Abstract-Enhanced Polarization-sensitive Terahertz Emission from Vertical Grown Graphene by Dynamical Photon drag Effect

Lipeng Zhu,  Yuanyuan Huang,  Zehan Yao,  Baogang Quan,  Longhui Zhang ,  Junjie Li,  changzhi gu,  Xin Long Xu  and  Zhaoyu Ren 

http://pubs.rsc.org/en/content/articlelanding/2017/nr/c7nr02227a#!divAbstract

Improving terahertz (THz) emission from graphene is a challenge for graphene-based THz photonics as graphene demonstrates a weak light-matter interaction. With an unique ultra-black surface structure, vertical grown graphene (VGG) is proposed to enhance the light-matter interaction and further enhance THz emission. Herein, enhanced THz radiation is observed by THz time-domain emission spectroscopy from VGG compared with single-layer graphene. The radiated THz amplitude shows a linear dependence on the pump power, which demonstrates a second order nonlinear effect. Considering the symmetry of VGG on substrate, we can exclude the optical rectification effect and photogalvanic effect (PGE) by the D6h point group with centrosymmetry. Thus we analyze the transient photocurrent related to THz emission only by the photon drag effect (PDE). The polarization-sensitive THz radiation signals are wave-vector reliance and demonstrate cos2φ and sin2φ dependence on the polarization angles of the pump laser. This is consistent with the theoretical analysis of PDE. Our results show the enhanced, ultrafast, broadband THz radiation property of VGG, which paves the way for high performance of THz emitter and THz detector based on graphene materials.