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Observation of optical solitons in PT-symmetric lattices.

Wimmer M, Regensburger A, Miri MA, Bersch C, Christodoulides DN, Peschel U - Nat Commun (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Optics, Information and Photonics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstraße 7/B2, 91058 Erlangen, Germany [2] Erlangen Graduate School in Advanced Optical Technologies (SAOT), 91058 Erlangen, Germany.

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.

No MeSH data available.


Nonlinear self-trapping in a PT-symmetric mesh lattice.Same as in Fig. 4 but in the nonlinear regime. The nonlinearity cannot prevent the expansion above the PT threshold (a,c,e). Yet at high powers a discrete soliton is formed once PT symmetry is restored (G=1.4,ϕ0=0.4π) (b,d,f). In this case internal oscillations are observed because of mode interference effects. For simulations a nonlinear factor of Γ=0.24π was chosen. In the experiment the power of the initial pulse is Pin≈40 mW.
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f5: Nonlinear self-trapping in a PT-symmetric mesh lattice.Same as in Fig. 4 but in the nonlinear regime. The nonlinearity cannot prevent the expansion above the PT threshold (a,c,e). Yet at high powers a discrete soliton is formed once PT symmetry is restored (G=1.4,ϕ0=0.4π) (b,d,f). In this case internal oscillations are observed because of mode interference effects. For simulations a nonlinear factor of Γ=0.24π was chosen. In the experiment the power of the initial pulse is Pin≈40 mW.

Mentions: Once the power of the single initial pulse is raised, nonlinear processes come into play and hence discrete solitons can in principle form in this PT configuration. In general, the strong phase potential slightly decouples the adjacent lattice sites of the mesh structure which in turn hinders the spreading of the initial distribution. As a result, nonlinear effects can be observed at much lower peak powers (see Supplementary Fig. 14). When the associated linear lattice is operated above the critical threshold the system becomes unstable and the nonlinearity is unable to establish a solitary wave (Fig. 5a,c). This exponential increase in energy is shown in Fig. 5e. Conversely, when the band structure is real (below PT threshold), an optical soliton is observed as depicted in Fig. 5b,d. As the PT lattice has a four-side spatial periodicity a single-site excitation does not result in a stationary profile but instead excites strong internal oscillations around the PT soliton. In all cases the soliton remains almost invariant during propagation without any appreciable increase in its energy (Fig. 5f).


Observation of optical solitons in PT-symmetric lattices.

Wimmer M, Regensburger A, Miri MA, Bersch C, Christodoulides DN, Peschel U - Nat Commun (2015)

Nonlinear self-trapping in a PT-symmetric mesh lattice.Same as in Fig. 4 but in the nonlinear regime. The nonlinearity cannot prevent the expansion above the PT threshold (a,c,e). Yet at high powers a discrete soliton is formed once PT symmetry is restored (G=1.4,ϕ0=0.4π) (b,d,f). In this case internal oscillations are observed because of mode interference effects. For simulations a nonlinear factor of Γ=0.24π was chosen. In the experiment the power of the initial pulse is Pin≈40 mW.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525206&req=5

f5: Nonlinear self-trapping in a PT-symmetric mesh lattice.Same as in Fig. 4 but in the nonlinear regime. The nonlinearity cannot prevent the expansion above the PT threshold (a,c,e). Yet at high powers a discrete soliton is formed once PT symmetry is restored (G=1.4,ϕ0=0.4π) (b,d,f). In this case internal oscillations are observed because of mode interference effects. For simulations a nonlinear factor of Γ=0.24π was chosen. In the experiment the power of the initial pulse is Pin≈40 mW.
Mentions: Once the power of the single initial pulse is raised, nonlinear processes come into play and hence discrete solitons can in principle form in this PT configuration. In general, the strong phase potential slightly decouples the adjacent lattice sites of the mesh structure which in turn hinders the spreading of the initial distribution. As a result, nonlinear effects can be observed at much lower peak powers (see Supplementary Fig. 14). When the associated linear lattice is operated above the critical threshold the system becomes unstable and the nonlinearity is unable to establish a solitary wave (Fig. 5a,c). This exponential increase in energy is shown in Fig. 5e. Conversely, when the band structure is real (below PT threshold), an optical soliton is observed as depicted in Fig. 5b,d. As the PT lattice has a four-side spatial periodicity a single-site excitation does not result in a stationary profile but instead excites strong internal oscillations around the PT soliton. In all cases the soliton remains almost invariant during propagation without any appreciable increase in its energy (Fig. 5f).

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Optics, Information and Photonics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstraße 7/B2, 91058 Erlangen, Germany [2] Erlangen Graduate School in Advanced Optical Technologies (SAOT), 91058 Erlangen, Germany.

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.

No MeSH data available.