Surface Acoustic Waves in Phononic Crystals

Abstract

Over the past two decades, propagation of acoustic waves in periodic structures comprised of multi-components has received much attention because of renewed physical properties and potential applications in a variety of fields, such as noise and vibration isolation, frequency filters in wireless communication, super lens design, etc. These composite materials, called phononic crystals (PCs) [1,2], give rise to forbidden gaps for acoustic waves which are analogous to the band gaps for electromagnetic waves in photonic crystals. Major mechanisms leading to the forbidden gaps are Bragg scattering and localized resonances (LR) [3]. The former opens up the Bragg gap at the Brillouin-zone boundaries, and the band-gap frequency corresponds to the wavelength in the order of the structural period, i.e. of the lattice constant, and relates to the lattice symmetry. On the other hand, localized

Wet-etched phononic crystal waveguiding on GaAs

“…The values of the two curves are normalized by the spectral maximum amplitude of the substrate. In the lower curve of Figure 5(a), the phononic crystal is seen to attenuate |uz| at all frequencies, as might be expected with the introduction of scattering centres (Wu, et al, 2016) along the path of the SAW. However, the transmitted wave through the phononic crystal is considerably less between 400 MHz and 450 MHz.…”

“…While these wet-etched holes do provide a platform to demonstrate waveguiding behaviour along the GaAs surface, the larger than desired attenuation is mimicked in the simulations, which have estimated decay constant of approximately 1 dB/a. The leakage of acoustic power into the phononic crystal and bulk may be caused by the Pseudo-SAW behaviour of GaAs along the [110] direction (Webster & Carr, 1985), radiating into the substrate bulk (Wu, et al, 2016), or the coupling of multiple modes present in the bandgap (Pennec, et al, 2010). Further analysis into the origins of the decay mechanism will not be studied here.…”

Frequency and time domain analysis of surface acoustic wave propagation on a piezoelectric gallium arsenide substrate: A computational insight

“…Due to the spatial periodicity of the PC, see Figure 1, it results (Laude and Khelif, 2016;Wu et al, 2016) r(rÞ = r(r + a);…”

“…Both experimental (Malfanti et al, 2011;Yankin et al, 2014) and numerical (Li et al, 2012) studies are today available. The computational modeling is approached through finite difference, finite element (FE), or plane wave expansion (PWE) methods (see Assouar and Oudich, 2011;Li et al, 2012;Wu et al, 2016). FE analysis and experimental study of SAW propagation through twodimensional pillar-based surface PC is reported for example in Yankin et al (2014) and Guo et al (2016), while the P-Matrix method is used in Tian et al (2016).…”

Surface acoustic wave modes in two-dimensional shallow void inclusion phononic crystals on GaAs

“…Phononic crystal (PnC) structures for controlling surface acoustic wave (SAW) propagation have been studied as an alternative to traditional metal gratings for applications requiring SAW guiding, reflecting and electronic device integration [1]. One significant design challenge of PnCs for SAW devices is the bulk mode conversion losses from leaky SAWs [2].…”