  We propose an infrared power switch based on an asymmetric high-Q microcavity
incorporating a metallic nanolayer in close proximity to a layer made of a
phase-change material (PCM). The microcavity is designed so that when the PCM
layer is in the low-temperature phase, the metallic nanolayer coincides with a
nodal plane of the resonant electric field component, to allow a high resonant
transmittance. As the light intensity exceeds a certain threshold,
light-induced heating of the PCM layer triggers the phase transition
accompanied by an abrupt change in its refractive index in the vicinity of the
transition temperature. The latter results in a shift of the nodal plane away
from the metallic nanolayer, rendering the entire microcavity highly reflective
over a broad frequency range. The nearly binary nature of the PCM refractive
index allows for the low-intensity resonant transmission over a broad range of
ambient temperatures below the transition point.
