近日，美国加州理工学院的Harry A. Atwater及其研究小组与加州大学的Aaswath P. Raman等人合作并取得一项新进展。经过不懈努力，他们对宽带非互易热发射率和吸收率进行研究。相关研究成果已于2024年7月24日在国际知名学术期刊《光：科学与应用》上发表。

在这项工作中，研究人员通过测量具有亚波长厚度(50nm和150nm)的梯度epsilon-接近零InAs层的热发射率和吸收率，证明了宽带非互易热发射率和吸收率。该效应发生在与红外透明窗口重叠的12.5 ~ 16μm光谱范围内，并在中等(1T)磁场下观察到。

据悉，违背基尔霍夫热辐射定律的物体，其光谱方向吸收率和发射率不相等。实现这一不等式不仅是基础科学研究的重要兴趣所在，也是推动光子能量转换与辐射冷却技术达到热力学极限的先决条件。截至目前，光谱定向发射率与吸收率的不一致性主要局限于狭窄的光谱共振区域，或是远红外波段以外的长波长范围。为了跨越从基础原理展示到实际技术应用的鸿沟，关键在于实现对宽光谱范围内不均匀光谱定向吸收率与发射率的控制。

附：英文原文

Title: Broadband nonreciprocal thermal emissivity and absorptivity

Author: Shayegan, Komron J., Hwang, Jae S., Zhao, Bo, Raman, Aaswath P., Atwater, Harry A.

Issue&Volume: 2024-07-24

Abstract: A body that violates Kirchhoff’s law of thermal radiation exhibits an inequality in its spectral directional absorptivity and emissivity. Achieving such an inequality is of fundamental interest as well as a prerequisite for achieving thermodynamic limits in photonic energy conversion and radiative cooling. Thus far, inequalities in the spectral directional emissivity and absorptivity have been limited to narrow spectral resonances, or wavelengths well beyond the infrared regime. Bridging the gap from basic demonstrations to practical applications requires control over a broad spectral range of the unequal spectral directional absorptivity and emissivity. In this work, we demonstrate broadband nonreciprocal thermal emissivity and absorptivity by measuring the thermal emissivity and absorptivity of gradient epsilon-near-zero InAs layers of subwavelength thicknesses (50nm and 150nm) with an external magnetic field. The effect occurs in a spectral range (12.5–16μm) that overlaps with the infrared transparency window and is observed at moderate (1T) magnetic fields.

DOI: 10.1038/s41377-024-01520-3

Source: https://www.nature.com/articles/s41377-024-01520-3