Static and dynamic behavior of two optically bound microparticles in a standing wave

Brzobohaty, O.; Karasek, V.; Siler, M.; Trojek, J.; Zemanek, P.
OPTICS EXPRESS 19 (2011) 19613-19626

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. Download

Dynamic size tuning of multidimensional optically bound matter

Brzobohaty, O.; Karasek, V.1; Cizmar, T.; Zemanek, P.

We generate and dynamically control one-, two- and three-dimensional optically bound structures of soft matter in the geometry of counter-propagating incoherent laser beams. We report results for the Bessel, Gaussian, and Laguerre-Gaussian laser modes and particularly focus on the influence of the lateral dimensions of the beam profile on the resulting self-arranged optically bound structures. Employing the transfer of the orbital angular momentum of light in the Laguerre-Gaussian beams, we show that optically bound structures can conserve their spatial arrangements even while orbiting along the beam circumference. Download

Experimental and theoretical determination of optical binding forces

Brzobohaty, O.; Cizmar, T.; Karasek, V.; Siler, M.; Dholakia, K.; Zemanek, P.
OPTICS EXPRESS 18 (2010) 25389-25402

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.Download

Long-range one-dimensional longitudinal optical binding

Karasek, V.; Cizmar, T.; Brzobohaty, O.; Zemanek, P.; Garces-Chavez, V.; Dholakia, K.

We create extended longitudinally optically bound chains of microparticles with the use of counter-propagating "nondiffracting'' light fields, the so-called Bessel beams. The beam homogeneity and extended propagation range allow the creation of 200 mu m 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. Download.