Nanosecond, high peak power vortices generated in a passively Q-switched microchip laser

Abstract Nanosecond high-peak-power vortex-pulsed lasers show application in material processing, high-capacity optical communication, and quantum information processing. This study generated nanosecond, high-peak-power LG 0,1 vortex beams in a Yb:YAG/Cr 4+ :YAG passively Q-switched microchip laser (PQSML) pumped with an annular beam. An annular pump beam, irradiated at 940 nm, was shaped by aligning the uneven distribution of light emitters in a laser diode bar and emitting light from a multimode fiber. An optical coupling system was constructed using two spherical lenses ( f = 8 mm). The diameter was 80 μm at the focus spot. A linear increase in the average output power was achieved with a slope efficiency of 12.4%. The average output power of the vortex laser was 256 mW at an incident pump power (P in ) of 5.7 W. Vortices oscillated in a single-longitudinal mode when P in < 4.2 W, and the laser attained a pulse width of 2 ns and peak power of 28 kW. Conversely, when A P in > 4.2 W, vortices oscillated in a multi-longitudinal mode, and the laser attained a peak power of approximately 19 kW and pulse width of less than 2.2 ns. The vortex laser with a pulse energy of 42 μJ operated at a repetition rate of 6.3 kHz. A high-beam-quality and high-purity vortex-pulsed laser generated in the compact PQSML shows potential applications in integrated photonics, such as quantum communication and optical trapping.