Narrow‐linewidth injection‐locked Ho:YAG laser by using thulium‐doped fiber laser as pumping source

Abstract We demonstrated a narrow‐linewidth Ho:yttrium aluminum garnet (YAG) injection‐locked laser by using a 1908 nm thulium‐doped fiber laser as a pumping source to generate 2.09 μm single‐frequency pulses. A compact single‐longitudinal‐mode nonplanar ring oscillator (NPRO) based on Ho:YAG material with a beam quality factor of 1.01 at the central wavelength of 2090.91 nm was considered as the seed source. In the experiment, the pulse energy of 3.6 mJ with a pulse width of 161.6 ns from single‐frequency Ho laser was achieved at a pulse repetition frequency (PRF) of 100 Hz. The linewidth of the single‐frequency pulse spectrum monitored through the heterodyne method was approximately 1.9 MHz at the lowest Ho laser energy.