New Form of a Laser for Sound

Illustration of a phonon laser using an optically levitated nanoparticle. (Source: A. N. Vamivakas & M. Osadciw, RIT)

The optical laser has grown to a $10 billion global tech­nology market since it was invented in 1960, and has led to Nobel prizes for Art Ashkin for developing optical tweezing and Gerard Mourou and Donna Strick­land for work with pulsed lasers. Now a Rochester Institute of Tech­nology researcher has teamed up with experts at the University of Rochester to create a different kind of laser – a laser for sound, using the optical tweezer technique invented by Ashkin.

The researchers propose and demonstrate a phonon laser using an optically levi­tated nano­particle. The researchers studied the mechanical vibrations of the nano­particle, which is levi­tated against gravity by the force of radiation at the focus of an optical laser beam. “Measuring the position of the nano­particle by detecting the light it scatters, and feeding that information back into the tweezer beam allows us to create a laser-like situation,” said Mishkat Bhatta­charya, associate professor of physics at RIT. “The mechanical vibrations become intense and fall into perfect sync, just like the electro­magnetic waves emerging from an optical laser.”

Because the waves emerging from a laser pointer are in sync, the beam can travel a long distance without spreading in all directions – unlike light from the sun or from a light bulb. In a standard optical laser the properties of the light output are controlled by the material from which the laser is made. Interes­tingly, in the phonon laser the roles of light and matter are reversed – the motion of the material particle is now governed by the optical feedback.

“We are very excited to see what the uses of this device are going to be – especially for sensing and infor­mation processing given that the optical laser has so many, and still evolving, appli­cations,” said Bhatta­charya. He also said the phonon laser promises to enable the inves­tigation of fundam­ental quantum physics, including engi­neering of the famous thought experiment of Schrödinger’s cat, which can exist at two places simultaneously. (Source: RIT)

Reference: R. M. Pettit et al.: An optical tweezer phonon laser, Nat. Phot., online 1 April 2019; DOI: 10.1038/s41566-019-0395-5

Link: Center for Coherence and Quantum Optics, University of Rochester, Rochester, USA

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