New Nanoscale Light Switch

Overlaid scanning electron microscopy (SEM) and optical images showing an ENGRAVE nanowire that is periodically modulated at one end. (Source: UNC-Chapel Hill)

Researchers from the Univer­sity of North Caro­lina at Chapel Hill have reached a new milestone on the way to optical computing, or the use of light instead of elec­tricity for computing. They explored a new way to select and send light of a specific color using long silicon wires that are several hundred nano­meters in diameter and their work enabled a new type of nanoscale light switch that can turn on and off the trans­mission of one color of light over very long distances.

Optical computing tech­nology promises many benefits. Swapping electrons for light-based techno­logy would mean that the computers of the future won’t overheat and will run much faster. “In the past there hasn’t been a controlled method for selec­tively sending light down nanoscale wires, so optical technology has either used much larger structures or wasted a lot of light in the process,” said James Cahoon, asso­ciate professor of chemistry in the College of Arts and Sciences at UNC-Chapel Hill. “We found a way to turn on and off the trans­mission of a specific color of light, and it repre­sents an impor­tant step towards the more controlled, effective use of light that would enable optical computing.”

The research team deve­loped the „Encoded Nano­wire Growth and Ap­pearance through VLS and Etching (ENGRAVE)“ technique, which can create complex shapes in nanowires. They then achieved selective light trans­mission through precise diameter modu­lation with the ENGRAVE technique. This was the first report of direct use of a Mie reso­nance, a light scat­tering property of nanowires, for guiding light in a nano­wire.

This work is a step forward for optical computing and will help enable further advances in the tech­nology. The team’s findings can enable down­sizing of the optical components needed to develop computers based on light instead of on elec­tricity. By minia­turizing these components, they can be more easily inte­grated with the existing electronic compo­nents in computers. Addi­tionally, the color of light conducted by the wires in this study is sensi­tive, with the color changing as the environ­ment changes. Thus, these structures can be used as a new type of sensor, in which the color of the conducted light senses the environ­ment of the wire. (Source: UNC)

Reference: S. Kim et al.: Mie-coupled bound guided states in nanowire geometric superlattices, Nat. Commun. 9, 2781 (2018); DOI: 10.1038/s41467-018-05224-2

Link: Nanomaterials & Photonics (J. F. Cahoon), Dept. of Chemistry, University of North Carolina-Chapel Hill, Chapel Hill, USA

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