Red and green resonant cavity LEDs for datacom applications

We report on the development of resonant cavity LEDs (RCLEDs) for use in short distance datacommunication applications using the IEEE 1394 standard where plastic optical fibre (POF) is the physical medium. The devices are designed for 650nm and 500nm emission where POF has low attenuation. The red devices based on InGaAlP/GaAs are optimised for room temperature operation and 90μm diameter devices have a maximum coupled power to 1mm diameter POF of 1mW. At 10mA the coupled power is 0.4mW with a quantum efficiency of 2%. Current spreading is shown to be critical in optimising the output power. The devices function as resonant cavity detectors with a response FWHM of 4.2nm centred at 650nm. The blue-green RCLEDs are based on InGaN/GaN and use a hybrid metal-epitaxial mirror cavity. This wavelength is preferable for longer links. The substrate emitting devices have fibre-coupled powers of 200μW at 20mA. A datarate of 250Mb/s is measured. The resonant cavity is confirmed by angularly resolved spectral measurements. The tradeoff between green and red devices is discussed.