Influence of crystal structure on the ultrafast ionization of cubic wide-band-gap crystals by ultrashort laser pulses

Gruzdev, Vitali E.; Sergaeva, Olga

doi:10.1364/cleo_si.2018.sm3o.4

Cited by 1 publication

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“…[72] and also neglects possible contributions from multiple valence bands [73] as well as degeneracy of the valence and conduction bands [68,71]. Estimations of the nonlinear-absorption rates by the Keldysh formula can be further improved if proper energy-momentum relations are utilized since the Keldysh approach demonstrates a significant influence of energy-momentum relation on the photo-ionization rate [74]. When all those factors are properly taken into account, the Keldysh formula delivers the magnitudes of nonlinear absorption that coincide with experimental data with accuracy of some 30-50%.…”

Section: Ionizationmentioning

confidence: 99%

Ultrafast Laser Material Damage Simulation—A New Look at an Old Problem

et al. 2022

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The chirped pulse amplification technique has enabled the generation of pulses of a few femtosecond duration with peak powers multi-Tera and Peta–Watt in the near infrared. Its implementation to realize even shorter pulse duration, higher energy, and higher repetition rate laser systems relies on overcoming the limitations imposed by laser damage of critical components. In particular, the laser damage of coatings in the amplifiers and in post-compression optics have become a bottleneck. The robustness of optical coatings is typically evaluated numerically through steady-state simulations of electric field enhancement in multilayer stacks. However, this approach cannot capture crucial characteristics of femtosecond laser induced damage (LID), as it only considers the geometry of the multilayer stack and the optical properties of the materials composing the stack. This approach neglects that in the interaction of an ultrashort pulse and the materials there is plasma generation and associated material modifications. Here, we present a numerical approach to estimate the LID threshold of dielectric multilayer coatings based on strong field electronic dynamics. In this dynamic scheme, the electric field propagation, photoionization, impact ionization, and electron heating are incorporated through a finite-difference time-domain algorithm. We applied our method to simulate the LID threshold of bulk fused silica, and of multilayer dielectric mirrors and gratings. The results are then compared with experimental measurements. The salient aspects of our model, such as the implementation of the Keldysh photoionization model, the impact ionization model, the electron collision model for ‘low’-temperature, dense plasma, and the LID threshold criterion for few-cycle pulses are discussed.

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