Cylindrical vector-polarized vortex pulses from a passively Q-switched laser are demonstrated. Pump radiation reshaped into a size-controlled annular profile via circular Dammann grating produces an efficient excitation of the LG01 mode. The YAG / Nd : YAG / Cr4 + : YAG composite crystal structure is found to reduce the Q-switching threshold and significantly suppress thermal damage, thus allowing ability to obtain a passively Q-switched pulse. The threshold pumping power is found to be 4.35 W, with a slope efficiency of 23.1%. A maximum peak power of 3.24 kW, maximum pulse energy of 53.46 μJ, pulse width of 17.5 ns, and repetition rate of 2.695 kHz are obtained. Furthermore, a radially polarized output with a polarization degree of 88.9% is confirmed. Finally, mode and polarization tuning are also discussed.

中文翻译：

---

被动Q使用圆形达曼光栅-switched径向偏振模式LG01激光

演示了来自被动调Q激光器的圆柱矢量偏振涡旋脉冲。通过圆形达曼光栅将泵浦辐射整形为尺寸受控的环形轮廓，可有效激发LG01模式。发现YAG / Nd：YAG / Cr4 +：YAG复合晶体结构可降低Q开关阈值并显着抑制热损伤，从而具有获得被动Q开关脉冲的能力。发现阈值泵浦功率为4.35 W，斜率效率为23.1％。获得的最大峰值功率为3.24 kW，最大脉冲能量为53.46μJ，脉冲宽度为17.5 ns，重复频率为2.695 kHz。此外，确认了偏振度为88.9％的径向偏振输出。最后，还讨论了模式和偏振调谐。