Refractive index measurements of photo-resists for three-dimensional direct laser writing

Femtosecond 3D printing is an important technology for manufacturing of nano- and microscopic devices and elements. Crucial for the design of such structures is the detailed knowledge of the refractive index in the visible and near-infrared spectral range and its dispersion. Here, we characterize 5 photoresists that are used with femtosecond 3D direct laser writers, namely IP-S, IP-Dip, IP-L, IP-G, and OrmoComp with a modified and automized Pulfrich refractometer setup, utilizing critical angles of total internal reflection. We achieve an accuracy of 5⋅10−4 and reference our values to a BK-7 glass plate. We also give Abbe numbers and Schott Catalog numbers of the different resists. Their refractive indices are in the 1.49-1.57 range, while their Abbe numbers are in the range between 35 and 51.