Achievement of large spot size and long collimation length using UV curable self-assembled polymer lens on a beam expanding core-less silica fiber

We report a novel three-segmented fiber-collimator using self-assembled fluorinated polymer lens and a beam expanding coreless silica fiber of 200-μm diameter spliced to single-mode optical fiber. Both numerical and experimental analyses are presented for design, fabrication, and optical characterization of the device. We have obtained a working distance over 6 mm and a stable spot size over 50 μm in a wide wavelength range of 1.51-1.59 μm.