Multiple light scattering and optomechanical forces

Abstract

Abstract. When off-resonant light travels through a transparent medium, light scattering is the primary optical process to occur. Multiple-particle events are relatively rare in optically dilute systems: scattering generally takes place at individual atomic or molecular centers. Several well-known phenomena result from such single-center interactions, including Rayleigh and Raman scattering, and the optomechanical forces responsible for optical tweezers. Other, less familiar effects may arise in circumstances where throughput radiation is able to simultaneously engage with two or more scattering sites in close, nanoscale, proximity. Exhibiting the distinctive near-field electromagnetic character, inter-particle interactions such as optical binding and a variety of inelastic bimolecular processes can then occur. Although the theory for each two-center process is well established, the connectivity of their mechanisms has not received sufficient attention. To address this deficiency, and to consider the issues that ensue, it is expedient to represent the various forms of multi-particle light scattering in terms of transitions between different radiation states. The corresponding quantum amplitudes, registering the evolution of photon trajectories through the material system, can be calculated using the tools of quantum electrodynamics. Each of the potential outcomes for multi-particle scattering generates a set of amplitudes corresponding to different orderings of the constituent photon-matter interactions. Performing the necessary sums over quantum pathways between radiation states is expedited by a state-sequence development, this formalism also enabling the identification of intermediate states held in common by different paths. The results reveal the origin and consequences of linear momentum conservation, and they also offer new insights into the behavior of light between closely neighboring scattering events.

Perspective: Quantum Hamiltonians for optical interactions

“…This is a surprising claim, since over its close to sixty year history there has been a host of applications to which the PZW Hamiltonian has been applied, which have agreed with, or led to predictions borne out by experiment. There are many hundreds of papers in the established literature citing the original work, bearing testimony to its efficacy and success; numerous significant applications and advances have built upon it, even over the last decade [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37]. Indeed we know of no cases where the theory has been faulted by experimental studywhich would usually be the condition to invite reappraisal of a previously successful theory.…”

Self-Organization of Metal Nanoparticles in Light: Electrodynamics–Molecular Dynamics Simulations and Optical Binding Experiments

“…Similar to molecular isomers with the same chemical formula but different atomic arrangements, metal NPs have shown the ability to self-organize into a great variety of photonic clusters (i.e., optical matter isomers) by optical binding. − However, accurately predicting the optical matter isomers is not a trivial task. Due to the nature of multibody and directional interactions, the complexity of optical binding increases nonlinearly with the number of particles involved. , In pioneering work, Ng et al applied a multiple scattering technique to predict various geometric configurations of photonic clusters formed by dielectric microspheres . Later we developed a coupled-dipole model for optical binding of multiple NPs .…”

“…Due to the nature of multibody and directional interactions, the complexity of optical binding increases nonlinearly with the number of particles involved. 3,11 In pioneering work, Ng et al applied a multiple scattering technique to predict various geometric configurations of photonic clusters formed by dielectric microspheres. 12 Later we developed a coupled-dipole model for optical binding of multiple NPs.…”

Structured light, transmission, and scattering

“…Therefore it is expedient, to preserve rather than lose generality, to utilize a standard plane wave basis for effecting the virtual photon summations over wave-vector (with arbitrary direction and magnitude) and polarization. Summing over all time-ordered contributions, and using calculational methods recently developed and described in detail elsewhere, [24,25] the matrix element duly emerges as follows:…”