New epoxy-based nanostructured materials containing lanthanide ions doped LaF 3 nanoparticles were obtained by cationic UV-induced ring-opening polymerization. The lanthanide Er 3+ and Yb 3+ ions were added as dopant to LaF 3 nanoparticles. The synthesized NPs were solubilized into cyclohexene oxide and afterwards dispersed, in the range between 3 and 20 wt.%, into CE as dicycloaliphatic epoxy resin. The cured films were completely transparent and TEM analysis showed the absence of macroscopic agglomeration. The fast UV curing process was shown to be efficient on “freezing” the good nanometric dispersion achieved in the liquid formulations. These new materials could find suitable applications in optical communication and in LASER waveguide direct writing.