Formation of a Standing-Light Pulse through Collision of Gap Solitons

Abstract

Results of a systematic theoretical study of collisions between moving solitons in a fiber grating are presented. Various outcomes of the collision are identified, the most interesting one being merger of the solitons into a single zero-velocity pulse, which suggests a way to create pulses of ``standing light". The merger occurs with the solitons whose energy takes values between 0.15 and 0.35 of the limit value, while their velocity is limited by about 0.2 of the limit light velocity in the fiber. If the energy is larger, another noteworthy outcome is acceleration of the solitons as a result of the collision. In the case of mutual passage of the solitons, inelasticity of the collision is quantified by the energy-loss share. Past the soliton's stability limit, the collision results in strong deformation and subsequent destruction of the solitons. Simulations of multiple collisions of two solitons in a fiber-loop configuration are performed too. In this case, the maximum velocity admitting the merger increases to about 0.4 of the limit velocity. Influence of an attractive local defect on the collision is also studied, with a conclusion that the defect does not alter the overall picture, although it traps a small-amplitude pulse. Related effects in single-soliton dynamics are considered too, such as transformation of an input sech signal into a gap soliton (which is quantified by the share of lost energy), and the rate of decay of a quiescent gap soliton in a finite fiber grating, due to energy leakage through loose edges.