Photons may someday replace electrons inside cellphones, automobiles and other products. This shift got a recent boost with the development of an ultrafast, ultrasmall optical switch. The new device, developed by a team from Vanderbilt University, the University of Alabama at Birmingham and Los Alamos National Laboratory, is now the smallest of the existing ultrafast optical switches, representing a major breakthrough in light-detecting electronic technology. Containing individual switches measuring only 200 nm in diameter, this new optical device can turn on and off trillions of times per second. It is made of a metamaterial consisting of nanoscale particles of vanadium dioxide that are deposited on a glass substrate and coated with a nanomesh of gold nanoparticles. VO2 switches are ideal for optoelectronics applications, the researchers said. Besides being ultrafast and miniature in size, they are compatible with current integrated circuit technology. The device can operate in the visible and NIR spectra, and generates low heat. The researchers had previously used lasers to prompt a phase change in VO2 nanoparticles, and had taken the process further to determine whether it could be done with electrons, too. “Not only does it work, but the injection of hot electrons from the gold nanoparticles also triggers the transformation with one-fifth to one-tenth as much energy input required by shining the laser directly on the bare VO2,” said Richard Haglund, a professor at Vanderbilt. The properties of VO2 nanoparticles have long been known, but theoretical and computational studies of the semiconductor-to-metal transition have only begun within the past few years. The research is published in Nano Letters. For more information, visit: www.vanderbilt.edu.