Frequency Tuning Method on Teeth-Like Tines of the Fused Silica Micro-Hemispherical Resonator Using Femtosecond Laser

The fused silica micro-hemispherical resonant gyroscope is a new type of solid-wave gyroscope and offers numerous benefits including high precision, low power consumption, small size, and long life. The core component of the gyroscope is the micro-hemispherical resonator (MHR). The inevitable frequency split of the MHR working modes will directly restrict the performance improvement of the gyroscope. Therefore, it is crucial to eliminate the frequency split by a tuning method. A femtosecond laser ablation method is reported for permanent frequency tuning of the wineglass modes in MHRs with teeth-like tines. Firstly, the influence of different positions and depths of the tuning ablation grooves on the eigenfrequencies and frequency split of the working modes is determined by theory and simulation. In the low-frequency rigid axis, the efficient tuning method is located at the outer edges of the tines, while closer to the middle of the tines can obtain a more accurate frequency split. In addition, the Laser Doppler Vibrometer (LDV) test system has been built to test the frequency split of the MHR. Femtosecond laser ablation experiments were then designed, and the experiments and simulations were in good consistency. Finally, combined with the test system and the tuning method, the frequency split of a MHR is reduced to one percent of the initial, which is helpful for the gyroscope’s performance. [2023-0130]