Investigations in the nonlinear behavior of dielectrics by using ultrashort pulses (Best Oral Presentation)

Starke, K.; Ristau, Detlev; Welling, H.; Amotchkina, Tatiana V.; Trubetskov, Michael K.; Tikhonravov, Alexander V.; Chirkin, A. S.

doi:10.1117/12.525132

Cited by 28 publications

(28 citation statements)

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“…Momentum transfer collisions entering the Drude model are collisions of electrons with phonons and heavy particles such as neutrals and ions [10,14,33,[96][97][98][99][100][101][102]. Electron-electron collisions cannot contribute to τ coll as both particles have the same effective mass.…”

Section: Description Of the Breakdown Dynamicsmentioning

confidence: 99%

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

et al. 2016

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The wavelength dependence of the threshold for femtosecond optical breakdown in water provides information on the interplay of multiphoton, tunneling and avalanche ionization, and is of interest for parameter selection in laser surgery. We measured the bubble threshold from UV to near-IR wavelengths and found a continuous decrease of the irradiance threshold with increasing wavelength λ. Results are compared to the predictions of a numerical model that assumes a bandgap of 9.5 eV and considers the existence of a separate initiation channel via excitation of valence band electrons into a solvated state followed by rapid upconversion into the conduction band. Fits to experimental data yield an electron collision time of ≈ 1 fs, and an estimate for the capacity of the initiation channel. Using that collision time, the breakdown dynamics was explored up to λ = 2 µm. The irradiance threshold first continues to decrease but levels out for wavelengths longer than 1.3 µm. This opens promising perspectives for laser surgery at wavelengths around 1.3 µm and 1.7 µm, which are attractive because of their large penetration depth into scattering tissues.

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Section: Description Of the Breakdown Dynamicsmentioning

confidence: 99%

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

et al. 2016

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“…20,31 The experimentally measured relaxation times involving in self-trapped electron excitation is applied to describe the decay process of excited electrons. 5,15,32 The detailed calculations of W PI , W II and W rel for KDP crystal are presented in the Supplemental Material.…”

Section: -3mentioning

confidence: 99%

Determination of ultra-short laser induced damage threshold of KH2PO4 crystal: Numerical calculation and experimental verification

et al. 2016

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Rapid growth and ultra-precision machining of large-size KDP (KH2PO4) crystals with high laser damage resistance are tough challenges in the development of large laser systems. It is of high interest and practical significance to have theoretical models for scientists and manufacturers to determine the laser-induced damage threshold (LIDT) of actually prepared KDP optics. Here, we numerically and experimentally investigate the laser-induced damage on KDP crystals in ultra-short pulse laser regime. On basis of the rate equation for free electron generation, a model dedicated to predicting the LIDT is developed by considering the synergistic effect of photoionization, impact ionization and decay of electrons. Laser damage tests are performed to measure the single-pulse LIDT with several testing protocols. The testing results combined with previously reported experimental data agree well with those calculated by the model. By taking the light intensification into consideration, the model is successfully applied to quantitatively evaluate the effect of surface flaws inevitably introduced in the preparation processes on the laser damage resistance of KDP crystals. This work can not only contribute to further understanding of the laser damage mechanisms of optical materials, but also provide available models for evaluating the laser damage resistance of exquisitely prepared optical components used in high power laser systems.

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“…For the theoretical modeling, rate equation models are applied to investigate the interaction of high power laser irradiation with dielectric materials. In the framework of thin film technology adapted rate equations are used to calculate the free electron density during irradiation with short laser pulses to model for example the laser induced damage threshold [30] and the linear as well as the nonlinear material absorption [31]. Since the optical and electronic properties in terms of the band gap and the refractive index represent an essential part of the needed input parameters for the rate equation calculations, it is quite desirable to use the concept of the virtual coater in order to calculate these values.…”

Section: From Atomistic To Rate Equation Modelsmentioning

confidence: 99%

Simulation in thin film technology

et al. 2015

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Braunschweig, Germany ABSTRACTSimulation and modeling find more and more their way into thin film technology. Beside theoretical models for layer design, pre-production design analysis, and real time process control, atomistic simulation techniques gain of importance. Here, especially classical procedures such as Direct Simulation and Particle-in-Cell Monte Carlo (DSMC/PIC-MC), kinetic Monte Carlo (kMC) and Molecular Dynamics (MD) as well as quantum mechanical techniques based on Density Functional Theory (DFT) have to be mentioned. These methods are applied in order to investigate the material transport inside the coating facilities, the thin film growth in dependence of characteristic process conditions, and the optical and electronic thin film properties. By combination of these atomistic techniques in a suitable manner, a multiple scale simulation model can be realized for investigating the influence of specific process conditions on the resulting layer properties. The further extension of this "virtual coater" concept with respect to rate equation models enables the possibility to investigate also the interaction of laser irradiation with the modeled thin film structures.

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Investigations in the nonlinear behavior of dielectrics by using ultrashort pulses (Best Oral Presentation)

Cited by 28 publications

References 0 publications

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

Wavelength dependence of femtosecond laser-induced breakdown in water and implications for laser surgery

Determination of ultra-short laser induced damage threshold of KH2PO4 crystal: Numerical calculation and experimental verification

Simulation in thin film technology

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