Pulse-State Switchable Fiber Laser Mode-Locked by Carbon Nanotubes

We proposed a carbon nanotube (CNT) mode-locked fiber laser delivering chirp-free soliton (CFS) and chirped pulse (CP) simultaneously or separately based on a circulator and chirped fiber Bragg grating (CFBG). The CFS reflected by the CFBG exhibits spectral sidebands with a bandwidth of 0.27 nm, whereas the CP has a smooth spectrum with a bandwidth of 4.1 nm. The durations of the CFS and CP are 9.6 and 1.3 ps, respectively. Due to the large anomalous dispersion and spectral filtering of CFBG, the CFS maintains low intensity and accumulates high energy without wave breaking. Numerical simulations agree well with the experiment and confirm the strong pulse shaping ability of CNT. The operation-switchable fiber laser may facilitate the practical applications where multitype pulses are necessary.