Accessing Terahertz Complex Conductivity Dynamics in the Time-Domain

Time-resolved terahertz (THz) spectroscopy is frequently utilized to measure conductivity dynamics on ultrafast time scales. Typically photo-induced changes in the transmission of the peak of the THz waveform are recorded and thought to represent the real conductivity dynamics. Here we evaluate a time-domain scheme that accesses both the real and imaginary conductivity dynamics by recording the photo-induced change in the transmitted THz pulse at its peak and its zero-crossing, respectively. The applicability and limitations of this method are investigated by modeling the THz response of material systems with known conductivity dynamics. The relationship between measured time-domain dynamics and the actual charge carrier dynamics is discussed.