We demonstrate high-speed LiFi data communication of over 20 Gbit/s using visible light from a laser-based white light emitting surface mount device (SMD) product platform that offers 10-100X the brightness of conventional LED sources. Equipped with high power blue laser diodes that offer over 3.5 GHz of 3 dB bandwidth, the laser-based white light SMD modules exhibited a signal-to-noise ratio (SNR) above 15 dB up to 1 GHz. The high SNR was combined with high order quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM) to maximize the bandwidth efficiency. In this work, we present a laser based white light SMD module configured with a single 3W blue laser diode mounted on heat-sink, optically coupled to a collimating optic, achieving a LiFi data rate of up to 10 Gbit/s. Moreover, we demonstrate wavelength division multiplexing (WDM), from a white light SMD module configured with two blue laser diodes separated in peak wavelength to serve as separate communication channels. Using WDM, the dual laser SMD module enabled LiFi data rates of over 20 Gbit/s by simultaneously transmitting data over both channels.
We report the high-speed performance of semipolar GaN ridge laser diodes at 410 nm and the dynamic characteristics including differential gain, damping, and the intrinsic maximum bandwidth. To the best of our knowledge, the achieved modulation bandwidth of 6.8 GHz is the highest reported value in the blue-violet spectrum. The calculated differential gain of ~3 x 10-16 cm2, which is a critical factor in high-speed modulation, proved theoretical predictions of higher gain in semipolar GaN laser diodes than the conventional c-plane counterparts. In addition, we demonstrate the first novel white lighting communication system by using our near-ultraviolet (NUV) LDs and pumping red-, green-, and blueemitting phosphors. This system satisfies both purposes of high-speed communication and high-quality white light illumination. A high data rate of 1.5 Gbit/s using on-off keying (OOK) modulation together with a high color rendering index (CRI) of 80 has been measured.
III-nitride light emitters, such as light-emitting diodes (LEDs) and laser diodes (LDs), have been demonstrated and studied for solid-state lighting (SSL) and visible-light communication (VLC) applications. However, for III-nitride LEDbased SSL-VLC system, its efficiency is limited by the “efficiency droop” effect and the high-speed performance is limited by a relatively small -3 dB modulation bandwidth (<100 MHz). InGaN-based LDs were recently studied as a droop-free, high-speed emitter; yet it is associated with speckle-noise and safety concerns. In this paper, we presented the semipolar InGaN-based violet-blue emitting superluminescent diodes (SLDs) as a high-brightness and high-speed light source, combining the advantages of LEDs and LDs. Utilizing the integrated passive absorber configuration, an InGaN/GaN quantum well (QW) based SLD was fabricated on semipolar GaN substrate. Using SLD to excite a YAG:Ce phosphor, white light can be generated, exhibiting a color rendering index of 68.9 and a color temperature of 4340 K. Besides, the opto-electrical properties of the SLD, the emission pattern of the phosphor-converted white light, and the high-speed (Gb/s) visible light communication link using SLD as the transmitter have been presented and discussed in this paper.
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