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 our knowledge the first time. The results obtained can be explained in terms of spatial gap solitons. For infinite-extent arrays of antiguides it is found that (for interelement-spacing values), below the in-phase-mode resonance, self-focusing occurs with increasing light intensity even when the medium is intrinsically self-defocusing (i.e., negative nonlinearity). If the medium has positive nonlinearity the analysis shows that antiguided arrays possess either self-focusing or self-defocusing properties depending on the parameters of the structure, whereas evanescent-wave in-phase coupled arrays always have self-focusing properties.