Negative refractive index response of weakly and strongly coupled optical metamaterials

TL;DR

This paper investigates how the optical properties of fishnet metamaterials change with layer separation, revealing differences between weak and strong coupling effects on negative refractive index and figure of merit.

Contribution

It provides a detailed analysis of the retrieved optical parameters of coupled fishnet metamaterials, highlighting the impact of layer separation on their electromagnetic response.

Findings

Weak coupling results are similar to single-layer structures.

Strong coupling significantly alters the optical parameters.

High figure of merit in strong coupling is due to the real part of n moving away from resonance.

Abstract

e present a detailed study of the retrieved optical parameters, electrical permittivity, magnetic permeability and refractive index, of the coupled fishnet metamaterial structures as a function of the separation between layers. For the weak coupling case, the retrieved parameters are very close to the one-functional-layer results and converge relatively fast. For the strong coupling case, the retrieved parameters are completely different than the one unit fishnet results. We also demonstrate that the high value of the figure of merit (FOM=|Re(n)/Im(n)|) for the strongly coupled structures is due to the fact that the real part of the negative $n$ moves away from the maximum of the imaginary part of n (close to the resonance), where the losses are high.