Diode pumped narrow linewidth linearly polarized passively Q switched 1645 nm Er

We demonstrate a narrow-linewidth linearly polarized 1645 nm Er:YAG laser, directly diode-pumped by a fibercoupled continuous-wave laser diode at 1532 nm. Passive Q-switching is realized by a few-layer graphene saturable absorber. A maximum polarized average output power of 3.13 W is achieved at 23.28 W incident pump power. A pulse energy of as much as 58.8 \mu J and pulse width of 4.21 μs are yielded at a 53.2 kHz pulse repetition rate. The spectrum and linewidth of the output beams are measure