Single- and dual-tube He–Ne lasers for high-power excitation of LG01-mode vortex beam

In this study, aiming to extend the power of LG _01 -mode vortex light at 632.8 nm, the commercial He–Ne laser was upgraded to dual-tube gain geometry with the assistance of an intracavity spot defect for spatial filtering. We investigated the impact of using single and double He–Ne gas gain tubes on the powers of vortex laser output, and achieved a maximum 4.7 mW power of LG _01 -mode vortex light, corresponding to an optical–optical conversion efficiency of 39.2% and making it the highest power of vortex light obtained in He–Ne laser up to now.