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Proceedings Paper

Nonlinear effects during interaction of femtosecond doughnut-shaped laser pulses with glasses: overcoming intensity clamping
Author(s): Nadezhda M. Bulgakova; Vladimir P. Zhukov; Mikhail P. Fedoruk; Alexander M. Rubenchik
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Paper Abstract

Interaction of femtosecond laser pulses with a bulk glass (fused silica as an example) has been studied numerically based on non-linear Maxwell’s equations supplemented by the hydrodynamics-type equations for free electron plasma for the cases of Gaussian linearly-polarized and doughnut-shaped radially-polarized laser beams. For Gaussian pulses focused inside glass (800 nm wavelength, 45 fs duration, numerical aperture of 0.25), the free electron density in the laser-excited region remains subcritical while the locally absorbed energy density does not exceed ~2000 J/cm3 in the range of pulse energies of 200 nJ – 2 μJ. For doughnut-shaped pulses, the initial high-intensity ring of light is shrinking upon focusing. Upon reaching a certain ionization level on its way, the light ring splits into two branches, one of which shrinks swiftly toward the beam axis well before the geometrical focus, leading to generation of supercritical free electron density. The second branch represents the laser light scattered by the electron plasma away from the beam axis. The final laserexcited volume represents a tube of 0.5–1 μm in radius and 10-15 μm long. The local maximum of absorbed energy can be more than 10 times higher compared to the case of Gaussian beams of the same energy. The corresponding pressure levels have been evaluated. It is anticipated that, in the case of doughnut-shaped pulses, the tube-like shape of the deposited energy should lead to implosion of material that can be used for improving the direct writing of high-refractive index optical structures inside glass or for achieving extreme thermodynamic states of matter.

Paper Details

Date Published: 16 May 2017
PDF: 8 pages
Proc. SPIE 10228, Nonlinear Optics and Applications X, 102280C (16 May 2017); doi: 10.1117/12.2265307
Show Author Affiliations
Nadezhda M. Bulgakova, HiLASE Ctr. (Czech Republic)
Vladimir P. Zhukov, Institute of Computational Technologies SB RAS (Russian Federation)
Novosibirsk State Technical Univ. (Russian Federation)
Mikhail P. Fedoruk, Institute of Computational Technologies SB RAS (Russian Federation)
Novosibirsk State Univ. (Russian Federation)
Alexander M. Rubenchik, Lawrence Livermore National Lab. (United States)

Published in SPIE Proceedings Vol. 10228:
Nonlinear Optics and Applications X
Mario Bertolotti; Joseph W. Haus; Alexei M. Zheltikov, Editor(s)

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