Generation of the second optical harmonic in silicon under the action of terahertz pulse with high electric field strength

The article presents the results of experimental studies on generation of the second optical harmonic of a femtosecond laser pulse with a radiation wavelength of $1240$ nm in a silicon surface layer under the action of terahertz radiation pulses with a maximum electric field strength of up to $23$ MV/cm. It is shown that, in the field range up to $15$ MV/cm, the intensity of the second harmonic is proportional to the dielectric susceptibility $\chi^{(3)}$ and the squared electric field strength of the terahertz pulse.