This review provides a perspective on the recent developments in the transmission of light through subwavelength apertures in metal films. The main focus is on the phenomenon of extraordinary optical transmission in periodic hole arrays, discovered over a decade ago. It is shown that surface electromagnetic modes play a key role in the emergence of the resonant transmission. These modes are also shown to be at the root of both the enhanced transmission and beaming of light found in single apertures surrounded by periodic corrugations. This review describes both the theoretical and experimental aspects of the subject. For clarity, the physical mechanisms operating in the different structures considered are analyzed within a common theoretical framework. Several applications based on the transmission properties of subwavelength apertures are also addressed.

http://digital.csic.es/bitstream/10261/47904/1/Light%20passing.pdf

Light passing through subwavelength apertures

Introductory Fourier transform spectroscopy

The existing theories which aim to explain the extraordinary optical transmission of a metallic film pierced by a two-dimensional subwavelength hole array [T.W. Ebbesen, H.J. Lezec, H.F. Ghaemi, T. Thio, and P.A. Wolff, Natural (London) 391, 667 (1998)] all have in common the following feature: instead of studying the two-dimensional crossed grating resulting from the hole array, they consider a one-dimensional grating with infinite slits. We show that such a simplification introduces an efficient channel for light transmission in lamellar gratings, which does not exist for hole arrays. Therefore in order to explain the relatively high transmission observed by Ebbesen et al., it is necessary to take into account the existence of the holes in the array. In this paper we develop a two-dimensional analysis of the experiment performed by Ebbesen et al. No simplification is introduced. This allows us to obtain theoretically the long-wavelength peak reported by Ebbesen et al. with the same grating thickness as the one used by these authors. We also review and study in detail the various contributions devoted to this very surprising effect.

/pdf/theory-of-light-transmission-through-subwavelength-periodic-2kaxlsw2or.pdf

Theory of light transmission through subwavelength periodic hole arrays

In this paper we show how the optical properties of a metallic film can be tailored by one-dimensional periodically nanostructuring it which, in turn modifies the surface plasmon properties. The interaction of light with the surface plasmons can be used for two apparently opposite effects: trapping incident radiation into small volumes (in reflection gratings) and transmitting light very efficiently (in transmission gratings). A physical picture of the mechanisms involved, as well as dependences of the transmission and reflection spectra on wavelength, absorption and geometrical parameters of the grating, are provided.

Transmission and focusing of light in one-dimensional periodically nanostructured metals

In this Letter, we study the scattering of light by a single subwavelength slit in a metal screen In contrast with previous theoretical works, we provide a microscopic description of the scattering process by emphasizing the generation of surface plasmons at the slit apertures The analysis is supported by a rigorous formalism based on a normal-mode-decomposition technique and by a semianalytical model that provides accurate formulas for the plasmonic generation strengths The generation is shown to be fairly efficient for metals with a low conductivity, such as gold in the visible regime Verification of the theory is also shown by comparison with recent experimental data [H F Schouten, Phys Rev Lett 94, 053901 (2005)]

Theory of Surface Plasmon Generation at Nanoslit Apertures

We present a semi-analytical model that quantitatively predicts the transmission, the absorption and the resonance locations of one-dimensional lamellar metallic gratings with subwavelength slit apertures. The model relies on the fact that subwavelength apertures perforated in metallic films behave like monomode waveguides and provide Airy-like formulae for the transmission and reflection coefficients. Limitations are outlined for too shallow grating depths.

https://iopscience.iop.org/article/10.1088/1464-4258/2/1/309/pdf

One-mode model and Airy-like formulae for one-dimensional metallic gratings

A photolithographic process has been used to form cross-shaped patterns in 3-μm-thick nickel foils. Patterns with cross arm dimensions in the 10–20-μm range, and with periodicities in the 16–26-μm range, yield self-resonant bandpass filters for wavelengths in the 20–25-μm region. Transmittances as high as 80% were achieved with center wavelength-to-bandwidth ratios (λR/Δλ) of ∼5. We present a simple empirical formula that relates the wavelength of peak transmittance, or resonant frequency, with cross dimensions and periodicity.

Cross-shaped bandpass filters for the near- and mid-infrared wavelength regions.

Interferometers of the Michelson or Mach–Zehnder type are designed as array interferometers. The number of array channels is equal to the number of points needed for an interferogram for Fourier transformation. Similarly one may use an array of step gratings with each grating having a different step height and producing one point of the interferogram. These interferometers, which do not have moving parts, use all the incident light, and the interferogram is instantly produced for real-time spectroscopy.

Wave-front-dividing array interferometers without moving parts for real-time spectroscopy from the IR to the UV

Thin and thick cross shaped metal grids

Geometrical Optics * Interference * Diffraction * Coherence * Maxwell's Theory * Maxwell II. Modes and Mode Propagation * Blackbody Radiation, Atomic Emission and Lasers * Optical Constants * Fourier Transformation and FT-Spectroscopy * Imaging Using Wave Theory * Aberration.

K. D. Möller

Papers

One-mode model and Airy-like formulae for one-dimensional metallic gratings

Cross-shaped bandpass filters for the near- and mid-infrared wavelength regions.

Wave-front-dividing array interferometers without moving parts for real-time spectroscopy from the IR to the UV

Thin and thick cross shaped metal grids

Optics: Learning by Computing, with Examples Using MathCad