Process analysis of COC terahertz fiber fabrication by one-step extrusion

Polymer terahertz (THz) fibers have attracted significant interest due to their compactness and capability in efficient terahertz transmission and gas sensing. The urgent demand for the development of polymer THz fibers lies in the fabrication methods that are compatible with flexible designs, enabling low-loss waveguides. This paper presents a comprehensive investigation into the numerical and experimental aspects of the one-step extrusion process, offering a viable solution for fabricating flexible and low-loss THz waveguides. Precise shaping of the proposed structures is achieved through the choice of COC polymer, moderate flow rate Q_m and mold temperature T_MOLD. Excessive Q_m or T_MOLD leads to partial or complete collapse of the polymer waveguide while insufficient Q_m or T_MOLD is not conducive to a smooth extrusion process. The fabricated waveguide shows an average loss of 3 dB/m over a frequency range from 1.0 to 2.0 THz. The feasibility and practicality of the one-step extrusion establish its potential for further advancements in polymer fiber fabrication.