Intracavity Frequency Doubling in a Femtosecond Ti:sapphire Laser Using Lithium Triborate and Beta-Barium Borate

The intracavity frequency-doubling characteristics of LiB 3 O 5 (LBO) and β-BaB 2 O 4 (BBO) in a femtosecond Ti:sapphire laser were investigated to generate efficiently blue wavelength, femtosecond pulses. At a repetition rate of 80 MHz, 24 fs pulses with a spectral bandwidth of 13.7 nm around 422 nm for LBO, and 29 fs pulses with a spectral bandwidth of 10.4 nm for BBO, were produced. The minimum pump power to start the mode locking of Ti:sapphire laser with the doubling crystal was about 2.5 W. With a laser pump power of 5 W, the blue output power of 86 mW with an internal conversion efficiency of about 3.3% from LBO and that of 114 mW with 4.5% from BBO were obtained.