Band gaps in phononic crystals: Generation mechanisms and interaction effects

C. Croënne, E. J. S. Lee, Hefei Hu, and J. H. Page

Characteristic properties of gaps of different origins are investigated and compared, for a 3D crystal of tungsten carbide beads in water, a 2D crystal of nylon rods in water, and a 3D opal-like structure of weakly sintered aluminum beads. For the second type of crystal, it is shown that Bragg and hybridization gaps can be overlapped, allowing the study of the interaction between these two mechanisms. Atypical dispersion characteristics are demonstrated near the resonance frequency.

AIP Advances 1, 041401 (2011)

Negative effective dynamic mass-density and stiffness: Micro-architecture and phononic transport in periodic composites

Sia Nemat-Nasser and Ankit Srivastava

We calculate negative effective density and negative effective compliance for a layered composite and show that the frequency-dependent effective properties remain positive for cases which lack the possibility of localized resonances whereas they may become negative for cases where there exists a possibility of local resonance below the length-scale of the wavelength. We also show that the introduction of damping in the system considerably affects the effective properties in the frequency region close to the resonance.

AIP Advances 1, 041502 (2011)

Realization of a 33 GHz phononic crystal fabricated in a freestanding membrane

Drew F. Goettler, Mehmet F. Su, Charles M. Reinke, Seyedhamidreza Alaie, Patrick E. Hopkins, Roy H. Olsson, III, Ihab El-Kady, and Zayd C. Leseman

A 2D simple cubic lattice phononic crystal created by nanofabrication with a focused ion beam and operating at 33 GHz is reported. A freestanding membrane of silicon is ion-milled to create a simple cubic array of 32 nm diameter holes that are subsequently backfilled with tungsten to create inclusions at a spacing of 100 nm. Simulations are used to predict the operating frequency and to show that milling a freestanding membrane has a unique characteristic; the exit via has a conical shape, or trumpet-like appearance.

AIP Advances 1, 042001 (2011)