  Irradiation of solids with ultrashort pulses using laser sources in the
mid-infrared (mid-IR) spectral region is a yet predominantly unexplored field
that opens broad possibilities for efficient and precise surface texturing for
a wide range of applications. In the present work, we investigate both
experimentally and theoretically the impact of laser sources on the generation
of surface modification related effects and on the subsequent surface
patterning of metallic and semiconducting materials. Through a parametric study
we correlate the mid-IR pulsed laser parameters with the onset of material
damage and the formation of a variety of periodic surface structures at a laser
wavelength of {\lambda}L=3200 nm and a pulse duration of {\tau}p=45 fs. Results
for nickel and silicon indicate that the produced topographies comprise both
high and low spatial frequency induced periodic structures, similar to those
observed at lower wavelengths, while groove formation is absent. The
investigation of the damage thresholds suggests the incorporation of nonlinear
effects generated from three-photon-assisted excitation (for silicon) and the
consideration of the role of the non-thermal excited electron population (for
nickel) at very short pulse durations. The results demonstrate the potential of
surface structuring with mid-IR pulses, which can constitute a systematic novel
engineering approach with strong fields at long-wavelength spectral regions
that can be used for advanced industrial laser applications.
