Revealing Optical Soliton Radiation and Encoding via Nonlinear Fourier Transform

Abstract

Mode-locked lasers exhibit a rich diversity of nonlinear dynamics, often featuring the nontrivial coexistence of linear dispersive waves and coherent structures, especially in transient evolution involving multiple soliton pulses. The coexistence of solitons and an embedded dispersive wave background sets a challenge for characterizing and analyzing these transient dynamics. Here, we demonstrate the real-time full-field characterization of transient soliton dynamics in a mode-locked fiber laser using nonlinear Fourier transform (NFT) and high-bandwidth coherent homodyne detection, revealing new insights into the physics of optical soliton interactions within complex nonlinear systems. Such characterization includes the formation of multiple solitons amid wide relaxation oscillations, the switching of multiple solitons, and controlled soliton drifting with associated digital encoding. NFT proves its efficiency in separating and analyzing coherent structures among the dispersive wave radiation in fiber lasers. By implementation of the inverse NFT, the corresponding pure soliton distribution can be reconstructed. These findings shed new light on ultrafast transient dynamics in optics.