Ultra-wideband Antireflection Assisted by Continuously Varying Temporal Medium

TL;DR

This paper introduces a novel ultra-wideband antireflection technique using a continuously varying temporal medium with multi-stage permittivity variation, enabling reflectionless electromagnetic wave propagation across broad frequency ranges.

Contribution

It proposes a new design of a multi-stage temporal medium with continuously varying permittivity for ultra-wideband antireflection, extending previous single-stage coatings.

Findings

Design achieves reflectionless propagation over a broad frequency band.

Numerical verification confirms effectiveness of the multi-stage temporal medium.

Application demonstrated in impedance matching between dielectric and free space.

Abstract

We demonstrate that reflectionless propagation of electromagnetic waves between two different materials can be achieved by designing an intermediate temporal medium, which can work in an ultra-wide frequency band. Such a temporal medium is designed with consideration of a multi-stage variation of the material' s permittivity in the time domain. The multi-stage temporal permittivity is formed by a cascaded quarter-wave temporal coating, which is an extension of the antireflection temporal coating by Pacheco-Pe\~na et al [[1] Optica 7, 323 (2020)]. The strategy to render ultra-wideband antireflection temporal medium is discussed analytically and verified numerically. In-depth analysis shows that the multi-stage design of the temporal media implies a continuously temporal variation of the material' s constitutive parameters, thus an ultra-wideband antireflection temporal medium is reasonably obtained. As an illustrative example for application, the proposed temporal medium is adopted to realize impedance matching between a dielectric slab and free space, which validates our new findings.