Highly efficient passively Q-switched Tm:YAP laser using a Cr:ZnS saturable absorber

We describe a diode-pumped, passively Q-switched 2 μm Tm:YAP laser generating 10.5 W of average power. The laser utilized a Cr²⁺:ZnS saturable absorber with a nonsaturated transmission (T₀) of 90% and exhibited a record 46% optical slope efficiency and a 42% overall optical conversion efficiency, both measured relative to the incident 794 nm pump power. At maximum average output power, the laser generated 0.6 mJ Q-switched pulses with a maximum peak power of 32 kW. Pulse duration varied between 20 and 53 ns, depending on operating wavelength and pump power. A laser with a T₀=80% saturable absorber generated 1.45 mJ Q-switched pulses with a peak power of 138 kW.