Diffusion stabilizes cavity solitons in bidirectional lasers

A bidirectional laser is a ring cavity laser in which emission is allowed to occur in the two possible axial directions, say clockwise and counterclockwise. However, the structures reported, did not behave as cavity solitons (CSs), as they could not be written/erased without disturbing other neighboring LSs, which violates the basic requirement for information storage and manipulation. The model proposed is a set of two coupled Ginzburg-Landau equations for the two counter propagating fields. As a transverse coupling mechanism, only diffraction was considered there. We have numerically integrated by means of a split-step method on a grid of 512 spatial points, and considered a flat-top profile for the pumping A in order to take into account the finite transverse extension of the laser excitation. It shows that a minimum value of transverse diffusion is needed to stabilize the structures, and also that it allows to switch them on and off without disturbing neighboring structures. The stabilization mechanism presented here is twofold: Diffusion reduces the parameter region of pulsing LSs allowing for the existence of these structures even in the isotropic cavity; and also converts the LSs in true CSs, as the LSs in an ensemble can be written/erased independently.