Nonlinear optical feedback for nano- and micropatterning of silicon surface under femtosecond laser irradiation

Silicon based micro- and nanophotonics yielding plenty of applications from black silicon for photovoltaics to all-dielectric nanoantennas for sensing and nonlinear optics requires advanced methods of fabrication. Here we provide a detailed investigation of femtosecond laser fabrication of silicon based miro- and nanostructures formed via self-organization processes revealing a strong influence of nonlinear optical feedback during their growth under multipulse irradiation. Our results are supported by the experimental study of the effects of laser wavelength, fluence, exposure time, and ambient gas pressure. We demonstrate that both sub-µm and µm-scale structures have similar principles of formation, which paves the way to controllable and low-cost fabrication of advanced optoelectronics devices with multilevel patterning of functional elements.