Passively Q-switched Nd:YAG/ICTA laser at 561 nm

We demonstrate a compact diode-pumped passively Q-switched Nd:YAG laser operating at the wavelength of 1123 nm, and its frequency-doubling into 561 nm by using a KTA crystal. The laser makes use of a single emitter 2.5 W laser diode, and at 561 nm puts out a 12 kHz pulse train of 4 ns, 5 mu J pulses with an average power of 55 mW. The high pulse energy of the 1123 nm laser allows us to study the saturation of 1123 nm absorption in the Cr(4+):YAG Q-switch crystal. The ratio of the ground-state and excited-state absorption cross-sections is found to be sigma(GSA)/sigma(ESA) = 5.5 +/- 0.9. 2008 Elsevier B.V. All rights reserved.