A microresonator is provided that incorporates a composite material comprising a polymer matrix and nanoparticles dispersed therein. The microresonator includes the composite material having a shape that is bounded at least in part by a reflecting surface. The shape of the microresonator allows a discrete electromagnetic frequency to set up a standing wave mode. Advantageously, the polymer matrix comprises at least one halogenated polymer and the dispersed nanoparticles comprise an outer coating layer, which may also comprise a halogenated polymer. Methods for making composite materials and microresonators are also provided. Applications include, for example, active and passive switches, add/drop filters, modulators, isolators, and integrated optical switch array circuits.