Abstract-Terahertz transmission of square-particle and rod structured TbFeO3 metamaterials

Xinxi Zeng, Guanqiao Zhang, Xiaoqing Xi,Bo Li, Ji Zhoub,


https://www.sciencedirect.com/science/article/pii/S0167577X18313855

We investigated terahertz (THz) transmission of square-particle and rod structured TbFeO3 metamaterials. Mie-type resonances were excited in TbFeO3-based metamaterials. And their dependence on shape and orientation angle was studied. Dielectric TbFeO3 ceramic wafers, which were prepared by 3-D direct writing technology and traditional solid-state sintering method, were processed into square-particle and rod structured metamaterials using laser beam machining. With variation of orientation angle, square-particle structured metamaterial showed angle-independence, while rod structured metamaterial showed complicated behaviors: angle-dependence at lower frequencies and angle-independence at higher frequencies. Circular magnetic and electric field distributions surrounding the incident electromagnetic fields endowed resonances insensitivity to orientation angle. And angle-dependence of rod-shaped metamaterial at lower frequencies were caused by the central symmetry breaking.

Abstract-3D direct writing of terahertz metamaterials based on TbFeO3 dielectric ceramics

Applied Physics Letters

Xinxi Zeng, Rong Wang, Xiaoqing Xi, Bo Li,  Ji Zhou

https://aip.scitation.org/doi/abs/10.1063/1.5035123

The integration of terahertz waves with metamaterials has become a key goal in modern photonics. In this work, we designed grating-structured metamaterials and face-centered-cubic (fcc) metamaterials based on TbFeO3 dielectric ceramics and built these materials using 3D direct writing technology. To simulate the behavior of the designed TbFeO3 metamaterials, the dielectric constant of TbFeO3 dielectric ceramic materials was determined. The desired strong electric and magnetic resonances were excited in the designed TbFeO3 metamaterials. The grating-structured metamaterials showed increased polarization-dependent transmittance as the line spacing decreased, while the fcc metamaterial showed a deep transmission dip at low frequencies and an electromagnetically induced increase in transmittance at higher frequencies. An increase in the electrical resistance contributed to the increase in the transmission properties of the fcc TbFeO3 metamaterial as its temperature decreased, while a reduction in the dielectric constant of TbFeO3 simultaneously caused a blueshift in this metamaterial. When combined with 3D direct writing technology, TbFeO3, with its high dielectric constant and low loss characteristics, represents an inexpensive and promising step towards the production of the next generation of low-cost, easy-to-fabricate, all-dielectric metamaterials.

Abstract-Dielectric meta-atom with tunable resonant frequency temperature coefficient

• Lingling Wu, 
• Xiaoqing Xi, 
• Bo Li & 
• Ji Zhou

https://www.nature.com/articles/s41598-017-02974-9

In this paper, we present a proof-of-concept of a new approach to achieving tailored resonant frequency temperature coefficients in dielectric meta-atoms. The technique involves introducing a thermally expanding or contracting material joining the active high permittivity dielectric absorbers. Both simulation and experiment show that by careful design of the element size and appropriate choice of thermomechanical intermediate layer material, increased or decreased resonant frequency shift temperature sensitivity is possible. Once the active dielectric material is chosen, and a meta-atom design determined, we show the resonant frequency shift depends on the thermal expansion coefficient of the intermediate layer. This work demonstrates the feasibility of manipulating the blue or red shift of metamaterial devices by introducing temperature responsive intermediate layers into meta-atoms.Furthermore, this method could also be applied in the Terahertz, infrared or even optical frequencies on scaled meta-atoms.

Abstract-Molecular Rotation-Vibration Dynamics of Low-Symmetric Hydrate Crystal in the Terahertz Region

Xiaojian Fu , Hongya Wu , Xiaoqing Xi , and Ji  Zhou

J. Phys. Chem. A, Just Accepted Manuscript

DOI: 10.1021/jp411609t

Publication Date (Web): December 22, 2013

Copyright © 2013 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/jp411609t?journalCode=jpcafh

The rotational and vibrational dynamics of molecules in copper sulfate pentahydrate crystal are investigated with terahertz dielectric spectra. It is shown that the relaxation-like dielectric dispersion in the low frequency region is related to the reorientation of water molecules under the driving of terahertz electric field, whereas the resonant dispersion can be ascribed to lattice vibration. It is also found that, due to the hydrogen-bond effect, the vibrational mode at about 1.83 THz along [-111] direction softens with decreasing temperature, that is, the crystal expands in this direction when cooled. On the contrary, the mode hardens in the direction perpendicular to [-111] during the cooling process. This contributes to the further understanding of the molecular structure and bonding features of hydrate crystals.