Xi Fugang, Yang He, Khayrudinov Vladislav, He Yuhang, Haggren Tuomas, Zhou Yixuan, Lipsanen Harri, Sun Zhipei, Xu Xinlong
Shaanxi Joint Lab of Graphene, State Key Laboratory of Photoelectric Technology and Functional Materials, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon-Technology, School of Physics, Northwest University, Xi'an 710127, People's Republic of China.
School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, People's Republic of China.
Nanotechnology. 2021 Dec 3;33(8). doi: 10.1088/1361-6528/ac3948.
The development of powerful terahertz (THz) emitters is the cornerstone for future THz applications, such as communication, medical biology, non-destructive inspection, and scientific research. Here, we report the THz emission properties and mechanisms of mushroom-shaped InAs nanowire (NW) network using linearly polarized laser excitation. By investigating the dependence of THz signal to the incidence pump light properties (e.g. incident angle, direction, fluence, and polarization angle), we conclude that the THz wave emission from the InAs NW network is induced by the combination of linear and nonlinear optical effects. The former is a transient photocurrent accelerated by the photo-Dember field, while the latter is related to the resonant optical rectification effect. Moreover, the-polarized THz wave emission component is governed by the linear optical effect with a proportion of ∼85% and the nonlinear optical effect of ∼15%. In comparison, the-polarized THz wave emission component is mainly decided by the nonlinear optical effect. The THz emission is speculated to be enhanced by the localized surface plasmon resonance absorption of the In droplets on top of the NWs. This work verifies the nonlinear optical mechanism in the THz generation of semiconductor NWs and provides an enlightening reference for the structural design of powerful and flexible THz surface and interface emitters in transmission geometry.
强大的太赫兹（THz）发射器的发展是未来太赫兹应用的基石，如通信、医学生物学、无损检测和科学研究。在此，我们报道了使用线偏振激光激发的蘑菇形砷化铟纳米线（NW）网络的太赫兹发射特性和机制。通过研究太赫兹信号对入射泵浦光特性（如入射角、方向、通量和偏振角）的依赖性，我们得出结论，砷化铟NW网络的太赫兹波发射是由线性和非线性光学效应共同诱导的。前者是由光德姆伯场加速的瞬态光电流，而后者与共振光学整流效应有关。此外，偏振太赫兹波发射分量由线性光学效应主导，占比约85%，非线性光学效应占比约15%。相比之下，偏振太赫兹波发射分量主要由非线性光学效应决定。推测太赫兹发射通过NW顶部铟液滴的局域表面等离子体共振吸收而增强。这项工作验证了半导体NW太赫兹产生中的非线性光学机制，并为透射几何结构中强大且灵活的太赫兹表面和界面发射器的结构设计提供了启发性参考。
