Subwavelength waveguiding of surface phonons in pillars-based phononic crystal

Abstract

In this study, we theoretically analyze the guiding of surface phonons through locally resonant defects in pillars-based phononic crystal. Using finite element method, we simulate the propagation of surface phonons through a periodic array of cylindrical pillars deposited on a semi-infinite substrate. This structure displays several band gaps, some of which are due to local resonances of the pillar. By introducing pillar defects inside the phononic structure, we show the possibility to perform a waveguiding of surface phonons based on two mechanisms that spatially confine the elastic energy in very small waveguide apertures. A careful choice of the height of the defect pillars, allows to shift the frequency position of the defect modes inside or outside the locally resonant band gaps and create two subwavelenght waveguiding mechanisms. The first is a classical mechanism that corresponds to the presence of the defect modes inside the locally resonant band gap. The seconde is due to the hybridation between the phonon resonances of defect modes and the surface phonons of the semi-infinite homogenous medium. We discuss the nature and the difference between both waveguiding phenomena.

Tuning of Surface-Acoustic-Wave Dispersion via Magnetically Modulated Contact Resonances

“…Similarly, ordered and disordered arrays of surface pillars are able to induce subwavelength band gaps due to the hybridization between the SAW modes and pillars' resonances [8]. These hybrid modes can be exploited for subwavelength waveguiding [9,10] and to achieve negative lensing effects [11]. The same hybridization phenomenon is observed when SAWs interact with a granular layer of silica microbeads, owing to the contact resonance of each sphere adhered to the elastic substrate.…”

Guiding of elastic waves in a two-dimensional graded phononic crystal plate

“…Based on former studies, 2D GPnCs, which are able to focus propagating waves, have been employed to implement acoustic lenses, beamwidth compressors, and bending waveguides [5][6][7][8][9][10]. For PnCs with pillars as attachments, resonance effects are very important in determining the properties of the system and its possible applications [11][12][13][14][15]. By placing several locally resonant layers of different resonance frequencies on a PnC, a broadband sound shield which is induced by the combination of different local resonant bandgaps can be achieved [16].…”

Guiding and confinement of interface acoustic waves in solid-fluid pillar-based phononic crystals

“…Amongst them, pillar-based phononic crystals have showed promising properties and has been exploited in diverse applications such as negative refraction, acoustic cloaking, sub-wavelength imaging, waveguiding and acoustic lensing. [4][5][6][7][8] In the literature, pillar-based structures were studied in two main configurations. They have been considered deposited on a slab, 5,9,10 or supported by semi-infinite medium.…”