Fabrication and Optical Rotation Characteristics of Anisotropically Shaped Micro-Objects Made of Fluorinated Polyimide

Three-dimensional optical trapping and rotation are demonstrated for fluorinated polyimide micro-objects fabricated by reactive ion etching. Optical rotation occurs in the designed direction due to optical radiation pressure exerted on the sides of the micro-object by a strongly focused Nd³⁺ : YAG laser beam (1.064 μm). The object has shape anisotropy that is not bilateral symmetry but rotational symmetry in the horizontal cross section. The observed rotation speed in ethanol solution is almost proportional to the incident laser power. Fluorinated polyimide materials are useful because they are easy to etch in oxygen plasma, have excellent fabrication quality, are highly transparent in the near infrared region, and have a small specific gravity. Using fluorinated polyimide as the micro-object material makes it easier to achieve optical trapping and increases the rotation speed compared with using silicon dioxide.