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1. Role of Dielectric Loss in Microwave Absorber Design

   https://doi.org/10.1109/SoutheastCon48659.2022.9764067  

   Saha, Arun K.; Pendleton, Walker G. (May 2022, IEEE Southeastcon 2022)

   A theoretical analysis is conducted to understand the role of dielectric loss component in the design process of a microwave absorber. The analysis starts with the determination of input impedance of the absorber and equating this to free space impedance in order to develop the impedance matching equation. The result of analysis showed that absorbing material must have some amount of loss component for impedance matching at a certain frequency and for perfect impedance matching a specific value of loss factor is required along with specific value of dielectric constant and material thickness. 

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2. Broadband and Tunable Microwave Absorption Properties from Large Magnetic Loss in Ni–Zn Ferrite

   https://doi.org/10.1002/admt.202301857  

   Ghosh, Subrata; Sharma, Shweta; Li, Wenjie; Nozariasbmarz, Amin; Raman, Lavanya; Liu, Na; Goyal, Gagan K.; Zhang, Yu; Perini, Steven E.; Lanagan, Michael; et al (January 2024, Advanced Materials Technologies)

   Abstract Highly effective electromagnetic (EM) wave absorber materials with strong reflection loss (RL) and a wide absorption bandwidth (EBW) in gigahertz (GHz) frequencies are crucial for advanced wireless applications and portable electronics. Traditional microwave absorbers lack magnetic loss and struggle with impedance matching, while ferrites are stable, exhibit excellent magnetic and dielectric losses, and offer better impedance matching. However, achieving the desired EBW in ferrites remains a challenge, necessitating further composition design. In this study, impedance matching is successfully enhanced and EBW in Ni–Zn ferrite is broadened by successive doping with Mn and Co , without incorporation of any polymer filler. It is found that Ni_0.4Co_0.1Zn_0.5Fe_1.9Mn_0.1O₄material exhibits exceptional EM wave absorption, with a maximum RL of −48.7 dB. It also featured a significant EBW of 10.8 GHz, maintaining a 90% absorption rate (RL < −10 dB) for a thickness of 4.5 mm. These outstanding properties result from substantial magnetic losses and favorable impedance matching. These findings represent a significant step forward in the development of microwave absorber materials, addressing EM wave pollution concerns within GHz frequencies, including the frequency band used in popular 5G technology. 

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3. Microwave Absorption of Organic Metal Halide Nanotubes

   https://doi.org/10.1002/admi.201901270  

   Lin, Haoran; Green, Michael; Xu, Liang‐Jin; Chen, Xiaobo; Ma, Biwu (December 2019, Advanced Materials Interfaces)

   Abstract Organic metal halide hybrids have attracted tremendous research interests owing to their outstanding optical and electronic properties suitable for various applications, including photovoltaics, light‐emitting diodes, and photodetectors. Recently, the multifunctionality of this class of materials has been further explored beyond their optical and electronic properties. Here, for the first time the microwave electromagnetic properties of a 1D organic metal halide hybrid, (C₆H₁₃N₄)₃Pb₂Br₇, a single crystalline bulk assembly of organic metal halide nanotubes, are reported. Good microwave absorption performance with a large reflection loss value of −18.5 dB and a threshold bandwidth of 1.0 GHz is discovered for this material, suggesting its potential as a new microwave absorber. This work reveals a new functionality of organic metal halide hybrids and provides a new material class for microwave absorption application studies. 

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4. Inverse designed aperiodic multilayer perfect absorbers for mid infrared enable tunability switchability and angular robustness

   https://doi.org/10.1038/s41598-025-99995-6  

   Nazari, Masoumeh; Banad, Yaser M; Sharif, Sarah (December 2025, Scientific Reports)

   We present a class of inverse-designed, aperiodic multilayer graphene-based perfect absorbers operating in the mid-infrared spectrum (3–5 μm), a range vital for atmospheric transparency and advanced sensing. Our design leverages a fixed material sequence—graphene, PPSU dielectric spacers, and PbSe layers on a gold substrate—while achieving precise spectral tunability solely through layer thickness variation, enabling absorption peak control in 0.25 μm steps without any change in material composition. This physical tunability allows scalable fabrication of wavelength-specific devices using a single manufacturing process. We further demonstrate electrical switchability by dynamically modulating graphene’s chemical potential (µc from 0 eV to 1 eV), enabling absorption amplitude control and wavelength redshifting without structural alteration. The proposed absorber achieves > 99.9% efficiency using only five graphene layers in a compact ~ 2 μm stack, offering significant advantages in size, weight, power, and cost. Our hybrid micro-genetic inverse design algorithm enables this performance while preserving > 90% absorption at incidence angles up to 52°, supporting broad angular robustness. Extensive simulation and field distribution analyses confirm the role of plasmonic confinement and impedance matching. Additionally, we validate the design’s fabrication tolerance and benchmark its performance against recent state-of-the-art absorbers. By combining advanced inverse design with nanophotonic structures, our work advances the field of mid-infrared absorbers, providing a scalable and efficient platform for next-generation optical devices. 

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5. Bioinspired Fano-like resonant transmission: frequency selective impedance matching

   https://doi.org/10.1088/1361-6463/ad1c86  

   Esposito, Gennaro_Andrea; Tallarico, Domenico; Sayed_Ahmed, Moustafa; Miniaci, Marco; Shahab, Shima; Bergamini, Andrea (January 2024, Journal of Physics D: Applied Physics)

   Abstract The study of the impedance mismatch between the device and its surroundings is crucial when building an acoustic device to obtain optimal performance. In reality, a high impedance mismatch would prohibit energy from being transmitted over the interface, limiting the amount of energy that the device could treat. In general, this is solved by using acoustic impedance matching layers, such as gradients, similar to what is done in optical coatings. The simplest form of such a gradient can be considered as an intermediate layer with certain qualities resting between the two media to impedance match, and requiring a minimum thickness of at least one quarter wavelength of the lowest frequency under consideration. The desired combination(s) of the (limited) available elastic characteristics and densities has traditionally determined material selection. Nature, which is likewise limited by the use of a limited number of materials in the construction of biological structures, demonstrates a distinct approach in which the design space is swept by modifying certain geometrical and/or material parameters. The middle ear of mammals and the lateral line of fishes are both instances of this method, with the latter already incorporating an architecture of distributed impedance matched underwater layers. In this paper, we develop a resonant mechanism whose properties can be modified to give impedance matching at different frequencies by adjusting a small set of geometrical parameters. The mechanism in question, like the lateral line organ, is intended to serve as the foundation for the creation of an impedance matching meta-surface. A computational study and parameter optimization show that it can match the impedance of water and air in a deeply sub-wavelength zone. 

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