A theoretical model of high-harmonic generation from two-color relativistic circularly polarized laser pulse interacting
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A theoretical model of high‑harmonic generation from two‑color relativistic circularly polarized laser pulse interacting with over‑dense plasmas Duan Xie1 · Yan Yin2 · Hong‑bin Zhuo3 Received: 17 October 2019 / Accepted: 4 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this article, we set up a theoretical model to investigate the physical mechanism of circularly polarized (CP) high-harmonic generation (HHG) by two-color relativistic driving lasers (with one at fundamental and the other at second harmonic). The compression effect of the electron density profile and the boundary oscillating are responsible for the harmonic emission. Based on this model, the scaling law between the intensity of the 4th harmonic and that of the fundamental driving laser can be successfully acquired. Our theoretical model holds only when the second-harmonic laser is much weaker than the fundamental laser. For more general cases, particle-in-cell (PIC) simulations are performed to demonstrate that the HHG efficiency. The intensity of higher order harmonics can be effectively tuned by gradually enhancing the intensity of the second-harmonic driving laser.
1 Introduction CP-HHG from relativistic laser-plasma interaction can provide a kind of intense, short-wavelength, chiral radiation source, which is suitable for the ultrafast detection technology of chiral materials (including bio-molecules, magnetic materials, topological insulators, etc.). As a result, such source owns broad application prospect in bio-medicine, condensed matter physics, material science and so on [1–7]. The main mechanism of plasma-based harmonic generation in relativistic regime is known as the relativistically oscillating mirror (ROM) and coherent synchrotron emission (CSE) model [8–19]. Comparing with CSE model, ROM is more robust and commonly used, which can be described as Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00340-020-07457-w) contains supplementary material, which is available to authorized users. * Hong‑bin Zhuo [email protected] 1
College of Physics and Electronic Information Engineering, Neijiang Normal College, Neijiang 641112, China
2
College of Art and Science, National University of Defense Technology, Changsha 410073, China
3
Center for Advanced Material Diagnostic Technology, Shenzhen Technology University, Shenzhen 518118, China
follows: when a sufficiently intense femtosecond pulse interacts with an over-dense plasma, the ponderomotive force of the incident pulse combined with the electrostatic force from ions drive the surface electrons oscillating relativistically. Then, the reflected electromagnetic pulse contains high-order harmonics resulted from the extreme Doppler shift. However, it has long been believed that ROM is invalid for CP-HHG, because the ponderomotive force of a single CP laser lacks oscillating components. Fortunately, if twocolor counter-rotating CP lasers are used, the condition will be totally different. Be
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