Engineering the Hypersonic Phononic Band Gap of Hybrid Bragg Stacks
journal contributionposted on 13.06.2012, 00:00 by Dirk Schneider, Faroha Liaqat, El Houssaine El Boudouti, Youssef El Hassouani, Bahram Djafari-Rouhani, Wolfgang Tremel, Hans-Jürgen Butt, George Fytas
We report on the full control of phononic band diagrams for periodic stacks of alternating layers of poly(methyl methacrylate) and porous silica combining Brillouin light scattering spectroscopy and theoretical calculations. These structures exhibit large and robust on-axis band gaps determined by the longitudinal sound velocities, densities, and spacing ratio. A facile tuning of the gap width is realized at oblique incidence utilizing the vector nature of the elastic wave propagation. Off-axis propagation involves sagittal waves in the individual layers, allowing access to shear moduli at nanoscale. The full theoretical description discerns the most important features of the hypersonic one-dimensional crystals forward to a detailed understanding, a precondition to engineer dispersion relations in such structures.
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shear modulicalculationunderstandingpolywave propagationphononic band diagramsengineer dispersion relationsHypersonic Phononic Band GapBrillouin lightaccessHybrid Bragg StacksWe reportnanoscalepreconditionstructures exhibitincidencecrystalspacing ratiostackvector naturegap widthsagittal wavesdensitysound velocitiesspectroscopyvelocitymethacrylate