Photonic Crystals

The Institute has awarded this year’s Newton Medal to Eli Yablonovitch for his work on photonic crystals. What are they?

Photonic crystals
Credit: US Naval Research Lab

The IOP’s premier annual award, the Newton Medal and Prize, has been awarded to Eli Yablonovitch for his work in photonics, and particularly photonic crystals.

Their principle is similar to how the properties of semiconductors enable the creation of electronic devices. Photonic crystals have a band gap that allows some wavelengths of light to pass but not others, allowing unprecedented control over the behaviour of light.

Research into photonic crystals began to accelerate after Yablonovitch and Sajeev John published two papers on them. But since they’re difficult to fabricate they were limited to manipulating microwaves until 1996 when Thomas Krauss made the first photonic crystal that works with visible light.

Krauss’s work led to borrowing techniques from the semiconductor industry to produce photonic crystals – but only two-dimensional ones. The first three-dimensional photonic crystal had been made five years earlier by Yablonovitch by drilling holes in layers of transparent material – it’s now named yablonovite after its pioneer.

Three-dimensional photonic crystals are yet to find commercial applications. However one-dimensional ones are used variously for coating lenses or for colour-changing paint, while two-dimensional ones are utilised for a new class of optical fibre – photonic-crystal fibres.

Where more traditional optical fibres uses differences in refractive indices to guide light, photonic-crystal fibres use the structural properties of their construction material to exercise much greater control over light and are used for applications such as high-speed communications, fibre lasers and power transmission.

It’s thought that three-dimensional crystals could be used in components for optical computers, which, not being limited by the relatively slow speed of electrons, could be more than 10 times faster than a regular computer – if difficulties in their manufacture can be overcome.