An optical power or energy-switching device, comprising an optical waveguide having an input section and an output section, the two sections forming a pair of opposed surfaces extending transversely through the axes of said waveguide sections, and a thin, substantially transparent layer of electrically conductive material disposed between said opposed surfaces, said layer of conductive material forming a plasma when exposed to optical signals propagating within said optical waveguide with an optical power level above a predetermined threshold, said plasma damaging said opposed surfaces sufficiently to render said surfaces substantially opaque to light propagating within said optical waveguide so as to prevent the transmission of such light.