To understand the ambitions of Marin Soljacic, think of what the first semiconductor transistors did for the speed and power of computer circuitry--and then think photons instead of electrons.
By calculating the behavior of light in structures called photonic crystals, Soljacic is paving the way for devices that can process information at ultrafast speeds using light alone. The crystals' microscopic honeycombs shut out light of any but a few particular wavelengths; as a consequence, they could offer a way to guide data-carrying light beams within microprocessors.
Soljacic has also shown how photonic crystals can enable light beams to interact and to control one another, so that photonic devices can carry out logic operations.
The all-optical computers predicted in the 1980s haven't materialized, he says, because the effects on which photonic interactions depend are usually so weak that they appear only with beams too intense to be of practical use in microchip devices. But Soljacic has shown how photonic crystals can be designed to dramatically boost these optical effects so that they will occur even with very low-power light beams.
Ultimately, he thinks, it should be possible to use a single photon to control another in a photonic-crystal device. This would reduce energy consumption and heat production enough to make optical information processing practical--and it raises the possibility of all-optical quantum computers, which would expand computer power beyond recognition.
--Philip Ball
