Bowtie-Funnel Combo Best for Conducting Light

The Vanderbuilt team developed structure that’s part bowtie, part funnel that conducts light powerfully and indefinitely, as measured by a scanning near field optical microscope. (Source: Ella Maru Studio)

Running computers on virtually invisible beams of light rather than micro­electronics would make them faster, lighter and more energy efficient. A version of that tech­nology already exists in fiber optic cables, but they’re much too large to be practical inside a computer. A Vander­bilt team found the answer in a formula familiar to college physics students. Sharon Weiss, her doctoral student, Shuren Hu, and colla­borators at the IBM T. J. Watson Research Center and Uni­versity of Tech­nology in Troyes, France, developed a structure that’s part bowtie, part funnel that concen­trates light power­fully and nearly indefinitely, as measured by a scanning near field optical micro­scope. Only 12 nanometers connect the points of the bowtie.

“Light travels faster than elec­tricity and doesn’t have the same heating issues as the copper wires currently carrying the infor­mation in computers,” said Weiss. “What is really special about our new research is that the use of the bowtie shape concen­trates the light so that a small amount of input light becomes highly amplified in a small region. We can poten­tially use that for low-power mani­pulation of infor­mation on computer chips.”

Using two principles from Maxwell’s equations and applying boundary condi­tions that account for materials used, Weiss and Hu combined a nano­scale air slot surrounded by silicon with a nano­scale silicon bar sur­rounded by air to make the bowtie shape. “To increase optical energy density, there are generally two ways: focus light down to a small tiny space and trap light in that space as long as possible,” Hu said.

The challenge is not only to squeeze a compara­tively elephant-size photon into refrigerator-size space, but also to keep the elephant volun­tarily in the refri­gerator for a long time. It has been a prevai­ling belief in photonics that you have to compro­mise between trapping time and trapping space: the harder you squeeze photons, the more eager they are to escape. Weiss said she and Hu will continue working to improve their device and explore its possible appli­cation in future computer platforms. (Source: Vander­built Univ.)

Reference: S. Hu et al.: Experimental realization of deep-subwavelength confinement in dielectric optical resonators, Sci. Adv. 8, eaat2355 (2018); DOI: 10.1126/sciadv.aat2355

Link: Dept. of Electrical Engineering and Computer Science (S. Weiss), Vanderbilt University, Nashville, USA

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