Magnetic induced terahertz modulation characteristics based on ferromagnetic nematic liquid crystals

Qinghao Meng; Xueyan Wang; Boyan Zhang; Siyu Qian; Bo Peng; Hangyu Zhou; Bo Su; Cunlin Zhang

doi:10.1016/j.saa.2022.122232

Magnetic induced terahertz modulation characteristics based on ferromagnetic nematic liquid crystals

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Mar 15:289:122232. doi: 10.1016/j.saa.2022.122232. Epub 2022 Dec 12.

Authors

Qinghao Meng¹, Xueyan Wang², Boyan Zhang¹, Siyu Qian¹, Bo Peng¹, Hangyu Zhou², Bo Su³, Cunlin Zhang¹

Affiliations

¹ Department of Physics, Capital Normal University, Beijing 100048, China; Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Beijing 100048, China; Beijing Advanced Innovation Centre for Imaging Theory and Technology, Beijing 100048, China; Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing 100048, China.
² Department of Physics, Capital Normal University, Beijing 100048, China.
³ Department of Physics, Capital Normal University, Beijing 100048, China; Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Beijing 100048, China; Beijing Advanced Innovation Centre for Imaging Theory and Technology, Beijing 100048, China; Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Beijing 100048, China. Electronic address: subo75@cnu.edu.cn.

PMID: 36525811
DOI: 10.1016/j.saa.2022.122232

Abstract

In recent years, solid state terahertz (THz) modulators have obtained rapid progress with the widespread use of two-dimensional (2D) materials in the field of THz; however, challenges remain in preparing flexible THz modulators. In this study, flexible ferromagnetic nematic materials were prepared by doping thermotropic nematic liquid crystals 5CB into magnetic fluids, and the influence of water was reduced by a self-made cyclic olefin copolymer (COC) microfluidic chip. THz modulation characteristics of magnetic fluid and ferromagnetic nematic liquid crystal (FNLC) under the induction of external magnetic field were compared using a THz time domain spectroscopy system. Under the action of a 91 mT magnetic field, the magnetic fluid has a maximum modulation depth (MD) of 54%. Under the same magnetic field, the maximum MD of the FNLC materials increase to 78% because of the rearrangement of Fe₃O₄ nanoparticles induced by the topological defect of the liquid crystal. We demonstrate that the magneto-optical effect is significantly enhanced in the ferromagnetic nematic liquid crystal hybrid system. This strategy of doping thermotropic nematic liquid crystals to enhance the magneto-optical effect has great potential for THz filtering, modulation, and sensing applications.

Keywords: Magnetic fluid; Microfluidic chip; Terahertz modulation; Thermotropic nematic liquid crystals.