Introduction

This chapter introduces the concept of solitons and their interactions, highlighting the formation of soliton molecules. It also discusses the research on polyatomic soliton molecules (PSMs) in a fiber laser with near-zero group velocity dispersion (ZGVD). The results include various observed PSMs and their formation mechanisms. The work is important in understanding the interaction dynamics of large soliton molecular complexes and may have practical applications in multiple encoding, supercontinuum generation, and all-optical bit storage.

Results

The experimental studies were conducted in a quasi-vectorial cavity fiber laser, in which no saturable absorber existed. By controlling the cavity dispersion close to the zero group velocity dispersion (ZGVD) point, the laser was able to form scalar dark solitons (DSs) and bound solitons (BSs). Additionally, experiments showed that scalar DSs and BSs could be simultaneously formed along the same polarization axis under certain conditions. Theoretical predictions on vector dark-bright solitons and their formation were also discussed, including the formation of ordinary dark-bright solitons (ODBS) made of orthogonally polarized dark-bright solitons, which had not been previously observed. Trapping of scalar DSs and BSs to form soliton molecules, specifically (1 + 1) polyatomic soliton molecules, was successfully achieved in the fiber laser.

Discussion

The chapter discusses the formation of different types of solitons in a fiber laser, including bright solitons (BSs) and dark solitons (DSs). It is shown that fundamental DSs can be easily generated in a fiber laser without a saturable absorber (SA) in the cavity, and the fiber laser can also operate close to the zero group velocity dispersion (ZGVD) point to form simultaneous BSs and DSs. The interaction between different types of solitons is also explored, with the potential to create large optical molecules. The development of compound soliton molecules is discussed, and the practical significance of this concept in enriching control schemes for optical soliton molecules is highlighted. The potential for the formation of higher-dimensional spatiotemporal solitons is also mentioned, which could advance the understanding of soliton formation and dynamics in complex three-dimensional systems.

Materials and methods

This chapter describes the experimental setup and measurement system used in the study. The fiber ring cavity consists of different segments of fibers, including EDF, DCF, and stand SMF, and the net cavity dispersion is tuned to the vicinity of the ZGVD point. More details on the experimental parameters and measurement systems can be found in Supplementary Section 1.

Acknowledgements

The chapter discusses the sponsorship of the research by the Singapore Ministry of Education and the National Natural Science Foundation of China.

Data availability

The data that support the simulations within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

Conflict of interest

The authors declare no competing interests.

Supplementary information

This chapter contains supplementary material for the paper available at the given DOI.