Injection-seeded Ho:YAG laser at room temperature by monolithic nonplanar ring laser

We demonstrated a 1.91 μm-pumped, injection-seeded Ho:YAG laser operating at room-temperature. Single-frequency, nearly transform-limited Q-switched operation of the laser was achieved by injection-seeding. Using a monolithic Ho:YAG nonplanar ring oscillator (NPRO) as the seed laser, the 11 mJ single-frequency Q-switched Ho:YAG laser at 110 Hz with a pulse width of 110 ns was obtained. The beam quality factor was measured to be M 2 < 1.1 by the traveling knife-edge method at the maximal output level. We measured the pulse spectrum, half-width of which was 4.8 MHz, by a heterodyne technique.