In addition to the generation and characterization of structured laser beams, their propagation becomes especially relevant not only for transporting pulses to potential experiments but also for modifying their properties. For over a decade, USAL has been a pioneer in the development of theoretical methods that allow understanding the propagation of ultrafast laser pulses in highly nonlinear media across different spectral regions (far-infrared, infrared, and ultraviolet). In particular, during this period, it has specialized in the study of the nonlinear propagation of light pulses in gas-filled hollow fibers, which can be structured based on the superposition of transverse modes. Noteworthy are the collaborative works with Prof. Helder Crespo at the University of Porto (Portugal), where ultrarapid single-cycle pulses have been achieved [Opt. Lett. 43, 337 (2018), >50 citations; Sci. Rep. 8, 2256 (2018), >40 citations].