Scientists at Yale University in Connecticut have found a way to extend the lifetime of sound waves traveling through glass. Their discovery could help to optimize performance of optomechanical systems.

The peculiar nature of glass – it is an excellent light conductor but a poor conductor of sound at cryogenic temperatures – has stymied development of improved sound transmission.

Fiber optic and cable.Fiber optic and cable. At room temperature, a wine glass struck with a fork will ring for several seconds. If the glass is in a room with other loud sounds, this extra noise will amplify the sound waves given off by the ringing glass. The amplification increases the amount of time the glass will ring.

Physicists ultimately explained the slow absorption of sound waves by proposing localized absorbers – “acoustic atoms” – that interact with sound waves the same way atoms interact with light. At low temperatures the amplitude of a sound wave affects how long it will ring. The acoustic atoms cause sound to vibrate at different amplitudes, analogous to turning on a stereo. The longer the stereo is on, the longer the sound will last.

This finding informed the researchers’ approach. They shone a laser into the core of a fiber optic waveguide and probed and generated sound waves at the fiber’s core. By generating an intense acoustic wave at one frequency (“turning on the stereo”) and probing at another (“tapping a wine glass”), the researchers extended the lifetime of a sound wave.

“Our work takes an important step toward engineered sound dynamics in glass,” says Peter Rakich, assistant professor of applied physics and physics at Yale and principal investigator of the study, which is published in Nature Materials.

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