Silicon nitride grating coupler based on DBR and thermo-optic tuning technology

In order to solve the problem of the efficiency degradation and manufacturing complexity of traditional grating couplers under ambient temperature fluctuations, a Si₃N₄ high-efficiency grating coupler integrating distributed Bragg reflector (DBR) and thermo-optical tuning layer is proposed. The finite difference time domain (FDTD) method is used to simulate and optimize the key parameters such as grating period, duty cycle, duty cycle, incident angle, cladding thickness, DBR layer, etc., and the coupling efficiency of -1.6 dB and the 3 dB bandwidth of 106 nm are realized. In order to further enhance the temperature stability, an amorphous silicon (a-Si) thermo-optical material layer and a titanium (Ti) serpentine heater are embedded in the DBR to compensate for the decrease in coupling efficiency caused by ambient temperature fluctuations through local temperature control. The design not only simplifies the fabrication process, but also significantly improves the stability of the device over a wide temperature range, providing a highly reliable coupling solution for photonic integrated chips in non-temperature control scenarios such as optical communications, data centers, and in-vehicle systems.