Terahertz Dielectric Property Characterization of Photopolymers for Additive Manufacturing

In this paper, resin-based photocurable polymer materials for stereolithography, digital-light-processing (DLP), and polymer-jetting additive manufacturing techniques were characterized from 0.2 to 1.4 terahertz (THz) for their comprehensive dielectric properties, e.g., refractive index, absorption coefficient, dielectric constant, and loss tangent, by using laser-based THz time-domain spectroscopy. A total of 14 photocurable 3D-printing polymers were chosen, owing to their suitability, in terms of printing resolution, material characteristics, and so on, for millimeter-wave (mm-wave) and THz applications. The measurement results from 0.2 to 1.4THz, the dielectric constants of all photopolymer samples under test are between 2.00-3.10, while the loss tangents are from 0.008 to 0.102, which are quite useful for many applications, e.g., 3D printed antennas and THz transmission lines, which were demonstrated by an asymptotically quasi-single-mode Bragg fiber microfabricated by DLP micromanufacturing technique using HTM140-V2 photopolymer, which is previously reported at the nominal frequencies from 0.246 to 0.276 THz.