Display omitted •First demonstration of LIPSS as polarization gratings.•Optical behavior can be modified changing LIPSS morphology in the fabrication process.•Results supported by computational modelling of light-LIPSS interaction.•Fast LIPSS generation with a setup based on line-focused beam and imaging system.•Potential applications as reflective waveplates, using a simple, one-step process. A fast and reliable method for the fabrication of polarization modifying devices using femtosecond laser is reported. A setup based on line focusing is used for the generation of LIPSS on stainless steel, processing at different speeds between 0.8 and 2.4 mm/s with constant energy per pulse of 1.4 mJ. SEM and AFM characterizations of the LIPSS show a progressive increase in period as the processing speed increases, while height remains approximately constant in the studied range. Optical characterization of the devices shows an induced change in the polarization of the reflected beam that varies with the processing speed, which allows a controlled fabrication of these devices.