Keywords: femtosecond laser processing, surface plasmon polaritons, silicon
It is reported that the periodicity of nanostructures formed on solid surfaces with femtosecond (fs) laser pulses is attributed to the excitation of surface plasmon polaritons (SPPs). We have demonstrated that the SPPs can be excited on a Si grating with the intense fs laser pulse, using reflectivity measurement with the linearly-polarized fs laser pulse as a function of the incident angle. To investigate the validity of this technique, we perform the measurement at different fluences above the single-shot ablation threshold of Si. The experimental results obtained show that wavelength of SPPs excited on the Si gratings change with an increase of the laser fluence, and that change of the near-field distribution in the vicinity of SPPs excited leads to morphological change of ablated surfaces.