Fig. 2
2D deflecting and focusing of ultrasound. a Experimental setup showing a soft porous GRIN metasurface covering a large rectangular ultrasonic transducer immersed in a large water tank. A tiny hydrophone is mounted on motorized linear stages to scan the acoustic pressure field in the XZ plane (60 mm × 100 mm) emerging from the metasurface (shaded blue area). b–d Snapshots of the measured pressure fields shown at a given time without any sample (b), with the deflecting metasurface (c), and with the focusing metasurface (d) (corresponding videos are shown in Supplementary Movies 1, 2 and 3). Simulated (e) and measured (f) acoustic field patterns extracted from fast Fourier transforms performed at 90 kHz on the signals recorded for the focusing metasurface (d). Measured (red diamonds) and simulated (black line) normalized amplitude field distributions along the Z-axis for X = 0 mm (g) and along the X-axis for Z = 44 mm (h). The full widths at half maximum peaks are 4.9λ0 and 0.8λ0 along the Z-axis and X-axis, respectively
