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Thursday, July 11 • 10:20 - 10:40

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Phononic Crystals (PCs) (i.e. periodic arrangements of several materials) have recently received a great deal of interest because of the unusual properties that they can exhibit. Classically, depending on material properties and geometrical arrangement, PCs can produce band gaps, i.e. frequency ranges where the propagation of waves is forbidden (i.e. waves are evanescent). These Bragg band gaps offer several potential applications such as sonic insulators or filters, from the kHz to the GHz range depending upon the spatial periodicity. In this presentation, the general case of PCs made of piezoelectric materials is studied where the band gaps may be tuned by changing the electrical boundary conditions. Two devices have been studied: (1) stack of piezoelectric rods or plates, poled along their thickness [S. Degraeve et al, J. Appl. Phys. 115, 194508 (2014)]., (2) a piezoelectric plate, poled along its thickness, covered by a periodic array of electrodes on its two faces [C. Vasseur et al, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 65, 9 (2018) 1552-1562]. These devices exhibit Bragg gaps that depend on the electrical boundary conditions chosen on periodically placed electrodes. In both cases, an analytical model is developed that is compared to finite element results, validating the model. Depending on the electrical boundary condition, tunability is clearly demonstrated, i.e. an increase or a decrease of the width and the position of the stop bands. For both devices under study, ultrasonic experiments are presented, showing a good agreement with the theoretical predictions. Finally, more complex control involving space-time modulation of electrical boundary conditions give access to tuning/control of nonlinear physical effects such as non reciprocity [C. Croenne et al, Appl. Phys. Lett. 110(6), 061901 (2017)]. Extension of this concept to guided waves in piezoelectric plates and surface waves in piezoelectric substrates is currently under progress for microfabricated RF components.

Thursday July 11, 2019 10:20 - 10:40 EDT
Westmount 3
  T02 Act. noise & vib. cntrl., SS03 Active meta-materials