Formation of extraordinarily uniform periodic structures on metals induced by femtosecond laser pulses

In this paper, we report an observation of extraordinarily uniform periodic structures on metals following p-polarized femtosecond laser pulses at various obliquely incident angles. The highly uniform structures are oriented parallel to the laser polarization. Angular dependence of the period of these structures is studied, and the results indicate that these structures are formed by the interference between the incident light and excited surface plasmons. Under identical experimental conditions, these highly uniform structures show distinctly different levels of morphological clearness on different metals, and this difference can be explained by considering the electron-phonon coupling strength in different metals.