Accurate core alignment for polymer optical waveguide in the mosquito method for high-efficient coupling

We demonstrate the importance of vertical position accuracy of formed core in the polymer optical waveguides fabricated using the Mosquito method for 3-dimensional wiring. We theoretically confirm the core vertical position deviation from the designed position is caused by the several fabrication parameters, the needle size and the needle-scanning speed. As an example of 3-dimensional wiring, we focus on the optical path conversion by 45-degree mirrors, and experimentally investigate the influence of the core vertical position on the coupling efficiency to other components via a 45-degree mirror. By forming the cores on appropriate height in the cladding, graded-index core optical waveguides exhibit a slight loss increment as low as 0.2 dB due to mirror structure, realizing the high efficient coupling via a 45-degree mirror.