High-energy Q-switched operation of a fiber-laser-pumped Er:YAG laser

A high-energy Q-switched Er:YAG laser in-band pumped by an Er,Yb co-doped fiber laser is reported. A simple two-mirror multi-mode resonator incorporating an electro-optic Q-switch and a multi-Brewster-plate polarizer was employed, together with a simple compensation scheme to reduce the depolarization loss due to thermally induced stress birefringence in the Er:YAG crystal at high pump powers. The laser yielded Q-switched pulses at 1617 nm with 30.5-mJ pulse energy and <20-ns pulse duration (FWHM) at 20-Hz repetition rate, corresponding to a peak power of >1.5 MW for 55 W of pump power at 1532 nm. The prospects for further improvement in Q-switched performance are discussed.