Pulsed-laser frequency locking for a compact 355-nm direct-detection Doppler wind lidar

A pulsed-laser frequency-locking technique is proposed for a compact 355-nm direct-detection Doppler wind lidar. The technique employs an integrated locking loop based on a dual-channel Fabry–Perot etalon (DFP) and a seed-tunable 355-nm pulsed laser to support compact airborne deployment and long-term frequency stability. A polarization-controlled beam-splitting structure is introduced before the DFP to suppress splitting-ratio drift and maintain balanced power distribution between the two channels. The reference pulsed laser passes through the same DFP channels as the lidar backscattered signals and serves directly as the frequency-feedback signal, enabling a compact integrated design without a dedicated locking channel. With a cascaded dual-loop proportional–integral–derivative control strategy, the pulsed-laser frequency is stably locked to the DFP reference operating point. During a 6-h temperature-locked closed-loop measurement, the Allan deviations are 1.54 MHz at 1 s and 0.89 MHz at 15 s, corresponding to equivalent wind-speed uncertainties of ∼0.27 and 0.16 m/s at 355 nm, respectively.