Fano interference in supported gold nanosandwiches with weakly coupled nanodisks

Abstract

Abstract:We studied the far-field optical response of supported goldsilica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s-and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 × 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory. In particular, the Fano asymmetry can be explained in terms of interference between the scattered waves from the decoupled nanodisks in the spectral range limited by their respective plasmon resonances. We also show that the reflectance and ellipsometry spectra can be described by a three-layer system with uniaxial effective dielectric functions.

Full Color Generation Using Silver Tandem Nanodisks

“…This has been used in surface-enhanced Raman scattering (SERS), − sensors, , high Purcell factors, negative refractive indexes, and so on. Particularly, trapezoidal sandwich structures can further enhance the magnetic field and exhibit Fano resonances. − The sharpness of the resonance can be measured by the quality factor ( Q factor, which is proportional to the resonance frequency divided by the fwhm); the Q factor of the out-of-phase mode is higher than that of the in-phase mode, as seen from Figure c. However, most of the energy radiation is caused by the latter mode, in addition, whose resonance peak is enhanced and blue-shifted when compared with the single nanodisk, ,, which is beneficial for full color generation because larger structures are easier to fabricate (see the quantitative comparison of resonances between the sandwich structure and single nanodisks in Figure S3 in the Supporting Information).…”

Spectroscopic ellipsometry for active nano- and meta-materials

“…LSPR modes peaking at distinct wavelengths are excited in the plane (ordinary effective dielectric function ε eff,o ) and perpendicularly to it (extraordinary effective dielectric function ε eff,e ) due, in this case, mainly to the shape anisotropy and specific orientation of the NPs. Uniaxial effective dielectric anisotropy has also been observed in the case of supported 2D assemblies of Au nanodisk/SiO 2 nanodisk/Au nanodisk, together with Fano features related to the interference between waves scattered by the weakly interacting Au nanodisks [142]. In the case of a stronger coupling between disks in the sandwich structures, optical magnetism has been reported [143].…”

Surface sensitivity of optical and magneto-optical and ellipsometric properties in magnetoplasmonic nanodisks

“…This phenomenon was also detected in ellipsometric studies on nude gold nanodisks arrangements. 26,27 Lastly, in Fig. 2(d), we present T-MOKE spectra obtained in Kretschmann configuration.…”