In this paper, we theoretically design and numerically verify a broadband plasmonic absorber that works continuously in ultraviolet to near-infrared region. Different from the traditional metal-insulator-metal (MIM) three-layer structure, our perfect absorber is based on insulator-metal-insulator-metal (IMIM) four-layer structure. This perfect absorber has 280 nm ultra-thin thickness, and the combination of refractory metal titanium nitride and high-melting-point insulator silica gives our absorber strong thermal stability. The novel titanium nitride ring-square array layer combines the absorption of different wavelength bands so that the absorber can achieve a continuous absorption of more than 90% from wavelength 200 to 1200 nm. Finite-difference time-domain (FDTD) calculated average absorption rate reaches 94.85%, which 99.40% maximum absorption at wavelength 270 nm and 90.30% minimum absorption at 390 nm. In addition, polarization independence under normal incidence and large incident angle insensitivity under oblique incidence, making our perfect absorber more advantageous in applications such as solar energy collection, photothermal conversion, and invisibility cloak.
In this paper, we theoretically investigate a tunable ultra-narrow band absorber consisting of lamellar structure in the near-infrared wavelength range. The absorption efficiency is 99.9% under normal incidence and the full width at half maximum (FWHM) is only 4nm. The high absorption is attributed to the surface plasmon resonance (SPR), which increases the interaction volume of the optical field. The ultra-narrow band absorber has a high refractive index sensitivity of 1208nm/RIU in a wide refractive index range of 1.33 to 1.40 and a high figure of merit of 302. Besides, the influence of structure parameters on the sensing performance are also investigated. Due to its easiness to be fabricated, the proposed structure has potential in sensing application.
We report a dual-band perfect absorber based on nanodisk array for sensing application in the visible region. Due to the excitation of the magnetic resonance mode, a narrow band absorption peak appears and the absorption rate is greater than 99.9%. The other is due to the excitation of local surface plasmon resonance mode, exhibiting broadband absorption characteristics, and the absorption value is greater than 80%. This structure has a wide angular range absorption characteristic. Finally, we calculated the sensing performance of the structure with refractive index ranging from 1.33 to 1.37. The refractive index sensitivity is 250 nm/RIU and 170 nm/RIU. Therefore, our research provides an important theoretical guidance for narrow-band absorption in the visible region for sensing measurements. This has important application prospects in imaging, sensing and optoelectronic devices.