Triple-Band Anisotropic Perfect Absorbers Based on α-Phase MoO3 Metamaterials in Visible Frequencies.

Bin Tang,Neigang Yang,Jiangbin Su,Gui Jin,Xianglian Song

doi:10.3390/nano11082061

Bin Tang, Neigang Yang + Show 3 more

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https://doi.org/10.3390/nano11082061

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Abstract

Anisotropic materials provide a new platform for building diverse polarization-dependent optical devices. Two-dimensional α-phase molybdenum trioxides (α-MoO3), as newly emerging natural van der Waals materials, have attracted significant attention due to their unique anisotropy. In this work, we theoretically propose an anisotropic perfect metamaterial absorber in visible frequencies, the unit cell of which consists of a multi-layered α-MoO3 nanoribbon/dielectric structure stacked on a silver substrate. Additionally, the number of perfect absorption bands is closely related to the α-MoO3 nanoribbon/dielectric layers. When the proposed absorber is composed of three α-MoO3 nanoribbon/dielectric layers, electromagnetic simulations show that triple-band perfect absorption can be achieved for polarization along [100], and [001] in the direction of, α-MoO3, respectively. Moreover, the calculation results obtained by the finite-difference time-domain (FDTD) method are consistent with the effective impedance of the designed absorber. The physical mechanism of multi-band perfect absorption can be attributed to resonant grating modes and the interference effect of Fabry–Pérot cavity modes. In addition, the absorption spectra of the proposed structure, as a function of wavelength and the related geometrical parameters, have been calculated and analyzed in detail. Our proposed absorber may have potential applications in spectral imaging, photo-detectors, sensors, etc.

Highlights

Two-dimensional (2D) materials with weak van der Waals interaction between atomic layers have drawn wide attention due to their extraordinary physical, chemical, and optoelectronic properties, such as graphene [1], hexagonal boron nitride (h-BN) [2,3], transition metal dichalcogenides (TMDs) [4], and black phosphorus (BP) [5,6,7,8]
When a second α-MoO3 nanoribbon with a width w2 = 275 nm is stacked on the first α-MoO3 nanoribbon separated by a dielectric layer, as shown by the inset in Figure 2b, dual-band perfect absorption can be established for both polarization directions due to the absorption enhancement of the weak resonant absorption peak at the short wavelengths
We theoretically propose and numerically demonstrate an anisotropic perfect metamaterial absorber in visible frequencies; it consists of a multi-layered αMoO3 /dielectric structure stacked on a silver mirror

Summary

Introduction

Two-dimensional (2D) materials with weak van der Waals (vdW) interaction between atomic layers have drawn wide attention due to their extraordinary physical, chemical, and optoelectronic properties, such as graphene [1], hexagonal boron nitride (h-BN) [2,3], transition metal dichalcogenides (TMDs) [4], and black phosphorus (BP) [5,6,7,8]. By breaking the vdW bonds, monolayer 2D materials can be achieved and further transferred to the desired substrates [9,10,11]. In recent years, it has been demonstrated, both theoretically and experimentally, that plasmons can support low propagation loss and strong field confinement in a few or even monolayer 2D materials. A new type of 2D vdW semiconducting crystal, α-phase molybdenum trioxide (α-MoO3 ), has intrigued many researchers due to its highly anisotropic properties [12]. In contrast to the monoclinic and hexagonal phase of crystal MoO3 , orthorhombic MoO3 (α-phase) is Nanomaterials 2021, 11, 2061.

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