Nonlinear tunneling in a fiber guide array resonator.

A fiber guide array resonator is proposed and shown to obey a nonlinear Schrödinger model in a square well potential with nonlinearity defocusing inside the well and focusing outside. This model is proved to possess nonlinear states which are i) continuous extensions of the linear eigenstates, ii) remarkably stable up to a threshold amplitude, iii) unstable at the threshold where nonlinear tunneling occurs by gap soliton emission outside the well. This allows in particular to obtain soliton formation by constant wave irradiation of the fiber guide array resonator. An explicit analytic expression of the threshold is given in terms of the well size for each level.