Light photonic crystals clinch physics medal

The US physicist who first discovered "photonic crystals" which can repel, trap and steer light is to receive the Newton Medal, the BBC can reveal.

This is the highest honour given by the Institute of Physics in London.


Prof Eli Yablonovitch of the University of California, Berkeley, proposed and created the crystals in the
1980s.


They are now used in data processing and in wave guides for laser surgery; they have also been discovered in bird feathers and the skin of chameleons.


"I'm very, very honored," Prof Yablonovitch told the BBC.|

His seminal description of photonic crystals was published in 1987 when these materials had never been manufactured, and were not known by that name.


It is the second most-cited paper ever published in the prestigious journal Physical Review Letters.

Surprisingly enough, the same concept was described in a second paper three weeks later by Sajeev John, now a professor at the University of Toronto.

Both researchers built on an idea put forward 100 years earlier in 1887, by British physicist Lord Raleigh. He suggested that a material with a repeating, regular structure - such as a crystal - could block light of particular wavelengths.

This happens, Raleigh calculated, because if the light has a wavelength that is similar to the size of the repeated units in the structure, then the waves reflected off its internal surfaces will interfere and cancel each other out. That produces a "stop band" (later called a "photonic bandgap") - a range of light wavelengths that will be repelled by the crystal.

"[Lord Raleigh] developed the idea of the one-dimensional photonic crystal," Prof Yablonovitch explained.

"That's something that we've lived with for over 100 years. But over that entire period, no-one really thought of extending Raleigh's idea into two and three dimensions."

That was where he and Prof John stepped in, almost simultaneously - at a time when controlling light was a subject of great interest, for applications such as optical fibres and solar cells.

"It's just one of those ideas - maybe after 100 years the time had come, and two people thought of it within a few months of one another," Prof Yablonovitch said.

But, he added, expanding the idea into more dimensions, to block light in all directions, was very difficult because "it wasn't clear what the crystal structure should be".