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In this letter, the experimental results on a supercontinuum signal are presented based on a significantly broad and highly flat final spectrum (∼810 nm and less than 3 dB). The supercontinuum was induced by two different microstructures in photonic crystal fibers (PCFs) with solid cores, pumped in the nanosecond regime (large pulses) by a Q-switched Nd:YAG laser. The simultaneous presence of both PCFs allowed an optimized spectrum to be obtained in comparison with the work reported in recent papers. The spectral evolution of a pump pulse propagating into the two PCFs was analyzed experimentally and the dispersion in the PCFs was estimated through numerical simulations. The broadening of the final spectrum was related to nonlinear phenomena such as modulation instability, stimulated Raman scattering, four-wave mixing, self-phase modulation, cross-phase modulation and the formation of higher-order solitons. The proposed scheme may have potential applications for the use of supercontinuum spectra in the areas of sensing, spectroscopy and metrology.

In many physical applications the electrons play a relevant role. For example, when a beam of electrons accelerated to relativistic velocities is used as an active medium to generate Free Electron Lasers (FEL), the electrons are bound to atoms, but move freely in a magnetic field. The relaxation time, longitudinal effects and transverse variations of the optical field are parameters that play an important role in the efficiency of this laser. The electron dynamics in a magnetic field is a means of radiation source for coupling to the electric field. The transverse motion of the electrons leads to either gain or loss energy from or to the field, depending on the position of the particle regarding the phase of the external radiation field. Due to the importance to know with great certainty the displacement of charged particles in a magnetic field, in this work we study the fractional dynamics of charged particles in magnetic fields. Newton’s second law is considered and the order of the fractional differential equation is [Formula: see text]. Based on the Grünwald–Letnikov (GL) definition, the discretization of fractional differential equations is reported to get numerical simulations. Comparison between the numerical solutions obtained on Euler’s numerical method for the classical case and the GL definition in the fractional approach proves the good performance of the numerical scheme applied. Three application examples are shown: constant magnetic field, ramp magnetic field and harmonic magnetic field. In the first example the results obtained show bistability. Dissipative effects are observed in the system and the standard dynamic is recovered when the order of the fractional derivative is 1.

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