Femtosecond laser induced periodic surface structures on crystals: Formation, evolution and application

In the research field of laser induced periodic surface structures (LIPSSs), the ones located at the superficial surface of the solid materials (s-LIPSSs) induced by femtosecond laser have been widely investigated. It is noticed that, the formation of s-LIPSSs is limited to a relatively narrow parameter window and, as the parameters are tailored, such structures would evolve into novel topographies which possess laser-ablated micro-grooves with LIPSSs being deeply located at the groove-bottoms (d-LIPSSs). In this work, both s-LIPSSs and d-LIPSSs are produced on the surface of Nd:LGGG crystal by using femtosecond laser irradiation. Experimental investigations and numerical modeling convince the crucial role of surface plasmon polariton excitation in the formation of both structures. The evolution of surface topographies and the dependence of LIPSSs-periods on the fabricating parameters can be mainly ascribed to the feedback mechanisms of s-LIPSSs and laser-induced micro-grooves. Furthermore, based on the d-LIPSSs, a novel approach is proposed to fabricate 2-dimensional surface with orthogonal dual-periods. Such structure shows enhanced polarization-sensitive antireflectivity within long wavelength range and the ability for NIR detection, which is superior to the traditional surface structure composed of s-LIPSSs.