Semi-empirical Quantum Optics for Mid-Infrared Molecular Nanophotonics

TL;DR

This paper introduces a semi-empirical quantum optics model for mid-infrared nanophotonics, enabling efficient design and understanding of light-matter interactions in nanoscale resonators for quantum control applications.

Contribution

The authors develop a semi-empirical quantum optics approach that accurately models mid-IR nanostructures, simplifying design and analysis compared to first-principles methods.

Findings

Reproduces experimental vibrational relaxation rates

Provides design rules for tip-enhanced vibrational control

Proposes intensity-dependent phase shifts in weak coupling regime

Abstract

Nanoscale infrared (IR) resonators with sub-diffraction limited mode volumes and open geometries have emerged as new platforms for implementing cavity quantum electrodynamics (QED) at room temperature. The use of infrared (IR) nano-antennas and tip nanoprobes to study strong light-matter coupling of molecular vibrations with the vacuum field can be exploited for IR quantum control with nanometer and femtosecond resolution. In order to accelerate the development of molecule-based quantum nano-photonic devices in the mid-IR, we develop a generally applicable semi-empirical quantum optics approach to describe light-matter interaction in systems driven by mid-IR femtosecond laser pulses. The theory is shown to reproduce recent experiments on the acceleration of the vibrational relaxation rate in infrared nanostructures, and also provide physical insights for the implementation of coherent phase rotations of the near-field using broadband nanotips. We then apply the quantum framework to develop general tip-design rules for the experimental manipulation of vibrational strong coupling and Fano interference effects in open infrared resonators. We finally propose the possibility of transferring the natural anharmonicity of molecular vibrational levels to the resonator near-field in the weak coupling regime, to implement intensity-dependent phase shifts of the coupled system response with strong pulses. Our semi-empirical quantum theory is equivalent to first-principles techniques based on Maxwell's equations, but its lower computational cost suggests its use a rapid design tool for the development of strongly-coupled infrared nanophotonic hardware for applications ranging from quantum control of materials to quantum information processing.