Light-based wireless communications on the way after university demos world's first white lasers

Arizona State University claims white lasers could herald the introduction of 'Li-Fi', as well as even more energy-efficient lighting

Researchers at Arizona State University claim to have demonstrated the world's first white lasers in a development that could bring "light-based wireless communication".

White lasers, invented in 1960, are more luminous and energy efficient than LEDs, and offer the prospect not just of more energy-efficient lighting, but new forms of light-based communications.

However, "realising such a device has been challenging because of intrinsic difficulties in achieving epitaxial growth of the mismatched materials required for different colour emission," according to the paper published in Nature this week. The paper had been submitted in October, but required extensive peer review before publication.

The researchers, Cun-Zheng Ning, professor in the School of Electrical, Computer and Energy Engineering, together with doctoral students Fan Fan, Sunay Turkdogan, Zhicheng Liu and David Shelhammer, claim to have created "a novel nanosheet - a thin layer of semiconductor that measures roughly one-fifth of the thickness of human hair, with a thickness that is roughly one-thousandth of the thickness of human hair - with three parallel segments, each supporting laser action in one of three elementary colours.

"The device is capable of lasing in any visible colour, completely tunable from red, green to blue, or any colour in between. When the total field is collected, a white colour emerges," claims the university.

It continues: "The technological advance puts lasers one step closer to being a mainstream light source and potential replacement or alternative to light emitting diodes (LEDs).

"Lasers are brighter, more energy efficient, and can potentially provide more accurate and vivid colours for displays like computer screens and televisions. Ning's group has already shown that their structures could cover as much as 70 per cent more colours than the current display industry standard.

"Another important application could be in the future of visible light communication in which the same room lighting systems could be used for both illumination and communication.

"The technology under development is called Li-Fi for light-based wireless communication, as opposed to the more prevailing Wi-Fi using radio waves. Li-Fi could be more than 10 times faster than current Wi-Fi, and white laser Li-Fi could be 10 to 100 times faster than LED-based Li-Fi, currently still under development.

"The concept of white lasers first seems counter-intuitive because the light from a typical laser contains exactly one colour, a specific wavelength of the electro-magnetic spectrum, rather than a broad-range of different wavelengths. White light is typically viewed as a complete mixture of all of the wavelengths of the visible spectrum," said Ning, who also researched the technology at Tsinghua University in China.

However, while the proof-of-concept shows that it is possible to build white-light lasers, the next step is demonstrating how they can be built more easily and powered by everyday power sources, such as batteries.

"This experimental effort demonstrates the key first material requirement and will lay the groundwork for the eventual white lasers under electrical operation," claims the university.

The technology has been widely researched around the world, with BT one of the organisations that have been competing to develop white-laser communications.