Crucial role of metal surface in enhanced transmission through subwavelength apertures

Abstract

In order to understand the details of the extraordinary enhancement of the optical transmission through subwavelength holes in metal films, we have fabricated perforated free-standing metal films where the nature of the bulk and surfaces can be controlled independently. We find that the transmission enhancement depends only on the dielectric properties of the metal within a skin depth of the two in-plane surfaces and not on those of the film core, nor on the metal constituting the hole walls. This provides direct and conclusive evidence that the phenomenon is mediated by surface plasmons.

Tuning Fabry-Perot resonances via diffraction evanescent waves

“…It is a direct manifestation of the constructive or destructive wave interference over a certain path length and can lead to multiple transmission peaks as a function of frequency for wave transmission through impedance-mismatched layers. There is a renewed interest in electromagnetic FP resonances, especially their relevance to the recently observed transmission enhancement through subwavelength openings in normally opaque objects, [1][2][3][4][5][6][7][8] as well as to the ensuing debate on the relative contributions of surface wave versus diffraction in such phenomena. [9][10][11][12][13][14][15][16][17][18][19] It has been shown that light transmission through hole arrays in perfect-conductor thin films, where there can be no true surface waves, may be attributed ͑via Babinet's principle͒ to the reflection by the complementary structure consisting of planar arrays of perfect-conductor disks.…”

Plasmonic structures with extraordinary transmission and highly directional beaming properties

“…As defined in the standard diffraction theory by Bethe [1] in 1944, a circular aperture with a subwavelength diameter transmits EM waves rather poorly ϳ(d/ ), 4 in which exiting EM waves are fully diffracted in all directions. These two disadvantages of low transmission and diffraction are the main problems in controlling of light, especially for subwavelength scales.…”

“…A resonant interaction leads to an enhanced transmission at wavelengths determined by the corrugation period [3][4][5][6][7][8]. It is also possible to confine the transmitted beam with the use of the periodically corrugated metal surface with subwavelength apertures [9 -12].…”

“…In contrast with metamaterials relying on the resonance of geometrical structures such as arrays of metal wires and split ring resonators, the CRLH-TL is an inherently wideband structure well suited to phase shifting applications. In this context, it has recently attracted significant interest, and different one-dimensional devices based on this principle have been demonstrated, such as leaky-wave antennas [3] and phase shifters used for instance in series feed network of antenna arrays [1,4] or compact dual-band couplers [2].…”

“…From a more general perspective, it is believed that most demonstrated CRLH-TL-based microwave devices [1][2][3][4] could benefit from MEMS technology and especially from the state-of-the-art tunability capability it offers.…”