A Team of Tohoku University Researchers produced Deep Ultraviolet LEDs for data transmission

A team of Tohoku University researchers has developed Deep Ultraviolet (DUV) LEDs. The team published their research results on 22nd July in Applied Physics Letters. Tohoku University was established as Japan's third national university in 1907. Located on the ancient site of Aoba Castle in Sendai City, Tohoku University is proud to be ranked among Japan's leading universities.

What is a Deep Ultraviolet LED?

A Deep-UV LED is an LED that emits light in the wavelength range called "UV-C" (100 to 280 nm). Currently, the development of Deep-UV LEDs is becoming particularly active. This is because the demand for Deep-UV LEDs has increased dramatically as an alternative device to replace mercury lamps, which have been the main light sources used for UV light application equipment such as sterilization equipment.

Deep-UV LEDs have unique benefits compared to mercury lamps such as small size, high efficiency and zero warm-up time.

Tohoku University

Researchers have solved a major problem for optical wireless communications. Kazunobu Kojima, associate professor at the Insitute of Multidisciplinary Research for Advanced Materials at Tohoku University, stated: "A key technology for faster modulation is to decrease the device size.” He further stated: “However, this tactic creates a dilemma: although smaller LEDs can be modulated faster, they have lower power”.

Another issue is that both visible and infrared optical wireless communications can have significant solar interference, according to Kojima. To avoid confusion with visible and infrared solar light, the researchers aimed to improve LEDs that specifically communicate via deep ultraviolet light, which can be detected without solar interference.

"Deep ultraviolet LEDs are currently mass-produced in factories for applications related to COVID-19," Kojima said, noting that deep ultraviolet light is used for sterilization processes as well as in solar-blind optical wireless communications. "So, they're cheap and practical to use."

The researchers produced the deep ultraviolet LEDs on sapphire templates, which are inexpensive, and measured their transmission speed. They found out that the deep ultraviolet LEDs were smaller and much quicker in their communications than traditional LEDs at that speed.

"The mechanism underlying this speed is in how a lot of tiny LEDs self-organize in a single deep ultraviolet LED," Kojima said. "The tiny LED ensemble helps with both power and speed."

The researchers want to use the deep ultraviolet LEDs in 5G wireless networks. Many technologies are currently under testing to contribute 5G, and Li-Fi, or light fidelity, is one of the candidate technologies.

"Li-Fi's critical weakness is its solar dependency," Kojima said. "Our deep ultraviolet LED-based optical wireless technology can compensate for this problem and contribute to society, I hope."

What is Li-Fi?

Li-Fi, also known as "Light Fidelity" is a wireless optical networking technology, which uses light-emitting diodes (LEDs) to transmit data. In 2011, professor Harald Haas made a Li-Fi demonstration at the TED (Technology, Entertainment, Design) Global Talk on Visible Light Communication (VLC). Below is a video demonstration of Li-Fi technology by professor Harald Haas:

VLC uses light as a medium to deliver high-speed communication like Wi-Fi and complies with the IEEE standard IEEE 802.15.7. The IEEE 802.15.7 is a high-speed, bidirectional, and fully networked wireless communication technology-based standard similar to Wi-Fi's IEEE 802.11.

How does Li-Fi work?

Li-Fi is a high speed, bidirectional, and fully networked wireless communication of data using light. Li-Fi constitutes of several light bulbs that form a wireless network.

When an electrical current goes through to a LED light bulb, a stream of light (photons) emits from the lamp. LED bulbs are semiconductor devices, which means that the brightness of the light flowing through them can change at extremely high speeds. The signal is sent by modulating the light at different rates. The signal can then be received by a detector which interprets the changes in light intensity (the signal) as data. Also when the LED is ON, you transmit a digital 1, and when it is OFF, you transmit a 0.

Top Applications of Li-Fi Technology

Li-Fi technology in Hospitals

As Li-Fi does not interfere with radio frequency devices, Li-Fi can be safely used in many hospital applications. For example, in corridors, waiting rooms, patient rooms, and operating theatres, Li-Fi technology will allow a light communication network, which will remove electromagnetic interference issues from smartphones and the use of Wi-Fi in hospitals. Li-Fi can also be used for real-time monitoring and report of patient movement and vital signs without the need for wires.

Li-Fi can enable patients on their beds connecting to internet news, emails, video games, and social media platforms through their smartphones. This will help them pass the time during their stay. For medical workers, Li-Fi will enable the tracking and relocation of the positions of key medical devices especially those regularly shared by different departments.  Check the below diagram for a summary of the benefits of Li-Fi in hospitals.

Li-Fi in Schools

The right wireless network is a key component to provide new learning experiences by connecting students and teachers to smart technology, enabling learning applications on any mobile device. Li-Fi can also provide seamless network connectivity and security throughout the whole school, from the classroom all the way through to university dorms.  Some schools have even started trialing Li-Fi technology in classrooms.

The Kyle Academy, based in Scotland has also started using Li-Fi in the classroom.  The Li-Fi project is being run in collaboration with PureLiFi and The University of Edinburgh. The installation of pureLiFi’s LiFi-XC system consists of eight LiFi-enabled LED light bulbs in the ceiling and students have been given access to LiFi-XC Stations that plug into their laptops enabling high-speed connectivity through the lights.

Li-Fi in Retail

Li-Fi can help to direct shoppers from the time they enter the shop. It can also help them to locate specific products in the store, collect digital coupons, check store promotions, check stock availability of some products on the shelves, engage in-store online services through their smart devices and improve their store experience.

For retailers, Li-Fi can enable them to send promotions to shoppers’ smart devices, displaying promotions, and offers. Li-Fi can also help retailers understanding behavior anonymously for most customers, understanding the demographics of their shoppers, enabling target marketing campaigns, conducting display advertising campaigns, and checking real-time stock availability. Li-Fi will bring an opportunity for shopping malls and centres to be a frontrunner in gaining an understanding of their customers and ultimately influencing them.

You can read more about Li-Fi applications from the following links:

https://www.lifitn.com/blog/2018/8/30/5-applications-of-li-fi-technology

https://www.lifitn.com/blog/2019/6/6/top-li-fi-applications-updated-list

Conclusion

In conclusion, Research institutes and schools are increasingly implementing Li-Fi systems in order to offer secure and seamless Internet connectivity to their students. In addition, drastically rising data consumption and increasing RF spectrum crunch are further laying down the groundwork that will foster the adoption of alternative wireless communication technologies like Li-Fi, further pushing its overall industry outlook. If you have enjoyed this post and would like to hear more updates about Li-Fi technology subscribe to our newsletter. Don’t forget to subscribe to our social media accounts.

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