Development of periodically concentric rings within microcavity upon femtosecond laser irradiation

Understanding the formation mechanisms of the nanostructures and their designs has important implications for both the fundamental science and application prospects. In this study, we proposed a strategy for femtosecond laser-induced high regularity concentric rings within silicon microcavity. The morphology of the concentric rings can be flexibly modulated by the pre-fabricated structures and the laser parameters. The physics involved is deeply explored by the Finite-Difference-Time-Domain simulations, which reveals that the formation mechanism can be attributed to the near-field interference of the incident laser and the scattering light from the pre-fabricated structures. Our results provide a new method for creating the designable periodic surface structures.