Manipulation of polarisations for broadband terahertz waves emitted from laser plasma filaments

Zhang, Zhelin and Chen, Yanping and Cui, Sen and He, Feng and Chen, Min and Zhang, Zhen and Yu, Jin and Chen, Liming and Sheng, Zheng-Ming and Zhang, Jie (2018) Manipulation of polarisations for broadband terahertz waves emitted from laser plasma filaments. Nature Photonics, 12. pp. 554-559. ISSN 1749-4885

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    Abstract

    Polarization control of broadband terahertz waves is essential for applications in many areas such as material sciences, medical and biological diagnostics, near-field communications and public securities. Conventional methods for polarization control are limited to narrow bandwidth and often with low efficiency. Here based upon theoretical and experimental studies, we demonstrate that the two-colour laser scheme in gas plasma can provide effective control of elliptically polarized terahertz waves, including their ellipticity, azimuthal angle, and chirality. This is achieved with a circularly-polarized laser at the fundamental frequency and its linearly polarized second harmonic, a controlled phase difference between these two laser components, as well as a suitable length of the laser plasma filament. A flexible control of their ellipticity and azimuthal angle is demonstrated with our theoretical model and systematic experiments. This offers a unique and flexible technique on the polarization control of broadband terahertz radiation suitable for wide applications.