High-power, high repetition rate, tunable, ultrafast vortex beam in the near-infrared

TL;DR

This paper demonstrates a tunable, high-power, ultrafast vortex beam source in the near-infrared, achieved through optical parametric generation in a nonlinear crystal, with stable output and specific wavelength ranges.

Contribution

It introduces a novel high-power, tunable vortex beam source in the near-IR using single-pass optical parametric generation with detailed experimental results.

Findings

Signal vortex beam at 1433-1553 nm with 1.7 W power

Broadband idler radiation at 3379-4132 nm with 0.48 W power

Stable pulses of 637 fs at 78 MHz repetition rate

Abstract

We report on experimental demonstration of high power, ultrafast, high repetition rate vortex beam source tunable in the near-IR wavelength range. Based on single-pass optical parametric generation of Yb-fiber laser of vortex order lp=1 in a 50 mm long MgO doped periodically poled LiNbO3 crystal, the source produces signal beam in vortex profile of order ls=1 across 1433-1553 nm. Additionally, the source produces broadband idler radiation tunable across 3379-4132 nm in the Gaussian beam profile. We observed that the vortex profile of the pump beam is always transferred to the signal beam due to the highest overlapping integral among the interacting beams and the idler maintains a Gaussian spatial profile owing to conservation of orbital angular momentum in optical parametric processes. For pump power of 4.72 W, the signal and idler beams have maximum power of 1.7 W at 1509 nm and 0.48 W at 3625 nm respectively. The signal vortex beam has output pulses of width 637 fs at a repetition rate of 78 MHz. The signal (idler) has spectral width of 4.3 nm (129.5 nm) and passive peak-to-peak power fluctuation better than 3% (1.1%) over 30 minutes, respectively.