Theory of the Coherence of Topological Lasers

Year: 2020

Authors: Amelio I., Carusotto I.

Autors Affiliation: Univ Trento, INO CNR BEC Ctr, I-38123 Povo, Italy; Univ Trento, Dipartimento Fis, I-38123 Povo, Italy.

Abstract: We present a theoretical study of the temporal and spatial coherence properties of a topological laser device built by including saturable gain on the edge sites of a Harper-Hofstadter lattice for photons. For small enough lattices, the Bogoliubov analysis applies, and the coherence time is almost determined by the total number of photons in the device in agreement with the standard Schawlow-Townes phase diffusion. In larger lattices, looking at the lasing edge mode in the comoving frame of its chiral motion, the spatiotemporal correlations of long-wavelength fluctuations display a Kardar-Parisi-Zhang (KPZ) scaling. Still, at very long times, when the finite size of the device starts to matter, the functional form of the temporal decay of coherence changes from the KPZ stretched exponential to a Schawlow-Townes-like exponential, while the nonlinear dynamics of KPZ fluctuations remains visible as a broadened linewidth as compared to the Bogoliubov-Schawlow-Townes prediction. While we establish the above behaviors also for nontopological 1D laser arrays, the crucial role of topology in protecting the coherence from static disorder is finally highlighted: Our numerical calculations suggest the dramatically reinforced coherence properties of topological lasers compared to corresponding nontopological devices. These results open exciting possibilities for both fundamental studies of nonequilibrium statistical mechanics and concrete applications to laser devices.

Journal/Review: PHYSICAL REVIEW X

Volume: 10 (4)      Pages from: 41060-1  to: 41060-20

More Information: We are grateful to Jacqueline Bloch, Leonie Canet, Alessio Chiocchetta, Aurelian Loirette-Pelous, Matteo Secli, Moti Segev, and Davide Squizzato for useful discussions. The addition of Fig. 9 and of Sec. V were stimulated by the constructive feedback that we received from the referees, to whom we are strongly indebted. We acknowledge financial support from the H2020-FETFLAG-2018-2020 project PhoQuS (No. 820392) and from the Provincia Autonoma di Trento. All numerical calculations were performed using the Julia programming language [75].
KeyWords: Excess Spontaneous Emission; Hermitian Optical-systems
DOI: 10.1103/PhysRevX.10.041060

Citations: 40
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