Circularly polarized light can present more optical properties of chiral materials and is widely used to analyze and detect biomolecules. In this paper, a dual-frequency terahertz circular polarization detection structure, which is based on multilayer metamaterials, is proposed. The proposed structure consists of a dual-frequency quarter-wave plate, a polyimide spacer, and a filter. The simulation results show that the structure can distinguish the handedness of circularly polarized light by filtering. The extinction ratios are 4 dB and 5.26 dB at 0.952 THz and 1.03 THz, respectively, and the maximum transmittance efficiency reaches 40%. Given the advantages of easy integration and dual-frequency operation, our design is bound to facilitate the development of multi-frequency detection in biomedical imaging devices.

Measuring the polarization state of light is an inherent problem, especially for the detection of circularly polarized light. We propose a metasurface structure based on graphene to investigate the circular polarization detection function in the THz regime by using the finite difference time domain (FDTD) method. The proposed graphene metasurface consists of a layer of graphene arrays, a polymer dielectric spacer, and a layer of graphene bands. By adjusting the Fermi energy, the structure can realize tunable polarization detection functions. On this basis, we combine tunable filters with different angles into the structure to achieve full Stokes parameter measurement. The simulation results show that the structure's working band can be tuned in the range of 25.88 μm-28.68 μm. The structure we designed helps to develop a tunable and integrated polarization detection method.

Polarization detection is an important part of many polarization applications such as polarization imaging, wireless communication, and circular dichroism spectroscopy. In this paper, two polarization-dependent terahertz wave absorption and transmission metasurface for linearly and circularly polarized light are proposed and proved by numerical simulations. Polarization filtering and polarization absorption are integrated on a single cell, and the orthogonal polarization component is transmitted and absorbed, respectively. The linearly polarization-dependent transmission and absorption structure can obtain a transmission extinction ratio of 11.5 dB and an absorption extinction ratio of over 270 dB at 3 THz. Moreover, the circularly polarization-dependent structure can obtain a transmission extinction ratio of 8.1 dB and an absorption extinction ratio of 4.66 dB at 2.8 THz. Our design facilitates the acquisition of full Stokes parameters and the high-resolution imaging.