Harmonic generation at high repetition rate with Q-switched Nd:YVO 4 lasers

Abstract

A variety of applications require short, energetic laser pulses delivered at high repetition rate. These include micro-machining, range finding, and scientific applications such as amplifier pumping. An important advantage provided by diode-end-pumping of solid state lasers is that this type of geometry allows the generation of short, energetic, Q-switched pulses at high repetition rate. The high peak power of such pulses facilitates harmonic generation. In this paper, we describe a high average power, high repetition rate Q-switched Nd:YVO<SUB>4</SUB> laser, pumped by a fiber-coupled diode bar. The laser provides pulses of excellent spatial quality at repetition rates up to 100 kHz, average power 3-4 W, and durations of 8 to 20 nsec. The near-diffraction-limited beam and the high peak power allow efficient harmonic generation at high repetition rates. Second harmonic generation is achieved in non- critically-phase-matched LBO with a conversion efficiency of 55% at 20 kHz, providing an average power of 1.75 W at 532 nm. third harmonic generations (to 355) in LBO has been achieved with > 20% efficiency, resulting in an ultraviolet average power of 0.65 W at 20 kHz.