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25LM-O-16
Peculiarities of Interaction of Radially and Azimuthally Polarized Laser Pulses with Transparent Dielectrics
V.P. Zhukov1'2, N.M. Bulgakova1, M.P. Fedoruk2'3
1-HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnici 828, 25241 Dolni
Brezany, Czech Republic
2- Federal Research Center for Information and Computational Technologies, 6 Lavrentyev Ave., 630090
Novosibirsk, Russia 3- Novosibirsk State University, 2 Pirogova str., 630090, Novosibirsk, Russia
Email address: zukov@ict.nsc.ru
Spatially and/or temporally shaped laser pulses attract a high interest as a promising technique foi improving efficiency, quality, and precision of material processing [1,2]. Recently by numerical modeling, we have demonstrated that appl ication of radially -polarized doughnut-shape pulses for volumetric modification of fused silica can provide considerable differences in the strength and geometry of modification as compared with Gaussian pulses with the same irradiation parameters (bear energy, pulse duration, numerical aperture )[3]. In the case of a doughnut-shaped beam, the free-electron plasma generated in the focus region has a toroidal shape. Consequently, a part of laser radiation scattered by the plasma propagates to the axes of the laser-excited zone, contrary to Gaussian pulses where the laser light is mostly scattered to the periphery. As a result, the part of the beam scattered to the axis induces an enhanced ionization close to the axis where, according to simulations, the absorbed density of laser energy can be more than an order of magnitude higher as compared to the Gaussian laser pulse. On the stage of the elastoplastic relaxation of the laser -excited material, such a large absorbed energy will generate a huge mechanic al stress comparable with the pressure levels in the Earth's mantle.
In this work, the action ofthe focused doughnut-shaped pulses with radial and azimuthal polarization on fused silica has been investigated numerically and the effects of polarization are studied for different numerical apertures. The model is based on nonlinear Maxwell 's equations supplemented by the equations of hydrodynamic type for the description of the generation of the free electron plasma and its motion in the laser field [3]. The equations are solved by an original finite-difference scheme presented in Ref. [4].
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[2] A. Möhl, S. Kaldun, C. Kunz, F. A. Müller, U. Fuchs, S. Graf, Tailored focal beam shaping and its application in laser material processinj J. Laser Appl., vol. 31, article 042019 (2019).
[3] V. P. Zhukov, A.M. Rubenchik, M.P. Fedoruk, N. M. Bulgakova, Interaction of doughnut-shaped laser pulses with glasses, J. Opt. Soc. Am. B, vol. 34, No 2, pp. 463-471, (2017).
[4] V. P. Zhukov, M. P. Fedoruk, Numerically implemented impact of a femtosecond laser pulse on glass in the approximation of nonlinear
Maxwell equations, Math. Models Comput. Simul., vol. 12, No. 1, pp. 77-89, (2020).
