Light scattering of rectangular slot antennas: parallel magnetic vector vs perpendicular electric vector

Abstract

We study light scattering off rectangular slot nano antennas on a metal film varying incident polarization and incident angle, to examine which field vector of light is more important: electric vector perpendicular to, versus magnetic vector parallel to the long axis of the rectangle. While vector Babinet’s principle would prefer magnetic field along the long axis for optimizing slot antenna function, convention and intuition most often refer to the electric field perpendicular to it. Here, we demonstrate experimentally that in accordance with vector Babinet’s principle, the incident magnetic vector parallel to the long axis is the dominant component, with the perpendicular incident electric field making a small contribution of the factor of 1/|ε|, the reciprocal of the absolute value of the dielectric constant of the metal, owing to the non-perfectness of metals at optical frequencies.

Cathodoluminescence as a probe of the optical properties of resonant apertures in a metallic film

“…Subsequently, Bouwkamp extended Bethe's result adding further terms in a series expansion [ 2 ] and Roberts [ 3 ] developed a modal method to accommodate apertures in finite thickness films. A broad range of other apertures have been investigated including rectangular slots [ 4 – 5 ] and circular apertures [ 3 , 6 ] as well as more complex shapes such as cross-shaped [ 7 – 9 ], and coaxial apertures [ 10 – 11 ]. Interest in sub-wavelength metallic apertures increased significantly after Ebbesen et al reported optical transmission, enhanced relative to an equivalent hole–area fraction of randomly arranged apertures, through periodic arrangements of holes in a silver film [ 12 ].…”

“…This enhancement is strongly associated with the ordered arrangement of the apertures. Theoretical and experimental research into isolated rectangular slots [ 4 – 5 ] and coaxial apertures [ 10 – 11 ], however, has shown that these cavities exhibit distinct localized resonances that have a strong dependence on the geometry of the holes including the thickness of the metal film [ 13 ]. Other than the excitations discussed above, sharp Fano resonances arising from the interference of two modes [ 14 ] have promising applications in sensing, switching and lasing.…”

Resonant Transmission Through a Single Subwavelength Slit for Varied Metallic Permittivities and Its Modal Orthogonality

“…Electromagnetic resonant transmission through one-or two-dimensional slits has been discussed for several decades, and research on extraordinary optical transmission [1][2][3][4] has led to significant physical and practical achievements. In earlier research [5,6], perforated metallic plates are generally assumed to be perfect electric conductors (PECs), and corresponding resonant transmission characteristics through PEC slits were investigated.…”

Magnetic Nature of Light Transmission through a 5-nm Gap

“…The most prominent examples of the principle are slot antennas 7 , 8 . Slot antennas, which are complementary to rod antenna radiating as electric dipoles, act as magnetic dipoles and become an important building block in optical magnetism.…”

“…In this work, we studied the light transmission through a single slit of 5-nm width and 150-nm thickness and found that the transmission through a high aspect ratio nanogap is dominated by the magnetic field, as slot antennas of moderate aspect ratios 2 , 7 , 8 . A slit structure can be regarded as a slot antenna of an extreme length, having a simple 2-dimensional geometry enabling easier analysis.…”