Performance tunable passively Q-switched fiber laser based on single-walled carbon nanotubes

Passively Q-switched fiber laser (PQFL) has great potential applications in remote sensing, ranging, and optical communications. However, the PQFLs were seldom studied in view of both theory and experiment. This paper is dedicated to make up for this shortcoming. On the one hand, by describing the coupling rate equations of the PQFL system, the Q-switched pulse output with a modulation frequency of 17.61 kHz and a modulation period of 56.8 μs was obtained at 140 mW pump power. On the other hand, an erbium-doped PQFL whose performance is tunable by controlling the pump power and polarization state was constructed by using a single-walled carbon nanotube (SWCNT) as the saturable absorber (SA). The Q-switched pulse with a repetition rate of 17.61 kHz and a signal-to-noise ratio of 50.2 dB was output at a pump power of 140 mW. The theoretical simulation results were in good agreement with the experimental results. It was also verified from such two aspects that the repetition rate of the output pulse of PQFL was approximately proportional to the pump power. This research promotes the theory and design of PQFL.