Abstract
In this work, the two-dimensional profile of the light transmission through a prism-like metallic film sample of Au was measured at a wavelength of 632.8 nm in the visible intraband transition region to verify that, beyond the possible mechanisms of overcoming the diffraction limit, a strongly nonuniform optical absorption path length of the light traveling in the metal could induce a lensing effect, thereby narrowing the image of an object. A set of prism-like Au samples with different angles was prepared and experimentally investigated. Due to the nonuniform paths of the light traveling in the Au samples, lens-effect-like phenomena were clearly observed that reduced the imaged size of the beam spot with decreasing light intensity. The experimental measurements presented in the work may provide new insight to better understand the light propagation behavior at a metal/dielectric interface.
Highlights
According to the conventional Snell’s law established by Snell and Descartes in the first half of the 17th century[1], light that is incident at an angle θ1 will be refracted in the positive direction at an angle θ2 at an interface consisting of materials 1 and 2 with refractive indices n1 and n2, respectively, such that n1sinθ1 = n2sinθ[2]
It has been shown that for a parallel light beam with a typical mercury (Hg) wavelength λ of 365 nm in the near-ultraviolet intraband transition region of Ag incident on a sample containing a nanostructure with dimensions much smaller than the wavelength, an image of the nanostructure can be focused by a planar Ag lens attached to the sample, resulting in a reduced light intensity and a considerably narrowed image of the nanostructure compared with that obtained without using a planar Ag lens[9,10]
Due to possible side effects, such as beam scattering and diffraction induced by the nanostructure, the light beams transmitted through the planar Ag lens will not be parallel, implying that the path z of a light beam traveling through the Ag lens will depend on the individual light paths, which are nonuniformly distributed in the lens
Summary
According to the conventional Snell’s law established by Snell and Descartes in the first half of the 17th century[1], light that is incident at an angle θ1 will be refracted in the positive direction at an angle θ2 at an interface consisting of materials 1 and 2 with refractive indices n1 and n2, respectively, such that n1sinθ1 = n2sinθ[2]. This law is valid for optically transparent dielectric materials in a broad photon energy range and under almost all conditions. The experimental measurements reported in this work may provide new insight to better understand the light propagation behavior occurring at a metal/dielectric interface
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