Mode-locking and self-mode-locking-like operation in a resonantly pumped gain-switched Tm-doped fiber laser

Mode-locking and mode-locking-like operation in a fast gain-switched Tm-doped fiber laser have been investigated experimentally. Applying a SESAM mirror, stable gain-switched and regular mode-locked pulses at a wavelength of similar to 2 mu m are reported. The repetition rates of the gain-switched pulses and mode-locked subpulses are 50 kHz and 111 MHz, respectively. The duration of subpulses recorded within one gain-switched pulse envelope is similar to 110 ps. Besides, in the same laser system configuration, it has been found that self-starting mode-locked resembling pulses, attributed to mode beating, can be generated. To the best of our knowledge, it is the first report on a gain-switched fiber laser where both modes of operation have been demonstrated.