Abstract-Spectral interference of terahertz pulses from two laser filaments in air

Yanping Chen^1,2,a), Zhelin Zhang^1,2, Zhen Zhang^1,2, Xiaohui Yuan^1,2, Feng Liu^1,2, Min Chen^1,2, Jianqiu Xu^1,2, Jin Yu^1,3, Zhengming Sheng^1,2,4,b) and Jie Zhang^1,2
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a) Electronic mail: yanping.chen@sjtu.edu.cn
b) Electronic mail: zmsheng@sjtu.edu.cn
Appl. Phys. Lett. 106, 221105 (2015); http://dx.doi.org/10.1063/1.4922143

Spectral interference is experimentally demonstrated by two terahertz pulses emitting from filaments induced by two successive femtosecond laser pulses in air. Here, a leading pulse is set to be weaker than a trailing pulse and their temporal separation is larger than the pulse duration of the terahertz pulses. When the leading pulse is stronger than the trailing pulse, thefrequency modulation within the whole terahertz envelope is greatly deteriorated due tononlinear effects applying on the trailing pulse through the plasmas generated by the leading pulses. Such unique terahertz spectrum may find applications in terahertz spectroscopy.

Abstract-Dual-frequency terahertz emission from splitting filaments induced by lens tilting in air

Zhelin Zhang¹, Yanping Chen^1,a), Liu Yang¹, Xiaohui Yuan¹, Feng Liu¹, Min Chen¹, Jianqiu Xu¹, Zhengming Sheng^1,2 and Jie Zhang¹
http://scitation.aip.org/content/aip/journal/apl/105/10/10.1063/1.4895720
1 Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
2 Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, United Kingdom
a) Author to whom correspondence should be addressed. Electronic mail: yanping.chen@sjtu.edu.cn
Appl. Phys. Lett. 105, 101110 (2014); http://dx.doi.org/10.1063/1.4895720

Dual-frequency terahertz radiation from air-plasma filaments produced with two-color lasers in air has been demonstrated experimentally. When a focusing lens is tilted for a few degrees, it is shown that the laser filament evolves from a single one to two sub-filaments. Two independent terahertz sources emitted from the sub-filaments with different frequencies and polarizations are identified, where the frequency of terahertz waves from the trailing sub-filament is higher than that from the leading sub-filament.