Laser is one of the greatest inventions of human science and technology in the 20th century. The emergence of lasers not only greatly promotes the development of related science and technology, brings forth new disciplines such as nonlinear optics, laser spectroscopy, ultra-strong and ultra-fast optics, laser materials and laser physics, but also has a great and far-reaching impact on many aspects of human life.
As a kind of laser source, fiber laser has the advantages of small size, high time/space coherence, high conversion efficiency and good heat dissipation. With the rapid development of optical fiber manufacturing and laser technology, the output power and pulse energy of fiber laser can be comparable to that of solid state laser. Therefore, fiber laser is considered as the next generation of high quality max laser source
Generally speaking, in order to generate ultrashort pulses of FS and PS magnitude in fiber lasers, a simple and effective way is to use passive mode-locking technology. The passive mode-locking techniques commonly used by researchers include non-linear polarization rotation (NPR), non-linear optical amplifier loop (NALM), real saturable absorber and so on. When a fiber laser operates in a stable mode-locked state, its output mode-locked pulse can generally be called soliton pulse. As early as 1973, A. Hasegawa and F. Tappert theoretically predicted that optical fibers could support the transmission of optical solitons. In 1980, F. Mollenauer et al. first confirmed the existence of optical solitons in experiments. However, the study of soliton properties in optical fiber lasers began in the 1990s.
Unlike optical soliton transmission in optical fibers, fiber lasers have periodic gain amplification and output loss, which is a non-conservative dissipative system. It is precisely because of this dissipative structure that the soliton pulses of ultrafast fiber lasers tend to evolve into new soliton shapes or exhibit complex non-linear dynamic characteristics under specific conditions. The results show that the discovery of new soliton nonlinearity is of great significance for both industrial applications and basic scientific research.