A new record for an optical superlens

6/25/2012 By Linda H. Conway

Object viewed through superlens, with an array of 30 nm linesMechanical Science and Engineering professor Nicholas Fang and Ph.D. student Pratik Chaturvedi, in collaboration with researchers at Hewlett-Packard Laboratory and the University of California, Davis, report that they have refined optical resolution to a new record of 30 nanometers.

Written by By Linda H. Conway

Object viewed through superlens, with an array of 30 nm lines
Object viewed through superlens, with an array of 30 nm lines
Object viewed through superlens, with an array of 30 nm lines
Mechanical Science and Engineering professor Nicholas Fang and Ph.D. student Pratik Chaturvedi, in collaboration with researchers at Hewlett-Packard Laboratory and the University of California, Davis, report that they have refined optical resolution to a new record of 30 nanometers. Their results appeared in the January issue of Applied Physics Letters.

Breaking the physical limit of diffraction of light has been the dream of microscopists for generations. In 2000, an intriguing theory of negative index of refraction was proposed, which promised for the first time to overcome this barrier without using any nonlinear optics. At the heart of this proposal was a thin film of silver, which could interact with the subwavelength modes of the object under it, leading to sharper images and finer details. The physics of such a superlens was confirmed by Fang and colleagues in 2005.

According to Fang, improving resolution of the superlens in a similar way to “Moore’s Law” is not a trivial job. This is partly because silver likes to bead up, just like water droplets forming on a windshield. Such islandized silver will blur the structures being viewed. Fang and his colleagues have found a novel way to smooth the silver layer and improve its superlens attributes. They have demonstrated that a thin layer of germanium applied before the silver grains are deposited will anchor them onto the substrate, allowing for the formation of a silver film of roughness less than 0.6 nm! These findings are an important advancement in molecular scale optical imaging and should lead to 5-10 times higher-density of optoelectronic devices.

“A smooth optical superlens,” by Pratik Chaturvedi, Wei Wu, V.J. Logeeswaran, Zhaoning Yu, M. Saif Islam, S. Y. Wang, R. Stanley Williams, and Nicholas X. Fang, Applied Physics Letters 96, 043102 (2010).


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This story was published June 25, 2012.