We develop a semiclassical theory of laser oscillation into a chiral edge state of a topological photonic system endowed with a frequency-dependent gain. As an archetypal model of this physics, we consider a Harper–Hofstadter lattice embedding population-inverted, two-level atoms as a gain material. We show that a suitable design of the spatial distribution of gain and its spectral shape provides flexible mode-selection mechanisms that can stabilize single-mode lasing into an edge state. Implications of our results for recent experiments are outlined.
PACS: 03.65.Vf, 42.60.Da, 42.65.Sf, 73.43.-f
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Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan ↩
CNR-IOM Democritos, Via Bonomea 265, I-34136 Trieste, Italy ↩
INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento, I-38123 Povo, Italy ↩