The ability to create phonons and then steer them using laser beams could lead to a new generation of applications, say physicists.
Zap an optical fibre with a couple of laser beams and the resulting interference pattern causes an interesting effect--it squeezes the material, an effect known as electrostriction. This creates a compression wave called a phonon, a packet of sound, which travels along the fibre.
Not to be outdone, phonons also influence light because they change the refractive index of the material. This bends light and alters its frequency, an effect known as Brillouin scattering.
After that, things get complicated. This mechanism sets in train a complex set of feedback effects in which photons generate phonons which influence the photons and so on.
The problem is understanding what's going on. The ability to influence sound with light, and vice versa, could have interesting applications. But without an accurate model of this phenomenon, it's hard to exploit.
That looks set to change. Until now, physicists have sought to understand the phenomenon by assuming the phonons have a particular form and working out how this influences the incident light. In other words, they ignore feedback effects.
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