2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/85884We study the defect-induced nonlinear transmission of a periodic structure created by alternating slabs of two materials with positive and negative refractive index. We demonstrate bistable switching and tunable nonlinear transmission in a novel type of bandgap that corresponds to the vanishing average refractive index, and compare the observed effects for two types of the bandgaps.3 pages, 5 figures; significant changesOpticsMaterials SciencePattern Formation and Solitonstext