Confinement of acoustic fields in a honeycomb phononic crystal slab

We demonstrate the confinement of acoustic waves in a microscopic phononic crystal slab consisting of a honeycomb array of holes in silicon. The acoustic field is measured on the sample surface at frequencies up to 1GHz by means of an ultrafast optical technique. Using temporal Fourier transforms, the confinement is shown to depend on frequency, and a phononic band gap is identified. Finite element simulations are performed and used to analyze the results.