Circulation and concentration of s- and p-polarized light in two-dimensional compound gratings

摘要

Two-dimensional compound gratings (2dCGs) are capable of π-radian difference phase resonances (PRs). Circulation and concentration of s- and p-polarized light incident on 2dCG metal structures are studied. In prior work, it has been shown that PRs can occur for s- and p-polarized light in one-dimensional compound gratings (1dCGs). In contrast, the structure studied in this work has two asymmetric holes in the unit cell, each filled with a material of high dielectric permittivity (?=10.84) and can support PRs in 2dCGs in the spectral range from 8 to 12 GHz. Due to asymmetry within the system, the two apertures react differently to the incident light and support polarization dependent PRs that are resonantly excited within the apertures. It is shown that PRs occur in 2dCGs with similar characteristics of 1dCGs, such as having narrow bandwidths, high Q values, and high concentrations of electromagnetic fields. However, PRs occurring on 2dCGs have a benefit of manipulating in more numerous ways as compared with 1dCGs. As the incident light excites waveguide cavity modes, the fields in the corresponding neighboring cavities in 2dCGs are coupled by circulations of counter-propagating modes and the π-radian phase differences produce a concentration and narrowband inversion of the transmissivity/opacity. The dependencies of bandwidth and wavelength of the PRs on structural and material properties, polarization of the incident beam, as well as the Poynting vector fields are described. Applications include narrow bandwidth optical filters, light trapping, antireflection coatings, waveguiding structures, and electromagnetically induced transparency.