풫풯-symmetric nonlocal gap solitons in optical lattices.

The existence and stability of 풫풯-symmetric gap solitons in a periodic structure with defocusing nonlocal nonlinearity are studied. It is found that solitons are in general unstable, their instability rate depending on the magnitude of the imaginary potential. For low values of the imaginary potential solitons survive over distances many times the Rayleigh distance, whereas for high values of the imaginary potential solitons develop an oscillatory instability, eventually leading to a transverse drift towards the gain region. [ABSTRACT FROM AUTHOR]