Thin-film lithium niobate multi-channel multifunctional photonic integrated chip for interferometric optical gyroscope

In this study, based on a thin-film lithium niobate (TFLN) platform, a multifunctional multi-channel photonic integrated chip operating in the C-band was successfully developed. The chip size is only 1.5 cm × 0.47 cm, which integrates 23 functional devices such as a multimode interference coupler, grating coupler, mode spot converter, phase modulator, and photodetector integrated using vertical coupling. The loss in each channel of the chip is less than 17.5 dB, the polarization extinction ratio is higher than 29 dB, and the modulation efficiency of the three units is greater than 4.2 V·cm. This TFLN chip can be used to replace some fiber optic devices in multi-axis optical gyroscopes, significantly improving the compactness of photonic links and reducing cost. For application verification, the optical coupling and electrical packaging of the device were conducted, a precision test was conducted by connecting three-axis interferometric optical gyroscopes system (7200s data, 0.1 Hz sampling frequency, bias instability are 0.041°/h, 0.03°/h and 0.022°/h), and the Earth's rotational speed was measured. This paper provides what we believe to be a new concept for the development of multifunctional photonic integrated chips for inertial sensing, demonstrating the potential of miniaturization and integration of core devices in precision measurement.