Abstract-Excellent Terahertz shielding performance of ultrathin flexible Cu/graphene nanolayered composites with high stability

Shengyue Hou, Wenle Ma, Guanghao Li, Yi Zhang  Yunyun Jim Fei Fan, Yi Huang,


https://www.sciencedirect.com/science/article/abs/pii/S1005030220303029

Electromagnetic interference (EMI) shielding at Terahertz (THz) frequency range attracts increasing attention due to the rapid development of THz science and technologies. EMI shielding materials with small thickness, high shielding effectiveness (SE), good flexibility and stability are highly desirable. Herein, an ultrathin flexible copper/graphene (Cu/Gr) nanolayered composite are prepared, which can reach the average EMI SE of 60.95 dB at 0.1-1.0 THz with a thickness of only 160 nm, indicating that more than 99.9999% of the THz wave power can be shielded. Furthermore, the Cu/Gr nanolayered composite also exhibits excellent oxidation resistance, with a 93.09% maintenance rate for EMI SE value after heating at 120 °C for 3 h in air, far higher than that of the bare Cu film (62.15%). Besides, the Cu/Gr nanolayered composite exhibits good mechanical flexibility and flexural fatigue resistance. The EMI SE value of the Cu/Gr nanolayered composite shows a maintenance rate of 98.87% even after 1500 times bending cycles, obviously higher than that of multilayer Cu film (93.07%). These results demonstrate that the ultrathin flexible Cu/Gr nanolayered composites with excellent shielding performance and good stability have a broad application prospect in THz shielding for wearable devices and next generation mobile communication equipment.

Abstract-Application of Terahertz Spectroscopy and Imaging in the Diagnosis of Prostate Cancer

Ping Zhang, Shuncong Zhong, Junxi Zhang, Jian Ding, Zhenxiang Liu, Yi Huang, Ning Zhou, Walter Nsengiyumva, and Tianfu Zhang

https://www.osapublishing.org/copp/abstract.cfm?uri=copp-4-1-31

The feasibility of the application of terahertz electromagnetic waves in the diagnosis of prostate cancer was examined. Four samples of incomplete cancerous prostatic paraffin-embedded tissues were examined using terahertz spectral imaging (TPI) system and the results obtained by comparing the absorption coefficient and refractive index of prostate tumor, normal prostate tissue and smooth muscle from one of the paraffin tissue masses examined were reported. Three hundred and sixty cases of absorption coefficients from one of the paraffin tissues examined were used as raw data to classify these three tissues using the Principal Component Analysis (PCA) and Least Squares Support Vector Machine (LS-SVM). An excellent classification with an accuracy of 92.22% in the prediction set was achieved. Using the distribution information of THz reflection signal intensity from sample surface and absorption coefficient of the sample, an attempt was made to use the TPI system to identify the boundaries of the different tissues involved (prostate tumors, normal and smooth muscles). The location of three identified regions in the terahertz images (frequency domain slice absorption coefficient imaging, 1.2 THz) were compared with those obtained from the histopathologic examination. The tissue tumor region had a distinctively visible color and could well be distinguished from other tissue regions in terahertz images. Results indicate that a THz spectroscopy imaging system can be efficiently used in conjunction with the proposed advanced computer-based mathematical analysis method to identify tumor regions in the paraffin tissue mass of prostate cancer.

Abstract-Active Terahertz Shielding and Absorption Based on Graphene Foam Modulated by Electric and Optical Field Excitation

Shi‐Tong Xu, Fei Fan, Jierong Cheng,  Honghui Chen, Wenle Ma, Yi Huang, Shengjiang Chang,

https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201900555

Ultralight materials for broadband terahertz (THz) shielding and absorption are promising in practical THz applications. Here, active THz shielding and absorption properties of 3D graphene foam (GF) controlled by both laser pumping and biased electric field are investigated. The GF can be tuned from OFF‐shielding state to ON‐shielding state when the external field excitations are applied, and 10 dB shielding bandwidth expands from 0 to a broad band of 0.2–1.6 THz. Further researches show that the GF always keeps very low THz reflection either with or without external fields, but its absorption characteristics can be remarkably controlled from 13% to 95.4% at 0.3 THz by the power of the external excitations, and its specific average terahertz absorption performance increases from 3.9 × 103 to 1.95 × 104 dB cm3 g−1. This modulation mechanism reveals that the carrier density in GF increases one order of magnitude from 2.6 × 1014 cm−3 to 3.15 × 1015 cm−3. Finally, the tunable THz shielding and absorption characteristics of this GF device are demonstrated by THz transmission imaging, which shows its great potential applications in active THz imaging, radar, and electromagnetic compatibility.

Abstract-Annealing temperature dependent terahertz-thermal-electrical conversion characteristics of three-dimensional microporous graphene

Meng Chen, Yingxin Wang, Jianguo Wen, Honghui Chen, Wenle Ma, Fei Fan, Yi Huang, and Ziran Zhao

https://pubs.acs.org/doi/10.1021/acsami.8b20095


Three-dimensional microporous graphene (3DMG), possesses ultrahigh photon absorptivity and excellent photothermal conversion ability, and shows great potential in energy storage and photodetection, especially for the not well-explored terahertz (THz) frequency range. Here, we report on the characterization of THz-thermal-electrical conversion properties of 3DMG with different annealing treatments. We observe distinct behavior of bolometric and photothermoelectric responses varying with annealing temperature. Resistance-temperature characteristics and thermoelectric power measurements reveal that marked charge carrier reversal occurs in 3DMG as the annealing temperature changes between 600 and 800 °C, which can be well explained by Fermi-level tuning associated with oxygen functional group evolution. Benefiting from the large specific surface area of 3DMG, it has an extraordinary capability of reaching thermal equilibrium quickly and exhibits a fast photothermal conversion with a time constant of 23 ms. In addition, 3DMG can serve as an ideal absorber to improve the sensitivity of THz detectors and we demonstrate that the responsivity of a carbon nanotube device could be enhanced by 12 times through 3DMG. Our work provides new insight into the physical characteristics of carrier transport and THz-thermal-electrical conversion in 3DMG controlled by annealing temperature and opens an avenue for the development of highly efficient graphene-based THz devices.

Abstract-Terahertz phase jumps for ultra-sensitive graphene plasmon sensing

Yi Huang,  Shuncong Zhong,  Yaochun Shen, Yingjie Yu, Daxiang Cui,

https://pubs.rsc.org/en/Content/ArticleLanding/2018/NR/C8NR08672A?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FNR+%28RSC+-+Nanoscale+latest+articles%29#!divAbstract

The phase behavior of the reflected terahertz radiation (THz) under surface plasmon resonance (SPR) supported by doped graphene has been comprehensively investigated. For a TM–polarized wave, the dependence of the phase on the angle of incidence has a region with an abrupt jump–like change. We found in particular that the resonance phase dependence would change from step–like contour to Fano lineshape when the system passed through the optimum SPR conditions (i.e., R = 0) in terahertz regime. Monitoring the transformation could provide ultrahigh–sensitive label–free detection of biomolecules. Importantly, the characteristic of phase jumps as a readout response to achieve refractive index sensing that outperforms traditional terahertz–amplitude based attenuated total reflection (ATR) spectroscopy. The results demonstrated a high figure of merit (FOM) of up to 171 based on the terahertz phase information. Moreover, the sensing range could be tuned by changing the surface conductivity of graphene via high doping levels or with few–layer graphene. These terahertz phase response characteristics of graphene plasmon are promising for tunable ultra–sensitivity (bio)chemical sensing applications.

Abstract-Tunable terahertz plasmonics sensor using doped graphene

Yi Huang,  Shuncong Zhong,

http://ieeexplore.ieee.org/document/8068489/

Graphene plasmons exhibit much larger confinement and relatively long propagation distances at terahertz (THz) regime, with the advantage of being highly tunable via electrical and chemical doping. Thus, it provide a suitable alternative to noble-metal plasmons. We investigated the Otto configuration based THz-plasmonics sensor using a continuous suspended monolayer graphene (MLG) and graphene/insulator stacks (GIS) by finite element method (FEM). We revealed that a continuous suspended MLG based sensor has extremely high detection accuracy and promising prospect of application in ultrasensitive THz-plasmonics gas sensing. In addition, more layers of graphene will result in higher detection accuracy, but lower sensitivity and FOM of the sensor using GIS.

Abstract-Ultra-Broadband Wide-Angle Terahertz Absorption Properties of 3D Graphene Foam

Zhen Ge, Ying Zhou, Yang Yang, Peishuang Xiao, Jiajie Liang, Tengfei Zhang, Qian Shi, Guanghao Li, Yongsheng Chen,

http://onlinelibrary.wiley.com/doi/10.1002/adfm.201704363/abstract

As a next generation of detection technology, terahertz technology is very promising. In this work, a highly efficient terahertz wave absorber based on 3D graphene foam (3DG) is first reported. Excellent terahertz absorption property at frequency ranging from 0.1 to 1.2 THz is obtained owing to faint surface reflection and enormous internal absorption. By precise control of the constant properties for 3DG, the reflection loss (RL) value of 19 dB is acquired and the qualified frequency bandwidth (with RL value over 10 dB) covers 95% of the entire measured bandwidth at normal incidence, which far surpasses most reported materials. More importantly, the terahertz absorption performance of 3DG enhances obviously with increasing the incidence while majority of materials become invalid at oblique incidence, instead. At the incidence of 45°, the maximum RL value increases 50% from 19 to 28.6 dB and the qualified frequency bandwidth covers 100% of the measured bandwidth. After considering all core indicators involving density, qualified bandwidth, and RL values, the specific average terahertz absorption (SATA) property is investigated. The SATA value of 3DG is over 3000 times higher than those of other materials in open literatures.

Abstract-Spinning disk as a spatial light modulator for rapid infrared imaging

Zijian Zhang,  Lin Liu,  Aznida Abu Bakar Sajak,  Lu Gan,   Yi Huang,  Yaochun Shen

http://ieeexplore.ieee.org/document/7876596/

A novel spinning disk approach is reported, to achieve video-rate compressive imaging at infrared (IR) and terahertz (THz) frequencies. It uses a 200-mm-diameter circular stainless steel disk with a number of chemically etched 2-mm-diameter holes as a spatial light modulator (SLM). The authors demonstrate that this mechanical SLM is well suited for imaging at both optical and THz frequencies since the stainless steel is opaque to all optical and electromagnetic radiations while the holes are totally transparent. Using a single pair of IR emitter and receiver, the authors demonstrate that the system is capable of capturing a 96 × 96 video sequence at 10 frames/s. The achieved spatial resolution is better than 2 mm using the spinning disk where the diameter of the holes is 2 mm. The authors also present a key-frame extraction method based on this SLM disk, which allows us to capture the shape of a sample even when its size is larger than the effective imaging area of the system.