[论文解读] Radiation forces and torques in optics and acoustics

Ivan Toftul, Sebastian Golat+4 more|arXiv (Cornell University)|Oct 31, 2024

Experimental and Theoretical Physics Studies被引用 7

一句话总结

一份统一综述，指出光学与声学辐射力与扭矩源于结构化波的局部能量、动量与自旋密度，并阐述理论与应用。

ABSTRACT

The mechanical action of various kinds of waves has been recognized for several centuries. The first tide of scientific interest in wave-induced forces and torques emerged at the turn of the 20th century, with the development of wave theories and the concepts of wave momentum and angular momentum. A second surge occurred in the past several decades, driven by technological breakthroughs: the invention of lasers and the controlled generation of structured wave fields. This resulted in major discoveries, including optical trapping and manipulation of small particles, from atomic to micro sizes, as well as acoustic manipulation of larger particles, including biological cells and samples. Nowadays, radiation forces and torques underpin numerous applications: optical and acoustic tweezers, acoustofluidic sorting of biological cells, optomechanical systems operating in both classical and quantum regimes, solar sails, quantum simulators, volumetric displays, etc. In this review, we present a unifying perspective on optical and acoustic forces and torques acting on various particles, addressing both their theoretical foundations and key applications. Our approach relies on the universal connection between the local energy, momentum, and spin densities of wave fields and the principal forces and torques exerted on small particles. Moreover, we describe important cases of nontrivial (e.g., lateral and pulling) forces and complex (e.g., chiral and anisotropic) particles. We also highlight significant experimental achievements involving optical and acoustic manipulation in structured wave fields. Our aim is to illuminate the common fundamental origins and close interconnections between the mechanical actions of optical and acoustic fields, thereby fostering a deeper understanding and advancing the development of optomechanical and acoustomechanical applications.

研究动机与目标

• 提供一个统一框架，将波的能量、动量与自旋密度连接到光学与声学中对粒子的力与扭矩。
• 描述规范动量与自旋密度如何决定 Rayleigh 粒子上的辐射力。
• 讨论复杂粒子（各向异性、手性、共振）下的非平凡力与扭矩。
• 总结结构场中光学与声学力的实验进展及应用。
• 突出光机和声机作用的共同物理起源及相互联系。

提出的方法

• 采用应力张量框架，将波通量与吸收、散射及由此产生的力/扭矩联系起来。
• 利用局部能量、动量与自旋密度之间的普遍联系，预测 Rayleigh 粒子上的力/扭矩。
• 描述规范动量与动量的动能动量，以及它们与 Belinfante-Rosenfeld 关系在结构场中解释力的作用。
• 将框架扩展到复杂粒子（各向异性、手性、共振）以及界面和波前整形。
• 讨论离场波、涡旋束、拉扯力及分选应用等实例。
• 给出光学与声学力/扭矩操控方面的实验成果综述。

Figure 1: Examples of manifestations of optical and acoustic forces. (a) The story started with Kepler’s 17th-century suggestion that the comet tail is directed away from the sun because of the radiation pressure from the sun light [image by Fred Espenak, NASA GSFC]. (b) Modern manipulation of diele

实验结果

研究问题

• RQ1 单色结构场的规范动量与自旋密度如何决定对小型 Rayleigh 粒子的辐射力与扭矩？
• RQ2 通过能量、动量和自旋密度连接电磁场与声场的统一形式是什么？
• RQ3 复杂粒子属性（各向异性、手性、磁电耦合）如何改变辐射力与扭矩？
• RQ4 结构字段（衰减波、涡旋束、波前整形）在实现拉扯力或分选等非平凡力中的作用？
• RQ5 将理论与光学和声学操控与分选应用联系起来的关键实验里程碑有哪些？

主要发现

• 局部规范动量与自旋密度定量地决定各向同性 Rayleigh 粒子上的辐射力与扭矩。
• 存在一个 Belinfante-Rosenfeld 关系，将动能动量、规范动量和自旋密度联系在结构场中。
• 在结构照明下，复杂粒子（包括各向异性和手性情况）产生非平凡的力和扭矩。
• 结构化波场实现拉扯力、涡旋束捕获，以及对粒子的精确光学/声学操控与分选。
• 该框架统一光学与声学辐射作用，并通过局部动力量扩展到其他波类型。
• 实验进展已经在真空中展示了 GHz 量级的光学扭矩，在声学中展示了对被困粒子的 kHz 量级扭矩。

Figure 2: ‘Executive toys’ based on the first 19th-century experiments on the mechanical action of electromagnetic and acoustic waves. (a) The Crookes radiometer employing vanes with absorbing (black) and reflecting (white) surfaces. (b) Acoustic Dvorak radiometer using Helmholtz resonators radiatin