Transparent Perfect Microwave Absorber Employing Asymmetric Resonance Cavity

Abstract

The demand for high‐performance absorbers in the microwave frequencies, which can reduce undesirable radiation that interferes with electronic system operation, has attracted increasing interest in recent years. However, most devices implemented so far are opaque, limiting their use in optical applications that require high visible transparency. Here, a scheme is demonstrated for microwave absorbers featuring high transparency in the visible range, near‐unity absorption (≈99.5% absorption at 13.75 GHz with 3.6 GHz effective bandwidth) in the Ku‐band, and hence excellent electromagnetic interference shielding performance (≈26 dB). The device is based on an asymmetric Fabry–Pérot cavity, which incorporates a monolayer graphene and a transparent ultrathin (8 nm) doped silver layer as absorber and reflector, and fused silica as the middle dielectric layer. Guided by derived formulism, this asymmetric cavity is demonstrated with microwaves near‐perfectly and exclusively absorbs in the ultrathin graphene film. The peak absorption frequency of the cavity can be readily tuned by simply changing the thickness of the dielectric spacer. The approach provides a viable solution for a new type of microwave absorber with high visible transmittance, paving the way towards applications in the area of optics.

Design of an Optical Transparent Absorber and Defect Diagnostics Analysis Based on Near-Field Measurement

“…To observe only the signal completely reflected by the surface, a copper sheet was attached to the back of the transparent absorbing structure and was measured. Figure 7 shows the reflected power result (P re f lec = |Γ 3 | 2 × 100%) obtained from Equation (7). The measurement results confirmed a difference of up to 1.46 dB for the reflection coefficient and up to 4.68% for the X-band average reflectance.…”

Ultra-light MXene aerogel/wood-derived porous carbon composites with wall-like “mortar/brick” structures for electromagnetic interference shielding

“…This is because increasing the carbonization temperature greatly increases the r of WPC, which increases the impedance mismatch between the materials and air, causing most of the incident electromagnetic waves to be reflected. In addition, during the multiple reflection and scattering process of the electromagnetic waves entering the materials, highly conductive WPC has a stronger dielectric loss mechanism, which makes them fully captured and attenuated, resulting in the excellent EMI shielding performance [39,40].…”

Thin‐Metal‐Film‐Based Transparent Conductors: Material Preparation, Optical Design, and Device Applications

“…Toward this goal, various designs have been exploited, including carbon‐based materials, [ 310–312 ] metal meshes and nanowires, [ 313–315 ] and thin metal films. [ 92,202,316 ] Compared to other candidates, thin metal films exhibit unique advantages of simple structure and large‐scale manufacturing compatibility, and therefore, have been gaining increased attention in recent years. For example, Maniyara et al.…”

“…By adding a monolayer graphene on the backside of the substrate, they were able to further increase the structure's RF absorption without scarifying much of its visible transparency. [ 316 ]…”