Generation of one-dimensional vortex-arrays with tunable singularity and high peak power in a passively Q-switched microchip laser

Abstract

One-dimensional (1D) vortex-arrays with multiple-singularity aligning along a line are flexible for microparticle manipulation, high capacity storage, material processing. Moreover, a high peak power one-dimensional vortex-array with large singularity enables assemble processing. The development of a miniature laser to directly generate one-dimensional vortex-array with tunable singularity is of great value for practical applications. However, solid-state lasers for this purpose was limited by the low power, low efficiency and less singularity achieved. Here, we demonstrate a simple and robust method for directly generating one-dimensional vortex-array with singularity tunable upon to 4 in a tilted Nd:YAG/Cr4+:YAG composite crystal passively Q-switched (PQS) microchip laser, irradiated by a decentered annular beam (DAB). The singularity of one-dimensional vortex-array can be tuned from 1 to 4 by controlling the offset of collimating lens, Δx. The average output power of one-dimensional vortex-array with 4 singularities is 0.76 W at Pin = 5.66 W, the optical conversion efficiency is 13.4%. One-dimensional vortex-array with 4 singularities processes pulse width of 3.5 ns, peak power of 5.56 kW. The achieved results suggest the potential that DAB can be used a practical pump beam in PQS microchip laser for generating nanosecond, high peak power one-dimensional vortex-arrays with tunable singularity.