EFFECTIVE SUM FREQUENCY PULSE-COMPRESSION IN NONLINEAR CRYSTALS

Sum frequency (SF) generation in the case of strong energy exchange and group velocity mismatch may lead to very effective SF pulse compression. The conditions needed for effective compression of SF pulses are found. It is possible to produce SF pulses the duration of which is sufficiently smaller than the initial duration of the pump pulses and almost the total energy of the pump pulses is converted into the SF wave. By this technique the 3 ps pump pulses (lambda = 1.06-mu-m) can be converted into a almost-equal-to 3 cm KDP crystal to a 200 fs SF pulse (lambda = 0.53-mu-m) if the intensity of the pump is almost-equal-to 3 GW/cm2.