Electronically controlled liquid crystal terahertz polarization manipulation under static magnetic field pre-anchoring

Abstract

In this work, a new strategy was proposed for active control of mm-thick liquid crystals (LC) cell to realize the polarization manipulation in terahertz (THz) regime, which through the electric field control and static magnetic field pre-anchoring. The LC cell was fabricated by a nematic 5CB LC and two silica substrates that were coated with the graphite layer as the transparent electrode. Under the pre-anchoring of the static magnetic field, the optical axis of LC can be precisely controlled by the variable electric field. By using a THz-TDS with a wire grid polarizer, the output THz polarization from the LC cell can be deduced from the amplitude and phase shift of ±45° components. Here, we systematically analyzed three different outfield configurations. Only if the ±45° components that output from the polarizer have phase shifts, can the polarization state conversion be realized. The results show that the linear to circular or the cross-polarization conversion were realized under the specific electric field. This work provides a new approach for the thick-LC layer anchoring and orientation control, and also the tunable polarization manipulation of THz LC devices.