Sub-wavelength diffraction-free imaging with low-loss metal-dielectric multilayers

TL;DR

This paper demonstrates numerically that metal-dielectric multilayers can enable diffraction-free propagation of sub-wavelength optical beams with low loss, using a design based on effective medium theory and verified by FDTD simulations.

Contribution

It introduces a novel low-loss, diffraction-free optical material based on silver and high-index dielectrics, characterized by effective medium theory and transfer matrix methods.

Findings

Diffraction-free propagation verified by FWHM analysis.

Small reflections and attenuation observed.

Suitable for arbitrarily shaped optical planar elements.

Abstract

We demonstrate numerically the diffraction-free propagation of sub-wavelength sized optical beams through simple elements built of metal-dielectric multilayers. The proposed metamaterial consists of silver and a high refractive index dielectric, and is designed using the effective medium theory as strongly anisotropic and impedance matched to air. Further it is characterised with the transfer matrix method, and investigated with FDTD. The diffraction-free behaviour is verified by the analysis of FWHM of PSF in the function of the number of periods. Small reflections, small attenuation, and reduced Fabry Perot resonances make it a flexible diffraction-free material for arbitrarily shaped optical planar elements with sizes of the order of one wavelength.