High-Power CW and Q-Switched Tm:CaYAlO4 Lasers at $1.94~\mu \text{m}$ for Shallow Water Absorption

We report on 790-nm diode-pumped continuous-wave and passively Q-switched Tm:CYA lasers. For continuous-wave laser operation, a maximum output power of 7.62 W is achieved with slope efficiency of 50.9%. Passive Q-switching of the Tm:CYA crystal is also obtained with a maximum average output power of 1.32 W using a Cr:ZnSe saturable absorber. The shortest pulse width is about 42.6 ns with a pulse energy of 60.2 $\mu \text{J}$ and a pulse peak power of 1.41 kW. These results represent the best laser performances of continuous-wave and passively Q-switched Tm:CYA lasers, to date. The 1.94- $\mu \text{m}$ Tm:CYA lasers provide better laser sources for shallow absorption of biological tissue.