Transmission of intense femtosecond laser pulses into dielectrics

Peñano, Joseph; Sprangle, P.; Hafizi, B.; Manheimer, Wallace M.; Zigler, A.

doi:10.1103/physreve.72.036412

Cited by 83 publications

(79 citation statements)

References 26 publications

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“…By means of numerical simulations that solve the time-dependent electromagnetic wave equation and include multiphoton ionization, electron attachment, Ohmic heating of free electrons, and temperature-dependent collisional ionization, Peñano et al (2005) have modeled self-consistently the transmission, reflection, and absorption of laser pulses of 10-100 fs duration and peak intensities of 10 12 -10 14 W/cm 2 , by a thin, highly collisional plasma layer. These laser pulses interacting with fused silica were shown to produce above-critical plasma densities and electron energy densities sufficient to attain experimentally measured damage thresholds.…”

Section: Permanent Index Modification and Damagementioning

confidence: 99%

Femtosecond filamentation in transparent media

2007

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Section: Permanent Index Modification and Damagementioning

confidence: 99%

Femtosecond filamentation in transparent media

2007

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“…15 The electron recombination time is τ rec = 150 × 10 −15 s. 21 For an excitation wavelength of λ = 800nm and a fused silica target with a band gap of W ion = 9eV , 6 photons are needed to promote an electron to the conduction band, resulting in an ionization rate…”

Section: Numerical Modelmentioning

confidence: 99%

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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“…For such pulses, the electron dynamics in the timedependent field of the pulse be described in terms of the density matrix whose evolution is determined by rate equations with phenomenological relaxation and generation times [19][20][21][22][23] . In this description, the effect of the pulse electric field is restricted to generation of an electronhole plasma through multiphoton or collisional ionization processes.…”

Section: Introductionmentioning

confidence: 99%

Theory of dielectric nanofilms in strong ultrafast optical fields

Apalkov

Stockman

2012

Phys. Rev. B

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We theoretically predict that a dielectric nanofilm subjected to a normally-incident strong but ultrashort (a few optical oscillations) laser pulse exhibits deeply nonlinear (non-perturbative) optical responses which are essentially reversible and driven by the instantaneous optical field. Among them is a high optical polarization and a significant population of the conduction band, which develop at the peak of the pulse and almost disappear after its end. There is also a correspondingly large increase of the pulse reflectivity. These phenomena are related to Wannier-Stark localization and anticrossings between the Wannier-Stark ladders originating from the valence and conduction bands leading to optical "softening" of the dielectric. Theory is developed by solving self-consistently the Maxwell equations and the time-dependent Schrödinger equation. The results point out to a fundamental possibility of optical-field effect devices with the bandwidth on the order of optical frequency.

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Transmission of intense femtosecond laser pulses into dielectrics

Cited by 83 publications

References 26 publications

Femtosecond filamentation in transparent media

Femtosecond filamentation in transparent media

Self-organized pattern formation in laser-induced multiphoton ionization

Theory of dielectric nanofilms in strong ultrafast optical fields

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