Passively Q-switched 10 mJ Tm:YLF laser with efficient OPO conversion to mid-IR

A diode-end-pumped Tm:YLF laser, passively Q-switched (PQS) with a Cr:ZnS saturable absorber, generated 10 mJ, 29 ns-long pulses at 1.9 μm, corresponding to a peak power of 350kW. A PQS laser operated at a maximum pulse repetition frequency (PRF) of 1 kHz, generating an average power of 10 W. The demonstrated pulse energy and average power represent significant increases over previous results with PQS Tm-doped lasers, and the 10 mJ pulse energy is comparable to that of much more complex actively Q-switched versions of such lasers. Using a cadmium silicon phosphide (CSP) optical parametric oscillator (OPO), the laser output was converted to 3.5-4.2 μm mid-IR emission. The OPO exhibited an optical efficiency of 64%, and generated 6W of mid-IR power.