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Updated: Jul 12, 2025
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Simulation, Fabrication and Characterization of THz Metamaterial Absorbers
Published on: December 27, 2012
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Extinction and attenuation by voids in absorbing host media
Optics Express
|October 20, 2023
Summary
This study clarifies extinction definitions for particles in absorbing materials. It reveals host absorption significantly impacts void extinction, enabling negative extinction cross-sections and better understanding of radiative transfer.
Area of Science:
- Optics and Photonics
- Materials Science
- Electromagnetism
Background:
- Controversy exists regarding extinction and attenuation by particles in absorbing hosts, hindering radiative transfer understanding in composite materials.
- Existing extinction definitions (equivalence theorem, near-field analytical, operational) have limitations, particularly concerning host absorption and far-field effects.
Purpose of the Study:
- To outline and compare existing extinction definitions for particles in absorbing media.
- To investigate the influence of host absorption on void extinction using a generalized operational definition.
- To provide a clearer understanding of radiative transfer in composite materials with voids.
Main Methods:
- Review and analysis of existing extinction definitions, including an equivalence theorem, near-field analytical definition, and operational definition.
- Application of the independent scattering approximation and rigorous multiple scattering theory.
- Utilizing the Maxwell-Garnett effective medium theory to calculate attenuation coefficients for void-containing materials (SiC, Ag).
Main Results:
- The generalized operational definition of extinction is shown to be equivalent to effective medium methods under specific approximations.
- Host absorption significantly influences void extinction, leading to positive, zero, or even negative extinction cross-sections at void resonance.
- The equivalence theorem and near-field definition fail to capture void resonance structures and negative extinction in absorbing media.
Conclusions:
- The generalized operational extinction definition accurately accounts for host absorption effects, resolving previous limitations.
- Negative extinction cross-sections, indicating reduced total absorption, are possible and quantitatively controlled by host absorption.
- The findings enhance the understanding of complex scattering phenomena and radiative transfer in absorbing composite materials.
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