Vortex Laser using a Sagnac Ring as an Output Coupler

涡旋激光束携带轨道角动量，导致中心相位奇异。轨道角动量使它们在粒子捕获、显微镜、分辨率成像、天文学、高速计量学、通信和量子信息等领域具有重要的应用价值。目前的涡流产生方法功率有限、昂贵且效率低。本项目研究了世界上第一台采用Sagnac干涉仪作为输出耦合器的涡旋激光器的设计，该涡旋激光器在多功率输出下产生了高质量的涡旋，特别是在2.3W输出功率下获得了M2x = 2.09和M2y= 2.07的左手涡旋。标准具被引入到SI中，这允许非常精确和容易地控制和反转y失准。切换旋向性导致没有功率损失，光束质量为M2x = 2.07和M2y = 2.04。两者都具有约19%的光学效率。透射曲线表明，SI在约16%的透射率下作为输出耦合器发挥最大效率。相应的功率曲线显示斜率效率为25%，仅略低于传统输出耦合器的28%。增益介质中的热透镜效应限制了输出的最大功率，这可以通过更好的腔设计来克服。这些结果表明，这种设计在需要高功率、高质量涡流并易于旋向控制的行业中具有潜力。展望未来，优化腔体以获得更高的功率是优先事项。将SI压缩并将其制造为单一元件将使其用途得到进一步探索，并为激光实验室之外的使用打开大门。涡旋激光器可以相对容易地被修改为脉冲操作和宽光谱涡旋产生。

Vortex laser beams carry orbital angular momentum (OAM), which results in acentral phase singularity. The orbital angular momentum makes them of interestin fields like particle trapping, microscopy, resolution imaging, astronomy, highspeedmetrology, communication and quantum information. Current methods ofvortex generation are power limited, expensive and ine_cient. A design for a world-_rst vortex laser, using a Sagnac interferometer (SI) as an output coupler has been investigated in this project.The vortex laser produces high quality vortices at multiple power outputs, notablya left-handed vortex with a beam quality of M2 x = 2.09 and M2y= 2.07 at 2.3W output power. An etalon was introduced into the SI, which allowed the ymisalignment to be controlled and reversed very precisely and easily. Switching thehandedness resulted in no power loss and a beam quality of M2x = 2.07 and M2y = 2.04. Both had an optical efficiency of approximately 19%. The transmission curve showed that the SI acted most efficiency as an output coupler at roughly 16% transmission. The corresponding power curve showed a slope efficiency of 25%, only slightly below that of a conventional output coupler at 28%. Thermal lensing effects in the gain medium limit the maximum power of the output, this can be overcome with better cavity design. These results suggest that this design has potential in industries requiring high power, high quality vortices with easy handedness control.Looking forward, optimising the cavity for significantly higher powers is a priority.Compacting the SI and manufacturing it as a single element would allow it's uses to be further explored and open up the door for usage outside of the laser lab. The vortex laser could relatively easily be modified for pulsed operation and broad spectrum vortex generation.