Toward the Stable Optical Trapping of a Droplet with Counter Laser Beams under Microgravity

To identify the optimum conditions for the optical trapping of a droplet under microgravity, we theoretically analyzed the efficiency of trapping with counter laser beams. We found that the distance between the two foci is an important parameter for obtaining stable trapping conditions. We also performed an optical trapping experiment with counter laser beams under microgravity. The experimental results correspond well to the theoretical prediction

Holographic optical trapping

Holographic optical tweezers use computer-generated holograms to create arbitrary three-dimensional configurations of single-beam optical traps useful for capturing, moving and transforming mesoscopic objects. Through a combination of beam-splitting, mode forming, and adaptive wavefront correction, holographic traps can exert precisely specified and characterized forces and torques on objects ranging in size from a few nanometers to hundreds of micrometers. With nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps offer extraordinary access to the microscopic world and already have found applications in fundamental research and industrial applications.Comment: 8 pages, 7 figures, invited contribution to Applied Optics focus issue on Digital Holograph

Numerical Modelling of Optical Trapping

Optical trapping is a widely used technique, with many important applications in biology and metrology. Complete modelling of trapping requires calculation of optical forces, primarily a scattering problem, and non-optical forces. The T-matrix method is used to calculate forces acting on spheroidal and cylindrical particles.Comment: 4 pages, 4 figure

Self-trapping of Bose-Einstein condensates in optical lattices

The self-trapping phenomenon of Bose-Einstein condensates (BECs) in optical lattices is studied extensively by numerically solving the Gross-Pitaevskii equation. Our numerical results not only reproduce the phenomenon that was observed in a recent experiment [Anker {\it et al.}, Phys. Rev. Lett. {\bf 94} (2005)020403], but also find that the self-trapping breaks down at long evolution times, that is, the self-trapping in optical lattices is only temporary. The analysis of our numerical results shows that the self-trapping in optical lattices is related to the self-trapping of BECs in a double-well potential. A possible mechanism of the formation of steep edges in the wave packet evolution is explored in terms of the dynamics of relative phases between neighboring wells.Comment: 8 pages, 15 figure

Rotational dynamics of optically trapped polymeric nanofibers

The optical trapping of polymeric nanofibers and the characterization of the rotational dynamics are reported. A strategy to apply a torque to a polymer nanofiber, by tilting the trapped fibers using a symmetrical linear polarized Gaussian beam is demonstrated. Rotation frequencies up to 10 Hz are measured, depending on the trapping power, the fiber length and the tilt angle. A comparison of the experimental rotation frequencies in the different trapping configurations with calculations based on optical trapping and rotation of linear nanostructures through a T-Matrix formalism, accurately reproduce the measured data, providing a comprehensive description of the trapping and rotation dynamics.Comment: (21 pages, 5 figures