Visible–Infrared Transparent Ultra-Thin Frequency-Tunable Microwave Absorber Based on a Nanometer-Thick Patterned VO₂ Film

Abstract

Designing an ultra-thin microwave absorber that can simultaneously realize tunable absorption and broadband optical transparency remains a crucial challenge. In this work, we present a visible−infrared transparent ultrathin frequency-tunable microwave absorber based on a nanometer-thick patterned vanadium dioxide (VO 2 ) film. The thermally variable sheet resistance of the nanometer-thick VO 2 film enables different percentages of equivalent resistance in the equivalent impedance of the patterned VO 2 film, which induces the absorbing mode to transform from pure Fabry−Perot (FP) cavity resonant to FP cavity and LC electrical co-resonant. The measured thermally peak absorption frequency modulation range is 15.42−12.99 GHz, while the ultrathin thickness is only 0.071 of the central wavelength of this range. Moreover, the absorber can achieve high optical transparency from 380 to 6000 nm. Therefore, the proposed absorber has diverse applications in optics and modern intelligent platforms.

Design of an ultra-wideband and switchable VO2-based microwave absorber

“…Compared with the reported MMA in [58], the our structure shows a narrower RBW, but it offers the switching capability. Compared with the similar switchable design using VO 2 in [42,59], this work achieves a higher RBW with an incident angle stability while the design of MMA using lumped resistors such as VO 2 chip is usually difficult to achieve the incident angle stability up to 60°, which may be considered as effectively of the proposed design. In addition, our design can control its operation bandwidth to be suitable for specific applications by scaling its dimensions.…”

Tunable Microwave Absorbing Devices Enabled by Reversible Metal Electrodeposition

“…Hence, there has been a broader scope of research based on active elements, including lumped elements, 15−17 2D materials (such as graphene 18−20 and black phosphorus 21,22 ), liquid crystals, 23,24 ferrite materials, 25,26 and phase-change materials. 27,28 These active elements have the capability to modify their electromagnetic properties in response to external stimuli such as electric, 17,19 magnetic, 25 light, 4,29 or heat, 28 thus enabling dynamic control of microwaves. Voltage stimulation is regarded as a promising external stimulus due to its flexibility, practicality, and low energy usage.…”

“…While it is feasible to achieve tuning of microwave absorbing properties based on architectural changes, such as manipulating fluids like liquid metal , and water , in microfluidic systems or changing shapes using shape-memory materials , and origami, − the former necessitates additional pneumatic or storage apparatus, and the latter exhibits limited flexibility in mechanical tuning. Hence, there has been a broader scope of research based on active elements, including lumped elements, − 2D materials (such as graphene − and black phosphorus , ), liquid crystals, , ferrite materials, , and phase-change materials. , These active elements have the capability to modify their electromagnetic properties in response to external stimuli such as electric, , magnetic, light, , or heat, thus enabling dynamic control of microwaves. Voltage stimulation is regarded as a promising external stimulus due to its flexibility, practicality, and low energy usage .…”