Effects of flexural and extensional excitation modes on the transmission spectrum of phononic crystals operating at gigahertz frequencies

Abstract

Articles you may be interested inMeasurement of frequency gaps and waveguiding in phononic plates with periodic stepped cylinders using pulsed laser generated ultrasound Surface acoustic wave band gaps in a diamond-based two-dimensional locally resonant phononic crystal for high frequency applications Phononic crystals operating in the gigahertz range with extremely wide band gaps Appl. Phys. Lett. 97, 193502 (2010); 10.1063/1.3504701Band gaps of lower-order Lamb wave in thin plate with one-dimensional phononic crystal layer: Effect of substrate Appl.Phononic crystals (PnCs) are a class of materials that are capable of manipulating elastodynamic waves. Much of the research on PnCs, both theoretical and experimental, focus on studying the transmission spectrum of PnCs in an effort to characterize and engineer their phononic band gaps. Although most studies have shown acceptable agreement between the theoretical and experimental bandgaps, perfect matches are elusive. A framework is presented wherein two and three dimensional harmonic finite element analyses are utilized to study their mechanical behavior for the purpose of more accurately predicting the spectral properties of PnCs. Discussions on a Harmonic Finite Elements Analysis formulation of a perfectly matched layer absorbing boundary and how reflections from absorbing boundaries can be inferred via standing wave ratios are provided. Comparisons between 2D and 3D analyses are presented that show the less computationally intensive 2D models are equally accurate under certain conditions. Finally, it is shown that a surface excitation boundary condition in a 3D model can significantly improve understanding of the experimental results for PnCs excited by surface mounted excitation sources. V C 2013 American Institute of Physics.

Demonstration of acoustic waveguiding and tight bending in phononic crystals

“…A frequency domain analysis was performed to reinforce the eigenfrequency analysis and calculate the transmission coefficient for the PnCs. 25 The FEM results are in good agreement with experimental results, however FEM shows a deeper bandgap. This is expected, and can be attributed to insertion and material losses in the experiment which are not accurately represented in the simulation.…”

Acoustic phonon propagation in ultra-thin Si membranes under biaxial stress field

“…In particular it has been shown that dispersion relations can be significantly modified e.g. by means of phononic crystals [1][2][3][4][5][6][7], spatial confinement [8][9][10][11][12][13] or external stress field [14][15][16][17][18][19][20]. Recently, single-crystalline inorganic membranes with thicknesses ranging from few hundred nanometers to the ultimate down-scaling limit represented by graphene, a truly 2D system, have received considerable attention [21].…”

Ultra-high frequency, high Q/volume micromechanical resonators in a planar AlN phononic crystal

“…This is due to losses in the experiment such as substrate losses, 24,25 material losses, 5 insertion losses, 26 and due to the Interdigital Transducers (IDTs) only detecting the longitudinal and flexural waves. 27 These experimental losses cause a reduction in the transmission peaks of the devices such that when the PnC is normalized to the slab, the depth of the bandgap is shallower than modeled. The difference between experimental and numerical transmissions (See Fig.…”