Controlling the Dynamics of Quantum Mechanical Systems Sustaining Dipole-Forbidden Transitions via Optical Nanoantennas

TL;DR

This paper proposes a method to excite dipole-forbidden transitions in quantum systems using specially designed optical nanoantennas that enhance higher-order multipole moments, enabling new spectroscopic and sensing applications.

Contribution

It introduces a design for optical nanoantennas that significantly enhance multipole moments, allowing excitation of otherwise forbidden transitions in quantum systems.

Findings

Enhanced electric quadrupole transition excitation by nanoantennas

Self-consistent modeling of excitation, emission, and dynamics

Potential applications in spectroscopy and sensing

Abstract

We suggest to excite dipole-forbidden transitions in quantum-mechanical systems by using appropriately designed optical nanoantennas. The antennas are tailored such that their near-field contains sufficiently strong contributions of higher-order multipole moments. The strengths of these moments exceed their free space analogs by several orders of magnitude. The impact of such excitation enhancement is exemplarily investigated by studying the dynamics of a three-level system. It decays upon excitation by an electric quadrupole transition via two electric dipole transitions. Since one dipole transition is assumed to be radiative, the enhancement of this emission serves as a figure of merit. Such self-consistent treatment of excitation, emission, and internal dynamics as developed in this contribution is the key to predict any observable quantity. The suggested scheme may represent a blueprint for future experiments and will find many obvious spectroscopic and sensing applications.