Research on soliton molecule generation with external independent controllable modulation period and pulse width and its gain-managed nonlinear amplification

Soliton molecules offer significant practical advantages in high-speed optical communications and precision spectroscopy. However, owing to limitations inherent in passive generation inside the laser cavity, independently controlling the spectral modulation period and pulse duration remains challenging for a laser based solely on soliton molecules. This work reports the generation and amplification of soliton molecules based on Lyot filtering and gain-managed nonlinear (GMN) amplification, in which the spectral modulation period and pulse duration can be independently and actively tuned outside the laser cavity. The birefringence-based Lyot filter enables precise control over both the spectral modulation period and the inter-pulse separation. GMN amplification effectively suppresses gain narrowing and overcomes the gain-bandwidth limitation, thereby enabling a much broader spectrum and much shorter pulse output. As a principle-based demonstration in our work, the modulation period is varied from 2 nm to 2.7 nm, corresponding to the pulse intervals of 3.68 ps and 3.06 ps, respectively. After GMN amplification, the average powers are amplified to 124.5 mW and 149.7 mW, respectively, and the pulse widths are 154 fs and 164 fs, respectively. Additionally, we conclude that GMN amplification does not alter the inherent spectral modulation period and pulse interval of soliton molecules. Under GMN amplification, soliton molecules also exhibit the same amplification characteristics as conventional pulses, such as asymmetric spectral broadening toward longer wavelengths and the ability to achieve ultrashort pulse durations. To the best of our knowledge, this is also the first demonstration of the pulse dynamics of soliton molecules under GMN amplification.