Transient optical non-linearity in p-Si induced by a few cycle extreme THz field

Andrei Savel'ev; Oleg Chefonov; Andrei Ovchinnikov; Alexey Rubtsov; Alexander Shkurinov; Yiming Zhu; Mikhail Agranat; Vladimir Fortov

doi:10.1364/OE.415354

Transient optical non-linearity in p-Si induced by a few cycle extreme THz field

Opt Express. 2021 Feb 15;29(4):5730-5740. doi: 10.1364/OE.415354.

Authors

Andrei Savel'ev, Oleg Chefonov, Andrei Ovchinnikov, Alexey Rubtsov, Alexander Shkurinov, Yiming Zhu, Mikhail Agranat, Vladimir Fortov

PMID: 33726106
DOI: 10.1364/OE.415354

Abstract

We study the impact of a few cycle extreme terahertz (THz) radiation (the field strength E_THz ∼1-15 MV/cm is well above the DC-field breakdown threshold) on a p-doped Si wafer. Pump-probe measurements of the second harmonic of a weak infrared probe were done at different THz field strengths. The second harmonic yield has an unusual temporal behavior and does not follow the common instantaneous response, ∝ETHz2. These findings were attributed to: (i) the lattice strain by the ponderomotive force of the extreme THz pulse at the maximal THz field strength below 6 MV/cm and (ii) the modulation of the THz field-induced impact ionization rate at the optical probe frequency (due to the modulation of the free carriers' drift kinetic energy from the probe field) at the THz field strength above 6-8 MV/cm.