Terahertz waveguiding through 3D-Printed Bar-Nested Hollow-Core optical fibers

Terahertz (THz) frequencies, ranging from 0.1 to 10 THz, offer unique sensing, imaging, and high-speed communications applications. However, these electromagnetic radiations experience high attenuation in free-space transmission, emphasizing the need for a low-loss waveguiding solution, often limited by material absorption. Negative curvature hollow-core fibers offer a promising solution by confining the light within an air core region, further reducing material absorption losses. This study presents the design, fabrication, and characterization of a simple bar-nested tubular hollow core fiber tailored for operation in the THz regime. The bar nested four-tube fiber design parameters are numerically optimized using finite element simulations. The cyclic olefin copolymer-based fiber is fabricated through fused deposition modeling in a 3D printer, enabling rapid prototyping and intricate fiber designs. The experimental results demonstrated a measured transmission loss of 7.6 dB/ m for the fabricated fiber at 750 GHz with a bandwidth of 100 GHz. The differences observed between numerical and experimental losses are attributed to the fabrication imperfections, surface scattering losses, and coupling losses, highlighting the challenges and potential of 3D printing for THz waveguide development.