Etienne Averlant has successfully defended his PhD thesis for which he carried out experimental and theoretical studies of localized structures in Vertical-Cavity Surface-Emitting Lasers (VCSELs), also called cavity solitons. 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, he reports experimental evidence of spontaneous formation of localized structures in an 80 mm 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.
Further, he focuses on the vectorial character of localized structures generated in a broad-area VCSEL submitted to linearly polarized optical injection. He explains our experimental findings by considering the spin-flip carrier dynamics in the VCSEL quantum well active medium.
In a third part, he adds a delayed optical feedback to the modified Swift-Hohenberg equation derived in the first part. He shows that the delayed feedback induces a spontaneous motion of two-dimensional localized structures in an arbitrary direction in the transverse plane. He characterizes moving cavity solitons 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, he considers temporal localized structures generated in nonlinear fiber cavities. He shows 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. He also describes a photonic crystal fiber cavity by considering second, third and fourth order dispersion. He shows that third order dispersion breaks the inversion symmetry and allows localized structures to drift with a constant speed. He has characterized their motion by estimating, analytically and numerically, their linear and nonlinear velocity.
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