Resonant-Cavity Light-Emitting Diodes (RCLEDs) Made From a Simple Dielectric Coating of Transistor Outline (TO)-Can Packaged InGaN LEDs for Visible Light Communications

Abstract

An experimental evaluation of a directed line-of-sight visible light communication system based on phosphor-converted white resonant-cavity light-emitting diodes (RCLEDs) is presented. With a simple dielectric coating of the transistor outline-can-packaged InGaN LEDs, a $\lambda $ /4-thick Ta2O5/SiO2 distributed Bragg reflector functioning as the top mirror of near-UV RCLEDs can be formed automatically without inducing a registration misalignment as in conventional photolithography. In addition, a passivation coating can also be created over the entire LED structure. As a result of the optical cavity effect, the completed RCLEDs exhibit improved output performance in terms of light output power, external quantum efficiency, and directionality. The resulting RCLEDs are more suitable for building a 200 Mb/s ON–OFF keying nonreturn-to-zero optical link for data transmission over a distance of 100 cm in free space. Finally, we show that real-time transmissions of digital TV signals can be accomplished using the proposed short-range ( $\sim 100$ cm) optical wireless link (data rate $\sim 150$ Mb/s) mainly consisting of a field-programmable gate array-based video encoder/decoder, an optical bandpass filter, and the phosphorescent white RCLEDs made by a simple process.