DEFECT LATTICE SOLITONS IN TWO-DIMENSIONAL KERR MEDIA

We report on the existence and stability of two-dimensional fundamental defect solitons in optical lattices based on both focusing and defocusing Kerr media. It is found that in focusing Kerr media, for positive defect, the solitons only exist in the semi-infinite gap; for negative defect, the solitons may stably exist in the semi-infinite and the first gaps. In contrast, in defocusing Kerr media, for positive defect, the solitons exist in both the first gap and semi-infinite gap; while for negative defect, the solitons only exist in the first gap. Additionally, for zero defect, solitons only exist in the semi-infinite gap for focusing media and only exist in the first gap for defocusing media.