Dual-wavelength diode-pumped laser operation of N p-cut and N g-cut Tm:KLu(WO4)2 crystals

Abstract

Simultaneous continuous-wave laser oscillation at two wavelengths has been observed and studied in a diode-pumped monoclinic N p-cut Tm:KLu(WO4)2 for different transmission of the output coupler. The maximum output power reached 1.15 W with a slope efficiency of 20.4 % with respect to the absorbed power for polarization parallel to the N m optical axis. In an analogous N g-cut crystal, the dual-wavelength laser operation is accompanied by polarization switching with increasing pump power and the switching point depends on the output coupling. The thresholds are slightly higher, and the slope efficiency reached a maximum of 25.5 % for polarization parallel to N m at low pump levels, but at high pump levels, the oscillating polarization is parallel to N p, reaching maximum output power of 3.09 W. Simple modelling with rate equations taking into account reabsorption losses explains qualitatively the complex behavior observed in the continuous-wave laser experiments with this anisotropic biaxial laser crystal.