SCATTERING BY A PERIODIC ARRAY OF SUBWAVELENGTH SLITS II: SURFACE BOUND STATES, TOTAL TRANSMISSION, AND FIELD ENHANCEMENT IN HOMOGENIZATION REGIMES

摘要

This is the second part in a series of two papers that are concerned with the quantitative analysis of the electromagnetic field enhancement and anomalous diffraction by a periodic array of subwavelength slits in a perfect conducting slab. In this part, we explore the scattering problem in the homogenization regimes, where the period of the structure is much smaller than the incident wavelength. In particular, two homogenization regimes are investigated: in the first regime, the width of the slits is comparable to the period, while in the second regime, the width of the slits is much smaller than the period. By presenting rigorous asymptotic analysis, we demonstrate that a surface plasmonic effect mimicking that of plasmonic metals occurs in the first regime. In addition, for incident plane waves, we discover and justify a novel phenomenon of total transmission which occurs either at certain frequencies for all incident angles or at a special incident angle but for all frequencies. For the second regime, the nonresonant field enhancement is investigated. It is shown that the fast transition of the magnetic field in the slits induces strong electric field enhancement. Moreover, the enhancement becomes stronger when the coupling between the slits is weaker.