Liang Hsing-Chih, Lin Han-Yu
Opt Lett. 2020 Apr 15;45(8):2307-2310. doi: 10.1364/OL.390278.
We propose a theoretical model to generate the resonant geometric modes localized on ray periodic trajectories with orbital angular momentum. Based on the numerical analysis, we realize resonant geometric modes in the off-axis pumped degenerate cavity ${\rm Nd}{:}{{\rm YVO}_4}$Nd:YVO lasers with an external mode converter. The experimental results reveal that laser output modes display the planar geometric modes when the off-axis displacement is sufficiently large, and the cavity length is set to satisfy the degenerate conditions. To generate the vortex beams, the planar geometric modes are transformed into circular geometric modes. Finally, the resonant geometric modes with large orbital angular momentum (OAM) can be generated from converting the circular geometric modes with an axicon lens. The experimental results are performed to approve the theoretical analyses.
我们提出了一个理论模型，以产生局域于具有轨道角动量的射线周期轨迹上的共振几何模式。基于数值分析，我们在带有外部模式转换器的离轴泵浦简并腔 ${\rm Nd}{:}{{\rm YVO}_4}$ 钕:钇钒石榴石激光器中实现了共振几何模式。实验结果表明，当离轴位移足够大且腔长设置为满足简并条件时，激光输出模式呈现平面几何模式。为了产生涡旋光束，将平面几何模式转换为圆形几何模式。最后，通过用锥透镜转换圆形几何模式，可以产生具有大轨道角动量（OAM）的共振几何模式。实验结果证实了理论分析。
