Four peak and high angle tilted insensitive surface plasmon resonance graphene absorber based on circular etching square window

Abstract 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 achieves absorption rates of 96.55%, 98.71%, 99.37%, and 99.96% at four wavelengths: 2092.24 nm, 2180.67 nm, 2230.08 nm, and 2336.17 nm, respectively, with an average absorption rate of 98.54%. Through simulations of electric field distribution intensity and verification of whether it meets the impedance matching theory, the physical mechanism behind the high absorption rate of the four peaks is explored. The absorber's polarization insensitivity and tilt insensitivity are investigated through different polarized light and tilted incident angles. It is found that the absorber is insensitive to polarized light and has excellent insensitivity within a tilt angle range of 0° to 65°. The sensitivities of the four peaks are 501.54 nm/RIU, 565.76 nm/RIU, 605.47 nm/RIU, and 582.70 nm/RIU, 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.