Dynamics of Soliton Cascades in Fiber Amplifiers

TL;DR

This paper investigates how femtosecond pulses in fiber amplifiers generate cascades of solitons through Raman effects, producing multiple ultrashort pulses with varying wavelengths.

Contribution

It numerically demonstrates the formation of cascading solitons in fiber amplifiers without soliton fission, highlighting the role of Raman shifts and input pulse parameters.

Findings

Multiple ultrashort pulses are generated at the amplifier output.

The number of pulses depends on total gain and input pulse width.

Cascaded soliton formation occurs without soliton fission.

Abstract

We study numerically the formation of cascading solitons when femtosecond optical pulses are launched into a fiber amplifier with less energy than required to form a soliton of equal duration. As the pulse is amplified, cascaded fundamental solitons are created at different distances, without soliton fission, as each fundamental soliton moves outside the gain bandwidth through the Raman-induced spectral shifts. As a result, each input pulse creates multiple, temporally separated, ultrashort pulses of different wavelengths at the amplifier output. The number of pulses depends not only on the total gain of the amplifier but also on the width of input pulses.