Laser pulse faster than light11/28/2022 As such, they are elusive species that only live transiently during illumination.īecause the graphene is connected to gold, both real and virtual charge carriers are absorbed by the metal to produce a net current. “Virtual” charge carriers are electrons that are only set in net directional motion while the laser pulse is on.“Real” charge carriers are electrons excited by light that remain in directional motion even after the laser pulse is turned off.In trying to reconcile the experimental measurements at Erlangen with computational simulations at Rochester, the team had a realization: In gold-graphene-gold junctions, it is possible to generate two flavors-“real” and “virtual”-of the particles carrying the charges that compose these bursts of electricity. The research groups of Franco and of FAU’s Peter Hommelhoff have been working for several years to turn light waves into ultrafast current pulses. The breakthrough: Harnessing real and virtual charge carriers Further, the direction and magnitude of the current can be controlled simply by varying the shape of the laser pulse (that is, by changing its phase). Laser pulses can produce electricity far faster than any traditional method-and do so in the absence of applied voltage. The ultrashort laser pulse sets in motion, or “excites,” the electrons in graphene and, importantly, sends them in a particular direction-thus generating a net electrical current. This is done, for example, by illuminating tiny graphene-based wires connecting two gold metals. LASER PULSE FASTER THAN LIGHT HOW TOIn recent years, scientists have learned how to exploit laser pulses that last a few femtoseconds to generate ultrafast bursts of electrical currents. Lasers generate ultrafast bursts of electricity “This is a great example of how fundamental science can lead to new technologies,” says Ignacio Franco, an associate professor of chemistry and physics at Rochester who, in collaboration with doctoral student Antonio José Garzón-Ramírez ’21 (PhD), performed the theoretical studies that lead to this discovery. That is almost a million times faster than today’s computers operating with gigahertz clock rates, where 1 petahertz is 1 million gigahertz. The researchers’ advances have opened the door to information processing at the petahertz limit, where one quadrillion computational operations can be processed per second. The feat, reported on May 11 in the journal Nature, was accomplished by harnessing and independently controlling, for the first time, the real and virtual charge carriers that compose these ultrafast bursts of electricity. Now, researchers at the University of Rochester and the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have made a decisive step in this direction by demonstrating a logic gate-the building block of computation and information processing-that operates at femtosecond timescales. “We now know that lightwave electronics is practically possible.” - Tobias Boolakee
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