A high-efficiency white-light-emitting device that includes a polariton light emitter that emits UV or blue light to a down-converting material that converts the polariton emissions to white light. The polariton light emitter includes an active region situated within a resonant optical cavity formed on a substrate. The down-converting material can comprise a luminophoric phosphor or other material. The polariton light and down-converting material can be arranged in a single apparatus to provide a white-light-emitting device that can be used for lighting and instrumentation. The device can also be configured for high-frequency modulation to provide optical signals for communications and control systems.