Existing terahertz optical systems generally transmit through free space, facing challenges such as high transmission losses, susceptibility to obstacles, and limited flexibility. Integrating waveguides into terahertz systems emerges as a viable solution to address these issues. Among them, coupling terahertz waves from waveguides to free space efficiently is a key research focus. In this study, we utilize 3D optical printing technology to fabricate a terahertz stepped horn antenna based on polymer composite materials. We analyze the shape of the near-field beam and the far-field gain of the antenna. By designing a stepped structure, impedance matching is adjusted, achieving a gain of 23dBi at 220GHz. Electromagnetic waves are continuously reflected and absorbed within the material, resulting in non-zero tangential electric field components and normal magnetic field components. Additionally, partial absorption of electromagnetic waves by the material reduces interactions between electromagnetic waves at the exit of the horn antenna, resulting in a near-field Gaussian-like beam. Furthermore, utilizing 3D printing technology, we fabricate a horn lens antenna that integrates antenna and lens functionality, further optimizing the near-field Gaussian beam. This work provides a new signal transmission solution for wired terahertz communication systems and applications such as terahertz-based explosion velocimetry.

Terahertz; Horn antenna; Composite polymer; 3D printing; Near-field Gaussian beam