$\pi$ mode lasing in the non-Hermitian Floquet topological system

Abstract

$\pi$ modes are unique topological edge states appearing in Floquet systems with periodic modulations of the underlying lattice structure in evolution variable, such as dynamically modulated Su-Schrieffer-Heeger (SSH) lattices. These edge states are anomalous states usually appearing between Floquet replicas of the same band, even if standard topological index remains zero for this band. While linear and nonlinear $\pi$ modes were observed in conservative systems, they have never been studied in nonlinear regime in the non-Hermitian systems with structured gain and losses. Here we show that SSH waveguide array with periodically oscillating waveguide positions in propagation direction and with parity-time symmetric refractive index landscape, can support $\pi$ modes that are damped or amplified at different ends of the array. By including nonlinearity and nonlinear absorption into our continuous system, we achieve stable lasing in $\pi$ mode at one end of the array. The representative feature of this system is that lasing in it is thresholdless and it occurs even at low gain-loss amplitudes. The degree of localization of lasing $\pi$ modes can be flexibly controlled by the amplitude of transverse waveguide oscillations. This work therefore introduces a new type of topological Floquet laser and a route to manipulation of $\pi$ modes by structured gain and losses.

arXiv comment9 pages, 3 figures, to appear in APL Photonics

References in corpus (31)

• Topological Insulators
• Topological insulators and superconductors
• Topological Photonics
• Topological Photonics
• Photonic Floquet Topological Insulators
• Lasing in topological edge states of a 1D lattice
• Nonlinear topological photonics
• Non-Hermitian Topology and Exceptional-Point Geometries
• Observation of photonic anomalous Floquet Topological Insulators
• Experimental observation of anomalous topological edge modes in a slowly-driven photonic lattice
• Topologically protected midgap states in complex photonic lattices
• Nonlinear control of PT-symmetry and non-Hermitian topological states
• Active topological photonics
• Low-threshold topological nanolasers based on second-order corner state
• Lasing from multipole topological corner states
• Floquet topological transitions in a driven one-dimensional topological insulator
• Observation of anomalous π modes in photonic Floquet engineering
• Anomalous single-mode lasing induced by nonlinearity and the non-Hermitian skin effect
• Complex classes of periodically driven topological lattice systems
• Mode-Locked Topological Insulator Laser Utilizing Synthetic Dimensions
• Room temperature electrically pumped topological insulator lasers
• Nonlinear non-Hermitian higher-order topological laser
• Topological Valley Hall Edge State Lasing
• Theory of Topological Corner State Laser in Kagome Waveguide Arrays
• Observation of $\pi$ solitons in oscillating waveguide arrays
• Photonic Flatband Laser
• Floquet topological insulator laser
• Edge states in dynamical superlattices
• Topological Microlaser with A non-Hermitian Topological Bulk
• Tunable two-dimensional laser arrays with zero-phase locking
• Floquet topological insulators with hybrid edges

Cited by in corpus (2)

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