Spatiotemporal mode decomposition of ultrashort pulses in linear and nonlinear graded-index multimode fibers

We develop a spatiotemporal mode decomposition technique to study the spatial , temporal mode power distribution of ultrashort pulses in long spans of graded-index multimode fiber, for different input laser con-ditions. We find that the beam mode power content in the dispersive pulse propagation regime can be described by the Bose-Einstein law, as a result of the process of power diffusion from linear and nonlinear mode coupling among nondegenerate mode groups. In the soliton regime, the output mode power distribution approaches the Rayleigh-Jeans law.(c) 2023 Chinese Laser Press

Automated summary

We developed a spatiotemporal mode decomposition technique to analyze the power distribution of ultrashort pulses in graded-index multimode fibers. Our findings reveal that the power content of beam modes in the dispersive pulse propagation regime follows the Bose-Einstein law, which is a result of power diffusion from mode coupling. In the soliton regime, the output mode power distribution approaches the Rayleigh-Jeans law.