Ultrafast all-anomalous-dispersion Er-doped large-mode-area fiber lasers

Ultrafast Er-doped large-mode-area (LMA) fiber lasers are demonstrated in the all-anomalous-dispersion regime. With the assistance of a home-made carbon nanotube saturable absorber, stable and chirp-free solitons are always observed for output coupling ratios (OCRs) varying from 10% to 90%, leading to the simultaneous achievement of the maximum pulse energy and minimum pulse duration at the OCR of 70%. To validate the universality of the all-anomalous-dispersion mode-locking, an all-fiber saturable absorber based on nonlinear multimode interference effect is incorporated into the LMA fiber laser cavity, which can also generate chirp-free solitons. The influences of gain fiber dispersion on solitons are numerically simulated, revealing that the dispersion consistency of fibers in the laser cavity is in favor of generating stable and chirp-free solitons even at an ultrahigh OCR. This work paves the way for ultrafast Er-doped LMA fiber lasers in the all-anomalousdispersion regime, which provides an alternative route to further improve the stability and output pulse energy of ultrafast LMA fiber lasers, i.e. ensuring the dispersion consistency and hence enlarging the OCRs.

Automated summary

This paper demonstrates ultrafast Er-doped large-mode-area (LMA) fiber lasers in the all-anomalous-dispersion regime, achieving stable and chirp-free solitons with the assistance of a homemade carbon nanotube saturable absorber. The universality of all-anomalous-dispersion mode-locking is validated by incorporating an all-fiber saturable absorber based on nonlinear multimode interference effect, which also generates chirp-free solitons. The numerical simulation reveals that the dispersion consistency of fibers in the laser cavity is beneficial for generating stable and chirp-free solitons even at an ultrahigh output coupling ratio (OCR).