Generation of Soliton Molecules in an All-Normal Dispersion Yb-Doped Fiber Laser with a Lyot Filter

Soliton molecules offer practical advantages in high-speed optical communication, precision spectroscopy, and micromachining. In all-normal dispersion fiber lasers, group velocity dispersion broadens the pulse duration, hindering the attainment of the nonlinearity dispersion balance essential for soliton molecule formation. Consequently, the generation of soliton molecules in such lasers is a technically demanding task. Here, we report an all-normal dispersion fiber laser, mode-locked via nonlinear polarization evolution (NPE) and Lyot filtering. By adjusting the intracavity polarization, this setup allows direct control over pulse interactions, enabling the generation of stable soliton molecules, soliton bound states, and multipulse states. A spectral modulation period of up to 0.95 nm is achieved. In addition, different types of solitons, such as soliton singlets and soliton molecules in tightly and loosely bound states, are observed.