Correlative metrology for precise refractive index mapping and control in 2PP-fabricated components

Two-photon polymerization (2PP) is a powerful technique for fabricating three-dimensional micro-optical components. However, achieving the designed optical performance is challenging, as the final refractive index (RI) and geometry depend critically on process parameters. This work presents a correlative metrology framework to precisely map and control the RI in 2PP-fabricated polymer waveguides. Our approach integrates lateral shearing interferometry (LSI), Raman Spectroscopy, Atomic Force Microscopy (AFM), and White Light Interferometry (WLI) to characterize components. By analyzing the degree of conversion (DC) via Raman spectroscopy, we identify distinct, material-dependent polymerization behaviors and reveal the significant influence of spatial proximity effects on the final polymer state. By precisely measuring, modeling, and predicting the refractive index and geometry, we are able to provide a metrology frame for improving the performance of 2PP-printed waveguides.