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Reflected wavefront manipulation based on ultrathin planar acoustic metasurfaces.

Li Y, Liang B, Gu ZM, Zou XY, Cheng JC - Sci Rep (2013)

Bottom Line: Here, we theoretically demonstrate that the generalized Snell's law can be achieved for reflected acoustic waves based on ultrathin planar acoustic metasurfaces.The metasurfaces are constructed with eight units of a solid structure to provide discrete phase shifts covering the full 2π span with steps of π/4 by coiling up the space.Our results could open up a new avenue for acoustic wavefront engineering and manipulations.

View Article: PubMed Central - PubMed

Affiliation: 1] Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China [2] State Key Laboratory of Acoustics, Chinese Academy of Sciences, Beijing 100190, P. R. China.

ABSTRACT
The introduction of metasurfaces has renewed the Snell's law and opened up new degrees of freedom to tailor the optical wavefront at will. Here, we theoretically demonstrate that the generalized Snell's law can be achieved for reflected acoustic waves based on ultrathin planar acoustic metasurfaces. The metasurfaces are constructed with eight units of a solid structure to provide discrete phase shifts covering the full 2π span with steps of π/4 by coiling up the space. By careful selection of the phase profiles in the transverse direction of the metasurfaces, some fascinating wavefront engineering phenomena are demonstrated, such as anomalous reflections, conversion of propagating waves into surface waves, planar aberration-free lens and nondiffracting Bessel beam generated by planar acoustic axicon. Our results could open up a new avenue for acoustic wavefront engineering and manipulations.

No MeSH data available.


Acoustic axicon for the non-diffracting Bessel beam.(a) Schematic diagram of the design of acoustic axicon. The green cone-like line with base angle  is the desired equiphase surface for the acoustic axicon so that the phase shift at  should be proportional to the length of the red line . Here, the half-height of the axicon h is selected to be 100 cm. (b) The theoretical continuous phase shift (red dots) and the discrete phase shift provided by the metasurface (blue squares) along the y direction. (c) Spatial distribution of the intensity field  for the designed axicon with . (d) Transverse cross-section of the intensity profile at x = 240 cm from the metasurfaces within the DOF.
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f5: Acoustic axicon for the non-diffracting Bessel beam.(a) Schematic diagram of the design of acoustic axicon. The green cone-like line with base angle is the desired equiphase surface for the acoustic axicon so that the phase shift at should be proportional to the length of the red line . Here, the half-height of the axicon h is selected to be 100 cm. (b) The theoretical continuous phase shift (red dots) and the discrete phase shift provided by the metasurface (blue squares) along the y direction. (c) Spatial distribution of the intensity field for the designed axicon with . (d) Transverse cross-section of the intensity profile at x = 240 cm from the metasurfaces within the DOF.

Mentions: To design a flat acoustic axicon with a base angle β, the conical phase profile should be employed so that the phase shift ϕ(y) at every point along the direction satisfy the following equation By applying the aforementioned rule, the theoretical continuous phase shift (red dots) and the discrete phase shifts (blue dots) provided by the acoustic metasurfaces are shown in Fig. 5(b). Spatial intensity distribution of the acoustic axicon and the transverse cross-section of the intensity profile at x = 240 cm from the metasurface are shown in Figs. 5(c) and 5(d), respectively. Due to the good performance of the proposed acoustic metasurfaces, it is not surprising to observe a non-diffracting Bessel beam propagating along the x direction with a relatively long distance.


Reflected wavefront manipulation based on ultrathin planar acoustic metasurfaces.

Li Y, Liang B, Gu ZM, Zou XY, Cheng JC - Sci Rep (2013)

Acoustic axicon for the non-diffracting Bessel beam.(a) Schematic diagram of the design of acoustic axicon. The green cone-like line with base angle  is the desired equiphase surface for the acoustic axicon so that the phase shift at  should be proportional to the length of the red line . Here, the half-height of the axicon h is selected to be 100 cm. (b) The theoretical continuous phase shift (red dots) and the discrete phase shift provided by the metasurface (blue squares) along the y direction. (c) Spatial distribution of the intensity field  for the designed axicon with . (d) Transverse cross-section of the intensity profile at x = 240 cm from the metasurfaces within the DOF.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3756345&req=5

f5: Acoustic axicon for the non-diffracting Bessel beam.(a) Schematic diagram of the design of acoustic axicon. The green cone-like line with base angle is the desired equiphase surface for the acoustic axicon so that the phase shift at should be proportional to the length of the red line . Here, the half-height of the axicon h is selected to be 100 cm. (b) The theoretical continuous phase shift (red dots) and the discrete phase shift provided by the metasurface (blue squares) along the y direction. (c) Spatial distribution of the intensity field for the designed axicon with . (d) Transverse cross-section of the intensity profile at x = 240 cm from the metasurfaces within the DOF.
Mentions: To design a flat acoustic axicon with a base angle β, the conical phase profile should be employed so that the phase shift ϕ(y) at every point along the direction satisfy the following equation By applying the aforementioned rule, the theoretical continuous phase shift (red dots) and the discrete phase shifts (blue dots) provided by the acoustic metasurfaces are shown in Fig. 5(b). Spatial intensity distribution of the acoustic axicon and the transverse cross-section of the intensity profile at x = 240 cm from the metasurface are shown in Figs. 5(c) and 5(d), respectively. Due to the good performance of the proposed acoustic metasurfaces, it is not surprising to observe a non-diffracting Bessel beam propagating along the x direction with a relatively long distance.

Bottom Line: Here, we theoretically demonstrate that the generalized Snell's law can be achieved for reflected acoustic waves based on ultrathin planar acoustic metasurfaces.The metasurfaces are constructed with eight units of a solid structure to provide discrete phase shifts covering the full 2π span with steps of π/4 by coiling up the space.Our results could open up a new avenue for acoustic wavefront engineering and manipulations.

View Article: PubMed Central - PubMed

Affiliation: 1] Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, P. R. China [2] State Key Laboratory of Acoustics, Chinese Academy of Sciences, Beijing 100190, P. R. China.

ABSTRACT
The introduction of metasurfaces has renewed the Snell's law and opened up new degrees of freedom to tailor the optical wavefront at will. Here, we theoretically demonstrate that the generalized Snell's law can be achieved for reflected acoustic waves based on ultrathin planar acoustic metasurfaces. The metasurfaces are constructed with eight units of a solid structure to provide discrete phase shifts covering the full 2π span with steps of π/4 by coiling up the space. By careful selection of the phase profiles in the transverse direction of the metasurfaces, some fascinating wavefront engineering phenomena are demonstrated, such as anomalous reflections, conversion of propagating waves into surface waves, planar aberration-free lens and nondiffracting Bessel beam generated by planar acoustic axicon. Our results could open up a new avenue for acoustic wavefront engineering and manipulations.

No MeSH data available.