Femtosecond Laser-Matter Interactions: Solid-Plasma-Solid Transformations at the Extreme Energy Density

Cover
Half Title
Title Page
Copyright Page
Dedication
Table of Contents
Preface
List of frequently used symbols
Chapter 1: Basics of Laser–Matter Interactions: Light and Matter
1.1: Laser Beam
1.1.1: Macroscopic Electrodynamics
1.1.2: Polarization States
1.1.3: Spectral Structure
1.1.4: Temporal/Spatial Shape of the Incident Laser Pulse Intensity
1.1.5: Focussing Positions of the Laser Beam on/in a Target
1.1.6: Focussing to Diffraction Limit with the High NA Lens
1.1.7: Diffraction-Free Beams
1.2: The Matter
1.2.1: Electrons’ Oscillations and Scattering in the High-Frequency Electromagnetic Field
1.2.2: The Drude Model for the Permittivity of Simple Plasma in the High-Frequency Electric Field
1.2.2.1: Electrons’ plasma frequency
1.2.2.2: Critical density of electrons
1.2.3: Absorbed Energy Density
1.2.4: Hierarchy of the Laser-Affected Material Transformations as a Function of Laser Intensity/Fluence
1.2.4.1: Melting
1.2.4.2: Ablation
1.2.4.3: Atomic field intensity
1.2.4.4: The relativistic intensity
1.3: Summary
Chapter 2: Interaction with Metals
2.1: Interaction of the Plane Wave with a Metal Layer
2.2: Electron and Lattice Temperature, Energy Balance, Two-Temperature Approximation
2.3: Temperature Dependence of the Electronic and Lattice Heat Capacity
2.4: Electrons Relaxation Processes in the Laser-Affected Metal
2.4.1: Electron–Electron Collisions
2.4.2: Electron–Phonon Momentum Transfer
2.4.3: Electron–Phonon Energy Transfer
2.4.4: Electron-to-Ion Momentum and Energy Transfer
2.4.5: Electron-to-Ion Energy Exchange Time
2.4.5.1: Non-ideality effects
2.4.5.1: Effects of the oscillations in high-frequency electromagnetic field on the electrons’ collision rate
2.5: Modification of the Electron Distribution Function: From the Fermi–Dirac to the Maxwell–Boltzmann
2.6: Electronic Heat Conduction
2.7: Summary
Chapter 3: Interaction with Dielectrics
3.1: Ionization in the Strong High-Frequency Electric Field: Electrons Transfer from the Valence to Conduction Band and to Continuum
3.1.1: Tunnelling Ionization Rate in the Limit y << 1
3.1.1.1: Linear polarization
3.1.1.2: Tunnel ionization in the elliptically polarized electric field
3.1.2: Multi-Photon Ionization Rate
3.1.2.1: Linear polarization
3.1.2.2: Time dependence of the ionization degree produced by the Gaussian laser pulse with the MPI domination
3.1.2.3: Circular polarization
3.1.3: Ionization by the Electron Impact
3.1.3.1: Transition to the avalanche regime
3.1.4: Distribution Function of Electrons Transferred to the Conduction Band in Dielectrics
3.2: Electrons’ Collision Rates: Momentum and Energy Transfer
3.2.1: Electron–Phonon Collisions
3.2.2: Momentum and Energy Transfer Collisions in a Dielectric Converted to Plasma
3.2.3: Effects of the Electrons’ Oscillations in the HF Field on the Collision Rates
3.3: Transient Permittivity in the Laser-Affected Dielectric
3.3.1: Non-Linear Contributions to the Permittivity at the Low Intensity (I << Iat)
3.3.2: Kerr-Nonlinearity in Silica: Temperature Dependence
3.3.3: Permittivity in the Intense-Laser-Excited Dielectric
3.3.3.1: Reaching the state Ɛre = 0
3.4: Laser Interaction with the Electrically Inhomogeneous Dielectric
3.4.1: Normal Incidence
3.4.2: Oblique Incidence
3.4.2.1: s-Polarization
3.4.2.2: p-Polarization
3.4.2.3: Band gap modification and collapse
3.5: Energy Density Thresholds for Achieving the Major Steps in Dielectric-Plasma Transformation
3.5.1: Threshold to Achieve the State Where Ɛre = 0
3.5.2: Threshold Fluence for Transferring All Valence Electrons to the Conduction Band
3.5.3: Ionization Threshold: Transfer Electrons to the Solid Plasma State
3.6: Energy Equations: Two-Temperature Approximation
3.7: Linear and Non-Linear Heat Conduction: Transition from Heat Transfer in Solid to That in Plasma
3.7.1: Heat Diffusion in the Isotropic Medium
3.7.2: Thermal Conduction in Dielectrics: Energy Carriers are Phonons
3.7.3: Electronic Heat Conduction in Plasma
3.7.4: Applicability of Diffusion Approximation for Description the Heat Conduction in the Laser-Created Plasma
3.7.5: Linear and Non-Linear Heat Propagation from the Focal Region
3.7.5.1: Linear heat conduction
3.7.5.2: Non-linear heat propagation
3.8: Summary
Chapter 4: Non-Destructive Transformations: Formation, Lifetime and Decay of Unconventional States of Matter
4.1: Generation and Decay of the Coherent Phonons
4.1.1: Melting in Equilibrium: Atomic Vibrations Become Anharmonic
4.1.2: Swift Deposition of the Energy Density Comparable to the Enthalpy of Fusion by the Ultra-Short Laser Pulse
4.1.2.1: Processes during the pulse: building the electronic pressure force
4.1.2.2: After the end of the pulse: electronic heat transfer, electron–lattice temperature equilibration, and phonon’s decay rate
4.1.2.3: Phonon’s excitation imprinted into the transient optical properties
4.1.2.4: Experiments
4.2: Fast Transformations in Non-Equilibrium: Transient Phase States—Neither Solid Nor Melt
4.2.1: Road to Melting in Equilibrium: Sequence of the Catastrophes
4.2.1.1: Main features of the melting in equilibrium
4.2.1.2: Critical entropy and critical temperature
4.2.2: Ultra-Fast Material Transformations
4.2.2.1: The legitimacy of the entropy concept for the description of rapidly excited metal
4.2.2.2: Entropy changes during the quick heating
4.2.3: Novel Transient Phase States—Neither Solids Nor Melts
4.2.3.1: Excitation of metals/semi-metals—Ga, Bi, Al
4.3: Mixed Dielectric/Metal Properties in Swiftly Excited Transparent Dielectric
4.4: Inverse Population in Laser-Excited Sapphire and Silica
4.5: Summary
Chapter 5: Ablation of Metals and Dielectrics
5.1: Evaporation in Equilibrium
5.2: Major Relaxation Processes under Swift Short Pulse Excitation
5.3: Short Pulse Ablation Thresholds
5.3.1: Ablation of Metals
5.3.1.1: Extremely short pulses of duration shorter tc,i
5.3.1.2: Comparison to the Coulomb explosions of clusters
5.3.1.3: Ultra-short pulses ω-1pi < tp < theat
5.3.1.4: Ablation threshold fluence for metals
5.3.2: Ablation of Dielectrics
5.4: Dependence of the Ablation Thresholds on the Laser Wavelength for Metals and Dielectrics
5.5: Long Pulse Ablation Thresholds
5.6: Ablation Thresholds in the Ambient Gas
5.7: Ablation Rate, Depth and Mass Per Single Pulse
5.8: Control over the Phase State of the Ablated Plume
5.8.1: Criterion for Complete Atomization of Ablated Plume
5.8.2: Experimental Verification of the Plume’s Atomization
5.9: Multiple Pulse Action: Accumulation Effects
5.9.1: Dwell Time: Control over the Number of Pulses Hitting the Spot
5.9.2: Multiple-Pulse Action on Dielectrics: Energy Accumulation
5.9.3: Achieving Thermal Ablation Threshold with the Low-Energy Multiple Pulses
5.9.4: Smoothing of the Intensity Distribution across the Focal Spot
5.9.5: Change of the Interaction Mode: Density Build-Up near the Target Surface
5.10: Summary
Chapter 6: Extreme Energy Density Confined inside a Transparent Crystal—Novel Path for New Materials Creation: Solid-Plasma-Solid Transformations
6.1: Introduction
6.2: Interaction of the Gauss Beam Tightly Focused inside a Transparent Crystal
6.2.1: Beam Propagation
6.2.2: Focusing of the Gauss Beam with the High-NA Optics
6.2.2.1: Conventional approach to the high-NA focusing
6.2.2.2: Experimental evidence: high-NA focus produces nano-sharp intensity distribution
6.2.3: Laser Modification of the Dielectric Permittivity: Conversion to Solid Density Plasma
6.2.3.1: Threshold for Conversion of Dielectric into Absorbing Medium (εre = 0)
6.2.3.2: Conversion a dielectric to the solid density plasma
6.2.3.3: Ionization after the end of the pulse
6.2.4: Relaxation Processes
6.2.4.1: Range for the maximum temperature/pressure value in the absorption volume
6.2.4.2: Ion’s acceleration by the gradient of the electronic pressure
6.2.4.3: Electrons-to-ions energy transfer by the Coulomb collisions: Spatial separation of the light and heavy ions
6.2.4.4: Diffusion of ions with the different masses: The experimental evidence of the spatial separation
6.2.5: Micro-Explosion in Sapphire Considered as a Strong Point-Like Explosion
6.2.5.1: Interpretation of the micro-explosion experiments using the strong point-like explosion solution
6.2.6: Summary of the Conditions after the Electron–Ion Energy Equilibration Shock Wave Generation, Propagation and Stopping
6.2.6.1: Analysis of the experimentally observed structure on the basis of the energy and mass conservation laws
6.2.6.2: Evolution of the conditions and the structure of the laser affectedzone during expansion
6.2.7: Modelling the Hydrodynamics of the Confined Explosion
6.2.8: Relaxation of the Laser-Affected Material to the Ambient Conditions
6.3: Interaction of the Gauss Beam Tightly Focused on the Surface of an Opaque Solid Buried under the Transparent Cover
6.3.1: Upper Limit for the Energy Density Directly Delivered to the Opaque Medium through the Transparent Layer
6.3.2: High-Energy-Density Interaction at the Silicon/Silica Interface
6.3.3: Shock Wave Generation in Silica Layer
6.4: Summary of the Gauss Beam–Generated Confined Micro-Explosions
6.5: Interaction of the Bessel Beam Focused inside a Bulk of the Transparent Crystal
6.5.1: Status of the BB–Transparent Crystal Interactions
6.5.2: Non-Diffractive Bessel Beam
6.5.3: Creation of the BB by the Circular Slit
6.5.4: Formation the BB by Transmitting the GB through the Axicon
6.5.5: BB Interaction with the Transparent Medium at Low Intensity
6.5.6: Intense BB Interaction: Conversion a Dielectric into Plasma Near the Axis
6.5.7: BB Interaction with Plasma
6.5.8: Energy Deposition in Plasma to the End of the Pulse
6.5.9: Strong Cylindrical Explosion
6.5.10: Experimental Evidence of the High Energy Density Achieved by the BB Induced Cylindrical Explosion
6.6: Solid-Plasma-Solid Transformation in Confined Micro-Explosion: New Path for High-Pressure Material Phase Formations
6.6.1: Discovery of Superdense bcc-Al in Sapphire Irradiated by the Tightly Focused Gauss Beam
6.6.2: Discovery of New Tetragonal Polymorphs of Silicon
6.7: Summary: Confined Micro-Explosion by the Gauss and Bessel Beams
Conclusions and Future Directions
Appendices
Bibliography
Index