High-Precision Laser Frequency Stabilization Method in Fiber-Optic Sinusoidal Frequency Modulation Interferometer

This work establishes a frequency stabilization reference signal model for modulated lasers under low-pressure gas absorption, specifically considering the deviation of original frequency locking reference points from absorption peaks induced by intensity modulation. We propose a dynamic frequency locking adjustment method based on real-time tracking of intensity modulation coefficients. Through PID control, this approach enables precise adjustment of drive current to maintain long-term locking of the laser’s central frequency to specific gas absorption peaks during wide-range, high-bandwidth modulation. Experimental results demonstrate that the relative stability of the semiconductor laser’s central frequency achieves better than 1.05 × 10−8 at a sampling time of t = 0.4 s. Finally, integrating this stabilization method into a sinusoidal frequency-modulated laser interferometer validates its effectiveness. The results show that the interferometer achieves a measurement resolution better than 1 nm and a stability of 0.58 nm (1σ), nanoscale displacement measurement is achieved.