Supercritical fluid deposition technique enabling metallic coating onto 3D-printed polymer for fabrication of high-aspect-ratio THz devices

Three-dimensional (3D) terahertz devices often have difficulty of fabrication due to smaller feature size and complexity of architecture. We herein propose the new fabrication method by combining two techniques; building 3D polymer architecture using high-resolution 3D printing, followed by coating its surface with metal film using high-step-coverage deposition technique, supercritical fluid deposition (SCFD). Difficulty of metal film formation by SCFD onto the polymer is the largest obstacle, but was overcome by a facile surface modification technique to anneal the polymer in oxygen ambient. We thereby demonstrated the fabrication of THz high-pass filter. Our developed method enables the monolithic integration of necessary components for THz devices, for instance passive components together with waveguides. It obviates assembly of individually fabricated components that leads to potential signal loss caused by misalignment, which is more critical with increasing frequency of THz waves.