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DF: Dielektrische Festkörper

DF 11: Electric, Electromechanical and Optical Properties II

DF 11.3: Vortrag

Freitag, 31. März 2006, 11:50–12:10, M{\"U}L Elch

Trapping and Manipulation of Micro- and Nanoparticles on the Surfaces of Lithium Niobate Crystals utilizing Light-Induced Electric Space Charge Fields* — •F.Y. Kuhnert¹, J. R. Adleman², H. A. Eggert¹, D. Psaltis², and K. Buse¹ — ¹Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn — ²Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125

The ability to trap and to manipulate inorganic particles and organic cells of micrometer and submicrometer size plays an important role in the field of Optofluidics. Optical tweezers are well known that use high intensity laser beams to trap particles due to the field gradient of a focused laser beam. Here we try a novel approach: Irradiating a lithium niobate crystal with an inhomogeneous light pattern leads to charge separation along the c-axis which causes electrical fields. As a result strong field gradients are present in proximity of the crystal surface. In contrast to optical tweezers, the strength of the electrical field depends only on the exposure i.e. on the product of intensity and time. With a laser beam we record space-charge and field patterns of circular shape as well as space-charge gratings with period length between 20 micron and 1000 micron into a lithium niobate crystal doped with 0.05 wt% Fe. Chalk particles (~15 micron diameter) and silicon dioxide particles (80 nm diameter) in air as well as silicon carbide particles (130 nm diameter) in liquid are trapped and moved on the crystal surface. * Financial support by the DAAD, the DFG (BU 913/17), and the Deutsche Telekom AG is gratefully acknowledged.