[OPTICAL REVIEW Vol. 10, No. 3 (2003) 136-139]
© 2003 The Optical Society of Japan

Rotation of a Fine Particle with Circularly Polarized Anti-Parallel Collinear Laser Beams


National Metrology Institute of Japan, The National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 3, 1-1-1 Umezono Tsukuba, Ibaraki 305-8563, Japan

(Received June 14, 2002; Accepted February 3, 2003; Revised January 23, 2003)

We have succeeded in the operation of rotating a fine particle which was held without mechanical contact by circularly polarized laser beams with opposite propagation directions. A polystyrene latex particle 11.9 μm in diameter deformed in a disk-like shape was dispersed in water, and was trapped using the anti-parallel collinear laser beams which were set up so that they had the circular polarization rotating in the same direction. It was observed that the trapped particle rotated in the same direction as the rotation of the circular polarization of light. Inversion of the rotational direction of the circular polarization of light reversed the direction of the rotation of the particle. Although the rotational speed of a particle varied significantly from particle to particle, it was found to be proportional to the laser beam intensity. A typical value for the rotational speed per beam intensity was 2.1 Hz/W.

Key words: laser trap, laser manipulation, optical motor, circular polarization, anti-parallel collinear laser beams