Veröffentlichungen und Präsentationen

As part of our primary research focus, we explore the phenomenon of non-radiative resonance energy transfer (RET) between a pair of dipoles positioned within a hyperbolic metamaterial (HMM). Our investigation reveals that the presence of an HMM can fundamentally alter these non-radiative dipole-dipole interactions, leading to strong coupling between the dipoles. To analyze these interactions, we model the coupling parameters using a coupled Drude oscillator system [1] (see fig.1). Our approach involves deriving analytical expressions for these parameters and validating them through precise numerical techniques. Due to the anisotropic nature of HMM, it is crucial to obtain the correct expression for the polarizability of a particle placed within such a medium. Specifically, when considering isotropic spherical particles within an anisotropic background medium, it has been demonstrated that "the internal field and dipole moment of the sphere cannot be calculated using the same shape effects as in the case of an isotropic background" [2]. This implies that the polarizability of a spherical particle in an anisotropic medium cannot be analytically determined without accounting for the depolarization effect caused by the ellipsoidal shape (see fig.2). In our study, we aim to demonstrate, through rigorous numerical simulations, that the effective medium approximation proposed by Sihvola provides a satisfactory estimation for this problem. To analyze this, we consider a gold (Au) nanosphere with a radius of 10 nm as a dipole source placed in an arbitrary anisotropic medium. By comparing the effective permittivity extracted from the simulations with analytically obtained results, we can assess the accuracy of the approximation. For our numerical simulations, we utilized COMSOL Multiphysics®. The s-parameters were obtained for the geometry of an Au particle placed in an anisotropic unit cell using the Wave Optics Module within COMSOL®. To extract the effective permittivity for a medium containing uniformly distributed particles, with a volume fraction as high as 0.27, we employed the Smith retrieval technique [3] implemented in MATLAB®. Our investigation encompasses both positive and negative anisotropic media, and we highlight the importance of considering the ellipsoidal depolarization factor by comparing the finite element method (FEM) results with the Maxwell Garnett mixing formula. This analysis will prove particularly valuable when dealing with near-field dipole-dipole interactions in an anisotropic media.