Because laser is an acronym for “light amplification by stimulated emission of radiation,” these new contraptions – which exploit particles of sound called phonons – should properly be called phasers. Such devices could one day be used in ultrasound medical imaging, computer parts, high-precision measurements, and many other places.
A laser is created when a bunch of light particles, known as photons, are emitted at a specific and very narrow wavelength. The photons all travel in the same direction at the same time, allowing them to efficiently carry energy from one place to another. Since their invention more than 50 years ago, almost all lasers have used light waves. Early on, scientists speculated that sound waves be used instead, but this has proved tricky to actually achieve.
It wasn’t until 2010 that researchers built the very first sound lasers, coaxing a collection of phonons to travel together. But those first devices were hybrid models that used the light from a traditional laser to create a coherent sound emission.
“In our work, we got rid of this optical part,” said engineer Imran Mahboob of NTT Basic Research Laboratories in Japan, co-author of a paper describing the new sound lasers that appears Mar. 18 inPhysical Review Letters. Because they need one less part, these new phasers “are much easier to integrate into other applications and devices.”
These phasers can be integrated into tiny “integrated circuit”, but they are not currently capable of directing the very narrow wavelength in a “beam” like light lasers can, as light can travel in a vacuum, whereas “phonons” need a “medium to travel through”.
“We would lose the lasing if we get it out,” said Mahboob. “So we will need to figure out how to build structures onto the resonator that would allow us to transmit the vibrations out as energy.” Currently, he doesn’t have a good idea of how to do that, though other researchers will likely expand on the work and offer suggestions.
While this means you can’t make the cat chase after a tiny dot of sound, there are still a lot of potential uses for these phasers. A tiny part of the device translates the mechanical vibration into an oscillating electrical signal, which could serve as a tiny clock. Most modern day electronics use a quartz crystal to keep time but these crystals tend to be relatively bulky objects that consume a lot of energy. A miniscule sound laser could provide the same effect and replace quartz crystals, said Mahboob.
Other potential applications, once the technology matures further, would be to use the ultrasound frequencies to scan objects or people for safety or medical purposes. Alternatively, the extremely narrow sound wavelengths could be used for high-precision measurement, suggested electrical engineer Jacob Khurgin of Johns Hopkins University in Baltimore, Maryland.