Study and manipulation of meso-scale systems using optical tweezers

Optical traps or tweezers offer the possibility of study and the controlled manipulation of systems in the meso-scale. The manipulation can be achieved by direct interaction of particles with the trapping light itself, as well as by inducing micro-flows that can affect the dynamics of particles which, in turn, may be used to study the flows themselves. In the first half of the talk, we study the spin orbit interaction (SOI) of light in optical tweezers, where both the spin redirectional topological phase, and the spin Hall effect (SHE) can be enhanced using a stratified medium in the path of the trapping light beam. The enhanced SOI and SHE leads to controlled transportation and rotation of micron-sized particles in the optical trap. In the second part of the talk, I will discuss the creation of micro-bubbles in the trap that can be used in a process akin to lithography, where permanent micro-patterns can be created by controlled manipulation of the bubbles. The bubbles also induce flows that affect the trajectory of particles in their vicinity. The particles can be then used as probes to study the nature of microhydrodynamic flows.