Polarization controlled terahertz time domain spectroscopy using dual-color plasma

Terahertz waves have found many applications, including imaging, security, high-capacity telecommunications, and quality inspections. Moreover, sample characterization using the terahertz time-domain (THz-TDS) gives us information about both amplitude and phase, which is a significant advantage over other conventional spectroscopic methods. Several sources and detectors, such as photoconductive antennas, nonlinear crystals, or photo-Dember sources, can be used for these mentioned applications. However, they are often low-energy, limited by threshold or narrow spectrum. In our experimental setup, we generate the THz field using dual-color plasma. The generation process resides in the mixing of the first and second harmonics providing substantial conversion efficiency, excellent signal-to-noise ratio, and a broad spectrum ranging from 0,1 THz to 4 THz. Furthermore, we enhance our measurement technique by implementing ZnTe polarization-sensitive detection. Here we experimentally demonstrate plasma polarization response. Our multipurpose configuration is employed in various experimental arrangements such as transmission, reflection, or attenuated total reflection (ATR). It offers a complete sample analysis of thickness, dielectric functions, birefringence, and optical activity.