Generation of Circularly Polarized Strong-Field Terahertz Waves

Terahertz (THz) circular dichroism (TCD) spectroscopy is extensively used to examine the chiral properties of biological macromolecules and other materials. The rapid advancements in strong-field THz generation and field-modulated techniques highlights the importance of advancing tunable strong-field TCD spectroscopy technology. In this study, we designed and implemented an integrated strong-field TCD spectroscopy system. By using a tilted-pulse-front technique, we generated linearly polarized strong-field THz radiation and achieved linear-to-circular polarization conversion via a reflective metasurface. The resulting circularly polarized THz radiation exhibited an ellipticity greater than 0.9 in the frequency range of 0.38-0.61 THz, achieving a linear-to-circular conversion efficiency exceeding 90%. Additionally, the peak electric field strength of the circularly polarized THz radiation exceeded 100 kV/cm. The proposed system is expected to be instrumental in investigating the chiral characteristics of materials under strong field conditions and in examining how these characteristics vary under different field conditions.