GaN-Based Miniaturized Cyan Light-Emitting Diodes on a Patterned Sapphire Substrate With Improved Fiber Coupling for Very High-Speed Plastic Optical Fiber Communication
We demonstrate the performance of a novel cyan light-emitting diode (LED) on a patterned sapphire (PS) substrate as a light source for plastic optical fiber (POF) communications with the central wavelength at 500 nm. To further enhance the external quantum efficiency (EQE) and output power of this miniaturized high-speed LED, a LED with a PS substrate is adopted. Furthermore, by greatly reducing the number of active <formula formulatype="inline"> <tex Notation="TeX">$\hbox{In}_{\rm x}\hbox{Ga}_{1 - {\rm x}}\hbox{N/GaN}$</tex></formula> multiple quantum wells (MQWs) to four and minimizing the device active area, we can achieve a record-high electrical-to-optical (E–O) bandwidth (as high as 400 MHz) among all the reported high-speed visible LEDs under a very small dc bias current (40 mA). The fiber coupling efficiency has been improved in 4 dB using lens with a 500-<formula formulatype="inline"><tex Notation="TeX">$\mu \hbox{m}$</tex></formula> diameter mounted on the LED chip. Thus, the maximum fiber-coupled power was <formula formulatype="inline"><tex Notation="TeX">$-$</tex></formula>2.67 dBm at the bias current of 40 mA. The 1.07-Gb/s data transmissions over a 50-m SI-POF fiber have been successfully demonstrated using this device at the bias current of 40 mA.