The resonant optical excitation of dielectric nanostructures offers unique opportunities for developing remarkable nanophotonic devices. Light that is structured by tailoring the vectorial characteristics of the light beam provides an additional degree of freedom in achieving flexible control of multipolar resonances at the nanoscale. Here, we investigate the nonlinear scattering of subwavelength silicon (Si) nanostructures with radially and azimuthally polarized cylindrical vector beams to show a strong dependence of the photothermal nonlinearity on the polarization state of the applied light. The resonant magnetic dipole, selectively excited by an azimuthally polarized beam, enables enhanced photothermal nonlinearity, thereby inducing large scattering saturation. In contrast, radially polarized beam illumination shows no observable nonlinearity owing to off-resonance excitation. Numerical analysis reveals a difference of more than 2 orders of magnitude in photothermal nonlinearity under two types of polarization excitations. Nonlinear scattering and the unique doughnut-shaped focal spot generated by the azimuthally polarized beam are demonstrated as enabling far-field high-resolution localization of nanostructured Si with an accuracy approaching 50 nm. Our study extends the horizons of active Si photonics and holds great potential for label-free superresolution imaging of Si nanostructures.

中文翻译：

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圆柱矢量光束揭示硅纳米结构超定域化的多极非线性散射

介电纳米结构的共振光激发为开发卓越的纳米光子器件提供了独特的机会。通过定制光束的矢量特性来构建的光在实现纳米级多极共振的灵活控制方面提供了额外的自由度。在这里，我们研究了具有径向和方位角偏振圆柱矢量光束的亚波长硅 (Si) 纳米结构的非线性散射，以显示光热非线性对应用光偏振态的强烈依赖性。共振磁偶极子由方位极化光束选择性激发，可增强光热非线性，从而引起大的散射饱和。相比之下，由于偏共振激发，径向偏振光束照明没有显示出可观察到的非线性。数值分析表明，在两种偏振激发下，光热非线性存在超过 2 个数量级的差异。非线性散射和由方位偏振光束产生的独特的甜甜圈形焦斑被证明可以实现纳米结构 Si 的远场高分辨率定位，精度接近 50 nm。我们的研究扩展了有源硅光子学的视野，并在硅纳米结构的无标记超分辨率成像方面具有巨大潜力。非线性散射和由方位偏振光束产生的独特的甜甜圈形焦斑被证明能够以接近 50 nm 的精度实现纳米结构 Si 的远场高分辨率定位。我们的研究扩展了有源硅光子学的视野，并在硅纳米结构的无标记超分辨率成像方面具有巨大潜力。非线性散射和由方位偏振光束产生的独特的甜甜圈形焦斑被证明可以实现纳米结构 Si 的远场高分辨率定位，精度接近 50 nm。我们的研究扩展了有源硅光子学的视野，并在硅纳米结构的无标记超分辨率成像方面具有巨大潜力。