High Finesse Cavity with Anapole-Assisted Resonant Subwavelength Particle Mirror

TL;DR

This paper introduces a high finesse optical cavity with a subwavelength resonant particle mirror, leveraging anapole excitation to enhance light-matter interactions beyond the electric dipole approximation, with potential applications in nano optics and quantum technologies.

Contribution

The work presents a novel cavity design using a subwavelength resonant particle with anapole excitation to achieve near-unity reflectivity and enhanced subwavelength light-matter interactions.

Findings

Eigenmode solutions show high field concentration at the particle.

Particle designed to scatter as a magnetic quadrupole.

Potential for significant enhancement in nano optics and quantum applications.

Abstract

Strong light interaction with a subwavelength object has been a long pursuing goal with difficulties mainly arising from the diffraction limit. We propose a high finesse cavity with one mirror made of a subwavelength resonant particle as a platform to enhance this interaction. High-quality eigenmode solutions are obtained for such a highly non-paraxial cavity with a very high field concentration at the particle. The eigenmode solutions interact with the small particle in a more general way than by the electric dipole approximation. With the help of the anapole excitation in the dipole term, the particle is designed to scatter like a pure magnetic quadrupole, and in this way, it has anear-unity reflectivity when used as a mirror for the strongly focused field of the eigenmode. Light-matter interactions at the subwavelength scale can be greatly enhanced due to the small size of the particle and the high finesse of the cavity, which can be potentially interesting for applications in nano optics, quantum optomechanics, nonlinear optics, and subwavelength metrology beyond the electric dipole approximation.