Comprehensive microscopic model of the extraordinary optical transmission
Spotlight summary: Optical science has been greatly influenced by experiments measuring the behavior of light transmitted through apertures. Famous examples include Grimaldi’s description of diffraction by a circular aperture and Young’s double-slit experiment (the classic demonstration of the wave nature of light). Given the long and detailed study of optical transmission through apertures, it was somewhat surprising when, in 1997, Ebbesen and coworkers demonstrated an unexplained level of transmission through a metallic screen perforated with an array of subwavelength holes. Bethe’s optical theory for subwavelength holes predicted transmission proportional to the fourth power of the ratio between the hole radius and the wavelength, but observations showed transmission orders of magnitude greater than this. For several years the origin of this extraordinary optical transmission (EOT) was vigorously debated. The materials and geometries exhibiting EOT, coupled with the polarization dependence of the phenomenon, strongly suggested contributions from surface plasmons (SPs), which can act to “funnel” light into the subwavelength holes, thus increasing transmission. The surface plasmon description was not entirely satisfactory however—SP-based predictions did not appear to be accurate in all circumstances, especially for longer infrared wavelengths. Brute force solutions to Maxwell’s equations could accurately predict EOT, however such methods are largely unintuitive, hindering the design process required to incorporate EOT into new technologies. Liu and Lalanne have, in a series of papers that include the current article, developed an intuitive but accurate description of EOT. By augmenting an SP component with a second component (dubbed a quasi-cylindrical wave), EOT behavior is accurately explained over an extensive range of wavelengths. The new framework can handle a wide variety of surface aperture patterns and is less computationally intensive than realizing a full numerical solution of Maxwell’s equations. Critically, Liu and Lalanne’s method provides intuitive insight and a degree of modularity to EOT calculations, thus paving the way for deliberate system design and, ultimately, engineering applications. Given the current drive toward miniaturized SP-based optical technologies, this is a particularly timely and relevant contribution.
Technical Division: Optical Design and Instrumentation
ToC Category: Diffraction and Gratings
|OCIS Codes:||(050.1950) Diffraction and gratings : Diffraction gratings|
|(240.6680) Optics at surfaces : Surface plasmons|
|(050.6624) Diffraction and gratings : Subwavelength structures|
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