Controlled generation of OAM-switchable vortex beams at 639 nm from a Pr3+: YLF laser

Abstract

In this paper, we reported and demonstrated a blue LD-pumped Pr3+: YLF laser for the controlled generation of orbital angular momentum (OAM) switchable vortex beams at 639 nm. To begin with, the quantitative tilt imbalance of the resonator was introduced to select the higher-order Hermite-Gaussian (HG) modes by utilizing the eigenvector method and introducing the concept of mode discriminant factor. Moreover, the mode converter, composed of two cylindrical mirrors, was applied to convert the Hermite- Gaussian (HG) modes into the Laguerre-Gaussian (LG) modes with the OAM. Then, the experiment setup was built to validate the correctness and effectiveness of the quantitative tilt imbalance. The results showed that the vortex beams with OAM of 0 to ±14 at 639 nm can be obtained by adjusting the tilted angle of the output mirror, which agreed well with the simulation results, and the slope efficiencies of the vortex beams with OAM = 1, 2, and 3 are 11.64%, 8.01%, and 6.05%, respectively. The method provided a viable solution for the generation of visible vortex beams with switchable OAM from the Pr3+: YLF laser.