Coherent polarization locking of Q-switched Ho:YAG laser

Abstract

We had demonstrated the use of Coherent Polarization Locking (CPL) to mitigate the intra-cavity optical damage in a Q-switched Ho:YAG laser. By splitting the available pump power into two individual Ho:YAG laser rods, we had passively coherent combined two orthogonal polarized lasers with output pulse energy of 9.13mJ, pulse width of 14ns, operating at 800Hz pulse repetition rate. In contrast, when all the pump power was pumped on a single Ho:YAG laser rod built with the same cavity configuration, severe optical damage was observed. It was occurred at the surface coating of the laser rod when operating at < 2kHz pulse repetition rate, thus limiting the output pulse energy to < 5mJ. We also demonstrated, first to our knowledge, that by performing Q-switching only in one of the laser arms, it resulted in pulse operation for the entire CPL laser cavity.