Light Emitting Diodes: Toward Smart Lighting

We review the history and state-of-the-art of light emitting diode (LED). Unique properties of LEDs– high efficiency, long life time, flexibility in obtaining customized spectral power distribution, fast modulation rate, compact form factor, ability to generate radiation with wavelengths outside the visible range (infrared and ultraviolet, including deep ultraviolet) enable multiple applications for signage, display, general lighting, biology, medicine, agriculture, communications, industrial controls, security, and transportation. Many of emerging LED applications will be in "smart lighting", which are applications that are not possible or difficult to achieve using more traditional lighting sources.