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

TL;DR

This paper demonstrates that topological defect lasers can operate in stable topological states and exhibit symmetry-protected power oscillations, even with nonlinearities and imperfections, advancing the potential for topological quantum devices.

Contribution

It reveals the existence of stable topological states and symmetry-protected oscillations in nonlinear topological lasers, extending topological photonics into nonlinear regimes.

Findings

Topological defect lasers can operate in stable topological states.

Symmetry-protected power oscillations occur at spectral phase transitions.

These effects are resilient to imperfections and symmetry-breaking.

Abstract

Topological photonics started out as a pursuit to engineer systems that mimic fermionic single-particle Hamiltonians with symmetry-protected modes, whose number can only change in spectral phase transitions such as band inversions. The paradigm of topological lasing, realized in three recent experiments, offers entirely new interpretations of these states, as they can be selectively amplified by distributed gain and loss. A key question is whether such topological mode selection persists when one accounts for the nonlinearities that stabilize such systems at their working point. Here we show that topological defect lasers can indeed stably operate in genuinely topological states. These comprise direct analogues of zero modes from the linear setting, as well as a novel class of states displaying symmetry-protected power oscillations, which appear in a spectral phase transition when the gain is increased. These effects show a remarkable practical resilience against imperfections, even if these break the underlying symmetries, and pave the way to harness the power of topological protection in nonlinear quantum devices.