Diode-pumped 250-W zigzag slab Nd:YAG oscillator–amplifier system

A laser-diode-pumped zigzag slab Nd:YAG master oscillator power amplifier (MOPA) system featuring high pulse energy and high average power was developed for pumping of an ultrashort-pulse laser system. The MOPA system consists of an oscillator, a preamplifier, two postamplifiers, and image-relay telescopes. The postamplifiers have an angle-multiplexed ring-type double-pass configuration. A pulse energy of 1.26 J and an average power of 251 W were obtained at a repetition rate of 200 Hz. The frequency-doubled power when a ${\mathrm{LiB}}_3{\mathrm{O}}_5$ crystal was used was 105 W at a repetition rate of 170 Hz. The intensity profiles of the fundamental and the second harmonic are nearly top-hat shaped and are suitable for pumping.