Spectral characterization of second harmonic chi((2)) cascading phenomena.

The second harmonic generation in a thin β-barium borate crystal is used to measure χ(2) cascading phenomena in the spectral domain. The harmonic generation is induced by two pulses produced by spectrally filtering a femtosecond pulse and centered at the wavelength λ-Δλ and λ+Δλ. New spectral components appear in spectral density of both the fundamental and harmonic pulses. High order cascading phenomena are evidenced. In good agreement with theoretical predictions, for large phase mismatch the evolution of the spectra demonstrates the competition between cascaded χ(2) and χ(3) phenomena.