Presence of temporal dynamical instabilities in topological insulator lasers

Abstract

Topological insulator lasers are a newly introduced kind of lasers in which light snakes around a cavity without scattering. Like for an electron current in a topological insulator material, a topologically protected lasing mode travels along the cavity edge, steering neatly around corners and imperfections without scattering or leaking out. In a recent experiment, topological insulator lasers have been demonstrated using a square lattice of coupled semiconductor microring resonators with a synthetic magnetic field. However, laser arrays with slow population dynamics are likely to show dynamical instabilities in a wide range of parameter space corresponding to realistic experimental conditions, thus preventing stable laser operation. While topological insulator lasers provide an interesting mean for combating disorder and help collective oscillation of lasers at the edge of the lattice, it is not clear whether chiral edge states are immune to dynamical instabilities. In this work we consider a realistic model of semiconductor class-B topological insulator laser and show that chiral edge states are not immune to dynamical instabilities.

Theory of chiral edge state lasing in a two-dimensional topological system

“…Such topological lasers appear promising to solve a long-standing technological problem in opto-electronics, namely the realization of large-area devices offering high-power coherent emission [32]: a pioneering theoretical work [33] has in fact pointed out that the topological protection against fabrication defects should make laser operation into topological edge states to remain single mode and to have a high slope efficiency even well above the laser threshold. This optimistic view was somehow questioned in [34] for the specific case of semiconductor-based devices: using a standard model of laser operation in these systems, dynamical instabilities stemming from the combination of nonlinear frequency shifts and of the slow carrier relaxation time were predicted. The purpose of this article is to build a generic theory of topological laser operation.…”

Nonlinear mode competition and symmetry-protected power oscillations in topological lasers

“…Looking beyond this symmetry class, it will be worthwhile to explore the role of nonlinear distributed gain and loss in topological-insulator lasers [30,31], where topological edge states align continuously along an edge band. This is a scenario which has been predicted to be more fragile against the carrier dynamics in the medium [53], but is generally expected to benefit from non-hermitian effects, as has already been demonstrated for complex and directed coupling [54]. It would therefore be desirable to classify in general which nonlinearly extended dynamical symmetries can exist in these and other universality classes of topological systems, and whether this leads to novel operation regimes as described here for the case of non-hermitian chargeconjugation symmetry.…”

Ultrashort Pulse Generation in Nanolasers by Means of Lorenz–Haken Instabilities

“…Several experimental and theoretical proposals for both photonic [ 8–21 ] and plasmonic [ 22–26 ] nanolasers have demonstrated the feasibility to automatically start a pulsed lasing state under continuous wave (CW) excitation, paving the way for the integration of ultra‐fast lasers at the nanoscale. Following the ideas developed for conventional “macroscopic” lasers, they are based on the well‐known mechanisms of mode‐competition, passive Q‐switching and mode‐locking.…”