Abstract One of the most universal physical processes shared by all matter at finite temperature is the emission of thermal radiation. The experimental characterization and theoretical description of far-field black-body radiation was a cornerstone in the development of modern physics with the groundbreaking contributions from Gustav Kirchhoff and Max Planck. With its origin in thermally driven fluctuations of the charge carriers, thermal radiation reflects the resonant and non-resonant dielectric properties of media, which is the basis for far-field thermal emission spectroscopy. However, associated with the underlying fluctuating optical source polarization are fundamentally distinct spectral, spatial, resonant, and coherence properties of the evanescent thermal near-field. These properties have been recently predicted theoretically and characterized experimentally for systems with thermally excited molecular, surface plasmon polariton (SPP), and surface phonon polariton (SPhP) resonances. We review, starting with the early historical developments, the emergence of theoretical models, and the description of the thermal near-field based on the fluctuation–dissipation theory and in terms of the electromagnetic local density of states (EM-LDOS). We discuss the optical and spectroscopic characterization of distance dependence, magnitude, spectral distribution, and coherence of evanescent thermal fields. Scattering scanning near-field microscopy proved instrumental as an enabling technique for the investigations of several of these fundamental thermal near-field properties. We then discuss the role of thermal fields in nano-scale heat transfer and optical forces, and the correlation to the van der Waals, Casimir, and Casimir–Polder forces. We conclude with an outlook on the possibility of intrinsic and extrinsic resonant manipulation of optical forces, control of nano-scale radiative heat transfer with optical antennas and metamaterials, and the use of thermal infrared near-field spectroscopy (TINS) for broadband chemical nano-spectroscopic imaging, where the thermally driven vibrational optical dipoles provide their own intrinsic light source.

中文翻译：

---

热近场：相干性、光谱学、传热和光力

摘要 在有限温度下，所有物质共有的最普遍的物理过程之一是热辐射的发射。远场黑体辐射的实验表征和理论描述是现代物理学发展的基石，古斯塔夫·基尔霍夫 (Gustav Kirchhoff) 和马克斯·普朗克 (Max Planck) 做出了开创性贡献。由于其起源于电荷载流子的热驱动波动，热辐射反映了介质的共振和非共振介电特性，这是远场热发射光谱的基础。然而，与潜在波动的光源偏振相关的是渐逝热近场的根本不同的光谱、空间、共振和相干特性。这些特性最近已被理论预测并通过实验表征为具有热激发分子、表面等离子体极化子 (SPP) 和表面声子极化子 (SPhP) 共振的系统。我们回顾了早期历史发展、理论模型的出现以及基于波动耗散理论和电磁局部态密度 (EM-LDOS) 的热近场描述。我们讨论了渐逝热场的距离相关性、幅度、光谱分布和相干性的光学和光谱表征。散射扫描近场显微镜被证明是一种有助于研究这些基本热近场特性的技术。然后我们讨论了热场在纳米级传热和光学力中的作用，以及与范德华力、卡西米尔和卡西米尔-波尔德力的相关性。我们总结了对光学力的内在和外在共振操纵的可能性，用光学天线和超材料控制纳米级辐射热传递的可能性，以及使用热红外近场光谱 (TINS) 进行宽带化学纳米光谱成像，其中热驱动振动光学偶极子提供自己的本征光源。