Deformable Ultrafast Fiber Laser Based on a Delay-Tunable Mach–Zehnder Interferometer

We present a deformable ultrafast fiber laser based on a delay-tunable Mach–Zehnder interferometer, which can generate pulses with adjustable durations spanning from 239 fs to 24.51 ps, as well as dual-color soliton complexes characterized by tunable sub-pulse separations ranging from 2.49 ps to 3.93 ps. The Mach–Zehnder interferometer is accurately modeled by introducing a linear spectral phase difference in the frequency domain. Simulation results fully reproduce the experimental observations, demonstrating that the properties of mode-locked pulses are predominantly governed by the linear spectral phase difference and self/cross-phase modulation effects. Particularly, owing to the time delay in two arms of the Mach–Zehnder interferometer, the temporal profile of dual-color soliton complex varies between adjacent roundtrips. This study elucidates the formation mechanisms of diverse types of pulses in Mach–Zehnder interferometer-based fiber laser, offering a deformable pulse source for applications such as Terahertz wave generation and nonlinear optical imaging.