Abstract
Controlling light transport in nonlinear active environments is a topic of considerable interest in the field of optics. In such complex arrangements, of particular importance is to devise strategies to subdue chaotic behaviour even in the presence of gain/loss and nonlinearity, which often assume adversarial roles. Quite recently, notions of parity-time (PT) symmetry have been suggested in photonic settings as a means to enforce stable energy flow in platforms that simultaneously employ both amplification and attenuation. Here we report the experimental observation of optical solitons in PT-symmetric lattices. Unlike other non-conservative nonlinear arrangements where self-trapped states appear as fixed points in the parameter space of the governing equations, discrete PT solitons form a continuous parametric family of solutions. The possibility of synthesizing PT-symmetric saturable absorbers, where a nonlinear wave finds a lossless path through an otherwise absorptive system is also demonstrated.
Highlights
Controlling light transport in nonlinear active environments is a topic of considerable interest in the field of optics
Apart from a few well-studied cases, the interaction of these two processes still remains poorly understood. For example, such nonlinear gain/loss systems are routinely encountered in laser configurations or in nonlinear active cavities and optical fibres, which are typically described by Ginzburg–Landau-type equations[2,3]
One way to avoid these complications is to ensure that the linear spectrum is completely real, even though the underlying problem itself is non-Hermitian. An answer to this interesting possibility was given few years ago by Bender and Boettcher when they indicated that a wide class of non-Hermitian Hamiltonians can display altogether real spectra, provided they respect parity-time (PT) symmetry[4]
Summary
Controlling light transport in nonlinear active environments is a topic of considerable interest in the field of optics. Energy in a.u. Width in positions discrete mesh lattice satisfies PT symmetry provided that it remains invariant under n- À n, m- À m and after complex conjugation In this locally PT-symmetric environment, stable discrete solitons exist
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