We present a novel, structurally simple, multifunctional broadband absorber. It consists of a patterned vanadium dioxide film and a metal plate spaced by a dielectric layer. Temperature control allows flexible adjustment of the absorption intensity from 0 to 0.999. The modulation mechanism of the absorber stems from the thermogenic phase change properties of the vanadium dioxide material. The absorber achieves total reflection properties in the terahertz band when the vanadium dioxide is in the insulated state. When the vanadium dioxide is in its metallic state, the absorber achieves near-perfect absorption in the ultra-broadband range of 3.7 THz–9.7 THz. Impedance matching theory and the analysis of electric field are also used to illustrate the mechanism of operation. Compared to previous reports, our structure utilizes just a single cell structure (3 layers only), and it is easy to process and manufacture. The absorption rate and operating bandwidth of the absorber are also optimised. In addition, the absorber is not only insensitive to polarization, but also very tolerant to the angle of incidence. Such a design would have great potential in wide-ranging applications, including photochemical energy harvesting, stealth devices, thermal emitters, etc.

In this paper, a multi-mode surface plasmon resonance absorber based on dart-type single-layer graphene is proposed, which has the advantages of polarization independence, tunability, high sensitivity, high figure of merit, etc. The device consists of a top layer dart-like patterned single-layer graphene array, a thicker silicon dioxide spacer layer and a metal reflector layer, and has simple structural characteristics. The numerical results show that the device achieves the perfect polarization-independent absorption at the resonance wavelengths of λ_I = 3369.55 nm, λ_II = 3508.35 nm, λ_III = 3689.09 nm and λ_IV = 4257.72 nm, with the absorption efficiencies of 99.78%, 99.40%, 99.04% and 99.91%, respectively. The absorption effect of the absorber can be effectively regulated and controlled by adjusting the numerical values such as the geometric parameters and the structural period p of the single-layer graphene array. In addition, by controlling the chemical potential and the relaxation time of the graphene layer, the resonant wavelength and the absorption efficiency of the mode can be dynamically tuned. And can keep high absorption in a wide incident angle range of 0° to 50°. At last, we exposed the structure to different environmental refractive indices, and obtained the corresponding maximum sensitivities in four resonance modes, which are S_I = 635.75 nm RIU⁻¹, S_II = 695.13 nm RIU⁻¹, S_III = 775.38 nm RIU⁻¹ and S_IV = 839.39 nm RIU⁻¹. Maximum figure of merit are 54.03 RIU⁻¹, 51.49 RIU⁻¹, 43.56 RIU⁻¹, and 52.14 RIU⁻¹, respectively. Therefore, this study has provided a new inspiration for the design of the graphene-based tunable multi-band perfect metamaterial absorber, which can be applied to the fields such as photodetectors and chemical sensors.

A metamaterial absorber based on the thermotropic phase change material VO₂ has been designed. Flexible switching of absorption performance (bandwidth is 3.3 THz) can be achieved through temperature adjustment.

A four-band terahertz tunable narrow-band perfect absorber based on a bulk Dirac semi-metallic (BDS) metamaterial with a microstructure is designed. The three-layer structure of this absorber from top to bottom is the Dirac semi-metallic layer, the dielectric layer and the metal reflector layer. Based on the Finite Element Method (FEM), we use the simulation software CST STUDIO SUITE to simulate the absorption characteristics of the designed absorber. The simulation results show that the absorption rate of the absorber is over 93% at frequencies of 1.22, 1.822, 2.148 and 2.476 THz, and three of them have achieved a perfect absorption rate of more than 95%. We use the localized surface plasmon resonance (LSPR), impedance matching and other theories to analyze its physical mechanism in detail. The influence of the geometric structure parameters of the absorber and the incident angle of electromagnetic waves on the absorption performance has also been studied in detail. Due to the rotational symmetry of the structure, the designed absorber has excellent polarization insensitivity. In addition, the maximum adjustable range of absorption frequency is 0.051 THz, which can be achieved by changing the Fermi energy of BDS. We also define the refractive index sensitivity (S), which is 39.1, 75.4, 119.1 and 122.0 GHz RIU⁻¹ for the four absorption modes when the refractive index varies in the range of 1 to 1.9. This high-performance absorber has a very good development prospect in the frontier fields of bio-chemical sensing and special environmental detection.

We propose an ultrathin-film c-silicon (silicon is 0.9 μm)/ZnO heterojunctions solar cells. It has been found that the average absorption in the wavelength range from 300 to 1400 nm reaches 93.16%. The short circuit current density ( J _sc ) reached 41.94 mA cm ⁻² . The efficiency of the solar cell reaches 18.97%.

This article introduces a new type of graphene-based perfect absorber that features tunability across four wave peaks and high sensitivity, consisting of Ag–SiO₂–graphene. By controlling the Fermi level and relaxation time of graphene, the tunability of the absorber is achieved, and by changing the refractive index of SiO₂, the selectivity of the resonant wavelength is realized. The results show that the absorber has an average absorption rate of 98.54% at four wavelengths: 2092.24 nm, 2180.67 nm, 2230.08 nm, and 2336.17 nm. The electric field distribution intensity is simulated to verify whether it meets the impedance matching theory, exploring the physical mechanism behind the high absorption rates at these four peaks. Different polarizations and inclined incidence angles are investigated to explore the absorber’s insensitivity to polarization, demonstrating excellent insensitivity within an inclination angle range from 0° to 65°. The sensitivities of the four peaks are 501.54 nm RIU⁻¹, 565.76 nm RIU⁻¹, 605.47 nm RIU⁻¹, and 582.70 nm RIU⁻¹, respectively. Finally, the practical application of the absorber in detecting aqueous solutions of 10%, 20%, 25% glucose solutions, and 30%, 50% sugar solutions is simulated, and the results show that the absorber has good sensing performance. This paper’s absorber features four-peak perfect absorption and excellent tilt insensitivity, good refractive index sensitivity, and holds great potential applications in detectors and optical communication systems.