抄録
Using a pump-probe technique, we measured the refl ectivity of crystalline silicon to understand dynamic
processes responsible for the periodic surface nanostructure formation with superimposed multiple shots
of low-fl uence femtosecond (fs) laser pulses. The free-electron density and the lattice temperature on
the surface were derived from the observed time-dependent refl ectivity change. The results have shown
that the multiple low-fl uence fs laser pulses are crucial for the nanostructure formation through nonthermal
interaction processes.
