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Faster LEDs Enable Wireless Communications from Invisible Light

September 21, 2020 by Luke James

A Tohoku University team of researchers claims to have made significant improvements on a type of LED technology, which could see it used in 5G wireless networks.

Japanese researchers claim that they have solved a major challenge for optical wireless communications—wherein pulsating light carries information via coded messages—by developing a new type of LED, or light-emitting diode, that is both long-lasting and super-fast.

In research published in Applied Physics Letters in July 2020, the Tohoku University team describes their deep ultraviolet, aluminium gallium nitride LEDs.


A side view of an LED device that emits ultraviolet light. Image Credit: Getty Images.


What Are Deep Ultraviolet LEDs? 

Deep ultraviolet (DUV) light-emitting diodes are types of LEDs that emit light in the UVC radiation wavelength range (UVC is 100 to 280 nanometres). Currently, the development of DUV LEDs is becoming very active because the demand for them has grown dramatically as an alternative to mercury lamps, namely the light sources used for UV light applications (such as hospital sterilisation equipment).

When compared to mercury lamps, DUV LEDs have many additional benefits, such as higher efficiency, zero warm-up time, and a smaller size—altogether a boon for faster modulation. 


Faster Speed

A common trade-off for faster modulation, however, is that of power. “Although smaller LEDs can be modulated faster, they have lower power,” says Kazunobu Kojima, associate professor at the Institute of Multidisciplinary Research for Advanced Materials at Tohoku University.

Another problem is that boost visible and infrared optical wireless communications can be subject to interference from visible and infrared solar light. To avoid the confusion that would come from such solar interference, the research team tried to enhance existing LEDs that already specifically communicate via deep ultraviolet light. This was so that they could enable detection without solar interference.


Tohoku University’s diagram of its LED structure (viewed from the side and annotated).

Tohoku University’s diagram of its LED structure (viewed from the side and annotated). Image Credit: Tohoku University.


The researchers produced their DUV LEDs on inexpensive sapphire templates and measured their transmission speed. Initial findings were positive and demonstrated that DUV LEDs were a lot faster in their communications—even despite their small size—than traditional LEDs.

Said Jokima: “The mechanism underlying this speed is in how a lot of tiny LEDs self-organise in a single deep ultraviolet LED. The tiny LED ensemble helps with both power and speed”.


Future Interests and Potential Applications

The research team hopes to use its new DUV LED technology in 5G wireless networks. As a Li-Fi (or light-fidelity) technology, the Tohoku University research team’s DUV LEDs could stand a chance. Li-Fi, which uses LEDs to transmit data, is currently a promising candidate and many iterations of it are currently being tested for use in real-world 5G applications.

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