Frequency tunable circular polarization control of terahertz radiation

We report on frequency tunable circular polarization control of THz radiation. The technique is based on the relative phase control of two THz pulses that are generated from optical rectification of ultrashort optical pulses in a ZnTe crystal. By changing the temporal separation of the optical pump pulses, continuous control of circular polarization from right to left is achieved in the frequency range from 0.3 to 2.5 THz. The developed scheme shows a potential application for sensitive detection of circular dichroism in the far-infrared regime.