Abstract
The nonresonant interaction of nonlinear waves in one-dimensional photonic band gap materials is investigated analytically and numerically. We derive highly accurate analytical formulae that determine the phase shift experienced by nonlinear waves during nonresonant interaction. The case of nonresonant interaction of Bragg and gap solitons is considered in detail. We show that the phase shift of the interacting solitons should be experimentally observable, and can be used as a probe to determine the existence and the parameters of a gap soliton.