Broadband ultrafast ultraviolet laser output by using β-BaB2O4 crystal

In this paper, a broadband ultrafast ultraviolet (UV) laser was generated through sum-frequency method with beta-BaB2O4 (BBO) crystal by using a femtosecond (fs) Ti:sapphire laser as the fundamental laser source. We studied the influence of the power ratio between the fundamental frequency and second harmonic laser beams on output power and conversion efficiency of UV laser. The time delay method was used to change the optical path difference in the sum-frequency generation (SFG). At the same time, the cutting angle of the crystal was optimized and the effect of different focal lengths of lenses on the experimental results was studied. Finally, we obtained a tunable UV laser beam with a tuning range from 226.7 nm to 360 nm generated by the BBO crystal. The laser had high conversion efficiency, and the maximum output power was 540 mW at 270 nm.