Yoo YJ, Jang D, Kim KY. Highly enhanced terahertz conversion by two-color laser filamentation at low gas pressures.
OPTICS EXPRESS 2019;
27:22663-22673. [PMID:
31510552 DOI:
10.1364/oe.27.022663]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 07/16/2019] [Indexed: 06/10/2023]
Abstract
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.
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