3D microstructured frequency selective surface based on carbonized polyimide films for terahertz applications

In recent years, frequency selective surface (FSS)-based two-dimensional (2D) and three-dimensional (3D) carbon materials such as carbon nanofibers, carbon nanotubes, and carbon-filled filaments are essential tools to design millimeter-wave radomes, absorbers, electromagnetic interference (EMI) shielding, and antenna reflectors in gigahertz (GHz) regimes. Terahertz (THz) technologies are gaining attentions from medical imaging to security surveillance. In this work, a 3D microstructured FSS using carbon-based polyimide as a precursor to enhance the resonant frequency at the THz range. Furthermore, gold nanoparticles (AuNPs) are embedded on 3D microstructured carbonized polyimide (3D-CPI) film to improve their FSS property through plasmonic effects. From the time domain spectroscopy measurements, 3D-CPI FSS film shows band-stop filter properties in the frequency range of 0.5–1.5 THz and with a maximum return loss (RL) of 40.5 dB (at the resonant frequency of 1 THz). The 3D-CPI/AuNPs film demonstrates the highest RL of 43.7 dB at the higher excitation resonance frequency ≈1.06 THz due to the interaction of plasmonic electrons with scattered delocalized electrons in carbon, which induces the mechanisms for EMI shielding. The results will open insight into 3D plasmonic carbon microstructures as an EMI shielding material at THz frequency.