Scientists have designed a device to achieve the seeming-impossibility of confining light to a space with dimensions smaller than its wavelength. The deceptively simple device is a pipe with a tiny bore, and walls made of so-called transformation optical materials. To understand how these materials work, consider first what happens when light hits water. Light changes directions, because of the difference in the refractive index of water versus air; it hits the water at one angle and travels through it at a different angle. Transformation optical materials are designed with a continuously changing refractive index, so that light can be made to travel in a circle rather than a straight line. Scientists have demonstrated that this principle can confine light to a space smaller than its own wavelength, while losing little energy. These findings have huge implications for the storage and manipulation of optical information as well as studies of the fundamental properties of light.
Creating Electromagnetic Cavities using Transformation Optics