Abstract-Tunable terahertz phase shifter based on dielectric artificial birefringence grating filled with polymer dispersed liquid crystal

Xin Zhang, Fei Fan, Chun-Yue Zhang, Yun-Yun Ji, Xiang-Hui Wang, and Sheng-Jiang Chang

Schematic diagram in the experiment and experimental data. (a) The structure of the dielectric gradient grating filled with PDLCs in the experiment; (b) The schematic diagram of geometry configuration in the measurement; (c) The time domain signals of + 45° and -45° LP components at 0 V and (d) 80 V measured by THz-TDS system, respectively.

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-10-2-282

An active terahertz (THz) anisotropic manipulation is based on a structure combined polymer dispersed liquid crystal (PDLC) with sub-wavelength dielectric gradient grating. In this structure, the PDLC works as an adjustable anisotropic material due to the change of the optical axis direction induced by applying a biased electric field, while the dielectric grating serves as an artificial high birefringence material. By using an appropriate design, the THz birefringence of this structure can be enhanced or offset under different biased voltages, and the phase shift curve of this structure becomes flatter than that of the pure PDLC cell due to the dispersion manipulation of the grating. Moreover, the experimental results fit with the simulative designing, demonstrating that the phase shift of the structure can vary from π to 0 near 0.8 THz when the electric field increases from 0 to 80V, and this device realizes the function of polarization conversion as a tunable THz half-wave plate. This work exhibits potential applications in THz functional devices, such as actively controlled phase shifters and polarization convertors combined LC with artificial microstructure.

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