Vortex Laser using a Sagnac Ring as an Output Coupler

点击翻译按钮获取中文摘要

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.