Long-lived elementary excitations and light coherence in topological lasers

Abstract

Combining topologically protected chiral light transport and laser amplification gives rise to topological lasers, whose operation is immune to fabrication imperfections and defects, uncovering the role of topology in a novel nonlinear non-Hermitian regime. We study a topological laser based on the photonic Haldane model with selective pumping of chiral edge modes described by saturable gain. We investigate elementary excitations around the mean-field steady state and their consequences for the coherence properties. In particular, we show that the hybridization of chiral edge modes gives rise to long-lived elementary excitations, leading to large phase fluctuations in the emitted light field and a decrease in light coherence. In contrast to topologically trivial lasers, the lifetime of elementary excitations is robust against disorder in topological lasers. However, the lifetime depends strongly on the edge-mode dispersion around the lasing frequency. As a result, the lifetime can be reduced by orders of magnitude for lasing of different edge modes, leading to a suppression of phase fluctuations and larger coherence of the emitted light. On the other hand, amplitude fluctuations and the second-order autocorrelation function are moderately increased at the same time.

Physics and Applications of High‐β Micro‐ and Nanolasers

“…[214] Recent theoretical studies showed that topological lasers in comparison to conventional laser arrays have a significantly improved temporal coherence in the presence of spatial disorder, [215] while in its absence, the temporal coherence is slightly below the conventional case, but the second-order photon autocorrelation function is still close to unity. [216] The latter was experimentally verified in refs. [204,217].…”

Linearized theory of the fluctuation dynamics in 2D topological lasers

“…Among all Bogoliubov modes, the ones with the slowest relaxation rate play a very important role in determining the long-distance, long-time behaviour of the spatiotemporal coherence properties of the laser emission [15]. If the localization of the edge mode was uniform in k, λ(k) = 1 (as assumed, for instance, in [30]), Eq. ( 29) would predict a quartic ∼ k 4 behaviour of the decay rate of the Goldstone branch at small k, proportional to the curvature of the edge mode or, equivalently, to the inverse of the effective mass 1/m * , Im(ω Bog + (k)) −(k 2 /2m * ) 2 /Γ.…”

Kibble-Zurek mechanism in polariton graphene

“…These unique features of exciton-polaritons allow merging topological photonics [1] with the field of interacting quantum fluids [12,13]. The first important question arising at the crossroads of the two fields is the modification of topology by interactions of the fluids [14][15][16] and, in particular, the stability of the topologically protected modes in lasers [17][18][19]. The possibilities of synergy of the two fields were already demonstrated by enhancement of topological protection in lattices due to quantum fluid interactions [20].…”