A Perfect Absorber Based on Similar Fabry-Perot Four-Band in the Visible Range

Abstract

A simple metamaterial absorber is proposed to achieve near-perfect absorption in visible and near-infrared wavelengths. The absorber is composed of metal-dielectric-metal (MIM) three-layer structure. The materials of these three-layer structures are Au, SiO 2 , and Au. The top metal structure of the absorber is composed of hollow three-dimensional metal rings regularly arranged periodically. The results show that the high absorption efficiency at a specific wavelength is mainly due to the resonance of the Fabry-Perot effect (FP) in the intermediate layer of the dielectric medium, resulting in the resonance light being trapped in the middle layer, thus improving the absorption efficiency. The almost perfect multiband absorption, which is independent of polarization angle and insensitivity of incident angle, lends the absorber great application prospects for filtering and optoelectronics.Nanomaterials 2020, 10, 488 2 of 10 to their absorption band, absorption capacity, absorption principle, and absorption spectrum [8][9][10][11][12][13][14]. For example, the Salisbury screen is mainly used in the military to reduce the reflection of radar detectors by canceling the interference of reflected microwaves by the reflection layer [15]. The same principle can be used in optical frequencies to design an anti-reflective film on a camera lens or glass. For another example, a pyramid-shaped structure can increase the number of reflections and scatter in the structure by matching the impedance of free space, thus increasing the absorption efficiency [16].Since the concept of the perfect absorber was introduced in 2008, the research on superstructure electromagnetic material absorbers has shown exponential growth year by year [17][18][19][20]. From the initial microwave frequency band to terahertz [20,21], infrared [22,23], and visible frequency band [24][25][26][27], a large number of studies have been conducted, and absorption bandwidth also includes single-frequency absorption, dual-frequency absorption, multi-frequency absorption, and broadband absorption [28][29][30][31][32][33]. Compared with the traditional absorption materials, the advantage of the superstructure material absorber lies in the structure size, arrangement, and different materials selected to form the dual-frequency, multi-frequency, or dual-band absorber [34][35][36]. The structure size is small and the processing method is simple, which is conducive to the integration in the period surface [37][38][39]. The structure or quantity can be flexibly adjusted to achieve different absorption purposes. Due to the variety of absorbers, the absorbers have a different applicable wavelengths, bandwidths, structure characteristics, adjustable abilities, and absorption principles. In this paper, a multi-band metamaterial absorber in the visible light range is designed from the perspective of the absorption frequency band. By changing the structure size of the absorber and the metal structure on the surface, the absorber can achieve a broader tolerance range for polar...

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