Wide-angle Perfect Absorption Research Articles

Design and analysis of a wideband and wide angle 3D metamaterial absorber

In this paper, we proposed a three-dimensional (3D) metamaterial absorber joint by lightweight 3D grid structure and traditional magnetic materials, which can achieve wideband and wide-angle perfect absorption at 5–20 GHz. By simulation, the broadband absorption remained almost 90% from 0° to 80° for TM wave. The surface current and power loss distributions were investigated to interpret the physical mechanism of wideband and wide-angle absorption. The broadband and wide-angle absorption were derived from magnetic and electric resonances between the top resistive film, background plane and magnetic loss of magnetic materials. The results proved that different layers of the proposed absorber play different loss roles, and finally contributed to the wideband and wide-angle absorption. The polarization insensitive stability of the proposed absorber was also demonstrated at different polarized angles. The present study provided a new design to achieve a polarization insensitive, wideband and wide-angle absorber. Moreover, the structure absorber has potential applications in other fields, including the solar cell, imaging and detection etc.

Optimal angular stability of reflectionless metasurface absorbers

In this work, we investigate the possibilities of reaching wide-angle perfect absorption with Huygens' metasurfaces possessing both electric and magnetic responses. We analyze the role of the anisotropy of the polarizability tensor of the unit cell and reveal the conditions for the optimal angular stability in symmetric absorption as well as polarization independence. Then we approximate the desirable behavior with a Huygens' metasurface whose reflectance is low in a wide frequency range while the absorption is total around a single resonance frequency. Reaching of the optimal angular stability was numerically demonstrated and the corresponding wide-angle and wide-band properties were experimentally checked.

Perfect optical absorbers in a wide range of incidence by photonic heterostructures containing layered hyperbolic metamaterials.

We theoretically and experimentally investigate the wide-angle perfect absorptance in a photonic heterostructure composed of a metal film and a truncated photonic crystal (PC) with layered hyperbolic metamaterials (HMMs) in the near ultraviolet and visible regions. The wide-angle perfect optical absorption depends on the dispersionless Tamm plasmon polarition (TPP) under TM polarization, which originates from reflection phase compensation condition between the metal and the truncated PC with HMMs. Our experimental results show nearly perfect absorptance over 0.91 in an angle range of 0-45 degree, which facilitates the design of perfect optical absorbers working in a wide angle range.

Ultra-broadband wide-angle perfect absorber in the visible regime through a thin grating–insulator–metal structure

A new thin grating-insulator-metal (GIM) structure with ultra-broadband wide-angle perfect absorption is proposed, and a general approach to this kind of multilayered structure is investigated based on the rigorous coupled-wave analysis method and the transfer matrix method. On the basis of this approach, the electromagnetic field distributions in each layer and optical diffraction coefficients are derived theoretically. Compared with a metal–insulator–metal (MIM) structure, the GIM structure consisting of a metal grating on top of a low-loss dielectric layer and a bottom metal layer can achieve a higher absorption with the smaller thickness that attributes to the extraordinary optical transmission of the top grating layer and the cavity resonance of the middle insulator layer. By optimizing the structural and material parameters, the materials from top to bottom are selected as Mn-Al2O3-Mn, whose thicknesses are 10 nm, 65 nm, and 70 nm, respectively. With these optimum parameters, better performance with average absorption over 95% in the visible regime is obtained. Furthermore, this structure retains near-perfect broadband absorption for large incidence angles and different polarizations. The conclusions presented here could have potential applications in optical devices, such as optical displacement detection and visible light absorption.

Monolayer-graphene-based broadband and wide-angle perfect absorption structures in the near infrared

Broadband optical absorption structures in the near infrared by coupling monolayer-graphene with periodical metal structures are proposed and demonstrated numerically. Optical absorption of graphene with over-50%-absorption bandwidth up to hundreds of nanometer caused by magnetic dipole resonances and magnetic coupling effect are investigated in detail, and the demonstrated bandwidths are one order higher than those caused by dielectric guiding mode resonances. In addition, the influences of geometrical parameters of structures are fully analyzed and these demonstrated structures show angular-insensitive absorption for oblique incidence in a large angular range. The demonstrated absorption structures in this work provide new design ideas in the realization of advanced graphene-based optoelectronic devices.

Ge2 Sb2 Te5 -Based Tunable Perfect Absorber Cavity with Phase Singularity at Visible Frequencies.

The metal-dielectric stacks-based asymmetric Fabry-Perot (F-P) cavity systems have recently attracted much interest from the scientific community for realizing perfect absorption over the spectral bands from visible to infrared since they possess a lithography-free design that is cost-effective and scalable. This study experimentally demonstrates an asymmetric F-P cavity system for achieving tunable wide angle perfect absorption and phase singularity. The proposed system shows tunable multiband perfect absorption in the visible spectral region by incorporating an ultrathin layer of phase change material such as Ge2 Sb2 Te5 (GST) in the stack. The system shows multi-narrowband perfect absorption with a maximum of 99.8% at a specific incident angle and polarization state when the GST is in amorphous phase; however, the absorption bands blueshift and broaden after switching to the crystalline phase. More importantly, the proposed scheme shows tunable phase singularity at the reflection-less point. The obtained tunable perfect absorption and abrupt phase change are solely due to the presence of a highly absorbing ultrathin layer of GST in the stack. Experimental results are validated using an analytical simulation model based on a transfer matrix method. The proposed scheme could find potential applications in active photonic devices such as phase-sensitive biosensors and absorption filters.

Wide-angle Spectrally Selective Perfect Absorber by Utilizing Dispersionless Tamm Plasmon Polaritons

We theoretically investigate wide-angle spectrally selective absorber by utilizing dispersionless Tamm plasmon polaritons (TPPs) under TM polarization. TPPs are resonant tunneling effects occurring on the interface between one-dimensional photonic crystals (1DPCs) and metal slab, and their dispersion properties are essentially determined by that of 1DPCs. Our investigations show that dispersionless TPPs can be excited in 1DPCs containing hyperbolic metamaterials (HMMs) on metal substrate. Based on dispersionless TPPs, electromagnetic waves penetrate into metal substrate and are absorbed entirely by lossy metal, exhibiting a narrow-band and wide-angle perfect absorption for TM polarization. Our results exhibit nearly perfect absorption with a value over 98% in the angle of incidence region of 0–80 degree.

SiO2/bi-layer GZO/Ag structures for near-infrared broadband wide-angle perfect absorption

In this work, near-infrared (NIR) perfect absorbers with a silicon dioxide (SiO2)/gallium-doped zinc oxide (GZO)/silver (Ag) multi-layer structure were designed and experimentally demonstrated. The results show that a broadband perfect absorption (PA) from 1.24 µm to 1.49 µm was achieved by adopting bi-layer GZO thin films with different carrier concentrations. This absorption remained higher than 97% for incident angles up to 60°. The perfect NIR absorber reported here has a simple structure as well as broadband and wide-angle absorption features, which is promising for practical applications.

The wide-angle perfect absorption based on the optical Tamm states

Based on the optical Tamm states (OTSs), a metal-distributed Bragg reflector (DBR) structure is presented. The existence of optical Tamm states is demonstrated by the dip of reflectivity spectrum in photonic band gap. The properties of the optical Tamm states are investigated by applying the transfer matrix method. The effects of different metal thicknesses and angles on the absorption are studied by numerical simulation. The wide-angle perfect absorption appears when the metal thickness is 39 nm.

Coherent perfect absorption in epsilon-near-zero metamaterials

Above-light-line surface plasmon polaritons can arise at the interface between a metal and epsilon-near-zero metamaterial. This unique feature induces unusual fast-wave non-radiative modes in a epsilon-near-zero material/metal bilayer. Excitation of this peculiar mode leads to wide-angle perfect absorption in low-loss ultrathin metamaterials. The ratio of the perfect absorption wavelength to the thickness of the epsilon-near-zero metamaterial can be as high as 10^4; the electromagnetic energy can be confined in a layer as thin as {\lambda}/10000. Unlike conventional fast-wave leaky modes, these fast-wave non-radiative modes have quasi-static capacitive features that naturally match with the space-wave field, and thus are easily accessible from free space. The perfect absorption wavelength can be tuned from mid- to far-infrared by tuning the epsilon = 0 wavelength while keeping the thickness of the structure unchanged.