The influence of saturable absorber parameters on the operation regimes of a dumbbell-shaped thulium fibre laser is studied. As saturable absorbers, polymer films with nanotubes characterised by different transmission coefficients in the saturated and unsaturated states are used. The operation of lasers with absorbers of different configurations used to obtain stable Q-switching and mode-locking regimes in the spectral range 1930 – 1960 nm is demonstrated. The average output power in the single-pulse mode-locking regime is 3.5 mW at a pulse repetition rate of 8.4 MHz and a pulse duration of 1.08 ps.

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Octave-spanning supercontinuum conversion in three different rare-earth doped fiber amplifiers have been investigated. Using an erbium amplifier, it turned out to increase the output power to 445 mW with a spectral width of 1250 nm. For a thulium amplifier, an average output power of 390 mW and a spectral width of 569 nm was obtained. Additionally, for holmium, the average output power was 724 mW with a spectral width of 450 nm. For all cases, the output pulses envelope did not exceed 0.72 ns.

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