The metamaterial hyperlens, the light-colored slivers are gold and the darker ones are a transparent thermoplastic. Credit: University at BuffaloA hyperlens that resembles the children’s toy Slinky is set to revolutionize cancer diagnostics, nanoelectronics manufacturing and our ability to observe single molecules, according to its US inventors.
The resolution of a conventional optical microscope is limited by the diffraction limit of light. New imaging techniques are therefore needed to visualize objects smaller than the wavelength of light. One of the most promising approaches is the use of so-called hyperlenses.
“A hyperlens overcomes the diffraction limit [of light] by transforming evanescent waves responsible for imaging subwavelength features of an object into propagating waves,” says Natalia Litchinitser, who led the research team at the University at Buffalo. “Once converted, those formerly decaying (evanescent) components [that are] commonly lost in conventional optical imaging (using conventional lenses) can now be collected and transmitted using standard optical components.”
To date, most of the optical hyperlenses designed have been comprised of tiny concentric rings of silver and an insulating (dielectric) material. These only work within a narrow range of wavelengths and suffer from large losses in resonance, explains Litchinitser. “We designed a hyperlens with a fan-shaped layered structure consisting of alternating metal and dielectric nanoscale layers.” The lens looks like a Slinky – a popular spring toy that walks down stairs – suspended in motion. Her team demonstrated that this hyperlens works well across a wide range of wavelengths and only has minimal resonance losses. The work is published in Nature Communications [Sun, J., Shalaev, M. I. & Litchinitser N. M., Nat. Commun. (2015) DOI: 10.1038/ncomms8201].
“We are currently pursuing with this research in several different directions,” Litchinitser says. “One is to integrate such a hyperlens on a facet of an optical fiber in order to use this lens for higher-resolution optical endoscopy.” The highest resolution endoscopes available today can resolve objects to around 10,000nm, the hyperlens is expected to be able to improve that to 250nm or better. This addition resolution may enable earlier detection of hard-to-find cancers such as ovarian cancer.
The lenses could also be used to improve the precision of optical nanolithography. This technique − that involves passing light through a mask to create a pattern on a polymer film − is used to build optoelectronic devices, data storage drives, sensors and other gadgets. The Slinky-like hyperlens – thanks to its high resolution – could also potentially be used for imaging single molecules.