Spectral Broadening of Low Repetition Rate Pulses in a Fibre Gain-Managed Nonlinear Amplifier

Managing the nonlinear phase shifts and generating bandwidths broader than the gain spectrum are the two main challenges of ultrafast fibre lasers, both of which can be addressed by a new amplification method with gain-managed nonlinearity (GMN). The GMN regime is achieved when nonlinear spectral broadening balances gain-shaping. This balance manifests as the absorption of the blue part of the spectrum and the amplification of the red part. Despite running counter to conventional amplifier design rules, this deliberate use of both gain and loss during pulse amplification is a crucial aspect of the GMN regime. In this regime, the pulse and gain spectra evolve together and reshape one another. As a result, the pulse duration can be compressed to sub-100-fs with a spectrum spanning from 1000 to 1150 nm [1].