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-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 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-Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion

• Yixuan Zhou
• , Yiwen E.
• , Xinlong Xu
• , Weilong Li
• , Huan Wang
• , Lipeng Zhu
• , Jintao Bai
• , Zhaoyu Ren
•  & Li Wang

http://www.nature.com/articles/srep38515

Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.