Structural limits of Flexographic Printing towards Singlemode Dimension Waveguides

Flexographic printing is a graphical printing process with high throughput potential. In previous research, polymer optical waveguides are printed by sequentially applying UV-polymer layers on a PMMA substrate. Multimodal waveguides are achieved with an optical attenuation of 0.95 to 1.58 dB/cm. Their cross-section dimensions reach from 50 to 500 µm due to using Flexcel NX printing plates. These master plates feature a minimal structure resolution of 10 µm. Further, commercial printing varnish 390119 from Jänecke&Schneemann is used as waveguide core material. This study investigates whether flexo-printing can manufacture single-mode waveguides. Therefore, a novel high-precision multifunctional printing and coating system, NSM Challenger 650 (C650), is put in operation. This equipment allows infeed repetition accuracy in the single-digit micron domain. Additionally, Ektaflex printing plates are introduced to print functional optical structures. These printing plates feature a layout resolution of 2 µm. Finally, optical UV-polymer, designed for waveguide manufacturing, is used as a printing polymer. Optical waveguides with low attenuation and high mode consistency are promised by the polymer's high transparency and significant refractive index difference towards the substrate. Process parameters are examined to answer these questions, and the resulting optical waveguides are geometrically characterized confocally regarding aspect ratio and single-mode capability. A functional characterization is shown using optical attenuation measurement and beam profiler images. Based on these results, flexographic single-mode optical waveguides outlook on optical sensors based on FBG.