45 research outputs found
Photophoretic manipulation of absorbing aerosol particles with vortex beams: theory versus experiment
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
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
Focusing and correlation properties of white-light optical vortices
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
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
Undetectable interception of network traffic on LAN technologies
Nowadays it's impossible to imagine a company that doesn't use Internet and Intranet (LAN) to move confidential data around. Safety measures can be both: hardware and software information security solutions. The cases of development and usage of custom, their own systems of automation of information processing (electronic document management, accounting, backup, etc.) are not rare, any more. In that case information security department assess the sustainability of computer networks or systems to attacks by the software, forgetting the data that being transmitted over the Ethernet (except, perhaps, Wi-Fi channel, but they only checking for cryptographically strong algorithm and a password). In current article, we propose a concept of the device for not-detectable interception (and modification) of the transmitted information through the Ethernet network
Optical guiding of absorbing nanoclusters in air
We suggest a novel approach in all-optical trapping employing
a photophoretic force for manipulation of absorbing particles in open air.
We demonstrate experimentally the robust three-dimensional guiding, over
the distances of a few millimeters, of agglomerates of carbon nanoparticles
with the size spanned from 100 nm to 10μm, as well as their acceleration
up to velocities of 1 cm/sec. We achieve stable positioning and guiding of
particles as well as simultaneous trapping of a large number of particles in a
dual beam optical trap created by two counter-propagating and co-rotating
optical vortex beams
Observation of polychromatic vortex solitons
We demonstrate experimentally the formation of polychromatic single- and double-charge optical vortex solitons
by employing a lithium niobate crystal as a nonlinear medium with defocusing nonlinearity. We study
the wavelength dependence of the vortex core localization and observe self-trapping of polychromatic vortices
with a bandwidth spanning over more than 70 nm for single-charge and 180 nm for double-charge vortex
solitons.This work was supported by the Australian Research
Council through Discovery and Linkage International
projects and by the National Science Foundation
(NSF)-Bulgaria, project WUF-02/05
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
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