# Experimental demonstration of linear and spinning Janus dipoles for polarisation and wavelength selective near-field coupling

## TL;DR

This paper experimentally demonstrates how Janus dipoles with electric and magnetic components can be spectrally and phase selectively excited to control near-field interference and directional coupling in nanophotonics, introducing a novel spinning Janus dipole with omnidirectional or null coupling.

## Contribution

It introduces a method for spectral and phase selective excitation of Janus dipoles and presents a new spinning Janus dipole with cylindrical symmetry for enhanced near-field control.

## Key findings

- Spectral and phase selective excitation of Janus dipoles achieved.
- Control over directionality and coupling strength demonstrated.
- Introduction of a spinning Janus dipole with omnidirectional coupling or noncoupling.

## Abstract

The electromagnetic field scattered by nano-objects contains a broad range of wave vectors and can be efficiently coupled to waveguided modes. The dominant contribution to scattering from subwavelength dielectric and plasmonic nanoparticles is determined by electric and magnetic dipolar responses. Here, we experimentally demonstrate spectral and phase selective excitation of Janus dipoles, sources with electric and magnetic dipoles oscillating out of phase, in order to control near-field interference and directional coupling to waveguides. We show that by controlling the polarisation state of the dipolar excitations and the excitation wavelength to adjust their relative contributions, directionality and coupling strength can be fully tuned. Furthermore, we introduce a novel spinning Janus dipole featuring cylindrical symmetry in the near and far field, which results in either omnidirectional coupling or noncoupling. Controlling the propagation of guided light waves via fast and robust near-field interference between polarisation components of a source is required in many applications in nanophotonics and quantum optics.