92 research outputs found

    Photophoretic manipulation of absorbing aerosol particles with vortex beams: theory versus experiment

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    We develop a theoretical approach for describing the optical trapping and manipulation of carbon nanoclusters in air with a dual-vortex optical trap, as realized recently in experiment [V. Shvedov et al., Opt. Express 17, 5743 (2009)]. We calculate both longitudinal and transverse photophoretic forces acting on a spherical absorbing particle, and then compare our theoretical predictions with the experimental data

    Materials processing with tightly focused femtosecond vortex laser beams

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    This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than 100 nm uniform groove thickness.Comment: 8 pages, 3 figures, 10 references; submitted to Appl. Phys. Lett. on May 31, 201

    Momentum transfer in a standing optical vortex

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    A field superposition of singular beams incident on, and then reflected from a mirror has been investigated. It was demonstrated that the standing optical wave, which contains a vortex, possesses an orbital angle momentum where the energy flux circulates only in the azimuth direction of the beam. We show in this paper that the standing light wave containing the optical vortex transfers angular momentum to a substance located in the field of the vortex without moving the substance in the azimuth or radial directions. This property of the standing vortex present an opportunity to form the three-dimensional optical traps, gasdynamic and hydrodynamic vortices, in a localised volume by a direct transfer of the orbital angular momentum from the optical vortex.Comment: English has been corrected; a second address entered; Eq.(13) and (14) corrected. 11 pages, including 1 figur

    Focusing and correlation properties of white-light optical vortices

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    We generate double-charge white-light optical vortices by sending a circularly polarized partially incoherent light through an uniaxial crystal. We show that the generated polichromatic vortices are structurally stable, and their correlation properties can be altered by the beam focusing, resulting in changes of the vortex core visibility.Comment: 6 pages, 4 figure

    Counterpropagating nematicons in bias-free liquid crystals

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    We experimentally investigate the interaction of two counterpropagating spatial optical solitons (nematicons) in bias-free nematic liquid crystals. We demonstrate the existence of vector solitons composed of two nematicons propagating in opposite directions and analyze their stability versus relative distance and input power.We observe the dynamic instability of two counterpropagating nematicons in the form of time-dependent splitting and spatial entanglement

    Nonlinear propagation and quasi self-confinement of light in plasmonic resonant media

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    We study nonlinear propagation of light in colloidal suspension of metallic nanoparticles, in the regime of particles surface plasmon resonance. We show that the propagation exhibits features typical for purely defocusing media and the observed spatial confinement is not a real self-trapping, as for solitons, but rather than is caused by the phase modulation of the beam via nonlocal defocusing nonlinearity. We also show that the light-induced refractive index change in the suspension leads to stabilization of structured light beams. In particular, we demonstrate a stable nonlinear propagation of bright ring beams with complex states of polarization, including practically important radial and azimuthal states.Qatar National Research Fund (grant # NPRP 9-020-1-006). Y.S-R. acknowledges support from CONACyT and Australian and Mexican Academies of Science for Ph.D. internship grant
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