Fractional optical vortex beam induced rotation of particles

Tao, Shaohua; Yuan, Xiaocong; Lin, Jiao; Peng, Xiang; Niu, Hanben

doi:10.1364/opex.13.007726

Cited by 255 publications

(104 citation statements)

References 17 publications

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“…A particular kind of vortices with fractional topological charge (or order) has received increasing attention due to their special features and potential use in applications ranging from optical manipulation [15,16], quantum entanglement [17], digital spiral imaging [18] among other topics. Typically, such types of vortices [15,16] exhibit a diffractive slit opening while they propagate so the beam's cross-section becomes asymmetric.…”

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confidence: 99%

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Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

Mitri

2016

Journal of Quantitative Spectroscopy and Radiative Transfer

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-An absorptive Rayleigh dielectric sphere in a non-diffracting non-paraxial fractional Bessel vortex beam experiences a spin torque. The axial and transverse radiation spin torque components are evaluated in the dipole approximation using the radiative correction of the electric field. Particular emphasis is given on the polarization as well as changing the topological charge  and the beam's half-cone angle. When  is zero, the axial spin torque component vanishes. However, when  becomes a real positive number, the vortex beam induces left-handed (negative) axial spin torque as the sphere shifts off-axially from the center of the beam. The results show that a non-diffracting non-paraxial fractional Bessel vortex beam is capable to induce a spin reversal of an absorptive Rayleigh sphere placed arbitrarily in its path. Potential applications are yet to be explored in particle manipulation, rotation in optical tweezers, optical tractor beams, the design of optically-engineered metamaterials to name a few areas. Keywords: Negative spin torque, dielectric sphere, dipole approximation.The optical radiation torque [1] which arises from the transfer of angular momentum of light to a (lossy) dielectric sphere has received significant attention in optical levitation [2-4] and particle rotation applications in atomic physics [5,6], cell biology [7] and other areas [8,9]. In common optical laser beams, and under some conditions related to the particle absorptive properties, a spin torque causing the particle to rotate around its center of mass arises, in addition to an orbital component causing the particle to rotate around the beam's axis of wave propagation [1]. Note that the orbital torque component exerted on the sphere vanishes at the center of the beam. Moreover, the sphere should be absorptive in order to experience a spin torque [1]. Various standard types of laser beams have been suggested and investigated for this purpose [10,11]. Examples of beams also include optical vortices of Gaussian-like [12,13] and nondiffracting beams [14].A particular kind of vortices with fractional topological charge (or order) has received increasing attention due to their special In contrast, another class for factional vortex beams (which can be realized experimentally using blazed-phase hologram encoded in a programmable liquid crystal display illuminated with a He-Ne laser [19]) and displays limited-diffracting features during propagation exists [19,20]. The physically-realizable apodized beam carrying finite energy preserves the nondiffracting propagation property. It is also known as a high-order Bessel vortex beam of fractional type  (HOBVB-F) [21][22][23]. A HOBVB-F with fractional order  connects standard nondiffracting Bessel (vortex) beams (Fig. 1) of successive integer order in a smooth transition. It also generates individual vortices in the (lateral) plane perpendicular to the axis of wave propagation corresponding to a cross-section of the incident nondiffracting beam [19]. This specific feature provides ...

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“…Typically, such types of vortices [15,16] exhibit a diffractive slit opening while they propagate so the beam's cross-section becomes asymmetric.…”

mentioning

confidence: 99%

Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

Mitri

2016

Journal of Quantitative Spectroscopy and Radiative Transfer

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“…[2][3][4] A plane wave can be converted into a helical mode with an azimuthal phase of exp(imθ), where m is the topological charge and θ is the azimuthal angle. Optical beams with helical phase are known as optical vortices 5 which possess orbital angular momentum (OAM).…”

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confidence: 99%

Annular beam with segmented phase gradients

Cheng

Tao

2016

AIP Advances

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An annular beam with a single uniform-intensity ring and multiple segments of phase gradients is proposed in this paper. Different from the conventional superposed vortices, such as the modulated optical vortices and the collinear superposition of multiple orbital angular momentum modes, the designed annular beam has a doughnut intensity distribution whose radius is independent of the phase distribution of the beam in the imaging plane. The phase distribution along the circumference of the doughnut beam can be segmented with different phase gradients. Similar to a vortex beam, the annular beam can also exert torques and rotate a trapped particle owing to the orbital angular momentum of the beam. As the beam possesses different phase gradients, the rotation velocity of the trapped particle can be varied along the circumference. The simulation and experimental results show that an annular beam with three segments of different phase gradients can rotate particles with controlled velocities. The beam has potential applications in optical trapping and optical information processing.

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“…For example, if one attempts to alter OAM by coherent superposition of two LG modes with mutually opposite azimuthal index, then the intensity will no longer possess the characteristic azimuthally independent annular shape of the individual modes. 9,10 Similarly, trying to alter the intensity distribution of a BB by superimposing several coherent Bessel modes of different order or propagation constant will result in a field that cannot propagate in a "diffraction-free" manner.…”

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“…17 "Classic" vortex beams, with integer values of l, therefore produce quantized values for OAM transfer and lead to smooth rotation around the beam annulus. Previously reported experiments to impart noninteger amounts of OAM to trapped particles using fractional vortex beams 9 or interference of two classic vortices 10 produce azimuthal intensity variations that inhibit smooth particle motion unless the particles are of sufficiently large diameter to bridge any azimuthal gaps in intensity. In contrast, the interference-free superposition we present can be used to produce smoothly varying OAM transfer without the limitation of such intensity minima.…”

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Interference-free superposition of nonzero order light modes: Functionalized optical landscapes

Čižmár

Dalgarno

Ashok

et al. 2011

Applied Physics Letters

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In this paper, we utilize the incoherent superposition of nonzero order light modes. We show that this approach brings an additional degree of freedom to the generation of optical fields and notably the formation of superpositions that are otherwise unattainable through the use of refractive or diffractive optical elements and coherent or incoherent light sources. We employ this technique in two exemplary cases: first to create a field with tunable orbital angular momentum whose spatial intensity distribution remains unchanged and second to form an unusual type of “nondiffracting” light beam.

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Fractional optical vortex beam induced rotation of particles

Cited by 255 publications

References 17 publications

Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

Annular beam with segmented phase gradients

Interference-free superposition of nonzero order light modes: Functionalized optical landscapes

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