Direct generation of vortex beams from an off-axis pumped all-solid-state laser

An off-axis pumped all-solid-state laser is proposed for the direct generation of Laguerre Gauss (LG) vortex beams with single handedness. The superposition states of the LG⁺₀₁ and LG^-₀₁ beams with opposite handedness are theoretically analyzed, as well as the influence of the gain medium longitudinal position on the superposition states in the laser cavity. In the experiments, an Nd:YVO₄ laser setup is designed to verify that moving the longitudinal position of the gain medium changes the amplitude components distribution of the LG⁺₀₁ and LG^-₀₁ beams. The vortex beam with single handedness is obtained when the gain medium is placed at d = 13 mm with the off-axis displacement Δx =  ± 0.5 mm and Δy =  ± 1.5 mm. In addition, by turning the off-axis displacements over, the handedness of the vortex beam is found to be reversed. The generated LG⁺₀₁ and LG^-₀₁ mode lasers have maximum output powers of 1.64 W and 1.57 W, with slope efficiencies of about 25.7% and 24.9% at a pump power of 6.36 W.