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We demonstrate a narrow-linewidth linearly polarized 1645 nm Er:YAG laser, directly diode-pumped by a fiber-coupled 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 μJ 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 measured to be 1645.34 and 0.05 nm, respectively. This laser can be useful in the detection of atmosphere pollutants.

We demonstrate a potassium titanyl phosphate-based optical parametric oscillator (OPO) emitting at 1729 nm. A maximum output power of 1.56 W at 1729.4 nm is obtained with an original fundamental laser power of 5.48 W. The pulse with a pulse duration of 11.22 ns exceeds 3 mJ at a 500 Hz repetition rate. To our knowledge this is the highest energy output of an OPO laser emitting around 1.73 \mu m operating at a 100 Hz order of magnitude. This laser is primarily used for bond-selective imaging of deep tissue, a promising way for diagnosing vulnerable plaques in live patients.