High-Q Spiral Resonator for Optical Gyroscope Applications: Numerical and Experimental Investigation

This paper reports the numerical and experimental results of a high-Q silica-onsilicon spiral resonator to be used in microoptical gyroscopes having a potential resolution <; 10 °/h. First, demonstration of a Ge:SiO₂ waveguiding spiral cavity as sensing element for gyro applications is given, and results of its optical characterization are provided. Quality factor, finesse, free spectral range, and thermal stability have been measured, clearly showing the potential of the device for gyro applications. The effect of coupling tuning through micrometer scale heaters and the supported eigenstates of polarization have also been experimentally investigated. The thermal stabilization of the silica chip is realized using a thermoelectric cooler co-packaged with the resonant cavity. The Q-factor of the spiral exceeds 106, and the thermal drift of the resonance frequency is very low (<; 20 kHz/s). An original formula estimating the bias drift due to the Kerr effect has been derived, proving that a bias drift of 0.2 °/h can be achieved by controlling the polarization noise. The resolution of the angular velocity sensor has been numerically estimated by exploiting the experimental results. We demonstrate that the resolution of our device can be improved to values less than 10 °/h, by decreasing both the propagation loss within the resonator (<; 0.05 dB/cm, which is currently achievable) and the cavity insertion loss to 1-2 dB (typical value).