Femtosecond Laser Filamentation (Springer Series on Atomic, Optical, and Plasma Physics Book 55)

__Femtosecond Laser Filamentation__ gives a comprehensive review of the physics of propagation of intense femtosecond laser pulses in optical media (principally air) and the applications and challenges of this new technique. This book presents the modern understanding of the physics of femtosecond laser pulse propagation, including unusual new effects such as the self-transformation of the pulse into a white light laser pulse, intensity clamping, the physics of multiple filamentation and competition, and how filaments’ ability to melt glass leads to wave guide writing. The potential applications of laser filamentation in atmospheric sensing and the generation of other electromagnetic pulses from the UV to the radio frequency are treated, together with possible future challenges in the excitation of super-excited states of molecules. Exciting new phenomena such as filament induced ultrafast birefringence and the excitation of molecular rotational wave packets and their multiple revivals in air (gases) will also be discussed. This volume provides the most comprehensive and up-to-date discussion of these topics currently available. It will be of great interest to scientists and researchers using intense femtosecond laser pulses as well as to graduate students and researchers who wish to learn more about the field. 000 1 001 2 Preface 7 Acknowledgement 9 Contents 10 002 13 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 20 003 22 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? 58 004 60 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 66 005 71 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 78 006 81 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 84 007 87 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 ) 99 008 102 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 110 009 111 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 126 010 127 References 127 Index 133 This book attempts to give a discussion of the physics and current and potential applications of the self-focusing of an intense femtosecond laser pulse in a tra- parent medium. Although self-focusing is an old subject of nonlinear optics, the consequence of self-focusing of intense femtosecond laser pulses is totally new and unexpected. Thus, new phenomena are observed, such as long range lam- tation, intensity clamping, white light laser pulse, self-spatial ltering, self-group phase locking, self-pulse compression, clean nonlinear uorescence, and so on. Long range propagation at high intensity, which is seemingly against the law of diffraction, is probably one of the most exciting consequences of this new sub- eld of nonlinear optics. Because the intensity inside the lament core is high, new ways of doing nonlinear optics inside the lament become possible. We call this lamentation nonlinear optics. We shall describe the generation of pulses at other wavelengths in the visible and ultraviolet (UV) starting from the near infrared pump pulse at 800 nm through four-wave-mixing and third harmonic generation, all in gases. Remotely sensing uorescence from the fragments of chemical and biological agents in all forms, gaseous, aerosol or solid, inside the laments in air is demonstrated in the labo- tory. The results will be shown in the last part of the book. Through analyzing the uorescence of gas molecules inside the lament, an unexpected physical process pertaining to the interaction of synchrotron radiation with molecules is observed. Front Matter....Pages i-xiii Introduction....Pages 1-9 Filamentation Physics....Pages 11-48 Theory of Single Filamentation....Pages 49-59 Multiple Filamentation....Pages 61-70 Filamentation Nonlinear Optics: General....Pages 71-76 Filamentation Nonlinear Optics: Third Harmonic Generation and Four-Wave-Mixing Inside a Filament....Pages 77-91 Remote Sensing Using Filamentation....Pages 93-101 Challenges Ahead....Pages 103-118 Back Matter....Pages 119-130