A dual broadband terahertz bifunction absorber that can be actively tuned is proposed. The optical properties of the absorber were simulated and numerically calculated using the finite-difference time-domain (FDTD) method. The results show that when the conductivity of vanadium dioxide is less than σ0 = 8.5 × 103 S/m, the absorptance can be continuously adjusted between 2% and 100%. At vanadium dioxide conductivity greater than σ0 = 8.5 × 103 S/m, the absorption bandwidth of the absorber can be switched from 3.4 THz and 3.06 THz to 2.83 THz and none, respectively, and the absorptance remains above 90%. This achieves perfect modulation of the absorptance and absorption bandwidth. The physical mechanism of dual-broadband absorptions and perfect absorption is elucidated by impedance matching theory and electric field distribution. In addition, it also has the advantage of being polarization insensitive and maintaining stable absorption at wide angles of oblique incidence. The absorber may have applications in emerging fields such as modulators, stealth and light-guided optical switches.
In this article, we presented our proposal for a metamaterial perfect absorber (MPA) operating in the near-infrared band. Our MPA comprised a trapezoidal silver layer, a substrate layer, and an intermediate alumina layer. The transmission characteristics of MPA were analyzed by the three-dimensional (3D) finite difference time domain method. The simulation results were analyzed by equivalent circuit theory. The results show that the MPA achieved 100% absorption of transverse magnetic (TM) polarization and transverse electric (TE) polarization with resonance wavelength
λ
= 1492.5 nm. By varying the length of the bottom side of the trapezoid, the MPA’s resonance wavelength could be effectively tuned, and the absorption was maintained at above 99%. With the incidence angle of 0°–55°, the absorption remains above 90% at TE polarization and above 80% at 55°–70°. The absorption at the TM polarization remains above 99% when the incident angle is 0°–70°. A wide angle of incidence and good absorption were achieved. The sensitivity (S) and figure of merit were 228 nm/refractive index unit and 1378 RIU−1, respectively. The proposed absorber with excellent absorption in the range of infrared spectra has a promising application potential in fields such as energy harvesting and infrared sensors.
In this paper, a band-stop filter based on a surface plasmon polariton metal–insulator–metal is designed and studied. The relationship between wavelength and filter transmittance is simulated using the finite difference time domain method and coupled mode theory. Compared with a single-diamond resonator, the minimum transmittances of the double-diamond resonator and double-rectangular resonator at a fixed wavelength are increased by 11.33% and 14.25%, respectively, achieving an enhancement effect. The research results also show that the sensitivity of the filter can reach 860 nm/RIU. The structure has good application prospects in optical integration, optical communication, and optical information processing.
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