Rapid fabrication of antireflective structures on ZnS surface by spatial shaping femtosecond laser

Antireflection performance and fabrication efficiency are key factors that affect the practical application of antireflective structures. Nowadays, how to combine good antireflection performance with highly efficient processing is still a difficult problem. In this work, a novel and scalable method of fabrication of antireflective LIPSS (laser induced periodic surface structure) on ZnS surface by spatial shaping femtosecond laser is proposed. A Gaussian beam is converted to a line beam by a cylindrical lens transformation. The focal long axis of line beam is on the scale of centimeters, and the minor axis is on the scale of micrometers. Hence, the fabrication efficiency can be significantly improved by adjusting the scanning direction perpendicular to the major axis. Notably, the proposed highly efficient method only takes 21 s to complete the fabrication of 1 x 1 cm2 antireflective ZnS surface with excellent antireflective property. At the laser power of 500 mW, scan speed of 1.0 mm/s, scan interval of 0.55 cm, the transmittance of fabricated antireflective structures maintains 78-87.5% at 2.5-10 mu m, with the average transmittance of 81.3%, 5.9% higher than that of untreated ZnS. This proposed method may open a revolutionary concept for the rapid antireflective surface laser processing, which has a great application potential in energy, military, aerospace and other fields.