Fig. 7: The broadband focusing performance of the unidirectional focusing lens (UFL).
From: Unidirectional focusing for broadband Lamb guided wave based on mode conversion
a The full width at half maximum (FWHM) of the UFL at 253.2 kHz, 266.8 kHz, 282.9 kHz, 299.5 kHz, 315.5 kHz, 328.5 kHz, and 345 kHz. The shaded area indicates the subwavelength FWHM within 4.51–5.4 mm. b Normalized displacement field profiles of the UFL along x-direction, the black short dash lines denote the designed focal length F = 25.04 mm at 328.5 kHz.
