Compact Passively Q-Switched Yb:YAG Multipass Ring Lasers

An efficient and compact continuous-wave Yb:YAG laser with a slope efficiency of 50.3% with respect to the absorbed power was demonstrated using a multipass ring cavity (MPRC). Large cavity length ranges can be implemented using MPRCs with the same optical elements but different beam configurations. When Cr:YAG was used as the saturable absorber for passive Q-switching, various pulse widths and repetition rates were obtained. When a two-mirror MPRC, which is a compact ring laser cavity was used, the spatial hole-burning effect was reduced, and the spontaneous noise from the gain medium was not directly incident on the saturable absorber, causing less perturbation of the population difference of the saturable absorber than that of a linear cavity. This indicates that MPRCs can reduce the time jitter problem of a passively Q-switched laser. In this study, a Yb:YAG MPRC laser with a 33 ns pulse width is demonstrated, and the timing jitter of the repetition period was restrained to around 11%. The obtained experimental results are in good agreement with simulation results.