Self collimation of ultrasound in a three-dimensional sonic crystal

Abstract

We present the experimental demonstration of self-collimation (subdiffractive propagation) of an ultrasonic beam inside a three-dimensional (3D) sonic crystal. The crystal is formed by two crossed steel cylinders structures in a woodpilelike geometry disposed in water. Measurements of the 3D field distribution show that a narrow beam, which diffractively spreads in the absence of the sonic crystal, is strongly collimated in propagation inside the crystal, demonstrating the 3D self-collimation effect.

Effective impedance boundary optimization and its contribution to dipole radiation and radiation pattern control

“…Recent progress in the research area of photonic and phononic crystals and metamaterials provides a new approach to realize radiation pattern control and modulation. Early studies focused on spatial dispersion affected by spatial periodicity to modulate radiation patterns-that is, utilizing crystal anisotropy to counteract the spreading of the wave [5][6][7] -and band-edge states are the most important factors for realizing it [8][9][10] . Recently, based on the forminvariant form of Maxwell's equations under certain coordinate transformations, transformation optics for controlling the electromagnetic fields has proved to be an effective approach for manipulating ray traces 11,12 .…”

Evidences of spatial (angular) filtering of sound beams by sonic crystals

“…The phenomenon has been demonstrated for two-dimensional SCs. However the band calculation of the three-dimensional SCs shows the existence of the twodimensional angular band gaps, as well as full two-dimensional self-collimation of the beams [14]. This envisages the possibility of the full two-dimensional spatial filtering with three-dimensional SCs, which could be highly utile in technological applications.…”

Nonlinear self-collimated sound beams in sonic crystals

“…The size of the self-collimated beam is also limited by the extension of such flat region in angular space. Self-collimation of low amplitude (linear), monochromatic acoustic waves has been demonstrated in 2D [4] and 3D [5] sonic crystals. More recently, the simultaneous self-collimation of two beams of different frequencies was also demonstrated experimentally [6].…”