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Spectral generation and control of linear and nonlinear self-accelerating beams and pulses.


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Bongiovanni, Domenico (2018). Spectral generation and control of linear and nonlinear self-accelerating beams and pulses. Thèse. Québec, Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 262 p.

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Unlike a conventional laser propagating along a straight line, a self-accelerating beam has the characteristic to follow a curved trajectory in a linear homogeneous medium, thus introducing transverse acceleration. Research on this field started in 2007 with the introduction of the Airy beam in an optical context. Such a beam propagates without diffraction along a parabolic trajectory, while exhibiting an Airy-shaped amplitude profile. Another property associated to the Airy beam is its capability of “self-healing”. Should one attempt to block a part of the beam at a certain distance, the Airy beam would “regenerate” during propagation. These intriguing features have made the Airy beam ideal for several applications in diverse fields of science. To name a few, we can mention optical bullets, curved plasma channels, electron accelerating beams and optical trapping. In the time domain, the counterpart to an Airy beam is an Airy pulse, showing the same properties in time when propagating in a linear regime. Nevertheless, in nonlinear media, an Airy beam/pulse behaves differently, due to the breakup of its acceleration by the nonlinearity. This constitutes a clear disadvantage, eventually limiting the possible range of applications of these wave packets. Meanwhile, over the last few years, the concept of acceleration has been extended beyond the parabolic case. In particular, further research advances on this topic have reported self-accelerating beams propagating along any arbitrary trajectory. Interestingly, the possibility to generate self-accelerating beams has also been investigated in the framework of the so-called “non-paraxial” regime, where beams accelerating along large bending angles have been demonstrated. In this dissertation, we numerically and experimentally investigate the linear and nonlinear dynamics of optical self-accelerating wave packets. In the linear regime, one of the technique used to generate such wave packets is based on the spectral amplitude and phase modulation of a standard laser beam. We introduce an analytical approach able to predict theirs curved paths, in the one- (or (1+1)D), two- (or (2+1)D) and three-dimensional (i.e. spatio-temporal or (3+1)D) cases, starting from the knowledge of the applied spectral modulation. Conversely, our method allow us to achieve any desired convex path by accordantly designing the spectral modulation. Based on this study, we also propose and demonstrate a practical and easy technique to confine the energy of self-accelerating wave packets. In particular, we show that a significant enhancement of the peak intensity of these beams can be achieved, while preserving their intrinsic properties. Finally, we study the nonlinear propagation of Airy beams and pulses. Specifically, we show that these self-accelerating wave packets are capable to preserve their accelerating properties in Kerr and photorefractive nonlinear media when their initial spectral modulation is properly engineered.

Type de document: Thèse Thèse
Directeur de mémoire/thèse: Morandotti, Roberto
Co-directeurs de mémoire/thèse: Hu, Yi; Wetzel, Benjamin
Mots-clés libres: linear dynamics; nonlinear dynamics; optical self-accelerating wave packets; laser beam; peak intensity; nonlinear propagation of Airy beams and pulses
Centre: Centre Énergie Matériaux Télécommunications
Date de dépôt: 03 juill. 2018 13:30
Dernière modification: 03 juill. 2018 13:30
URI: http://espace.inrs.ca/id/eprint/6949

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