We demonstrate self-trapping of light by simultaneously compensating normal and anomalous (saddleshaped) diffractions with self-focusing and self-defocusing hybrid nonlinearity in optically induced ionic-type photonic lattices. Innovative two-dimensional gap solitons, named "saddle solitons," are established, whose phase and spectrum characteristics are different from all previously observed spatial solitons. © 2009 Optical Society of America OCIS codes: 190.6135, 190.5330, 350.4238. Despite the discovery of a variety of soliton entities in discrete systems [1], to our knowledge, it has not been possible to demonstrate a two-dimensional (2D) spatial soliton in a physical arrangement where an optical beam exhibits simultaneously normal and anomalous diffractions in different transverse directions. First, natural materials typically are not endowed with a saddle-shaped bi-diffractive property; second, it remains a challenge to find a nonlinear material that can support hybrid self-focusing and selfdefocusing nonlinearities without changing experimental conditions. Previous work on nonlinear X waves and light bullets was aimed toward balancing of beam diffraction and pulse dispersion simultaneously, but in spatial domain alone compensation of normal and anomalous diffractions in the same experimental setting has not been realized. Man-made periodic structures have shown many intriguing optical properties. In an optically induced 2D square lattice [2][3][4], for example, the highsymmetry X point in the first Bloch band is akin to a saddle point in diffraction spectrum [see Fig. 1(c)], where normal and anomalous diffractions coexist along orthogonal directions [5]. At this X point, a quasi-1D soliton train can be excited provided that an appropriate type of nonlinearity is used to balance beam diffraction in one particular direction, whereas in the orthogonal direction it is an extended plane wave [6]. The propagation constant of such a 1D soliton train could reside within the first Bloch band, thus named "in-band" or "embedded" solitons [7]. However, to simultaneously balance normal and anomalous diffractions for self-trapping of a 2D-localized optical beam, one needs orientationdependent hybrid nonlinearity. Fortunately, such nonlinearity was found in our recent work with photorefractive nonlinear crystals under nonconventional bias (NCB) condition [8][9][10], in which coexistence of self-focusing and self-defocusing nonlinearities at two orthogonal directions has led to observation of controlled 1D soliton transition from different band edges or subband edges.In this Letter, we employ the hybrid nonlinearity to demonstrate a type of spatial gap solitons, namely, "saddle solitons," by balancing the saddle-shaped diffraction in an optically induced 2D ionic-type lattice [10]. Such solitons have propagation constant residing in the Bragg reflection gap, but they differ from all previously observed solitons supported by a single self-focusing or self-defocusing nonlinearity. In addition, quasi-localized 2D in-band...