90-degree bent core polymer optical waveguide coupler for low loss lens-less light coupling between laser / photodetector and fiber

In this paper, we present direct fabrication of vertically 90-degree bent core polymer optical waveguide couplers to be integrated in optical engines enabling lens-less light coupling between laser source / photodetector and fiber with low loss. We apply the Mosquito method that we developed as a fabrication technique for single-mode and multimode polymer optical waveguides with circular cores. Because of the unique fabrication procedures of the Mosquito method, three-dimensional core alignment is possible, and thus 90° bent core can be formed directly on a laser chip. We would like to emphasize that the bending radius as small as 2 mm or less could be formed, while the insertion loss of the waveguide is as low as 5 dB.