Stereolithography 3D printing of a cyclic olefin resin for terahertz quasi-optical applications

Stereolithography (SLA) additive manufacturing (AM) is an emerging technique for fabricating terahertz (THz) complex quasi-optical components at low-cost. However, most photopolymers exhibit significant absorption losses, limiting the performance of SLA-produced quasi-optics. Cyclic Olefin Resin (COR) was identified as a promising alternative owing to its formulation of olefinic monomers highly transparent to THz radiation. SLA-fabricated COR samples were characterized from 0.5 to 6 THz using time-domain spectroscopy. Gyroid lattices were printed to assess the feasibility of sub-wavelength features at 1 THz. Additionally, plano-convex and Fresnel lenses were manufactured and evaluated using a THz quantum cascade laser (QCL) system. COR exhibited an absorption coefficient of (3.96 ± 0.01) cm–1 at 1 THz, increasing to (11.29 ± 0.39) cm–1 at 6 THz, substantially lower than conventional photopolymers, which exceed 60 cm–1 at 2 THz. Gyroid lattices demonstrated reproducible features, while the lenses operated efficiently at 3.4 THz. COR was shown to be considerably more transparent to THz radiation than standard photopolymers, enabling the fabrication of efficient quasi-optics using low-cost SLA systems, improving accessibility of bespoke THz optical components.