Real-time spectral combs from delayed quantum feedback in multimode cavity QED

arXiv:2611.13465v1 Announce Type: new Abstract: We study the time-dependent physical spectrum of light for a two-level atom coupled to a large, but discrete, number of modes of an electromagnetic cavity. Radiation emitted by the atom, placed at the center of the cavity, returns after the round-trip time $t_r$, re-excites it, and is re-emitted, producing a sequence of atomic population revivals. For a coupling approximately flat over the atomic linewidth, the emission dynamics reduces to a delay-differential equation of Bixon--Jortner type. Using its analytical solution in terms of Laguerre polynomials, we investigate how successive emission and reabsorption cycles shape the time-dependent spectrum.