Asymmetric plasmonic-semiconductor cavities for angle-adjusted dual-band differential absorption responses

Light absorbers are desirable for wide applications in optoelectronic devices. In this work, we propose and demonstrate a new plasmonic absorber platform, which can support two sharp absorption bands with differential features via tuning the incident angle. The absorber is formed by an asymmetrical metal–semiconductor–metal(MSM) stack intercalated by metal micro-cavities. The maximal absorption for the two peaks respectively reaches 99.8% (λ=0.983μm) and 98.9% (λ=1.187μm). Importantly, the dual-band absorber shows remarkable differential properties when the incident angle is tuned. For instance, the wavelength position is only with a 2 nm fluctuation for the first band in the shorter wavelength range, suggesting a nearly stable state during the angle changes from 0° to 50°. Nevertheless, the wavelength position shifts up to 37.5 nm for the second band in the longer wavelength region, indicating an angle-sensitive absorption. These properties are mainly related to the relaxed resonant fields from the MSM cavities and their different coupling modes to the adjacent metal cavities in this asymmetric structure. These new findings could pave applications for differential optoelectronic manipulations, filters and photo-detection, etc. •A new plasmonic-semiconductors based absorber platform is proposed.•Differential absorption features are obtained via tuning the incident angle.•The maximal absorption reaches 99.8% (0.983 μm) and 98.9% (1.187 μm).•It can pave applications for differential optoelectronic manipulations, filters, etc.