Advanced ultrathin metallic directional coupler operating at 0.75–1.1 THz

Terahertz components are crucial for next-generation high-frequency measurement and wireless communication. All-metal couplers are essential for measuring watt-scale terahertz power where the terahertz coupling foil is the core component of the all-metal coupler. The above devices are also widely used in vector network analyzer frequency expansion modules. However, current manufacturing methods, including CNC machining, EDM, and UV-LIGA, face challenges such as limited precision, material losses, and operational constraints in the THz range. This work presents a compact, wide-bandwidth, highly directional micro-aperture waveguide bidirectional coupler for THz applications (750–1100 GHz), utilizing a hybrid integration approach. The core component, a copper-based coupling foil, was fabricated using silicon-based MEMS technology, achieving sub-micron precision and surface roughness under 50 nm. The upper and lower waveguides were manufactured via CNC milling, ensuring high structural accuracy and consistency. Test results demonstrate that the assembled coupler achieves a coupling level of −10 to −15 dB and directivity exceeding −20 dB, outperforming conventional fabrication techniques. Additionally, failure mechanisms arising during the manufacturing process are analyzed in detail. The proposed hybrid integration approach provides a reliable and scalable solution for fabricating high-performance THz components above 750 GHz. This work paves the way for improved fabrication strategies in next-generation THz devices, enabling more efficient and precise THz measurement and communication systems.