Description of the modes governing the optical transmission through metal gratings

Abstract

An analytical model based on a modal expansion method is developed to investigate the optical transmission through metal gratings. This model gives analytical expressions for the transmission as well as for the dispersion relations of the modes responsible for high transmission. These expressions are accurate even for real metals used in the visible - near-infrared wavelength range, where surface plasmon polaritons (SPP's) are excited. The dispersion relations allow the nature of the modes to be assessed. We find that the transmission modes are hybrid between Fabry-Pérot like modes and SPP's. It is also shown that it is important to consider different refractive indices above and below the gratings in order to determine the nature of the hybrid modes. These findings are important as they clarify the nature of the modes responsible for high transmission. It can also be useful as a design tool for metal gratings for various applications.

High-frequency electromagnetic non-destructive evaluation for high spatial resolution, using metamaterials

“…This study presents the possibility of improving the spatial resolution of the electromagnetic non-destructive control of conductive strip grating in the frequency range of hundreds of megahertz, using evanescent waves (Born & Wolf 2002) that may appear in slits having widths smaller than the wavelength of the incident electromagnetic waves in vacuum (Guillaumee et al 2011).…”

Non-universal behavior of leaky surface waves in a one dimensional asymmetric plasmonic grating

“…This coupling creates two degenerate SPP modes propagating all at once on both the interfaces. 21 However, this is not the case here as we can see from Fig. 3 that the surface wave mode exists only on Au/ analyte side for the given h values.…”

“…11,12,14,20,21 Narrow slits support TM waveguide mode propagating inside the slits in contrast to cylindrical apertures. 11,12,[19][20][21] A metal grating surrounded by a dielectric medium supports three resonant states (RS), which can be identified in a reflection spectrum. These RS are (i) waveguide formed within the metal strips (broad band resonance, metal-insulator-metal structure), 10 similar to FP cavity mode, (ii) propagating SPPs, and (iii) involve the whole grating periodicity depending on the availability of FP cavity modes.…”

“…3,4,13,18 Among the various types, grating structure can be compact and robust, which are desirable characteristics for integration into other devices 6 apart from the tunability of the spectral response through geometrical parameters. [10][11][12][19][20][21] Especially, 1D grating can support waveguide, propagating SPPs and/or surface wave modes. 10,14,19 The grating parameters can be tuned to maximize any of the above modes, which may be featured in the optical properties.…”

An effective cavity resonance model for enhanced optical transmission through a periodic array of subwavelength square apertures

“…There have been some successful studies of cavity-type resonances for one-dimensional gratings, under limited geometrical conditions. [23][24][25][26] This approach has successfully been extended to two-dimensional arrays of cylindrical apertures in metallic films, 27 and will be further applied to subwavelength square aperture arrays in this paper.…”