26ps pulses from a passively Q-switched microchip laser

Abstract

Short-pulse laser systems have found entry into industrial micro material fabrication processes on a large scale during the past ten years. In the same way the demand of simple, compact and cost-efficient seed sources has grown. The physical parameters needed for short-pulse laser processing range between a few femtoseconds to some ten picoseconds at repetition rates of up to 1 MHz. Up to now these laser systems are based on high repetition rate oscillators and regenerative amplifiers. These systems are rather complex and expensive. In contrast a Q-switched microchip laser in combination with a single pass amplifier permits a much simpler approach. In the following we present a 50 μm Nd³⁺:YVO₄ microchip laser that is passively Q-switched by a semiconductor saturable absorber mirror. To overcome handling problems of the small crystal dimensions the 50 μm 3 at.-% doped Nd³⁺:YVO₄ crystal is optically bonded to an undoped YVO₄ crystal of a length of about 500 μm. The system provides pulse widths around 26 ps at a repetition rate of up to 0.9 MHz. The average output power is 15 mW at a wavelength of 1,064 nm, at an energy of 17 nJ. We will discuss the prospects and limits in terms of pulse width, repetition rate, output power, and system stability. The experimental data are compared to theoretical calculations.