Fourth harmonic all-solid-state low power ultraviolet laser by BBO crystal

A series of fourth harmonic generation(FHG) experiments based on a laser diode pumped acousto-optic Q-switched Nd:YVO2 laser employing KTP and BBO crystals was conducted. When the incident pump power of the green laser was 1.10 W and the beam waist radius was 12 μm, a 210 mW quasi-continuous UV laser pulse train was obtained and the power conversion efficiency was 19.1%. The results illustrate that for the same incident power, the FHG conversion efficiency varies with the waist width of the green laser beam. At last, we investigate the far field distributions of the UV laser in both o and e light vibration planes, and point that the elliptical shape distribution and the fringe pattern a caused by the different acceptance angles of the BBO crystal in the two planes.