Chiral metamaterials: retrieval of the effective parameters with and without substrate

TL;DR

This paper presents a robust method for retrieving effective parameters of chiral metamaterials, accounting for substrates and top layers, and analyzes substrate effects on wave propagation and homogeneity.

Contribution

It extends the parameter retrieval procedure to include substrates and top layers using transfer matrix techniques, improving accuracy for chiral metamaterials.

Findings

Substrate can cause inhomogeneity in the metamaterial slab.

Resonance elements far from the substrate are less affected by substrate presence.

The method accurately retrieves parameters for chiral metamaterials with or without substrates.

Abstract

After the prediction that strong enough optical activity may result in negative refraction and negative reflection, more and more artificial chiral metamaterials were designed and fabricated at difference frequency ranges from microwaves to optical waves. Therefore, a simple and robust method to retrieve the effective constitutive parameters for chiral metamaterials is urgently needed. Here, we analyze the wave propagation in chiral metamaterials and follow the regular retrieval procedure for ordinary metamaterials and apply it in chiral metamaterial slabs. Then based on the transfer matrix technique, the parameter retrieval is extended to treat samples with not only the substrate but also the top layers. After the parameter retrieval procedure, we take two examples to check our method and study how the substrate influences on the thin chiral metamaterials slabs. We find that the substrate may cause the homogeneous slab to be inhomogeneous, i.e. the reflections in forward and backward directions are different. However, the chiral metamaterial where the resonance element is embedded far away from the substrate is insensitive to the substrate.