Azimuthally polarized beams are gaining fundamental importance for near-field force microscopy systems to inspect photoinduced magnetism in special molecules or nanostructures, due to their strong axial magnetic field and vanishing electric field. The magnetic dominant region represents a unique trait of such a beam as a potentially ideal structured light to probe photoinduced magnetism at the nanoscale. Therefore, we present a near-field characterization of an optical, sharply focused azimuthally polarized beam using photoinduced force microscopy, a technique with simultaneous near-field excitation and detection, achieving nanoscale resolution well beyond the diffraction limit. Such a method exploits the photoinduced gradient force on a nanotip, mechanically detected as forced oscillations of the cantilever in an atomic force microscopy system upon external light illumination. The photoinduced force is strongly localized, which that depends only on the near-field signal free from background scattering photons, granting photoinduced force microscopy a superior performance over its precedent near-field scanning optical microscopy. We develop an analytical model to correct the tip-induced measurement anisotropy, suppress the background noise, and reveal the local electric field distribution of the azimuthally polarized beam. These measurements are used to retrieve its strong longitudinal axial magnetic field at the center of the polarization vortex where the electric field vanishes. This study can lead to a plethora of possibilities in optomechanical, chemical, or biomedical applications. We also propose and discuss how to use such beams with polarization azimuthal symmetry as a way to calibrate microscope nanotips.

中文翻译：

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具有磁优势的聚焦聚焦方位角偏振光束：通过光致力显微镜在纳米尺度上进行近场表征

方位角偏振光束由于其强大的轴向磁场和消失的电场，对于检查特殊分子或纳米结构中的光致磁性在近场力显微镜系统中变得越来越重要。磁性支配区域表示这种光束的独特特征，它是潜在理想的结构化光，可探测纳米级的光致磁性。因此，我们提出了一种利用光致力显微镜对光学的，锐利聚焦的方位偏振光束进行近场表征的技术，该技术具有同时进行近场激发和检测的技术，可实现远远超出衍射极限的纳米级分辨率。这种方法利用了纳米尖端上的光诱导梯度力，在外部光照射下，在原子力显微镜系统中被机械检测为悬臂的强制振荡。光诱导的力被强烈地定位，这仅取决于没有背景散射光子的近场信号，从而使光诱导的力显微镜具有比其先前的近场扫描光学显微镜更高的性能。我们建立了一个解析模型来校正尖端引起的测量各向异性，抑制背景噪声，并揭示方位极化光束的局部电场分布。这些测量用于在电场消失的极化涡旋中心恢复其强大的纵向轴向磁场。这项研究可以在光机械，化学或生物医学应用中带来大量可能性。