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Focusing a Two-Dimensional Acoustic Vortex Beyond Diffraction Limit on an Ultrathin Structured Surface
Physical Review Applied ( IF 4.6 ) Pub Date : 2021-01-11 , DOI: 10.1103/physrevapplied.15.014015
Jing-jing Liu , Bin Liang , Jian-chun Cheng

We propose and experimentally demonstrate a mechanism for focusing two-dimensional (2D) vortex for airborne sound beyond diffraction limit on an ultrathin structured surface in free space. A simple design of unit cell is presented as a practical implementation, which is capable of exciting evanescent wave and modulating its propagation phase over full 0-to-2π range. By analytically deriving the dispersion relationship and desired azimuthal distribution of effective parameters, we elucidate how to guide the propagation of excited evanescent waves in the vicinity of an unbounded surface decorated with designed structures and focus such surface vortex within a target region despite its compactness and nonaxisymmetry. The effectiveness of our mechanism is demonstrated numerically and experimentally via production and confinement of 2D vortex on a square surface at subwavelength spatial resolution. We anticipate our methodology with no need of a 2D system, bulky device size, geometric symmetry, active elements, or complicated phased array to offer new possibilities for the miniaturization and integration of planar vortex devices and may promote their on-chip applications in various fields such as by significantly boosting the information density and manipulation precision.

中文翻译:

将超薄结构化表面上的二维声涡旋聚焦在衍射极限之外

我们提出并实验证明了一种机制,用于将二维(2D)涡旋聚焦在自由空间中的超薄结构表面上,以使超过衍射极限的空气传播声聚焦。单元电池的一个简单的设计是作为一个实际实现中,它是能够激发渐逝波和调制其传播相位在整个0到2的π范围。通过分析得出有效参数的色散关系和所需的方位角分布,我们阐明了如何引导激发的van逝波在设计结构装饰的无边界表面附近的传播,以及如何使这种表面涡旋集中在目标区域内,尽管其紧凑性和非轴对称性。通过在亚波长空间分辨率下在正方形表面上产生和限制2D涡旋,在数值和实验上证明了我们机理的有效性。我们预期我们的方法将不需要2D系统,庞大的设备尺寸,几何对称性,有源元素,
更新日期:2021-01-12
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