Polarimetric properties of imperfect laser-induced periodic surface structures on stainless steel

The use of femtosecond laser nanostructuring to generate Laser-Induced Periodic Surface Structures (LIPSS) is a well-known and robust technology customized for a wide variety of materials. As a low-cost and high-throughput technique it can be applied in fast and large-scale manufacturing. Nevertheless, the quality of LIPSS strongly depends on the optical properties of the light beam (such as its uniformity and polarization state) and the homogeneity of the surface. Therefore, manufactured LIPSS are frequently far from ideal. A key feature of LIPSS is their ability to modulate the polarization state of transmitted or reflected radiation. In this work, we analyze how random fluctuations of LIPSS topography, and randomness of the LIPSS parameters, modify the polarimetric properties of the output beam. We have focused on LIPSS manufactured over steel surfaces. For this, we have computed the electromagnetic field reflected by the surface using a Finite Element Method for different incident polarizations. Finally, the Stokes parameters of the reflected light has been numerically computed, and compared with the ones characterizing the beam after reflection on an ideal periodic LIPSS topography.