Electro-Optic Fabry-Perot Etalon for Frequency Stabilization in in Single-Longitudinal Mode Nd:YVO₄ Laser

Single-longitudinal mode lasers are widely used as light sources in coherent lidars due to their narrow linewidth and long coherence length. However, we observed spontaneous frequency drift in a single-longitudinal mode laser, accompanied by the oscillation of a second mode, which could compromise the laser’s performance. In this study, we recorded the frequency drift and the resulting power fluctuations. By analyzing the centroid positions of the laser spot, we confirmed that the drift originated from changes in the optical path length. To address this issue, we designed an electro-optic Fabry–Perot etalon. When a 400 V voltage was applied, the laser returned to single-longitudinal mode operation within 15 s. The electro-optic etalon induced an optical path variation of 0.05 μm. This work provides new insights into the application of electro-optic crystals for stabilizing laser frequencies.