“Ultrafast optical wireless data streaming for transmitting a high-definition video signal within one second with directly using the smart display made by RGB micro-LEDs” will come true soon. Under the continued support by the Ministry of Sci-ence and Technology (MOST) in Taiwan, Professor Gong-Ru Lin, Professor Hao-Chung Kuo, and Dr. Chih-Hsien Cheng collaborate to demonstrate the worldwide new record on “Beyond 5-Gbit/s data encoding and transmission in free space us-ing ultrafast 2×2 green micro light-emitting-diode (Green Micro-LED) array”. In previous years, the research on the high-speed green micro-LED always kept a slow pace due to its bottleneck originating from both material and device designs. The newly announced Green Micro-LED array with unique design and package achieves the world's fastest record for visible light wireless data communication of LED. This result follows the developing trend of high-speed blue and red Micro-LEDs to complete the last research mile that enables the free-space optical wireless communication from all kinds of intelligent display instruments made of RGB-Micro-LED array. The paper was rapidly accepted for publication by the Optica (formerly the Optical Society of America), subsequently recommended by Profes-sor Harald Haas with the University of Edinburgh in the United Kingdom, and se-lected from the nearly 10,000 papers each year published by the Optica Society as the focus report in “Spotlight on Optics” in osapublishing.org, Optica. The “Spot-light on Optics” web page has been published for more than a decade, and only at most 1% of the nearly 10,000 published papers in the whole year can be selected as the focus papers. This paper is one of only 2 of all chosen articles with Taiwan-ese academic institutions as the corresponding address in 2021. 

Professor Harald Haas, a world-renowned inventor of the Lighting Fidelity (LiFi) and the pioneer scientist in the field of Visible Light Communication (VLC), has pointed out that the communication data rates of video data streaming re-quire up to 1 Terabit or at least 4 Gigabit per second after distortion-free compres-sion, especially for enabling the head-mounted augmented reality devices playing fluent images that meet the perceived visual quality of humans. To satisfy this de-mand, it is crucial to develop the ideal candidate for a displaying or projecting light source in the visible spectral region that allows encoding with such data rates to realize distortion-free augmented reality vision. Also, for efficient usage of the spectral frequency band available in the visible light region, the development of ideal green Micro-LEDs with narrow linewidth, stabilized wavelength, weak droop effect, and high quantum efficiency remains a fundamental challenge in the aca-demic community. As recommended in his summary report to this research, he praised that the visible Micro-LED with high bandwidth and spectral stability de-veloped by Prof. Lin, Prof. Guo, and their teams will open a new era of intelligent display and metaverse related applications. 

This worldwide top-ranked modulation and communication record of the green Micro-LED array originates from a novel design on its material recipe, layered structure, and unique package proposed by Prof. Kuo and Prof. Lin. The new structural design breaks through the limitation set by the quantum-confined Stark effect to effectively solve the bottleneck that reduces emission efficiency under high current density injection yet to be overcome. Prof. Haaz declares that the de-vice's elegant and unique design essentially solves the problem left for future wave-division multiplexing applications: the spectral broadening and offset under high injection currents that persistently affected modulation speed and efficiency in past component designs. Another significant improvement came from Prof. Lin's proposal for packaging and integrating this array to a specially designed mi-crowave adapter, which effectively improves the electro-optical modulation bandwidth to 800-MHz for performing the high-speed data encoding assembly without significant distortion. It is envisaged that this component can achieve data transmission rates close to 10-Gbps through enhanced compensated digital driv-ing and modulation circuit technology. The release of this device will be immedi-ately valued by industrial companies in metaverse-related concepts such as Fox-conn Technology and so on. Such superior performance will rapidly explode its demand for industries of intelligent display, augmented reality, and lighting com-munications shortly. 

Citation Note in the Spotlight on Optics
As noted by Professor Harald Haas, the worldwide recognized inventor of Lighting Fidelity (LiFi) and the pioneer of Visible Light Communication (VLC), in his summary for the citation of “Ultrafast 2 × 2 green micro-LED array for optical wire-less communication beyond 5 Gbit/s” to be cited in the “Spotlight on Optics” (osapublishing.org) of Optica in November 2021. 

---“Multi-gigabit-per-second (Gbps) data rates delivered by high bandwidth, spectrally stable micro LEDs in the visible light spectrum will unlock new applica-tions. For instance, the raw data rate required for augmented reality headsets to produce human perception quality vision is 1 terabit per second. If compressed, this data rate would still be 4 Gbps. It is, therefore, essential to develop technolo-gies that allow these kinds of data rates. The visible light spectrum is an ideal can-didate for this purpose. However, for full exploitation of the available visible light spectrum, the opto-electrical conversion efficiency at ultra-high electrical band-width remains a fundamental challenge. This paper presents a new 2x2 micro LED array that provides an effective solution to the quantum-confined Stark effect, which typically reduces the emission efficiency under high injected current densi-ties. It also leads to a spectral shift that reduces the possible gains of wavelength division multiplexing due to the wide emission spectrum. This issue is elegantly re-duced. Moreover, due to the segmented design of the device the electrical 3-dB bandwidth is 800 MHz which constitutes a major improvement. It is envisaged that with enhanced digital modulation techniques, this device could be able to achieve data rates close to 10 Gbps.”

Reference on International Publication:
1.G.-R. Lin, H.-C. Kuo, C.-H. Cheng, Y.-C. Wu, Y.-M. Huang, F.-J. Liou, and Y.-C. Lee, “Ultrafast 2 × 2 green micro-LED array for optical wireless communication be-yond 5 Gbit/s”, Photonics Research 9(10), 2077-2087 (2021). View: Abstract | HTML | PDF
https://doi.org/10.1364/PRJ.437689

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