Ultrashort pulses delivered from mode-locked fiber lasers have extensive ultrafast applications in industry and science. These short pulses can also self-assemble and bind to form soliton molecules (SMs), which are endowed by the balanced interaction forces. Studies on transient SM dynamics raise the question of how far the “molecular” analogy reaches—that is, whether diverse dimensions of SMs can be controllably driven or manipulated. However, comprehensive and precise manipulation of the multiple properties of SMs in a real-time manner has remained a challenge and largely unexplored in experiments. Moreover, due to the lack of analytic relationship between cavity parameters and specific soliton operations, the problem of repeatability has also hampered the possibility of obtaining an augmented subspace of desired SM states through tuning intracavity parameters.

The image on the cover for Advanced Photonics Nexus Volume 4 Issue 1 illustrates the intelligent control of soliton molecules in a $2\text{-}\mu \mathrm{m}$ mode-locked fiber laser by combining an evolution algorithm and electronic polarization controller. Depending on the specifications of the merit function used for the optimization procedure, various soliton molecule operations can be obtained. The image is based on original research presented in the article “Intelligent soliton molecules control in an ultrafast thulium fiber laser,” by Yi Zhou, Kangwen Yang, Kevin K. Tsia, Heping Zeng, and Kenneth K. Y. Wong (doi: 10.1117/1.APN.4.1.016012).