High-energy, single-frequency, Q-switched Er:YAG laser with a double-crystals-end-pumping architecture

A high-energy, single-frequency, injection-seeded, Q-switched Er:YAG laser oscillating at 1645 nm is demonstrated. For obtaining high output energy, a double-crystals-end-pumping architecture is utilized. The maximum output energies of single-frequency pulses are 12.84 mJ, 16.87 mJ, and 20.3 mJ at pulse repetition rates of 500 Hz, 300 Hz and 200 Hz, respectively. Correspondingly, the pulse widths are 162 ns, 125 ns, and 110 ns, respectively. The half-width of the pulse spectrum at the pulse repetition rate of 200 Hz is 4.59 MHz, measured by using the heterodyne technique, which is 1.14 times transform limited. To the best of our knowledge, 20.3 mJ is the highest energy obtained from a single-frequency, injection-seeded Er:YAG laser.