Dissipative solitons for mode-locked fibre lasers
High-energy ultrashort laser pulses at various wavelengths are necessary for a wide variety of scientific as well as industrial applications. Possessing advantages like compactness and robustness, fibre lasers are considered as attractive candidates for the generation of ultrashort laser pulses. To date, however, fibre lasers lag behind their solid-state counterparts in pulse power and duration. To improve the performance of fibre lasers, different mode-locking mechanisms have been proposed, including dispersion-managed solitons, similaritons and dissipative solitons. EU-funded researchers explored the use of dissipative-solitons mode-locking. Within the project DISCANT (High-energy dissipative soliton dispersion-managed fibre laser based on carbon nanotubes), they searched for ways to exploit this mechanism ensuring a good balance between nonlinearity and dispersion but also gain and losses." After numerically analysing the inter-cavity pulse dynamics, the researchers proposed the use of single-walled carbon nanotubes (SWNTs). Combining SWNTs of different diameters and chiralities can enable the development of mode-locked fibre lasers that are tunable over a broad range of wavelengths. SWNTs exhibit optical non-linearity, short carrier relaxation time and high damage threshold. Even for a wavelength detuning within hundreds of nanometres, appreciable optical saturable absorption is still observed. These features imply a great potential for wideband tunable lasers. Researchers paid particular attention to dissipative solitons in an all-fibre ytterbium-doped fibre laser with SWNT-based mode locker. With optimal cavity dispersion, the oscillator could generate 8.4 picosecond pulses. Through further compression outside the cavity, pulses as short as 118 femtoseconds were attained. Experimental operation confirmed the validity of the initial proposal. The DISCANT project results did not only advance our understanding of mode-locked fibre lasers, an important step has been made in achieving high-energy ultrashort laser pulses of importance for a broad range of applications.
Keywords
Dissipative solitons, mode-locked, fibre lasers, carbon nanotubes, ultrashort laser pulses, DISCANT
