Picardi Michela F, Zayats Anatoly V, Rodríguez-Fortuño Francisco J
Department of Physics, King's College London, Strand, London, WC2R 2LS, United Kingdom.
Phys Rev Lett. 2018 Mar 16;120(11):117402. doi: 10.1103/PhysRevLett.120.117402.
Unidirectional scattering from circularly polarized dipoles has been demonstrated in near-field optics, where the quantum spin-Hall effect of light translates into spin-momentum locking. By considering the whole electromagnetic field, instead of its spin component alone, near-field directionality can be achieved beyond spin-momentum locking. This unveils the existence of the Janus dipole, with side-dependent topologically protected coupling to waveguides, and reveals the near-field directionality of Huygens dipoles, generalizing Kerker's condition. Circular dipoles, together with Huygens and Janus sources, form the complete set of all possible directional dipolar sources in the far- and near-field. This allows the designing of directional emission, scattering, and waveguiding, fundamental for quantum optical technology, integrated nanophotonics, and new metasurface designs.
圆偏振偶极子的单向散射已在近场光学中得到证实，其中光的量子自旋霍尔效应转化为自旋动量锁定。通过考虑整个电磁场，而不仅仅是其自旋分量，可以实现超越自旋动量锁定的近场方向性。这揭示了两面神偶极子的存在，其与波导的耦合具有侧面依赖性且受拓扑保护，并揭示了惠更斯偶极子的近场方向性，推广了克尔条件。圆形偶极子与惠更斯源和两面神源一起，构成了远场和近场中所有可能的定向偶极源的完整集合。这使得能够设计出定向发射、散射和波导，这对于量子光学技术、集成纳米光子学和新型超表面设计至关重要。
