Figure 2

Acoustic transmission and distribution of the displacement field for sample 2. (Top) Scheme of a structure consisting of two mirrors with six periods of layers a and b enclosing a defect layer of higher porosity between them. (Middle) Measured acoustic wave transmission spectrum through the sample (solid line). The dashed curve is the calculated spectrum (see text for details). (Bottom) In solid line, squared phonon displacement corresponding to the first (thick line) and second (thin line) modes at 1.01 and 1.27 GHz, respectively. The dashed line represent the layer acoustic impedance.