Fabrication of antireflective hydrophobic periodic micro-hole structures on ZnS surface by femtosecond laser direct writing

ZnS has a promising wide range of applications in optical and optoelectronic areas. But the Fresnel reflection on ZnS surface reduces the transmittance of light and causes an obstacle in its applications. Thus, it is crucial to minimize the Fresnel reflection to promote the antireflection property. This paper demonstrates an effective way to fabricate antireflective periodic micro-hole structures on ZnS surface by femtosecond laser direct writing. The effects of laser power, scanning speed on the morphology of the holes are investigated. The fabricated structures exhibit an excellent antireflection property, and achieve more than 30% decrease in reflectance in the near-ultraviolet spectral wavelength range and near-infrared spectral region (200-800 nm), reducing 35% in 280 nm, especially. Besides, the prepared surface demonstrates effective performance concerning hydrophobicity with a contact angle of 107.4°, and the contact angle of unprocessed ZnS is 96.2°. These results show that the femtosecond laser can induce the antireflection and hydrophobic properties on the surface of ZnS, which has a potential application in outdoor optical and optoelectronic devices. (paper)