Metallic carbon nanotube-based saturable absorbers for holmium-doped fiber lasers

In 2003, carbon nanotubes opened a new field of research on nanomaterial-based mode-locked fiber lasers. They maintain popularity in the ultrafast laser community due to their broadband operation, relatively high damage threshold, and tunable optical properties. Here we show that metallic carbon nanotube-based thin film fabricated by vacuum filtration technique can be used as a saturable absorber in holmium-doped fiber laser operating in anomalous and normal dispersion regimes. Scaling the absorbers modulation depth by adjusting the film thickness was observed. The Fourier transform limited 6.65 nm wide optical solitons in anomalous dispersion regime were generated. Utilizing stretched-pulse regime greatly improves the laser performance - 212 fs pulses reach the energy of 3.79 nJ.