Phononic and photonic properties of a stubbed strip waveguide
Résumé
Many studies have been devoted to the search of photonic and phononic band gaps, but relatively few works are dealing with the simultaneous control of phonons and photons. Phoxonic structures hold promises for the simultaneous confinement and tailoring of sound and light waves with potential applications to acousto-optical devices and highly controllable photon-phonon interactions. The aim of this presentation is to investigate both the photonic and photonic band structures, and in particular dual photonic-photonic band gaps, in a model of silicon strip waveguide in which each unit cell contains one hole in the middle and two symmetric stubs on the side of the waveguide. We use the finite-element (FE) methods to calculate the dispersion curves and the finite difference time domain (FDTD) to obtain the transmission spectra. Appropriate choices of the geometrical parameters allows us to obtain a complete phononic gap together with a photonic band gap of a given polarization and symmetry. Then, we investigate the possibility of confined modes inside cavities inserted in the phoxonic strip waveguide. Such situation is suitable to enhance the photon-phonon interaction. The optomechanical and photoelastic effects of a phononic/photonic cavity are discussed and analyzed on a two dimensional infinite phoxonic crystal before being applied to the strip waveguide. Depending on the choice of the phononic defect mode, the importance of the optomechanical and the photoelastic effects on the photonic mode is then discussed and compared. Finally, we discuss the actual values of the geometrical parameters, compatible with the technological fabrication constraints, in order to find the photonic features in the range of the telecommunication wavelengths, with the acoustic frequencies falling in the gigahertz regime.