Figure 1
From: Broadband All-angle Negative Refraction by Optimized Phononic Crystals
(a) Schematic demonstration of negative refraction. Red and green lines denote EFC for air and PnC, respectively. The black arrows indicate directions of energy flow when acoustic waves enter PnC from air with the interface normal parallel to ΓM. (b) The unit cell of the optimized PnC with square lattice constant a. The grey and white denote steel and air respectively. (c) The first phononic band of the initial (dotted blue line) and optimized (solid blue line) structure, initial (dotted green line) and optimized (dashed green line) radius of EFC curvature of equifrequency contours along ΓM direction and dispersion relation in air which is shifted to M point (dashed red line). The initial and optimized upper and lower limit are indicated by blue and red triangles. (d) The complete 3D band structure and EFCs of the optimized PnC.
