Quasi-trapped modes in metasurfaces of anisotropic MoS$_2$ nanoparticles for absorption and polarization control in the telecom optical range

TL;DR

This paper explores how anisotropic MoS$_2$ nanoparticles and their metasurfaces can support quasi-trapped modes at telecom wavelengths, enabling narrowband absorption and polarization control despite weak absorption.

Contribution

It demonstrates the existence of quasi-trapped mode resonances in MoS$_2$ metasurfaces and reveals their potential for polarization manipulation in the telecom optical range.

Findings

Quasi-trapped mode resonance at 1550 nm in MoS$_2$ metasurfaces.

Weak nanoparticle absorption leads to effective narrowband absorption.

Metasurfaces exhibit birefringence, enabling polarization transformation.

Abstract

We investigate the resonant optical response of single material-anisotropic nanoparticles (NPs) of molybdenum disulfide (MoS$_2$) and their two-dimensional arrays (metasurfaces) irradiated by plane waves of the telecomunication optical range. Nanoparticles in the form of a disk with centered and shifted hole are considered. Using the recently experimental measured the MoS$_2$ dielectric permittivity and numerical calculations with analytical multipole analysis, we show that the material-anisotropy of NPs can lead to specific nonlocal contributions in their magnetic and electric dipole response and affect the effective dipole polarizabilities. Applying a special procedure we determine the period of the MoS$_2$ metasurfaces supporting the quasi-trapped mode (QTM) resonance around the tellecom wavelength of 1550 nm. It is shown that regardless extremely weak absorption of the single nanoparticles, the excitation of the QTM leads to effective narrowband absorption in the metasurfaces. Influences of the linear polarization direction of normally incident waves on the QTM implementation and the reflection and transmission spectra are studied. It is found and demonstrated, for the first time, that a metasurface, composed of the MoS$_2$ disks with their anisotropy perpendicularto the metasurface plane, has the properties of a continuous birefringent medium. Due to these properties, normally incident and linear-polarized waves can be transformed in the transmitted and reflected waves with changed polarizations.