2016, Choporova, Yulia Yu., Gerasimov, Vasily V., Knyazev, Boris A., Sergeev, Sergey M., Shevchenko, Oleg A., Zhukavin, Roman K., Abrosimov, Nikolay V., Kovalevsky, Konstantin A., Ovchar, Vladimir K., Hübers, Heinz-Wilhelm, Kulipanov, Gennady N., Shastin, Valery N., Schneider, Harald, Vinokurov, Nikolay A.

A single-color pump-probe system has been commissioned at the Novosibirsk free electron laser. The laser emits a tunable monochromatic terahertz radiation. To prove the proper system operation, we investigated the time-resolved absorption of a sample of n-type germanium doped with antimony, which was previously investigated at the FELBE facility, in the temperature range from 5 to 40 K. The measured relaxation time amounted to about 1.7 ns, which agreed with the results obtained at the FELBE. The results of pump-probe measurements of non-equilibrium dynamics of hot electrons in the germanium crystal at cryogenic temperatures are presented for wavelengths of 105, 141 and 150 μm.