Phased arrays of nanoscale antennas allow control of visible light

Ars Technica : Arrays of antennas that transmit in phase with each other are used to boost, shape, and focus the signal they are sending. Traditionally, they have been used with radio waves, whose long wavelengths lead to large devices. Jie Sun of MIT and his colleagues have now created a phased array of antennas, each just 400â700 nm in length, which can transmit visible light. On a single silicon chip, the researchers were able to fit 4096 antennas arranged in a 64âÃâ64 grid with sides of 9 µm. Light was fed to the array by a fiber-optic cable, and each antenna handled a range of wavelengths, so the array as a whole was able to create multicolor images. The researchers demonstrated the array’s capabilities by transmitting an image of the MIT logo, which required combining the light from each antenna in precise ways. This nanophotonic phased array may be the first step toward nanoscale devices that rely on control over the shape of light emission. Such devices could find applications in optical communications, holography, and medical imaging.