Silva Glauber T, Lopes J Henrique, Mitri Farid G
IEEE Trans Ultrason Ferroelectr Freq Control. 2013 Jun;60(6):1207-12. doi: 10.1109/TUFFC.2013.2683.
Acoustic Bessel beams are known to produce an axial radiation force on a sphere centered on the beam axis (on-axial configuration) that exhibits both repulsor and tractor behaviors. The repulsor and the tractor forces are oriented along the beam's direction of propagation and opposite to it, respectively. The behavior of the acoustic radiation force generated by Bessel beams when the sphere lies outside the beam's axis (off-axial configuration) is unknown. Using the 3-D radiation force formulas given in terms of the partial wave expansion coefficients for the incident and scattered waves, both axial and transverse components of the force exerted on a silicone- oil sphere are obtained for a zero- and a first-order Bessel vortex beam. As the sphere departs from the beam's axis, the tractor force becomes weaker. Moreover, the behavior of the transverse radiation force field may vary with the sphere's size factor ka (where k is the wavenumber and a is the sphere radius). Both stable and unstable equilibrium regions around the beam's axis are found, depending on ka values. These results are particularly important for the design of acoustical tractor beam devices operating with Bessel beams.
已知声学贝塞尔光束会在以光束轴为中心的球体上产生轴向辐射力（轴上配置），该力表现出推斥力和牵引力行为。推斥力和牵引力分别沿光束传播方向和与之相反的方向。当球体位于光束轴之外（离轴配置）时，贝塞尔光束产生的声辐射力的行为尚不清楚。利用根据入射波和散射波的分波展开系数给出的三维辐射力公式，得到了零阶和一阶贝塞尔涡旋光束作用在硅油球体上的力的轴向和横向分量。随着球体偏离光束轴，牵引力变弱。此外，横向辐射力场的行为可能随球体的尺寸因子ka（其中k是波数，a是球体半径）而变化。根据ka值，在光束轴周围发现了稳定和不稳定的平衡区域。这些结果对于设计使用贝塞尔光束的声学牵引光束装置尤为重要。
