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Five Key Dates © C. SCHRÖDER/UNISTRA 1954 Born on January 30 in Oslo (Norway) 1964 Moved to Paris with his family 1988 Joined NEC Corporation in Tokyo, where he discovered a new property of light the following year 2005 Director of the Institute of Supramolecular Science and Engineering (ISIS) until 2012 2014 Awarded the Kavli Prize in Nanoscience PROFILE 25 SPRING 2015 N° 37 and time again, with the same result. Even more disconcertingly, it appeared as if the light passed through an area three times larger than that occupied by the holes, i.e., as if it could travel through the metal. For eight years, Ebbesen endeavored to solve the mystery, while pursuing other research at NEC. Yet he never gave up. “I had enough experience to know that I wasn’t making an experimental error,” he says. “Moreover, some of my colleagues, like fellow scientist Shunji Kishida of NEC Labs, kept urging me to keep going and not lose heart.” And the light dawned They were well advised to do so, for their support and Ebbesen’s perseverance allowed this strange phenomenon to be well understood today. In fact, the array of holes behaves like an antenna. The free electrons randomly gather together on the metal plate—a conducting surface— in groups called plasmons. These plasmons adapt themselves to the periodicity of the array, in other words the spacing between the holes. They are said to come into resonance with it, forming a sort of magnifying glass above each hole: they focus the photons that fall onto the holes, and re-emit them. “Although initially the probability of a photon passing through the holes is very low, the ‘magnifying glasses’ considerably increase this probability,” Ebbesen explains. “This concentrating effect is so high that more light is transmitted than allowed by the surface area occupied by ebbesen@unistra.fr the holes.” This finding has a wealth of applications, such as improving the quality of lasers or increasing the efficiency of optical fibers. This discovery in the 1990s of a new property of light, thought for decades to hold no more secrets, certainly caused a stir. And when Ebbesen gave his speech at the Kavli Prize award ceremony, the astrophysics laureates, who use light to probe the Universe, were surprised. “I keep telling my students that many things we have no inkling about remain to be discovered,” he adds. “Didn’t Albert Einstein say: ‘As our circle of knowledge expands, so does the circumference of darkness surrounding it.'” His latest passion: hybrid states Ever since his breakthrough with arrays of holes, Ebbesen has never stopped exploring the unknown. In addition to the Kavli Prize, he has been awarded several prestigious distinctions (including the Agilent Europhysics Prize, for his work on nanotubes), and jointly holds some 30 patents. And at 60, he has no intention of calling it a day. “I’m currently working on hybrid light-matter states, and I’ve never had so much fun in my life!” he enthuses. History repeats itself: after re-reading the article by Haroche, whose work—along with that of Claude Cohen- Tannoudji—is a constant source of inspiration, he took on this new challenge. “With my teams, we’ve managed to change the properties of matter (conductivity, chemical reaction rate, etc.) by placing molecules on an array of nano-holes or by using mirrors,” he explains. “We don’t even need any light: quantum vacuum fluctuations, the very ones that may partly give rise to dark energy, cause matter to come into resonance with the array, a phenomenon that modifies the molecules.” No doubt this bodes well for fascinating new papers. And it is further proof, if one were needed, that genuine discoveries do not stem from planned, applied research, but rather from insatiable, childlike curiosity. ii “I keep telling my students that many things we have no inkling about remain to be discovered.”


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