A 250 µm voyage

Specially designed, extremely small metal structures can trap light. Once trapped, the light becomes a confined wave known as surface plasmons. The surface plasmons are represented here by the blue waves, which begin at the pump beam and are detected 250 micrometers away by the probe beam, traveling at almost as fast as light through the air. Credit: Hess et al./Nano Lett.

It is all relative. A span of 250 µm, a fourth of a mm, would hardly qualify for a "voyage". And yet, if you are at a nm scale 250 µm is quite a length (it would compare to a travel of 250km at our human scale). And this is what makes researchers excited when seeing plasmons that can travel that distance.

Researchers at the Northwest National Laboratory have run a series of experiments demonstrating the possibility of having plasmons (quasi particles made of lightwaves) travelling up to 250µm.

This is farther away than it was thought possible. Plasmons are explained by quantum mechanics representing one aspect of the duality particle/wave of light (and electrons). Like electrons they could be used for communication but the problem so far was the very limited travelling span a plasmon could move, so short that it cannot be exploited for communications. With this experiment it has been shown that the "particle-like" form for of a lightwave can be maintained for distances up to 250µm which would make it possible to create chips with transistors interacting at the speed of light, basically using plasmons to replace electrons (which are very slow).

For the experiment researchers have used one laser to generate plasmon of a gold surface (pump) and another one to probe the ripples generated by plasmons moving on the surface detecting their position and speed.

It could be a twist to keep the performance increase of chips in line with the Moore's law.

Author - Roberto Saracco

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