438 research outputs found
On the universal character of the Discrete Nonlinear Schroedinger Equation
No full textWe address the universal applicability of the discrete nonlinear Schrodinger equation. By employing an original but general top-down-bottom-up procedure based on symmetry analysis to the case of optical lattices, we derive the most widely applicable and simplest possible model, revealing that the discrete nonlinear Schrodinger equation is "universally" fit to describe light propagation even in discrete tensorial nonlinear systems and in the presence of nonparaxial and vectorial effects
All-optical switching in a liquid crystalline waveguide
No full textWe demonstrate an all-optical switch based on mode mixing in a liquid crystalline waveguide defined by an external voltage. Efficient switching and rerouting can be achieved with good contrast at low powers in the whole transparency region. (C) 2005 American Institute of Physics
Symmetry-breaking instabilities in perturbed optical lattices: Nonlinear nonreciprocity and macroscopic self-trapping
No full textWe develop an asymptotic analysis of nonlinear energy propagation in lattices subject to slowly varying perturbations, investigating symmetry breaking and its effects. We derive a general set of evolution equations and study them by using catastrophe theory, revealing a wealth of system dynamics. Below a power threshold, symmetry breaking drives nonreciprocal oscillations; beyond that, symmetry breaking yields an effect of "macroscopic" self-trapping, which supports a self-maintained energy imbalance between Bloch bands. We numerically verify the theoretical results and discuss their possible implementation in waveguide arrays
Nonlinear adiabatic evolution and emission of coherent Bloch waves in optical lattices
No full textWe investigate energy propagation in a perturbed optical lattice, studying the nonlinear adiabatic evolution of a light beam. Through an asymptotic model, we demonstrate that: (i) energy propagating in the adiabatic regime visualizes the dispersion relation of the unperturbed lattice; (ii) the adiabatic evolution can be broken by nonlinearity, giving rise to tunneling between Bloch bands; (iii) the tunneling is accompanied by nonlinear emission of one - or more - coherent Bloch waves, the properties of which can be completely controlled by linear and/or nonlinear parameters. We verify the analytical results against numerical simulations and indicate possible experimental implementations
Light propagation through a nonlinear defect: symmetry breaking and controlled soliton emission
No full textWe investigate the emission of solitons at a nonlinear longitudinal defect. We discuss the basic physics and introduce a novel approach to achieve complete nonlinear control of the process. Theoretical results are confirmed by numerical simulations. (c) 2006 Optical Society of America
All-optical switching with a nematic coherent mixer
No full textThe Kerr-like (reorientational) response of nematic liquid crystals (NLC) can be exploited in a guided-wave configuration supporting two TM-polarized modes, by which an integrated-optics switch is demonstrated that is able to all-optically route the signal to either of two outputs. Although the switch optimization would require adiabatically tailored input and output Y-junctions to launch the excitation, its geometry is the simplest offering switching/routing with all-optical control at mW powers. Results on the switching speed is presented
Governing soliton splitting in one-dimensional lattices
No full textWe investigate discrete light dynamics in the presence of a longitudinal defect of arbitrary extension, amplitude and position in a nonlinear waveguide array. We model and discuss the physics of the soliton-defect interaction, showing how to gain complete control over the system outcome for soliton-based data processing. We propose all-optical management in dye-doped liquid crystals
Dispersion spectroscopy of photonic lattices
No full textWe theoretically demonstrate how to acquire the full bandgap spectrum of a photonic lattice of arbitrary profile. Focusing on the ID case in the presence of a linear refractive index acceleration and employing a multiscale analysis, we show that each photonic band can be directly mapped by the light evolution in the lattice, whereas the size of each gap corresponds to the tunneling rate. We verify the analytical results with numerical simulations and discuss experimental realizations of this technique for dispersive spectroscopy. (c) 2006 Optical Society of Americ
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