Publications scientifiques
Frank G. Mbieda Ngomegni
Autres affiliations : University of Buea
Alain M. Dikandé*
Physica Scripta
Abstract The laser dynamics in inscription processes involving transparent media is carried out, by considering an optical field propagating in a transparent medium with Kerr nonlinearity. The study takes into account multi-photon absorption phenomena, as well as a possible modification of the material structure resulting in the generation of a plasma of nearly free electrons. The model is described by a complex Ginzburg–Landau equation governing the laser dynamics, in which an extra K th-order nonlinear term is induced by K -photon absorption processes. The model also takes into consideration the electron plasma generation via a linear term in the optical field. A global stability analysis of the system dynamics reveals a rich variety of fixed points consisting of no, one or two singular points in the amplitude-frequency plane. The modulational instability of plane waves gives rise to period-halving bifurcations in the continuous-wave amplitude growth rate, reminiscent of dominant multi-pulse structures in the nonlinear regime at large multi-photon absorption rate K . Pulses and multi-pulses are observed in numerical simulations of the nonlinear equations for the full system dynamics, the first structures are clearly associated with the case K = 2 whereas multi-pulse structures of increasing amplitudes and shorter perioids are dominant at larger values of K .
