Bandwidth control of forbidden transmission gaps in compound structures with subwavelength slits

Abstract

Phase resonances in transmission compound structures with subwavelength slits produce sharp dips in the transmission response. For all equal slits, the wavelengths of these sharp transmission minima can be varied by changing the width or the length of all the slits. In this paper we show that the width of the dip, i.e., the frequency range of minimum transmittance, can be controlled by making at least one slit different from the rest within a compound unit cell. In particular, we investigate the effect that a change in the dielectric filling, or in the length of a single slit, produces in the transmission response. We also analyze the scan angle behavior of these structures by means of band diagrams and compare them with previous results for all-equal slit structures.

Light circulation and weaving in periodically patterned structures

“…[1][2][3][4][5][6][7][8] These periodic structures include transmission gratings, diffraction gratings, and more complicated one-dimensionally ͑1D͒ periodic metal-dielectric composites, all of which can be grouped under the label of plasmonic crystals. Numerous works have explained in detail the various optical and surface plasmon modes ͑SPs͒ that exist in these structures and their relative roles in producing the optical characteristics mentioned above.…”

“…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.…”

“…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.…”

“…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.…”