Influence of lattice geometry on the terahertz dielectric properties of 3D printed photopolymers

Abstract The burgeoning field of terahertz (THz) technology has witnessed remarkable advancements, driving the demand for specialized optical components that can efficiently manipulate THz waves. In this context, additive manufacturing has emerged as a transformative approach for fabricating THz optical components with tailored dielectric properties. The dielectric properties of materials in the THz regime, specifically, refractive index, absorption coefficient, dielectric constant, and loss tangent, play a pivotal role in determining the performance of THz optical systems. In this context, this study emphasizes the understanding of how geometric factors affect the dielectric behavior of SLA-printed photopolymers in the THz frequency range. Thus, five different photopolymer-based lattice structures, Diamond (A), Neovius (B), Primitive (C), Gyroid (D), and Fischer-KochS (E), are fabricated, each with four different filling ratios. Afterwards, the dielectric properties of these lattice structures within the 0.5–1.5 THz frequency range are investigated using terahertz time-domain spectroscopy (THz-TDS). The central objective is to examine how the filling ratio 20%–80% affects the spectral response of the lattices in terms of transmission, absorption, refractive index, and permittivity. The results show that low filling ratios of 20%–40% generally yield higher transmittance and lower absorption, whereas higher filling ratios of 60%–80% suppress transmission due to increased scattering and dielectric losses. Diamond and Primitive lattices exhibit higher transmission at low filling but show progressive suppression with increasing infill. Neovius demonstrates stable transmission with low absorption across the considered band, highlighting its suitability for broadband low-loss THz applications. While Gyroid structure provides relatively strong transmission at 20% filling, but significant attenuation at higher infill levels, where dielectric constants and losses increase. Fischer-KochS shows its best performance at intermediate filling ratios, offering relatively higher transmission with moderate losses, while at 80% filling, transmission is suppressed due to stronger dielectric interaction. Overall, these findings highlight the interplay between geometry and filling ratio, establishing practical guidelines for optimizing SLA-fabricated photopolymer lattices in THz applications such as filters, waveguides, and sensors.