Daniel Wasserman

An ordinary piece of semiconductor weakly changes the color of light passing through it. For decades, physicists worked around this limitation by placing the crystal in clever surroundings, but the material itself remained the same. Now researchers have assembled a "sandwich" of alternating thin layers of gallium arsenide and aluminum gallium arsenide.

A film of aluminum nitride, as thin as a soap bubble, hangs above a mirror with a micrometer-sized air gap between them. When invisible infrared light with a wavelength of about 15 micrometers hits it, the film starts to vibrate in sync with the light, like a string that responds only to its own note.