Scientists develop 'saser' that emits sound rather than light

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London, Feb 27 (ANI): Two research groups, using tiny drum heads and vibrating towers, have made impressive advances in developing a 'saser', which is a new type of laser that emits sound rather than light.

According to a report in Nature News, such sound-based lasers are still in their infancy, but they could one day lead to everything from more detailed ultrasound imaging to faster electronics, according to the research teams.

The maths for sound and light waves are nearly identical, and under the right circumstances it should be possible to create a coherent beam of sound waves inside a solid block of material.

Because sound waves travel more slowly, the wavelength of sound at a particular frequency is much shorter than that of light.

Sound waves of short wavelength could have some extremely useful practical applications, according to Kerry Vahala, a physicist at the California Institute of Technology in Pasadena.

For example, beams of sound waves could provide extremely high-resolution ultrasound machines capable of resolving objects that even the most powerful microscope could miss.

To isolate just one frequency, Vahala and his group used a laser to drive two silica drums just a few tens of micrometres across.

Light from the laser ran around the rim of the drum heads like a car around a racetrack. Its energy made the two heads vibrate at specific frequencies.

By looking at how the laser flickered as it exited the drums, Vahala and his team were able to verify that a single frequency was being amplified in one of the drum heads.

When the system crossed a threshold, that head beat with a pure tone.

Adjusting the gap between the two drums changed the feedback between them and allowed the team to tune the frequency of the sound.

A second group of researchers used an entirely different setup to make a saser sing.

Tony Kent of the University of Nottingham, UK, and his team began with a tower made of alternating layers of semiconducting gallium arsenide and aluminium arsenide.

When a laser struck the top of the tower, it created a sound that caused electrons in the gallium arsenide to quantum-mechanically tunnel through the aluminium arsenide layer.

The tunnelling amplified the sound at a specific frequency, which in turn caused more electrons to tunnel.

"The amplification effect was only briefly coherent, but it nevertheless demonstrates the saser concept," Kent said. (ANI)

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