Selective resonant radiation in quadratic crystals via group-velocity dispersion

We consider the phenomenon of resonant radiation emitted by solitonlike wave packets in quadratic crystals and demonstrate the key role of the group-velocity dispersions, at the fundamental frequency and second harmonic, respectively, without any contribution from higher-order dispersions. In particular our approach allows us to predict a mechanism of primary resonance around the fundamental frequency component. Our theoretically predicted resonances are found to be in excellent agreement with numerical simulation of the propagation in a wide range of parameter values.