Self-Q-switching and mode locking in a 1.53-μm fiber ring laser with saturable absorption in erbium-doped fiber at 4.2 K

Self-Q-switching and mode locking have been observed for the first time to our knowledge in a 1.53-μm erbium-doped fiber ring laser that has an erbium-doped fiber cooled to 4.2 K as a saturable absorber. The repetition period of the self-Q-switching was 77 μs (13 kHz), which was determined by a gain recovery time of the laser. Cw mode locking was also observed when the pump power was increased to 150 mW. The Q-switching pulse width was approximately 3.3 μs, and the shortest mode-locked width was approximately 20–30 ns.