Open AccessHighly enhanced terahertz conversion by two-color laser filamentation at low gas pressures
Author(s) -
Young Joon Yoo,
Dogeun Jang,
Ki-Yong Kim
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.022663
Subject(s) - filamentation , terahertz radiation , optics , femtosecond , laser , materials science , terahertz spectroscopy and technology , brightness , far infrared laser , plasma , energy conversion efficiency , argon , physics , optoelectronics , atomic physics , quantum mechanics
We present an experimental study on pressure-dependent terahertz generation from two-color femtosecond laser filamentation in various gases. Contrary to short-focusing geometry, we find that long filamentation yields higher terahertz energy at lower gas pressures in most gases. This counter-intuitive phenomenon occurs due to multiple peculiar properties associated with filamentation. In practice, filamentation in low-pressure argon provides a maximum laser-to-terahertz conversion efficiency of 0.1%, about 10 times higher than in atmospheric air. In addition, our pressure-dependent study reveals an anticorrelation between terahertz output energy and local plasma fluorescence brightness. This determines the absolute phase difference between two-color laser fields for maximal terahertz generation, as well as verifies the microscopic mechanism of terahertz generation in two-color laser mixing.