Interaction acousto-optique dans les micro et nano structures périodiques.

Abstract

Phoxonic structures (also called phononic-photonic) consist of a periodicity in the refractive index and acoustic impedance in a systematic way and confine acoustic and electromagnetic waves.They lead to new acousto-optical or optomechanical applications. The main objective of this work is to model a crystal that allows the coupling of photonic and phononic band gap phenomena in order to study the acousto-optical interactions that can occur in anoptomechanical cavity by inserting a silicon disc of radius ri. insideinclusions. This analogy between optics and acoustics allows us, on one hand, to increase the efficiency of the insulators and on the other hand, to improve the acoustic characteristics and optimize the electromechanical performances of certain types of transducers used in medical imaging. The simulation of the gap according to the geometric parameters using the COMSOL MULTIPHYSICS software based on the finite element method has shown that the internal radius value ri = r/2 is optimal to obtain a maximum phononic and photonic (TM) width of 75% and 15% simultaneously. This opening obtained from Silicon remains the best compared to gaps of aluminum, SiO2 and epoxy. Finally a thorough study on transmission (results in accordance with the literature) was carried out and has shown another form of investigating of the band gap that confirmed the choice of the inner radius value. The width of the absolute band gap obtained by inserting an internal disc withoptimized radius ri = r/2insures the presence of a large number of well localized modes with a high quality factor which can reach 105. In conclusion, the phoxonic cavity designed with a high quality factor can be used to improve the acousto-optical interaction.