Nanoablation of Si surface with femtosecond-laser-induced plasmonic near-fields

Abstract

Superimposed multiple shots of low-fluence femtosecond (fs) laser pulses form a periodic nanostructure on various kinds of solid surfaces through ablation. It has been proposed that the periodicity of the nanostructures is attributed to the excitation of surface plasmon polaritons (SPPs). However, the excitation of SPPs on non-metallic material surfaces was never been directly observed. We have observed anomalies appearing in the reflection of intense fs laser pulses at a Si grating surface with a grating structure. The results have exhibited an abrupt decrease to create a sharp dip at a specific incident angle, where the Si grating surface was deeply ablated along the edge of the grooves periodically. The experimental results and model calculation provide directly evidence that SPPs can resonantly be excited at the interface between air and the non-metallic material surface and that enhanced near fields can form periodic structures on the surface.