Frequency Doubling of Tunable Ti:sapphire Laser with KNbO3 in External Cavity

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Abstract
Frequency doubling of a tunable Ti:sapphire laser is demonstrated using a noncritically phase-matched KNbO3 crystal in an external enhancement cavity. A narrow linewidth Ti:sapphire laser is constructed and its center frequency is locked to a reference interferometer. The optimum phase-matching condition is achieved by temperature-tuning the KNbO3 crystal. Tunable blue light between 426.8 nm and 433.6 nm is successfully generated with the highest conversion efficiency of 31% for 470 mW pump power. It is found that the optimum phase-matching temperature depends on the pump power as well as the pump wavelength resulting from the thermal effect.