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Past Winner
2008 E.W.R. Steacie Memorial Fellowship

Pierre Berini

Electrical Engineering and Physics

University of Ottawa

Pierre Berini
Pierre Berini

Not too many people can perform the kinds of tricks with light that electrical engineer Pierre Berini can. Under the right conditions, he can make it travel along a metal surface in the form of a wave known as a surface plasmon.

His field is called surface plasmon photonics, or plasmonics for short, and Dr. Berini’s contributions have earned him a 2008 NSERC E.W.R. Steacie Memorial Fellowship. It’s technology that offers the possibility of creating integrated circuits that work with light rather than electricity. Just as optical fibres can carry far more data than electrical wires, so circuits that use plasmons could increase the capacity of electronic devices.

Plasmons are generated when light shines perfectly along the edge of a metal surface. They are typically a very short lived phenomenon, however. For example, shining a flashlight along the edge of a mirror would generate plasmons that traveled less than 10 microns at visible wavelengths before dissipating. Because of their short travel distance, they seemed to have little practical use in circuits (typical components of integrated circuits tend to be about a millimetre long, 100 times the normal travel distance of a plasmon). They were in fact regarded as a problem for many years, since optical devices had to be engineered so as to keep light away from metal regions in order to prevent the losses and other negative effects they would cause.

The conventional wisdom began to change in the 1990s, as Dr. Berini and other researchers took a closer look at the possibility of generating plasmons propagating over longer distances. “We were investigating various geometries of metal films to see if these things were always deleterious,” he explains. “We found a geometry that allows surface plasmons to be confined by a stripe while propagating over centimetres. That, all of a sudden, becomes useful within the context of integrated optics. You’ve got enough length there to do all kinds of useful things on a chip.”

The discovery of a plasmon-friendly geometry fuelled the last 10 years of his group’s research, and he expects it to lead to the next 10 as well. And he is not alone – discoveries such as his have helped spark a resurgence in interest in plasmonics, reflected in a sharp increase in the number of papers and conferences devoted to this area. Developments in nano-fabrication techniques have also increased the possibilities for using plasmons productively.

Among Dr. Berini’s developments is the invention of the first-ever optical circuits that use metal to guide light waves. These devices send light in the form of plasmons down metal tracks on a substrate, similar to the way electricity flows in a circuit built on a chip. By manipulating the plasmons, he can perform a number of functions in an integrated fashion. So far, he has made wavelength filters, variable attenuators and modulators, with such devices as sensors, and plasmonic amplifiers and lasers on his “to do” list.

Finding commercial applications for research is common in his field, but Dr. Berini’s technology transfer record is exceptional. In order to exploit the commercial aspects of his research, he formed Spectalis Corp., which attracted an unprecedented amount of venture capital compared to most university spin-off deals. As a consultant, he has also helped other companies improve their products, notably QPS Technology and Optiwave.

Despite the commercial potential of his work, Dr. Berini did not design his research program with a view to solving industrial problems. “We were looking at these metal waveguides simply from a curiosity standpoint,” he says, “not knowing whether anything useful would come of it.”

But useful it has been, leading to filing no less than 17 patents to date. As part of his Steacie Fellowship, he plans to continue investigating and developing ways to put plasmons to practical use.

Biosensing is the most promising application so far, because the nature of plasmons will allow for the creation of far more sensitive detectors than are currently available. He hopes to create a sensing platform flexible enough to detect biological, chemical or gaseous substances in a variety of settings. One of the challenges involves the fact that the structure supporting a sensor must be index-matched to the substance around it, that is, it has to refract light to exactly the same degree. That’s feasible enough for detectors immersed in water or blood, but gets more difficult for those in air. Dr. Berini’s solution is to mount the sensor on an ultra-thin membrane, strong enough to support it, but with a thickness measured in tens of nanometres, thin enough that the light refraction in the membrane becomes negligible.

And that’s just the beginning. In theory, plasmonic circuits could play a role anywhere that electronic circuits are currently used. As he continues to fine-tune the materials, processes and theoretical models, building lasers is one of his next goals. Further into the future, he says using plasmons for optical communications networks and devices could also become feasible.