Self collimation of ultrasound in a 3D sonic crystal (original) (raw)

Subdiffractive propagation of ultrasound in sonic crystals

Physical Review B, 2007

We present an experimental demonstration of the subdiffractive propagation Í‘self-collimationÍ’ of an ultrasound beam in a two-dimensional sonic crystal formed by a square array of steel cylinders inmersed in water. Measurements show that the diffractive spreading of a narrow beam is strongly reduced along the spatially modulated direction of the crystal. The effect of the finite crystal length is theoretically analyzed, resulting in a frequency shift of the subdiffractive point in good correspondence with the experimental results.

Formation of collimated sound beams by three-dimensional sonic crystals

Journal of Applied Physics, 2012

A theoretical and experimental study of the propagation of sound beams in-and behind three-dimensional sonic crystals at frequencies close to the band edges is presented. An efficient collimation of the beam behind the crystal is predicted and experimentally demonstrated. This effect could allow the design of sources of high spatial quality sound beams.

Nonlinear self-collimated sound beams in sonic crystals

Physical Review B, 2015

We report the propagation of high-intensity sound beams in a sonic crystal, under self-collimation or reduced-divergence conditions. The medium is a fluid with elastic quadratic nonlinearity, where the dominating nonlinear effect is harmonic generation. The conditions for the efficient generation of narrow, non-diverging beam of second harmonic are discussed. Numerical simulations are in agreement with the analytical predictions made, based on the linear dispersion characteristics in modulated media and the nonlinear interaction in a quadratic medium under phase matching conditions.

Simultaneous self-collimation of fundamental and second-harmonic in sonic crystals

Applied Physics Letters, 2011

Simultaneous self-collimation of sound beams with different frequencies, corresponding to fundamental wave and to its second harmonic, is proposed theoretically and demonstrated experimentally. The result is obtained when the isofrequency contours for each harmonics, corresponding to different propagation bands, develop flat segments along the same direction. The effect can be utilized for managing (enhancement and control) of nonlinear frequency mixing of narrow sound beams.

Nondiffractive propagation of sound in sonic crystals

Journal of The Acoustical Society of America, 2008

We report the nondiffractive propagation of acoustic waved in sonic crystals, e.g., acoustic media with periodic modulation of the material parameters (density and bulk modulus). Such novel materials have recently attracted a great interest, because of their potential applications in the control of sound propagation, used as reflectors, focusers or waveguides. All these properties are related with the dispersion introduced by the crystal anisotropy. In particular we consider the case of two-dimensional sonic crystals, consisting, e.g. in an array of steel cylinders in water. It is shown that, for given frequencies and directions of incidence, a narrow sonic beam can propagate without diffractive broadening. Such nondiffractive sonic beams exist in crystals with perfect symmetry, and do not require the presence of defects, differently from other waveguiding phenomena reported previously. The cancellation of diffraction occurs at frequencies and wavevectors for which dispersion curves (isofrequency lines) have zero curvature, i.e, are locally flat. By means of perturbative techniques, a simple analytical expression for the nondiffractive conditions has been obtained. The phenomenon is also demonstrated by numerical integration of the acoustic equations using the FDTD technique. We present experimental evidence of the nondiffractive propagation in a periodic array of steel cylinders in water.

Nondiffractive propagation in sonic crystals

The Journal of the Acoustical Society of America, 2006

We report the nondiffractive propagation of acoustic waved in sonic crystals, e.g., acoustic media with periodic modulation of the material parameters (density and bulk modulus). Such novel materials have recently attracted a great interest, because of their potential applications in the control of sound propagation, used as reflectors, focusers or waveguides. All these properties are related with the dispersion introduced by the crystal anisotropy. In particular we consider the case of two-dimensional sonic crystals, consisting, e.g. in an array of steel cylinders in water. It is shown that, for given frequencies and directions of incidence, a narrow sonic beam can propagate without diffractive broadening. Such nondiffractive sonic beams exist in crystals with perfect symmetry, and do not require the presence of defects, differently from other waveguiding phenomena reported previously. The cancellation of diffraction occurs at frequencies and wavevectors for which dispersion curves (isofrequency lines) have zero curvature, i.e, are locally flat. By means of perturbative techniques, a simple analytical expression for the nondiffractive conditions has been obtained. The phenomenon is also demonstrated by numerical integration of the acoustic equations using the FDTD technique. We present experimental evidence of the nondiffractive propagation in a periodic array of steel cylinders in water.

Propagation of sound beams behind sonic crystals

Physical Review B, 2009

A theoretical and experimental study of the propagation of sound beams in and behind two-dimensional sonic crystals at frequencies close to the band edges is presented. Beam focusing is predicted and discussed. We evaluate, by analytical numerical methods, the main focusing characteristics, such as the focal distance, the width of beam waist, and the beam quality at the waist. The field distribution is shown to depend strongly on the beam size and frequency. Experiments were performed on narrow sources radiating in ultrasound regime, although the results are extendable to arbitrary frequencies.

Subdiffractive propagation in a bidimansional sonic crystal

Hydroacoustics, 2007

Sonic crystals are media with a periodic modulation of the acoustic parameters, as the density and the bulk modulus. They have recently attracted a great interest, because of their potential applications in the control of sound propagation, used as reflectors, focusers or waveguides. All these properties are related with the dispersion introduced by the crystal anisotropy. We report on the nondiffractive propagation of sound in two-dimensional sonic crystals. It is shown that, for given frequencies and directions of incidence, a narrow sonic beam can propagate without diffractive broadening. Such nondiffractive sonic beams exist in crystals with perfect symmetry, and do not require the presence of defects, differently from other waveguiding phenomena reported previously. The cancellation of diffraction has been predicted using the plane-wave expansion method to evaluate the dispersion surfaces of the crystal and the spatial dispersion (isofrequency) curves. It occurs for frequencies and wavevectors for which dispersion curves have zero curvature, denoting a transition between focusing and defocusing regimes. By means of perturbative techniques, a simple analytical expression for the nondiffractive conditions has been obtained. The phenomenon is also demonstrated by numerical integration of the acoustic equations using the FDTD technique with very good agreement with the preliminary experimental results. Support from Spanish MEC, project FIS2005-07931-C03-01, is acknowledged.