Ultraviolet femtosecond laser sources at the 10-watt level

This research is to achieve high-power, high-beam-quality, and long-term stable third-harmonic generation (THG) of ultraviolet femtosecond lasers. Based on the principle of birefringent crystal pre-compensation, a third-harmonic generation system capable of efficiently compensating for spatiotemporal walk-off effects is designed. A comprehensive numerical model for three-wave coupling is established to optimize key parameters such as crystal length and fundamental wave energy distribution ratio. Experimentally, two LBO crystals are employed for second-harmonic generation (SHG) and sum-frequency generation (SFG), respectively. At a repetition rate of 200 kHz, maximum output powers of 22.5 W for green light and 10.6 W for ultraviolet femtosecond laser radiation are achieved, with a UV conversion efficiency of 26.5%. We have successfully realized a high-efficiency ultraviolet laser output with a power level of 10 watts.