High-power second-harmonic generation with picosecond and hundreds-of-picosecond pulses of a cw mode-locked Ti:sapphire laser.

A cw mode-locked Ti:sapphire laser was efficiently frequency doubled with a lithium triborate crystal in an external enhancement cavity. Second-harmonic output powers of 1.28 W and 860 mW have been generated at 399 nm with fundamental pulse widths of 1.5 and 320 ps, respectively. At the 1.5-ps pulse width the conversion efficiency was 75%. The spectral width of the 320-ps pulses, produced by modification of a laser cavity, is as narrow as the bandwidth of a normal cw, multimode, narrow-bandwidth Ti:sapphire laser. The frequency-doubled output can be thus used as a high-power, narrow-bandwidth light source in the UV region.