Coupled tapering/uptapering of dark soliton pair in nonlinear media

Tapering/uptapering of coupled dark solitons of two coaxially co-propagating mutually incoherent beams in a nonlinear medium in presence of small gain or loss has been investigated in this paper using Beam Propagation Method (BPM), i.e., by direct simulations of the underlying Nonlinear Schrödinger Equation (NLSE). The results are compared with the earlier published results of tapering/uptapering of coupled bright solitons. It is found that in contrast to uptapering of bright solitonic pair, dark solitonic pair tapers in presence of losses. Moreover, in contrast to the possibility of tapering as well as uptapering of a bright solitonic pair, a dark solitonic pair never undergoes uptapering.