Transmission Resonances of Metallic Compound Gratings with Subwavelength Slits

Abstract

Transmission metallic gratings with subwavelength slits are known to produce enhanced transmitted intensity for certain resonant wavelengths. One of the mechanisms that produce these resonances is the excitation of waveguide modes inside the slits. We show that by adding slits to the period, the transmission maxima are widened and, simultaneously, this generates phase resonances that appear as sharp dips in the transmission response. These resonances are characterized by a significant enhancement of the interior field.

Analytical model for the transmission of electromagnetic waves through arrays of slits in perfect conductors and lossy metal screens

“…This problem is easily amenable to the mode matching solution 31 (a modal approach applied to slit systems can also be found, for instance, in Ref. 10). In most of the cases treated in the literature, the wavelength of the impinging field is taken to be longer than d in order to enforce a single transmitted and reflected spot (nondiffracting operation regime).…”

“…6 Moreover, complex spectra with deep and narrowband notches (phase resonances) in the middle of the transmission bands have been reported for compound transmission gratings. 10,11 In addition to periodic arrays of slits, the study of the transmission through a single slit aperture made in a flat metal screen has also been a subject of interest. [12][13][14] From the analysis of this simple structure it is possible to qualitatively understand some important details of the behavior of more complex periodic geometries.…”

Light circulation and weaving in periodically patterned structures

“…Most of the research on phase resonances has been done on 1D periodic transmission and diffraction gratings with light polarized with the magnetic field oriented parallel to the metal wires ͑i.e., p-polarized light͒. [6][7][8][13][14][15] Phase resonances for p-polarized incident light arise in 1D periodic structures that have multiple grooves per period ͑i.e., compound gratings͒. Many different types of compound grating structures support phase resonances including, but not limited to, compound gratings with the grooves within each period of the grating being identically composed and oriented except that not all the grooves are surrounded by the same identical configuration of neighboring grooves, 6 and, as described in this work, compound gratings with the grooves in each period that differ with respect to composition or dimensions.…”

“…In these types of structures, p-polarized VSP-CMs in neighboring grooves couple to each other and produce field profiles of equal magnitude but with a radians phase difference; such modes have come to be called modes or resonances. [6][7][8]14,15 In this work, two tasks are performed: the first is to determine if a different type of cavity mode ͑CM͒ that is not produced by Fabry-Pérot resonances of SPs on the vertical walls of the grooves can produce resonances, and the second is to study and describe the phenomenon of light circulation and light weaving that occurs when modes are excited. This different type of CM is a simple wave guide cavity mode ͑denoted as WG-CM͒, whose energy is determined by both the height and width of the groove and the dielectric constant of the material filling the groove.…”

“…3͑b͔͒ that are similar to the ones studied in past works on p-polarized resonances. [6][7][8]14,15 The reader is referred to these works [6][7][8]14,15 for the description of the numerous properties of p-polarized resonances. The rest of this work involves an aspect heretofore not discussed or analyzed in detail, namely, light circulation and light weaving properties of s-polarized and p-polarized resonances.…”