Advances in modeling and optimization for two-photon lithography

Background: Two-photon polymerization (TPP) is one of the most promising methods for the fabrication of metasurfaces due to its ability to create complex, high-resolution nanostructures. However, fabricating these structures using TPP is complex, and predicting the results of the fabrication process is challenging. Aim: We aim to address these challenges by demonstrating how different modeling techniques can be employed to support the fabrication-aware design of metasurfaces. Approach: We introduce and explore three modeling techniques: a simple threshold model, a compact model, and a full model of polymerization. Each model offers different levels of complexity and accuracy. We assess how well each model performs and what limitations they have, using practical examples to show how they can guide the fabrication process. Results: Our comparison highlights the advantages and limitations of each modeling approach. The basic threshold model provides a general overview, focusing solely on the optical aspects and using a simple threshold for the photoresist. Thus, it lacks detailed descriptions of resist behavior. The compact model is semi-empirical, focusing on simplified chemical dynamics of a single species while including essential photochemical processes. By contrast, the full model of polymerization is the most advanced, offering a detailed description of various species involved in the process, such as monomers, polymers, and quenchers. Although it provides the most accurate predictions, it is also the most complex and computationally demanding. Conclusions: By comparing these modeling approaches, we show that the decision on the most appropriate model depends on the specific requirements of the metasurface fabrication process. This analysis helps researchers and engineers determine the most suitable modeling approach for their work.