"Aspects of light-fluid interaction: Optical Manipulation in Densely Scattering Opaque Suspensions" |
| TYPE | Solid State Institute Seminar |
| Speaker: | Mr. Elad Greenfield |
| Affiliation: | Physics Department and Solid State Institute, Technion |
| Date: | 12.05.2013 |
| Time: | 08:30 |
| Location: | Solid State Auditorium(Entrance) |
| Remark: | Ph.D. Student of Distinguished Professor Moti Segev |
| Abstract: | Optofluidics, the science of light interaction with fluids, presents a host of attractive and versatile alternatives to traditional technologies. Optofluidic effects rely heavily on the ability to tailor th e distribution of the optical fields and forces inside particulate-liquid suspensions, with micron scale accuracy. However, densely-packed suspensions of particles, ranging from biological suspensions such as blood, plasma, natural minerals, milk and foods, to synthetic nanoparticle-based drugs, polluted fluids, inks and paints- are inaccessible to optical manipulation. These suspensions scatter the light so heavily that they become opaque: the light diffuses, losing its directionality and localization, and the optical field cannot be externally tailored inside such suspensions. In my thesis, I focus on nonlinear light-fluid interactions. The talk will begin with some brief examples of linear and nonlinear tools for optical manipulation of fluids that were developed as a part of my thesis. The bulk of the talk will focus on theoretical and experimental optical manipulation of the local properties of particulate-loaded, scattering (opaque) suspensions. We show that counter-intuitively, optical forces that multiply-scattered light exerts on the same particles that scatter the light- can give rise to dense shock fronts of particle concentration, propagating deep inside the opaque suspensions. We explore these waves theoretically and experimentally, and exploit them to manipulate the local properties of opaque fluids. We demonstrate optical transport and concentration of large populations of nanoparticles, clearing of localized volumes of opaque solutions from particles, generation of directional light-matter filaments, and light induced suspension-to-gel phase transitions in localized volumes inside scattering fluids. These optofluidic effects penetrate deep into the suspensions, constituting first evidence that light that scatters in fluidic medium can give rise to localized, directional, and hence- 'anti-diffusive' fluidic effects. Further, this is a first demonstration of light manipulating the local properties of multiply-scattering fluids. Possible applications of this work are briefly discussed. |