Design and modeling of a passively Q-switched diode-pumped Thulium laser at 2.3 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e923" altimg="si87.svg"><mml:mi mathvariant="normal">μ</mml:mi></mml:math>m

We report on a diode-pumped Tm:LiYF4 laser operating the 3H4 → 3H5 transition (at ∼2.3μm) passively Q-switched by Cr2＋:ZnSe saturable absorber. This delivers maximum average output power of 130 mW at 2304.6 nm with nearly diffraction limited beam, linear polarization (π) and no colasing ∼1.9μm. The corresponding pulse characteristics (duration/energy) are 1.24 μs/3.6 μJ repetition rate 36 kHz. By scaling under quasi-CW pumping, even shorter durations 870 ns higher energies 6.1 achieved. performance is simulated using model quasi-four-level gain medium “slow” absorber showing good agreement experiment. effect thermal lens discussed.