Limits...
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.


Experimental realization of the discrete mesh lattice.Two coupled fibre loops (a) of different length are used to implement the mesh lattices displayed in (b–d). Four kilometres of dispersion compensating fibres (DCF) are inserted into the loops to amplify the nonlinear phase shift. The phase and amplitude of the signals are controlled by a phase modulator (PM) and acousto-optical modulators (AOM). Losses are compensated by fibre amplifiers (EDFA). The temporal pulse evolution in the loops can be mapped onto 1+1D mesh-lattices spanned by the discrete time m and position n. In contrast to the passive lattice (b) a constant gain (red) in the long loop and loss (blue) in the short loop are equivalent to amplified and attenuated diagonal paths through the lattice (c). (d) By alternating gain and loss on every other round trip (purple) and by inserting an appropriate phase modulation a PT-symmetric system can be generated, which consists of amplifying and lossy waveguides.
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f1: Experimental realization of the discrete mesh lattice.Two coupled fibre loops (a) of different length are used to implement the mesh lattices displayed in (b–d). Four kilometres of dispersion compensating fibres (DCF) are inserted into the loops to amplify the nonlinear phase shift. The phase and amplitude of the signals are controlled by a phase modulator (PM) and acousto-optical modulators (AOM). Losses are compensated by fibre amplifiers (EDFA). The temporal pulse evolution in the loops can be mapped onto 1+1D mesh-lattices spanned by the discrete time m and position n. In contrast to the passive lattice (b) a constant gain (red) in the long loop and loss (blue) in the short loop are equivalent to amplified and attenuated diagonal paths through the lattice (c). (d) By alternating gain and loss on every other round trip (purple) and by inserting an appropriate phase modulation a PT-symmetric system can be generated, which consists of amplifying and lossy waveguides.

Mentions: Our experimental platform consists of two coupled fibre loops having slightly different lengths11505152 (see Supplementary Fig. 1 and Supplementary Methods). Like in time multiplexing, subsequent passes through the short and the long loop cause a pulse to spread on a time mesh lattice with discrete arrival times being equivalent to positions in the spatial domain (see Fig. 1). As group velocity dispersion is negligible in our setup, each pulse is completely characterized by a single complex amplitude that is denoted by and for the short and the long loop, respectively. Here m stands for the time interval as measured in round trips and n denotes the position of a single pulse during one cycle. When a pulse travels through the longer loop, it will not only step in time from m to m+1, but will also be slightly delayed thus hopping from position n to n+1. Conversely, the propagation in the short loop is equivalent to shifting the pulse to the descendent position at n−1. In what follows, we discuss the ensuing optical evolution in a co-moving reference frame.


Observation of optical solitons in PT-symmetric lattices.

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

Experimental realization of the discrete mesh lattice.Two coupled fibre loops (a) of different length are used to implement the mesh lattices displayed in (b–d). Four kilometres of dispersion compensating fibres (DCF) are inserted into the loops to amplify the nonlinear phase shift. The phase and amplitude of the signals are controlled by a phase modulator (PM) and acousto-optical modulators (AOM). Losses are compensated by fibre amplifiers (EDFA). The temporal pulse evolution in the loops can be mapped onto 1+1D mesh-lattices spanned by the discrete time m and position n. In contrast to the passive lattice (b) a constant gain (red) in the long loop and loss (blue) in the short loop are equivalent to amplified and attenuated diagonal paths through the lattice (c). (d) By alternating gain and loss on every other round trip (purple) and by inserting an appropriate phase modulation a PT-symmetric system can be generated, which consists of amplifying and lossy waveguides.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Experimental realization of the discrete mesh lattice.Two coupled fibre loops (a) of different length are used to implement the mesh lattices displayed in (b–d). Four kilometres of dispersion compensating fibres (DCF) are inserted into the loops to amplify the nonlinear phase shift. The phase and amplitude of the signals are controlled by a phase modulator (PM) and acousto-optical modulators (AOM). Losses are compensated by fibre amplifiers (EDFA). The temporal pulse evolution in the loops can be mapped onto 1+1D mesh-lattices spanned by the discrete time m and position n. In contrast to the passive lattice (b) a constant gain (red) in the long loop and loss (blue) in the short loop are equivalent to amplified and attenuated diagonal paths through the lattice (c). (d) By alternating gain and loss on every other round trip (purple) and by inserting an appropriate phase modulation a PT-symmetric system can be generated, which consists of amplifying and lossy waveguides.
Mentions: Our experimental platform consists of two coupled fibre loops having slightly different lengths11505152 (see Supplementary Fig. 1 and Supplementary Methods). Like in time multiplexing, subsequent passes through the short and the long loop cause a pulse to spread on a time mesh lattice with discrete arrival times being equivalent to positions in the spatial domain (see Fig. 1). As group velocity dispersion is negligible in our setup, each pulse is completely characterized by a single complex amplitude that is denoted by and for the short and the long loop, respectively. Here m stands for the time interval as measured in round trips and n denotes the position of a single pulse during one cycle. When a pulse travels through the longer loop, it will not only step in time from m to m+1, but will also be slightly delayed thus hopping from position n to n+1. Conversely, the propagation in the short loop is equivalent to shifting the pulse to the descendent position at n−1. In what follows, we discuss the ensuing optical evolution in a co-moving reference frame.

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.