Pulse-to-pulse coherent beat note generated by a passively Q-switched two-frequency laser

摘要

We demonstrate experimentally the pulse-to-pulse coherence of the beat note produced by a dual-npolarization passively Q-switched Nd:YAG laser subjected to a frequency-shifted, polarization-rotated, opti-ncal feedback. The reinjection of one laser eigenstate into the other eigenstate ensures the phase-locking ofnthe beat note against an external acoustic reference wave at the onset of each pulse, circumventing the in-ntrinsic memory loss of the optical phase between successive pulses. It opens the possibility to generate op-ntically a coherent pulsed beat note in the radio-frequency range with a subhertz linewidth, i.e., over thou-nsands of pulses. An application to lidar radar is discussed. © 2008 Optical Society of America