3.65 W of 335 nm cw Generation In a Pr³⁺:LiYF₄ Laser Pumped By a Fiber Coupled Blue LD Module

We report on the stable 670/335 nm Pr³⁺:LiYF₄ (Pr: YLF) continuous-wave (CW) laser. A fiber-coupled InGaN laser diode (LD) emitting at 444 nm is used as the pump source, effectively increasing the pump power. Using a straight cavity structure, we achieved a maximum output power of 7.4 W at 670 nm with a pump power of 37 W. Second-harmonic generation (SHG) of the 670 nm laser was achieved using a lithium borate (LBO) crystal. To avoid damage to the gain material by the UV laser, a V-folded cavity structure is adopted for intracavity frequency doubling. With an incident pump power of 32 W, more than 3.65 W was obtained at 335 nm with an optical-to-optical conversion efficiency of 11.4%, and the output power stability in one hour is better than 0.5%. To the best of our knowledge, this is the first research on Pr: YLF laser emitting at 335 nm. This research has high application value in fields such as photobiology and semiconductor detection.