Analytical modeling and optimization of terahertz time-domain spectroscopy experiments using photoswitches as antennas

From classical charge transport equations and dipole radiation equations, we derive a simple analytical model for the signal detected in terahertz time-domain spectroscopy using photo-conducting antennas. The validity of our model is checked by comparison to published calculated results and to experimental data we have measured. This expression depends mostly on the carrier lifetime in the antennas' semiconductor material and on the laser pulse duration. The analytical form of the detected terahertz (THz) signal allows us to separate the contribution of the different experimental parameters. Together with a detailed noise analysis in THz time-domain spectroscopy, we optimize the parameter values in order to achieve the largest dynamics of measurement.