Interaction of highly focused intense laser radiation with transparent dielectrics: Subwavelength nanogratings formation

Femtosecond laser writing of birefringent subwavelength nanolattices in dielectrics has been studied for almost two decades since it reveals a number of applications for optical memory devices, optical waveguides, microfluidic channels, etc. In this work, a numerical study of the formation of plasma quasiperiodic nanostructures in a fused silica in the propagation direction of a focused laser pulse is carried out. It is shown that the focused beam creates a dense plasma, which provides an effective reflection of the incident laser pulse, leading to the formation of a standing wave. In the bundles of standing wave, an effective ionization emerges, which forms plasma gratings with a subwavelength period. The conducted modeling allows us to determine the conditions under which the proposed regime of material nanostructuring is possible. It is shown that the energy absorbed in plasma gratings will ensure the substance melting, which leads to the formation of "frozen" quasiperiodic nanopatterns.