Article
Optics
Mayuri Nakagawa, Makoto Okano, Shinichi Watanabe
Summary: We report on a system that can measure terahertz electric-field vector waveforms without mechanical moving parts. By combining phase-locked femtosecond lasers and an electro-optic modulator, polarization-sensitive terahertz time-domain spectroscopy measurements can be performed. The system provides a robust platform for both basic science and practical applications.
Article
Multidisciplinary Sciences
Lin Ke, Lei Zhang, Nan Zhang, Qing Yang Steve Wu, Hai Sheng Leong, Ali Abdelaziem, Jodhbir S. Mehta, Yu-Chi Liu
Summary: Terahertz spectroscopy technique is applied to analyze the biomechanical properties of human corneas. The phase changes of terahertz signal are influenced by the effects of pressure, anisotropic deformation, thickness changes, and hydration levels. The correlation between the phase shift and refractive index shift can be used to derive the elastic Young's modulus of the corneas.
SCIENTIFIC REPORTS
(2022)
Article
Chemistry, Multidisciplinary
Zhihui Zeng, Elena Mavrona, Daniel Sacre, Nico Kummer, Jingming Cao, Luca A. E. Mueller, Erwin Hack, Peter Zolliker, Gustav Nystroem
Summary: By utilizing a simple method, the study successfully prepared a biopolymer aerogel with excellent mechanical properties, electrical properties, and low density, which exhibits high birefringence values in the THz regime. The research results suggest that the outstanding electrical and optical properties of the aerogel are influenced by the embedded nanomaterials.
Article
Materials Science, Multidisciplinary
K. Grishunin, E. A. Mashkovich, A. Kimel, A. M. Balbashov, A. K. Zvezdin
Summary: Efficiency of ultrafast spin excitation in antiferromagnetic alpha-Fe2O3 using a nearly single-cycle THz pulse is studied with respect to THz pulse polarization and sample temperature. Above the Morin point, most effective excitation occurs when the magnetic field of the THz pulse is perpendicular to the antiferromagnetically coupled spins. The mechanism of spin excitation above and below the Morin point relies on a magnetic-dipole interaction of the THz magnetic field with spins, where coupling efficiency is proportional to the time derivative of the magnetic field.
Article
Physics, Applied
T. G. H. Blank, K. A. Grishunin, A. V. Kimel
Summary: An intense THz pulse excites a high-Q magnetic resonance mode in the antiferromagnetic insulator HoFeO3 via the THz Zeeman torque. Anomalous beating in the magnon dynamics at certain temperatures is observed, which is attributed to the formation of cavity magnon-polaritons. Simulations using Maxwell's equations support this idea. The observed beating pattern depends on the polarization of the probe pulse and can be explained by considering an imaginary Verdet constant.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Shi-Tong Xu, Fei Fan, Shu Chen, Yanzhao Xing, Yuebo Gao, Huixin Li, Guangcheng Niu, Sheng-Jiang Chang
Summary: This work proposes a new strategy for active control of mm-thick liquid crystals (LC) cell through electric field control and static magnetic field pre-anchoring to realize polarization manipulation in terahertz (THz) regime. The results demonstrate that linear to circular or cross-polarization conversion can be achieved under specific electric fields.
OPTICAL MATERIALS EXPRESS
(2021)
Article
Polymer Science
Alexander T. Clark, Sophia D'Anna, Jessy Nemati, Phillip Barden, Ian Gatley, John Federici
Summary: Using terahertz nondestructive evaluation, stress maps for polymeric materials can be obtained by analyzing the cross-polarized terahertz pulses. By using amber as a sample material, it is found that amber behaves as a classic uniaxial birefringent material, with stress directions consistent with visible photoelasticity measurements. Additionally, the method allows for the visualization of stress levels within the amber matrix and localized stress regions surrounding inclusions.
Article
Optics
Yunyun Ji, Xinhao Jiang, Fei Fan, Huijun Zhao, Jierong Cheng, Xianghui Wang, Shengjiang Chang
Summary: Researchers demonstrate an active terahertz beam deflection device based on polarization mode conversion, using phase-gradient metasurfaces and tunable liquid crystal materials. The device achieves beam deflection of 47.5° with ultrahigh modulation depth of 99.6% in one mode, and 32.5° deflection with a modulation depth of 97.8% in another mode. This work provides a new approach for wavefront manipulation and active modulation of terahertz waves.
Article
Optics
Yunyun Ji, Xinhao Jiang, Fei Fan, Huijun Zhao, Jierong Cheng, Xianghui Wang, Shengjiang Chang
Summary: This study demonstrates an active THz beam deflection device based on polarization mode conversion by integrating phase-gradient metasurfaces and tunable liquid crystal materials. The resonant modes in the photonic cavity formed by the double-layer metasurface and tunable anisotropic liquid crystal material actively regulate the resonance matching conditions, enabling beam deflection and modulation. This work provides a new approach for wavefront manipulation and active modulation of THz waves using liquid crystal photonic devices.
Article
Materials Science, Multidisciplinary
Rahul Godiwal, Subhash Nimanpure, Guruvandra Singh, Amit Kumar Gangwar, Ajay Kumar Verma, Dibakar Roychowdhury, Preetam Singh, Mukesh Jewariya
Summary: In this study, nanocrystalline ZnO thin films were experimentally characterized using terahertz time-domain spectroscopy. Birefringence was observed at different substrate temperatures, indicating the presence of crystallinity in the films. The absorption behavior of ZnO films suggests their potential use in future THz photonics devices.
Article
Optics
Zixuan Du, Qiang Ling
Summary: A highly birefringent microstructure fiber for terahertz waveguiding has been proposed, consisting of a suspended core with a split-ring structure. The fiber's properties such as effective refractive index, birefringence, and relative absorption loss were investigated using the finite element method, with three key parameters optimized for optimal performance. The study also explored the impact of the shape of the split-ring gap on birefringence and absorption loss, achieving high birefringence up to the order of 10-2 and demonstrating great commercial potential.
Article
Materials Science, Multidisciplinary
Zihan Liu, Jialin Wen, Liang Zhang, Zhengyong Zhou, Yuming Dong, Tianyu Yang
Summary: This paper introduces a low-loss, high birefringence anti-resonant fiber structure that maintains a birefringence above the 10-3 level over a wide frequency band. It has minimum loss and bend radius and good manufacturing error tolerance. Additionally, three methods for introducing high birefringence into low-loss ARFs are proposed and verified, contributing to the development of more efficient and reliable THz transmission systems.
RESULTS IN PHYSICS
(2023)
Article
Materials Science, Characterization & Testing
Min Zhai, Esam T. Ahmed Mohamed, Alexandre Locquet, G. Schneider, R. Kalmar, M. Fendler, N. F. Declercq, D. S. Citrin
Summary: The study conducted nondestructive investigation of injection-mold weld lines in an ABS thermoplastic electrical receptacle plate using terahertz techniques and surface acoustic microscopy. The results showed that terahertz techniques can reveal the molecular orientation and stress near the weld lines, while surface acoustic microscopy can demonstrate the abnormal mechanical properties at the weld lines.
NDT & E INTERNATIONAL
(2021)
Article
Optics
Ryota Ito, Hayato Sekiya, Iwao Kawayama, Michinori Honma, Masayoshi Tonouchi, Toshiaki Nose
Summary: Polarization control plays a crucial role in terahertz imaging, and liquid crystals have the potential to achieve tunable polarization control. This study fabricates a twisted nematic (TN) cell using a hydrogen-bonded liquid crystal and discusses the influence of dichroism in the terahertz region. The experimental results show that the polarization state in the Gooch-Tarry minimum condition is affected by the dichroism of the liquid crystal, and a nondichroic liquid crystal is required for complete linearly polarized output. The output intensity of the dichroic liquid crystal-TN cell changes with electrical switching or rotation of the incident terahertz wave polarization direction by 90 degrees, but these intensity variations disappear when using the nondichroic hydrogen-bonded liquid crystal.
Article
Optics
Esam A. A. Hagras, Mohamed Farhat O. Hameed, S. S. A. Obayya
Summary: A compact terahertz dual core photonic crystal fiber polarization splitter is presented, which utilizes a nematic liquid crystal (NLC) of type E7 to achieve high birefringence. The design uses TOPAS as the background material and investigates the impact of geometric parameters and the temperature dependence of the NLC on the splitter's performance. The numerical results show a device length of 3.848 cm with low crosstalk and a large bandwidth of 58 GHz. The design is less sensitive to fabrication perturbations and has potential for THz applications.
