We investigate the defect solitons (DSs) in square photonic lattices in biased centrosymmetric photorefractive crystals with saturable self-fousing nonlinearity. We reveal the existence and stable regions of DSs due to the changing defect strength; in particular, DSs appear to be unstable in the first bandgap with high power where the repulsive defect is, which is usually stable in non-centrosymmetric media. The DSs existence and stable regions reduce with the increase of the attractive defect strength in the semi-infinite bandgap. For a repulsive defect, DSs can be profoundly affected by their defect potentials and power.

中文翻译：

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具有饱和自聚焦非线性的偏心对称光折射晶体中二维晶格势支持的缺陷孤子

我们研究具有饱和自融非线性的偏心对称光折射晶体中方形光子晶格中的缺陷孤子（DSs）。由于缺陷强度的变化，我们揭示了DS的存在和稳定区域。特别是，在排斥缺陷所在的高功率的第一带隙中，DS似乎不稳定，通常在非中心对称介质中是稳定的。在半无限带隙中，随着缺陷缺陷强度的增加，DS的存在和稳定区域减小。对于排斥性缺陷，DS可能会受到其缺陷电位和功率的深刻影响。