Abstract-Terahertz generation from reduced graphene oxide

Huan Wang, Yixuan Zhou, Zehan Yao, Lipeng Zhu, Yuanyuan Huang, Xinlong Xu, Zhaoyu Ren,

https://www.sciencedirect.com/science/article/pii/S0008622318303609


We firstly investigate the generation of terahertz (THz) wave from reduced graphene oxide(RGO) illuminated with femtosecond near-infrared laser pulse. Experiment results show that the THz generation from RGO can be enhanced by increasing the reduction degree and reducing the film thickness. The former can be attributed to the increase of sp2 carbon region, which has much smaller band gap and graphene-like photoelectric properties. The latter is due to the suppression of the light-induced lateral currents in the surface of RGO layers. The linear dependency of the THz electrical field on the pump power confirms that the THz emission from RGO is governed by second-order nonlinear properties. When exciting laser irradiates from opposite sample sides, π phase shift of the generated THz wave has been observed, suggesting the transient photocurrent related to THz emission is induced by the photon drag effect. The conclusion has been further confirmed by the well fitting of the experiment and theoretical calculation based on the symmetry of RGO. This work makes it clear the THz generation mechanism of RGO and paves a way for developing new THz sources.

Abstract-Temperature Dependent Conductivity of Graphene Oxide and Graphene Oxide-Polyaniline Nanocomposites Studied by Terahertz Time-Domain Spectroscopy

Partha Dutta, Jessica Afalla, Arnab Halder, Sudeshna Datta, and Keisuke Tominaga

http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b10412

In this work, we have studied the temperature-dependent conductivity of graphene oxide (GO) and graphene oxide-polyaniline (GO-PANI) nanocomposites by terahertz time-domain spectroscopy (THz-TDS) from 78 K to 293 K. The refractive index and absorption coefficient are related to the conductivity, and it has been found that in the THz region, the real part of the complex conductivity of GO is less than that of GO-PANI over the entire range of experimental temperatures. Both the systems exhibit an increase in these physical parameters with increasing temperature. The complex conductivity spectra of these systems in the THz region are well fitted by an analytical model that has contributions from the scattering of free electrons (Drude-Smith term) and from bound-electron oscillation (Lorentz term). The fitting analysis suggests a more ordered structure and anharmonicity for both the systems with increasing temperature and reports that GO-PANI has a greater free electron density and damping frequency of oscillation and more ordered structures than GO at all temperatures.

Abstract-Two-Terminal Graphene Oxide Devices for Electrical Modulation of Broadband Terahertz Waves

1. 1. 
      
2. Seungwoo Lee^1,*, 
3. Kyung Eun Lee², 
4. Won Jun Lee², 
5. Byung Cheol Park³, 
6. Byungsoo Kang³, 
7. Euyheon Hwang^4,* and
8. Sang Ouk Kim^2,*

Article first published online: 16 DEC 2015

DOI: 10.1002/adom.201500577

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

http://onlinelibrary.wiley.com/doi/10.1002/adom.201500577/abstract;jsessionid=7B118B09A2FC6E009805CF6701D21B98.f01t03?userIsAuthenticated=false&deniedAccessCustomisedMessage=

Graphene oxide (GO) can provide a generic way to effectively control broadband THz transmission amplitude, when incorporated into two-terminal electrode devices. Electrically trapped charge carriers within localized impurity states (LIS) of GO, which originate from fully randomized defective structure of GO, result in a large modulation of transmission amplitude (≈30%) for broadband THz waves (≈0.3–2.0 THz) even at room temperature.

Abstract-Solution-processable reduced graphene oxide films as broadband terahertz wave impedance matching layers

Yixuan Zhou,   Yiwen E,   Zhaoyu Ren,   Haiming Fan,   Xin Long Xu,  Xinliang Zheng,   Dangyuan Lei,   Weilong Li,   Li Wang and  jintao bai  

J. Mater. Chem. C, 2015, Accepted Manuscript

http://pubs.rsc.org/en/content/articlelanding/2015/tc/c4tc02930e#!divAbstract
DOI: 10.1039/C4TC02930E

The potential of solution-processable reduced graphene oxide (rGO) films as wave impedance matching layers has been examined in a broad terahertz (THz) spectral bandwidth. The THz sheet conductivities of rGO fims measured by THz time-domain spectroscopy were observed to be tunable and sensitive to the film thicknesses and reduction degrees, which can be efficiently controlled by our solution-processable fabrication method. Remarkable broadband impedance matching was achieved with suitable rGO film, showing as the suppression of the internal reflected THz pulses from the substrate in the spectra. The underlying mechanisms have been revealed in both experiment and theory. This work paves the way for developing rGO-based broadband and large-scale anti-reflection layers for THz components.