Study of the formation of a microrelief on ZnSe- and CdSe-crystal surfaces ablated by excimer KrF-laser radiaton

One-dimensional gratings with a period of $0.5-2.3\text{μ}\text{m}$ are formed on the surfaces of CdSe and ZnSe crystals ablated by two interfering radiation beams of a nanosecond excimer KrF laser. Investigated are the dependences of the shape and depth of gratings on the energy density under irradiation by a single pulse, and on the number of pulses at a given energy density. The maximum grating depth is estimated as $\sim 0.57$ of the period. By forming a one-dimensional grating with a period of $1.5\text{μ}\text{m}$ and a depth of $0.53\text{μ}\text{m}$ on the CdSe-crystal surface, this surface becomes antireflective at a wavelength of $4\text{μ}\text{m}$. The surface reflectivity is reduced by 88 %. A possibility of forming two-dimensional gratings having periods of 1 and $1.5\text{μ}\text{m}$ is demonstrated. (paper)