Frequency doubling with KNbO_3 in an external cavity

Potassium niobate is employed in an external resonator to generate single-frequency tunable radiation near 430 nm. For excitation with 1.35 W of power from a cw titanium–sapphire laser, 0.65 W of blue light is produced. A simple model has been developed to account for thermal lensing in the nonlinear crystal.