Localized structures in surface-emitting lasers: vectorial character and delay-induced motion

In this PhD thesis, we carry out experimental and theoretical studies of localized structures in Vertical-Cavity Surface-Emitting Lasers (VCSELs). Such structures consist of bright peaks of light, localized in space that can be switched on or off, in the plane transverse to the propagation of the beam. They have notably been proposed for two applications: all-optical information processing, and information storage. In the first part of this thesis, we report experimental evidence of spontaneous formation of localized structures in an 80 µm diameter VCSEL biased above its lasing threshold and under optical injection. Such localized structures are bistable with the injected beam power and the VCSEL current. We experimentally investigate their formation for different frequency detunings between the injected beam and the VCSEL. Then, we derive a modified-Swift-Hohenberg equation to describe this system. We characterize localized structures by constructing their snaking bifurcation diagram and by showing clustering behavior within the pinning region of parameters. In the second part of this thesis, we focus on the vectorial character of localized structures generated in a broad-area VCSEL submitted to linearly polarized optical injection. We provide the first experimental evidence of the vectorial nature of localized structures generated in a broad area VCSEL: the polarization of the localized structure is not the one of the optical injection as it acquires a distinct ellipticity. We explain our experimental findings by considering the spin-flip carrier dynamics in the VCSEL quantum well active medium. In a third part, we add a delayed optical feedback to the modified Swift-Hohenberg equation derived in the first part. We show that the delayed feedback induces a spontaneous motion of two-dimensional localized structures in an arbitrary direction in the transverse plane. We characterize moving localized structures by estimating their threshold and calculating their velocity. This work is then extended to the more general well-accepted VCSEL-mean field model. In the last part of this thesis, we consider temporal localized structures generated in nonlinear fiber cavities. We show that when birefringence of a fiber cavity is taken into account, several kinds of localized structures can be generated. These structures differ by their polarization properties. We also describe a photonic crystal fiber cavity by considering second, third and fourth order dispersion. We show that third order dispersion breaks the inversion symmetry and allows localized structures to drift with a constant speed. We have characterized their motion by estimating, analytically and numerically, their velocity.