Generation of soliton oscillations in nonlinear quadratic materials

We show analytically and numerically that the generation of long-lasting soliton oscillations in resonant chi(2) optical materials possesses a threshold for the amplitude of a fundamental wave. The persistent oscillations of solitary waves reported by Etrich et al. Phys. Rev. E 54, 4321 (1996)] are found to appear for finite values of the wave amplitude.