Multipole analysis of metasurfaces composed of nanoparticles supporting electric and magnetic optical resonances

Theoretical approach to the multipole analysis of the extinction and scattering spectra of arbitrary shaped particles and the reflection and transmission spectra of metasurfaces composed from them is demonstrated and... [ view full abstract ]

Theoretical approach to the multipole analysis of the extinction and scattering spectra of arbitrary shaped particles and the reflection and transmission spectra of metasurfaces composed from them is demonstrated and discussed. The main attention is given to the first multipoles including magnetic quadrupole and electric octupole moments. The method is applied to high refractive- index nonspherical nanoparticles with resonant multipole responses in the optical range. Firstly, we show that the role of multipoles in the optical theorem (light extinction) and scattering by arbitrarily shaped nanoparticles can be different [1]. This can result in seemingly paradoxical conclusions with respect to the appearance of multipole contributions in the scattering and extinction cross sections. This fact is especially important for absorptionless nanoparticles, for which the scattering cross section can be calculated using the optical theorem, because in this case extinction is solely determined by scattering. Secondly, spectral multipole resonances of single parallelepiped-, pyramid-, and cone-like shaped silicon nanoparticles excited by linearly polarized light waves are investigated. It is demonstrated how specially configured scattering diagrams are connected with overlapping of different multipole modes resonantly excited in the nanoparticles [2]. At last, the multipole expansions of the reflection and transmission coefficients of 2D arrays of nanoparticles (metasurfaces) are developed and applied for investigation of the metasurface optical properties Suppressions of light reflection or transmission in metasurfaces composed of nonspherical silicon nanoparticles are explained as interference between waves generated by several multipole moments resonantly excited in these nanoparticles by incident light waves. The developed approach can be extremely useful for designing and optimization of metasurfaces with predetermined optical properties.

[1] A.B. Evlyukhin, T. Fischer, C. Reinhardt, and B. N. Chichkov, Phys Rev B 94, 205434 (2016).

[2] P.D. Terekhov, K. V. Baryshnikova, Y. A. Artemyev,  A. Karabchevsky, A. S. Shalin, and A. B. Evlyukhin, Phys. Rev. B 96, 035443 (2017).