Generation of wavelength- and OAM-tunable vortex beam at low threshold

• Published in: Optics express Vol. 26; no. 14; pp. 18164 - 18170
• Main Authors: Wang, Sha, Zhang, Shu-Lin, Li, Ping, Hao, Mei-Hui, Yang, Huo-Mu, Xie, Jian, Feng, Guo-Ying, Zhou, Shou-Huan
• Format: Journal Article
• Language: English
• Published: United States 09.07.2018
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.26.018164

Wavelength- and OAM- tunable laser with large tunable range is the key source for the application in large capacity optical communications. In this paper, we demonstrate a wavelength- and OAM-tunable vortex laser in a 1.2 W single mode fiber coupled LD pumped Yb:phosphate laser. A z-type cavity has been used to precisely control the laser mode diameter. A thin film polarizer (TFP) is inserted to finely control the intra-cavity loss and tune the wavelength. Corresponding laser fundamental mode to pump beam ratio has been optimized to decrease the pump threshold for high order HG mode running. A pair of cylindrical lenses has been used to convert the HG mode to vortex output. The vortex beam with OAM-tunable range from 1ħ to 14 ħ with wavelength tuning range of ~36.2 nm for LG vortex beam, and ~14.5 nm for LG vortex beam at pump power of only 1.2 W have been realized, which is the largest tuning range of both OAM and wavelength at ~1 W pump power range to the best of our knowledge.