High efficient second harmonic at 416 nm and fourth harmonic generation at 208 nm in compacted all-solid-state Ti:sapphire laser

Second harmonic and fourth harmonic are generated from Ti:sapphire laser pumped by a diode-Q-switched, doubling-frequency YLiF, (YLF) laser at 527 nm. The nonlinear crystal LiB₃O₅ (LBO) is used to generate the second harmonic wave in the Ti:sapphire cavity at I-phase match with birefringent filter, and β-BaB₂O₄ (BBO) crystal is used to generate ultraviolet at 208 nm. Maximum average power of 610 mW at 416 nm, and 64 mW at 208 nm are obtained at 1 kHz repetition rate when the pumping power is 3.8 W. The high conversion efficiency is attributed to the birefringent filter which narrows the linewidth of Ti:sapphire laser. Considering mode-competition and gain saturation, the dependence of line width of Ti:sapphire laser with birefringent filter (BF) on pumping power is investigated in theory and experiment, and there is good agreement between theoretical and experimental results.