SPATIAL GAP SOLITONS IN PERIODIC NONLINEAR STRUCTURES

Self-focusing effects in periodic leaky-wave coupled (antiguided) and evanescent-wave coupled array structures are analyzed for what is to o ur knowledge the first time. The results obtained can be explained in terms of spatial gap solitons. For infinite-extent arrays of antiguide s it is found that (for interelement-spacing values), below the in-pha se-mode resonance, self-focusing occurs with increasing light intensit y even when the medium is intrinsically self-defocusing (i.e., negativ e nonlinearity). If the medium has positive nonlinearity the analysis shows that antiguided arrays possess either self-focusing or self-defo cusing properties depending on the parameters of the structure, wherea s evanescent-wave in-phase coupled arrays always have self-focusing pr operties.