Generation of intense sub-cycle terahertz pulses with variable elliptical polarization

We demonstrate the generation of intense, sub-cycle terahertz (THz) pulses with variable elliptical polarization and peak fields above 80 kV/cm from large aperture photoconductive antennas using a specific interdigitated structure. The latter is composed of horizontal and vertical electrodes, which allow the generation of two quasi-half-cycle THz pulses with orthogonal polarization. A time delay between the two THz pulses is introduced by a phase delay mask covering only the parts of the antenna with horizontal electrodes. By changing the mask thicknesses, we can control, on demand, the polarization state of the THz pulses from linear polarization through elliptical to circular polarization over a quarter of a THz cycle.