Efficient 320 nm continuous-wave ultraviolet Pr:LiYF laser via optimized pump beam reshaping.

Numerous studies have found that the mode overlap efficiency affects the output power of lasers, with higher mode overlap efficiency leading to greater output power under the same conditions. We report a pump beam reshaping system that adjusts the waist size and beam divergence angle of focused laser diode (LD) pump beams to enhance the overlap efficiency between the pump beam and the resonator mode. This results in a Pr:LiYF laser with an output power of 4.33 W and a slope efficiency of 51.9% at 640 nm. After frequency doubling using a single lithium triborate (LBO) crystal, a compact and efficient laser with 320 nm output power of 1.91 W and slope efficiency of 23.1% is achieved. This work provides a feasible approach for realizing efficient ultraviolet lasers using an LD pump.