Evidence of ultrasonic band gap in aluminum phononic crystal beam

In this paper, we prove theoretically and experimentally the existence of complete ultrasonic band gap in phononic crystal beam. The phononic beam structure studied is composed of a linear lattice array of square pillars on a beam, made with aluminum-fortal easily machinable at centimetric scale. Ultrasonic characterization of phononic beam guides shows the existence of a frequency range where the transmitted signals are strongly attenuated, due to the presence of ultrasonic band gap, in agreement with theoretical results predicted by finite element simulation. These structures present a potential for the use as energy loss reduction in micromechanical resonators at high frequency regime.