URBANA, Ill., July 18, 2014 — Nanoantennas can be used like traditional photographic film to record light at distances smaller than its own wavelength. This could mean big things for the future of optical data storage. To make the new pillar bowtie nanoantenna (pBNA) arrays, researchers at the University of Illinois at Urbana-Champaign used gold nanoantennas on silicon dioxide pillars. These act as a multifunctional plasmonic film that can record near-field optical information. The film is used with a standard optical microscope that serves as a nanocamera. And, unlike conventional photographic film, this nanocamera technique can produce results in real time. The Illinois “I” logo, as recorded by the plasmonic film. Each bar in the letter is approximately 6 µm wide. Courtesy of Toussaint Research Group/University of Illinois. In the study, the researchers found that the plasmonic film structure could be used for direct laser writing of images or to record optical vector beams’ polarization structures. To demonstrate this, they used various written patterns — including the university’s logo and an animation of a stick figure walking — that were either holographically transferred to the pBNAs or laser-written using steering mirrors. “In our new technique, we use controlled heating via laser illumination of the nanoantennas to change the plasmonic response instantaneously, which shows an innovative but easy way to fabricate spatially changing plasmonic structures,” said Illinois graduate student Abdul Bhuiya, adding that this opens “a new avenue in the field of nanotech-based biomedical technologies and nano-optics.” The fundamental bit size of the film is set by spacing the antennas at 425 nm, but the film’s pixel density can be reduced by fabricating smaller array spacing and a smaller antenna size, or by employing a more tightly focused lens for recording optical information, the researchers said. “For a standard Blu-ray/DVD disc size, that amounts to a total of 28.6 GB per disk. With modifications to array spacing and antenna features, it’s feasible that this value can be scaled to greater than 75 GB per disk,” said Illinois graduate student Brian Roxworthy. “Not to mention, it can be used for other exciting photonic applications, such as lab-on-chip nanotweezers or sensing.” Among other photonic applications, the plasmonic film can create optofluidic channels without walls, the researchers said. The research was published in Nano Letters (doi: 10.1021/nl501788a). For more information, visit www.engineering.illinois.edu.