Hillenbrand R, Taubner T, Keilmann F
Max-Planck-Institut für Biochemie, Abteilung Molekulare Strukturbiologie, 82152 Martinsried, Germany.
Nature. 2002 Jul 11;418(6894):159-62. doi: 10.1038/nature00899.
Optical near fields exist close to any illuminated object. They account for interesting effects such as enhanced pinhole transmission or enhanced Raman scattering enabling single-molecule spectroscopy. Also, they enable high-resolution (below 10 nm) optical microscopy. The plasmon-enhanced near-field coupling between metallic nanostructures opens new ways of designing optical properties and of controlling light on the nanometre scale. Here we study the strong enhancement of optical near-field coupling in the infrared by lattice vibrations (phonons) of polar dielectrics. We combine infrared spectroscopy with a near-field microscope that provides a confined field to probe the local interaction with a SiC sample. The phonon resonance occurs at 920 cm(-1). Within 20 cm(-1) of the resonance, the near-field signal increases 200-fold; on resonance, the signal exceeds by 20 times the value obtained with a gold sample. We find that phonon-enhanced near-field coupling is extremely sensitive to chemical and structural composition of polar samples, permitting nanometre-scale analysis of semiconductors and minerals. The excellent physical and chemical stability of SiC in particular may allow the design of nanometre-scale optical circuits for high-temperature and high-power operation.
光学近场存在于任何被照亮的物体附近。它们会产生一些有趣的效应，比如增强针孔透射或增强拉曼散射，从而实现单分子光谱学。此外，它们还能实现高分辨率（低于10纳米）的光学显微镜成像。金属纳米结构之间的等离子体增强近场耦合为设计光学特性和在纳米尺度上控制光开辟了新途径。在此，我们研究了极性电介质的晶格振动（声子）对红外光光学近场耦合的强烈增强作用。我们将红外光谱学与一台近场显微镜相结合，该显微镜能提供一个受限场来探测与碳化硅样品的局部相互作用。声子共振发生在920厘米-1处。在共振频率的20厘米-1范围内，近场信号增加了200倍；在共振时，信号比用金样品获得的值高出20倍。我们发现，声子增强近场耦合对极性样品的化学和结构组成极其敏感，这使得对半导体和矿物进行纳米尺度分析成为可能。特别是碳化硅出色的物理和化学稳定性，可能有助于设计用于高温和高功率运行的纳米尺度光学电路。
