Microwave Transmission of a Compound Metal Grating

Abstract

An array of subwavelength slits in a metallic substrate supports a series of Fabry-Perot-like resonances, where each harmonic results in a transmission peak. Addition of extra slits per period yields a compound grating with a structure factor associated with the basis. In this study each repeat period is comprised of a central slit flanked by a pair of narrower slits. It supports three resonances for every Fabry-Perot-like solution. New and useful insight into this phenomenon is gained by describing each of the modes in terms of the band structure of diffractively coupled surface waves.

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.…”

“…Many aspects of phase resonances in 1D gratings for p-polarized incident light were studied by Hibbins et al, 13 in which they studied the phase difference between the electric fields in neighboring grooves. They used finite-element modeling to numerically model all the optical, SP, and modes and used a band-folding technique to provide a physical justification for the shape of the bands and the interactions between the modes.…”

“…By analyzing the details of these modes, they show that they are composed of coupled VSPCMs in neighboring grooves. 13 One issue that was not within the scope of Ref. 13 was whether such resonances exist for s-polarized light.…”

“…13 One issue that was not within the scope of Ref. 13 was whether such resonances exist for s-polarized light. For s-polarized light, there is no component of the electric field that is normal to any metal/dielectric interface, and hence, SPs and VSP-CMs cannot be excited.…”

“…13, or one can change the groove height or dielectric constant of the material filling the grooves, 7 as is done in this work. This is because the p-polarized resonances are composed of interacting p-polarized VSP-CMs, whose energies have small dependences on the widths of the grooves ͑relative to the energies of s-polarized WG-CMs͒; an example of these dependencies of CM energies on groove widths is shown in Fig.…”