Figure 23.
(a1) Two-component PnC comprised of a square lattice of hard cylinders embedded in a softer polymer matrix and (a2) its phononic band structure with displacement fields corresponding to the two eigenmodes, A and B. A PnBG (
= 0.53) is created from Bragg scattering of the impedance contrast 
of 6. (b1) Three-component PnC having an additional concentric very soft layer that serves to weakly couple the cylinders and the matrix and (b2) its band structure with displacement fields corresponding to the eigenmodes, C and D. A low frequency resonant PnBG (
= 0.7) is created by using a soft shell (
) with impedance contrasts of 
of 50 and 
of 9. Adapted from.391 The color map for each mode indicates zero (blue) to a maximum displacement amplitude (red) with local directions and magnitudes of the displacements given by the arrows.