With global energy demand surging and traditional energy resources diminishing, the solar absorber featuring optimized design shows substantial potential in areas like power generation. This study proposes a solar absorber that is insensitive to wide-angle incidence and polarization. It has a cylindrical structure with square holes, which is constructed from titanium nitride (TiN). The calculation results indicate that, for plane waves, the average absorption of this solar absorber across the wavelength range of 300–2500 nm reaches 92.4%. Moreover, its absorption rate of the solar spectrum corresponding to AM1.5 reaches 94.8%. The analysis of the characteristics within the electric and magnetic field profiles indicates that the superior absorption properties arise from a cooperative resonance effect. This effect originates from the interaction among surface plasmon resonance, guided-mode resonance, and cavity resonance. In this study, the geometric parameters of the solar absorber’s structure significantly influence its absorption performance. Therefore, we optimized these parameters to obtain the optimal values. Even at a large incident angle, this absorber maintains high absorption performance and shows insensitivity to the polarization angle. The findings expected from this study are likely to be of considerable practical importance within the realm of solar photothermal conversion.

At present, most of the reported metasurface structure absorbers show that its working band cannot be regulated actively. In this study, a dynamic tunable narrow-band perfect absorption structure for fiber-optic communication band based on liquid crystal (LC) is proposed and studied. The structure is mainly composed of two effective tiers. The top tier gold array and the bottom tier reflective gold film, which are separated by a SiO₂-LC dielectric medium interlayer to form a metal–dielectric–metal structure. Due to the unique optical properties of LCs, its index of refraction can be changed by adjusting the bias voltage and temperature, so as to adjust the resonance wavelength actively. The designed structure is analyzed by finite element method and the coupled mode theory is used to verify the analysis results. The designed structure has a 99.92% absorption effect in the most commonly used band of fiber-optic communication. Due to the symmetry of the absorber structure, the device is not sensitive to the polarization state of the excitation source. Moreover, the absorber exhibits an unusual dependence on the incident angle, which can be attributed to the anisotropy of the LC. Based on the dependence of incident angle, a plasma optical switch with large ON/OFF ratio (η) of 27.395 dB and nearly flawless modulation depth of 99.818% can be realized. It is believed that this structure can provide a method for the dynamic control of near infrared electromagnetic waves, and to be applied in electromagnetic energy absorption, filtering and plasma optical switch system.

We propose an ultracompact structure to efficiently achieve control and tuning of dual Fano resonance (DFR) lineshapes, in which a waveguide Fabry-Perot (FP) resonator is side-coupled to a double-nanobeam-cavity photonic molecule (FP-DNCPM). We theoretically and numerically demonstrate the transmission spectra of the FP-DNCPM coupled system can be converted between dual Lorentzian resonance (DLR) lineshapes and DFR lineshapes with arbitrary asymmetries by simply varying the phase shift in the waveguide FP resonator. We also show that our proposed system provides modulation capabilities for extinction ratio (ER), slope rate (SR), and group delay and we observe significant improvements in the performance of ER, SR, and slow light in the DFR lineshapes compared to the results obtained in the DLR lineshapes. We believe that our proposed structure holds significant potential as the candidate for multi-wavelength high-performance optical switches, modulators, slow light devices, and high-sensitivity sensors.

We propose and investigate a graphene periodic subsurface structure consisting of a coplanar pair of graphene ring resonators and a graphene ribbon. The Fano-like interference can be actively regulated by the applied magnetic field, incident angle and Fermi energy. Since the excited charges of graphene monolayer have cyclotron properties in the external magnetic field, the transmittance and line-shape can be effectively controlled. At a certain frequency, different magnetic fields have different effects on the conductivity tensor of graphene, which affects the metallic properties of graphene, leading to changes in the transmittance. The Fano-like line-shape can be regulated by adjusting the incident angle to delay the phase between adjacent graphene sheets. In addition, the resonance frequency can be electrically regulated through Fermi energy. Finite element method is introduced to analyze the graphene periodic structure and the results are demonstrated by multimode interference coupled mode theory. The Faraday rotation angle exceeding 85° are observed in a small magnetic flux density B of about 0.5 T. Moreover, a plasma-optic switching with high ON/OFF ratio and large modulation depth (MD) is designed, whose ON/OFF ratio (η) and MD are 19.921 dB and 98.982%, respectively. Notably, combining the influence of magnetic flux density on transmittance and the modulation of resonance frequency by Fermi energy, optical switching can be implemented at any frequency within the frequency range studied. These results provide methods for active regulation of electromagnetic waves in the terahertz field and have potential applications in optical switching and integrated photonic circuit.

In this study, a dynamically tunable terahertz device based on a VO₂–graphene hybrid metasurface is proposed, which realizes the dual functions of ultra-wideband absorption and efficient transmission through VO₂ phase transformation. At 345 K (metallic state), the device attains an absorption efficiency exceeding 90% (average 97.06%) in the range of 2.25–6.07 THz (bandwidth 3.82 THz), showing excellent absorption performance. At 318 K (insulated state), the device achieves 67.66–69.51% transmittance in the 0.1–2.14 THz and 7.51–10 THz bands while maintaining a broadband absorption of 3.6–5.08 THz (an average of 81.99%). Compared with traditional devices, the design breaks through the performance limitations by integrating phase change material control with 2D materials. The patterned graphene design simplifies the fabrication process. System analysis reveals that the device is polarization-insensitive and tunable via graphene Fermi energy and relaxation time. The device’s excellent temperature response and wide angular stability provide a novel solution for terahertz switching, stealth technology, and sensing applications.