Simple CW-UV generator by SHG technique with double-clad Pr-doped waterproof fluoro-aluminate glass fiber laser

UV light sources have many applications in science and technology. Generation of ultraviolet light from near-infrared lasers requires twice frequency conversion processes, such as the third- or fourth-harmonic generations (THG or FHG). In recent years, however, due to the increase in power of InGaN laser diode (InGaN-LD) and the emergence of primary visible solid-state lasers, it has become possible to generate ultraviolet laser light by once second-harmonic generation (SHG) [1] . In order to develop a more compact and simpler UV laser light source, we have been developing a single-mode primary visible fiber laser. Firstly, we successfully drew a single-mode double-clad structured Pr-doped waterproof fluoride glass fiber (Pr:SM-DC-WPFGF) and demonstrated laser oscillation with the power of 251.7 mW in 2016 [2] , then output power was improved to 2-W in 2019 [3] . We think that this kind of visible light source can be applied for a generation of UV laser.