Analysis and suppression of passive chip stray light for integrated optical gyroscopes

The miniaturization of integrated optical gyroscopes requires the effective suppression of stray light crosstalk, which arises from the cascade of passive functional devices and significantly affects system performance. This study focuses on a tightly confined silicon nitride platform, where the optical mode field is strongly confined within the SiN core, enabling a compact chip design with dimensions of just 2 mm x 3 mm. Guided by the principle of gyroscope reciprocity, we thoroughly investigate the stray light leakage mechanisms in waveguide splitters. To address the stray light radiation characteristics inherent to passive functional devices, we introduce a stray light suppression strategy incorporating a conical adiabatic waveguide structure and a rectangular deepetched groove. This design effectively dissipates the asymmetric high-order mode leakage from splitters, preventing scattered light from coupling back into the main waveguide. Comparative analysis reveals that this approach optimizes the gyroscope system's zero-bias stability to within 0.2 degrees/h. Experimental results validate the design's effectiveness in suppressing stray light, demonstrating its suitability for low-cost, high-performance optical gyroscope systems with high integration density.