The Development and Characterization of Polymer Microinjection Molded Gratings

Ruled diffraction gratings were fabricated via injection micromolding and characterized via atomic force and scanning-electron microscopy. A unique aspect of this study was the utilization of commercially available optical grating as the injection molding tooling. After depositing a reflective aluminum (AI) coating with 150 and 250 nm thickness onto the untreated polymer replicas, diffracted power profiles of the polymer gratings were compared with that of the mold. It was found that both the mold and nozzle temperatures, T-mold and T-noz, respectively, are important parameters influencing the fidelity of replication. Statistical analysis, however, revealed that the cyclic olefin copolymer (COC) replicated well the microtopography of the mold but did not replicate properly (within similar to 20 nm) the nanotopography formed by the Al grains. Grain size quantification revealed that the Al coating with 150-nm thickness had smaller grains than that with the 250-nm coating. Furthermore, testing of delamination of the reflective coatings revealed good adhesion between the COC and Al interface. Lastly, photoelasticity measurements showed stress levels only around the gate of the molded components, suggesting that COCs are excellent materials for optical applications. POLYM. ENG. SCI., 48:2169-2177, 2008. (C) 2008 Society of Plastics Engineers