Abstract
The experimental findings on the second harmonic generation (SHG) in centrosymmetric crystal silicon are reported. The SHG is induced by extremely high electric field (up to 15 MV/cm) parallel to the crystal surface of a short terahertz (THz) pulse while probing by an infrared femtosecond optical pulse. The SHG under such unique conditions is reported for the first time. At the electric field amplitude above 8 MV/cm, the quadratic dependence of the SHG yield integrated over the THz pulse duration on the electric field is violated and SHG yield is not changed with a further increase of the THz field. Saturation of SHG intensity at high electric fields is explained in terms of carrier density increase due to impact ionization and destructive interference of electric-field induced and current induced nonlinear polarizations.
Highlights
Second harmonic generation has been used for many years for studying properties of bulk and thin film materials[1]
In this study for the first time we present the findings on effect of high electric field strength of a THz pulse on bulk second-order susceptibility in silicon by use of second harmonic generation of an infrared femtosecond laser pulse propagating through a wafer
For the first time, the results are reported of experimental studies in a bulk of p-type silicon crystal of a second harmonic generation of a femtosecond chromium-forsterite laser radiation induced by a strong electric field of a THz pulse
Summary
Second harmonic generation has been used for many years for studying properties of bulk and thin film materials[1]. An important issue is the SHG efficiency for detecting high-frequency coherent transient processes caused by electrical and/or magnetic fields of low-cycle THz pulses. Investigation in this direction will enable one to develop new nonlinear optical methods for studying properties of semiconductor materials and nanostructures. Detection of freely propagating THz radiation by use of optical second-harmonic generation in silicon was reported earlier[4]. In this study for the first time we present the findings on effect of high electric field strength of a THz pulse (up to 15 MV/cm) on bulk second-order susceptibility in silicon by use of second harmonic generation of an infrared femtosecond laser pulse propagating through a wafer
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