Total absorption of electromagnetic waves in ultimately thin layers

TL;DR

This paper investigates the design of ultra-thin, single-layer electromagnetic absorbers using bi-anisotropic particles, enabling total absorption from one side and transparency from the other, with potential applications in isolators.

Contribution

It identifies conditions for bi-anisotropic particles to achieve perfect absorption and explores design possibilities across all four fundamental classes, including asymmetric structures with unique reflection properties.

Findings

Single-layer grids can be designed for total absorption from one side and transparency from the other.

Asymmetric structures can exhibit twist polarization reflection.

Practical approaches for realizing these particles are discussed.

Abstract

We consider single-layer arrays of electrically small lossy bi-anisotropic particles that completely absorb electromagnetic waves at normal incidence. Required conditions for electromagnetic properties of bi-anisotropic particles have been identified in the most general case of uniaxial reciprocal and nonreciprocal particles. We consider the design possibilities offered by the particles of all four fundamental classes of bianisotropic inclusions: reciprocal chiral and omega particles and nonreciprocal Tellegen and moving particles. We also study the reflection/transmission properties of asymmetric structures with different properties when illuminated from the opposite sides of the sheet. It has been found that it is possible to realize single-layer grids which exhibit the total absorption property when illuminated from one side but are totally transparent when illuminated from the other side (an ultimately thin isolator). Other possible properties are co-polarized or twist polarized reflection from the side opposite to the absorbing one. Finally, we discuss possible approaches to practical realization of particles with the properties required for single-layer perfect absorbers and other proposed devices.