Vector-field transverse-pattern dynamic in a laser with axial magnetic
field
A.I. Konukhov, L.A. Melnikov, M.V. Ryabinina
Department of Optics, Saratov State University,
Saratov, Russia
Pattern formation in lasers and associated spatio-temporal dynamics in the output of laser beam is a subject of numerous investigations. Hovever, most of the dynamical models of multi-transverse mode lasers assume the linear polarized electric field in the laser cavity. This approach (scalar model) is not valid in many cases. The examples are fiber lasers, semiconductor lasers, VCSEL's, and Zeeman lasers.
In this paper we present the results of the numerical simulations of transverse
-pattern dynamics in a Zeeman ring-cavity laser with high round-trip gain and
arbitrary cavity configuration, including near-confocal and near-flat mirror
cavity with the active medium having homodeneously-broadened transition
in the weak axial magnetic field. The paraxial
wave
equation for the orthogonal circular components of the field were solved
using of
the step-splitting method. The modal decomposition in terms of Laguerre-Gaussian
empty-cavity modes was used. Numerical experiments were carried for the
cavity configuration including a spherical mirror and Gaussian aperture.
The simulations started with noise and after some thousands of round-trips the patterns and temporal dependences were recorded and analysed. At the small gain the stationary regimes with Gaussian profiles of the circulary polarized components are observed. For nonzero magnetic field the asymmetry of components caused by self-lensing for the detuned beam is shown. The second thereshold is observed for higher gain appearing as temporal oscilations of power. We have observed symmetry breaking and the formation of complicated patterns. At high gain the quasiperiodic or chaotic oscillation occured accompanied with more complicated transverse structures.
Vector defects appearance is also discussed.