Loss-induced on/off switching in a channel add/drop filter

We introduce a mechanism that provides an on/off switching capability in channel add-drop filter structures, These filters consist of two waveguides, a bus and a drop, coupled through a frequency-selective element. The switching functionality is achieved by incorporating materials with variable absorbing characteristics into the coupling element. When the variable material displays minimum absorption, the frequency channel of interest is transferred completely from the bus waveguide to the drop waveguide. When the variable material displays maximum absorption, the frequency channel is not transferred and remains essentially undisturbed in the bus waveguide. We also discuss the practical feasibility of realizing this approach using either electrical or mechanical means.