Femtosecond Laser Filamentation (eBook)

Preface 7
Acknowledgement 9
Contents 10
1 Introduction 13
1.1 Mature Physics and New Development 13
1.2 Phase Effect of a Laser Pulse Propagating in an Optical Medium 15
1.3 Multiphoton and Tunnel Ionization 16
1.4 Optical Breakdown 18
1.5 Intense Femtosecond Laser Beam Attenuation 20
2 Filamentation Physics 22
2.1 Some Experimental Observations 22
2.2 Experimental Definition of a Filament by Burn Paper 26
2.3 Single Filamentation Physics 27
2.3.1 Slice-by-Slice Self-Focusing 27
2.3.2 Intensity Clamping 32
2.3.3 Is There Optical Breakdown During Filamentation? 34
2.3.4 Effect of External Focusing 36
2.3.5 Background Energy Reservoir 37
2.3.6 Self-Spatial Mode Filtering 42
2.3.7 Self-Phase Modulation, Self-Steepening and White Light Laser (Supercontinuum) 43
2.3.8 Conical Emission 47
2.3.9 Ring Structure at the Pump Wavelength 49
2.3.10 Self-Pulse Compression 49
2.3.11 X-wave 51
2.4 Full Evolution of a Single Filament 51
2.5 Maturity of a Filament 57
2.6 Filamentation Without Ionization 57
2.7 What Is a Filament? 58
3 Theory of Single Filamentation 60
3.1 Introduction 60
3.2 Filamentation in Air 60
3.3 Numerical Solution of Filamentation in Air 62
3.4 Filamentation in Condensed Matter 66
3.5 x-Wave and Conical Emission1 66
4 Multiple Filamentation 71
4.1 Introduction 71
4.2 Multiple Filamentation: Experimental Observation 71
4.3 Interference and Competition of Multiple Filaments 74
4.4 Theory of Multiple Filamentation 77
4.5 The Challenge of Long Distance Filamentation 78
4.6 Long Distance Multiple Filamentation Control 78
5 Filamentation Nonlinear Optics: General 81
5.1 Self-Actions 81
5.2 Self-Remote Projection in Air 82
5.3 Self-Pulse Compression 83
5.4 Exploitations of the Self-Actions 84
6 Filamentation Nonlinear Optics: Third Harmonic Generation and Four-Wave-Mixing Inside a Filament 87
6.1 Introduction 87
6.2 Third Harmonic Generation Inside a Filament in Air (Theoretical Analysis) 87
6.3 Experiment on THG in Air 93
6.4 Conical Emission and Superbroadening of the Third Harmonic in Air 95
6.5 Efficient Tunable Few Cycle Visible Pulse Generation Through Four-Wave-Mixing Inside the Filament Core 95
6.6 Self-Group-Phase Locking During Four-Wave-Mixing Inside a Filament 98
6.7 Derivation of Equation ( 6.1 ) 99
7 Remote Sensing Using Filamentation 102
7.1 Introduction 102
7.2 Remote Control of Filamentation 103
7.3 Physical Considerations 105
7.4 Detection of Chemical and Biological Agents in Air 106
7.4.1 Molecules in the Gas/Vapor Phase 106
7.4.2 Biological Targets 108
7.4.3 Metallic Targets 109
7.4.4 Water Aerosols Containing Metallic Salts 109
7.5 Conclusion and Looking Ahead 110
8 Challenges Ahead 111
8.1 Multiple Filamentation 112
8.1.1 Why Does a Large Diameter Beam Diverge Slowly Over Long Distances When There Is Multiple Filamentation? 112
8.1.2 Filament Collaboration 112
8.1.3 Optimum Wavelength to Produce the Broadest and Strongest White Light 113
8.1.4 Filament Control Using a Deformable Mirror 113
8.2 Time-Resolved Excitation of Superexcited States of Molecules 114
8.3 Ultrafast Birefringence 117
8.3.1 Filament-Induced Birefringence 118
8.3.2 Excitation of Molecular Rotational Wave Packets in Air and Polarization Separation 122
8.3.3 Just the Beginning of Filament-Induced Birefringence 126
References 127
Index 133