Exploring Transport Regimes of Electromagnetic Waves in 3D Amorphous Dielectric Networks through Numerical Studies

Engineered randomness in dielectric materials to access different regimes of wave transport have recently attracted substantial fundamental interest, with practical relevance to applications in sensing, communications, quantum cascade lasers, and enhanced photocurrent generation. Of particular interest are the recently introduced Local Self-Uniform structures, which are disordered networks exhibiting strong spatial correlations, and are built from trivalent node scattering centers which can be experimentally fabricated in silicon-based platforms.

We investigate different optical transport regimes in these three-dimensional disordered dielectric media. These engineered structures exhibit regimes of transparency, classical photon diffusion, complete photonic bandgaps (PBG), and strong scattering leading to Anderson-Localized modes at the edges of the forbidden bands. Since the localization length exceeds the scattering length, a clear observation requires the modeling of large samples only recently possible with computational advancements in cloud-based Finite-Difference Time Domain (FDTD) simulations. We characterize these regimes by analyzing the reduction of the mean free path as the system approaches the PBG, the anomalous decay of transmission at specific wavelengths, and the temporal confinement of a quasi-monochromatic focused beam, in agreement with existing theory.