Limits of Babinet’s principle for solid and hollow plasmonic antennas

Abstract

We present an experimental and theoretical study of Babinet’s principle of complementarity in plasmonics. We have used spatially-resolved electron energy loss spectroscopy and cathodoluminescence to investigate electromagnetic response of elementary plasmonic antenna: gold discs and complementary disc-shaped apertures in a gold layer. We have also calculated their response to the plane wave illumination. While the qualitative validity of Babinet’s principle has been confirmed, quantitative differences have been found related to the energy and quality factor of the resonances and the magnitude of related near fields. In particular, apertures were found to exhibit stronger interaction with the electron beam than solid antennas, which makes them a remarkable alternative of the usual plasmonic-antennas design. We also examine the possibility of magnetic near field imaging based on the Babinet’s principle.

Plasmonic Antennas with Electric, Magnetic, and Electromagnetic Hot Spots Based on Babinet’s Principle

“…However, the distribution of the delocalized field (e.g., electric for bowtie and magnetic for diabolo) differs. In general, magnetic fields are weaker than electric fields in agreement with previous findings [42,46].…”

“…The peak energies of the scattering efficiency in the complementary PA (i.e., bowtie and inverted bowtie, diabolo and inverted diabolo) of the same size differ by less than 11%. The difference is less pronounced for large antennas, in line with the requirements of Babinet's principle: perfectly thin and opaque metal [42]. For the bowtie geometry, the scattering peaks of inverted PAs are less intense and redshifted with respect to direct PAs (as is the case also for disc-shaped antennas [42]), while opposite is true for the diabolo geometry.…”

“…The difference is less pronounced for large antennas, in line with the requirements of Babinet's principle: perfectly thin and opaque metal [42]. For the bowtie geometry, the scattering peaks of inverted PAs are less intense and redshifted with respect to direct PAs (as is the case also for disc-shaped antennas [42]), while opposite is true for the diabolo geometry. Not surprisingly, the peak energies of the scattering cross section for the diabolo PAs are considerably smaller than that for the bowtie PAs of the same wing length v. In other words, for the same energy, the diabolo PAs are smaller by a factor of more than 2 than the bowtie PAs.…”

“…Consequently, when the direct antenna features an electric hot spot, the inverted antenna features a magnetic hot spot and vice versa. The validity of Babinet's principle for the plasmonic antennas has been experimentally verified [39,40], although some quantitative limitations have been found in particular in the visible spectral range [41,42].…”

Spectral Engineering Via Complex Patterns of Circular Nano-Object Miniarrays: II. Concave Patterns Tunable by Integrated Lithography Realized by Circularly Polarized Light

“…Babinet inverted plasmonic metasurfaces were used to produce spin-selective second-harmonic vortex beams [35]. It was shown that disks and cylindrical apertures differ quantitatively with respect to the Babinet complementarity because the apertures produce higher magnetic-to-electric-field ratios and better charge-transfer properties [36]. Miniarrays of elliptical nanoholes that are not superimposable on their mirror image exhibit chiroptical effects, i.e., selective reflection of a single spin state while preserving its handedness [37].…”