178  mJ single-frequency nanosecond Tm,Ho:YAG amplifier

A high-energy single-frequency nanosecond diode side-pumped Tm, Ho-codoped yttrium aluminum garnet (Tm,Ho:YAG) laser at 2.09 µm is demonstrated. The laser is designed as a master oscillator and power amplifier (MOPA) system and includes a 2.09 µm single-frequency seed source, an injection-amplifier with a folded "twisted-mode" cavity, and a two-stage amplifier. A maximum single-frequency output energy of 178 mJ with a pulse width of 235.4 ns and a pulse repetition rate (PRR) of 5 Hz is achieved. The linewidth of the single-frequency pulse is measured to be 2.79 MHz by a heterodyne beating technique. The M² factors are measured to be 1.72 and 1.67 in the x and y directions, respectively.