Stable passive Q-switching of a Tm:  LiYF4 laser is obtained using polycrystalline Cr2+:  ZnS as a saturable absorber. The achieved maximum pulse energy of 0.9 mJ and peak power of 65 kW for a pulse duration of ∼14  ns represent substantial improvement and highest values for a passively Q-switched diode-pumped Tm laser operating at ∼1.9  μm.

Single pulse energies as high as 145 µJ were generated with a passively Q-switched diode-pumped Tm:KLu(WO₄)₂ laser using poly-crystalline Cr²⁺:ZnS as a saturable absorber. The maximum average power reached 0.39 W at a pulse repetition rate of 2.7 kHz with pulse durations in the 25 - 30 ns range. The maximum peak power amounted to 6 kW. The obtained results agree well with theoretical analysis.

We report on polarization switching in the Tm:KLu(WO4)2 laser between the Nm and Np states oscillating at different wavelengths: 1946 nm for N m and 1922 nm for N p . There is a certain power range where the two laser polarizations coexist in this biaxial crystal. The switching strongly depends on the thermal management of the active medium through either the mode matching between the pump and the laser beams or the cooling of the crystal faces. Intensity, arb. units Wavelength, nm P inc = 11.0 W P inc = 12.0 W P inc = 18.0 W

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Pulse energies as high as 145 µJ, peak powers of 6 kW and pulse durations in the 25-30 ns range were generated with a passively Q-switched diode-pumped Tm 3+ :KLu(WO 4 ) 2 laser using polycrystalline Cr 2+ :ZnS as saturable absorber.