Macroscopic direct observation of optical spin-dependent lateral forces and left-handed torques

Magallanes, Hernando; Brasselet, Étienne

doi:10.1038/s41566-018-0200-x

Cited by 62 publications

(47 citation statements)

References 47 publications

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“…Reverse orbiting of non-spherical particles confined on a 2D interface was observed by employing Laguerre-Gaussian vortex beams [13]. Negative OT was demonstrated for a macroscopic inhomogenous and anisotropic disk by measuring the rotationally Doppler-shifted reflected light [14,15] and more recently by the direct observation of the disk rotation [16].…”

Section: Introductionmentioning

confidence: 99%

Negative optical torque on a microsphere in optical tweezers

Diniz¹,

Dutra²,

Pires³

et al. 2019

Opt. Express

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We show that the optical force field in optical tweezers with elliptically polarized beams has the opposite handedness for a wide range of particle sizes and for the most common configurations. Our method is based on the direct observation of the particle equilibrium position under the effect of a transverse Stokes drag force, and its rotation around the optical axis by the mechanical effect of the optical torque. We find overall agreement with theory, with no fitting, provided that astigmatism, which is characterized separately, is included in the theoretical description. Our work opens the way for characterization of the trapping parameters, such as the microsphere complex refractive index and the astigmatism of the optical system, from measurements of the microsphere rotation angle.

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Section: Introductionmentioning

confidence: 99%

Negative optical torque on a microsphere in optical tweezers

Diniz¹,

Dutra²,

Pires³

et al. 2019

Opt. Express

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show abstract

“…Negative optical torque, which causes objects to rotate opposite to the direction of the incident beam’s angular momentum, has been theoretically postulated 13 – 15 yet with limited experimental realization 8 , 16 . Stable negative optical torque has only been demonstrated via coupled spin–orbit light scattering in optically inhomogeneous and anisotropic transparent media, such as birefringent and structured glass disks 8 or polymer layers 16 . Negative optical torque events were also observed in electrodynamically coupled NP dimers 17 , but only when the dimers were in a transient (unstable) state.…”

Section: Introductionmentioning

confidence: 99%

Crossover from positive to negative optical torque in mesoscale optical matter

et al. 2018

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The photons in circularly polarized light can transfer their quantized spin angular momentum to micro- and nanostructures via absorption and scattering. This normally exerts positive torque on the objects wher the sign (i.e., handedness or angular direction) follows that of the spin angular momentum. Here we show that the sign of the optical torque can be negative in mesoscopic optical matter arrays of metal nanoparticles (NPs) assembled in circularly polarized optical traps. Crossover from positive to negative optical torque, which occurs for arrays with different number, separation and configuration of the constituent particles, is shown to result from many-body interactions as clarified by electrodynamics simulations. Our results establish that both positive and negative optical torque can be readily realized and controlled in optical matter arrays. This property and reconfigurability of the arrays makes possible programmable materials for optomechanical, microrheological and biological applications.

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“…In this context, optical micromanipulation includes not only trapping by a noncontact force but also single-cell manipulation, alignment, and sorting of mostly micron-sized dielectric particles [5][6][7]. Furthermore, digital holographic optical tweezers can be used to generate individual traps to transfer orbital or spin angular momentum and enable the particle circulation and spinning [8][9][10]. To obtain a stable trapping potential, the gradient force of a tightly focused beam must balance the scattering force exerted on the particle.…”

Section: Introductionmentioning

confidence: 99%

All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers

et al. 2020

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Dynamic control of compact chip-scale contactless manipulation of particles for bioscience applications remains a challenging endeavor, which is restrained by the balance between trapping efficiency and scalable apparatus. Metasurfaces offer the implementation of feasible optical tweezers on a planar platform for shaping the exerted optical force by a microscale-integrated device. Here, we design and experimentally demonstrate a highly efficient silicon-based metalens for two-dimensional optical trapping in the near-infrared. Our metalens concept is based on the Pancharatnam-Berry phase, which enables the device for polarization-sensitive particle manipulation. Our optical trapping setup is capable of adjusting the position of both the metasurface lens and the particle chamber freely in three directions, which offers great freedom for optical trap adjustment and alignment. Two-dimensional (2D) particle manipulation is done with a relatively low numerical aperture metalens (NAML = 0.6). We experimentally demonstrate both 2D polarization sensitive drag and drop manipulation of polystyrene particles suspended in water and transfer of angular orbital momentum to these particles with a single tailored beam. Our work may open new possibilities for lab-on-a-chip optical trapping for bioscience applications and micro to nanoscale optical tweezers.

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Macroscopic direct observation of optical spin-dependent lateral forces and left-handed torques

Cited by 62 publications

References 47 publications

Negative optical torque on a microsphere in optical tweezers

Negative optical torque on a microsphere in optical tweezers

Crossover from positive to negative optical torque in mesoscale optical matter

All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers

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