Dark solitons with asymmetric background in nonlinear waveguide arrays

Summary form only given. During the past several years discrete optical systems, i.e., nonlinear coupled waveguide arrays, have attracted a considerable deal of interest. Recently, the existence of localized modes, or discrete solitons (DS), in such arrays has been experimentally verified. Moreover, their potential application for all-optical steering and routing could be demonstrated in AlGaAs waveguide arrays. These experiments as well as numerous theoretical studies imply that discrete solitons may distinguish fundamentally from their continuous counterparts. Apart from bright DS dark localized modes may exist in an array with either focusing or defocusing nonlinearity. However, until now only symmetric DS with equal backgrounds or shock waves with zero background have been identified. We show that discreteness may support different mechanisms of localization. As a consequence dark DS with an asymmetric background and shock waves with finite background may form.