Quantum Control of Thermal Emission from Photonic Crystals with Two-Level Atoms

Thermal light engineering is a field of considerable interest and potential. We study quantum light-matter interactions in a one-dimensional photonic crystal with two-level atoms as the active medium, replacing classical oscillators in traditional blackbody models. In a thermal bath with pumping, these atoms modulate thermal emission via interactions with photonic modes. The model with quantum two-level systems enables the processes of spontaneous emission, stimulated absorption, and stimulated emission. Equilibrium and nonequilibrium regimes depend on competition between pumping and thermal relaxation rates. Strong light-matter interaction and photon decay govern dynamics and steady states. In equilibrium, with a high thermal relaxation rate, photon numbers are initially determined by spontaneous emission and later stabilize due to stimulated absorption, influenced by light-matter interaction strength. In-band-gap photons reach steady states at a time scale of one or two orders of magnitude longer than outside-band-gap photons. Interestingly, for a strong light-matter interaction, all photons in the equilibrium regimes show Planckian radiation, regardless of their frequencies in or out of the band gaps. Band-gap suppression of thermal emission is more pronounced with weaker light-matter interaction or larger photon decay. In the nonequilibrium regime, the dynamics of photon numbers exhibit a multi-time-scale process transitioning to steady states due to strong pumping and stimulated processes. Steady-state electron populations of two-level atoms deviate from the Fermi-Dirac distribution, and the steady-state photon numbers exhibit super-Planckian emission. These findings enable quantum control of thermal emission spectra, which is relevant for reducing thermal noise in quantum computing or enhancing radiative cooling.