Optical binding - coupled dipoles 

Optical binding is a phenomenon when the objects self-arrange in a laser beam that does not create a trap for single object. The stable objects configuration is obtained due to the interaction between the object via redistribution (scattering) of the incident light. To model this phenomenon we choose a numerical method based on coupled dipoles. The object is split into many dipoles (see the model of a sphere in the figure). Each dipole polarizes according to the electric field at its location. This field is a result of radiation of all other dipoles in the sample. The theory is in details descibed in the related papers mentioned below.

In the stable configuration the spheres are either attached to each other or there is a distance between them. Especially the second case provides an interesting possibility how to compare theoretical predictions with experimental reality.

We focused on so called longitudinal binding. Two counter-propagating incoherent beams interact with two spheres. We looked for parameters (sphere size and refractive index, beam parameters and surrounding medium refractive index) providing stable configuration with a distance between the objects A and B.

Even though the beams are incoherent, there exists multiple scattering of the light from single beam between the objects. That is why the Proceedings of SPIEwavy shape of the force occurs.

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Last modification: 11 Jul 2007