Internal flows and energy circulation in light beams

Bekshaev, A. Ya.; Bliokh, Konstantin Y.; Soskin, M. S.

doi:10.1088/2040-8978/13/5/053001

Cited by 318 publications

(500 citation statements)

References 175 publications

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“…In contrast, Belinfante's spin momentum p S is a rather enigmatic quantity [26][27][28][29][30][31][32][33] . On the one hand, the spin momentum provides the physical origin of the spin AM of quantum particles.…”

Section: Resultsmentioning

confidence: 99%

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Extraordinary momentum and spin in evanescent waves

2014

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Momentum and spin represent fundamental dynamic properties of quantum particles and fields. In particular, propagating optical waves (photons) carry momentum and longitudinal spin determined by the wave vector and circular polarization, respectively. Here we show that exactly the opposite can be the case for evanescent optical waves. A single evanescent wave possesses a spin component, which is independent of the polarization and is orthogonal to the wave vector. Furthermore, such a wave carries a momentum component, which is determined by the circular polarization and is also orthogonal to the wave vector. We show that these extraordinary properties reveal a fundamental Belinfante's spin momentum, known in field theory and unobservable in propagating fields. We demonstrate that the transverse momentum and spin push and twist a probe Mie particle in an evanescent field. This allows the observation of 'impossible' properties of light and of a fundamental field-theory quantity, which was previously considered as 'virtual'.

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Section: Resultsmentioning

confidence: 99%

“…In this case, what generates the spin AM density s / s z? This known paradox 26,34,35 is resolved by representing the zero transverse momentum as an array of infinitely small loops of circulating spin momentum in the (x,y) plane 26,[30][31][32] , see Fig. 1b.…”

Section: Resultsmentioning

confidence: 99%

Extraordinary momentum and spin in evanescent waves

2014

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“…It is a part of a general class of studies in which particles are observed to undergo circulation while immersed in a static force field with nonzero curl (25,49). In addition, Angelsky et al observed orbital angular momentum transfer in circularly polarized Gaussian beams as a manifestation of the macroscopic "spin energy flow," thus confirming the theory of inhomogeneously polarized paraxial beams (34,50).…”

Section: The Evanescent Wave Technique As a Methods Of Angular Momentumentioning

confidence: 91%

Elliptical orbits of microspheres in an evanescent field

Liu

Kheifets

Ginis

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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We examine the motion of periodically driven and optically tweezed microspheres in fluid and find a rich variety of dynamic regimes. We demonstrate, in experiment and in theory, that mean particle motion in 2D is rarely parallel to the direction of the applied force and can even exhibit elliptical orbits with nonzero orbital angular momentum. The behavior is unique in that it depends neither on the nature of the microparticles nor that of the excitation; rather, angular momentum is introduced by the particle's interaction with the anisotropic fluid and optical trap environment. Overall, we find this motion to be highly tunable and predictable.optical forces | colloids | microparticles | evanescent field | elliptical motion R ecently, much work has gone into the investigation of optical forces on micro-and nanoparticles near surfaces, primarily in the context of an electric field localized by a microstructured surface (1-5).Surface-based geometries have raised theoretical excitement due to, for instance, their ability to significantly enhance optical forces (6-8) as well as the emergence of lateral forces due to the extraordinary momentum and spin in evanescent waves (9)(10)(11)(12). From an applied point of view, such geometries can enable miniaturization and parallelization of efficient optical traps enabling integration into optofluidic devices (13,14). Moreover, light-controlled microspheres near surfaces have found applications as force transducers (15-18) and pumps and switches (19,20), and in general, their collective manipulation is an advancing field (21-23).However, in the case where a microparticle is within several diameters of a surface, optical and hydrodynamic surface effects cannot be neglected. Effects arising from optical coupling or reflections can complicate trapping and detection schemes (24), and hydrodynamic interactions can cause the motion of a microparticle to become highly nontrivial (25). Despite this, little quantitative study has been done on the dynamics of optically driven particles near a surface. In studies introducing new schemes to optically manipulate matter, the particle's response function is often ignored (11,12,(26)(27)(28)(29).In this work, we investigate the dynamics of a system with both near field optical forces and surface-induced hydrodynamic effects (see Fig. 1). By driving the particle with an oscillating force from a modulated evanescent field and tracking the particle's motion closely in two dimensions, we map out a range of dynamics that can arise from the interplay of optical and hydrodynamic surface effects. We find that the magnitude and direction of the optical force depends on particle size. We also observe that the trajectory of the particle in general does not follow the direction of the force. Instead, the shape and the orientation of the trajectory vary with modulation frequency and distance of the particle from the surface, a result of the anisotropy in both the hydrodynamic drag and the optical trap spring constant.In particular, we find that under ce...

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“…This is what is required by the general theory [22,23,26], being associated with a divergence-less nature of the quantities given by Eqs. (20) and (33).…”

Section: Application To Surface Plasmon-polaritonmentioning

confidence: 93%

Spin and momentum of the light fields in inhomogeneous dispersive media with application to surface plasmon-polariton waves

Bekshaev

Bliokh²

2018

Ukr. J. Phys. Opt.

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Abstract. Following the recent approach [Phys. Rev. Lett. 119, 073901 (2017); New J. Phys., 19, 123014 (2017)], we refine and accomplish a general scheme for the unified description of momentum and angular momentum of the light fields in complex material media. Equations for the canonical (orbital) and spin linear momenta, as well as the orbital and spin angular momenta are presented for a lossless inhomogeneous dispersive medium in a compact form, which is analogous to the Brillouin relationship for the energy. The results are applied to a surface plasmon-polariton field. The microscopic calculations support the phenomenological expectations. Our refined general scheme describes correctly the known unusual properties of the surface plasmon-polariton associated with transverse spin and magnetization momentum. Moreover, it predicts a singular momentum contribution sharply localized at the metal-dielectric interface, which is confirmed by the microscopic analysis. Our results can be useful for the optical systems employing structured light, especially in microoptics, plasmophotonics, optical sorting and micromanipulation.

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Internal flows and energy circulation in light beams

Cited by 318 publications

References 175 publications

Extraordinary momentum and spin in evanescent waves

Extraordinary momentum and spin in evanescent waves

Elliptical orbits of microspheres in an evanescent field

Spin and momentum of the light fields in inhomogeneous dispersive media with application to surface plasmon-polariton waves

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