Angle- and polarization-dependent reflection and backscattering from FS-LIPSS covered stainless steel surfaces: experimental study

Large double-scale random rough surfaces covered by femtosecond laser-induced periodic structures are produced experimentally. Irradiation circumstance is considered as the main approach for manufacturing various samples. Fabricated surfaces on the steel substrate are full of high spatial frequency ripples which are crossed by deeper grooves. A polarized He–Ne laser beam is utilized to illuminate the complex surfaces and probe their optical features. Intensities of the reflected and backscattered beams at various incident angles (from small values to large amounts) are monitored in this regard. Results show that the linearly polarized probe beam is scattered diffusely and also de-polarized significantly after striking the irradiated surfaces. However, the amounts of de-polarization of the reflected/backscattered lights are dependent on characteristics of the surface as well as the initial polarization and incident angle of the probe beam. Besides, a relation between the optical response and orientation of the samples is also observed. Finally, at last section, discussions concerning the physical phenomena that are playing a role in the optical response of the samples are presented in detail. Our experimental results reveal that photo-ablation with ultrashort laser systems is highly sensitive and fast enough method for fabrication of surfaces with applications in industry and medical fields in which controlled light reflections or backscattering are needed.