Pushing the limit of pulse duration in Q-switched solid-state lasers with high gain

We demonstrate a 1064 nm, mJ-level, sub-nanosecond end-pumped Q-switched laser with weak feedback and high gain. We obtain the pulse duration of 449.7 ps, namely 1.2 times of the round-trip time, as well as the maximum energy of 0.26 mJ at the repetition rate of 1 kHz. The pulse energy is further scaled to 3.6 mJ by a double-passed amplifier, resulting in the peak power of 8.1 MW at the highest repetition rate of 2 kHz. Moreover, both the classical Q-switching theory and weakfeedback Q-switching theory are utilized to analyze the experimental results. The simulated results support that the Q-switched lasers with weak feedback and high gain, is effective for approaching single roundtrip time, which is the pulse duration limit. Smaller pulse duration is expected by virtue of this simple and compact configuration.