2.3-μm Tm³⁺:YLF laser passively Q-switched with a Cr²⁺:ZnSe saturable absorber

We report, what is to our knowledge, the first passively Q-switched operation of a 2.3-μm Tm³⁺:YLF laser by using a Cr²⁺:ZnSe saturable absorber. In the experiments, a tunable Ti³⁺:sapphire laser was used to end pump the Tm³⁺:YLF gain medium inside an x cavity. A Cr²⁺:ZnSe saturable absorber was also included in the cavity to initiate passive Q switching. At all pump power levels above lasing threshold, passively Q-switched operation of the Tm³⁺:YLF laser could be obtained at 2309 nm with pulse durations and repetition frequencies in the ranges of 1.2-1.4 μs and 0.3-2.1 kHz, respectively. Analysis of power dependent repetition rate data further gave an estimated value of 3.1% for the round-trip saturable loss of the Cr²⁺:ZnSe saturable absorber.