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Could this be the tech leap that makes your next smartphone faster – and cheaper?

South China Morning Post 04/11/2022 Holly Chik

Chinese scientists have found a way to turn a piece of wire into a source of laser-like light
Discovery could mean a new range of smaller, cheaper electronic devices, experts say

Chinese scientists have developed a new way to make laser-like light that could boost the communication speed of everyday electronic devices like smartphones and improve security screening in places like airports.

The team from the Shanghai Institute of Optics and Fine Mechanics under the Chinese Academy of Sciences has found a way to build a compact version of the device, known as a free-electron laser.

Such lasers usually require bulky, high-powered devices housed in large, expensive facilities.

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By using a piece of extremely fine wire about 8cm (3.1 inches) in length, the new device can emit laser-like light in a broad range of wavelengths for a wide array of applications, unlike typical laser light that is restricted to a very narrow range.

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The research team published their findings in the peer-reviewed journal Nature on Wednesday.

Lasers produce a narrow, directional beam of light in which all of the light waves have very similar wavelengths. Shorter wavelengths have more energy.

Lasers are created when electrons in the atoms of optical materials like glass, crystal or gas absorb energy in the form of light or electricity, according to the Lawrence Livermore National Laboratory in the United States.

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The extra energy excites the electrons to move to a higher-energy orbit around a the nucleus of an atom. When they return to their normal orbit, they emit light particles, called photons, which can be seen with the human eye.

The light waves in a laser beam are "coherent", meaning the beam of photons is moving in the same direction at the same wavelength.

Study co-author Ye Tian told the Shanghai Observer news outlet that the team found a way to sync electrons "like a team of honour guards", to generate greater power.

"Imagine the electrons as athletes rowing a boat. The team that can make bigger waves and generate higher power will win the race. The best strategy is for all athletes to paddle in the same direction."

In the study, the Chinese scientists excited free electrons - energetic electrons not bound to matter - by irradiating an iron wire using a high-power ultra-fast laser pulse.

The short pulse accelerated the electrons to a high velocity down the wire, which made other electrons in the wire emit electromagnetic waves, with which the free-electron pulse interacted. The electrons then transferred energy to the waves and amplified them.

Chinese scientists have developed a new way to make laser-like light that could have implications for the way we use common electronic devices. Photo: Handout

Judith Dawes, a physics professor at Macquarie University in Australia, who was not involved in the study, said the research "offers a complete rethink on how an electron beam can be generated".

"The electrons and light are coupled together through a wavelike propagation of the electrons moving in the wire," said Dawes, who researches light interactions at the nanoscale.

She said the new technology enabled very compact light sources to operate across a wide spectrum of wavelengths, from radio waves to X-rays.

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Radio waves have the longest wavelengths in the electromagnetic spectrum, ranging from the length of a very tall building down to about the size of an atom, while X-rays have very small wavelengths, between 0.03 and 3 nanometres, according to Nasa.

Dawes said the new technology would find ready applications for improved security screening and sensing. Body-scanning machines at airports, for example, use millimetre-wave technology.

"The prospect of replicating Zhang and colleagues' findings with visible radiation is particularly exciting, because it could lead to highly compact sources of amplified light," physicist Nicholas Rivera with Harvard University wrote in an accompanying commentary published by Nature.

"This could be especially useful in materials, such as silicon, that are widespread and readily fabricated, but that have so far proved challenging to use as media for lasers," he said.

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David Gozzard, with the International Centre for Radio Astronomy Research in Australia, who was not involved in the study, echoed its potential application in silicon.

He pointed to smartphones, which contain computers, memory, motion sensors and cameras - all based on silicon.

"The more types of devices we can engineer from silicon, the smaller and cheaper we can make a huge variety of sensors and tools," he said.

"With further refinement, and finding ways to produce higher frequency [visible] light, tiny silicon-based lasers made from this technology will find their way into phones and other devices for high-speed communications and precision sensors."