Getting photons to interact generally requires extreme conditions—sending them through a dense cloud of ultracold atoms or using super-intense laser light, for example. But now researchers have shown theoretically that photons can be made to interact using very weak light in an ordinary slab of silicon by cutting a precise series of air spaces within the material. The effect could simplify the development of photon-based computing devices, either classical or quantum, using ordinary materials.
In vacuum or air, two light waves will pass through one another, since photons do not interact. In a nonmetallic solid such as silicon, photons can interact through the so-called Kerr effect—the presence of one photon changes the material’s index of refraction, altering how a second photon behaves within it. Photonic interactions within materials would be useful for making photon-based logic gates—the components of an optical computer—yet the Kerr effect usually requires extremely strong electric fields produced by intense laser beams.
But now Hyongrak Choi, Mikkel Heuck, and Dirk Englund of the Massachusetts Institute of Technology, Cambridge, have shown theoretically that similarly strong fields can also be realized by introducing a precise pattern of air spaces in the material. With modern fabrication technology, they suggest, it should be possible to achieve photon interactions even with very weak light.