We all know what happens when you throw a stone in a lake or step in a puddle, but what happens when you shine a laser on a material? As it turns out, the results can be quite similar. Researchers at the University of California, San Diego have recently discovered this behavior, which may lead to some interesting applications.
The researchers were working with a piece of hexagonal boron nitride, which are sheet-like in shape and can be bound together by van der Waals forces, a weak bond. As an atomic force microscope was scanning over the material, a laser was aimed at its tip, and as the tip moved near the edges, it detected an interference pattern. This pattern was being caused by atoms vibrating from the laser light, and those vibrations rippling out, bouncing off the material's edges, and returning to interfere with itself. Specifically called phonon polaritons, the waves of the atoms vibrating have a much shorter wavelength than that of light, and the researchers found the frequency can be tuned by altering the thickness of the material, and by adding impurities for the waves to reflect off of.
With the incredibly small wavelengths of these phonon polaritons, it may be possible to exploit them for moving information in very tight places, creating images of extremely high resolution, or controlling the heat flow in nanodevices. Ironically part of the reason this occurs in hexagonal boron nitride is because it is an insulator, preventing the electrons from dissipating the energy over short distances.