220–325-GHz Horn-Type Adapter for Terahertz Microstructured Fiber Measurements

In this article, a novel and innovative approach to characterize THz Bragg fibers using a horn-type adapter is presented, enabling a two-tier calibration method for a direct, efficient, and reliable way to measure THz Bragg fibers, including return loss (RL) and insertion loss (IL). The proposed approach is robust, accurate, and repeatable, making it suitable for designing and optimizing THz Bragg fibers and systems and enabling continued research and development. This study employs a calibration approach, utilizing short-short-load-thru (SSLT) and thru-reflect-line (TRL) calibrations. The horn-type adapter connects a standard WR-3.4 rectangular waveguide and a THz Bragg fiber, allowing the mode conversion from the TE10 mode in the rectangular waveguide to the HE11 mode in the Bragg fiber, with a middle stage of the TE11 mode in the tapered horn region. Additionally, the highly accurate measurement quality presented advantages compared to the existing THz measurement setups, for example, setup complexity, coupling efficiency, impedance adjustability, and less sensitivity to measurement environments, etc. The present approach shows advantages in experimental setup complexity, coupling efficiency, impedance adjustability, measurement repeatability, operator experience required, and setup tool cost compared to other existing THz measurement techniques.