Mechanical equivalence of spin and orbital angular momentum of light: an optical spanner

Simpson, N. B.; Dholakia, Kishan; Allen, L. J.; Padgett, Miles J.

doi:10.1364/ol.22.000052

Cited by 1,011 publications

(423 citation statements)

References 15 publications

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“…The transfer of spin and orbital AM to microscopic particles [7,8,9,10] and to liquid crystals [11,12] has been observed.…”

Section: Introductionmentioning

confidence: 98%

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

2009

Phys. Rev. A

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It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that is associated with the former part is spin, and the angular momentum that is associated with the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin and orbital angular momentum defined this way are used to investigate the angular momentum of nonparaxial beams that are described in a recently published paper [Phys. Rev. A 78, 063831 (2008)]. It is found that the orbital angular momentum depends, apart from an l-dependent term, on two global quantities, the polarization represented by a generalized Jones vector and a new characteristic represented by a unit vector I, though the spin depends only on the polarization. The polarization dependence of orbital angular momentum through the impact of I is obtained and discussed. Some applications of the result obtained here are also made. The fact that the spin originates from the momentum density that has no contribution to the net momentum is used to show that there does not exist the paradox on the spin of circularly polarized plane wave. The polarization dependence of both spin and orbital angular momentum is shown to be the origin of conversion from the spin of a paraxial Laguerre-Gaussian beam into the orbital angular momentum of the focused beam through a high numerical aperture.

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“…The transfer of spin and orbital AM to microscopic particles [7,8,9,10] and to liquid crystals [11,12] has been observed.…”

Section: Introductionmentioning

confidence: 98%

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

2009

Phys. Rev. A

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“…Recent work by Berry and Berg [1999] has involved using electrorotation to drive the molecular motor of E. coli bacteria backwards at speeds of up to 2,000Hz. Since the electrodes involved in that work were applying 10V across inter-electrode gaps of 50 considerably higher fields (and hence induced torques) could be applied with electrodes with interequivalent of laser spanners [Simpson et al 1997], then there exists a number of applications within current nanotechnological thought to which electrorotation might be applied. There are a number of advantages that favour electrorotation over its optical equivalent; most notable advantages are that electrorotation-induced torque is easily controlled by altering the frequency of the electric field, and that there does not need to be a direct optical path to the part to be manipulated.…”

Section: Electrorotationmentioning

confidence: 99%

AC electrokinetics: applications for nanotechnology

Hughes¹

2000

Nanotechnology

266

177

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The phenomena of dielectrophoresis and electrorotation, collectively referred to as AC electrokinetics, have been used for many years to study, manipulate and separate particles on the nanotechnology, that is the precise manipulation of particles on the nanometre scale. In this paper we present the principles of AC electrokinetics for particle manipulation, review the current state of AC Electrokinetic techniques for the manipulation of particles on the nanometre scale, and consider how these principles may be applied to nanotechnology.3

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“…Such light is referred as an optical vortex [1][2][3][4]. Optical vortices have been widely investigated for applications such as optical trapping and guiding [5][6][7], as well as superresolution microscopy [8,9]. Circularly polarized light has a helical electric field and a spin angular momentum, S@, associated with its circular polarization.…”

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confidence: 99%

Transfer of Light Helicity to Nanostructures

et al. 2013

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We discovered that chiral nanoneedles fabricated by vortex laser ablation can be used to visualize the helicity of an optical vortex. The orbital angular momentum of light determines the chirality of the nanoneedles, since it is transferred from the optical vortex to the metal. Only the spin angular momentum of the optical vortex can reinforce the helical structure of the created chiral nanoneedles. We also found that optical vortices with the same total angular momentum (defined as the sum of the orbital and spin angular momenta) are degenerate, and they generate nanoneedles with the same chirality and spiral frequency. DOI: 10.1103/PhysRevLett.110.143603 PACS numbers: 42.50.Tx, 42.50.Wk, 79.20.Ds, 79.20.Eb Light that has a helical wave front due to an azimuthal phase shift, expðiL Þ (where L is an integer known as the topological charge), carries orbital angular momentum, L@. Such light is referred as an optical vortex [1][2][3][4]. Optical vortices have been widely investigated for applications such as optical trapping and guiding [5][6][7], as well as superresolution microscopy [8,9]. Circularly polarized light has a helical electric field and a spin angular momentum, S@, associated with its circular polarization. Optical vortices with circular polarization exhibit both wave front and polarization helicities, and a total angular momentum, J@ [10-12], which is defined as the sum of the orbital and spin angular momenta. This angular momentum is evidenced by the orbital and spinning motions of trapped particles in optical tweezers.To date, several researchers have intensely studied the interaction of structured light, such as radially polarized beams, with plasmonic or metallic structures [13][14][15]. However, these previous studies mostly focused on optical properties, such as mode selection, plasmon focusing, etc., of plasmonic or metallic structures, including photonic crystals as well as plasmonic waveguides, prepared by conventional integrated photonic circuit techniques based on lithography and chemical etching. There are few reports on the use of structured light itself to form chiral structures on the nanoscale. Recently, we discovered that the helicity of a circularly polarized optical vortex can be directly transferred to an irradiated metal sample, resulting in the formation of chiral nanoneedles [16][17][18]. This is the first demonstration, to the best of our knowledge, of nanostructures created by structured light with angular momenta, and it clearly represents a new scientific phenomenon.We have also investigated control of the chirality of formed nanoneedles by changing the sign of the optical vortex helicity. Chiral nanostructures have the potential to form many new material structures [19], including planar chiral metamaterials [20,21] and plasmonic nanostructures [22,23]. They can also be used to selectively identify the chirality of chemical composites in nanoscale imaging systems, such as atomic force and scanning tunnel microscopes [24][25][26][27].However, it is currently unclear whe...

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Mechanical equivalence of spin and orbital angular momentum of light: an optical spanner

Cited by 1,011 publications

References 15 publications

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

Spin and orbital angular momentum of a class of nonparaxial light beams having a globally defined polarization

AC electrokinetics: applications for nanotechnology

Transfer of Light Helicity to Nanostructures

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