Ryota OMORI, Tamiki KOBAYASHI, Shinji MIYAMOTO and Atsuyuki SUZUKI

Department of Quantum Engineering and Systems Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113 Japan

(Received November 7, 1995; Accepted December 6, 1995)

The maximum axial trapping efficiency Q_max has been measured in water, ethanol, butanol and octanol for polystyrene latex spheres having a diameter of 2-15 μm. The effects of the diameter of the particle as well as the refractive index and the viscosity of surrounding medium have been investigated. For particles of d≥7 μm, Q_max is almost independent of particle size, while it decreases as the diameters decrease to d≤5 μm. It is also noted that Q_max is affected by the viscosity rather than the refractive index of the surrounding medium.

Key words : laser manipulation, optical trapping, trapping efficiency, radiation pressure, ray optics, laser, microsphere, polystyrene latex