Carbon nanotubes (CNTs) possess both remarkable optical properties and high potential for integration in various photonic devices. We overview, here, recent progress in CNT applications in fibre optics putting particular emphasis on fibre lasers. We discuss fabrication and characterisation of different CNTs, development of CNT‐based saturable absorbers (CNT‐SA), their integration and operation in fibre laser cavities putting emphasis on state‐of‐the‐art fibre lasers, mode locked using CNT‐SA. We discuss new design concepts of high‐performance ultrafast operation fibre lasers covering ytterbium (Yb), bismuth (Bi), erbium (Er), thulium (Tm) and holmium (Ho)‐doped fibre lasers.

We present a thulium-doped fiber laser mode-locked by a carboxymetylcellulose high-optical quality film with dispersed single-walled carbon nanotubes. Laser system based on the nonlinear amplifying loop mirror generates the shortest pulses earlier obtained in SWCNT mode-locked thulium-doped fiber lasers with a duration of 450 fs and 18 mW maximum average power at 1870 nm.

We have proposed and demonstrated a Q-switched Thulium doped fibre laser (TDFL) with a ‘Yin-Yang’ all-fibre cavity scheme based on a combination of nonlinear optical loop mirror (NOLM) and nonlinear amplified loop mirror (NALM). Unidirectional lasing operation has been achieved without any intracavity isolator. By using a carbon nanotube polymer composite based saturable absorber (SA), we demonstrated the laser output power of ~197 mW and pulse energy of 1.7 μJ. To the best of our knowledge, this is the highest output power from a nanotube polymer composite SA based Q-switched Thulium doped fibre laser.

The complex nonlinear dynamics of mode-locked fibre lasers, including a broad variety of dissipative structures and self-organization effects, have drawn significant research interest. Around the 2 μm band, conventional saturable absorbers (SAs) possess small modulation depth and slow relaxation time and, therefore, are incapable of ensuring complex inter-pulse dynamics and bound-state soliton generation. We present observation of multi-soliton complex generation in mode-locked thulium (Tm)-doped fibre laser, using double-wall carbon nanotubes (DWNT-SA) and nonlinear polarisation evolution (NPE). The rigid structure of DWNTs ensures high modulation depth (64%), fast relaxation (1.25 ps) and high thermal damage threshold. This enables formation of 560-fs soliton pulses; two-soliton bound-state with 560 fs pulse duration and 1.37 ps separation; and singlet+doublet soliton structures with 1.8 ps duration and 6 ps separation. Numerical simulations based on the vectorial nonlinear Schr¨odinger equation demonstrate a transition from single-pulse to two-soliton bound-states generation. The results imply that DWNTs are an excellent SA for the formation of steady single- and multi-soliton structures around 2 μm region, which could not be supported by single-wall carbon nanotubes (SWNTs). The combination of the potential bandwidth resource around 2 μm with the soliton molecule concept for encoding two bits of data per clock period opens exciting opportunities for data-carrying capacity enhancement.

We present an SESAM mode-locked thulium-doped fiber laser incorporating nonlinear amplifying loop mirror with intracavity and external group velocity dispersion control, which generates sub-300-fs near-transform-limited pulses at 1920-nm wavelength, with 106-mW maximum average output power. The dispersion control was realized by implementing a low-loss highly doped germanium silica fiber.

Ultrashort pulse generation at the short-wave infrared (SWIR) wavelength ranges from 1.6 to $2.5\mu \mathrm{m}$ and together with benefits of the all-fiber design has transformed lasers into an essential tool for industrial, technological, scientific, environmental, and medical applications. With the development of pumping sources and fiber components, ultrafast SWIR fiber lasers have drawn exceptional research and industrial attention over the last decade, resulting in the achievement of comparable performance or even surpassing well-established near-IR sources. Exceptionally compact, highly stable, cost-effective, and maintenance-free ultrafast fiber lasers operating at the SWIR range are currently well on the way to be commercially employed. This invited Perspective article gives a comprehensive overview of the most significant achievements enabling ultrafast generation at SWIR, including up-to-date gain fibers and saturable absorbers, nonlinear process, and laser architectures. This article highlights the perspectives and strategies for further maturing of the field of SWIR fiber lasers and pathways for the improvement of the performance, overcoming existing bottlenecks and challenges toward reducing pulse durations, tunability of repetition rate, and power upscaling. The advancement of the ultrafast SWIR laser development is projected until the landscape of existing technologies, driven by these ultimate sources, and potential applications, emerging on the horizon.