TY - GEN

T1 - Nonlinear effects during interaction of femtosecond doughnut-shaped laser pulses with glasses

T2 - 7th Nonlinear Optics and Applications Conference

AU - Bulgakova, Nadezhda M.

AU - Zhukov, Vladimir P.

AU - Fedoruk, Mikhail P.

AU - Rubenchik, Alexander M.

PY - 2017/1/1

Y1 - 2017/1/1

N2 - 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.

AB - 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.

KW - doughnut-shaped laser pulses

KW - free electron plasma

KW - Gaussian laser pulses

KW - glass

KW - Laser beam propagation

KW - Maxwell's equations

KW - non-linear processes

KW - WAVE-GUIDES

UR - http://www.scopus.com/inward/record.url?scp=85029166163&partnerID=8YFLogxK

U2 - 10.1117/12.2265307

DO - 10.1117/12.2265307

M3 - Conference contribution

AN - SCOPUS:85029166163

SN - 978-1-5106-0957-0

VL - 10228

T3 - Proceedings of SPIE

BT - Nonlinear Optics and Applications X

A2 - Bertolotti, M

A2 - Haus, JW

A2 - Zheltikov, AM

PB - SPIE

Y2 - 24 April 2017 through 25 April 2017

ER -