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 these 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.
Highlights
Topological quantum devices aim to evoke states that display a unique response to external stimuli
We find that this setting supports stationary lasing in topological modes over wide ranges of parameter space, and opens up a phase transition to an operation regime that exhibits topologically protected power oscillations
For our laser arrays (1) with saturable gain (2), these deviations manifest themselves as linear static perturbations in the bare resonator frequencies ws,n and the couplings kn, kn¢, and the symmetry-breaking nonlinearities quantified by the linewidth-enhancement factors αs
Summary
Nonlinear mode competition and symmetry-protected power oscillations in topological lasers. Can 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
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