This work reports the use of the chip-based GaN-based micro-LED (μLED) arrays for multifunctional applications as microdisplay, data transmitters, photodetectors, and solar cells. The functions of display and transmitter have been reported, and particularly, we experimentally demonstrated that μLED arrays could be used as self-powered, high-performance, and wavelength-selective photodetectors (PDs), enabling high-speed multiple-input multiple-output (MIMO) visible light communications (VLC) under on−off keying (OOK) modulation scheme using 405 nm violet laser diodes (LDs) as transmitters. The optoelectronic and communication characteristics of the μLED-based PDs with diameters of 40, 60 and 100 μm were systematically studied. The optoelectronic analysis shows superior performances of μLEDbased PDs at a 405 nm wavelength compared with other previously reported GaN-based PDs. Under a bias voltage of −5 V, the comparable peak responsivities of 0.27, 0.31, and 0.24 A/W, specific detectivities of 1.1 × 10 11 , 2.3 × 10 12 , and 2.1 × 10 12 cm H 1/2 W −1 , and linear dynamic ranges (LDRs) of 152, 162, and 164 dB were achieved for 40, 60, and 100 μm μLEDs, respectively. Even at zero-bias, that is, self-powered mode, we have achieved high peak responsivities of 0.24, 0.29, and 0.21 A/ W, high specific detectivities of 7.5 × 10 12 , 1.5 × 10 13 , and 1.3 × 10 13 cm H 1/2 W −1 , and high LDR up to 186, 196, and 197 dB for 40, 60, and 100 μm μLEDs, respectively. The μLEDs could also be used to harvest the optical energy of the system, working as solar cells. The μLED-based PD arrays were tested as receivers in the VLC system to implement high-speed parallel communication, which yields maximum data rates of 180, 175, and 185 Mbps for single 40, 60, and 100 μm μLED-based PDs at a distance of 1 m with BERs of 3.5 × 10 −3 , 3.7 × 10 −3 , and 3.5 × 10 −3 , respectively. Furthermore, the 2 × 2 MIMO parallel VLC system was achieved to increase the VLC data rate, which suggests the potential of using large μLED-based PD arrays for multiple Gbps and even Tbps VLC applications.

In this study, we built a single photon avalanche diode (SPAD) receiver based underwater wireless optical communication (UWOC) system. The bit error rate (BER) and signal-to-noise ratio (SNR) performance of UWOC with different distances and data transmission rates were obtained. Based on the water attenuation coefficient of 0.12 m −1 , a series of neutral density (ND) filters were exploited to attenuate the light output power from the blue laser diode (LD) to simulate the long distance UWOC. The maximum estimated distances of 144 m and 117 m with corresponding BERs of 1.89 × 10 −3 and 5.31 × 10 −4 at data transmission rates of 500 bps and 2 Mbps were acquired in UWOC system using on-off keying (OOK) modulation scheme, respectively. Furthermore, we compared the differences between free-space and underwater channels, and a divergence angle of ∼1.02 mrad was measured experimentally at a distance of 50 m in the free space. The long UWOC distances obtained in this study partly benefit from high sensitivity SPAD, the small laser divergence angle and low light attenuation. This study provides an approach to achieve long distance UWOC using SPAD.

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This work proposes an underwater wireless optical communication (UWOC) system based on computational temporal ghost imaging (CTGI) and a low-bandwidth high-sensitivity avalanche photodiode. After measuring the attenuation coefficient of water, a series of neutral density filters is used to attenuate the optical power to estimate the distance of UWOC. Experimental results show that under the conditions of 4 GHz transmitting frequency and 144.37 m estimated distance, through CTGI, we can achieve error-free transmission, and the peak signal-to-noise ratio is much higher than on–off keying. Additionally, after adopting the segmented reconstruction method, under the condition of 4 GHz transmitting frequency and 193.10 m estimated distance, we can also achieve error-free transmission. At the same time, the relationship between UWOC performance and the number of segments is also studied. This research provides a novel UWOC technique that enables high-frequency transmission signals to be detected by a low-bandwidth photodetector for long-distance UWOC.