Optical tweezers with tips grown at the end of fibers by photopolymerization.

We present a method to build an optical tip at the end of a single-mode optical fiber. The tip is grown by a self-writing process: photopolymerization by the light coming from the optical fiber. We developed a technique to produce a flat end surface on the tip. The good optical quality of the tip and the output laser beam was demonstrated by the fact that a counterpropagating optical trap could be constructed by using the tips with parameters comparable to regular fiber traps. Because of the small size of the tips, the tweezers require a much smaller space than regular fiber traps.