Breaking Kirchhoff's Law in Nonlinear Thermal Emission
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arXiv
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| Auteurs principaux: | , , , , |
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| Format: | Preprint |
| Publié: |
2025
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| _version_ | 1866912422529335296 |
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| author | Ma, R. Yu, Y. Sun, Y. Yan, H. Wan, W. |
| author_facet | Ma, R. Yu, Y. Sun, Y. Yan, H. Wan, W. |
| contents | Thermal radiation is strictly governed by Kirchhoff s law to reach thermal equilibrium. The violation of Kirchhoff s law decouples nonreciprocally the equity between absorptivity and emissivity, enabling exotic thermal engineering applications. However, achieving broadband nonreciprocal thermal emissivity and absorptivity remains a challenge. Here we experimentally demonstrate nonreciprocal and broadband thermal radiation by breaking Kirchhoff s law through nonlinear optical frequency conversion in a scattering medium. Thermal blackbody radiation is upconverted through sum-frequency generation with an intense infrared pump, while broadband conversion is enabled by the critical random quasi-phase-matching condition in the nonlinear nanocrystals. Moreover, a temporal transient measurement also indicates a possible active radiation cooling through such nonlinear thermal radiation. These results may pave a new way for nonlinear and active thermal management in critical applications like radiation cooling, energy harvesting, and infrared camouflage. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_08544 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Breaking Kirchhoff's Law in Nonlinear Thermal Emission Ma, R. Yu, Y. Sun, Y. Yan, H. Wan, W. Optics Applied Physics Thermal radiation is strictly governed by Kirchhoff s law to reach thermal equilibrium. The violation of Kirchhoff s law decouples nonreciprocally the equity between absorptivity and emissivity, enabling exotic thermal engineering applications. However, achieving broadband nonreciprocal thermal emissivity and absorptivity remains a challenge. Here we experimentally demonstrate nonreciprocal and broadband thermal radiation by breaking Kirchhoff s law through nonlinear optical frequency conversion in a scattering medium. Thermal blackbody radiation is upconverted through sum-frequency generation with an intense infrared pump, while broadband conversion is enabled by the critical random quasi-phase-matching condition in the nonlinear nanocrystals. Moreover, a temporal transient measurement also indicates a possible active radiation cooling through such nonlinear thermal radiation. These results may pave a new way for nonlinear and active thermal management in critical applications like radiation cooling, energy harvesting, and infrared camouflage. |
| title | Breaking Kirchhoff's Law in Nonlinear Thermal Emission |
| topic | Optics Applied Physics |
| url | https://arxiv.org/abs/2506.08544 |