Abstract-Strong Spatial Confinement of Terahertz Wave inside Femtosecond Laser Filament

Jiayu Zhao, Wei Chu, Zhi Wang, Yan Peng, Cheng Gong, Lie Lin, Yiming Zhu, Weiwei Liu, Ya Cheng, Songlin Zhuang, and Zhizhan Xu

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.6b00512

Publication Date (Web): November 8, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00512

In this paper, a new experimental phenomenon is demonstrated. During the femtosecond laser filamentation, the generated terahertz (THz) pulse has been found to be strongly confined inside the plasma channel, reaching a spatial diameter of a few tens of micrometres. It has been attributed to the formation of a plasma negative dielectric waveguide induced by the transverse inhomogeneous plasma density distribution. The new experimental phenomenon will renew the understanding of the THz wave generation and propagation dynamics during the femtosecond laser and air plasma interaction. Due to this strong spatial confinement, THz electric field strength could be enhanced by orders of magnitude, potentially providing a new approach to perform THz nonlinear optics with low laser energy.

Abstract-Terahertz Wave Guiding by Femtosecond Laser Filament in Air

Jiayu Zhao, Yizhu Zhang, Zhi Wang, Wei Chu, Bin Zeng, Ya Cheng, Zhizhan Xu, Weiwei Liu

http://arxiv-web3.library.cornell.edu/abs/1310.5435

(Submitted on 21 Oct 2013)

Femtosecond laser filament generates strong terahertz (THz) pulse in air. In this paper, THz pulse waveform generated by femtosecond laser filament has been experimentally investigated as a function of the length of the filament. Superluminal propagation of THz pulse has been uncovered, indicating that the filament creates a THz waveguide in air. Numerical simulation has confirmed that the waveguide is formed because of the radially non-uniform refractive index distribution inside the filament. The underlying physical mechanisms and the control techniques of this type THz pulse generation method might be revisited based on our findings. It might also potentially open a new approach for long-distance propagation of THz wave in air.