Heterogeneous integration of InP and Si₃N₄ waveguides based on interlayer coupling for an integrated optical...

In this study, we demonstrate a novel, to the best of our knowledge, integrated indium phosphide (InP) and silicon nitride (Si₃N₄) waveguide platform, which is based on interlayer coupling, to achieve heterogeneous integration of a photodetector and waveguide ring resonator firstly. In order to improve the gyro bias stability, the Si₃N₄ and InP waveguides were designed with a high polarization extinction ratio and ultra-low loss. Three-dimensional finite difference time domain methods are used to optimize the InP taper dimensions to provide efficient optical coupling between the Si₃N₄ and InP waveguides. The optical coupler with a length of 100 µm is designed to achieve optical coupling between the Si₃N₄ and InP waveguides while maintaining its state of polarization all the way from the taper waveguides. The coupling efficiency of the optimized interlayer coupler has been improved to about 99.5%.