Abstract
The numerical model of Q-switching regime for quasi-III-level laser including thermal effects was developed and verified with experiment. The room-temperature, high repetition rate, actively Q-switched Tm:YLF oscillator operating near 2-μm wavelength was constructed and examined. The 25-W fiber coupled laser diode with emission spectrum centered at 792-nm wavelength was deployed as a pump source. We have demonstrated in a short linear cavity above 5 W of output power for CW pumping and above 7 W for quasi-CW pumping regime (10 Hz repetition rate, 10 ms pump duration). The divergence angle was about 2.6 mrad, beam quality parameter M<sup>2</sup> < 1.1 for higher pump level. Applying 2-plates Lyot's filter, the continuous tuning in the range of 1845-1935 nm was achieved. The linewidth of tunable spectrum was less than 0.7 nm for all pump power range. The acousto-optic modulator made of fused silica was deployed for Q-switching. For the quasi-CW regime of pumping, the maximum Q-switched energy was 10.5 mJ with pulse duration of 22 ns corresponding to near 450 kW of peak power. For CW pumping regime we also demonstrated above 10 mJ for the repetition rate of 133 Hz, however with longer, 46-ns pulse duration as a result of significant increase in temperature of crystal. The output energy and peak power were limited in Q-switching regime by damages of applied laser elements.
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