A New Way to Guide Light in Optical Fibers

Many of our phone conversations and e‐mail communications race to their destinations over optical communication links that rely on total internal reflection to guide pulses of light down hair‐width fibers of glass. Despite their prodigious bandwidth, these glass fibers will be hard pressed to meet the heavy traffic demands being placed on them by the exploding use of the Internet. Recently, researchers from the US and UK have demonstrated another way to transmit light waves though narrow channels: By surrounding a hollow core with photonic bandgap structure. Their achievement opens the way for guiding light with little or no loss through an evacuated channel. That’s important because the interaction of light with glass now limits the maximum power that one can transmit with today’s glass‐core fibers. It’s not possible to have hollow cores with fibers that rely on total internal reflection because the core must have a larger index of refraction than the cladding, and there’s no solid material that has an index of refraction less than one.