Discrete Optical Solitons Research Articles

Discrete ultra-slow optical solitons based on optomechanical effect.

We demonstrate that discrete solitons are possible in a micro-fabricated optomechanical structure, which consists of N identical cells. Analyses illustrate that these states originate from photon-phonon interaction or optomechanical effect. In principle, the self-localized entities are capable of exhibiting very slow velocities, depending on the photon hopping rate and phase difference among successive optomechanical cells. The theoretical results pave the way for a new type of on-chip system to observe discrete optical solitons behaviors and may have potential application in on-chip manipulation of photonic information processing.

Discrete optical soliton scattering by local inhomogeneities

The nonlinear wave scattering by local inhomogeneities in discrete optical systems is studied both analytically and numerically. The presented theory describes the reflection and transmission of discrete optical solitons at a point defect. In particular, the derived expressions determine the reflected and transmitted pulses from the incident one. In the range of validity, the analytical results are in excellent agreement with the numerical simulations. It is demonstrated that the point defects in structured optical materials represent effective tool for controlling and manipulation of the nonlinear light pulses.

Wave interactions and wave-structure scattering in nonlinear patterned waveguides

The nonlinear interactions between discrete optical solitons that propagate in different regimes of diffraction, and the nonlinear scattering of dispersive waves by local optical potentials, were studied experimentally. It is well known in electromagnetism that when linear coherent waves meet they interfere without interactions. Linear waves also scatter through local optical structures without exchanging any power with guided and anti-guided modes of these structures. When a focusing Kerr nonlinearity is present, linearly inhibited phenomena, which break these rules, are shown to exist. Our studies were performed with Silica glass and semiconductor AlGaAs nonlinear planar modulated waveguides, excited by ultra-short pulses in the near infrared spectral regime.

Nonlinear wave interactions in patterned Silica and AlGaAs waveguides

Abstract We study nonlinear interactions between discrete optical solitons that propagate in different regimes of diffraction, and the nonlinear scattering of dispersive waves by local optical potentials. It is well known in optics that when linear coherent waves meet, they interfere without interactions. Linear waves also scatter through local optical structures not exchanging any power with the guided modes of these structures. As a focusing Kerr nonlinearity is present, such linearly-inhibited phenomena can exist. Our studies are performed in silica and AlGaAs nonlinear waveguides, excited by ultra-short pulses in the near infrared.

Spectral-discrete solitons and localization in frequency space

We report families of discrete optical solitons in frequency space, or spectral-discrete solitons existing in a dispersive Raman medium, where individual sidebands are coupled by coherence. The associated time-domain patterns correspond either to trains of ultrashort pulses or to weakly modulated waves. We describe the physics behind the spectral localization and study soliton bifurcations, stability, and dynamics.

Introduction

Discreteness provides unique opportunities for controlling the flow of light. As in solidstate physics, optical discrete or lattice configurations are known to exhibit a succession of allowed Floquet-Bloch bands and forbidden bandgaps. In weakly coupled systems, the Floquet-Bloch states can be accurately described by local modes, and thus the tight-binding approximation or coupled-mode theory is applicable. As a result, the field dynamics become effectively discretized. In optics, arrays of evanescently coupled waveguides, photonic crystal fibers, chains of coupled microresonators, and photonic crystals are prime examples of such structures where discrete wave dynamics can be experimentally investigated. Perhaps the most exciting outcome of the interplay between discreteness and optica nonlinearity is the existence of self-localized entities better known as discrete solitons. This class of optical solitons were first suggested in the late 1980s and successfully observed in AlGaAs waveguide arrays a decade later. Since then, discrete optical solitons have been observed in many other material systems such as in optically induced lattices, in quadratic waveguide arrays, and in liquid-crystal cells. This experimental work has not only resulted in a deeper understanding of nonlinear processes in periodic environments, but it has also helped to assess the potential of these self-trapped states toward future applications. Nowadays, the field of discrete optical dynamics in nonlinear lattices is at an exciting stage of development. Even though some of the basic concepts in this area have been around for a while, much remains to be explored and discovered.

Switching of discrete optical solitons in engineered waveguide arrays.

We demonstrate a simple concept for controlling nonlinear switching of discrete solitons in arrays of weakly coupled optical waveguides, for both cubic and quadratic nonlinear response. Based on the effective discrete nonlinear equations describing light propagation in the waveguide arrays in the tight-binding approximation, we demonstrate the key ideas of the array engineering by means of a steplike variation of the waveguide coupling. We demonstrate the digitized switching of a narrow input beam for up to 11 neighboring waveguides, in the case of the cubic nonlinearity, and up to 10 waveguides, in the case of the quadratic nonlinearity. We discuss our predictions in terms of the physics of the engineered Peierls-Nabarro (PN) potential experienced by strongly localized nonlinear modes in a lattice, and calculate the PN potential for the quadratic nonlinear array for the first time.

Discrete solitons in nonlinear zigzag optical waveguide arrays with tailored diffraction properties.

We show that the discrete diffraction properties of a nonlinear optical zigzag waveguide array can be significantly modified, by exploiting the topological arrangement of the lattice itself. This introduces extended interactions (beyond nearest neighbors), which, in turn, affect the lattice dispersion relation within the Brillouin zone. As a result of this band alteration, we demonstrate that altogether different families of discrete soliton solutions are possible, which are stable over a wide range of parameters. In the regime where instabilities occur, all scenarios are considered in detail. By appropriately engineering the geometrical configuration of the array we find both standing and traveling diffraction-free beams. Our method opens opportunities for diffraction management that can be employed to generate low-power spatial discrete optical solitons.