Département d'Optique P.M. Duffieux, Institut FEMTO-ST, CNRS UMR 6174, Université de Franche-Comté,16 Route de Gray, 25030 Besançon Cedex, France.
Opt Lett. 2010 Feb 1;35(3):357-9. doi: 10.1364/OL.35.000357.
Despite their modest spatial resolution, uncoated tapered fiber probes are now widely used by the nano-optics community for mapping, with scanning near-field optical microscopy (SNOM), the nonradiative fields at the surface of optical and plasmonic microstructures and nanostructures. Given the significant complexity of the vectorial optical phenomena associated with subwavelength structures, the correct interpretation of SNOM acquisitions requires a complete and accurate understanding of the intrinsic image-formation procedure. In this theoretical study, we show that the SNOM imaging process with uncoated tapered fiber probes is highly polarization dependent and that the dominant effect is, surprisingly, the choice of optical fiber from which the tapered probe was fabricated. We demonstrate that although a tapered monomode fiber is unable to collect the component of the vector electric field parallel to the tip axis, a tapered multimode fiber can successfully collect all the three field components. However, we show that the signal from the longitudinal field component is collected only 10% as efficiently as the signal from the two transverse field components.
尽管无涂层锥形光纤探头的空间分辨率有限，但纳米光学领域现在广泛使用它们通过扫描近场光学显微镜（SNOM）来绘制光学和等离子体微结构和纳米结构表面的非辐射场。鉴于与亚波长结构相关的矢量光学现象非常复杂，正确解释 SNOM 采集结果需要完全准确地了解内在的成像过程。在这项理论研究中，我们表明，带有无涂层锥形光纤探头的 SNOM 成像过程高度依赖于偏振，并且令人惊讶的是，主要影响因素是用于制造锥形探头的光纤的选择。我们证明，尽管锥形单模光纤无法收集与尖端轴平行的矢量电场分量，但锥形多模光纤可以成功收集所有三个场分量。然而，我们表明，纵向场分量的信号仅能以与两个横向场分量相同的效率收集 10%。
