摘要： Surface nanostructuring has received increasing attention in recent years due to the wide range of applications in which it offers advantages. Particularly, Laser-Induced Periodic Surface Structures (LIPSS) have proven useful for surface functionalization [1]. LIPSS are periodic formations generated in most materials when irradiated with linearly polarized radiation. The orientation of these structures is directly linked to the polarization of the incident light, while other parameters of their morphology such as period and depth can be controlled with the number of pulses, fluence, wavelength and pulse duration of the incident light. Due to their periodic nature, LIPSS behave optically as nanogratings [2], which have been largely studied as polarization converters (or Polarization Gratings, PGs). PGs are structures that introduce a phase shift in the incident light, which produces a change in its polarization state [3]. Therefore, PGs have potential applications as reflective waveplates [4], showing advantages over transmission waveplates such as higher damage thresholds and a lower temporal dispersion of the pulse. So far, PGs have been fabricated with methods such as direct laser interference or lithography [5]. The main drawbacks of these methods include limited choice of periods for the generated structures or a complex and environmentally unfriendly fabrication process, which could be overcome by a fabrication method based on LIPSS. In order to fabricate LIPSS-based PGs, stainless steel samples were irradiated with a 800 nm femtosecond Ti:Sapphire laser. The laser was focused onto the surface of the sample through a cylindrical lens with a focal length of 10 cm. The sample was translated perpendicular to the laser beam with a mechanical stage at a constant speed, generating LIPSS in a large area of 5 mm x 5 mm in a few seconds. By varying the fluence of the beam and the speed of the stage, LIPSS with different parameters were fabricated. Topography of the samples were characterized with AFM and SEM (Fig. 1a) microscopes, and polarization conversion and reflectivity were examined with a polarimeter. Results show that a gradual change in LIPSS morphology is associated to a gradual change in the ellipticity of the laser beam (Fig. 1b). It is also observed that LIPSS geometry changes smoothly with processing parameters. Therefore, it is proven that LIPSS-based PGs can be fabricated experimentally, and that the properties of such PGs can be tuned changing the LIPSS geometry, as expected. These results are in good agreement with the performed FDTD simulations for different LIPSS morphologies.