Doubly Q-switched single longitudinal mode Nd:YAG laser with electro-optical modulator and Cr4＋:YAG

An electro-optical modulator (EOM) and Cr4＋:YAG saturable-absorber-based doubly Q-switched Nd:YAG laser at 1.06μm with single-longitudinal-mode (SLM) output was demonstrated. The spatial-hole-burning suppression and cavity axial-mode selection were provided by a twisted-mode technique and resonant-reflector-mediated SLM operation. The Cr4＋:YAG initial transmittance (T0) affected the pulse profile, pulse energy, and laser spectra, which were analyzed theoretically and experimentally. Consequently, the laser output obtained an SLM rate of 96.2% with a symmetry factor of 0.64 when T0 was 6.2%. The results indicate that symmetric and SLM laser pulse can be obtained in a double Q-switched laser by adjusting the cavity loss according to T0. Compared with a solely Q-switched laser, the double Q-switches of EOM and Cr4＋:YAG provide a practical route toward the generation of a symmetric temporal profile and SLM operation.