Femtosecond laser induced the graded impedance matching structure to achieve multi-spectrum EM wave absorption performance

Optimal impedance matching is crucial for enhancing the performance of electromagnetic (EM) absorbing materials. In this study, a gradient impedance matching layer with component gradient and structural gradient was prepared on SiC_f/SiCN composites by femtosecond laser (fs laser) with different adjacent spot distance. The results show that the EM wave absorption is optimal when the spot distance is 30 μm, possessing the minimum reflection coefficient (RC_min)of −15 dB with a thickness of 2.05 mm, and the absorption performance at the frequency of 9.9 GHz reaches 96.8 %, while the absorption in the UV-to-NIR ranges reaches 82 %. This is attributed to the appropriate adjacent spot distance which allows the fs laser irradiated SiC_f/SiCN composites surface to build nanoparticle-attached dune-like periodic structures from the structure and composition together regulating the impedance matching. In addition, fs laser induced defects and nano-heterogeneous interfaces enhance the polarization loss. This study provides a new technological approach to the multi-spectrum EM wave absorption properties of SiC_f/SiCN composites.