Jul 31 2020
A crucial challenge faced in the field of optical wireless communications—the process where light carries data between cell phones and other devices—has now been resolved by a team of researchers.
Researchers aimed to improve LEDs that specifically communicate via deep ultraviolet light, which is not visible to the human eye. Image Credit: Kazunobu Kojima, Tohoku University.
Light-emitting diodes (LEDs) pulse their light in a coded message that can be decoded by the recipient devices.
Currently, Japanese researchers have coupled the two choices into a perfect combination of fast and durable LEDs. The researchers published their findings in the Applied Physics Letters journal on July 22.
A key technology for faster modulation is to decrease the device size. However, this tactic creates a dilemma: although smaller LEDs can be modulated faster, they have lower power.
Kazunobu Kojima, Study Author and Associate Professor, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
According to Kojima, another problem is the fact that both infrared and visible optical wireless communications could have considerable solar interference. With the aim of avoiding confusion with infrared and visible solar light, the team intended to enhance LEDs that particularly communicate through deep ultraviolet light, which could be detected without any hindrance due to solar interference.
“Deep ultraviolet LEDs are currently mass-produced in factories for applications related to COVID-19,” Kojima stated, observing that deep ultraviolet light is utilized in solar-blind optical wireless communications and for sterilization processes. “So, they’re cheap and practical to use.”
The scientists developed the deep ultraviolet LEDs on sapphire templates, which are regarded as a low-cost substrate, and quantified their transmission speed. It was identified that the deep ultraviolet LEDs were smaller and much faster in their communications compared to conventional 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. The tiny LED ensemble helps with both power and speed.
Kazunobu Kojima, Study Author and Associate Professor, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
The team intends to utilize the deep ultraviolet LEDs in 5G wireless networks. At present, several technologies are under testing to contribute 5G, and Li-Fi (which stands for light fidelity) is one of the viable technologies.
Li-Fi’s critical weakness is its solar dependency. Our deep ultraviolet LED-based optical wireless technology can compensate for this problem and contribute to society, I hope.
Kazunobu Kojima, Study Author and Associate Professor, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
This work was financially supported in part by the Five-Star Alliance and the Japan Society for the Promotion of Science.
Journal Reference:
Kojima, K., et al. (2020) Self-organized micro-light-emitting diode structure for high-speed solar-blind optical wireless communications. Applied Physics Letters. doi.org/10.1063/5.0013112.