Evidence of surface acoustic wave band gaps in the phononic crystals created on thin plates

Abstract

Phononic structures and acoustic band gaps based on bulk materials have been researched in length in the past decades. However, few investigations have been performed on phononic structures in thin plates to form surface acoustic wave (SAW) band gaps. In this letter, we report a new type of phononic crystals manufactured by patterning periodical air-filled holes in thin plates. We confirmed the existence of SAW band gaps in the created phononic crystals through laser ultrasonics measurements. Wide multiple SAW band gaps and special structures, such as narrow pass bands within a band gap were observed experimentally.

Phonon dispersion in hypersonic two-dimensional phononic crystal membranes

“…Therefore, such structures have become attractive for optomechanics, radio frequency (RF), and thermoelectric applications [17,22,23]. Various one-, two-, three-dimensional PnCs designed to tune the propagation of bulk [2][3][4][13][14][15]24], surface (Rayleigh, Sezawa) [6,[25][26][27], and plate (Lamb) waves [5,16,18,28] have been investigated both theoretically and experimentally in a wide range of sizes and frequencies. However, the direct measurements of the hypersonic phonon dispersion were performed mostly for bulk [2][3][4]24,29,30] and surface PnCs [6,[31][32][33], while the influence of the phononic patterning in thin membranes was studied theoretically and experimentally by means of transmission measurements, where the acoustic waves are generated and detected electrically [5,18,34,35] or optically [28] in the kHz-MHz range.…”

“…The artificial, second-order periodicity introduced in PnCs results in the modification of the phonon dispersion and, optionally, in complete frequency band gaps due to Bragg reflections and/or local resonances, which can be controlled by geometry and material properties [1,3,11,12]. The first experimental studies on PnCs, limited by fabrication capabilities (spacing of mm), were focused on sound (kHz) and ultrasound (MHz) waves propagation and intended for applications in acoustic filtering, sensing, and wave-guiding [13][14][15][16][17][18]. Recent advances in fabrication methods have allowed reduction of the characteristic sizes of PnCs to nm scale, enabling the control of hypersonic (GHz) phonons [2,4,6,19] and heat transport [20,21].…”

Trampoline metamaterial: Local resonance enhancement by springboards

“…The concept of a trampoline metamaterial provides promising opportunities for the many applications that require large band gaps, and the proposed configuration can be easily fabricated and characterized considering that experimental investigations have already been conducted on plates consisting of either holes, 29 or pillars. 30,31 While the focus here has been on pillared elastic metamaterials and subwavelength band gaps, the concept is in principle applicable to other configurations (e.g., replacing the pillars with heavy inclusions) and to superwavelength band gaps.…”

Ultrasonic transmission through periodically perforated plates

“…Zhang et al [73] comes up with the first experimental evidence of Lamb gaps for air-aluminum and air-brass two-dimensional PhPs. This work was followed by more experimental [74,75] and theoretical studies [112,113,114,72] centered in band-gap and waveguiding phenomena.…”

“…It has been explained as due to the fluid-solid resonant coupling attributed to a non-leaky elastic surface mode, corroborating the phononic-perforated plate connection. Theoretical [70,71,72] and experimental [73,74,75] studies dealt firstly with band gap and waveguiding phenomena for air-solid and solid-solid Phononic Plates (PhPs), whereas most recent studies also report negative refraction for flexural [76] and shear horizontal [77] waves.…”