Large-Signal Modulation Performance of Light-Emitting Diodes With Photonic Crystals for Visible Light Communication

Recently, GaN-based light-emitting diodes (LEDs) find their applications in, other than general lighting, visible light communication (VLC) for high-speed wireless data networks. The pursuit for more bandwidth from the LED can be realized by engineering the LED material structure and device design, or by modulation techniques. In this paper, we proposed GaN-based LEDs with the photonic crystal (PhC) structure for VLC applications. Contradictory to general thought that higher small frequency response translates to better large-signal performance, our results reveal that a PhC LED may not perform well at low data rate due to its relatively poorer signal-to-noise ratio (SNR). However, at higher data rates, the performance of PhC LEDs surpasses conventional LED structure. We showed data transmission capability of PhC LEDs with a bit rate up to 400 Mb/s using on–off keying modulation. To demonstrate the chip capability for large-signal transmission, without using preemphasis or postemphasis, VLC with 16-quadrature amplitude modulation orthogonal frequency-division multiplexing transmission capacity up to 2 Gbit/s is achieved with an error vector magnitude of 17.07%, SNR of 15.35 dB, and bit error rate of
$3.3 \times {10}^{-3}$
. Our LEDs embedded with PhCs pass the forward error correction criterion. The results reveal the advantages of LEDs with PhC for achieving higher data rate transmission.