Propagation of an ultrashort terahertz pulse with a high electric field amplitude in a silicon sample

A computational model is presented for the dynamics of a THz pulse incident on a sample of pure silicon with an electric field amplitude of up to $23$ MV/cm. It is shown that the motion of a two-period THz pulse will be accompanied, as a result of impact ionization, by a sharp increase in the concentration of free carriers up to a level of $\sim~10^{19}$ cm$^{-3}$ on the inlet surface and a slow decrease in depth up to $\sim10^{17}$ cm$^{-3}$ at the exit of the sample. The need to confirm the calculation model by the experimental measurements of the impact ionization rate for the given parameters of the THz pulse is shown.