Miniaturized, high-power diode-pumped, Q-switched Nd:YAG laser oscillator-amplifier

A miniaturized, passively Q-switched Nd:YAG laser oscillator-power amplifier is reported, which is axially pumped by a compact, fiber-coupled, high-power, quasi-cw diode laser module. The pumping intensity of the oscillator crystal can be adjusted independently of the pumping intensity of the amplifier. This ensures that the oscillator pulse enters the amplifier when its maximum population density is reached. Furthermore, pulse bursts can be generated with a definite, adjustable number of single pulses. Maximum pulse energies of 8.4 and 22 mJ were achieved for a single pulse and for a pulse burst, respectively, at a pumping power of 470 W. The pulse widths were 2 ns, whereas the beam quality corresponded to M2<1.5. The laser is appropriate for scaling the power to the 10 MW range. Operation by using a 100 m pumping fiber was demonstrated.