Passively gain-switched and self mode-locked thulium fiber laser at 1950 nm

• A CW-pumped, passively gain-switched and self-mode-locked Tm3+ laser is proposed.
• A Tm3+ fiber was the gain medium and saturable absorber in the coupled resonators.
• 2 μm self mode-locking in Tm3+ pumped at 1.57 μm was for the first time observed.
• Self mode-locked pulsing at 1950 nm with a peak power of 250 W was achieved.

We propose and demonstrate a CW-pumped, passively gain-switched and self-mode-locked thulium fiber laser at 1950 nm. In the system, a thulium fiber served as a saturable absorber Q-switch in a 980 nm pumped erbium fiber resonator and was intra-cavity excited by the self-induced Q-switching resonance at 1570 nm. A coupled 1950 nm resonator including the gain-switched thulium fiber was self mode-locked with a pump threshold of 70 mW. The mode-locked pulses had a maximum peak power of 250 W and a pulse duration of 720 ps.