Resonant slow modes in phononic crystal plates with periodic membranes

We propose a distinct phononic-crystal plate structure that comprises periodic circular membranes and present the theoretical and experimental investigation of elastic-wave propagation in the structure. Owing to the weak rigidity of the membranes, there are slow propagating resonant modes appended to the band structure. These resonant modes can also be engineered to locate inside the complete band gap. The frequencies and group velocities can be tuned by changing the membrane thickness and radius. By utilizing the laser-ultrasonic technique, the resonance and slow group velocity are observed. The measured results are in good agreement with the theoretical predictions. (C) 2010 American Institute of Physics. [doi:10.1063/1.3464955]