Article

Phase Transitions of Nonlinear Waves in Quadratic Waveguide Arrays

Friedrich-Schiller-University Jena, Max-Wien-Platz 1, 07743 Jena, Germany.
Physical Review Letters (Impact Factor: 7.51). 12/2010; 105(23):233905. DOI: 10.1103/PhysRevLett.105.233905
Source: PubMed

ABSTRACT

We study two-color parametric nonlinear modes in waveguide arrays with a quadratic nonlinear response. We predict theoretically and observe experimentally a new type of phase transition manifested in an abrupt power-controlled change of the mode structure from unstaggered to staggered, due to the interplay of localization and synchronization in parametrically driven discrete systems.

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Available from: Dragomir N Neshev, Dec 17, 2013
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    • "In such systems, light from the fundamental wave (FW) is coupled by the χ (2) nonlinearity to the second harmonic (SH) giving rise to a strong cascaded quadratic nonlinearity. Recently a new type of phase transition in the nonlinear localised states was identified due to the competition between selffocusing and SH waveguide coupling, where the SH phase profile abruptly switches from in-phase to staggered structure as the input power is increased [2]. However, the temporal extent of the short laser pulses used in realistic experiments leads to a complex pulse reshaping in the course of propagation. "
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    ABSTRACT: We present theoretical and experimental studies on nonlinear beam propagation in lithium niobate waveguide arrays utilizing higher order second harmonic bands. We find that the implementation of the higher order second harmonic bands leads to a number of new effects. The combined interaction of two second harmonic bands with a propagating fundamental beam can lead to a complete inhibition of nonlinear effects or to the formation of discrete spatial solitons, depending only on the wavelength of the fundamental wave. Furthermore we analyze the properties of discrete solitons subjected to linear coupling of the second harmonic. Here we predict and demonstrate experimentally a power dependent phase transition of the soliton topology.
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