Dark optical solitons: generation, propagation, and amplification

Abstract

As indicated by our recent publications,1,2 dark solitons are found to have better stability against loss and noise. However, due to the difficulty in obtaining dark pulses, only dark solitons under decaying background have been produced, where complex laser systems and pulse shaping apparatus have to be used. In this talk we propose a novel method for generating dark solitons with cw background, including simulated outputs showing effects of system parameter variations. The input to our proposed device is a cw optical beam, the output is a train of odd dark solitons on a cw background. We also show that for a nonsoliton input in the normal dispersion regime of an optical fiber, the central pulse will evolve into a primary soliton having the same amplitude and speed as the input, but with different pulse width. The generated secondary solitons, having smaller amplitudes and larger pulse widths, will move away from the primary pulse at varying speeds. The dark solitons preserve their shape after collision and have unique coupling properties, to be described in detail. Finally, we show how a dark soliton pulse train propagating in a lossy fiber can retain its shape by periodic amplification using the stimulated Raman scattering process.