2,549 research outputs found
Optical Levitation of a Droplet under Linear Increase of Gravitational Acceleration
Optical levitation of a liquid droplet in gas phase was investigated under
timedependent change of the gravitational acceleration with specific flight
pattern of an airplane. Through multiple trials under linear increase of
effective gravitational acceleration, we performed the experiment of ptical
trapping of a droplet from 0.3g_0 to 0.9g_0, where g_0 = 9.8 m/s^2. During such
change of the effective gravitational acceleration, the trapping position on a
droplet with the radius of 14 μm was found to be lowered by ca. 100
μm. The essential feature of the change of the trapping position is
reproduced by a theoretical calculation under the framework of ray optics. As
far as we know, the present study is the first report on optical levitation
under time-dependent gravitational change
Microrheology with Optical Tweezers of gel-like materials 'is not an option'!
Optical tweezers have been successfully adopted as exceptionally sensitive
transducers for microrheology studies of complex 'fluids'. Despite the general
trend, a similar approach cannot be adopted for microrheology studies of
'gel-like' materials, e.g. living cells.Comment: 3 pages, 1 figur
Optically bound microscopic particles in one dimension
Counter-propagating light fields have the ability to create self-organized
one-dimensional optically bound arrays of microscopic particles, where the
light fields adapt to the particle locations and vice versa. We develop a
theoretical model to describe this situation and show good agreement with
recent experimental data (Phys. Rev. Lett. 89, 128301 (2002)) for two and three
particles, if the scattering force is assumed to dominate the axial trapping of
the particles. The extension of these ideas to two and three dimensional
optically bound states is also discussed.Comment: 12 pages, incl. 5 figures, accepted by Phys. Rev.
Toward the Stable Optical Trapping of a Droplet with Counter Laser Beams under Microgravity
To identify the optimum conditions for the optical trapping of a droplet
under microgravity, we theoretically analyzed the efficiency of trapping with
counter laser beams. We found that the distance between the two foci is an
important parameter for obtaining stable trapping conditions. We also performed
an optical trapping experiment with counter laser beams under microgravity. The
experimental results correspond well to the theoretical prediction
Fundamentals of negative refractive index optical trapping: forces and radiation pressures exerted by focused Gaussian beams using the generalized Lorenz-Mie theory
Based on the generalized Lorenz-Mie theory (GLMT), this paper reveals, for the first time in the literature, the principal characteristics of the optical forces and radiation pressure cross-sections exerted on homogeneous, linear, isotropic and spherical hypothetical negative refractive index (NRI) particles under the influence of focused Gaussian beams in the Mie regime. Starting with ray optics considerations, the analysis is then extended through calculating the Mie coefficients and the beam-shape coefficients for incident focused Gaussian beams. Results reveal new and interesting trapping properties which are not observed for commonly positive refractive index particles and, in this way, new potential applications in biomedical optics can be devised
Single-particle motional oscillator powered by laser
An ion, atom, molecule or macro-particle in a trap can exhibit large motional
oscillations due to the Doppler-affected radiation pressure by a laser,
blue-detuned from an absorption line of a particle. This oscillator can be
nearly thresholdless, but under certain conditions it may exhibit huge
hysteretic excitation. Feasible applications include a "Foucault pendulum" in a
trap, a rotation sensor, single atom spectroscopy, isotope separation, etc.Comment: 9 pages, 1 fig; v2: the latest revision for Optics Expres
Effect of Coherence on Radiation Forces acting on a Rayleigh Dielectric Sphere
The radiation forces on a Rayleigh dielectric sphere induced by a partially
coherent light beam are greatly affected by the coherence of the light beam.
The magnitude of the radiation forces on a dielectric sphere near the focus
point greatly decreases as the coherence decreases. For the light beam with
good coherence, the radiation force may be used to trap a particle; and for the
light beam with intermediate coherence, the radiation force may be used to
guide and accelerate a particle.Comment: 12 pages, 3 figure
Measuring micro-interactions between coagulating red blood cells using optical tweezers
Agents that alter the dynamics of hemostasis form an important part in management of conditions such as atherosclerosis, cerebrovascular disease, and bleeding diatheses. In this study, we explored the effects of heparin and tranexamic acid on the efficiency of blood coagulation. Using optical tweezers, we evaluated the pN-range micro-interaction between coagulating red blood cells (RBCs) by measuring the minimum power required to trap them. By observing the mobility of RBCs and the intensity of cellular interactions, we found that the coagulation process can be separated into three phases. The effects of heparin and tranexamic acid were examined by observing variations in cellular interaction during the coagulation phases. Heparin attenuated the interaction between RBCs and prolonged the first phase whereas the samples containing tranexamic acid bypassed the first two phases and immediately proceeded to the final one
Processing carbon nanotubes with holographic optical tweezers
We report the first demonstration that carbon nanotubes can be trapped and
manipulated by optical tweezers. This observation is surprising because
individual nanotubes are substantially smaller than the wavelength of light,
and thus should not be amenable to optical trapping. Even so, nanotube bundles,
and perhaps even individual nanotubes, can be transported at high speeds,
deposited onto substrates, untangled, and selectively ablated, all with visible
light. The use of holographic optical tweezers, capable of creating hundreds of
independent traps simultaneously, suggests opportunities for highly parallel
nanotube processing with light.Comment: 3 pages, 1 figur
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