Passively Q-switched erbium doped fiber laser based on double walled carbon nanotubes-polyvinyl alcohol saturable absorber

A passively Q-switched Er-doped fiber laser with a ring cavity operating at 1568.6 nm is demonstrated using a saturable absorber based on a double walled carbon nanotubes film, which is prepared using polyvinyl alcohol as a host polymer. The Q-switching operation is achieved at a low pump threshold of 40 mW. The proposed fiber laser produces stable pulses train of repetition rate ranging from 14.7 KHz to 47 KHz as the pump power increases from threshold to 203 mW. The minimum recorded pulse width was 4.6 µs at 203 mW, while the highest energy obtained was 102.1 nJ.