Soliton dynamics in one-dimensional waveguide arrays with saturable, self-defocusing nonlinearity

The last two decades have witnessed a strong interest in periodic optical systems, such as waveguide arrays and photonic crystals [1, 2]. These systems exhibit many attractive features for which no counterpart exists in homogeneous media, including forbidden gaps in their transmission spectra [3], existence of strongly localized nonlinear modes (discrete and gap solitons) and the exciting possibility of controlling diffraction. One-dimensional waveguide arrays consisting of evanescently coupled parallel channels are fabricated in various photorefractive materials, including photovoltaic lithium niobate crystal possessing saturable self-defocusing nonlinearity [4] that is responsible for solitons’ stabilization and their enhanced mobility [5]. We analyze both experimentally and theoretically soliton dynamics in two types of photonic lattices: in uniform waveguide arrays with locally introduced coupling defect [6, 7] and in more complex, binary lattices with alternating spacing between channels of constant width [8, 9]. Coupling defect interrupts the lattice periodicity and offer an additional physical mechanism for light confinement, acting as a waveguide in whose vicinity light can be confined, causing the existence of the so-called, defect modes inside the bandgaps. On the other hand, an extra periodicity opens an additional mini-gap where light propagation is again forbidden, thus allowing for extended nonlinear interaction of light with binary lattices and existence of novel, stable types of lattice solitons that may be potentially useful for the development of future all-optical photonic devicesSymposium Nonlinear Dynamics - Milutin Milanković, Multidisciplinary and Interdisciplinary Applications : 8th Serbian Symposium in area of Non-linear Sciences : October 1-5, 2012, Belgrad