Large-area photoconductive switches as emitters of terahertz pulses with fully electrically controlled linear polarization

Polarimetric measurements in the terahertz (THz) range have a wide range of applications in material science and physico-chemistry. Usually performed using mechanically controlled elements, such measurements are inherently limited in precision and acquisition rate. Here, we propose and realize an innovative concept of a THz pulse emitter, linearly polarized, which allows electrical continuous control of the polarization direction and modulation ability up to several tens of kHz. It consists in an interdigitated photoconductive switch with an intermixed sickle geometry, where the vertical and horizontal components of the electric field are intermixed at a subwavelength scale. We demonstrate that such an emitter permits control of the direction and amplitude emitted with an excellent degree of polarization up to 4 THz, which is estimated to be experimentally better than 98%. This work opens perspectives for sensitivity improvements in THz polarimetry with lock-in detection schemes.