Abstract
The acoustic properties of a hybrid composite that exhibits both photonic and phononic behavior are investigated numerically with finite-element and finite-difference time-domain simulations. The structure is constituted of a periodic array of photonic resonant cavities embedded in a background superlattice. The resonant cavities contain a photo-elastic chalcogenide glass that undergoes atomic-scale structural reorganization when irradiated with light having energy close to its band-gap. Photo-excitation of the chalcogenide glass changes its elastic properties and, consequently, augments the acoustic transmission spectrum of the composite. By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters.
Highlights
By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters
A phononic crystal (PC) is a composite structure comprised of a spatially periodic array of inclusions of one material embedded in a different background matrix material
PCs come in one, twoand three-dimensional forms and, depending on their application, have length scales that vary from meters to several hundreds of nanometers
Summary
A phononic crystal (PC) is a composite structure comprised of a spatially periodic array of inclusions of one material embedded in a different background matrix material. The excitation of localized electrons from the top of the band-gap creates electron-hole pairs that facilitate the creation of metastable defect configurations within the covalent network This phenomenon leads to such effects as photo-darkening,[32] photo-expansion,[33] photo-anisotropy,[34] photo-fluidity[35] and photo-elasticity.[36] Gump et al demonstrated experimentally that the Ge-Se family of chalcogenide glasses undergo reversible changes in their elastic properties when irradiated with focused light having energy close to the material’s band-gap.[36] when irradiated with a laser at 2mW power, C11 of a glass with composition GeSe4 was reduced by approximately 5% with respect to C11 for the non-irradiated system. The stiffness of the glass was fully recovered upon ramping-down the laser from 6mW to 2mW, indicating that photo-elasticity in Ge-Se systems is a reversible phenomenon
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