Passive Q-switching of a Tm3+:LiYF4 waveguide laser by Cr2+:ZnSe and Co2+:ZnSe saturable absorbers

Abstract A Tm3+:LiYF4/LiYF4 channel waveguide laser produced by Liquid Phase Epitaxy and diamond-saw dicing is passively Q-switched by Cr2+:ZnSe and Co2+:ZnSe saturable absorbers. For Cr2+:ZnSe, the laser generated a maximum average output power of 0.59 W at 1876.5 nm with a slope efficiency of 36.1% (with respect to the absorbed pump power) and a linearly polarized output (π-polarization). The pulse characteristics (duration/energy) were 9 ns/2.1 μJ at a repetition rate of 0.29 MHz. The laser performance was modelled within a “slow” saturable absorber model showing good agreement with the experiment. We also revisited Co2+:ZnSe for passive Q-switching applications in the spectral range of ~2 μm. It allowed to operate the laser in a high-repetition-rate regime (0.91 MHz) while preserving the benefits of short pulses (30 ns/0.9 μJ). For Co2+:ZnSe, the average output power of the waveguide laser reached 0.81 W with a record-high slope efficiency of 49.6%.