Contents

Part 1 Survey of laser systems 
1.1 
Survey of laser systems 
W. 
Schulz ............................................................ 3

1.1.1 
Introduction ............................................................ 3

1.1.2 
Principles and experiments ............................................... 4

1.1.2.1 
Nonlinear ampli.cation .................................................. 4

1.1.2.2 
Selection of optical modes or directional selectivity .......................... 6

1.1.2.3 
Feedback resonator and regenerative ampli.cation ........................... 7

1.1.3 
Technical implementation, performance and applications ..................... 9

1.1.3.1 
Gas laser systems ....................................................... 9

1.1.3.1.1 
CO2 laser systems ....................................................... 9

1.1.3.1.2 
Excimer laser systems.................................................... 10

1.1.3.1.3 
Argon-ion laser systems .................................................. 10

1.1.3.1.4 
Helium-neon laser systems................................................ 10

1.1.3.2 
Solid-state laser systems.................................................. 11

1.1.3.2.1 
Diode-pumped solid-state laser systems .................................... 12

1.1.4 
Advanced design and short-pulse solid-state laser systems .................... 13

1.1.4.1 
Fundamentals of laser performance ........................................ 14

1.1.4.1.1 
Resonator design ........................................................ 14

1.1.4.1.1.1 
Rod end-pumped design.................................................. 14

1.1.4.1.1.2 
Rod side-pumped design ................................................. 14

1.1.4.1.1.3 
Slab side-pumped design ................................................. 15

1.1.4.1.1.4 
Innoslab end-pumped design............................................ 15

1.1.4.1.1.5 
Disc end-pumped design.................................................. 15

1.1.4.2 
Advances in laser performance ............................................ 15

1.1.4.3 
Resonator design ........................................................ 16

1.1.4.4 
Slitting with pulsed solid-state laser ....................................... 17

1.1.4.5 
Processing with higher harmonics ......................................... 18

1.1.5 
High-power diode laser (HPDL) systems.................................... 20

1.1.5.1 
Packaging technology .................................................... 21

1.1.5.2 
Multiplexing the emission of single bars .................................... 22

1.1.5.3 
Coherent coupling ....................................................... 23

1.1.5.4 
Direct applications with low beam intensity................................. 24

1.1.5.5 
Cutting and welding ..................................................... 24


References for 1.1 ....................................................... 27

Contents 
Part 2 Short and ultrashort pulse generation 
2.1	
Ultrafast solid-state lasers 
U. 
Keller ............................................................. 33

2.1.1	
Introduction ............................................................ 33

2.1.2	
De.nition of Q-switching and mode-locking................................. 35

2.1.2.1	
Q-switching ............................................................ 35

2.1.2.2	
Mode-locking ........................................................... 36

2.1.3	
Overview of ultrafast solid-state lasers ..................................... 39

2.1.3.1	
Overview for di.erent solid-state laser materials............................. 39

2.1.3.1.1	
Solid-state laser materials ................................................ 40

2.1.3.1.2	
Mode-locked rare-earth-doped solid-state lasers.............................. 66

2.1.3.1.3	
Mode-locked transition-metal-doped solid-state laser ......................... 67

2.1.3.1.4	
Q-switched ion-doped solid-state microchip lasers............................ 68

2.1.3.1.5	
Ultrafast semiconductor lasers ............................................ 69

2.1.3.1.6	
Ultrafast .ber lasers ..................................................... 73

2.1.3.2	
Design guidelines of diode-pumped solid-state lasers ......................... 73

2.1.3.3	
Laser cavity designs ..................................................... 76

2.1.3.3.1	
Typical picosecond lasers................................................. 76

2.1.3.3.2	
Typical femtosecond lasers................................................ 77

2.1.3.3.3	
High-power thin-disk laser................................................ 78

2.1.4	
Loss modulation ........................................................ 79

2.1.4.1	
Optical modulators: acousto-optic and electro-optic modulators ............... 79

2.1.4.2	
Saturable absorber: self-amplitude modulation (SAM)........................ 79

2.1.4.2.1	
Slow saturable absorber .................................................. 82

2.1.4.2.2	
Fast saturable absorber .................................................. 82

2.1.4.3	
Semiconductor saturable absorbers ........................................ 83

2.1.4.3.1	
Semiconductor dynamics ................................................. 83

2.1.4.3.2	
Typical self-amplitude modulation (SAM)
from semiconductor saturable absorbers .................................... 85

2.1.4.3.3	
Semiconductor saturable absorber materials ................................ 86

2.1.4.3.3.1	
InGaAs/GaAs/AlGaAs semiconductor material system....................... 86

2.1.4.3.3.2	
GaInAsP/InP semiconductor material system............................... 86

2.1.4.3.3.3	
GaInNAs semiconductor material.......................................... 87

2.1.4.3.3.4	
AlGaAsSb semiconductor material......................................... 87

2.1.4.3.3.5	
GaAs wafer for  1 m .................................................. 87

2.1.4.3.3.6	
Semiconductor-doped dielectric .lms....................................... 87

2.1.4.3.4	
Historical perspective and SESAM structure ................................ 88

2.1.4.4	
E.ective saturable absorbers using the Kerr e.ect ........................... 90

2.1.4.4.1	
Transverse and longitudinal Kerr e.ect..................................... 90

2.1.4.4.2	
Nonlinear coupled cavity ................................................. 90

2.1.4.4.3	
Kerr lens............................................................... 91

2.1.4.4.4	
Nonlinear polarization rotation............................................ 92

2.1.4.5	
Nonlinear mirror based on second-harmonic generation....................... 92

2.1.5	
Pulse propagation in dispersive media...................................... 92

2.1.5.1	
Dispersive pulse broadening .............................................. 92

2.1.5.2	
Dispersion compensation ................................................. 94

2.1.5.2.1	
GiresTournois interferometer (GTI)....................................... 96

2.1.5.2.2	
Grating pairs ........................................................... 96

2.1.5.2.3	
Prism pairs............................................................. 99

2.1.5.2.4	
Chirped mirrors.........................................................100

2.1.6	
Mode-locking techniques .................................................102

2.1.6.1	
Overview...............................................................102

2.1.6.2	
Hauss master equations..................................................102

2.1.6.2.1	
Gain...................................................................105

2.1.6.2.2	
Loss modulator .........................................................106

2.1.6.2.3	
Fast saturable absorber ..................................................106

2.1.6.2.4	
Group velocity dispersion (GVD)..........................................106

2.1.6.2.5	
Self-phase modulation (SPM) .............................................107

2.1.6.3	
Active mode-locking .....................................................108

2.1.6.4	
Passive mode-locking with a slow saturable absorber
and dynamic gain saturation..............................................110

2.1.6.5	
Passive mode-locking with a fast saturable absorber .........................112

2.1.6.6	
Passive mode-locking with a slow saturable absorber
without gain saturation and soliton formation...............................114

2.1.6.7	
Soliton mode-locking.....................................................115

2.1.6.8	
Design guidelines to prevent Q-switching instabilities ........................119

2.1.6.9	
External pulse compression ...............................................120

2.1.7	
Pulse characterization....................................................121

2.1.7.1	
Electronic techniques ....................................................121

2.1.7.2	
Optical autocorrelation ..................................................121

2.1.7.3	
New techniques: FROG, FROG-CRAB, SPIDER, ... ........................123

2.1.7.3.1	
FROG, SHG-FROG, FROG-CRAB........................................123

2.1.7.3.2	
SPIDER ...............................................................124

2.1.7.3.3	
Comparison between FROG and SPIDER techniques ........................125

2.1.8	
Carrier envelope o.set (CEO).............................................126

2.1.9	
Conclusion and outlook ..................................................129

2.1.10 
Glossary ...............................................................131


Contents	XI 
References for 2.1 .......................................................134

Part 3 Gas lasers 
3.1	
Gas laser systems 

R. 
Wester ............................................................171

3.1.1 
Introduction ............................................................171

3.1.2 
Threshold pump power density............................................172

3.1.2.1 
Line Broadening ........................................................174

3.1.2.1.1 
Natural line broadening ..................................................174

3.1.2.1.2 
Doppler broadening......................................................175

3.1.2.1.3 
Pressure broadening .....................................................175

3.1.3 
Excitation mechanisms...................................................176

3.1.3.1 
Gas discharge excitation..................................................176

3.1.3.2 
Electron-beam excitation.................................................177

3.1.3.3 
Gas-dynamic excitation ..................................................178

3.1.3.4 
Chemical excitation......................................................179

3.1.4 
Gas discharges ..........................................................180

3.1.4.1 
Elementary processes in gas discharges .....................................180

3.1.4.2 
Electron distribution function.............................................182

3.1.4.2.1 
Similarity laws ..........................................................183

3.1.4.2.2 
Characteristic frequencies ................................................183

3.1.4.2.3 
Rate coe.cients.........................................................184

3.1.4.2.4 
Approximate solutions of the Boltzmann equation ...........................184

3.1.4.2.5 
Charged-particle densities ................................................185

3.1.4.2.6 
Ambipolar di.usion......................................................186

3.1.4.3 
Electromagnetic .eld ....................................................187

3.1.4.4 
Neutral gas.............................................................188

3.1.4.5 
Discharge instabilities....................................................189

3.1.4.5.1 
Thermal instabilities.....................................................189

3.1.4.6 
Discharge types .........................................................190

3.1.4.6.1 
Glow discharges.........................................................191

3.1.4.6.1.1 
Secondary processes .....................................................191

3.1.4.6.2 
High-pressure glow discharges.............................................192

3.1.4.6.3 
High-frequency glow discharges............................................192

3.1.4.6.3.1 
Boundary layers in high-frequency discharges ...............................193

3.1.4.6.4 
Microwave discharges ....................................................194

3.1.4.6.5 
Arc discharges ..........................................................195



References for 3.1 .......................................................197

3.2 
CO2 laser and CO laser 
J. 
Uhlenbusch, W. Vi
ol ...............................................205

3.2.1 
CO2 laser ..............................................................205

3.2.1.1 
Fundamentals of CO2 laser discharge ......................................205

3.2.1.2 
Practical design of cw CO2 lasers..........................................206

3.2.1.2.1 
Sealed-o. lasers .........................................................207

3.2.1.2.2 
Lasers with slow axial .ow ...............................................207

3.2.1.2.3 
Lasers with fast axial .ow ................................................207

3.2.1.2.4 
Transverse-.ow lasers ....................................................208

3.2.1.2.5 
Gas-dynamic lasers ......................................................208

3.2.1.3 
Practical design of pulsed CO2 lasers ......................................208

3.2.1.3.1 
Transversely excited atmospheric-pressure lasers.............................208

3.2.1.3.2 
Q-switched low-pressure lasers ............................................209

3.2.2 
CO laser ...............................................................209

3.2.2.1 
Fundamentals of CO laser process .........................................209

3.2.2.2 
Practical design of cw CO lasers...........................................210

3.2.2.2.1 
Sealed-o. lasers .........................................................211

3.2.2.2.2 
Lasers with axial and transversal .ow......................................211

3.2.2.2.3 
Pulsed CO lasers ........................................................211



References for 3.2 .......................................................212

3.3 
Femtosecond excimer lasers and their applications 
S. 
Szatm
ari, G. Marowsky, P. Simon ..................................215

3.3.1 
Introduction ............................................................215

3.3.1.1 
Advantages and di.culties associated with short-wavelength lasers ............215

3.3.1.2 
General features of dual-wavelength laser systems ...........................216

3.3.1.3 
Comparison of high-power solid-state and excimer lasers......................217

3.3.1.4 
Seed pulse generation ....................................................219

3.3.1.4.1	
General features of hybrid dye/excimer lasers ...............................219

3.3.1.4.2	
Hybrid solid-state/excimer lasers ..........................................219

3.3.2	
Short-pulse ampli.cation properties of excimers .............................220

3.3.3	
Critical issues for a high-power excimer ampli.er ............................223

3.3.3.1	
Nonlinear e.ects, attainment of minimum pulse duration (spatially evolving
chirped-pulse ampli.cation)...............................................223

3.3.3.2	
Ampli.cation in media having nonsaturable absorption.......................225

3.3.3.2.1	
ASE content, nonsaturable absorption, limitations on the cross-section .........225

3.3.3.2.2	
O.-axis ampli.cation ....................................................226

3.3.3.2.3	
Multiple-pass o.-axis ampli.cation schemes.................................229

3.3.3.2.4	
Requirements for the discharge geometries of o.-axis ampli.ers................230

3.3.3.3	
Limited energy storage time (interferometric multiplexing)....................230

3.3.3.3.1	
Limitations on multiple-pass ampli.cation..................................231

3.3.3.3.2	
Optical multiplexing.....................................................231

3.3.3.3.3	
Interferometric multiplexing ..............................................232

3.3.3.4	
Focusability of short-wavelength high-intensity lasers.........................233

3.3.3.4.1	
Pulse front distortion, spatially dependent temporal broadening ...............233

3.3.3.4.2	
Origin of phase-front distortions in dual-wavelength laser systems .............234

3.3.3.4.3	
Active spatial .ltering ...................................................234

3.3.3.4.4	
Spectral .ltering ........................................................235

3.3.3.4.5	
Optimization of o.-axis ampli.ers for minimum phase-front distortion .........238

3.3.3.4.6	
Beam homogenization method for short-pulse excimers.......................238

3.3.3.4.7	
Focusability measurements ...............................................239

3.3.4	
Application of short laser pulses...........................................242

3.3.4.1	
Application of short laser pulses for plasma generation .......................242

3.3.4.2	
Micromachining of materials with subpicosecond UV pulses...................244



References for 3.3 .......................................................248

3.4	
Ion lasers and metal vapor lasers 
W. 
Seelig .............................................................255

3.4.1	
Introduction ............................................................255

3.4.2	
Properties of gas discharge laser media.....................................256

3.4.3	
Noble gas ion lasers......................................................259

3.4.3.1	
Excitation mechanism....................................................259

3.4.3.2	
Operating characteristics .................................................261

3.4.3.2.1	
Neutral gas depletion ....................................................261

3.4.3.2.2	
Axial gas pumping ......................................................262

3.4.3.2.3	
Transition regions .......................................................262

3.4.3.2.4	
Magnetic .elds..........................................................263

3.4.3.2.5	
Summary of operation parameters .........................................263

3.4.4	
Helium metal ion lasers ..................................................265

3.4.4.1	
Excitation mechanism....................................................265

3.4.4.2	
Operating characteristic of the continuous HeCd laser.......................266

3.4.5	
Self-terminating metal vapor lasers ........................................268

3.4.5.1	
Excitation mechanism....................................................268

3.4.5.2 
Operating characteristics .................................................269



References for 3.4 .......................................................272

3.5 
Excimer lasers 
U. 
Sowada ............................................................275

3.5.1 
Introduction ............................................................275

3.5.2 
Wavelengths and stimulated emission cross sections..........................275

3.5.2.1 
Rare-gas halogen excimers................................................275

3.5.2.1.1 
Rare-gas monohalides....................................................275

3.5.2.1.2 
Polyatomic rare-gas halogen excimers ......................................277

3.5.2.2 
Rare-gas excimers .......................................................278

3.5.2.3 
Halogen excimers........................................................278

3.5.3 
Chemical reactions in the discharge........................................278

3.5.4 
Beam properties.........................................................284

3.5.4.1 
Pulse energy and pulse duration...........................................284

3.5.4.2 
Output power...........................................................284



References for 3.5 .......................................................285

3.6 
Gasdynamical lasers, chemical lasers 
M. 
Hugenschmidt .....................................................289

3.6.1 
Introduction, historical background ........................................289

3.6.2 
Gasdynamic lasers (GDLs) ...............................................290

3.6.2.1 
Conventional combustion-driven GDLs.....................................290

3.6.2.1.1 
Population inversion due to gasdynamic processes ...........................290

3.6.2.1.2 
GDL fuels and energy requirements........................................292

3.6.2.1.3 
Numerical modeling and simulations .......................................293

3.6.2.1.4 
Population densities and small-signal gain achieved in gasdynamic lasers .......295

3.6.2.1.5 
Power extraction ........................................................296

3.6.2.1.6 
Simpli.ed calculation of small-signal gain, analytical approximations...........297

3.6.2.1.7 
Speci.c experimental investigations, realization of pulsed laser systems.........299

3.6.2.1.8 
Optical cavity design ....................................................299

3.6.2.2 
Downstream mixing GDLs................................................300

3.6.2.3 
Gasdynamic CO2 laser by detonation of solid explosives......................301

3.6.3 
Fast-.ow electric discharge lasers (EDL)....................................301

3.6.3.1 
Electrically excited fast-.ow or gasdynamic CO lasers........................301

3.6.3.2 
Electrical discharge excited gasdynamic CO2 lasers ..........................304

3.6.3.3 
Miscellaneous ...........................................................305

3.6.4 
Chemical lasers .........................................................306

3.6.4.1 
Fundamental processes, vibrational, rotational and translational temperatures...306

3.6.4.2 
Speci.c reactions and operation principles of chemical lasers ..................307

3.6.4.3 
Discussion and evaluation of chemical laser systems..........................308

3.6.4.3.1 
Iodine lasers ............................................................308

3.6.4.3.1.1 
Pulsed systems, photolytically initiated iodine lasers (PIL) ...................308

3.6.4.3.1.2 
Continuous-wave iodine lasers (COIL) .....................................309

3.6.4.3.2 
HCl and HBr lasers......................................................310

3.6.4.3.2.1 
Pulsed HCl lasers and HBr laser studies....................................310

3.6.4.3.2.2 
Continuous-wave laser excitation ..........................................311

3.6.4.3.2.3 
Numerical analysis ......................................................311

3.6.4.3.3 
CO lasers ..............................................................311

3.6.4.3.3.1 
Pulsed CO lasers ........................................................312

3.6.4.3.3.2 
Continuous-wave CO lasers ...............................................313

3.6.4.3.4 
HF, DF lasers...........................................................314

3.6.4.3.4.1 
Pulsed HF, DF lasers ....................................................314

3.6.4.3.4.2 
Continuous-wave HF or DF lasers .........................................320

3.6.4.3.5 
Transfer chemical lasers ..................................................325

3.6.4.3.5.1 
Pulsed transfer chemical (TCL) CO2 lasers .................................326

3.6.4.3.5.2 
Continuous-wave DFCO2 transfer chemical lasers...........................327

3.6.4.3.6 
Miscellaneous ...........................................................331

3.6.4.3.6.1 
Pulsed NO laser.........................................................331

3.6.5 
Concluding remarks .....................................................332



References for 3.6 .......................................................333

3.7 
Iodine lasers 
K. 
Rohlena, J. Ber
anek ...............................................341

3.7.1 
Principles of operation ...................................................341

3.7.2 
Laser transition cross-section .............................................342

3.7.3 
Iodine photodissociation lasers ............................................344

3.7.3.1 
Pumping kinetics of the iodine photodissociation laser .......................344

3.7.4 
Chemical oxygen iodine laser (COIL) ......................................346

3.7.4.1 
Generators of the excited oxygen (SOG)....................................347

3.7.4.2 
Pumping kinetics of the chemical oxygen-iodine laser ........................348

3.7.4.3 
All-gas chemical oxygen-iodine lasers.......................................349

3.7.5 
Outlook................................................................350



References for 3.7 .......................................................351

Index ............................................................................357



XII Contents 
Contents	XIII XIV Contents Contents XV 
