Focusing effects on blue generation by frequency doubling of femtosecond pulses in KNbO/sub 3/

摘要

We show that the nonlinear or blue-induced IR absorption in KNbO/sub 3/ leads to a significant temperature rise in the femtosecond experiments, which must be accounted for in setting the phase-matching conditions. We investigate, for the first time to our knowledge, the focusing dependence of the phase-matching temperature. We find that the optimum phase-matching temperature significantly depends not only on the input power but also on the focusing.