Extraordinary transmission of gigahertz surface acoustic waves

Abstract

Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.

Molecular Dynamics Simulation of Nanocrack Propagation in Single-Layer MoS2 Nanosheets

“…As illustrated in Figure S3, the stress concentration around the crack tip decays in an approximately semicircular wavefront. This is similar to laser-induced surface acoustic waves in single MoS 2 flake and thin films. , …”

“…This is similar to laser-induced surface acoustic waves in single MoS 2 flake and thin films. 53,54 For an approximately straight crack extension, the dynamic fracture energy Γ can be expressed as 55…”

Giant extraordinary transmission of acoustic waves through a nanowire

“…However, despite this, the result we find is a record, giant transmission enhancement. It may even be possible to achieve future efficiency increases by changing the material or adding a cavity to the cylinder (22). Our results were obtained for a nanowire with a diameter of 5 nm at ~50 GHz and  ~ 120 nm, although, as mentioned above, the results are scalable to larger dimensions and lower frequency ranges for which ultrasonic attenuation is negligible.…”

“…However, our results are perfectly scalable to larger dimensions for which ultrasonic attenuation would be negligible at this resonance. Moreover, crystals such as silicon, as used in (22) for surface wave extraordinary transmission, would have negligible ultrasonic attenuation at room temperature for the present nanowire dimensions (42).…”

“…Likewise for metamaterials involving airborne sound with zero effective density based on the use of membranes (18,19) or zero effective compressibility based on the use of Helmholtz resonators (20,21), with transmission efficiencies up to ~100 (18,19). However, although EAT has been demonstrated for surface acoustic waves on solids (22), it has not been demonstrated for bulk waves in solids, a geometry with potential applications in solid-state acoustic wave concentration and focusing. In contrast to the case of EAT involving fluids in which significant viscoelastic losses occur, record values of the transmission efficiency are expected for bulk waves in solids.…”