Powerful 3-μm lasers acousto-optically Q-switched with KYW and KGW crystals

We report, to the best of our knowledge, the first use of KY(WO₄)₂ and KG(WO₄) acousto-optical Q-switches in 3-μm powerful lasers. Q-switches of two different designs (normal incidence with antireflection coatings, and Brewster-angle cut crystals) operate in lasers based on Er:YAG, Cr:Yb:Ho:YSGG, and Cr:Er:YSGG laser crystals. Gain and lifetime of laser crystals significantly influence the regime of Q-switched generation. Er:YAG and Cr:Yb:Ho:YSGG lasers deliver pulses with 10.8 mJ and 17.5 mJ energy, respectively. Pulses with energy of 29.6 mJ and duration of 75 ns in the TEM₀₀ mode are obtained in a Cr:Er:YSGG laser. The energy is scaled up to 85.7 mJ in the two-stage master oscillator power amplifier system. Powerful laser systems of this kind are in the region of interest for pumping other mid-IR laser media (e.g., Fe:ZnSe and Fe:CdSe), OPOs, CO₂ lasers, and amplifiers. Preliminary experiments on microstructuring of transparent materials by the laser-induced backside wet etching method demonstrate the potential of such lasers to build the foundation for dye-free tissue and cell engineering concepts.