Near-Field Directionality Beyond the Dipole Approximation: Electric Quadrupole and Higher-Order Multipole Angular Spectra

Abstract

Within the context of spin-related optical phenomena, the near-field directionality is generally understood from the quantum spin Hall effect of light, according to which the transverse spin of surface or guided modes is locked to the propagation direction. So far, most previous works have been focused on the spin properties of circularly polarized dipolar sources. However, in near-field optics, higher-order multipole sources (e.g., quadrupole, octupole, and so on) might become relevant, so a more in-depth formulation would be highly valuable. Building on the angular spectrum representation, we provide a general, analytical, and ready-to-use treatment in order to address the near-field directionality of any multipole field, particularizing to the electric quadrupole case. Besides underpinning and upgrading the current framework on spin-dependent directionality, our results may open up new perspectives for engineering light-matter coupling at the nanoscale.

arXiv comment7 pages, 2 figures. Supplemental Material (19 pages). Supplemental tools (calculator of angular spectra and animation) available at https://doi.org/10.5281/zenodo.2677908

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Cited by in corpus (7)

• Experimental Realization of Near-Field Photonic Routing with All-Electric Metasources
• Momentum-space geometric structure of helical evanescent waves and its implications on near-field directionality
• A non-singular, field-only surface integral method for interactions between electric and magnetic dipoles and nano-structures
• Optical isolation induced by subwavelength spinning particle via spin-orbit interaction
• Directional coupling of emitters into waveguides: A symmetry perspective
• The dependence of evanescent wave polarization on the losses of guided optical modes
• Spatially resolving amplitude and phase of light with a reconfigurable photonic integrated circuit