论文标题
热发射的宽带定向控制
Broadband directional control of thermal emission
论文作者
论文摘要
控制发射远场热辐射的方向性是当代光子学和材料研究中的一个基本挑战。尽管光子策略使热发射对狭窄的带宽组的角度选择性具有固有的宽带现象。目前,我们缺乏将发射热辐射限制为在宽带宽上任意角范围的能力。在这里,我们介绍并实验实现了梯度Epsilon-near-Zero(ENZ)材料结构,通过支持漏水的电磁模式,这些模式可以在宽阔的带宽上以固定角度自由空间,从而实现了热发射的广泛方向控制。我们演示了两个发射极结构,这些发射极结构由光子构型中的多个半导体氧化物组成,可在长波红外波长上实现梯度ENZ行为。在70度-85摄氏度的角度范围内,在70度-85度的角度范围内,P极化在70和11.5微米之间表现出很高的平均发射率(大于0.6和0.7),在60 deg -75 ver的角度范围内和10.0至14.3微米之间。在这些角范围之外,在50度和40度时,发射率急剧下降到0.4。结构宽带热束功能仅能以特定角度才能强大的辐射传热,并通过直接测量热发射进行实验验证。通过将角度和光谱响应的常规限制解耦,我们的方法为诸如热伪装,太阳能加热,辐射冷却和废热恢复等应用中的辐射传热带来了新的可能性。
Controlling the directionality of emitted far-field thermal radiation is a fundamental challenge in contemporary photonics and materials research. While photonic strategies have enabled angular selectivity of thermal emission over narrow sets of bandwidths, thermal radiation is inherently a broadband phenomenon. We currently lack the ability to constrain emitted thermal radiation to arbitrary angular ranges over broad bandwidths. Here, we introduce and experimentally realize gradient epsilon-near-zero (ENZ) material structures that enable broad spectrum directional control of thermal emission by supporting leaky electromagnetic modes that couple to free space at fixed angles over a broad bandwidth. We demonstrate two emitter structures consisting of multiple semiconductor oxides in a photonic configuration that enable gradient ENZ behavior over long-wave infrared wavelengths. The structures exhibit high average emissivity (greater than 0.6 and 0.7) in the p polarization between 7.7 and 11.5 micron over an angular range of 70 deg - 85 deg, and between 10.0 to 14.3 micron over an angular range of 60 deg-75 deg, respectively. Outside these angular ranges, the emissivity dramatically drops to 0.4 at 50 deg and 40 deg. The structures broadband thermal beaming capability enables strong radiative heat transfer only at particular angles and is experimentally verified through direct measurements of thermal emission. By decoupling conventional limitations on angular and spectral response, our approach opens new possibilities for radiative heat transfer in applications such as thermal camouflaging, solar heating, radiative cooling and waste heat recovery.