2023-07-25 カリフォルニア工科大学(Caltech)
◆しかし、新しいデバイスは中程度の磁場内に置くことで、この法則を破ることが可能です。これにより、エネルギー収集システムや特定の迷彩の開発に重要な影響を与える可能性があります。デバイスは赤外線波長での吸収と放射を増強するパターン構造と磁場応答を持つ材料を組み合わせています。この成果は、物体のエネルギー変換効率向上に寄与する可能性があります。
＜関連情報＞
- https://www.caltech.edu/about/news/better-energy-harvesting-with-law-breaking-device
- https://www.nature.com/articles/s41566-023-01261-6
キルヒホッフの熱放射の法則の破れを直接観測 Direct observation of the violation of Kirchhoff’s law of thermal radiation
Komron J. Shayegan,Souvik Biswas,Bo Zhao,Shanhui Fan & Harry A. Atwater
Nature Photonics Published:24 July 2023
DOI:https://doi.org/10.1038/s41566-023-01261-6
Abstract
Thermal emission—the process through which all objects with a finite temperature radiate electromagnetic energy—has generally been thought to obey reciprocity, where the absorbed and emitted radiation from a body are equal for a given wavelength and angular channel. This equality, formalized by Gustav Kirchhoff in 1860, is known as Kirchhoff’s law of thermal radiation and has long guided designs to control the emitted radiation. Removing the constraint of Kirchhoff’s law unlocks a multitude of applications and designs for thermal emitters. Decoupling the absorptivity and emissivity relationship can be leveraged to achieve novel functions, ranging from reducing re-emission losses to the Sun in the context of solar energy harvesting systems to radiative camouflage. Here we report the direct measurements of an inequality between the spectral directional emissivity and absorptivity for a photonic design that supports a guided-mode resonance coupled to a magneto-optic material. This inequality occurs under the application of an in-plane magnetic field that modifies the normally diagonal permittivity tensor to a non-diagonal tensor in magneto-optic InAs, resulting in an antisymmetric relationship where the magnetic tuning of enhanced emissivity for a given angle correlates with decreased absorptivity for the same angle.
