Long-term laser frequency stabilization for application in sodium resonance fluorescence Doppler lidar

Abstract

This paper mainly reports long term laser frequency stabilization combined Pound-Drever-Hall technique with Dopplerfree saturated spectroscopy technique for application in sodium resonance fluorescence Doppler lidar. A single-mode dye laser with Pound-Drever-Hall frequency stabilization is employed in this lidar system. But the center frequency of the laser can drift due to temperature changes or piezo actuator relaxation. To reduce these drifts, a sodium Doppler-free saturated fluorescence spectroscopy system is set up and the sodium Doppler-free features are used as absolute frequency references to lock the laser frequency. A sodium vapor cell is heated to and stabilized at 65ºC in order to provide sufficient atomic sodium vapor density. A photodiode is placed adjacent to the sodium vapor cell to detect the laserinduced fluorescence. The frequency stabilization operation is based on LabVIEW program.In reaction to the error signal, this software program will act via the dye laser controller on the reference cell piezo actuator to keep the master resonator on the sodium fluorescence spectrum line. In this lidar system, we lock the laser frequency at sodium D2a line with ~4MHz precision for hours.