Modeling of laser ponderomotive self-focusing in plasma within the paraxial complex geometrical optics approach. (7th October 2019)

• Record Type: Journal Article
• Authors: Ruocco, A; Duchateau, G; Tikhonchuk, V T; Hüller, S
• Is Part Of: Plasma physics and controlled fusion. Volume 61:Number 11(2019)
• Publication Date: 2019-10-07
• Subjects: laser-plasma interaction -- hydrodynamics codes -- beam self-focusing -- inertial confinement fusion; Plasma (Ionized gases) -- Periodicals; Controlled fusion -- Periodicals; 530.44
• DOI: 10.1088/1361-6587/ab467b
• Languages: English
• ISSNs: 0741-3335

Abstract

Abstract: Laser ponderomotive self-focusing in an underdense homogeneous plasma is studied within the paraxial complex geometrical optics (PCGO) approach implemented in a hydrodynamic code in two-dimensional planar geometry. The self-focusing of a PCGO Gaussian beam is compared to simulations performed with a paraxial electromagnetic code. Good agreement has been found for beam powers less than three times the critical power and for plasma densities 5%–10% of the critical density. Besides Gaussian beams, PCGO allows to reproduce spatially modulated beams by superposition of Gaussian beams, mimicking a speckle pattern. Although the statistics of speckle patterns generated with PCGO reproduces well the speckle statistics of optically smoothed beams, a PCGO speckle is larger than optical speckles, carrying thus higher power such that they overestimate self-focusing effects. To overcome this issue, an algorithm is proposed within PCGO framework: it consists of superposing several Gaussian beams forming a speckle such that self-focusing effects are eventually well controlled. It is found that the superposition of three Gaussian beams with appropriate initial conditions leads to a reduction of the PCGO speckle intensity enhancement.