Generation of 7.6-W blue laser by frequency-tripling of a Nd:YAG laser in LBO crystals

High-power, quasi-continuous wave blue laser output is obtained by intracavity frequency-tripling of a 1.319 µm Nd:YAG laser with two LiB3O5 crystals. The conversion efficiency and the stability of the blue laser output power at 439.7 nm were both improved through the suppression of 1.338 µm operation by means of a thin YAG etalon. 7.6 W average power at 439.7 nm was demonstrated at 5 kHz with pulse width of 170±10 ns (FWHM). The beam quality factor M2 is 12±2 in both horizontal and vertical directions. The long-term stability of the blue light is better than 1% at an output of 6 W for 200 operation hours.