When surface plasmon resonance (SPR) occurs, the incident light is absorbed by the surface of the SPR structure, thus minimizing the intensity of the reflected light. Therefore, the SPR method is adopted in this paper to achieve perfect absorption of the absorbent. In this paper, we first propose a multi-frequency broadband absorber structure based on graphene SPR, which uses the continuous resonance of patterned graphene surface plasmon in the frequency spectrum to form a multi-frequency broadband absorption. In this simulation, a sandwich-stack structure was adopted, whereby the patterned graphene is situated on top of the SiO₂ layer and the metal layer. The broad-band absorption bands of the absorber were obtained as 4.14–4.38 THz, 5.78–6.36 THz, and 7.87–8.66 THz through the analog simulation of finite-difference time-domain method (FDTD) solutions. Then, based on the multi-layer resonant unit structure, through the superposition and combination of absorbing units responding to different frequency bands, the perfect absorption of ultra-wideband is achieved. The data results illustrate that the total absorption bandwidth of the absorber is 2.26 THz, and the relative absorption bandwidth B_w is equal to 28.93%. The electric field in X-Y direction of the absorber in the perfect absorption band is analyzed, respectively, and the dynamic tunability of the absorber is studied. Finally, we studied whether the absorbing structure still has efficient absorption characteristics for the two polarization modes when the incident angle is changed from 0° to 70°. The structure model proposed has potential value for application in terahertz photoelectric detection, filtering, and electromagnetic shielding.

Since the use of chemical fuels is permanently damaging the environment, the need for new energy sources is urgent for mankind. Given that solar energy is a clean and sustainable energy source, this study investigates and proposes a six-layer composite ultra-wideband high-efficiency solar absorber with an annular microstructure. It achieves this by using a combination of the properties of metamaterials and the quantum confinement effects of semiconductor materials. The substrate is W–Ti–Al₂O₃, and the microstructure is an annular InAs-square InAs film–Ti film combination. We used Lumerical Solutions’ FDTD solution program to simulate the absorber and calculate the model’s absorption, field distribution, and thermal radiation efficiency (when it is used as a thermal emitter), and further explored the physical mechanism of the model’s ultra-broadband absorption. Our model has an average absorption of 95.80% in the 283–3615 nm band, 95.66% in the 280–4000 nm band, and a weighted average absorption efficiency of 95.78% under AM1.5 illumination. Meanwhile, the reflectance of the model in the 5586–20,000 nm band is all higher than 80%, with an average reflectance of 94.52%, which has a good thermal infrared suppression performance. It is 95.42% under thermal radiation at 1000 K. It has outstanding performance when employed as a thermal emitter as well. Additionally, simulation results show that the absorber has good polarization and incidence angle insensitivity. The model may be applied to photodetection, thermophotovoltaics, bio-detection, imaging, thermal ion emission, and solar water evaporation for water purification.

In this study, we investigate a physical mechanism to improve the light absorption efficiency of graphene monolayer from the universal value of 2.3% to about 30% in the visible and near-infrared wavelength range. The physical mechanism is based on the diffraction coupling of surface plasmon polariton resonances in the periodic array of metal nanoparticles. Through the physical mechanism, the electric fields on the surface of graphene monolayer are considerably enhanced. Therefore, the light absorption efficiency of graphene monolayer is greatly improved. To further confirm the physical mechanism, we use an interaction model of double oscillators to explain the positions of the absorption peaks for different array periods. Furthermore, we discuss in detail the emerging conditions of the diffraction coupling of surface plasmon polariton resonances. The results will be beneficial for the design of graphene-based photoelectric devices.

In recent years, ZnO nanomaterials have achieved great performance in solar energy applications. How to synthesize a ZnO nanocomposite structure with high photoelectric conversion efficiency has become an urgent problem to solved. In this paper, a narrow band gap bismuth trioxide (Bi₂O₃) coated on a ZnO nanoarray by magnetron sputtering was used to prepare a composite heterojunction ZnO/Bi₂O₃. Studies have found that ZnO/Bi₂O₃ exhibits excellent photoelectric conversion performance. By preparing a composite heterostructure of ZnO/Bi₂O₃, it can effectively compensate for the insufficient absorption of ZnO in the visible light range and inhibit the recombination of carriers within the material. The influence of Bi₂O₃ thickness on the microstructure and electronic structure of the ZnO/Bi₂O₃ composite structure was explored and analyzed. The energy gap width of the composite heterostructure decreases with the increase in the Bi₂O₃ thickness on the surface of the ZnO nanorod array. At the same time, the conductive glass composite film structure is simple to prepare and is very environmentally friendly. The ZnO/Bi₂O₃ composite heterogeneous material prepared this time is suitable for solar cells, photodetectors, photocatalysis and other fields.

We numerically investigate the multipolar plasmonic resonances of Aluminum nanoantenna tuned by a monolayer graphene from ultraviolet (UV) to visible regime. It is shown that the absorbance of the plasmonic odd modes (l = 1 and l = 3) of graphene–Al nanoribbon structure is enhanced while the absorption at the plasmonic even modes (l = 2) is suppressed, compared to the pure Al nanoribbon structure. With the presence of the monolayer graphene, a change in the resonance strength of the multipolar plasmonic modes results from the near field interactions of the monolayer graphene with the electric fields of the multipolar plasmonic resonances of the Al resonator. In particular, a clear absorption peak with a high quality (Q)-factor of 27 of the plasmonic third-order mode (l = 3) is realized in the graphene–Al nanoribbon structure. The sensitivity and figure of merit of the plasmonic third-order mode of the proposed Graphene–Al nanoribbon structure can reach 25 nm/RIU and 3, respectively, providing potential applications in optical refractive-index sensing.

Designing various nanostructures to achieve narrowband light reflection resonances is desirable for optical sensing applications. In this work, we theoretically demonstrate two narrowband light reflection resonances resulting from the excitations of the zero-order transverse magnetic (TM) and transverse electric (TE) waveguide modes, in a waveguide structure consisting of an Au sphere array on an indium tin oxide (ITO) spacer on a silica (SiO₂) substrate. The positions of the light reflection resonances can be tuned easily, by varying the array periods of gold (Au) spheres or by changing the thickness of the ITO film. More importantly, the light reflection resonances have a very narrow bandwidth, the full width at half maximum (FWHM) of which can be reduced to only several nanometers for the zero-order TM and TE waveguide modes. The conventionally defined performance parameters of sensors, sensitivity (S) and figure of merit (FOM), have quite high values of about 80 nm/RIU and 32, respectively, in the visible wavelength range.