Phys. Rev. Lett. 104, 083901 (2010)

Since the advent of lasers, researchers have strived to build an acoustic equivalent — devices that can amplify and emit sound waves at a single frequency.

Kerry Vahala and his group at the California Institute of Technology in Pasadena fired a light laser at two micrometre-scale silica drums. The light raced around the rim of the drums, causing the drum heads to vibrate. Once the system crossed a threshold, one head beat with a pure, amplified tone — an effect that the researchers verified by looking at how the laser flickered as it exited the drums.

Such devices may prove useful in electronics and ultrasound applications.