Research on extrinsic optical activity in all-silicon-based terahertz metamaterial

Chiral metamaterials have stronger optical activity than natural materials within the terahertz frequencies, so they have attracted more attention. By arranging special silicon structures at terahertz frequencies, we propose an all-silicon-based extrinsic chirality structure with high outer circular dichroism in this paper. And its circular birefringence is also better than average. The properties of our all-silicon-based metamaterials are generated due to the resonance between the circularly polarized incident wave and the special silicon structure of the surface. The circular dichroism of the device due to transmission can reach 0.54. And we obtained the maximum polarization rotation angle can achieve 50°. In addition, the chirality of the device can be dynamically changed between 0.63THz-0.79THz. Such control can be achieved merely by changing the incident tilt angle. Our research can be applied to terahertz circular polarizer and polarimeter, which has great potential in optical path construction, light detection, signal transmission and processing.