149 research outputs found
Momentum transfer in a standing optical vortex
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
Self-induced mode transformation in nonlocal nonlinear media
We report on the first experimental observation of self-induced optical mode transformations in nonlocal nonlinear media. We show that the quadrupole Hermite-Gaussian mode experiences complex nonlinear dynamics in a nematic liquid crystal, including powe
Rotational spin Hall effect in a uniaxial crystal
We have considered the propagation process of the phase-matched array of
singular beams through a uniaxial crystal. We have revealed that local beams in
the array are rotated when propagating. However the right and left rotations
are unequal. There are at least two processes responsible for the array
rotation: the interference of local beams and the spatial depolarization. The
interference takes place in the vortex birth and annihilation events forming
the symmetrical part of the rotation. The depolarization process contributes to
the asymmetry of the rotation that is called the rotational spin Hall effect.
It can be brought to light due to the difference between the envelopes of the
dependences of the angular displacement on the inclination angle of the local
beams or the crystal length reaching the value some angular degree. The
direction of the additional array rotation is exclusively defined by the
handedness of the circular polarization in the initial beam array.Comment: 26 pages, 11 figure
Efficient Beam Converter for the Generation of Femtosecond Vortices
We describe an optical beam converter for an efficient transformation of
Gaussian femtosecond laser beams to single- or double-charge vortex beams
showing no spatial or topological charge dispersion. The device achieves a
conversion efficiency of 75% for single- and 50% for double-charge vortex beams
and can operate with high energy broad bandwidth pulses. We also show that the
topological charge of a femtosecond vortex beam can be determined by analyzing
its intensity distribution in the focal area of a cylindrical lens.Comment: 9 pages, 4 figures, submitted to Optics Letters 10 March 201
Counterpropagating nematicons in bias-free liquid crystals
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
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
Generation of optical bottle beams by incoherent white-light vortices
We generate experimentally optical bottle beams from incoherent
double-charge white-light vortices, and show that their parameters can
be efficiently controlled by varying the beam focusing conditions
Selective trapping of multiple particles by volume speckle field
We suggest a new approach for selective trapping of light
absorbing particles in gases by multiple optical bottle-beam-like traps
created by volume speckle field. We demonstrate stable simultaneous
confinement of a few thousand micro-particles in air with a single lowpower
laser beam. The size distribution of trapped particles exhibits a
narrow peak near the average size of an optical speckle. Thus, the speckleformed
traps act as a sieve with the holes selecting particles of a similar size
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