Low-threshold ultraviolet solid-state laser based on a Ce3+:LiCaAlF6 crystal resonator

A low-threshold solid-state UV laser using a whispering gallery mode (WGM) resonator constructed from UV transparent crystalline material is demonstrated. Using a Ce3+:LiCaAlF6 resonator, we observe broad bandwidth lasing (280-330 nm) with a low threshold intensity of 7.5×10(9) W/m(2) and an effective slope efficiency of ~25%. The lasing time delay dynamics in the pulsed operation mode are also observed and analyzed. Additionally, a LiCaAlF(6) WGM resonator with Q=2×10(7) at 370 nm is realized. The combination of this high Q and the small WGM mode volume significantly lowers the pump power threshold compared to traditional cavity designs, opening the door for both tunable continuous-wave and mode-locked operation.