Étude des propriétés magnétiques de structure à cristaux photoniques à base de ferrites

Abstract

This thesis is dedicated to the study and the design of new magnetic structures based on photonic crystals for optical systems. To perform these simulations, three softwares are used, the first is called BandSOLVE, which is based on the plane wave method (PWE), the second is the Fullwave based on the finite time difference method (FDTD) and the last is the BeamPROP, based on the Beam Propagation Method (BPM). In the first part, a magnetic sensor based on a two-dimensional photonic-crystal nanocavity infiltrated by Fe3O4 and a broadband W1 waveguide is presented. In order to improve the performance of the structure, the geometrical parameters such as the size of the cavity, the diameter of the air holes have been optimized. An optimal quality factor of 8655 is obtained for L = 4. Subsequently, the principle of the detection is realized by infiltrating different concentrations of Fe3O4 as well as the various local magnetic field factors. We analyzed the detection properties, based on the properties of the cavity and the number of functional holes. For N = 12 air holes, a sensitivity of 146.97 nm / RIU, a magnetic sensitivity of 20.4 nm and a factor of merit of 22.66 are obtained. The optical properties of this sensor are numerically determined by performing simulations using the finite difference method in the 2D time domain. The combination of these performances makes this device a promising platform for the design and development of magnetic field sensors. The second part of this work concerns the improvement of the magneto-optical properties of optical isolators based on YIG, for this purpose, three concepts have been proposed. The first concept is based on the study of a polarization-independent waveguide based on a planar magneto-photonic crystal of YIG developed on an Al2O3 substrate. First, the width and position of the complete photonic band gap of the waveguide are optimized. Then we studied the influence of gyrotropy on the non-reciprocal properties of the waveguide. The results reveal a Faraday rotation of 6.11 × 104 ° / cm and a modal birefringence of 7 × 10-6. Then, we studied optical fibers, starting with a conventional optical fiber structure, followed by magneto-photonic crystal fibers based on YIG / GGG. In order to obtain a non-reciprocal effect, the coupling of TE-TM modes as well as the magneto-optical properties are studied as a function of the gyrotropy. These results show a remarkable development in the magneto-optical behavior, which helps to improve the performance of optical isolators and make it suitable for non-reciprocal devices.