Gallium is in control of plasmon waves
EW Technology 17/03/2004 – Gallium is in control of plasmon waves
Gallium is in control of plasmon waves Harry Yeates
Researchers at the University of Southampton have developed a model for a device in which surface plasmon-polariton waves travelling in a metal-on-dielectric waveguide can be controlled. In a paper to be submitted shortly, they also claim to have backed up their predictions experimentally.
Plasmon-polariton waves are coupled optical and electronic excitations that propagate at the border between a very good metal, like gold, and a dielectric. The work at Southampton, led by Professor Nikolay Zheludev, is aimed at developing techniques for controlling these signals, opening the way to so-called ‘active plasmonics’ that could be used to transport information.
The waves travel only tens and hundreds of microns, but they are very compact, says Zheludev. In the space of a few tenths of a micron you can bend them several times, you can direct them and you can do a lot in a very small area, so they are very good for integration. All this is fine until you have a way of controlling them.
To enable control of the signals, Zheludev inserts a section of gallium in the gold side of a gold-on-silica waveguide. Gallium readily undergoes a phase change when thermally or optically excited, altering the transmission properties of the waveguide.
With gallium it is quite easy to switch it from what is essentially a semiconductor phase, to a phase which is electronically as good as gold, explains Zheludev. Calculations suggest that switch-on and switch-off times are of the order of a few picoseconds – several orders of magnitude faster than existing optomechanical switches.