High-performance broadband electromagnetic interference shielding optical window based on a metamaterial absorber

Abstract

An excellently transparent metamaterial-based electromagnetic interference (EMI) shielding window with broadband absorption is presented theoretically and demonstrated experimentally. The window is composed of double split circular ring (SCR) elements whose absorption spectra feature two mild resonant peaks. Indium–tin–oxide (ITO) with resonant patterns is utilized as the material to induce high ohmic loss and broaden the absorption bandwidth. The window achieves strong absorptivity, > 90%, covering an ultrawide frequency range of 7.8–18.0 GHz. Moreover, the measured shielding effectiveness (SE) of the window is > 18.25 dB, at 7.0–18.0 GHz, while the average optical transmittance is fixed at ∼73.10% in the visible–near-infrared (Vis–NIR) region of 400–1,500 nm. Further, the absorption mechanism is revealed by designing an equivalent circuit model and studying the distributions of the electric field and surface currents of the structure. Furthermore, a specific design feature also makes our device insensitive to the incident angle and the polarization state of the impinging microwave. The 90% absorption and shielding performance of the proposed optical window avail it for a wide range of great potential applications, such as the displays of military and medical precision devices.

Multifunctional Green Electromagnetic Interference Shielding Material for the Sub-6-GHz Band

“…The middle dielectric substrate layer can be equivalent to a lossless transmission line, and the backplane layer can be regarded as a shorted circuit. According to transmission line theory, the equivalent impedance of a lossless transmission line can be calculated by Z l o s s l e s s = j Z t tan false( β t false) μ r / ε r tan false( β t false) where j is the imaginary unit. The lossless DCL can be regarded as a pure inductance.…”

“…Conveniently, the circuit in the black dotted box in Figure a is simplified to an RLC series circuit in Figure b. The overall input impedance of the multifunction structure can be calculated, based on the transmission line theory as , 1 / Z i n = 1 / Z a + 1 / Z b …”

Paper-based flexible metamaterial for microwave applications

“…In recent years, the electromagnetic pollution arose from the widely used wireless communication facilities has stimulated the development of electromagnetic interference shielding materials [108,109]. Much efforts have been made to achieve high shielding effectiveness with paper- based metamaterials.…”

Ultrathin optically transparent electromagnetic shielding window with broadband microwave absorption and ultrahigh optical transmittance

“…Reference 34 reported an OTMMA with absorptivity higher than 90% in the range of 0.9 to 1 GHz, and a mechanically flexible and optically transparent millimeter‐wave broadband absorber with more than 90% absorption covering 73.5 ~ 110 GHz was proposed by Lai et al 35 In reference 36, a polarization‐sensitive, flexible, and broadband OTMMA based on ITO films was demonstrated. Moreover, an angle‐sensitive OTMMA based on ITO films was proposed with absorptivity of >80% when the incident angle is less than 30° 37 . The aforementioned OTMMAs exhibited high efficiency and broadband microwave absorption but the light transmittance is not high because they usually use a continuous ITO film as the back layer and an ITO film with a large duty cycle pattern as the resonant layer.…”

“…Moreover, an angle-sensitive OTMMA based on ITO films was proposed with absorptivity of >80% when the incident angle is less than 30 . 37 The aforementioned OTMMAs exhibited high efficiency and broadband microwave absorption but the light transmittance is not high because they usually use a continuous ITO film as the back layer and an ITO film with a large duty cycle pattern as the resonant layer. Another example is that Zhang et al 38 proposed an OTMMA-based EMI shielding window with an SE of 18.25 dB but only 73.10% light transmittance.…”