TM- and TE-polarization-selective narrowband perfect absorber for near-ultraviolet light using Fano resonance in an aluminum nanohole array structure

Abstract

Abstract A wavelength- and polarization-selective absorber for near-ultraviolet light with a wavelength of 375 nm was theoretically designed and experimentally verified. Furthermore, the absorption mechanism was elucidated using electromagnetic field analysis. The absorber developed in this study employs an Al nanohole array structure, which has a double-layer, two-dimensional metal nano-periodic structure. This absorber selectively absorbs near-ultraviolet light with a wavelength of 375 nm and achieves a maximum absorption rate of over 90% for TM polarization at the angle of incidence 10.8o. This absorption was confirmed to be due to Fano resonance originating from the coupling between localized surface plasmon generated at the nanohole edges and propagating surface plasmon resonance along the z-axis direction. Furthermore, this absorber can selectively and completely absorb not only TM- but also TE-polarized light under conditions such as varying angle of incidence and azimuth. The perfect absorption of TE polarization was found at the angle of incidence 14.5o and that of azimuth 45o due to the combined surface plasmon resonance of the two kinds of TM polarization. This method is expected to be applied as an intermediate optical element in near-ultraviolet light, such as optical switching, and in ultraviolet optical communications.