Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA.
Nano Lett. 2012 Mar 14;12(3):1475-81. doi: 10.1021/nl204201g. Epub 2012 Feb 8.
Despite the seminal contributions of Kirchhoff and Planck describing far-field thermal emission, fundamentally distinct spectral characteristics of the electromagnetic thermal near-field have been predicted. However, due to their evanescent nature their direct experimental characterization has remained elusive. Combining scattering scanning near-field optical microscopy with Fourier-transform spectroscopy using a heated atomic force microscope tip as both a local thermal source and scattering probe, we spectroscopically characterize the thermal near-field in the mid-infrared. We observe the spectrally distinct and orders of magnitude enhanced resonant spectral near-field energy density associated with vibrational, phonon, and phonon-polariton modes. We describe this behavior and the associated distinct on- and off-resonance nanoscale field localization with model calculations of the near-field electromagnetic local density of states. Our results provide a basis for intrinsic and extrinsic resonant manipulation of optical forces, control of nanoscale radiative heat transfer with optical antennas, and use of this new technique of thermal infrared near-field spectroscopy for broadband chemical nanospectroscopy.
尽管 Kirchhoff 和 Planck 对远场热发射做出了开创性的贡献，但电磁热近场的基本不同光谱特性已经被预测到了。然而，由于其瞬逝性质，它们的直接实验特征仍然难以捉摸。我们结合散射扫描近场光学显微镜和傅里叶变换光谱学，使用加热原子力显微镜探针作为局部热源和散射探针，对中红外热近场进行了光谱特征分析。我们观察到与振动、声子和声子极化激元模式相关的具有明显光谱特征和数量级增强的共振光谱近场能量密度。我们用近场电磁局部态密度的模型计算来描述这种行为以及相关的独特的共振和非共振纳米尺度场局域化。我们的结果为光学力的固有和外在共振操纵、使用光学天线控制纳米尺度的辐射热传递以及这种新的热红外近场光谱技术在宽带化学纳米光谱学中的应用提供了基础。
