Blue light emission by a Pr : LiYF4 − laser operated at room temperature

Room‐temperature operation of a solid‐state laser has been achieved for the first time in the blue region using Pr : YLF. The 0.2% Pr : YLF crystal was longitudinally pumped at 444 nm using a pulsed dye laser. Laser emission was observed at 479 nm and required a pump‐energy density of 8 J/cm2 at threshold.