Multi-wavelength Q-switched erbium-doped fibre laser using saturable absorber based on carbon nanotube film

Abstract

A stable passively Q-switched multi-wavelength erbium-doped fibre laser operating near 1533.5 nm is demonstrated using a saturable absorber based on single-walled carbon nanotube film, which is prepared using polyvinyl alcohol as a host polymer. The laser achieves a multi-wavelength oscillation regime as a result of nonlinear polarization rotation effect, which overcomes unstable mode competition in the ring cavity. It generates a stable multi-wavelength comb of seven lines, with the wavelength spacing of 0.10 nm at the pump power 64 mW. At the same pump power, the laser produces a stable pulse train with the repetition rate 13.1 kHz, the pulse width 7.2 μs and the pulse energy 21 nJ. A high performance of our Qswitched laser is achieved by optimizing the saturable absorber and the laser cavity.