A Dual-Polarized and Wideband Switchable Absorption/Transmission Frequency Selective Surface With Multispectral Functionality

In this paper, a microwave absorption/transmission switchable frequency selective surface (A/T-SFSS) with enhanced multispectral functionality in the visible and infrared spectra is developed. By simply controlling the flowing liquid medium (pure water in this work), efficient manipulation of two opposite states, absorption and transmission, can be achieved in the microwave frequency band with a wide switchable bandwidth. When functioning as a wideband absorber, the proposed A/T-SFSS exhibits an absorption rate over 90% from 6.50 GHz to 10.48 GHz. Conversely, it can be employed as a transmitter with high selectivity, featuring a second-order passband with two transmission zeros at both sides and an impressive −1 dB transmission bandwidth ranging from 7.04 GHz to 8.47 GHz. The design also demonstrates stable responses under different polarizations and incident angles. Additionally, the proposed A/T-SFSS offers flexibility in tailoring the visible and infrared spectra by actively changing the color and temperature of aqueous solutions. The influences of electromagnetic (EM) parameters and liquid temperature variations on the microwave performance are also thoroughly investigated. Finally, experimental verification through free-space tests of scattering parameters, image analyses of grayscale histogram, and infrared radiation detected by thermal imager provides compelling evidence for the potential of the developed A/T-SFSS. The results demonstrate its remarkable capability to achieve switchable microwave functionality as well as active control of visible light and infrared spectra, which significantly contributes to the field by advancing the development of multifunctional and multispectral structures.