Femtosecond laser induced nano-meter size surface structures on ZnSe film

We realize femtosecond laser-induced high spatial frequency nano-meter size periodic surface structures with a periodicity about 140nm-170 nm on ZnSe film in one step. Compared with bulk ZnSe, the periodicity and fluence threshold of the surface structure on ZnSe film are smaller and lower. We propose the shortened melting duration, which caused by the higher thermal conductivity of the sapphire substrate, is the origin of the difference between the bulk ZnSe and ZnSe film. Surface capillary wave is easier frozen with shorter melting duration leaves smaller periodicity. Meanwhile, we also found stripes on the surface of sapphire with much lower threshold than previously reported values. The results can benefit advanced optoelectronic device fabrication and fundamental research.