Conventional soliton or stretched pulse delivered by nanotube-mode-locked fiber laser

We propose a nanotube-mode-locked erbium-doped fiber laser that can deliver conventional solitons (CSs) or stretched pulses (SPs) based on a D-shaped fiber saturable absorber where evanescent-field interaction works. The net cavity dispersion of the laser is slightly negative. In our experiment, by optimizing the polarization controller in the cavity, CS and SP can be obtained at the central wavelengths of 1530.6 nm and 1530.3 nm due to carbon nanotubes and the spectral filtering effect induced by nonlinear polarization rotation. Although the acquired CS and SP nearly have the same central wavelengths, they show distinct optical spectra, 3-dB bandwidths. The proposed fiber laser is attractive for practical applications.