Transition from Lorentz to Fano Spectral Line Shapes in Non-Relativistic Quantum Electrodynamics

TL;DR

This paper demonstrates how strong coupling in multimode photonic systems can induce a transition from Lorentzian to Fano spectral line shapes, enabling tunable control over light-matter interactions such as emission and transparency.

Contribution

It introduces a method to control spectral line shapes in light-matter systems by tuning the coupling strength to the electromagnetic continuum, facilitating dynamic spectral shape switching.

Findings

Achieved Lorentzian to Fano transition via enhanced light-matter coupling.

Controlled the spectral shape by adjusting coupling strength.

Potential for tunable Fano resonances in molecular and material systems.

Abstract

Spectroscopic signatures associated with symmetric Lorentzian and asymmetric Fano line shapes are ubiquitous. Distinct features of Fano resonances in contrast with conventional symmetric resonances have found several applications in photonics such as optical switching, sensing, lasing, and nonlinear and slow-light devices. Therefore, it is important to have control over the generation of these resonances. In this work, we show through ab initio simulations of coupled light-matter systems that Fano interference phenomena can be realized in a multimode photonic environment by strong coupling to the electromagnetic continuum. Specifically, we show that by effectively enhancing the light-matter coupling strength to the photon continuum in an experimentally feasible way, we can achieve a transition from Lorentzian to Fano lines shapes for both electronic and polaritonic excitations. An important outcome of switching between these spectral signatures is the possibility to control the Purcell enhancement of spontaneous emission alongside electromagnetically induced transparency which is a special case of Fano resonances. Switching from Fano back to a Lorentzian profile can be achieved by physically reducing the coupling strength to the continuum of modes. Our results hold potential for realizing tunable Fano resonances of molecules and materials interacting with the electromagnetic continuum within multimode photonic environments.