Irradiation of Dye-Doped Microspheres with a Strongly Focused Laser Beam Results in Alignment upon Optical Trapping

Abstract

The irradiation of dye-doped polystyrene microspheres with an argon ion laser (488 nm) changes their properties and creates photopatterns. These photopatterns can be manipulated by altering the location of the focal point inside the spheres. The illuminated microspheres subsequently undergo one-dimensional rotational diffusion about the optical axis when captured in an optical trap (985 nm). This behavior is well described by a model in which the differently irradiated portions of the microsphere possess different refractive indices.