Defect solitons in two-dimensional photonic lattices with parity-time symmetry

We report the existence and stability of defect solitons (DSs) in two-dimensional parity-time-symmetric photonic lattices with self -focusing Kerr nonlinearity. We analyze the effect of different values of the local defect strength parameter on stability properties of DSs. In the case of a positive defect, the DSs only exist in the semi-infinite gap and can propagate stably in their entire existence domain. For the uniform optical lattices (zero-defect lattices), the DSs also exist only in the semi-infinite gap, but they are unstable upon propagation only in a tiny domain of their existence region, near the edge of the first Bloch band. In the case of a negarive defect, the DSs can exist in both the semi-infinite gap and in the first gap. In the first gap, they are stable only for moderate powers but are unstable for both high- and low-power regimes, near the edges of the first and the second Bloch bands. All DSs in the semi-infinite gap were found to be unstable. Thus the domains of stability can be effecrively controlled by liming the value and sign of the defect strength parameter. (c) 2013 Elsevier B.V. All rights reserved.