Comparison of high average-power femtosecond green and ultraviolet laser emissions generated by K3B6O10Br and K3B6O10Cl nonlinear crystals

We investigate the second harmonic generation (SHG) and third harmonic generation (THG) processes of femtosecond (fs) laser that occurred in type Ⅰ phase-matched K3B6O10X (X = Cl, Br; KBOC and KBOB) crystals. The high average power of 515 nm green and 343 nm ultraviolet (UV) fs lasers output were efficiently generated from these two crystals with an incident fundamental 773 fs 1030-nm laser source. Experimental results show that the highly effective nonlinear coefficient of the KBOC crystal causes higher harmonic conversion efficiency than that of KBOB crystal in the same fundamental laser parameters. The average power of 10.4 W 515 nm green and 4.6 W 343 nm UV lasers output were obtained from two pieces of 4.5 mm KBOC crystals, corresponding to 42.3 % and 19.7 % high optical conversion efficiency respectively, without temporal pulse walk-off time compensation between 1030 nm and 515 nm laser pulses. Our research will stimulate in-depth research on nonlinear frequency conversion in nonlinear optical systems and have potential applications in future applications.