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ABSTRACT: The redistribution of light between micro- or nanoobjects placed in counter-propagating laser fields leads to their steady-state
spatial configurations. Under appropriate conditions, the objects are spatially separated and form optically bound matter.
This is a very exciting phenomenon that is still not fully understood. In this article we present a new theoretical model
of how to study this phenomenon, which is based on a coupled dipole method particularly amenable to nanoparticle optical binding.
Predictions of this model are compared with experimental data and other theoretical models with satisfactory results.
Applied Physics B 04/2012; 84(1):149-156. · 2.19 Impact Factor
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ABSTRACT: It is generally accepted that the interaction between particles mediated by the scattered light (called optical binding) is very weak. Therefore, the optical binding is usually neglected in a multi-particle trapping in distinct optical traps. Here we show that even the presence of only two dielectric particles confined in the standing wave leads to their significantly different behavior comparing to the case of a single trapped particle. We obtained persuading coincidence between our experimental records and the results of the deterministic and stochastic theoretical simulations based on the coupled dipole method.
Optics Express 09/2011; 19(20):19613-26. · 3.59 Impact Factor
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ABSTRACT: We present an experimental and theoretical study of long distance optical binding effects acting upon micro-particles placed in a standing wave optical field. In particular we present for the first time quantitatively the binding forces between individual particles for varying inter-particle separations, polarizations and incident angles of the binding beam. Our quantitative experimental data and numerical simulations show that these effects are essentially enhanced due to the presence of a reflective surface in a sample chamber. They also reveal conditions to form stable optically bound clusters of two and three particles in this geometry. We also show that the inter-particle separation in the formed clusters can be controlled by altering the angle of the beam incident upon the sample plane. This demonstrates new perspectives for the generation and control of optically bound soft matter and may be useful to understand various inter-particle effects in the presence of reflective surfaces.
Optics Express 11/2010; 18(24):25389-402. · 3.59 Impact Factor
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ABSTRACT: Standing wave optical trapping offers many useful advantages in comparison to single beam trapping, especially for submicrometer size particles. It provides axial force stronger by several orders of magnitude, much higher axial trap stiffness, and spatial confinement of particles with higher refractive index. Mainly spherical particles are nowadays considered theoretically and trapped experimentally. In this paper we consider prolate objects of cylindrical symmetry with radius periodically modulated along the axial direction and we present a theoretical study of optimized objects shapes resulting in up to tenfold enhancement of the axial optical force in comparison with the original unmodulated object shape. We obtain analytical formulas for the axial optical force acting on low refractive index objects where the light scattering by the object is negligible. Numerical results based on the coupled dipole method are presented for objects with higher refractive indices and they support the previous simplified analytical conclusions.
Optics Express 07/2009; 17(13):10472-88. · 3.59 Impact Factor
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ABSTRACT: We employed a coupled dipole method (CDM) to study theoretically the interaction among several spherical particles placed into two counter-propagating mutually incoherent Bessel beams. This interaction is mediated by the light scattering among the particles. It has already been demonstrated that, if the intensity of the incident beam is sufficiently high, the scattered light is strong enough to self-arrange the objects in the space. Namely, the counter-propagating and incoherent Bessel beams are extremely useful to be employed because the interaction among the particles via the scattered light is not superimposed by other optical forces coming from the radiation pressure of each beam and axial gradients of the beam intensities. Therefore so-called optical binding between the particles is enhanced and leads to several stable configurations of the particles. We studied these stable configurations using the CDM for various properties of the beams and particles and we also compared these theoretical results with the experimental observations.
Journal of Optics A Pure and Applied Optics 01/2009; 11(3):034009. · 1.92 Impact Factor
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ABSTRACT: We create extended longitudinally optically bound chains of microparticles with the use of counterpropagating "nondiffracting" light fields, the so-called Bessel beams. The beam homogeneity and extended propagation range allow the creation of 200 microm long chains of organized microparticles. We observe short-range multistability within a single chain and long-range multistability between several distinct chains. Our observations are supported by theoretical results of the coupled dipole method.
Physical Review Letters 11/2008; 101(14):143601. · 7.37 Impact Factor
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ABSTRACT: We present a modified analytical model describing optical forces acting on two spherical nanoparticles arranged longitudinally in two counter-propagating beams. These particles interact with light as Rayleigh particles and are approximated by dipoles. We focus on the key phenomena of longitudinal binding between these two objects and therefore we applied the general analytical solution to two counter-propagating beams with zero intensity gradients along their propagation (Bessel beams). Numerical results coincide with a numerical model based on the coupled dipoles method.
Journal of Optics A Pure and Applied Optics 07/2007; 9(8):S215. · 1.92 Impact Factor
