Transparent and broadband switchable absorber/reflector based on structured water medium

Abstract

A reconfigurable absorber/reflector, which has optical transparency and broadband switching function, is developed based on structured water medium. The conductive indium tin oxide (ITO) coating is deposited on a thin polyethylene terephthalate (PET) film to act as the reflective backplane. Pure water is encapsulated by polydimethylsiloxane (PDMS) materials to construct structured water. The average optical transmittance is about 61.88%/56.44% in the visible spectrum of 380 – 760 nm with/without pure water. Based on the super-element configuration and the stacking technique, an obvious switching function from broadband absorption (12.47 – 28.43 GHz) to broadband reflection (12 – 30 GHz) can be attained under normal incidence through the injection and discharge of pure water,. Besides, the broadband switchable characteristics of the proposed structure remain effective for TE and TM modes when illuminated by oblique incident waves up to 45°. Moreover, the proposed switchable absorber/reflector shows good temperature stability and can work under different liquid temperatures. Furthermore, the excellent performance of the proposed design is demonstrated by both simulated and experimental results, exhibiting great potential as transparent smart windows in large-scale ground-based stealth systems.

Design of a broadband multifunctional switchable absorber/reflector based on active frequency selective surfaces

“…Active absorbers based on FSS, which combine two different functions and can generally be switched primarily from the absorbing state to other states, are proposed to obtain dynamic characteristics. As of now, most scholars are working on three types of absorption switches: absorbers/reflectors [15][16][17][18][19][20][21], absorbers/ radiators [22], and absorbers/transmitters [23,24]. Among them, the switchable absorber/reflector integrating two opposite functions plays a vital role in military stealth, which can hide the object in a wide bandwidth to avoid detection by the enemy in the absorbing state and can declare itself by flashing periodically in the reflecting state.…”

“…In recent years, a considerable number of switchable absorber/reflector designs have already been reported [15][16][17][18][19][20][21]. A frequency reconfigurable metamaterial absorber/reflector with eight modes of operation has been proposed in the literature [15], which is based on a strategically arranged structure of three-dimensional feed network and load switching diodes to realize the switching of single-band, dual-band, and triple-band.…”

“…The absorber/reflector's wideband and switchable properties in complex electromagnetic environments make it a promising candidate for stealth systems. The broadband switchable absorbers/reflectors are developed in [17][18][19][20][21], making significant progress in broadband switching characteristics. Nonetheless, these functionalities are limited to specific polarization.…”

“…Still, it has only one set of feeder networks, the polarization is fixed once the structure is built. In [20], a transparent broadband absorber/reflector has been given to switch between absorption and reflection functions by controlling the injection and discharge of pure water, which is plagued by the same problem of adjustable polarization. Hence, the pursuit of creating a broadband and polarization-tunable switchable absorber/reflector still needs to be fulfilled.…”

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

“…Compared to traditional metamaterial absorbers, these water-based absorbers can achieve wider bandwidth and higher efficiency in terms of absorbing performance owing to the dispersive and lossy characteristics of water. Further, water-based designs with reconfigurable functions, which are more adaptable to the rapidly changing and increasingly complex EM environment, can be achieved based on the liquid fluidity [16], [17], [18], [19], [20]. In [16], a water-based tunable metamaterial is first designed and its tunability is realized by rotating the functional device, which reshapes the water inside the reservoir.…”