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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.

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Abstract.A stable passively Q-switched erbium-doped fibre laser (EDFL) operating at 1536.5 nm is developed, using a 1 m long erbium-doped fibre as a gain medium and a simple graphene-based saturable absorber (SA). Using mechanical exfoliation, a single layer of graphene is obtained and deposited on the end facet of an optical fibre ferrule, which is then connected to another ferrule to form the SA. The SA is integrated into an EDFL cavity to achieve a stable pulse train at the threshold pump power of 42.3 mW. When the pump power increases from 42.3 to 63.5 mW, the pulse train repetition rate increases from 10.3 to 32.4 kHz, while the pulse width varies from 10.7 to 31.0 μs. The highest energy, 166.2 nJ, is achieved at the pump power of 42.3 mW.