Author: Alexandros MouskeftarasPublisher:
ISBN:
Category :
Languages : en
Pages : 182
Book Description
Study of the Physical Mechanisms Involved in the Femtosecond Laser Optical Breakdown of Dielectric Materials
Author: Alexandros MouskeftarasPublisher:
ISBN:
Category :
Languages : en
Pages : 182
Book Description
Numerical Study of Femtosecond Laser Interactions with Dielectric Materials
Author: Nikita ShcheblanovPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
With the appearance of new ultra-short laser systems, extremely high laser intensities became accessible thus allowing laser treatment of practically all materials. As a result, extremely precise processing techniques are under development considerably extending the number of the corresponding industrial and medical applications. Further progress in this field requires a better understanding of fundamental processes involved in the laser interactions. In addition, the success of several national and international involving the development and use of high power laser systems depends on the capacity of careful definition of damage threshold of their optical components. These points illustrate the importance of a detailed numerical modeling of laser interactions with dielectric materials. Under laser irradiation, seed electrons appear in the conduction band of dielectric materials due to photo-ionization process. Colliding with a third-body, these electrons are further heated in laser field. When the threshold electron energy is reached, electron-impact ionization begins. At the same time, the considered laser pulses are so short that electron sub-system has no time to reach an equilibrium state. The resulting optical properties are affected and the definition of the damage criterion should be revised. The proposed approach accounts for the non-equilibrium and provides a detailed description of all the involved processes. In particular, we consider the photo- and impact-ionization processes, as well as electron-electron, electron-phonon and electron-ion collisions. The electron energy distribution and heating of electronic and phonon subsystems is discussed. The role of laser parameters (wavelength, pulse duration, fluence) and material properties (energy gap, band structure) is investigated. The thermalization time is calculated and characterizes the non-equilibrium state as a function of laser pulse duration. A novel thermal criterion is proposed for damage definition based on the electron and phonon energies. The calculated damage thresholds are compared with recent experimental findings. An analysis of other criteria (classical optical breakdown and thermal) is also performed.
Optically Induced Nanostructures
Author: Karsten KönigPublisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110383500
Category : Science
Languages : en
Pages : 360
Book Description
Nanostructuring of materials is a task at the heart of many modern disciplines in mechanical engineering, as well as optics, electronics, and the life sciences. This book includes an introduction to the relevant nonlinear optical processes associated with very short laser pulses for the generation of structures far below the classical optical diffraction limit of about 200 nanometers as well as coverage of state-of-the-art technical and biomedical applications. These applications include silicon and glass wafer processing, production of nanowires, laser transfection and cell reprogramming, optical cleaning, surface treatments of implants, nanowires, 3D nanoprinting, STED lithography, friction modification, and integrated optics. The book highlights also the use of modern femtosecond laser microscopes and nanoscopes as novel nanoprocessing tools.
Laser Induced Damage in Optical Materials
Author: Laser Breakdown of Dielectric Materials
Author: Alan HeinsPublisher:
ISBN:
Category :
Languages : en
Pages : 194
Book Description
"The breakdown of dielectric solids and transparent gases by high-intensity femtosecond laser pulses are experimentally investigated. The plasma emission from atmospheric-pressure gases is studied. The plasma emission strength is shown to exhibit much less shot-to-shot variance than the plasma generated by longer-pulse lasers; this observation is explained by the different breakdown mechanism active for very short pulses. The breakdown plasma defocuses the pulse which creates it; this process is studied experimentally and through a Finite-Difference Time-Domain (FDTD) simulation. The plasma also causes a spectral blueshift in the generating pulse; the spectrum of the transmitted pulse is investigated. Time-resolved measurements of the evolving plasma shape are presented. The defocus, blueshift, and plasma shape experiments are all conducted for both linear and circular polarization -- and it is found that a circularly polarized pulse behaves exactly like a linearly polarized pulse of lower intensity. The intensity shift is determined to be 1.36 times, and is consistent among all three experiments, but disagrees with the 1.5 times shift seen in vacuum experiments. In spite of possessing a lower overall number of ions, the plasma generated with a circular pulse is shown to emit more brightly than one produced with a linear pulse. This is connected with theoretical descriptions of ionization which predict higher electron kinetic energies following a circularly polarized breakdown pulse, and shows that kinetic energy plays a major role in producing plasma emission. The role of impact excitation is reaffirmed in a mixed-gas experiment, in which it is shown that a lower-ionization-potential gas can increase emission from a higher-ionization-potential gas. In dielectric solids, it is found that circular pulses produce a narrower but deeper crater. The crater profiles are well fit by an atomic model which primarily considers lattice heating from electron collisions. In both solids and gases, the role of dephasing of the electron motion -- induced either through collisions or continuous blueshifting of the pulse -- is found to be the critical factor in moving energy from the pulse to the material. Finally, the effects of the shockwave generated when a solid is ablated in air are studied"--Page iii.
Research on the Electrical Breakdown of Gases Under Intense Optical Illumination
Author: R. G Meyer (Jr)Publisher:
ISBN:
Category :
Languages : en
Pages : 21
Book Description
A theoretical and experimental research program has been conducted on the physical mechanisms associated with the electrical breakdown of gases under the intense optical illumination from a laser. The light beam from a ruby laser was focused to a small region in the center of a test cell to ionize helium, argon, and air. Breakdown in air required the highest field strengths, the next highest were required to ionize helium, and the lowest field strengths were required for argon. Theoretical studies have indicated that the inverse Bremsstrahlung process, involving the absorption of optical photons by free electrons during collisions with gas atoms, satisfactorily accounts for the high degree of ionization produced during the short laser pulse and, in addition, predicts the observed pressure dependence of the breakdown. It was observed that as much as 50% of the total energy in the laser beam was absorbed in the plasma produced by breakdown and ttenuations by as much as a factor of 10 were observed in the intensity of the laser beam at later times in the optical pulse. An extension of inverse Bremsstrahlung to the fully ionized case shows considerable promise as the process to account for this absorption. (Author).
Femtosecond Laser-Matter Interaction
Author: Eugene G. GamalyPublisher: CRC Press
ISBN: 9814241814
Category : Science
Languages : en
Pages : 370
Book Description
This is the first comprehensive treatment of the interaction of femtosecond laser pulses with solids at nonrelativistic intensity. It connects phenomena from the subtle atomic motion on the nanoscale to the generation of extreme pressure and temperature in the interaction zone confined inside a solid. The femtosecond laser-matter interaction has already found numerous applications in industry, medicine, and materials science. However, there is no consensus on the interpretation of related phenomena. With mathematics kept to a minimum, this is a highly engaging and readable treatment for students and researchers in science and engineering. The book avoids complex mathematical formulae, and hence the content is accessible to nontechnical readers. Useful summaries after each chapter provide compressed information for quick estimates of major parameters in planned or performed experiments. The book connects the basic physics of femtosecond laser-solid interactions to a broad range of applications. Throught the text, basic assumptions are derived from the first principles, and new results and ideas are presented. From such analyses, a qualitative and predictive framework for the field emerges, the impact of which on applications is also discussed.
Femtosecond Laser Micromachining
Author: Roberto OsellamePublisher: Springer Science & Business Media
ISBN: 364223366X
Category : Science
Languages : en
Pages : 485
Book Description
Femtosecond laser micromachining of transparent material is a powerful and versatile technology. In fact, it can be applied to several materials. It is a maskless technology that allows rapid device prototyping, has intrinsic three-dimensional capabilities and can produce both photonic and microfluidic devices. For these reasons it is ideally suited for the fabrication of complex microsystems with unprecedented functionalities. The book is mainly focused on micromachining of transparent materials which, due to the nonlinear absorption mechanism of ultrashort pulses, allows unique three-dimensional capabilities and can be exploited for the fabrication of complex microsystems with unprecedented functionalities.This book presents an overview of the state of the art of this rapidly emerging topic with contributions from leading experts in the field, ranging from principles of nonlinear material modification to fabrication techniques and applications to photonics and optofluidics.
Controlled Material Modification of Transparent Dielectrics by Femtosecond Laser Pulses
Author: Marina GertsvolfPublisher:
ISBN:
Category : Dielectric devices
Languages : en
Pages : 186
Book Description
Author: