This thesis aims to characterize the photopolymer resins designed for the 3D printing of Gradient Refractive Index (GRIN) lenses. This thesis focuses explicitly on preparing UV-curable inks doped with nanoparticles that are custom-synthesized for sophisticated optical applications. Four different ink formulations have been studied, including epoxy-based and PMMA-based, together with two commercial UV-curable resins, which are a combination of acrylates and epoxies. Spectroscopy testing of these inks is conducted to study their optical performance for properties like the transmittance and absorbance over the UV, visible light, and NIR regions. The results show that it is possible to obtain significantly different behavior in the optical properties of materials compared to the inks without nanoparticles, offering a promising pathway for developing GRIN lenses with superior characteristics. This research also reports on some modifications performed on an Elegoo Mars 4 DLP printer to control a projector and the DMD device for arbitrary exposure times, further contributing to the development of high-performance optical devices through additive manufacturing.