Narrow Results

We present a simple method for enhancing the bandwidth and absorptivity of metamaterial perfect absorber (MPA)-formed disk resonators. Utilizing low-conductivity polymer and near-field coupling of multi-band resonances, a 6.8 GHz broadband MPA is achieved with absorption over 90%. The proposed MPA also shows polarization-independent absorption behavior. Furthermore, the structural design is useful for making broadband MPA and can be applied to higher frequencies with a simple configuration.

In this paper, a polarization-insensitive magnetic tunable perfect metamaterial absorber is analyzed which shows its functionality as a refractive index (RI) sensor. The unit cell structure of reported absorber consists of a cross-shaped Indium Arsenide (InAs) array over aluminum ground plane and has dimensions less than ${\lambda }_c/4$ with thickness of 7.5$\mu \mathrm{\text{m}}$ and periodicity of 9$\mu \mathrm{\text{m}}$ making it an ultra-thin absorber. The proposed absorber provides an average absorption of 99.99% on the implementation of magnetic field (B) at 0.4T. The resonance frequency and corresponding absorption rates can be controlled by varying the magnetic field from $B=0.1$–0.4T which provides high absorption as well as shift in the frequency spectrum by 0.3THz/T. Additionally, parametric analysis has also been done to confirm the selection of the optimum value of the designed parameters of the structure. Furthermore, simulation results reveal that the proposed structure is very sensitive to the change of RI values in the surroundings thus, the proposed structure can be employed as a RI sensor high sensitivity of 1.083THz/RIU over the range of 1–1.6RI. In addition, the result shows that the sensor can detect different chemical compounds such as ethanol, gasoline, paraffin, sodium chloride, carbon disulfide with an average sensitivity of 0.925THz/RIU. Thus, the proposed absorber with obtained sensitivity can be utilized as a biochemical sensor, making it one of the best contenders for chemical industry uses in diagnosis of different hazardous chemicals as well as finding its applicability in biomedical uses.

This paper designed a perfect optical absorber based on three-tier gate nanostructure, which shows a wide-band perfect absorption in the wavelength range of 200–560 nm as a transverse wave incidents to the nanostructure with the incident angle 35°< θ< 65°. When θ = 45°, a wide absorption band with the absorption rate more than 94% is observed, with the maximum of absorption rate reaching 99.3% at the wavelength of 430 nm. We also analyze the thermal characteristics of the perfect absorber. The band ranging from 560 nm to 1200 nm presents an increasing absorption rate with the increase of temperature. The calculation results of multi-physics analysis indicate that different cooling method causes different temperature distribution for the perfect absorber. This three-tier gate perfect absorber may find applications on broadband visible detectors, microbolometer and thermal imaging.

We design and numerically investigate a wide angle and broadband perfect absorber with compact multilayer structures. The proposed structure is composed of three stacks of semiconductor films and one metal layer. The absorber presents a broadband absorption between 450 nm and 700 nm with an average absorption above 99.2%. For oblique incidence, the absorber shows an average absorption about 90% for a wide range of incident angles from 0${}^{\circ }$ to 60${}^{\circ }$ with p polarization and s polarization. The electrical field intensity distributions are also studied to disclose the broadband absorption mechanism. This designed broadband absorber appears to have very promising applications in solar thermal energy harvesting, thermal emitters and detection.

An ultrathin metasurface-based absorber consisting of titanium nitride (TiN) nano-disk arrays–dielectric layer-TiN substrate is proposed in this paper. The absorber exhibits near-unity absorption in the whole visible range of 380–780 nm. Our results demonstrate that the proposed metasurface-based absorber is not only independent of light polarization, but also exhibits angle-independent absorption behavior for oblique incidence up to 70${}^{\circ }$. The high absorption performance of the TiN nano-disk arrays-based absorber can attribute to two different loss mechanisms associated with the intrinsic loss and plasmonic resonance.

We demonstrate an, ultra-narrow-band perfect absorber based on high-order magnetic plasmonic resonance, which is polarization independent because of the ring element in the structure. When the thickness $t$ of MgF₂ is 60nm, the absorption at frequency 424.5THz is close to 1, its full width at half maximum (FWHM) is 13nm. In our structure, a wavelength sensitivity about 190nm/RIU is achieved by utilizing the absorption peaks alter upon the refractive index change. In addition, we also discuss the figure of merit (FOM*) under different reflective index of sample surface. Therefore, the ultra-narrow-band perfect absorber will provide the great potential applications to filters and plasmonic refractive index sensors.

A broadband and polarization-insensitive optical metamaterial absorber (MA) based on the refractory metal chromium (Cr) closed-ring resonator is theoretically investigated. The semiconducting silicon dioxide (SiO${}_2)$ thin film is introduced as the space layer in this sandwiched structure. Utilizing the symmetrical geometry of the proposed MA structure, polarization insensitivity of the broadband absorption is gained. The simulation results show that the absorber with Cr closed-ring array obtains an average absorption of 99.25% from 400nm to 900nm, covering the total visible wavelength range. This compact design may have potential applications in solar energy harvesting, thermal imaging, and emissivity control.

We propose a new broadband metamaterial perfect absorber (MPA) based on structure of metallic dishes in the THz region. It demonstrated that the coupling interaction between the central dish and adjacent dishes leads to absorption characteristics. By optimizing the geometrical structure, the bandwidth is gained up to 1.0THz with absorption better than 90%. The mechanism of the absorption results was explained by induced current, magnetic and electric distributions. Furthermore, LC equivalent circuit was used to elucidate resonant frequencies. The obtained results can provide a general guideline for fabricating broadband MPA.