Quasitrapped modes in metasurfaces of anisotropic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> nanoparticles for absorption and polarization control in the telecom wavelength range

Abstract

Resonant optical responses of anisotropic molybdenum disulfide (${\mathrm{MoS}}_{2}$) nanoparticles (NPs) and their two-dimensional arrays (metasurfaces) are investigated. The nanoparticles in the form of disks with holes and with ${\mathrm{MoS}}_{2}$ layers oriented perpendicular to the disk's basis (in-plane material anisotropy) are considered. Using numerical calculations with analytical multipole analysis, we show that the material anisotropy of NPs provides an additional degree of freedom for manipulation of their resonant magnetic and electric dipole responses and affect the effective dipole polarizabilities. Based on this possibility and applying a special tuning procedure, we construct the ${\mathrm{MoS}}_{2}$ metasurfaces supporting the quasitrapped mode (QTM) resonance around the telecom wavelength of 1550 nm with high quality factor and high sensitivity to the environment. It is shown that regardless of extremely weak absorption of the single nanoparticles, the excitation of the QTM leads to effective narrowband absorption in the telecom wavelength range depending on the polarization direction of normally incident waves. It is demonstrated that a metasurface, composed of the ${\mathrm{MoS}}_{2}$ disks with the in-plane material anisotropy, has the properties of a continuous birefringent medium. Due to these properties, a normally incident linearly polarized wave can be transformed into transmitted and reflected waves with changed polarizations.

Topics & Concepts