Fig. 4.

(a)-(c) Alignment of an oblong polystyrene particle on an aluminum grating under the illumination of a laser beam polarized perpendicular to the grating rules. The laser beam was polarized horizontally and focused with a 50x objective lens ( Media 2 ^{(3.7MB, MOV)} ). (d)-(f) The oblong polystyrene particle was aligned with its long axis perpendicular to the grating rules after being illuminated by the polarized laser beam. The focusing of the laser beam and image-taking was through a 10x objective lens. (g) Characterization of rotation speed during alignment versus optical intensity. Rotation speed approaching 35 degree/sec can be achieved with sufficient laser intensity.