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Three-dimensional collimated self-accelerating beam through acoustic metascreen.

Li Y, Assouar MB - Sci Rep (2015)

Bottom Line: Acoustic metascreen with deep subwavelength spatial resolution, composed of hybrid structures combining four Helmholtz resonators and a straight pipe, transmitting sound efficiently and shifting fully the local phase is evidenced.With an extra phase profile provided by the metascreen, the transmitted sound can be tuned to propagate along arbitrary caustic curvatures to form a focused spot.Due to the caustic nature, the formed beam possesses the capacities of bypassing obstacles and holding the self-healing feature, paving then a new way for wave manipulations and indicating various potential applications, especially in the fields of ultrasonic imaging, diagnosis and treatment.

View Article: PubMed Central - PubMed

Affiliation: CNRS, Institut Jean Lamour, Vandoeuvre-lès-Nancy F-54500, France.

ABSTRACT
We report the generation of three-dimensional acoustic collimated self-accelerating beam in non-paraxial region with sourceless metascreen. Acoustic metascreen with deep subwavelength spatial resolution, composed of hybrid structures combining four Helmholtz resonators and a straight pipe, transmitting sound efficiently and shifting fully the local phase is evidenced. With an extra phase profile provided by the metascreen, the transmitted sound can be tuned to propagate along arbitrary caustic curvatures to form a focused spot. Due to the caustic nature, the formed beam possesses the capacities of bypassing obstacles and holding the self-healing feature, paving then a new way for wave manipulations and indicating various potential applications, especially in the fields of ultrasonic imaging, diagnosis and treatment.

No MeSH data available.


Related in: MedlinePlus

The metascreen is constructed by a series of individual elements.(a) Three-dimensional configuration of two adjacent axisymmetric elements. Incident wave propagating along +z direction penetrates metascreen through the slit (straight pipe) between the adjacent elements. (b) Schematic digram of an individual element in r − z plane (width w = λ/10 and height h = λ/2) consisting of four Helmholtz resonators (HRs) and a straight pipe (width w1). The width and height of the throat (cavity) of the HRs are w2 (w3) and h2 (h3). The HRs are formed by solid materials with identical height h1 = w2. The distance from the individual element to the axis is sn, which is the integral multiple of w. (c) The phase shift map and (d) the transmission coefficient map of the presented metascreen as functions of sn/w and w1/w. The geometric parameters in the simulations are fixed as (h1, h2, h3, ) = (0.01, 0.03, 0.235, 0.24)h. The hollow circle point indicates the w1 and sn of the elements achieving the desired phase profile from Eq. 4 with rb = 2.5λ.
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f2: The metascreen is constructed by a series of individual elements.(a) Three-dimensional configuration of two adjacent axisymmetric elements. Incident wave propagating along +z direction penetrates metascreen through the slit (straight pipe) between the adjacent elements. (b) Schematic digram of an individual element in r − z plane (width w = λ/10 and height h = λ/2) consisting of four Helmholtz resonators (HRs) and a straight pipe (width w1). The width and height of the throat (cavity) of the HRs are w2 (w3) and h2 (h3). The HRs are formed by solid materials with identical height h1 = w2. The distance from the individual element to the axis is sn, which is the integral multiple of w. (c) The phase shift map and (d) the transmission coefficient map of the presented metascreen as functions of sn/w and w1/w. The geometric parameters in the simulations are fixed as (h1, h2, h3, ) = (0.01, 0.03, 0.235, 0.24)h. The hollow circle point indicates the w1 and sn of the elements achieving the desired phase profile from Eq. 4 with rb = 2.5λ.

Mentions: To realize the desired phase profile shown in Fig. 1(b), we use a three-dimensional subwavelength hybrid elements to construct the metascreen. Figure 2(a) illustrates two adjacent elements in three-dimensional space to demonstrate the configuration of the metascreen. Figure 2(b) shows an individual element in r − z plane consisting of four Helmholtz resonator (HRs) and a straight pipe. Here the series connection of the HRs acts as acoustic resistance to shift the phase of the incident wave28. The cavity series has a tunable width w3 to span the phase shift over a full 2π range. The functionality of the straight pipe with fixed length of λ/2 supporting Fabry-Pérot resonance293031 is to provide coupling resonances keeping relatively impedance matching21. Considering the fact that the transmission coefficient is determined by the coupling resonances between the Fabry-Pérot and Helmholtz resonance, the number of the HRs is selected to be four in order to provide enough coupled resonances so that transmission coefficient can keep high value while covering 2π range21.


Three-dimensional collimated self-accelerating beam through acoustic metascreen.

Li Y, Assouar MB - Sci Rep (2015)

The metascreen is constructed by a series of individual elements.(a) Three-dimensional configuration of two adjacent axisymmetric elements. Incident wave propagating along +z direction penetrates metascreen through the slit (straight pipe) between the adjacent elements. (b) Schematic digram of an individual element in r − z plane (width w = λ/10 and height h = λ/2) consisting of four Helmholtz resonators (HRs) and a straight pipe (width w1). The width and height of the throat (cavity) of the HRs are w2 (w3) and h2 (h3). The HRs are formed by solid materials with identical height h1 = w2. The distance from the individual element to the axis is sn, which is the integral multiple of w. (c) The phase shift map and (d) the transmission coefficient map of the presented metascreen as functions of sn/w and w1/w. The geometric parameters in the simulations are fixed as (h1, h2, h3, ) = (0.01, 0.03, 0.235, 0.24)h. The hollow circle point indicates the w1 and sn of the elements achieving the desired phase profile from Eq. 4 with rb = 2.5λ.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664955&req=5

f2: The metascreen is constructed by a series of individual elements.(a) Three-dimensional configuration of two adjacent axisymmetric elements. Incident wave propagating along +z direction penetrates metascreen through the slit (straight pipe) between the adjacent elements. (b) Schematic digram of an individual element in r − z plane (width w = λ/10 and height h = λ/2) consisting of four Helmholtz resonators (HRs) and a straight pipe (width w1). The width and height of the throat (cavity) of the HRs are w2 (w3) and h2 (h3). The HRs are formed by solid materials with identical height h1 = w2. The distance from the individual element to the axis is sn, which is the integral multiple of w. (c) The phase shift map and (d) the transmission coefficient map of the presented metascreen as functions of sn/w and w1/w. The geometric parameters in the simulations are fixed as (h1, h2, h3, ) = (0.01, 0.03, 0.235, 0.24)h. The hollow circle point indicates the w1 and sn of the elements achieving the desired phase profile from Eq. 4 with rb = 2.5λ.
Mentions: To realize the desired phase profile shown in Fig. 1(b), we use a three-dimensional subwavelength hybrid elements to construct the metascreen. Figure 2(a) illustrates two adjacent elements in three-dimensional space to demonstrate the configuration of the metascreen. Figure 2(b) shows an individual element in r − z plane consisting of four Helmholtz resonator (HRs) and a straight pipe. Here the series connection of the HRs acts as acoustic resistance to shift the phase of the incident wave28. The cavity series has a tunable width w3 to span the phase shift over a full 2π range. The functionality of the straight pipe with fixed length of λ/2 supporting Fabry-Pérot resonance293031 is to provide coupling resonances keeping relatively impedance matching21. Considering the fact that the transmission coefficient is determined by the coupling resonances between the Fabry-Pérot and Helmholtz resonance, the number of the HRs is selected to be four in order to provide enough coupled resonances so that transmission coefficient can keep high value while covering 2π range21.

Bottom Line: Acoustic metascreen with deep subwavelength spatial resolution, composed of hybrid structures combining four Helmholtz resonators and a straight pipe, transmitting sound efficiently and shifting fully the local phase is evidenced.With an extra phase profile provided by the metascreen, the transmitted sound can be tuned to propagate along arbitrary caustic curvatures to form a focused spot.Due to the caustic nature, the formed beam possesses the capacities of bypassing obstacles and holding the self-healing feature, paving then a new way for wave manipulations and indicating various potential applications, especially in the fields of ultrasonic imaging, diagnosis and treatment.

View Article: PubMed Central - PubMed

Affiliation: CNRS, Institut Jean Lamour, Vandoeuvre-lès-Nancy F-54500, France.

ABSTRACT
We report the generation of three-dimensional acoustic collimated self-accelerating beam in non-paraxial region with sourceless metascreen. Acoustic metascreen with deep subwavelength spatial resolution, composed of hybrid structures combining four Helmholtz resonators and a straight pipe, transmitting sound efficiently and shifting fully the local phase is evidenced. With an extra phase profile provided by the metascreen, the transmitted sound can be tuned to propagate along arbitrary caustic curvatures to form a focused spot. Due to the caustic nature, the formed beam possesses the capacities of bypassing obstacles and holding the self-healing feature, paving then a new way for wave manipulations and indicating various potential applications, especially in the fields of ultrasonic imaging, diagnosis and treatment.

No MeSH data available.


Related in: MedlinePlus