Bend insensitive graded index multimode polymer optical waveguides fabricated using the Mosquito method

We fabricate low-loss graded index (GI) circular core multimode polymer optical waveguides with 90o bending and demonstrate low bending loss even if the bend radius is as small as 1 mm. In the several fabrication methods for GI-core polymer waveguides already proposed, we adopt the “Mosquito method†that utilize a microdispenser because the Mosquito method makes it possible to fabricate waveguides directly on board at desired places on a printed circuit board, and to draw various patterns of cores including curves. However, in the waveguides including such curved cores, the additional transmission loss due to the bending (bending loss) is a concern. Thus, we characterize the fabricated GI-core polymer waveguides with bending: using two kinds of cladding monomer with different refractive indexes for fabricating waveguides with bending. We found when the NA of waveguides was as high as 0.35, no additional loss due to bending was observed even if the bending radius is as small as 1 mm. The core diameter of the fabricated waveguides is 50 μm, and it is possible to further decrease the bending loss in the waveguides with smaller core diameter. Furthermore, utilizing the Mosquito method, we fabricate waveguides with not only horizontally curved cores but also vertically curved ones. Waveguides with vertically curved cores could make it possible to realize three-dimensionally optical wiring applicable to on-board optical interconnects.