磁环偶极子介导的核壳纳米粒子中的增益控制定向散射
Gain-controlled directional scattering in core-shell nanoparticles mediated by magnetic toroidal dipoles
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中文总结 AI 辅助
研究核壳纳米粒子中磁环偶极子介导的增益控制定向散射，利用洛伦兹 - 米氏理论，通过在介电芯引入光学增益，实现对近场和远场散射的控制，发现系统随增益变化的散射转变及相关特性，确定其为纳米系统定向散射的可调机制。
中文摘要 AI 辅助
环形偶极矩源于极向电流分布，形成一类具有独特近场特性的电磁激发。利用洛伦兹 - 米氏理论，我们表明核壳纳米粒子中传统磁偶极子与磁环偶极子之间的干涉产生法诺共振和明显的前后散射不对称性。通过在介电芯中引入光学增益，我们证明环形模式可以被选择性增强，从而实现对近场限制和远场散射方向性的控制。随着增益变化，系统经历从抑制后向散射到抑制前向散射的连续转变，通过主导磁偶极辐射的中间状态。这种偶极散射模式与磁环偶极子的相位共振和极向电流手性的反转有关。这些结果确定增益控制的环形激发是纳米尺度系统中定向散射的可调机制。
英文摘要
Toroidal dipole moments arise from poloidal current distributions and form a distinct class of electromagnetic excitations with unique near-field characteristics. Using Lorenz-Mie theory, we show that interference between conventional magnetic and magnetic toroidal dipoles in core-shell nanoparticles produces Fano resonances and pronounced forward-backward scattering asymmetry. By introducing optical gain in the dielectric core, we demonstrate that the toroidal mode can be selectively enhanced, enabling control of near-field confinement and far-field scattering directionality. As the gain varies, we find that the system undergoes a continuous transition from suppressed backscattering to suppressed forward scattering through an intermediate regime of dominant magnetic-dipole radiation. This dipolar scattering pattern is associated with a phase resonance of the magnetic toroidal dipole and a reversal of the poloidal current handedness. These results identify gain-controlled toroidal excitations as a tunable mechanism for directional scattering in nanoscale systems.
