Spatiotemporal analysis of an all-fiber multimode interference-based saturable absorber via a mode-resolved nonlinear Schrodinger equation

Abstract

This paper presents an approach that combines the generalized multimode nonlinear Schrodinger equation with a transmission model to analyze spatiotemporal characteristics of multimode interference in single mode/large mode area fiber–graded-index multimode fiber–single mode fiber (SMF/LMA-GIMF-SMF) structures for the first time. Approximated self-imaging (ASIM) behavior in GIMF and the study of the latter structure used in spatiotemporal mode-locked fiber lasers are first demonstrated. Simulations show that these structures can work as saturable absorbers enabling high-energy pulse output due to nonlinear intermodal interactions and intensity-dependent multimode interference. Otherwise, underlying ASIM is proven that it can perturb the transmission of SMF/LMA-GIMF-SMF, causing instability of their saturable-absorption characteristics. This paper provides a theoretical guide for many applications, such as beam shaping, mode conversion, and high-energy ultrafast fiber laser.

A 301 W narrow-linewidth in-band pumped Er:Yb co-doped fiber amplifier at 1585 nm and related modeling for dynamics study and optimization

“…, , The power propagation equations in EYDF are written as follows: Where a is the radius of the fiber core. Due to the high output power and noise pulse in EYDF, the multimode nonlinear Schrodinger equation is applied [30][31][32]. The equation considers dispersion and nonlinear effects for simulating spectral nonlinear broadening and intermodal coupling.…”

Spatiotemporal mode-locking and dissipative solitons in multimode fiber lasers

“…As mentioned above, all-fiber designs offer a viable solution to lower losses and increase the output power. Indeed, nonlinear multimode interference (NL-MMI) filter using a SMF-MMF-SMF structure [167][168][169] can be used as a spectral and spatial filter for STML in MMF lasers 19,63,82,170,171 . By precisely tuning the NL-MMI filter, tunable dual-wavelength STML can be realized with two wavelength emissions showing distinct characteristics 170 .…”