The perfect absorber

We demonstrate that films of very lossy metal or dielectric, with a thickness of only a few nanometers, can absorb almost all incident radiation when illuminated from the substrate side at the critical angle for total internal reflection. The absorption for s -polarized light approaches 100%, while...

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Bibliographic Details
Published in:Applied physics letters 2009-04, Vol.94 (17), p.171109-171109-3
Main Authors: Driessen, E. F. C., de Dood, M. J. A.
Format: Article
Language:English
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Summary:We demonstrate that films of very lossy metal or dielectric, with a thickness of only a few nanometers, can absorb almost all incident radiation when illuminated from the substrate side at the critical angle for total internal reflection. The absorption for s -polarized light approaches 100%, while the absorption for p -polarized light vanishes. We demonstrate this effect by measuring the absorption as a function of the angle of incidence at a wavelength of 775 nm in a 4.5 nm thick NbN film with a dielectric constant ϵ NbN = − 8.2 + 31.4 i . The measured absorption in this film reaches a maximum of 94%. We discuss the design of a near-unity efficiency single-photon detector for s -polarized light that has a broadband absorption coefficient of > 90 % for wavelengths from 700 to 1600 nm.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.3126062