Integrated polymer micro-ball lenses for two-dimensional divergence reduction of light from single-mode optical waveguides

Reduction of the divergence angle of a beam coupled out from an optical waveguide is desired in many applications. Collimation in one dimension has been demonstrated, see e.g. [1-3] However, for some applications such as on-chip optical coherence tomography (OCT) or Raman spectroscopy [4,5], it is necessary to produce a light beam that is collimated in two dimensions in order to increase the efficiency of chip-sample coupling. In our previous work [6], we have designed a fabrication procedure of a direct on-chip reflowed polymer micro-ball lens to enable light collimation in both, horizontal and vertical directions. In this work, we realized the complete design, optical characterization and demonstrate the feasibility of mass production.