Figure 1

(a) Three-dimensional map of experimental field amplitude on the imaging side of the water-methanol-steel flat lens at a frequency of 530 kHz. (b) Field amplitude through the focus along the direction parallel to the lens surface. The data fit to a sinc function (solid line) gives a half width of the primary peak, $\Delta /2$, of $0.37\lambda$. (c) Field amplitude through the focus along the direction perpendicular to the lens surface. The surface is located at $z=0$.Reuse & Permissions

Figure 2

Band structure of the methanol-steel PC in the $\Gamma M$ direction of the first BZ (left panel) and transmission coefficient for a 6-layer crystal along the same direction (right panel): symbols, experimental data; solid lines, FDTD calculation; dashed line, homogeneous water. The inset illustrates the phononic crystal structure and the associated first Brillouin zone.Reuse & Permissions

Figure 3

(a) Three-dimensional map of the normalized average absolute value of pressure calculated via the FDTD method. The source frequency is 530 kHz. (b) Normalized average absolute value of the pressure along a line parallel to the lens through the center of the focal point. The half-width $\Delta /2$ of the primary peak is $0.35\lambda$. The offset in lateral position of the focus is due to the FDTD staggered grid that ensures numerical stability. (c) Same as (b) but along a direction perpendicular to the lens. The surface of the lens is located at $z=0$.Reuse & Permissions

Figure 4

(a) Calculated band structure of methanol-steel PC slab immersed in water (inset: phononic crystal, left block; water, right block) for wave vectors parallel to the slab surface (transverse wave vector along $\Gamma K$ direction). The long dashed line corresponds to sound propagation in water. (b) Magnification of the region enclosed by the box in (a). The arrow points to a bound slab phonon mode near 510 kHz.Reuse & Permissions

Figure 5

Contour maps of the normalized average absolute value of pressure calculated via FDTD (a) at a frequency of 530 kHz for the PC lens imaging the 0.55-mm-wide line source located at 0.1 mm from the left lens surface and centered with respect to a surface cylinder at $x=0$, (b) same as (a) but with the source shifted down by $a_s/2$ in the direction parallel to the surface of the lens, and (c), (d) for two lenses with positional disorder of the steel rods showing imperfect focusing (c) and loss of focusing (d). The positional disorder in the numerical model has a standard deviation of 5%, which corresponds to an upper limit for the experimental crystal, as the disorder was measured only on the surface. Because of the fabrication method, the disorder at the surface is greater than in the interior.Reuse & Permissions