Optical frequency mixing through cascaded second-order processes in β-barium borate

Abstract

We show that the large effective optical nonlinearity, which is produced by cascaded second-order processes, allows us to accomplish the frequency conversion of a signal pulse with a pump pulse of moderate intensity. In a 1 cm long β-barium borate crystal, the cascaded effect enhances by 5 orders of magnitude the efficiency of the frequency mixing process. The enhancement is larger than 104 even in non-phase-matched condition for the intermediate second-harmonic field, when the imaginary part of the induced nonlinear susceptibility is negligible.