Low-cost multi-mode diode pumped Tm:YLF laser: Multi-color & Q-switching operations

In this paper, we report a low-cost multi-mode AlGaAs laser diode pumped broadly-tunable solid-state Tm:YLF laser at room-temperature operating in two different regimes: multi-color and Q-switching. A low-cost multimode AlGaAs laser diode, driving 3 W power at 780 nm, was used to excite the 3% Tm3+-ion doped YLF laser. In the continuous-wave regime, 650 mW of output power was obtained at 1942 nm with 41% power efficiency (indicates high cross-relaxation). The output wavelength can be tuned between 1831 and 2031 nm with a birefringent filter (BRF). To the best of our knowledge, this range is the broadest tuning range obtained from a Tm:YLF laser in 2 mu m band. Furthermore, multi-color laser operations were observed by translating the crystal inside the cavity (without BRF) i.e. three two-color, two three-color and one four-color were obtained. As far as we know, these results are the first demonstration of three- and four-color 2 mu m laser. Additionally, Q-switching regime were obtained by adding a saturable absorber into the cavity. In this regime, the repetition frequencies can be arranged between 16 and 100 kHz with a maximum of 2.7 W peak power and 2.39 mu J pulse energy by translating the saturable absorber along the stability region.