Defect solitons in optical lattices with parity-time symmetric defect

Abstract

The existence and stability of defect solitons in optical lattices with parity-time (PT) symmetric defect are reported. For positive or zero defects, in-phase solitons and out of phase solitons can exist stably in the semi-infinite gap and the first gap, respectively. For negative defects, in-phase solitons can be stable in both the semi-infinite gap and the first gap, whereas out of phase solitons are unstable in the first gap. For in-phase solitons with positive defect in the semi-infinite gap and negative defect in the first gap, there exists a cutoff point of the propagation constant below which the defect solitons vanish. The imaginary parts of the PT-symmetric defect potentials deeply affect the stability of solitons.