Bragg transmittance ofs-polarized waves through finite-thickness photonic crystals with a periodically corrugated interface

Abstract

Finite-thickness photonic crystals (PC's) with periodically corrugated interfaces are suggested to realize some unusual features in the behavior of transmitted Bragg beams (diffraction orders). The scattering of s -polarized plane waves by such structures is studied. It follows from the numerical results that rather thin corrugated PC's borrow their basic properties from both conventional PC's and gratings, leading to some new effects. In particular, a shift of the actual cutoff frequencies towards larger values than those of the Rayleigh cutoff frequencies can be obtained due to the ordinary opaque range in transmission, within which all propagative orders vanish. This effect can even be enhanced due to the nonordinary behavior arising at the edges of the ordinary opaque range, which manifests itself in that some but not all propagative orders in transmission are suppressed. Hence the opaque ranges for individual orders are wider than the corresponding ordinary range. Besides, frequency ranges exist which are not connected with the edge of the ordinary opaque range, where a similar nonordinary effect does appear. As a result, each propagative order in transmission generally has its own set of opaque ranges. Only a single order can be contributive while several others are formally propagative, too. The corrugations have to be located at the upper interface in order to realize these nonordinary effects. Moving the corrugation from the upper to the lower interface leads to a disappearance of the observed effects, so that their nature cannot be explained exclusively in terms of matching the wave vectors of the diffraction orders and the Floquet-Bloch waves. The conventional sequence of cutoffs for different diffraction orders with respect to each other can be changed for certain structures if the rods of a PC are made of Drude metal. Hence, transmission regimes can be realized which are beyond the classical theory of gratings. Several effects arising when varying the angle of incidence are demonstrated and briefly discussed. The detected effects can be used for controlling the number of actually contributive beams and for obtaining alternating ranges of single-beam and multibeam operation, which should lead to extending the potentials of optical and microwave technologies based on the use of single-beam and multibeam regimes.

Unidirectional transmission in non-symmetric gratings containing metallic layers

“…the isofrequency dispersion contours are localized at a periphery point of the First Brillouin Zone [5]. In this case, one-way higher-order transmission and even unidirectional transmission can be obtained, provided that the front-side and back-side interfaces have different periods [6]. One-way transmission might also appear in metallic slabs with the branched multiple slits [7] and gratings made of a zero-permittivity material [8], so that an anisotropy-like dispersion is not needed.…”

Wideband unidirectional transmission with tunable sign-switchable refraction and deflection in nonsymmetric structures

“…Because of reciprocity, additional transmission channels should be opened for one of the two opposite illumination directions, which can be connected with higher diffraction orders [1][2][3][4][5][6][7][8] or polarization conversion [9][10][11] and can exploit benefits of inclining interfaces. [12][13][14] In the first case, asymmetry in transmission is inspired, in fact, by asymmetric diffractions at the opposite interfaces of a grating-like structure.…”

“…Furthermore, it can be a wideband regime at least if a material or a periodic structure with specific dispersion is utilized to create a nonsymmetric structure. 4,5 Results related to various regimes of the diffraction-inspired asymmetric transmission have recently been reported for photonic crystal gratings, 2,3,5,6 gratings made of ultralow-index materials, 4 and stacked subwavelength hole arrays (SHAs) with one-side corrugations. 15 Moreover, asymmetric transmission can be achieved by using a single nonsymmetric metallic grating with slits, 1,16 or two different metallic gratings with slits and an air gap in between.…”

Basics of the photonic crystal gratings

“…In the gratings made of Drude metals or composites, the actual thresholds have different locations as compared to the classical case that is associated with dielectric gratings (Serebryannikov & Ozbay, 2009). In the PCGs with either dielectric or metallic rods, the actual thresholds can also be affected by location of the stop bands of the PC (Serebryannikov, 2006;Serebryannikov, 2009). …”

“…In the mid 2000's, PCs with the corrugated interfaces have been proposed to redirect the reflected waves to the side directions (Collardey, 2005), obtain unusual order of the cutoff wavelengths for higher diffraction orders (Serebryannikov, 2006), and realize a new mechanism of negative refraction due to the umklapp refracted beams (Lu, 2007). Later, PCs with the corrugated interfaces have been called photonic crystal gratings (PCGs) (Serebryannikov, 2009).…”