Department of Mechanical Engineering, University of Bristol. University Walk, Bristol BS8 1TR, United Kingdom.
Phys Rev Lett. 2018 Jan 26;120(4):044301. doi: 10.1103/PhysRevLett.120.044301.
Acoustic vortices can transfer angular momentum and trap particles. Here, we show that particles trapped in airborne acoustic vortices orbit at high speeds, leading to dynamic instability and ejection. We demonstrate stable trapping inside acoustic vortices by generating sequences of short-pulsed vortices of equal helicity but opposite chirality. This produces a "virtual vortex" with an orbital angular momentum that can be tuned independently of the trapping force. We use this method to adjust the rotational speed of particles inside a vortex beam and, for the first time, create three-dimensional acoustics traps for particles of wavelength order (i.e., Mie particles).
声涡旋可以传递角动量并捕获粒子。在这里，我们表明，被困在空气中声涡旋中的粒子以高速旋转，导致动态不稳定性和喷射。我们通过产生具有相同螺旋但相反手性的短脉冲涡旋序列来证明声涡旋内的稳定捕获。这产生了一个具有轨道角动量的“虚拟涡旋”，该角动量可以与捕获力独立调节。我们使用这种方法来调整涡旋光束中粒子的旋转速度，并首次为波长量级的粒子创建三维声阱（即 Mie 粒子）。
