Sound lasers are created by manipulating phonon particles, holding significant potential for applications in medicine and deep-sea exploration.
Chinese scientists have made a significant breakthrough in developing a stronger laser from sound waves instead of light, as reported by SciTechDaily on October 4. The new research was published in the journal eLight.
Sound generated inside a tiny silicon dioxide sphere. (Photo: IFL Science).
Conventional lasers are already fascinating. They were first created by humans in the 1960s. “Lasers produce a narrow beam of light in which all light waves have very similar wavelengths. The laser light waves travel together, with their peaks aligned, or in phase. This is why laser beams are very narrow, very bright, and can focus on a very small point,” NASA explains.
Although sound and light have distinct differences, physicists have researched creating sound lasers by manipulating phonons.
“Just as photons make up a beam of light, phonons—indivisible quantum particles—constitute a beam of sound. These particles arise from the collective motion of trillions of atoms, similar to a ‘wave’ in a sports arena due to the movement of thousands of fans. When you listen to a song, you are hearing this stream of tiny quantum particles,” explains Andrew N. Cleland, a professor at the Pritzker School of Molecular Engineering at the University of Chicago.
Initially used to explain the heat capacity of solids, phonons are predicted to follow quantum mechanics rules similar to photons. However, the technology for producing and detecting phonons still lags significantly behind that of photons.
Previously, phonon lasers formed from small objects were affected by weak and inaccurate sound waves, reducing their utility. The new method addresses this issue by “locking” sound waves in a more stable and stronger state.
In the recent study, the team of Chinese scientists took a microsphere of silicon dioxide (SiO2) and suspended it using light beams. This caused the sphere to vibrate, generating sound inside that resembled a beep with a very high pitch, exceeding human hearing capability. They then began to control the vibrating microsphere with an alternating electric field to create resonance, amplifying the sound waves by 1,000 times at those frequencies.
The experiment was conducted in a vacuum environment to better measure the sound waves (which are confined within the microsphere), bringing them closer to creating sound lasers that can be used for various purposes, from exploring and mapping the ocean acoustically to enhancing medical imaging techniques. Sound lasers could also find applications in materials science, quantum computing, and many other fields.
