Study of Electrode Ablation for Femtosecond Laser Trimming of Micro Hemispherical Resonator Gyroscope

Micro hemispherical resonator gyroscope (mHRG) use a femtosecond laser to remove mass to achieve frequency trimming, which has the advantages of high efficiency and high accuracy. However, the current laser trimming method has the drawback of ablating the capacitance area of the electrode. A novel method for reducing the ablation area of the laser is proposed and demonstrated useful after comparative experiments. First, trimming parameters and propagation process of light is analyzed to reveal the main factor causing the electrode ablation. Then, a novel method using side laser drilling is proposed for reducing the effect of propagation of laser. A trimming process is optimized after researching the effect of ablation shape and angle of the etching triangle. Experiments show that the ablation area fraction of electrode area with gold film can be reduced to 0.2% using the optimized process, whereas the ablation area fraction before optimization is more than 10%. Meanwhile, the optimized trimming method can reach a higher trimming accuracy, which can help to improve the gyroscope’s performance.