OPTICAL FREQUENCY MIXING THROUGH CASCADED 2ND-ORDER PROCESSES IN BETA-BARIUM BORATE

We show that the large effective optical nonlinearity, which is produc ed by cascaded second-order processes, allows us to accomplish the fre quency conversion of a signal pulse with a pump pulse of moderate inte nsity. In a 1 cm long beta-barium borate crystal the cascaded effect e nhances by 5 orders of magnitude the efficiency of the frequency mixin g process. The enhancement is larger than 10(4) even in non-phase-matc hed condition for the intermediate second-harmonic field, when the ima ginary part of the induced nonlinear susceptibility is negligible.