Wave dispersion tailoring in an elastic waveguide by phononic crystals

Waveguides may inevitably excite undesired modes and induce dispersion-related distortion. This is true when an elastic homogeneous waveguide is used to carry a pulse of which the center frequency is above its cutoff frequency. We show that these problems can be avoided if a properly-tailored phononic crystal (PC) structure is inserted inside a waveguide. In engineering the PC, we open the band gap of the undesired wave mode and make the dispersion curve of the desired wave branch straight in a target frequency band. Numerical simulations and ultrasonic experiments using the engineered PC confirmed the validity of the proposed approach. (C) 2013 AIP Publishing LLC.