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 absorptance rate of over 90% for TM polarization at the angle of incidence 10.8°. This absorptance 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 absorptance of TE polarization was found at the angle of incidence 14.5° and that of azimuth 45° 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.

对波长为375 nm的近紫外光进行了波长和偏振选择性吸收器的理论设计和实验验证。此外，利用电磁场分析阐明了吸收机制。本研究开发的吸收体采用Al纳米孔阵列结构，具有双层、二维金属纳米周期结构。该吸收体选择性吸收波长为375 nm的近紫外光，在入射角10.8°时TM偏振的最大吸收率达到90%以上。该吸收率被证实​​是由于法诺共振，该共振源自纳米孔边缘处产生的局域表面等离子体激元与沿z轴方向传播的表面等离子体共振之间的耦合。此外，该吸收体在不同的入射角和方位角等条件下不仅可以选择性地完全吸收TM偏振光，还可以完全吸收TE偏振光。由于两种TM偏振的组合表面等离子体共振，在入射角14.5°和方位角45°处发现TE偏振的完美吸收。该方法有望应用于近紫外光中的中间光学元件，例如光开关和紫外光通信。