Optical vortices near sub-wavelength structures

Schouten, Hugo F.; Visser, Taco D.; Lenstra, D.

doi:10.1088/1464-4266/6/5/031

Cited by 41 publications

(49 citation statements)

References 13 publications

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“…The energy flow pattern, which to some extent and with some limitations is equivalent with the electromagnetic momentum pattern [8], is expressed by the time-averaged Poynting vector distribution and appear as a natural instrument for characterizing light fields with arbitrary structure [5,6]. It is especially suitable in the near-field optics and for description of evanescently decaying waves [9][10][11][12], e.g., in plasmonic devices; some novel applications related to micro-resonators, invisibility cloaking, superlensing and metamaterials, essentially employ the controllable Poynting vector fields [11][12][13]. From a fundamental point of view, optical currents provide a deeper insight into the intimate geometric and dynamic transformation processes that underlie any light field evolution in the course of free or controlled propagation and diffraction [3,6,14,15].…”

Section: Introductionmentioning

confidence: 99%

Circular motion of particles suspended in a Gaussian beam with circular polarization validates the spin part of the internal energy flow

Angelsky¹,

Bekshaev²,

Maksimyak³

et al. 2012

Opt. Express

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Non-spherical dielectric microparticles were suspended in a water-filled cell and exposed to a coherent Gaussian light beam with controlled state of polarization. When the beam polarization is linear, the particles were trapped at certain off-axial position within the beam cross section. After switching to the right (left) circular polarization, the particles performed spinning motion in agreement with the angular momentum imparted by the field, but they were involved in an orbital rotation around the beam axis as well, which in previous works [Y. Zhao et al, Phys. Rev. Lett. 99, 073901 (2007)] was treated as evidence for the spin-to orbital angular momentum conversion. Since in our realization the moderate focusing of the beam excluded the possibility for such a conversion, we consider the observed particle behavior as a demonstration of the macroscopic "spin energy flow" predicted by the theory of inhomogeneously polarized paraxial beams [A. Bekshaev et al, J. Opt. 13, 053001 (2011)].

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Section: Introductionmentioning

confidence: 99%

Circular motion of particles suspended in a Gaussian beam with circular polarization validates the spin part of the internal energy flow

Angelsky¹,

Bekshaev²,

Maksimyak³

et al. 2012

Opt. Express

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“…A vortex structure in the streamlines of the Poynting vector has been detected for S ommerfeld's edge diff raction with discussion of the eel-like motion of light at the edge dating back to Newtonian times [5]. Recently vortices were found in light diff racted by narrow slits in silver and silicon [6,7]. However, to the best of our knowledge, vortex fi eld structures have never been detected in the vicinity of metal nanoparticles.…”

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confidence: 99%

Optical whirlpool on an absorbing metallic nanoparticle

2005

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EPSRC N a noPh otonic s Portfolio Centre, Sc h ool of Ph ysic s a nd A stronom y, U niv ersity of Sou th a m p ton, SO17 1B J , U nited King dom (Dated: Ju ne 2 0 , 2 0 0 5 )The power-flow lines of light interacting with a metallic nanoparticle, in the proximity of its plasmon resonance, form whirlpool-like nanoscale optical vortices. Two diff erent types of vortex have been detected. The ou tward vortex fi rst penetrates the particle near its centerline then, on exiting the particle, the flow-lines tu rn away from the centerline and enter a spiral trajectory. O u tward vortexes are seen for the wavelengths shorter then the plasmon resonance. For the wavelengths longer that the plasmon resonance the vortex is inward: the power-flow lines pass arou nd the sides of the particle before tu rning towards the centerline and entering the particle to begin their spiral trajectory.The structures of optical fi elds around metallic nanoparticles are of special interest due to their role in nanophotonic and plasmonic devices and metawaveguides [1][2][3]. Here for the fi st time, we report that light interacting with an absorbing metallic nanoparticle follows curly trajectories with curvatures on the subwavelength scale, creating whirlpool-like nanoscale optical vortices. These "energy sink" vortices with spiral energy flow line trajectories are seen in the proximity of the nanoparticle's plasmon resonance.O ptical vortices have been identifi ed as features in scalar wavefront dislocations of monochromatic light fi elds and modal lines corresponding to nonmonochromatic light as well as in singularities in the maps representing vectorial properties of light [4]. It is now recogniz ed that singularities are often features of fi elds near sub-wavelength structures. A vortex structure in the streamlines of the Poynting vector has been detected for S ommerfeld's edge diff raction with discussion of the eel-like motion of light at the edge dating back to Newtonian times [5]. Recently vortices were found in light diff racted by narrow slits in silver and silicon [6,7]. However, to the best of our knowledge, vortex fi eld structures have never been detected in the vicinity of metal nanoparticles.We studied the interaction of light with homogeneous isotropic spherical nanoparticles using Mie theory [8] -an exact analytical wave theory giving time-harmonic electromagnetic fi elds E and H at freq uency ω that satisfy the wave eq uationswhere k 2 = ω 2 εµ. S olutions to these eq uations are presented in the form of a series of spherical B essel Functions inside the particle and spherical Hankel functions outside it. The nanoparticle is assumed to have a dielectric coeffi cient ε and permittivity µ. Mie theory gives exact solutions of the vector wave eq uation for the internal and scattered fi elds of the particle and has generated a massive body of literature in which fi eld patterns for angle-dependant scattering, modes of excitation, and integral characteristics such as absorption and scattering cross-section have been calculated [9,1...

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“…These works have delivered insights regarding the scattering/absorption mechanisms, especially in the vicinity of small resonant spheres. Conceptually, the electromagnetic energy flow resembles the hydrodynamic flow [8,9], demonstrating how the structure perturbs its near field distribution in a scattering problem setup. From a mathematical point of view, the perturbed near field distribution may exhibit several critical points, such as centers and saddles, whose behavior is affected by the scatterers' geometry [8,9].…”

Section: Introductionmentioning

confidence: 97%