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Single-frequency operation of a resonantly pumped 1.645μm Er:YAG Q-switched laser

In this paper a resonantly pumped 1.645 μm injection-seeded single frequency Er:YAG Q-switched laser is reported. Firstly we introduce a monolithic Er:YAG non-planar ring oscillator (NPRO) developed by ourselves. The Er:YAG NPRO generated up to 10.5W 1.645 μm single frequency laser output power, with a slope efficiency of 60% and a linewidth of 18.6 kHz. The slave laser is a resonantly pumped Q-switched Er:YAG laser with a U-shape resonator and a 0.25 at.% Er:YAG crystal as the laser medium. When the pulse repetition rate was 1kHz, the Q-switched pulse energy was 5.4 mJ. Then one fraction of the single frequency laser beam from the Er:YAG NPRO was injection-seeded into a Q-switched slave laser. The Ramp-Hold-Fire technique was used to ensure the single frequency operation. Finally we obtained 1.645 μm single frequency Q-switched laser output with a pulse energy of 4.75mJ, pulse width of 336ns and pulse repetition rate of 200Hz, respectively.