Picosecond pulsed high-peak-power lasers

Abstract

Recent trends in the use and development of advanced schemes of high peak-power picosecond lasers are reviewed. Pulsed (pulsed repetitive) high-peak-power picosecond lasers of millijoule and multi-millijoule single pulse level operating at reasonably high repetition rates are required in a number of scientific and technological applications. The developed approach utilizes active-passive mode-locked and negative feedback controlled oscillator that provides generation of stable, closed to transform limited pulses with pulse duration of 25 ps (with Nd:YAG) and 16 ps (with Nd:YLF). Oscillator—regenerative amplifier scheme based on the common diode-end-pumped laser crystal generates pulses up to 1.2 mJ with Nd:YAG and up to 2 mJ with Nd:YLF crystals. Two-pass Nd:YAG diode-end-pumped amplifier provides output radiation of 4 mJ single pulse energy at 300 Hz repetition rate, that was converted in the second harmonic with more than 60% efficiency. Numerical modeling allows adequate description of the pulse formation process. Using 300 μm thickness Fabry-Perot etalons with different reflection coatings inside oscillator provided generation of pulses with increased up to 120, 180 and 400 ps durations. Aberrative character of thermal lens and mode structure at end-pump geometry were analyzed using decomposition on embedded beams. It was supposed that resonator stability range might be enhanced owing to adaptive action of the aberration lens. Optimized pulse diode-end-pumped double-pass amplifier schemes utilizing Nd:YLF, Nd:YAG and Nd:YVO4 crystals are discussed.