Effects of the helical magnetic wiggler on a laser beam interacting with a lattice of metallic nanoparticles: plasmonic and body waves

摘要

In this study, the influence of a helical magnetic wiggler on the nonlinear interaction of a laser beam with a lattice of metallic nanoparticles is investigated. Coupling of the static magnetic field of the wiggler to the field of the laser wave, and therefore a change in the electric field intensity of the pumped wave, leads to the formation of a nonlinear force in the interaction region. As a consequence, the nonlinear force enhances the plasmonic oscillations of the electronic cloud of each nanoparticle causing electron density modulation, which improves the self-focusing property of the laser beam. Using a perturbative method, the nonlinear dispersion plasmonic and body waves are obtained from the interaction of a laser beam with a lattice of nanoparticles in the presence of a helical magnetic wiggler. We investigate the effects of nanoparticle size, their separations and wiggler field strength on the evolution of the transverse profile of the laser beam in both incident linearly polarized and circularly polarized waves. The numerical results indicate that in the linear polarization for all branches of plasmonic and body waves (except for the low-frequency middle branch), laser bandwidth decreases with increasing nanoparticle separation length, which improves the self-focusing property. Moreover, with enhancement of the normalized wiggler field strength, the laser amplitude transverse profile for all branches of plasmonic and body waves (except for the low-frequency middle branch) decreases, which leads to beam focusing. For left and right circular polarization, it is found that with an increase in the nanoparticle separation length, the laser amplitude transverse profile for all branches of plasmonic and body waves (except for the low-frequency middle branch) increases, which leads to beam defocusing. Furthermore, with enhancement of the normalized wiggler field strength, the laser amplitude transverse profile decreases for body waves and the low-frequency lower branch of plasmonic waves, which gives rise to the beam focusing, whereas it increases for the low-frequency middle and upper branches of plasmonic waves, which leads to the beam defocusing.