Textured LED gives green light to Li-Fi

August 10, 2017, Agency for Science, Technology and Research (A*STAR), Singapore
Textured LED gives green light to Li-Fi
V-pits on the surface of an InGaN LED (left) scatter light into the device’s active layers, known as quantum wells (QWs – right). Credit: American Chemical Society.

Standard light-emitting diodes (LEDs) used for home lighting can now transmit data more rapidly between electronic devices, thanks to new research from A*STAR.

Wireless visible light communication—also known as Li-Fi—relies on data signals encoded in incredibly brief pulses of light, far too quick for the eye to see. By supplementing congested Wi-Fi networks, Li-Fi could increase the capacity and speed of in offices, homes and public spaces. However, white LEDs typically use a phosphor coating to create a natural-looking white light, and the time it takes for the phosphor's glow to fade away limits how quickly the LED can transmit data.

Previous solutions typically required installing new types of white LEDs. Instead, Ee Jin Teo of the A*STAR Institute of Materials Research and Engineering, and colleagues, have developed a Li-Fi receiver that overcomes these problems. Rather than using a conventional silicon photodiode to detect transmissions, they found that an indium gallium nitride (InGaN) LED is an effective data receiver.

Crucially, the team's InGaN LEDs can detect only the 'fast' blue component of the phosphor's white light, which fades in only one nanosecond, and not the 'slow' yellow component which takes more than 50 nanoseconds to fade away.

The researchers also gave their InGaN LED a textured surface, so that every square centimeter was covered with one billion V-shaped pits (see image), roughly 150 nanometers deep. These V-pits scatter incoming light, allowing the LED's active layers to absorb more than twice as much blue light as an LED with a smooth surface.

Tests with a white LED showed that the InGaN LED with V-pits was a much better receiver than a standard silicon photodetector. "Using a silicon photodetector, the white LED can reach a switching speed of five megahertz—this typically means a data rate of up to 100 megabits per second," says Teo. "With our InGaN LED as a detector, this switching speed can be increased by four times, enabling faster data transmission rates from white LEDs."

She notes, however, that since the receiver is only picking up part of the white LED's , it may reduce the range over which data can be transmitted.

"The next stage of our research," she adds, "is to implement this concept into a dongle where the same LED can be used for transmission as well as detection of data."

Explore further: Researchers break bandwidth record for data communication using laser-based visible light

More information: Chengyuan Yang et al. Textured V-Pit Green Light Emitting Diode as a Wavelength-Selective Photodetector for Fast Phosphor-Based White Light Modulation, ACS Photonics (2017). DOI: 10.1021/acsphotonics.6b00867

Related Stories

Laser diodes versus LEDs

November 11, 2013

Solid-state lighting based on light-emitting diodes (LEDs) is the most efficient source of high color quality white light. Nevertheless, they show significant performance limitations such as the "efficiency droop". Blue laser ...

Lowering the cost and environmental footprint of white LEDs

August 31, 2016

Replacing traditional light bulbs with light-emitting diodes (LEDs) could take a significant bite out of global energy consumption. But making white LEDs isn't completely benign or budget friendly. To help reduce the environmental ...

Recommended for you

Unusual sound waves discovered in quantum liquids

July 20, 2018

Ordinary sound waves—small oscillations of density—can propagate through all fluids, causing the molecules in the fluid to compress at regular intervals. Now physicists have theoretically shown that in one-dimensional ...

A phonon laser operating at an exceptional point

July 20, 2018

The basic quanta of light (photon) and sound (phonon) are bosonic particles that largely obey similar rules and are in general very good analogs of one another. Physicists have explored this analogy in recent experimental ...

A physics treasure hidden in a wallpaper pattern

July 20, 2018

An international team of scientists has discovered a new, exotic form of insulating material with a metallic surface that could enable more efficient electronics or even quantum computing. The researchers developed a new ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

dirk_bruere
not rated yet Aug 11, 2017
The wheel is once more re-invented. IBM patented this basic idea some time in the 1980s

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.