Extraordinary Acoustic Transmission through a 1D Grating with Very Narrow Apertures

Recently, there has been an increased interest in studying extraordinary optical transmission (EOT) through subwavelength aperture arrays perforated in a metallic film. In this Letter, we report that the transmission of an incident acoustic wave through a one-dimensional acoustic grating can also be drastically enhanced. This extraordinary acoustic transmission (EAT) has been investigated both theoretically and experimentally, showing that the coupling between the diffractive wave and the wave-guide mode plays an important role in EAT. This phenomenon can have potential applications in acoustics and also might provide a better understanding of EOT in optical subwavelength systems.

Figure 1

(a) Numerical (black curve) and experimental (gray curve, red online) zero-order transmission spectra for a rectangular grating with the size of 4 mm, the period of 4.5 mm. The Wood’s anomaly is indicated by an arrow. The upper panel is the sketch of the gratings. (b) The spatial intensity distribution of the pressure field in the grating at the wavelength of $2.02d$ (b1) and $1.09d$ (b2).

Figure 2

(a) Theoretical and (b) experimental angular dependences of zero-order transmission spectra for the rectangular grating. Insets are the zoomed-in figures.

Figure 3

(a) Theoretical and (b) experimental zero-order transmission spectra with different grating thickness. The Wood’s anomaly is denoted by white dotted line and the black dotted line denotes the track of the fundamental resonant mode. (c) Theoretical (black curve) and experimental (gray curve, red online) zero-order transmission spectra with grating thickness $h=8$, 4, 2 mm.

Figure 4

(a) The dependence of the phase of the resonant factor $\gamma$ (gray curve, red online) on the wavelength, and the zero-order transmission spectra (black curve) for the grating. (b) The dependence of the enhancement factor of diffraction $F$ ($\lambda$) on the wavelength (gray curve, red online), and the zero-order transmission spectra (black curve) for the grating. The light gray curve (green online) is the wavelength dependence of the normalized intensity of the pressure field inside the aperture.