High-energy 3.5 μm nanosecond KTA optical parametric oscillator

In this work, we demonstrated a 4.6 mJ short-pulse 3.5 μm mid-infrared laser, and investigated the effect of different repetition rates on the KTA-OPO conversion efficiency. At the optimal repetition rate of 100 Hz, a 1064 nm laser with electro-optically Q-switched was used to pump the KTA crystal, when pump energy was 26.5 mJ, a 4.6 mJ idler output was obtained, with a linewidth of 5.2 nm and a pulse width of 7.1 ns, corresponding to a conversion efficiency of 17.3%.