Acoustic Metamaterials Based on Phononic Crystals

Friday, June 4, 12h:00, IFAE: JOSÉ SANCHEZ-DEHESA. Grupo de Fenómenos Ondulatorios, Departamento de Ingeniería Electrónica. Universidad Politécnica de Valencia.

It has been shown that arrays of acoustic scatterers in a fluid or a gas define, in the homogenization limit, a class of acoustic metamaterials or metafluids with extraordinary properties [1]. These metafluids have positive dynamical mass density and positive bulk modulus, but they can be used to engineer materials with acoustical properties not know in nature. Along this talk I will review results recently obtained by our research group on this topic. First, I will introduce the homogenization theory allowing the determination of the acoustic parameters of metafluids based on phononic crystals made of periodic distributions of acoustic scatterers. It will be shown, for example, that acoustic structures can be tailored with a perfect matching of impedance with the surrounding medium [2]. By using metafluids we have also fabricated and characterized gradient index acoustic lenses. Moreover, metafluids have been proposed to engineer structures with anisotropic dynamical mass density [3], a property required to build acoustic cloaks [4]. In comparison with cloaking structures based on metamaterials with local resonances, these metafluids have broadband operation [5,6]. Finally, I will show that anisotropic metamaterials can be used to introduce a new type of crystalline systems named Radial Wave Crystals, which are radially periodic structures that verify the Bloch theorem. These new crystals are possible for acoustic waves as well for electromagnet waves [7].

References

[1] D. Torrent, A. Håkansson, F. Cervera and J. Sánchez-Dehesa, Homogenization of 2D clusters of rigid rods in air, Phys. Rev. Lett., 96, 204302 (2006).

[2] D. Torrent and J. Sánchez-Dehesa. Acoustic metamaterials for new 2D sonic devices,  New J. Phys. 9 023004 (2007). [3] D. Torrent and J. Sánchez-Dehesa. Anisotropic mass density by 2D acoustic metamaterials  New J. Phys. 10,  023004 (2008).

[4] S.A. Cummer and D. Schurig. One path to acoustic cloaking. New J. Phys., 9, 45 (2007).

[5] L.-W. Cai and J. Sánchez-Dehesa, Analysis of Cummer-Schurig acoustic cloaking. New J. Phys., 9, 450 (2007).

[6] D.Torrent and J. Sánchez-Dehesa. Acoustic cloaking in 2D: A feasible approach.  New J. Phys., 10, 063015 (2008).

[7] D. Torrent and J. Sánchez-Dehesa. Radial Wave Crystals, Phys. Rev. Lett., 103, 064301 (2010).

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