Nonlinear beam self-cleaning in a coupled cavity composite laser based on multimode fiber

We study a coupled cavity laser configuration where a passively Q-switched Nd:YAG microchip laser is combined with an extended cavity, including a doped multimode fiber. For appropriate coupling levels with the extended cavity, we observed that beam selfcleaning was induced in the multimode fiber thanks to nonlinear modal coupling, leading to a quasi-single mode laser output. In the regime of beam self-cleaning, laser pulse duration was reduced from 525 to 225 ps. We also observed a Q-switched mode-locked operation, where spatial self-cleaning was accompanied by far-detuned nonlinear frequency conversion in the active multimode fiber

Kerr self-cleaning of pulsed beam in an ytterbium doped multimode fiber

We experimentally demonstrate that Kerr spatial self-cleaning of a pulsed beam can be obtained in an amplifying multimode optical fiber. An input peak power of 500 W only was sufficient to produce a quasi-single-mode emission from the double-clad ytterbium doped multimode fiber (YMMF) with non-parabolic refractive index profile. We compare the self-cleaning behavior observed in the same fiber with loss and with gain. Laser gain introduces new opportunities to achieve spatial self-cleaning of light in multimode fibers at a relatively low power threshold

Laser array phase-locking and nonlinearity

Présentation orale : ULTRA/NANO-6-12-3International audienc

Collision between type II two dimensional quadratic solitons

International audienceWe report experimental and numerical results that describe collisions between two-dimensional type II quadratic solitons excited in a KTP crystal by fundamental waves of orthogonal polarization. Our results provide experimental evidence of the possibility of both inelastic collision (when two quadratic solitons merge at input into a single soliton at output) and quasi-elastic collision

Modal attraction on low order modes by Kerr effect in a graded refractive index multimode fiber

Modal attraction towards low order modes in a GRIN multimode fiber was experimentally observed at high power and characterized, thus enriching the dynamics of the Kerr self-cleaning effect leading to quasi fundamental mode generation

Generation of coherent wavefronts and images inside laser resonators

We describe a new type of laser mode filtering using two complementary spatial filters located against the plane mirrors of a confocal lens resonator. With Nd/YAG as amplifying medium, we report the synthesis of two particular waves: a sinusoidally modulated wavefront, and a uniphase beam with a flat spatial profile and minimal divergence. The temporal evolution of the beam under construction is also recorded. The process is a new type of wavefront reconstruction, like holography, but without reference.Nous décrivons un nouveau type de filtrage des modes d'un laser basé sur l'utilisation de deux filtres spatiaux complémentaires situés contre les miroirs plans d'un résonateur confocal à lentille. Nous rapportons la synthèse de deux ondes particulières dans un laser à YAG/Nd : une surface d'onde modulée sinusoïdalement et un faisceau uniphase, de profil spatial plat et de divergence minimale. L'évolution temporelle du faisceau pendant la phase de construction est aussi rapportée. Ce procédé est un nouveau type de reconstruction de front d'onde au même titre que l'holographie, mais sans référence

Interactions of Type II vectorial spatial solitary waves in materials with quadratic non-linearity

We present analytical, numerical and experimental results of the interactions between Type II vectorial spatial solitary waves (QSSW) in second-order non-linear media. We show that the outcome of the interaction can be changed from beam coalescence to steering, crossing or repulsion through a non-coherent control (i.e. the control does not rely on the relative phase between the interacting QSSW). We also provide experimental evidence that both quasi-elastic and inelastic collision between QSSW are feasible in second order non-linear media, depending on the relative velocity of the interacting QSSW. We determine (analytically, numerically and experimentally) the critical transverse velocity for elastic collision to be observed, when the fundamental frequency component of the two interacting beams are orthogonally polarized at the input face of the non-linear crystal