Highly band-selective meta-surfaces exhibiting perfect near infrared absorption and concurrent visible band sensing: A numerical study

We report a highly band-selective, bifunctional meta-surface that serves as an ultra-wide perfect absorber for near-infrared (NIR) band and a visible-band sensor, based on a rational design strategy involving stacking and/or grating of metals, inorganic insulators, and stimuli-responsive materials. PNIPAAm-based hydrogel was utilized as a layer of stimuli-responsive insulator, which is allowed to reversibly swell and collapse in one dimension in response to stimuli such as ambient temperature and chemical environment to empower the sensing capability in the visible band, with the perfect absorption in NIR region intact. The average absorption reached an impressive 99.4% from 780 to 2500 nm, which is attributed to the synergy of localized surface plasmon (LSP), propagating surface plasmon (PSP), and cavity mode. The reported bi-functional meta-surface is particularly attractive for band-selective solar energy harvesting, naked-eye sensing, and adaptive imaging.

Automated summary

We have reported a highly band-selective, bifunctional meta-surface that can work as an ultra-wide perfect absorber for near-infrared (NIR) band as well as a visible-band sensor. The rational design strategy involves stacking and/or grating of metals, inorganic insulators, and stimuli-responsive materials. A PNIPAAm-based hydrogel layer was used as a stimuli-responsive insulator, which can reversibly swell and collapse in one dimension in response to stimuli, enabling the sensing capability in the visible band while maintaining perfect absorption in the NIR region.