Physicists at The Australian National University (ANU) have developed
extremely powerful microscopic lasers that are even smaller than the
wavelength of the light they produce.
So called 'nanolasers' have a huge variety of medical, surgical, industrial
and military uses, covering everything from hair removal to laser printers
and night-time surveillance.
According to lead researcher Professor Yuri Kivshar, the nanolasers
developed by his team promise to be even more powerful than existing lasers,
allowing them to be useful in smaller-scale devices.
"They can also be integrated on a chip," he said.
"For example, they can be mounted directly on the tip of an optical fiber to
lighten or operate on a particular spot inside a human body.
"This technology uses laser light instead of electronics, an approach called
photonics. It's exciting to see how this can be realized in everyday
practical devices, like mobile phones."
Professor Kivshar's team used a clever trick to modify conventional lasers,
which traditionally comprise some form of light amplification device placed
between two mirrors. As the light bounces back and forth between the two
mirrors it becomes brighter and brighter.
Instead of mirrors, the research team created a device that works like
"inside-out" noise-canceling headphones and which traps energy and prevents
it from escaping. The trapped light energy builds up into a strong,
well-shaped laser.
This trick overcomes a well-known challenge of nanolasers—energy leakage.
To fabricate the laser, the team collaborated with Professor Hong-Gyu Park
and his group at Korea University.
The researchers say the device's efficiency was high—only a small amount of
energy was required to start the laser shining—with a threshold about 50
times lower than any previously reported nanolaser and narrow beam.
Professor Kivshar said the new laser builds on a quantum mechanical
discovery made almost 100 years ago.
"This mathematical solution was published by Wigner and von Neumann in 1929,
in a paper that seemed very strange at the time—it was not explained for
many years," Professor Kivshar said.
"Now this 100-year-old discovery is driving tomorrow's technology."
The research is reported in Nature Communications.
Reference:
Min-Soo Hwang et al, Ultralow-threshold laser using super-bound states in
the continuum, Nature Communications (2021).
DOI: 10.1038/s41467-021-24502-0
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Physics