Thursday, November 29, 2012

Our latest paper on optically-controlled active media

My colleagues and I just published a paper in Nature Photonics entitled "Superdiffusion in Optically Controlled Active Media." You may access the paper via this link to Nature Photonics or read about it in UCF Today.

I should point out that the claims made in the article in UCF Today is a bit over-reaching. What we have done is demonstrated that the coupling between light and particles in suspension models nonequilibrium processes that share some characteristics with similar processes inside cells. This is because the colloidal particles exchange energy randomly with their thermal bath (the water) and with the laser's radiation.

Importantly, the nature of the light-matter coupling is random due to multiple scattering by the particles, which establishes a three dimensional speckle inside the suspension.  This speckle exerts random forces on the particles which adds an additional component to their motion, besides that of Brownian motion. The resulting effect is that the particles move superdiffusively for times that are shorter than the decorrelation time of the speckle (which was about 1 millisecond).

Besides serving as a model system, I think it may be interesting to explore its ability to control some types of reaction kinetics. If reactants in solutions are driven apart from one another before they have a chance to react, then this would present a mechanical way of slowing the reaction of the bulk solution.

If you can access the article, then I hope you enjoy it!