Ultrasmooth Silver Surfaces Promise Invisibility Cloaks and Ultrahigh-resolution Lenses

Surface plasmon resonance—the coherent excitation of free electrons on the surface of metals—is crucial to the operation of extremely small photonic devices, which have applications ranging from optoelectronic circuits and molecular sensors to the ‘metamaterials’ that could one day be used to make invisibility cloaks.

To minimize scattering losses in metals, the metal surfaces need to be extremely smooth. Jinghua Teng at the A*STAR Institute of Materials Research and Engineering and co-workers have now developed an effective method to fabricate smooth thin films of silver with enhanced plasmonic properties1.

As surface plasmon resonances are confined to surfaces, it is possible to miniaturize plasmonic devices to sizes that go far below the wavelength of light used to excite the electrons, but at such dimenions, losses become an obstacle to performance. “One of the grand challenges for plasmonics and metamaterials application is the minimization of loss,” says Teng. “Applications of plasmonics in real-world devices will to a great extent depend on our ability to fabricate structures with low optical losses.”

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