Ultra-narrow band absorber in visible region based on the couple of Fabry-Pérot and guide mode resonance

Abstract

Metasurface based near perfect absorbers show great potential in the regulation of ultra-narrow visible light absorption with their advantages of ultra-high light absorption, high integration and wide wavelength adjustable range. However, there is a bottleneck in achieving narrower light absorption through a single resonant absorption mechanism. In this work, we proposed a low-cost absorber based on Ag/Al2O3/Ag sandwich structure. The proposed absorber successfully realizes the ultra-narrow visible light absorption regulation through the coupling effect of Fabry-Pérot (FP) resonance and guide mode resonance (GMR). When the absorption peak is 435 nm (blue light), 546 nm (green light) and 699 nm (red light), the full width at half maxima (FWHM) is 5.34 nm, 2.14 nm and 2.88 nm respectively. Further, based on this kind of absorber unit, we designed an encryption structure that can display the two-dimensional code image only under the irradiation of a specific wavelength, showing its potential application value in the field of image encryption and anti-counterfeiting recognition.