Passively mode-locked erbium doped fiber laser based carbon nanotube saturable absorber with MHz fundamental repetition rate: An experimental study

The purpose of this study is to compare the performance of single-mode fiber SMF and few-mode step index fiber FMF in terms of the influence of dispersions towards the cavity ring. A mode-locked fiber laser based on single-walled carbon nanotube saturable absorber (SWCNTSA) is demonstrated with 0.5 m gain medium of highly erbium-doped fiber EDF with peak absorption rate of 110 dB/m at 1530 nm. SMF and FMF; both with 1.5 m in length is applied into the cavity respectively. The total length of the laser cavity with presence of SMF and FMF are 26 m and 25 m respectively. Both laser cavities are able to generate mode-locked solitons, with the central wavelength of the spectrum ranges from 1561.4 nm to 1562.2 nm and repetition rate ranges from 8.10 MHz to 8.24 MHz. The dispersion difference occurred in FMF and SMF does not affect the generated shape of the mode-locked spectrum. By and large, throughout the result, FMF have remarkably less nonlinearity and simultaneously shows similar performance as SMF in terms of dispersion and loss.