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

Spectroscopic investigations have played a key role in understanding the microscopic properties of matter, and its interaction with electromagnetic radiation. The associated spectroscopic signatures that are involved in such investigations are symmetric Lorentz and asymmetric Fano line shapes [1]. The latter has found several applications in photonics such as optical switching, sensing, lasing and nonlinear and slow light devices [2]. This led to investigation of Fano resonances in a large variety of different systems [3]. Thus, control over their generation from initially Lorentzian line shapes becomes necessary. To this end, we demonstrate through ab initio simulations of coupled light-matter systems, a transition from an initially Lorentzian line shape into a Fano resonance when we couple the matter subsystem strongly to the electromagnetic continuum [4]. We show this for the case involving bare electronic as well as polaritonic excitations of a coupled light-matter systems. In addition to the control over the generation of Fano resonances, we have access to the Purcell enhancement of spontaneous emission together with the observation of electromagnetically induced transparency which is a special case of Fano resonance. Our findings has potential applications for realizing tunable Fano resonances of different matter systems strongly coupled to the electromagnetic continuum as well as it presents an alternative way to realize a Purcell enhancement of the spontaneous emission process.

[1] C. Ott, et al., Science 340, 716-720 (2013).

[2] M. Limonov, Adv. Opt. Photon. 13, 703-771 (2021).

[3] M. Limonov, et al., Nature Photonics 11, 543-554 (2017).

[4] D. M. Welakuh and P. Narang, Transition from Lorentz to Fano Spectral Line Shapes in Non-Relativistic Quantum Electrodynamics, coming to arxiv