Um estudo sobre cristais fotônicos 1D e 2D

Abstract

Throughout this thesis we are going to present a series of works concerning the study of the properties of one and two-dimensional photonic crystal systems such as: AlGaAs/GaAs circular microcavities, double heterostructures photonic crystal cavities (PCDH) and L3 cavities. Firstly, we introduce a study carried out on circular microcavities systems where the aim was to understand the influence of the light emitted by the embedded quantum dot (QD) ensemble over the cavity excited modesrelative intensity. As a result we showed that such intensity depends both on the QD position in the plane of the cavity and on the average polarization of the ensemble of QD. In the second work we propose an easier and efficient way to perform transmission experiments on photonic crystal systems where the excitation and signal collection are made with respect to the normal direction. For doing it, we use samplesthat have diffraction gratings on both sides of double heterostructures photonic crystal cavities, fabricated in the same semiconductor chip. We were able to visually observe the signal transmitted through the device extension applying an infrared imaging technique, but however we did not resolve any cavity mode due to the presence of many Fabri Perot modes in the transmitted spectrum. In the final chapter we show the results of QD/mode tuning measurements carried out in L3 cavity systems fabricated in the centre of p-i-n semiconductor junctions and study the effects of such a tuning on photoluminescence experimentsrealized with resonant and non-resonant excitation. Directly comparing our results we observed a significant decrease in the background of those samples that were excited with resonant excitation in relation to those excited with non-resonant excitation. Furthermore, in reflectivity experiments performed in the same set of samples we observed a considerable decrease in the fundamental mode intensity when thedetuning between the mode and the nearest embedded QD was roughly null in a system governed by the weak coupling. Lastly we report about changes in the reflectivity peak symmetry of the L3 cavities when their fundamental modes were excited with white light at different degrees of linear polarization. Our results indicate that the observed phenomenon takes place, in a controlled way, due to an interference process between the quantized L3 fundamental mode and the continuum of scattered modes in the vicinities of the crystal in a clear signature of the Fano interference phenomenon.