Broadband focusing of underwater sound using a transparent pentamode lens

Xiaoshi Su, Andrew N. Norris, Colby W. Cushing, Michael R. Haberman, Preston S. Wilson

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


An inhomogeneous acoustic metamaterial lens based on spatial variation of refractive index for broadband focusing of underwater sound is reported. The index gradient follows a modified hyperbolic secant profile designed to reduce aberration and suppress side lobes. The gradient index (GRIN) lens is comprised of transversely isotropic hexagonal microstructures with tunable quasi-static bulk modulus and mass density. In addition, the unit cells are impedance-matched to water and have in-plane shear modulus negligible compared to the effective bulk modulus. The flat GRIN lens is fabricated by cutting hexagonal centimeter scale hollow microstructures in aluminum plates, which are then stacked and sealed from the exterior water. Broadband focusing effects are observed within the homogenization regime of the lattice in both finite element simulations and underwater measurements (20-40 kHz). This design approach has potential applications in medical ultrasound imaging and underwater acoustic communications.

Original languageEnglish (US)
Pages (from-to)4408-4417
Number of pages10
JournalJournal of the Acoustical Society of America
Issue number6
StatePublished - Jun 1 2017

All Science Journal Classification (ASJC) codes

  • Arts and Humanities (miscellaneous)
  • Acoustics and Ultrasonics

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