Nkorni Katte

Metallodielectrics as metamaterials

Interference of light in a multilayer stack of metals and dielectrics, called metallo-dielectrics, can elicit unusual linear and nonlinear properties of these composite materials. This paper reports results on linear and nonlinear optical properties using various materials, especially super-resolution and nonlinear optical properties.

Broadband, tunable super-lenses in the visible region of the electromagnetic spectrum with metallodielectric stacks (MDS)

We compare two designs of metallodielectric stacks (MDS) based on Ag/GaP and Au/GaP, and calculate their superresolving bandwidths. The super-resolving bandwidth of the Ag/GaP design is (520nm-560nm), while that of Au/GaP is (630nm-660nm). We evaluate these two designs in their ability to resolve two 20nm wide apertures separated by a center-to-center distance of 80nm. We also compare two numerical techniques used to study these systems, namely the transfer matrix method (TMM) and the finite element method (FEM). The TMM is simpler than more numerically demanding FEM technique but FEM is more robust for determining super-resolution in most cases. Finally we discuss the practical limitations of our super-resolving imaging devices in resolving objects that are much smaller than the incident wavelength.

Z-scan simulations on metallodielectric stacks with nonlinear absorption

Experimental investigations reveal significant nonlinear responses from metallodielectric stacks (MDSs) with constituent metal films of silver (Ag), gold (Au) or copper (Cu). In particular, the Cu dielectric MDS exhibited large non-linear absorption. Nevertheless, there is a need to investigate these materials with more faithful numerical techniques in order to account for the underlying physical processes observed in the experiments. We apply a Finite Element Method (FEM) with radial symmetry to numerically solve for the Z-scan experiment of a MDS using the corresponding nonlinear Maxwell equations. The amplitude and the phase of the electromagnetic field at the exit interface of the MDS are used for transforming to the far-field regime.