25 mJ, 5 KHz, 3 ns, Nd:YAG discrete path slab amplifier using a hybrid resonator.

We report what we believe to be potential improved performance for a Nd:YAG discrete path slab amplifier configuration based on a hybrid resonator system. The amplifier is driven by a Q-switched 0.3 mJ nanosecond oscillator that generates an initial laser pulse at a repetition rate of 5 KHz and has beam quality of M2<1.3. The input pulse makes 12 passes through the slab amplifier to yield 25 mJ output pulse energy at the absorbed pump power of 878 W. A corresponding optical-to-optical efficiency of 14.3% was obtained, and the beam quality factors M2 in the unstable and stable direction were 1.7 and 1.5, respectively. No detectable signs of amplified spontaneous emission were observed.