|M.Sc Student||Bar-David Daniel|
|Subject||Fluidic vortices generated from optical vortices in a|
|Department||Department of Mechanical Engineering||Supervisor||Professor Tal Carmon|
|Full Thesis text|
Liquid micro-cavities provide a way to explore an abundant of diverse optical effects since Arthur Ashkin studied optical resonances in levitating droplets in 1977. In such droplets, light can circulate while reflected at an angle shallower than the total internal-reflection angle.
Liquid resonators present many advantages. They are easy to fabricate and manipulate, and their interface is exceptionally smooth, minimizing scattering losses. Furthermore, liquid resonators enable the study of phenomena that are unique to liquids, such as capillary wave. Additionally, momentum conservation consideration inside a micro-droplet cavity implies that light circulating in a micro-droplet generates micro-flows within the envelope of the drop. Despite many studies in micro-droplet resonators, such flows were never before studied nor even theoretically suggested.
In this work, we fabricate and study a liquid optical resonator. The flows are induced by the forces that light applies. These flows are mapped using a fluorescent marker. We took a special care in verifying that the nanoparticles are indeed probing the flows and that the relative speed between the nanoparticles and the liquid molecules is almost zero.
We report here on the experimental observation of fluidic micro-vortices that are generated from the angular-momentum that the optical vortex provides. The flows are parametrically studied and, as expected, exhibit an increase of rotation speed with optical power and decrease with viscosity.
Besides the fundamental interest in light-flow interactions including in opto-fluidic cavities, the optically controlled flows can serve in sensors by bringing analytes into the optical-mode maximum-power region.