Three-dimensional collimated self-accelerating beam through acoustic metascreen.

We report the generation of three-dimensional acoustic collimated self-accelerating beam in non-paraxial region with sourceless metascreen. Acoustic metascreen with deep subwavelength spatial resolution, composed of hybrid structures combining four Helmholtz resonators and a straight pipe, transmitting sound efficiently and shifting fully the local phase is evidenced. With an extra phase profile provided by the metascreen, the transmitted sound can be tuned to propagate along arbitrary caustic curvatures to form a focused spot.

The use of microwave plasma-assisted CVD on nanostructured iron catalysts to grow isolated bundles of carbon nanotubes.

Catalysts play a key role in the growth of carbon nanotubes. The microwave plasma-assisted chemical vapor deposition (MPACVD) method is now commonly used for directional and conformal growth of carbon nanotubes (CNTs) on substrates. In this work, we report on the effect of H(2) plasma pre-treatment on the diameter and density of iron catalyst nanoparticles for different iron layer thicknesses in order to grow isolated bundles of CNTs.

Combination of e-beam lithography and of high velocity AIN/diamond-layered structure for SAW filters in X band.

In this work, we report on the fabrication results of surface acoustic wave (SAW) devices operating at frequencies up to 8 GHz. In previous work, we have shown that high acoustic velocities (9 to 12 km/s) are obtained from the layered AIN/diamond structure. The interdigital transducers (IDTs) made of aluminium with resolutions up to 250 nm were successfully patterned on AIN/diamond-layered structures with an adapted technological process.