Yanwen Wu, Chengdong Zhang, Yang Zhao, Jisun Kim, Matt Zhang, Xing-Xiang Liu, Greg K. Pribi, Andrea Alù, Chih-Kang Shih, Xiaoqin Li
Plasmonics offers an enticing platform for manipulating light at the subwavelength scale. But so far metal loss represented serious challenge impeding the progress and broad impact of this field of research towards practical technology. Silver (Ag) is currently the preferred material for plasmonic applications because it has the lowest loss at optical frequencies among all metals. However, large discrepancies exist among widely quoted values of optical loss in Ag, due to variations in sample preparation and measurement. A natural question arises: what are the intrinsic optical constants of silver? In this work, we report the measurement of new optical constants on atomically smooth epitaxial silver films. Careful spectroscopic ellipsometry measurements and analyses show a lower optical loss (up to a factor ~ 2) in the epitaxial films at visible frequencies compared to the lowest previously reported values. Using these new optical constants, we predict that epitaxial silver may provide a new material platform for significantly improved plasmonic devices, including metasurfaces, surface enhanced Raman scattering, and nanolasers.
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http://arxiv.org/abs/1306.5360
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