  A localized defect mode in a photonic-layered structure develops nodal
points. Placing a thin metallic layer at such a nodal point results in the
phenomenon of induced transparency. We demonstrate that if this nodal point is
not a point of symmetry, then even a tiny alteration of the permittivity in the
vicinity of the defect suppresses the localized mode along with the resonant
transmission; the layered structure becomes highly reflective within a broad
frequency range. Applications of this hypersensitive transport for optical
limiting and switching are discussed.
