Abstract-A simple method to enhance terahertz radiation from femtosecond laser filament array with a step phase plate

Jiayu Zhao, Lanjun Guo, Wei Chu, Bin Zeng, Hui Gao, Weiwei Liu, and Ya Chen
https://www.osapublishing.org/ol/upcoming_pdf.cfm?id=236756

• Abstract: In this work, we experimentally demonstrate a 200% enhancement of terahertz (THz) wave amplitude generated by femtosecond laser filamentation in air. The experimental setup simply uses a semicircular phase plate to generate two parallel filaments. Temporally overlapped THz pulses from two filaments coherently add up, giving rise to significant enhancement of the THz pulse amplitude. It has been foreseen that further enhancement would be achieved if the design of phase plates could be optimized to generate filament array. This simple method makes full use of the laser energy and might potentially open a new approach to remotely enhance the THz emission in air.

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.