Pulse characterization of a mode-locked fiber laser based on a carbon nanotube saturable absorber

A passively harmonic mode-locked erbium-doped fiber ring laser was demonstrated by using single-walled carbon nanotube as a saturable absorber. By pumping with a 980 nm wavelength laser diode and adjusting the polarization controllers inside the fiber cavity, we obtained a soliton pulse train with a repetition rate of 9.33 MHz. We were able to increase the pulse repetition rate to 140 MHz, the 15th harmonic of the fundamental mode-locking frequency. The cavity supermodes were suppressed by 55 dB. Soliton pulses were generated with a center wavelength of 1562 nm and a linewidth of 4.2 nm. The pulse width measured by using second harmonic generation frequency resolved optical gating was 720 fs, and the time-bandwidth product was 0.371.