Etudes expérimentales des propriétés dispersives de structures photoniques à base de micro-résonateurs pour la réalisation de fonctions optiques

Abstract

In this thesis, we present a theoretical and experimental study on the dispersive properties of photonic structures based on microresonators. First, we develop a cavity ringdown based method who fully describe the linear properties of microcavities such as coupling regime and group delay. This homodyne method is successfully applied on a cristalline microdisk (MgF2) and passive and active microspherical resonators to characterize various types of phenomena. In the case of doped microspherical whispering gallery modes resonators, we demonstrate selective amplification filter by combining high spectral selectivity and below threhold laser amplification (gain up to 20 dB at 1.55 μm). In passive high-Q microspheres with high finesse (F > 10^5), we could observe a lift of degeneracy between counter propagating modes. This effect originates from Rayleigh scattering that couples these two modes. This phenomenom is observed in the spectral domain by a splitting of the resonance. In a second step, we study the dispersive properties of coupled-resonator architectures. The coupling of two cavities leads to a splitting of the resonance and a notable decrease in the absorption around the resonance. We experimentally show that it is possible to circumvent limitation imposed by the intrinsic losses of passive resonators using active resonators. This effect can be seen as the classical counter part of Electromagnetically Induced Transparency (EIT). Moreover, we demonstrate that Coupled-Active-Resonator-Induced Transparency is a promising alternative in optical delay line since we can dynamically adjust the delay from a few ns to tens of ns (≈ 90 ns) without any change in the transparency of the system. Furthermore, we propose and experimentally demonstrated tunable cavity-linewidth narrowing based on the strong dispersion induced by the coupling of two resonators. In the case of three resonators, we propose a coupling scheme allowing the Q-factor of a critically coupled resonator to be increased and actively modulated by using two additional coupled resonators. We experimentally validate the principle by means of a model system consisting of Er3+-doped fiber coupled resonators. We successfully show a growth of the Q-factor from 4×10^7 up to 2,5×10^8. These experimental results demonstrate the means of Q-factor tailoring using active artificial photonic media.La caractérisation de résonateurs de facteurs de surtension très élevés (> 10^8) est difficilement réalisée à partir des méthodes expérimentales conventionnelles en régime stationnaire. Nous proposerons une méthode hybride spectrale/temporelle permettant la mesure du facteur de surtension global et la discrimination, de manière univoque, des facteurs Q_0 intrinsèque et Q_e extrinsèque du dispositif. Par cette simple mesure, nous déterminons le régime de couplage et les propriétés dispersives de micro-cavités. Dans un second temps, nous présenterons différentes architectures à base de cavités couplées actives donnant accès un à degré de liberté supplémentaire quant au contrôle de la dispersion. Nous étudierons successivement le phénomène de transparence induite pour la réalisation d'états de lumière lente puis la dispersion induite dans le cas de deux et trois cavités. Dans ce dernier cas, la modulation des pertes intrinsèques mène à un contrôle actif du facteur de qualité de la structure. La démonstration expérimentale de ce principe montre la possibilité d'ingénierie du facteur Q par l'utilisation de structures photoniques artificielles actives