Group-III-nitride superluminescent diodes for solid-state lighting and high-speed visible light communications

Abstract

Group-III-nitride superluminescent diodes (SLDs) are emerging as light sources for white lighting and visible light communications (VLC) owing to their droop-free, low speckle noise and large modulation bandwidth properties. In this study, we discuss the development of GaN-based visible SLDs, and analyze their electro-optical properties by studying the optical power-bandwidth products (PBPs) and injection current densities. The significant progress in blue SLDs and their applications for white light VLC is highlighted. A blue SLD, with an optical power of > 100 mW and large PBP of 536 mW.nm, is utilized to generate white light, resulting in a high CRI of 88.2. In a modulation experiment designed for an SLD-based VLC system, an on-off keying scheme exhibits a 1.2 Gbps data rate, with a bit error rate (BER) of 1.8 × 10-3, which satisfies the forward error correction (FEC) criteria. A high data rate of 3.4 Gbps is achieved using the same SLD transmitter, by applying the 16-QAM discrete multi-tone (DMT) modulation scheme for high-speed white light communication. The results reported here unequivocally point to the significant performance and versatility that GaN-based SLDs could offer for beyond-5G implementation, where white lighting and high spectral efficiency VLC systems can be simultaneously implemented.