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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.


Related in: MedlinePlus

The generalized Snell's law of reflection and anomalous reflections.(a) Schematics for the derivation of the angle of reflection. ϕ and ϕ + dϕ are the phases at the two cross points separated by dy along the y direction. θr represents the anomalous reflection angle induced by the discrete phase shifts. (b) Pressure field pattern for the gradient phase profile of . The black arrows refer to the theoretical value of the reflected angle.
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f2: The generalized Snell's law of reflection and anomalous reflections.(a) Schematics for the derivation of the angle of reflection. ϕ and ϕ + dϕ are the phases at the two cross points separated by dy along the y direction. θr represents the anomalous reflection angle induced by the discrete phase shifts. (b) Pressure field pattern for the gradient phase profile of . The black arrows refer to the theoretical value of the reflected angle.

Mentions: The realization of 2π range phase shifts for the reflected acoustic waves allows us to revisit the Snell's law by selecting appropriately phase profile. Figure 2(a) illustrates the schematic diagram for the derivation of the generalized Snell's law. Considering the acoustic waves with normal incidence along the −x direction, due to the existing of discrete phase shifts along the y direction, the angle of the reflected wave θr (measured from the x direction) can be deduced by applying Fermat's principle1: where ϕ(y), dy represent the phase shift and the distance between two cross points along the y direction respectively, and k = 2π/λ is the wave vector in air. Equation (1) implies that the reflected angle can be engineered freely by designing the suitable phase profile along the y direction.


Reflected wavefront manipulation based on ultrathin planar acoustic metasurfaces.

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

The generalized Snell's law of reflection and anomalous reflections.(a) Schematics for the derivation of the angle of reflection. ϕ and ϕ + dϕ are the phases at the two cross points separated by dy along the y direction. θr represents the anomalous reflection angle induced by the discrete phase shifts. (b) Pressure field pattern for the gradient phase profile of . The black arrows refer to the theoretical value of the reflected angle.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: The generalized Snell's law of reflection and anomalous reflections.(a) Schematics for the derivation of the angle of reflection. ϕ and ϕ + dϕ are the phases at the two cross points separated by dy along the y direction. θr represents the anomalous reflection angle induced by the discrete phase shifts. (b) Pressure field pattern for the gradient phase profile of . The black arrows refer to the theoretical value of the reflected angle.
Mentions: The realization of 2π range phase shifts for the reflected acoustic waves allows us to revisit the Snell's law by selecting appropriately phase profile. Figure 2(a) illustrates the schematic diagram for the derivation of the generalized Snell's law. Considering the acoustic waves with normal incidence along the −x direction, due to the existing of discrete phase shifts along the y direction, the angle of the reflected wave θr (measured from the x direction) can be deduced by applying Fermat's principle1: where ϕ(y), dy represent the phase shift and the distance between two cross points along the y direction respectively, and k = 2π/λ is the wave vector in air. Equation (1) implies that the reflected angle can be engineered freely by designing the suitable phase profile along the y direction.

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.


Related in: MedlinePlus