Modeling the Early Ionization of Dielectrics by Ultrashort Laser Pulses

Bourgeade, Antoine; Mézel, C.; Saut, Olivier

doi:10.1007/s10915-010-9375-0

Cited by 14 publications

(6 citation statements)

References 20 publications

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“…[7][8][9][10] As far as nonlinear self-organization is concerned, a certain seed is required to start the process. Therefore, we follow a different approach and investigate the interaction of laser light with nanometer-sized inhomogeneities.…”

Section: -6mentioning

confidence: 99%

“…[4][5][6] Previous modelling efforts concerning laser energy deposition in dielectrics have concentrated on the temporal and spatial evolution of the laser pulse itself, while treating the material as homogeneous. [7][8][9][10] As far as nonlinear self-organization is concerned, a certain seed is required to start the process. Therefore, we follow a different approach and investigate the interaction of laser light with nanometer-sized inhomogeneities.…”

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confidence: 99%

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Self-organized pattern formation in laser-induced multiphoton ionization

2014

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We use finite-difference time-domain modelling to investigate plasma generation induced by multiphoton absorption of intense laser light in dielectrics with tiny inhomogenities. Plasma generation is found to be strongly amplified around nanometer-sized inhomogeneities as present in glasses. Each inhomogeneity acts as the seed of a plasma structure growing against the direction of light propagation. Plasma structures originating from randomly distributed inhomogeneities are found to interact strongly and to organize in regularly spaced planes oriented perpendicularly to the laser polarization. We discuss similarities between our results and nanogratings in fused silica written by laser beams with spatially homogeneous as well as radial and azimuthal polarization.Many dielectrics as e.g. silica glasses are known to be transparent within a wide frequency range. Only at high intensities absorption becomes possible, as electrons are promoted to the conduction band by nonlinear ionization processes.1 The strong intensity dependence of multiphoton ionization allows for the selective excitation and laser-induced modification of a small focal region situated inside a material volume. Different kinds of material modification have been observed, including refractive index changes, 2 void formation 3 and subwavelength volume grating formation. 4-6Previous modelling efforts concerning laser energy deposition in dielectrics have concentrated on the temporal and spatial evolution of the laser pulse itself, while treating the material as homogeneous.7-10 As far as nonlinear self-organization is concerned, a certain seed is required to start the process. Therefore, we follow a different approach and investigate the interaction of laser light with nanometer-sized inhomogeneities. This is of fundamental interest due to the inherent inhomogeneity of amorphous materials like silica glasses.11 Such inhomogeneities have also been suggested to play a major role in volume nanograting formation. 12Our simulations are based on the standard parameters which can be found in the literature. A good overview of the parameters of laser light and free carriers present during nanograting formation has been given by Bulgakova et al.9 . There, the intensities achieved by focussing and nonlinear propagation inside the homogeneous material cause smooth, submetallic carrier density distributions. We use similiar parameters, but in our case material inhomogeneities increase the local intensity and cause the formation of plasma spots. We demonstrate, that the ionization process is independent of the exact shape and nature of the initial inhomogeneities. However we can identify two regimes depending on the local carrier densities that are reached during irradiaton. For low carrier densities, ionization enhancement remains confined to the initial region of field enhancement close to an inhomogeneity. For higher carrier densities, a single nanoplasma forming at an inhomogeneity site enhances further ionization in its vicinity and acts as a seed for the gro...

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Section: -6mentioning

confidence: 99%

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confidence: 99%

Self-organized pattern formation in laser-induced multiphoton ionization

2014

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“…Finally, for the curve labeled "FI only" there was no CI contribution and we assessed damage using the plasma density criterion [Eq. (19)], which do not properly account for the energy deposition in the material.…”

Section: Effective Dre Parameters From Experimentsmentioning

confidence: 99%

“…For example in Refs. [2,6,10,19], simulations were performed within similar theoretical frameworks, but led to conflicting conclusions as different values for the LH rates were used.…”

Section: Introductionmentioning

confidence: 99%

Dynamical rate equation model for femtosecond laser-induced breakdown in dielectrics

2021

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Experimental and theoretical studies of laser-induced breakdown in dielectrics provide conflicting conclusions about the possibility to trigger ionization avalanche on the subpicosecond time scale and the relative importance of carrier-impact ionization over field ionization. On the one hand, current models based on a single ionizationrate equation do not account for the gradual heating of the charge carriers, which, for short laser pulses, might not be sufficient to start an avalanche. On the other hand, kinetic models based on microscopic collision probabilities have led to variable outcomes that do not necessarily match experimental observations as a whole. In this paper, we present a rate-equation model that accounts for the avalanche process phenomenologically by using an auxiliary differential equation to track the gradual heating of the charge carriers and define the collisional impact rate dynamically. The computational simplicity of this dynamical rate-equation model offers the flexibility to extract effective values from experimental data. This is demonstrated by matching the experimental scaling trends for the laser-induced damage threshold of several dielectric materials for pulse durations ranging from a few fs to a few ps. Through numerical analysis, we show that the proposed model gives results comparable to those obtained with multiple rate equations and identify potential advantages for the development of large-scale, three-dimensional electromagnetic methods for the modeling of laser-induced breakdown in transparent media.

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“…For example in refs. [1,4,7,17], plasma formation was modelled within similar theoretical frameworks, but assumed different IBH rates, thus influencing directly the efficiency of II and leading to conflicting conclusions about the relative importance of II over FI and the occurrence of ionization avalanche in short pulses.…”

Section: Introductionmentioning

confidence: 99%

Delayed-rate equations model for femtosecond laser-induced breakdown in dielectrics

Déziel,

Dubé,

Varin

2019

Preprint

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Modeling the Early Ionization of Dielectrics by Ultrashort Laser Pulses

Cited by 14 publications

References 20 publications

Self-organized pattern formation in laser-induced multiphoton ionization

Self-organized pattern formation in laser-induced multiphoton ionization

Dynamical rate equation model for femtosecond laser-induced breakdown in dielectrics

Delayed-rate equations model for femtosecond laser-induced breakdown in dielectrics

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