Henriksson Nils, Gabbani Alessio, Petrucci Gaia, Garoli Denis, Pineider Francesco, Maccaferri Nicolò
Department of Physics, Umeå University, Linnaeus väg 24, 901 87 Umeå, Sweden.
Department of Chemistry and Industrial Chemistry, University of Pisa, via Moruzzi 13, 56124 Pisa, Italy.
ACS Appl Opt Mater. 2024 May 15;2(12):2469-2475. doi: 10.1021/acsaom.4c00098. eCollection 2024 Dec 27.
Multilayered metal-dielectric nanostructures display both a strong plasmonic behavior and hyperbolic optical dispersion. The latter is responsible for the appearance of two separated radiative and nonradiative channels in the extinction spectrum of these structures. This unique property can open plenty of opportunities toward the development of multifunctional systems that simultaneously can behave as optimal scatterers and absorbers at different wavelengths, an important feature to achieve multiscale control of light-matter interactions in different spectral regions for different types of applications, such as optical computing or detection of thermal radiation. Nevertheless, the temperature dependence of the optical properties of these multilayered systems has never been investigated. In this work, we study how radiative and nonradiative processes in hyperbolic meta-antennas can probe temperature changes of the surrounding medium. We show that, while radiative processes are essentially not affected by a change in the external temperature, the nonradiative ones are strongly affected by a temperature variation. By combining experiments and temperature-dependent effective medium theory, we find that this behavior is connected to enhanced damping effects due to electron-phonon scattering. Contrary to standard plasmonic systems, a red-shift of the nonradiative mode occurs for small variations of the environment temperature. Our study shows that, to probe temperature changes, it is essential to exploit nonradiative processes in systems supporting plasmonic excitations, which can be used as very sensitive thermometers via linear absorption spectroscopy.
多层金属-电介质纳米结构既表现出强烈的等离子体行为，又具有双曲线光学色散。后者导致这些结构的消光光谱中出现两个分离的辐射和非辐射通道。这种独特的性质为多功能系统的开发开辟了大量机会，这些系统在不同波长下可同时作为最佳散射体和吸收体，这是在不同光谱区域实现对不同类型应用（如光学计算或热辐射检测）中光与物质相互作用进行多尺度控制的一个重要特征。然而，这些多层系统光学性质的温度依赖性从未被研究过。在这项工作中，我们研究双曲线元天线中的辐射和非辐射过程如何探测周围介质的温度变化。我们表明，虽然辐射过程基本上不受外部温度变化的影响，但非辐射过程会受到温度变化的强烈影响。通过结合实验和温度相关的有效介质理论，我们发现这种行为与电子-声子散射导致的增强阻尼效应有关。与标准等离子体系统相反，环境温度的微小变化会导致非辐射模式发生红移。我们的研究表明，为了探测温度变化，利用支持等离子体激发的系统中的非辐射过程至关重要，这些过程可通过线性吸收光谱用作非常灵敏的温度计。
