Spatial beam dynamics mediated by Hybrid nonlinearity

We provide a brief overview of recent progresses on the study of a new type of nonlinearity, named hybrid nonlinearity: the coexistence of self-focusing and self-defocusing nonlinearities in the same material under identical conditions. Such hybrid nonlinearity is established in a nonconventionally biased photorefractive crystal, which offers enhanced anisotropy and nonlocality, leading to a variety of unusual nonlinear beam dynamics in both continuous and discrete regimes. In homogenous media, elliptical optical solitons, stabilization of nonlinear optical vortices, as well as orientation-induced transition between bright and dark solitons are demonstrated. In discrete media, hybrid nonlinearity enables the creation of an ionic-type photonic lattice with alternating positive and negative optical potentials, which in turn enables the reconfiguration of lattice structures and Brillouin zones for band-gap engineering and light manipulation. Moreover, a host of nonlinear discrete localized states mediated by such hybrid nonlinearity are uncovered, including elliptical discrete solitons and "saddle" solitons. The novel concept of hybrid nonlinearity opens a door for exploring spatial beam dynamics and related nonlinear phenomena in anisotropic nonlinear systems beyond optics.