All-dielectric nanoantennas for unidirectional excitation of electromagnetic guided modes

TL;DR

This paper demonstrates how asymmetrical excitation of dielectric nanoparticles can generate chiral near fields, enabling unidirectional excitation of guided modes with high front--to--back ratios, advancing nanophotonics and quantum information applications.

Contribution

It introduces a novel method of using asymmetrical excitation of dielectric nanoparticles to achieve unidirectional mode excitation via multipole mode control.

Findings

Achieved up to 5.5 front--to--back ratio for dielectric waveguides.

Achieved up to 7.5 front--to--back ratio for plasmonic modes.

Demonstrated control of chiral near fields through multipole excitation.

Abstract

Engineering of intensity and direction of radiation from a single quantum emitter by means of structuring of their environment at the nanoscale is at the cornerstone of modern nanophotonics. Recently discovered systems exhibiting spin--orbit coupling of light are of particular interest in this context. In this Letter, we have demonstrated that asymmetrical excitation of a high-index subwavelength dielectric nanoparticle by a point dipole source located in a notch at its surface results in formation of a chiral near field, which is similar to that of a circularly polarized dipole or quadrupole. Using numerical simulations, we have shown that this effect is the result of a higher multipole (quadrupole and octupole) modes excitation within the nanoparticle. We have applied this effect for unidirectional excitation of dielectric waveguide and surface plasmon-polariton modes. We have achieved the value of front--to--back ratio up to 5.5 for dielectric waveguide and to 7.5 for the plasmonic one. Our results are important for the integrated nanophotonics and quantum information processing systems.