at 150 ℃, which enables successful lift of a-SiC as an additive step to existing photonics circuits. In this work, we present an adiabatic taper coupler which provides bidirectional lossless connection between two integrated photonics platforms: thin-film silicon nitride (Si 3 N 4 ) and a-SiC. Normalized power transmission of 96.61% is presented, and the coupler enables strong confinement when coupling from weakly confined thin-film device to normal thickness device. By utilizing such a coupler as bridge, switching back and forth between Si 3 N 4 and a-SiC platforms can be easily realized. This allow us to carry out applications including quantum interference and digital Fourier spectroscopy, in which long optical delay lines are constructed on Si 3 N 4 and highly integrated circuits are built on a-SiC.