Towards 10 Gb/s orthogonal frequency division multiplexing-based visible light communication using a GaN violet micro-LED

Visible light communication(VLC)is a promising solution to the increasing demands for wireless connectivity.Gallium nitride micro-sized light emitting diodes(micro-LEDs)are strong candidates for VLC due to their high bandwidths.Segmented violet micro-LEDs are reported in this work with electrical-to-optical bandwidths up to 655 MHz.An orthogonal frequency division multiplexing-based VLC system with adaptive bit and energy loading is demonstrated,and a data transmission rate of 11.95 Gb/s is achieved with a violet micro-LED,when the nonlinear distortion of the micro-LED is the dominant noise source of the VLC system.A record 7.91 Gb/s data transmission rate is reported below the forward error correction threshold using a single pixel of the segmented array when all the noise sources of the VLC system are present.

1 Gbps free-space deep-ultraviolet communications based on Ⅲ-nitride micro-LEDs emitting at 262 nm

The low modulation bandwidth of deep-ultraviolet(UV) light sources is considered as the main reason limiting the data transmission rate of deep-UV communications. Here, we present high-bandwidth Ⅲ-nitride microlight-emitting diodes(μLEDs) emitting in the UV-C region and their applications in deep-UV communication systems. The fabricated UV-C μLEDs with 566 μm2 emission area produce an optical power of 196 μW at the 3400 A∕cm2 current density. The measured 3 dB modulation bandwidth of these μLEDs initially increases linearly with the driving current density and then saturates as 438 MHz at a current density of 71 A∕cm2, which is limited by the cutoff frequency of the commercial avalanche photodiode used for the measurement. A deep-UV communication system is further demonstrated. By using the UV-C μLED, up to 800 Mbps and 1.1 Gbps data transmission rates at bit error ratio of 3.8 × 10-3 are achieved assuming on-off keying and orthogonal frequency-division multiplexing modulation schemes, respectively.

10 Gbps wavelength division multiplexing using UV-A, UV-B, and UV-C micro-LEDs

Deep ultraviolet(DUV) optical wireless communications have seen increased interest in recent years due to the unique properties of light in this spectral region. However, the reported DUV data rates remain significantly lower than comparable demonstrations at visible wavelengths due to lower modulation bandwidths and/or output power of the sources. Here, we present a wavelength division multiplexing demonstration using three UV microlight-emitting diodes emitting at nominal peak wavelengths of 285, 317, and 375 nm, respectively, each with an emitting area of approximately 1369 μm^(2)(equivalent to circular device pixels of diameter;0 μm). Using orthogonal frequency division multiplexing, data rates of 4.17, 3.02, and 3.13 Gbps were achieved from the 285, 317, and 375 nm devices, respectively, for a combined data rate of 10.32 Gbps transmitted over a distance of 0.5 m.

Ultrahigh frame rate digital light projector using chip-scale LED-on-CMOS technology

Digital light projector systems are crucial components in applications,including computational imaging,fluorescence microscopy,and highly parallel data communications.Current technology based on digital micromirror displays are limited to absolute frame rates in the few tens of kiloframes per second and require the use of external light sources and coupling optics.Furthermore,to realize gray-scale pixel values using duty cycle control,frame rates are reduced proportionally to the number of gray levels required.Here we present a self-emissive chip-scale projector system based on micro-LED pixels directly bonded to a smart pixel CMOS drive chip.The 128×128 pixel array can project binary patterns at up to 0.5 Mfps and toggle between two stored frames at megahertz rates.The projector has a 5-bit gray-scale resolution that can be updated at up to 83 kfps,and can be held in memory as a constant bias for the binary pattern projection.Additionally,the projector can be operated in a pulsed mode,with individual pixels emitting pulses down to a few nanoseconds in duration.Again,this mode can be used in conjunction with the high-speed spatial pattern projection.As a demonstration of the data throughput achievable with this system,we present an optical camera communications application,exhibiting data rates of>5 Gb/s.