Efficient diode-pumped passively <i>Q</i>-switched laser operation around 1.9 μm and self-frequency Raman conversion of Tm-doped KY(WO4)2

Abstract

Passively Q-switched operation of Yb,Tm:KY(WO4)2 and Tm:KY(WO4)2 lasers diode pumped at 805 nm has been investigated. A thin plate of Cr:ZnS was used as a saturable absorber for passive Q switching. A maximum average output power of 116 mW emitted at 1.9 μm in comparison to 160 mW for the free-running regime at the same pumping level has been obtained with a slope efficiency of 26% with respect to the incident pump power. Using a Tm:KYW sample with broadband antireflection coatings and dichroic laser resonator mirror, the first Stokes component of Raman self-frequency conversion was observed at 2365 nm.