Grupo de Óptica, Departamento de Física Aplicada, Universidad de Cantabria, Santander, Spain.
Langmuir. 2013 Jun 4;29(22):6715-21. doi: 10.1021/la400703r. Epub 2013 May 22.
The angular spectrum representation of electromagnetic fields scattered by metallic particles much smaller than the incident wavelength is used to interpret and analyze the spectral response of localized surface plasmon resonances (LSPs) both in the near-field and far-zone regimes. The previously observed spectral redshift and broadening of the LSP peak, as one moves from the far-zone to the near-field region of the scatterer, is analyzed on studying the role and contribution of the evanescent and propagating plane wave components of the emitted field. For such dipolar particles, it is found that the evanescent waves are responsible for those broadenings and shifts. Further, we prove that the shift is a universal phenomenon, and hence, it constitutes a general law, its value increasing as the imaginary part of the nanostructure permittivity grows. Our results should be of use for the prediction and interpretation of the spectral behavior in applications where the excitation of LSPs yield field enhancements like those assisting surface-enhanced Raman spectroscopy or equivalent processes.
利用电磁场在金属粒子上散射的角谱表示，来解释和分析局域表面等离子体共振（LSP）在近场和远场区域的光谱响应。通过研究发射场的消逝波和平行波分量的作用和贡献，分析了从远场到散射体近场区域时 LSP 峰值的光谱红移和展宽。对于这种偶极子粒子，我们发现消逝波是导致展宽和位移的原因。此外，我们证明了这种位移是一种普遍现象，因此构成了一条普遍规律，其值随着纳米结构介电常数的虚部增加而增加。我们的研究结果应该有助于预测和解释那些激发 LSP 产生场增强的应用中的光谱行为，例如表面增强拉曼光谱或等效过程。
