We show that, in the high wave-vector-mismatch (cascading) limit, the well-known paraxial description of parametric frequency conversion in quadratic media entails effective lensing effects, which can have a self-focusing or a self-defocusing nature, critically depending on the mismatch sign, the selected wave, and the launching condition (second-harmonic generation or downconversion). Numerical and experimental evidence of this behavior is reported.
© 2002 Optical Society of America
(190.3270) Nonlinear optics : Kerr effect
(190.4410) Nonlinear optics : Nonlinear optics, parametric processes
(190.4420) Nonlinear optics : Nonlinear optics, transverse effects in
(190.4970) Nonlinear optics : Parametric oscillators and amplifiers
C. Conti, S. Trillo, P. Di Trapani, J. Kilius, A. Bramati, S. Minardi, W. Chinaglia, and G. Valiulis, "Effective lensing effects in parametric frequency conversion," J. Opt. Soc. Am. B 19, 852-859 (2002)