Abstract-Terahertz beam spot size measurements by a CCD camera

O. V. Chefonov, A. V. Ovchinnikov, M. B. Agranat, and A. N. Stepanov

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-17-4099

We present the experimental data on the direct measurements of spatial distribution of the terahertz (THz) pulse intensity profile using a commercial silicon-based charge-coupled device (CCD) camera in the spectral range from 1–3 THz. A method to measure the dimensions of a high-intensity THz radiation beam in the focal plane using the CCD camera is proposed and experimentally verified.

© 2019 Optical Society of America

Abstract-Nonlinear Transfer of Intense Few Cycle Terahertz Pulse Through Opaque n-doped Si

O. V. Chefonov, A. V. Ovchinnikov, M. B. Agranat, V. E. Fortov, E. S. Efimenko, A. N. Stepanov, A. B. Save'lev

https://arxiv.org/abs/1805.09611

Intense few cycle terahertz pulses exhibit complex non-linear behavior under interaction with heavily n-doped Si. Fast increase in the transmission of a 700 fs pulse (central frequency 1.5 THz) through the Si sample (low field transmission of 0:02 %) saturates at 8 % for the external field of 5 MV/cm and then drops twofold at 20 MV/cm. An electro-optical sampling measurements revealed formation of a single cycle terahertz pulse at this field due to formation of a thin ionized layer by the first intense oscillation of the terahertz field.

Abstract-Two-color laser-plasma generation of terahertz radiation using a frequency-tunable half harmonic of a femtosecond pulse

N. V. Vvedenskii, A. I. Korytin, V. A. Kostin, A. A. Murzanev, A. A. Silaev, and A. N. Stepanov

http://prl.aps.org/accepted/1607aY19Td613941693e0a17dd97742a55922bd90

We investigate for the first time, both experimentally and theoretically, low-frequency terahertz (THz) emission from the ambient air ionized by a two-color femtosecond laser pulse containing, besides the fundamental-frequency main field, a weak additional field tunable near the frequency of the half harmonic. By controlling the mutual polarization and the powers of the main and additional fields, we determine the dependences of the THz power and polarization on the parameters of the two-color pulse. We also discover the resonant-like dependence of the THz~yield on the frequency detuning of the additional field. The analytical formulas obtained using the model of the free-electron residual current density give an excellent agreement with the experimental results.