Electromagnetic Penetration and Reflection Analysis in Fractal Structures Using Three-Dimensional Empirical Mode Decomposition

In this study, fuzz structures in tungsten surfaces are artificially generated using the midpoint displacement algorithm (MDA) based on the random fractal. The finite-difference time-domain (FDTD) method is employed to simulate electromagnetic wave propagation in the fuzz structures with different fractal dimension sizes. To analyze electromagnetic penetrations and reflections around the fuzz structures, we adopt the three-dimensional empirical mode decomposition (TEMD) to decompose simulation results by FDTD in the spatial frequency domain. The computation results showed that the distribution of electric field intensity is decomposed into 3-D intrinsic mode functions (IMFs), indicating resonances triggered by electromagnetic waves hitting the fuzz structures in the tungsten surface from high spatial frequency to low spatial frequency. These decomposed IMFs revealed the optical properties of fuzz structures regarding the relationship between fractal dimension sizes and the electromagnetic penetrations and reflections in the tungsten surface.