LASER FUNDAMENTALS
`
`SECOND EDITION
`
`WILLIAM T. SI LFVAST
`
`School ul Oplics 1' CRECIL
`Lhiunlsily of Centrd Florida
`
`CAMBRIDGE
`UNIVERSITY PRESS
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`ASML 1008
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`ASML 1008
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`

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`PUBLISHED III" THE 3% 51"N'lII].|l'l'E OF THE. UNIVERSITY DIFCALIBEJIIIE
`The PM lllikilg, Tklupinghn Slnaet. -1'_‘:1It|i£fin,'l.I|iIaIl Kilggltln
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`ISBN l]—32l—333-15-!)
`1. L551 ]_ 'I"|‘.h.
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`ISBNl]S1I33.'-H-SI] Illllaml
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`‘2(Il3(]553252
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`

`
`Contents
`
`Prefiice to the Second .E'dition
`
`Prefixce to the First Edition
`
`Aeknawletflgnlttents
`
`1
`
`INTRODUCTION
`UI"EIl\I'IE|I'
`llttmtltlclion
`Deliilion of llie I..ase-1'
`
`Simplicily 0|’ 2 Laser
`Unitpe
`of :1 Laser
`The Laser Spectrum and Hfawlertgtlls
`A Brief Hislory ofllle Laser
`f|1reI't"IeIrIr of the ll‘-uolt
`
`SECTION 1- FUNDAMENTAL WAVE PROPERTIES OF LIGHT
`
`2 WAVE NATURE OF LIGHT — THE INTERACTION CIF LIGHT
`WITH MATERIALS
`CW'Ell\iIEH'
`
`2.1 Ma!n'rI.=Il"s Faplatiuns
`2.1 IL'[a:n-nell"s Wave Equulinns
`Maxwell's ‘Wave Equations for a Vacuum
`Solution of tho Gentztal Wave Equation — Equivalsooo of Light and
`EI c Radiation
`‘Wave VeIot::il].r — ]3'I1aat'. and Group Velocities
`tkttetalized So-Iulion ofdmwatre Equation
`TI.'aI'IS‘W:l'Sl.'. Eloclrolttagoatic Waves and Polarized Light
`Flow of EI ic Energy
`Radiation [mm a Point Souroo (Elocuic Dipole Radiation]
`2.3- [ute:nu:lioI1 of Flleclrutlagnelic Radialion tliglit) will Matter
`Spread of Light in a Medium
`Maxwell‘: Equations in a Medium
`Application of Maxwell's Equations In Dielectric Materials —
`Laser Gain Media
`
`Complex: Index of Rofmclzion — Optical Constants
`Absorption and Dispersion
`
`page xix
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`ui
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`xxiii
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`L11-H-'4-'lI‘-'lI‘-'l'—'—-'—
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`EHEEfifitfii-"BEESEfiuauaua
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`
`viii
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`CONTENTS
`
`Estimating Particle Densities of Materials for Use in the
`Dispersion Equ stions
`1.4 Coherence
`
`Temporal Coherence
`Spatial Coherence
`REFERENCES
`FIIDIILEHS
`
`SECTHJN Z. FIJHDAMEHTJIL GIIAHTIIII PROPERTES BF LE3-IT
`
`3 PARHCLE NATURE DF LIGHT — DIS-Cl1E'l'E ENERGY LEVELS
`D"l"ER'l|"IF'W
`
`3.1 Bohr Theory ulthe Hydrogen Mom
`Historical Developrnent of die Concept of Discrete Energy Levels
`Energy Levels of lhe Hydrogen Atom
`Frequency and Wat-'eleogth of Emission Lines
`Ionizafion Energies and Energy Levels of Ions
`Photons
`
`J-.2 Quantum Tlleory of ilttulnic F.nes'gg.' Levels
`Wave Nature of Paiiicles
`
`Heisenberg Uncertainty Principle
`Wave Tl'LrEDl.'}'
`Wave Functions
`Quantum States
`The Schrodinger We're Equation
`Energy and Wave Function for the Ground State of die
`Hydrogen Atom
`Excited States ol'I-[ydrogen
`Allowed Quantum Numbers for Hydrogen Atom Wave Funciions
`5.3 Angular Menlenlum of At-runs
`Drbitel Angular Momentum
`Spin Angular Momentum
`Total Angular Momeonirn
`3.1} Energy Lei-1-Is .'l|sso("Inled with Due-Electron Alnnts
`Fine Smictlire o1'Speo1.ral Lines
`Pauli Exclusion Principle
`3.5 Periodic Table oftlne Elements
`
`Quantum Condhions Associ mad with ll-'[ulI:ipie Electrons Attached
`to Nuclei
`
`Shorrliand Notation for Electronic Configurations ofmoms Having
`More Than Dne ElecLron
`
`J-.6 Emerge Levels 0|’ Mnlli-Eleelron Atoms
`Energy-Level Designation for llpiulli-Eleclion States
`RusseIl—.'Saunders or L5 Coupling — Notalion for Energy i..-f.'.'."'e'Bl5
`Energy Levels Associated with Two Eleclrons in Unfilled Shells
`Rules for C|Ib1.sini.ng S. L. and J for L5 Coupling
`Degeneracy and Strnisiical Weights
`_i—_f Coupling
`lsoelectronic Scaling
`
`34
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`37
`3 E
`39
`39
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`45
`45
`45
`45
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`49
`5 l
`54
`54
`54
`56
`56
`57
`57
`59
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`I53
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`67
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`aififlfl
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`7'0
`5'2
`'32
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`e‘:1::ls‘
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`T9
`32
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`E5
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`CONTENTS
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`REFERENCES
`PROBLEMS
`
`4 RADMTNE TRANSITIDNS AND EMISSION LINEWIDTH
`Dlt'EIH|"lE'lI'
`
`4.1 Decay offlxcited States
`Radiative Decay of Excited States of Isolated Atoms —
`Spontaneous Emission
`Spontaneous Emission Decay Rate — Radiative Transition
`Probability
`lifetime of a Radiating Electron — The Electron as a Classical
`Radiating Harmonic Dscillator
`Nonradiative Decay of die Excited States — Collisional Decay
`4.2 Entisaien Broadening anti Line1=rid'th Due to Radiative Decay
`Classical Emission 1..ine-it-'i:iH1 of a Radiati ng Electron
`Natural Emission Linewidlh as Deduced by Quantum Mechanics
`{Minimum Linewidthll
`4.5 Additional F.rnisaio|1-llrocadeniltg P'rocesses
`Broadening Due to Nonradiative (Collisions!) Decay
`Broadening Due to Dephasing Collisions
`Alrtorphous Crystal Broadening
`Doppler Broadening in Gases
`Vii-ig Lirteshape Profile
`Broadening in Gases Due to Isotope Slrifts
`Comparison ofl-"anions Types of Emission Broadening
`11.4 Quantum Mechanical Description of Radiating Atoms
`Electric Dipole Radiation
`Electric Dipole l'tI'lEI2I'l.'t'. Element
`Electric Dipole Transition Probability
`Oscillator Strength
`Selection Rules for Electric Dipole Transitions Involving Atoms
`with a Single Electron in an Unfilled Subshell
`Selection Rules for Radiative Ttansitions Involving Atoms with
`More Thanflne Electron in an Unlilled Sub-shell
`
`Parity Selection Rule
`[rtefficient Radiative Transitions — Electric Quadrupole and Other
`1-ligher-Drder Transitions
`IitF.li'ERENlZ'ES
`PRDIILEMS
`
`5 ENERGY LEVELS AND lllI.D‘I!iT|"t|"E PROPERTIES OF MOLECULES.
`LIGIIIDS. AND SOLIDS
`{WE.Il\".'IE'H'
`
`5.1 Molecular Energy Levels and Spectra
`Energy Levels of Molecules
`Classification of Simple Molecules
`Rotational Energy Levels of Linear Molecules
`Rotational Energy Levels of SyrnmeLric—Top Molecules
`Selection Rules for Rotational Transitions
`
`Eli
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`89
`B9
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`94
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`101
`H11
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`103
`105
`106
`1131‘
`109
`1'09
`114
`115
`113
`121
`122
`123
`124
`124
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`125
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`129
`13!]
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`131
`131
`131
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`135
`135
`135
`135
`133
`139
`111-1
`111-1
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`CONTENTS
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`Vibrational Energy Levels
`Selection Rule for ‘#3:!-rational Transitions
`Rotational—\"ibra1:ional Transitions
`Probabilities of Rotational and ‘fibrafional Transitions
`
`Electrortic Energy Levels of Molecules
`Electronic Transitions and Associated Selection Rules of
`Molecules
`Emission Linewidth of Molecular Transitions
`
`The Franclt—Condon Principle
`E:I.cirner Energy l_.e'rel_s
`5.2 Liquid Energy lrcvek and Their Radiation Properties
`Smtcmre of Dye Molecules
`Energy l..evels of Dye Molecules
`Excitation and Emission of D3-'1:-: Molecules
`Elletrirrterttal Triplet States ofD}-‘e Molecules
`5.3 Emerge l..e\-'eIs in Solids — Dielectric Laser Evlalerials
`Host Materials
`
`Laser Species — Dopant Ions
`!"~larro'u.'-]'_.inew'idr1'| Laser Materials
`Broadband Tunable Laser Materials
`
`Broadening Mec11s.nisrn for Solid-State Lasers
`5.4 FJ14.-:rg'_|' Levels in Solids — liemicon-duetor Laser Materials
`Energy Bands in Crystalline Solids
`Energy Levels in Periodic Structures
`Energy Levels of Conductors. lrlsulators. and 3-enricondttctors
`Excitation and Decay of Excited Energy Levels — Recombination
`Radiation
`
`Direct and Indirect Bandgap Serniconductors
`Electron Distribution Function and Density of States in
`Semiconductors
`intrinsic Selrticortductor Materials
`
`E'.r.Iri.nsic Semiconductor Materials — Doping
`p—n Junctions — Recombination Radiation Due to Electrical
`Excitation
`
`Heterojunctiort Senrioonductor Materials
`Quantum Wells
`Variation of Bandgap Energy and Radiation Wavelength with
`Alloy Composition
`Recombi nation Radiation Transition Probability and l_.inewidth
`REFERENCES
`!"ItDBLEli'l5
`
`E: RADIATICIN MID THERMAL EQLI UBRIJM — ABS-DRPTIDH AND
`ST|lItl|.lL.:I.TE|Z| EMISSDN
`owzswnrw
`
`6.1 Equill:lJ:riu.m
`Thermal Equilibrium
`Thermal Equilibrium vie Conduction and Convection
`Thermal Eqtlilibrium via Radiation
`
`143
`143
`144
`143
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`149
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`1.50
`150
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`15!
`152
`153
`153
`155
`156
`157
`153
`153
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`159
`16!
`166
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`163
`163
`163
`17!]
`172
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`173
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`1'34
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`175
`1'II'9
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`179
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`132
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`134
`1315
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`19!
`195
`195
`195
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`199
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`199
`199
`23]
`QED
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`CONTENTS
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`6.1 Radiating Bodies
`Stefan—BoIt:t.mann Law
`Wien‘s Law
`Lrradiance and Radiance
`
`t‘i.3- Cavity Radiation
`Counting me Nttrrtbecr offlavity Modes
`Ra}.rieigII—Jeans Formula
`Planck's Law for Cavity Radiation
`Relationship between Cavity Radiation and Blaolthody
`Radiation
`
`Wavelength Depertdenoe of Blaekbody Emission
`ti.-4 Absorption and Stimulated Ention.
`The Piineiple ot'De'tsiled Balance
`A|:Iso1'pliorL and Stimulated Emission Coefficierus
`REFERENCES
`FEDILEBIS
`
`EECTIDN 3. LASER Milt"-‘LIFIERE
`
`? EDN DITIDNS FOR PRODUCING A. LASER — PCIPU LATIDN
`IITJERSIGHS, GAIN. AND G.AtN SJ‘-'tTlJRA't'tOI'uE
`CH-'El'd']E'|I'
`
`11 Jttrsorption and Cain
`M:Iso1'_ption and Gain on a Homogenoottsly Broadened Radiative
`Transition {Lorenuian Frequency Distributiont
`Gain Coeffiisieat and Eli Iratlated Emission Cross Section for
`
`Homogeneous Broadening,
`fittlsorption and Gain on an Inho rnogeneousiy Broadened Radiative
`Transition {Doppler Broadening with a Gaussian Distrib1.tIion'|I
`Gain Czoeffiiciont and Stimulated Emission Cross Section for
`
`Doppler Broadening
`Staasnoal Weights and the Gain Equation
`Relationship of Gain Coeffitient and Sti ITL1.titlI.Eti Emission
`Cross Section to .-ibsorpli on Coefficient and .5Lbsoi'pti on
`Cross Section
`
`11 Population Inversion t.-Nicol.-ss"ar_\-' Condition for a laser]
`1.’: Saturation Ettensity Ifititicient Condition for a Laser]
`T.-1 Dtt't'EItlllllI.t!I'I'I. and t3‘.rowtl1 of :1 Laser Beam
`Growfn of Beam flor a Gain Medium with Homogeneous
`Broadening
`Shape or Geometry of Amplifying ]'t"IEd.ium
`Growth of Beam for Doppler Broadening
`15 Expoltontziat Gmwtlt Factor {Gain}
`?.tS Threshold Requirornents for a Laser
`Laser with No Mirrors
`Laser with One Mirror
`Laser with Two Mirrors
`REFERENCES
`PROBLEMS
`
`20]
`20-4
`205
`2015
`El}?
`EDS
`209
`Etfl
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`311
`EM
`215
`216
`21'?
`22]
`22]
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`225
`225
`225
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`225
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`23!]
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`23!
`21:2
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`233
`234
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`233
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`24-9
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`253
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`xii
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`CONTENTS
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`255
`255
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`253
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`253
`253
`26!
`26!
`26!
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`26-6
`263
`2153
`2'30
`232
`2'33
`2'33
`2'3-S
`2'39
`2'39
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`230
`232
`234
`234
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`233
`233
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`290
`290
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`2 2
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`92
`293
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`295
`293
`30!
`30-1
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`LASER OSGLLATION ABOVE THRESHOLD
`lI|"n"ER"t'TE'W
`3.1 Laser Cain Saturation
`
`Rate Equations of the Laser Levels That lmclude Stimulated
`Emissi on
`
`Population Densities of Upper and Lower Laser Levels widl
`Beam Present
`
`Su'rall—3Eg,na.l Gain Eoefficient
`Saturation of the Laser Gain above Threshold
`
`3.2 Laser I-il-eam Growth I1-e_1rond the Saturation lmecrtsity
`Change from Exponential Growth to Linear Growth
`Steady-S Late Laser Lnlensity
`3.3 Optimization o‘l' Laser Output Power
`Optimum Output Minor Transmission
`Optimum Laser Clutput Intensity
`Estimating Optimum Laser Output Power
`3.4 Energy Exeltange between Upper Laser Level Popuiatiou and
`Laser Photons
`
`Decay Time ofa Laser Beam -».I.-'itl1in an Dpfiea] Cavity
`Basie Laser CE.‘t"il'jI' Rate Equations
`Steady-S Late Solutions below Laser T‘nres'nold
`Stead}-'—S Late Clperati on above Laser Threshold
`3.5 Laser Output Fluctuations
`Laser Spiking
`Relaxation Dseillauons
`
`3.-E Laser .-ltmplifieis
`Basie Amplifier Uses
`Propagation of a High—Power. Short-Duration Gptieal Pulse through
`an Amplifier
`Saturation Ertergy Fluenee
`Arnplifyi ng Long Laser Pulses
`Amplifying Short Laser Pulses
`Comparison ofE.ffieient Laser Amplifiers Based upon Fondarnental
`Saturation Limits
`
`Minor Array and Resonator {flegeiierativel Amplifiers
`REFERENCES
`PRDBLEJLIS
`
`REQUIREMENTS FOR OBTAINING POPULATION INVERSIONS
`DVEEHEW
`
`‘ELI Inrersittus and Tm:-Level Syrians
`9.2 Relative Decay Bales — Iiatliati-re versus Cnllisioual
`9.3 5l.e::ui:.-'-Stale Inversion: in Tlmee- and Four-l_.e1.'e] 53.'stt-nus
`Three -Level Laser widt die Irttennediate level as The Upper Laser
`Level
`
`T'l'II-ee-L.eL'el Laser with die Upper Laser Level as the I-}ighest1.ei-El
`Four-Lei-til Laser
`
`‘J.-I Transient Population Imrel-§'ons
`
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`

`
`CDNIENTS
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`9.5 Proct:-sses Thasl lnitiliit or Destmy Inversiorts
`Radiation Trapping in Atorrts and Ions
`Electron Collisional Thermalizaflon of Inc Laser Levels in Atoms
`and lens
`
`Comparison of Radiation Trapping and Electron Collisional Mixing
`ill a Gas Laser
`
`Attsorpti on wititin Inc Gain Medium
`REFERENCES
`PRCII-[Ell-IS
`
`113 LASER PUMPING REQUIREMENTS AND TECHNIQUES
`CWEl‘.'I.TIE'iI'lt'
`
`HM Excitation or Pumping Titre-sltold Reqtiresnents
`10.1 Pumping Pathways
`Excitation by Direct Pumping
`Excitation b_1.r Indirect Pumping {Pump and Transfer}
`Specific Pump—a:nd-Transfer Processes
`I|.l'.3- Specific Excitation Parameters Associated with
`Optical Pumping
`Pumping -Geometries
`Pumping Reqttirernents
`A Simplified Optics] Pumping Apprmtimation
`Transverse Pumping
`End Pumping
`Diode Pumpillg of So1id—Sta1e Lasers
`Characlzeti cation ofa Lascr Gain Medium with Optical Pumping
`{Slope Efliciency)
`IIIL4 Specific Excitation Parameters Associated with
`l"at'=tit:le Pumping
`Electron Collisional Pumping
`Hear}-' Particle Pumping
`A More .-ftcctlratc Description ofEle:tron E.I{'il3liDt|1 Rate to a
`Specific Energy Level in aGas Discharge
`Electrical Pumping of Semiconductors
`REFERENCES
`PRU!-[£|'tI1S
`
`l..fl.'SER RESONATORS
`SECTHJN 4.
`11
`l...fl5-EN CAVITY MODES
`OYERITIEW
`I‘l.l Introduction
`
`I11 Longitudinal Laser Cat"!-_t' Mod-es
`Fabr_',I—Pcrot Resonator
`Fabrg.-—Perol E‘a1.-'it}' Modes
`Longi tudinal Laser Cavity Modes
`Longinidinal Mode Ntunbcr
`Requimrnenls for me Ilcvelopment of Longitudinal
`Laser Modes
`
`3|Z|"i‘
`3-03
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`31]
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`315
`3it.‘r
`3E9
`3-}?
`322
`322
`322
`324
`324
`32'?
`3-31]
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`339
`339
`342
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`350
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`3-52
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`355
`355
`359
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`3-59
`351
`363
`364
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`3?]
`3T1
`3?]
`322
`322
`37''?
`38-1]
`3-80
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`382
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`xiv
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`CONTENTS
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`11.3 Tr'a.nsrr'ersr.- Laser Ca1r'Il_1.' Modes
`Fr-esn:e1—K_irehhoI'l' DiI'ft:;etion Integral Formula
`Development oI'Transverse Modes in a Car-ily with Plane-Parallel
`Mirrors
`
`Transverse Modes Using Curved Mirmts
`Transverse Mode Spatial Distributions
`'I'1'a.nsr-'erse Mode Frequencies
`Gaussian-Shaped Transvetrse Modes wirzlrin and beyond Ilre
`Laser Cavity
`11.4 Properties of Laser Modes
`Mode Characteristics
`Effect of Modes on due Gain Medium Profile
`E‘.E.FERl-ENCES
`PROBLEMS
`
`12 STAELE LJISER RESONATORS AND GAUSSLAN BEAMS
`DVERVIEW
`12.! Stable '|I':tr1.'ed Mirror Cavities
`Curr-eel Minor Cavities
`AECD Matrices
`
`Cavity Stability Criteria
`11.2 Properties of Carrmian B-earns
`Propagation ofa GfliJS51EL!'l Beam
`Gaussian Beam Properties of T\r«'o-Mirror Laser CaviLies
`Properties of Specific Two-Mirror Laser Cavities
`Mode Volume crfa l-Ierrnite—Gaussiar1 Mode
`
`11.3 Properties of Real Laser Bearrzis
`11.4 Propagation of Gaussian Beams l_.'singA.BCB Matrices —
`Complex Bean] Parameter
`Complex. Beam Parameter Applied to a Two-Minor Laser Cavity
`REFERENCES
`PROBLEMS
`
`13 SPEEIM. LASER CA'.I"lTlES AND CAWTY EFFECTS
`OVERVIEW
`13.1 Ulrstah|eResona1urs
`
`1.1.2 Q-Su-‘it-eliing
`General Description
`Theory
`Meflrods of Producing Q-Switching within a l..aser{'a1.'ir.:.r
`1.1.3 l_‘.ain—SIn'tr:l:ring
`13.4 Brliodre-Loelrirrg
`General Description
`T|'.Ieo:ry
`Techniques for Producing 5.-‘Io-|:le—Loc:lring
`13.5 Pulse Slrorleriog Techniques
`Self-Phase Modu laiion
`
`Pulse Shortenirrg or Lengthening Using Group Velocity Dispersion
`Pulse Compression l_SI1ortea1ir1g]I with Gratings or Pris rns
`Ultrashort-Pulse Laser and Amplifer System
`
`384
`385
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`592
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`410
`41 I
`412
`41'?
`42l
`423
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`425
`428
`432
`43 2
`434
`434
`434
`439
`439
`44l
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`450
`45 I
`45 l
`45 l
`456
`4&2
`4153-
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`46?
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`CONTENTS
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`13.6 Ring Lasers
`Monoidiic Unidirectional Single-Mode Nd'.YAG Ring Laser
`Two—!l.-'lirror Ring Laser
`13.1’ Complex Beam Paraineter .-!Ln:iI_1.'s'B .-applied to Multi-Mirror
`Laser Cavities
`
`Three—Mii'.ror Ring Laser Cavity
`Three— or FuLLr—Mirre-r Focused Cavity
`l3.B Cavities fior Producing Spectral .'H':i.n'ewing of
`Laser -Dutpul
`Cavity wilb Additional Fabr)-—Perol Etalo-n for ?\ls.rrew—F1'eqLtencj.'
`Selection
`
`Tunable Ca\'iT.}'
`Broadband Tunable cw Ring Lasers
`Tunable Cavity for l.lllIfE.1'I3.|.'I°0'|A-'—l:J.'EI:Z[1.l£.‘.l'|\C}" Output
`Disnibuted Feedback {D133} Lasers
`D'isIribi.1te:d Bragg Reflection Lasers
`I33 Laser Cavities Requiring Sm:Il1~Dia:neter Gain Regions —
`Astignialically Compensated Cavities
`[3.1fl Waveguide Cavities for Gas Lasers
`REFERENCES
`Pmsti-zais
`
`SECTION 5. SPECIFIC LLASER 5‘I"5TE MS
`
`14 LASER SYSTEMS |H"|:I"DL‘uI"lI|'IlG LGW-DENSITY I."-ulilhl MEDLA
`GVEZILVIEW
`14.1 A1oI:i1ieCasLa.ee1s
`lntrod-ueiion
`I-Iei'Iu.m—Neen Laser
`
`General Description
`Laser Slructure
`Excitafion Mechanism
`
`Applicadens
`Argon Ion Laser
`General Description
`Laser Striicture
`Excitafion Mechanism
`
`liryjxon [on Laser
`Applications
`Heliu.m—'E'admium I.a.-oer
`
`General Descripliori
`Laser SI:n.1c1'u.re
`Eiicitafion Mechanism
`
`Applicafiens
`Copper Vapor Laser
`General Description
`Laser SI:n.1ctLu'e
`Excitafion Mechanism
`
`.!Lpp1icati-ens
`
`453
`459
`4T"fl
`
`4?!)
`
`41"!)
`4T3
`
`4T"E
`
`«HS
`
`-HE
`480
`48!]
`4EI
`434
`
`484
`485
`436
`483
`
`491
`-’-lgl
`49I
`491
`-192
`
`492
`493
`494
`
`497
`49'?
`497
`493
`499
`
`500
`5rE|'l
`SDI
`
`SDI
`SEE
`504
`
`505
`505
`505
`507
`507
`
`509
`
`
`
`
`
`
`
`

`
`CONTENTS
`
`J42 1'5-iolecular -Gas Lasers
`Introduction
`Carbon Dioxide Laser
`
`Geruerai Descliption
`Laser SIruI::mre
`Excitalicrn Mechanism
`
`Applicalio-ns
`E:|:c1'rncrLasHs
`
`Genera] Desoliplion
`Laser Slrucrure
`Excitalion Mechanism
`
`Applicalioris
`Nitrogen Laser
`Genesai Dosc.Ii|:Ition
`Laser Slrucmrc and Eaioilation Mechanism
`
`Applications
`Far-lJ|.frsu'ed Gas Lasers
`
`General Descliption
`Laser Smrcmre
`Excitalzi on Mechanism
`
`Applicalions
`C'.'I1eIniscaI‘.I.aseI's
`
`Geruerai Descliption
`Laser Structure
`Excitation Mechanism
`
`Applications
`El-1-.3 X-Ray Plasma Lasers
`Introduction
`
`Pumping EI'l£!'g_1_.I' Requirements
`Excitalion Mechanism
`
`Optical C‘:n-ities
`X—F.:-my Laser Transitions
`Applicalicnris
`14-.4 Fnce-Electrrm Lasers
`Introduction
`Laser Slrucrure
`
`Applicalions
`REFERENCES
`
`15
`
`LASER SNSTEMS IHVCHLVING HIGI-|—DEN5l'|"'|" GAIN MEDIA
`DVEIYIEW
`
`15.! flrganic Dye Lasers
`Introduction
`Laser SIruc1Jn'e
`Excitnlicrn Mechanism
`
`Applications
`15.2 5r.I]'Id-Static Lasers
`Introduction
`
`5113
`519
`511
`511
`5| I
`5 I5
`5 I5
`5115
`5116
`5 I2’
`513
`521}
`521]
`521]
`521
`522
`522
`522
`523
`523
`524
`52.4
`524
`524
`524
`525
`525
`525
`525
`523
`532
`532
`532
`535
`535
`536
`53?
`532'
`
`539
`539
`539
`539
`541]
`543
`544
`545
`545
`
`
`
`
`
`
`
`

`
`CONTENTS
`
`xvii
`
`Ruby Laser
`General Descripfion
`Laser Structure
`Excilation Mechanism
`
`Appli cations
`NI.-od_1'mium "1'.-91C and Class Losers
`General Description
`Laser 5I.rucLu.re
`Excitation hiechanisin
`
`Applioafions
`Ncud_vuIium:'!t'LF Lasers
`General Description
`Laser SI1'I1cuJ.re
`Excilarion Medunism
`
`Jhppli cations
`Neod_1.1nium:‘!t'flrium ‘I-'an:ui:Itc I Z\id:"¢"u"C|_1} Lasers
`General Description
`Laser E-l1'ucLu.re
`Excitation Mechanism
`
`Jtppliealions
`'!t'flcI'hi|InI:Ye!LG Lasers
`
`General Descripiion
`Laser Structure
`Exci lation ii-'!eci1anism
`
`Jhpplj cations
`Alexandrite Laser
`
`General Description
`Laser Structure
`Excilsalion Meciuulism
`
`Applicafions
`Titanium Sapphire Laser
`General Description
`Laser SI.rucu.1.re
`Etci lation Mechanism
`
`Appli cations
`C|srom'Iu:a.1 IJS AF and I.-iC.‘-VLF Lasers
`
`General Description
`Laser SlrucLI.u'e
`Exci lotion Mechanism
`
`Aipplioalions
`Fiber Lasers
`
`Genetral Descripfion
`Laser Structure
`Etci Lation ii-'!echanism
`
`Applicalions
`Color Cc|1terI.ascrs
`
`General Description
`Laser Strucuare
`
`54'?
`54'?
`
`549
`559
`551]
`551
`553
`554
`555
`555
`5515
`5515
`55'?
`55?
`55'?
`55'?
`553
`558
`559
`559
`551]
`55!]
`55]
`552
`552
`553
`553
`554
`555
`555
`555
`55'?
`553
`553
`558
`553
`559
`5?fl
`5?fl
`5?D
`5?]
`5?]
`5?2
`5}'3
`5?3
`5?4
`
`
`
`
`
`
`
`

`
`rnriii
`
`CONTENTS
`
`Excitation Mechanism
`
`Applications
`15.! Semiconductor Diode T.:rs«ers
`[EIIIDCiLK.'|2iDl!.
`
`Four Basie Types of Laser Materials
`Laser Slnleture
`
`Frequency Control of Laser Output
`Quantum Cascade Lasers
`p—Doped Germanium Lasers
`Excitation Mechartiarn
`
`Applications
`REFERENCES
`
`SECTION «B. FREQUENCY-MULTIPLIEATIOH OF LASER BE.MrIIS
`16 FREQUENCY MUl.TiFL|CATiDl'i OF LASERS AND OTHER
`NONLINEAR OPTICAL EFFECTS
`Oil’-II|l¥'IE‘H'
`
`I6.I Ware Propagation in an Anisotropic Crystal
`I62 Polarization Response of Materials to Light
`IISJ Second-Order Nonline:1r Clplical Pnoce-sses
`Second Harmonie Generation
`
`Stan and Differenoe Freqtteney Generation
`Dpljeal Pararnelrie Dseillafion
`I6.-I Third-Order Fiorrlirteer Uptictrl Processes
`Third Harmortic Generation
`
`lntensit}-'-Dependent Refiaetwe Index — Self-Focusing
`I65 Nonlinear Optical Eflalerials
`I646 Phase Matching
`Description of Phase Mabchirrg
`Aohievi rig Phase Maloiting
`Types of Phase Matching
`II':i.T Saturahl.-e Absorpiion
`I63 Two-Photon Ahsorpljon
`IISJ} Slirnlfluterl Human Sralloring
`lti.1fl Harmonie Gerteration in Cases
`RFIERENCES
`
`Appendix
`index
`
`574
`57-6
`57-6
`57-6
`579
`SE!
`59!
`592
`59-!
`594
`596
`59?
`
`60!
`60!
`60!
`603
`60-1
`
`605
`60?
`
`I503
`609
`Ell]
`till]
`fill]
`6|3-
`6|5
`6I5
`6|?
`6|B
`6|‘?
`6|?
`
`52!
`625
`
`
`
`
`
`
`
`

`
`1 I
`
`ntroduction
`
`OUEEWEW A laser is a device Ihat amplifies light
`and pmdmres a highly diI1ectinnal_ high-intensity
`beam Ihatrnostoftenhosavetypure frequency or
` . ltcomesinsiees ranging from approx-
`intatelyoltetenlhtliediamelerofaltnrnanhairto
`Ihesieeofavetylasgebuilding;.inpourersrangir|g
`from I04‘ to lflm‘ ‘W, and in tuavelengtlis ranging
`irorntl1emicro'uravetotl|esoft—X-rayspectradmgiclrs
`wiflteolrespondingfroqpt-.|1cica from EU" to Ill" Hz.
`Lasers havepulseenezgieaas highas ll]‘l and pulse
`duiationsassholtmfi X IIl"5 s Theycaneasily
`iiill holes in the most durable of malerialsand-can
`
`oiexinenee!
`
`welddeiaclnedretiriasulililinthelnlrnaneye. They an:
`alcey eompnnent nfsmne nfour most mttlem com-
`munication systemsand a1e1he"“pbenograplI needle"
`oioureolnpoctdisc playels. They perform heat1Ie:rI-
`rnenstofhigh-atrength materials. mehas the pistons oi
`ourantornobile engines. and provide a special surgi-
`cal knife for manyI'.ypesoin1eIfical pn:I::edures_ They
`act as targetdesignstors for rnilitasytveapons andpro-
`vide for Ilse rapid cheek-out we ltave come to expect
`at the supermarket. Wltal a rernaEal:rlelangeofclral-
`aelcristics foradevice Ihatis in only its liflh decade
`
`INTRDDLICTIJN
`
`There is nothing magical about a laser. It can be thought ofasjust another type
`oi light source. Itcertainly has many unique properties that make it a special light
`source. but tllcae propeniescan be understood without toowledgeof sophticaieti
`rnathematical techniques oreomplca ideas. It isthe objective oithis teat toesplain
`theoperationoithelaserina simple, logical approach thatbuilds from one cotn-
`eepl In the ne:Ittasthe chapters evolve. The concepts, M they are developed, will
`be applied to all classes of laser rnflerials, so that the reader will develop a sense
`of the broad field of lasers while still acquiring the capability to study, design. or
`simply understand a specific type oflaser system in detail.
`
`DEFINITION OF THE LASER
`
`'I'he word laser is an acronym for Light Amplificilion by Stimulated Emiasi-on oi
`Radiation. The laser makes use of prooesses that increase or amplify light signals
`aflcrthose gnals have been genented by other means. These pI1o-ceases include
`(I) stimulated emission, a natunfl effect that was deduced by eonsiderations re-
`lating to tltennodynamic equilibrium, and {2} optical feedback {present in most
`
`
`
`
`
`
`
`

`
`IHTEODLICTION
`
`Optical reaonalor or cavity
`A
`
`Amplltyfmg medium
`
`
`
`‘Figure 1-1 Sitnplrfiad
`5Cl'tEt'l1El:lC oH_-fpical laser
`
`Fully re-tlecting
`mirror
`
`Parllallv transmitting
`mirror
`
`lasers) that is usually provitletl by rnirm-rs. Thus, in its simplest form. a laser con-
`sists of a gain or arnplifying me-diurn {where stimulated emission octatrs]. and a
`set of mirrors to feed -the light back intoxhe amplifier for continued growth of the
`developing beam, as seen in Figure 1-1.
`
`SIM PI.lCl'I'Y CF A LASER
`
`The simplicity ofa laser can be understood by considering the light from acartdle.
`NDI!'I'l'I&lljT, a burning candle radiates light in all directions, and lltettefore illumi-
`nates various ohje-ots equally ifthey are equidzistant front the candle. A laser takes
`light that would normally be emitted it} all directions, such as [mm a candle, and
`concentrates that light irto a single direction. Thus, if the light radiating or all di-
`rections from acatudie were concentrated into a single beanzt of the diameter of the
`pupil of your eye fapproxirnately 3 mm}, and if you were standing :1 distance of
`I II]. from-dte candle, then the light intensity would be l,0l]l],lJIII times 39 bright as
`the light that you non'na.ll1.r see radiating from the candle! Tltat is essential.l}r the
`underlying concept ofthe operation of alaser. However, acandle is not the kind of
`medium that prochices arnplificalion, and this there are no candle lasers. It takes
`relatively special conditions within the laser rnediutn for arnplificafion to occur,
`but it is that capalztility oftalring light that would normally radiate from a source in
`all tlirectzicuts — and concentrating that light into a beam traveling in a single direc-
`tion — that is involved in making a laser. These special conditions, and the media
`within which Huey we ]:l'oducetl._ will be described in some detail in this look.
`
`UI'tIGLl'E FFlOPER'l1E5 OF A LASER
`
`T'lte beam of light generated by a typical laser-can have many properties that are
`unique. When comparing laser properties to those of other light sources, it can
`be readily recognized that the values of various parameters for laser light either
`greatly exceed. or are tnttch more restrictive than the values for many common
`light sources. We never use lasetsfor street illumination, orfor illumination within
`our houses. We don't use lhetn for searchlights or flashlights or as headlights in
`
`
`
`
`
`
`
`

`
`INTRODUCTION
`
`our cars. Laseas generally have a narrower frequermy cfislributzion, or much higher
`intensity, or a much greater degree of oollirna'I:'Lo11. or much shorter pulse duration.
`titan that available from more oommon types oflight sources. Therefore. we do use
`them ili compact disc players, in supermarket eheok—out scanners. in su.rveg.ri.ng in-
`stn: meats, and in medical applications as a surgical knife or for welding detached
`retinas. We also use them in oornmuniealions systerns and in radar and n1il.i.la.ry
`targeting applications. as well as rnany other areas. A laser is a specialized light
`source that should be used an.l_v when its unique properties are required.
`
`THE LASER SPECTRUM END W'A'nI"ELENGTI'lS
`
`A portion ofthe E:l1E.Cl.I'Dl.'I'lE:gl1El‘.lC radiation spectrum is shorvn in figure 1-2 for the
`region covered by eur1'en'Il_v e:ItisliJ1g lasers. Such lasers span the wavelength-range
`from the farinfrared part of the spectrum (J. = I JIICI gun} to ‘the soFl—X—ray region
`0:. : 3 rim), ll'lE:n3lJ-}' co-verilig a range of wavelengths of almost six orders ofm.ag—
`nitude. There are several types of units that are used to define laser wavelengths.
`These range from micrometers ormicrons (tam) in the infrared to nanometers l_nnf_I
`and a.ngstroms[2lL}iIitl1e visible. ultraviolet [UV ‘Jr. vacuum ultraviolet {VLTV ]. ex-
`treme ultraviolet {EUV or XUV }, and soft—X—ray {SXR} spectral regions.
`
`WAVELENGTH IJHITS
`
`ltsrn = 104“ mi
`1.-x: In-H’ n1:
`1 nm = to-9 1:}.
`
`Consequently, I micron titre} : IELDCD angstroms Lit] : 5l.|l00na.nometers {am}.
`For example. green light has a wavelength of 5 2-: ll]‘7 111 = [L5 pm = 5.13410 lat =
`SDCI Iim.
`
`Figure ‘I-I Wavelength
`range ofvafious lasers
`
`HF
`
`CD
`
`I39
`
`..
`
`..
`
`
`
`Ar..
`
`FIR:I.::.ar:
`n
`
`.
`
`,
`
`CC--‘.
`
`Ha—H:e
`
`M:
`Ruby
`KI'F
`hie-Ne
`N-\:|:‘|'.¢I.G
`Ho-Ea
`
`$€|lH'l-Flag.
`La.-aars
`-..-. ..--
`
`nu’-
`1._.mz93
`SH! ill-Rays
`Ulravnlel
`"t'i:n-baa
`lnlrared
`Fan I-nlrared
`:__'_jjj.'__j_'_.. __l......:j_jl.j _.__.
`3£I|.-m mum
`3pm
`1pm an-Dnrn
`‘Iounm 3tJnrn
`tclnm
`-h-
`A. ::—
`
`-——-- ENEFIICi‘1"lL'l%I]-
`
`..
`
`
`
`
`
`
`
`

`
`IIVITHODLICTEON.
`
`WAVELENGTH EGIONS
`
`Far infrared: 1D to LCIDCI trrn;
`middle infrared: l to It] prrn;
`near infrared: 0.? to lttm;
`visible: {14to ll? _r.rrn. or 401110 TDD nrrr:
`ultraviolet: 0.2 to I14 ,r.r.n'L or EDD to 4130 nrrr;
`vacu urn ultraviolet: 0.] to 0.2 rim. or 100 to 200 nm:
`estr'ern:e ultraviolet: I0 I13 100 nm‘,
`soI't X—rays:
`I run to approximately 213-3!) nm {some overlap with ELf"rI"}I.
`
`A BRIEF HISTORY OF THE LASER
`
`Charles Townes took advantage of the stimulated emission process to construct a
`nricrowave amplifier, referred to as a eraser. This devioeproduced a coherent beam
`of microwaves to be used for DDII1II'Il.IllIl.CflIlCtl'l5. The first rnaser was produced in
`anrrnorria vapor with the inversion between two energy levels Ihat produced gain at
`a wavelength of 1.25 cm. The wavelengths produced in die maser were compara-
`ble to Ihe dirrrensions of the device. so errlrapolarinn tn the optical regime — wl'rene
`wavelengths were five orders ofrnagnitucle sn'ialter— was not an obvious extension
`of that work.
`
`in I953, Townes and Schawtow published a paper concerning Theirideas about
`extending the rnaser concept to optical frequencies. They developed the concept
`of an optical arnplitier surrounded by an optical mirror resonant cavity to allow for
`growth ofrlre beam. Townes and Schawlow each received a Nobel Prize for his
`work in this Held.
`
`In 19150. Theodore Maiman of Hughes Research Laboratories produced lire
`firsl laser using a ruby crystal as the amprlifier and afiashlamp as the energy source.
`The helical flashlarrrp surrounded a rod—shaped ruby crystal, and the optical cavity
`was formed by coating the flattened ends ofthe ruby nod w'itJ'r a highly reflecting
`material. An intense red beam was observed to emerge from the end ofthe rod
`when the flashlarnp was tired!
`The first gas laser was developed in l9IErl by A. Javan, ‘W. Bennett. and D. Har-
`riott of Bell Laboratories. using a mixture of helium and neon gases. At lire same
`laboratories. L. F. Johnson and K. Nassau demonstrated the first neodyrniurn laser,
`whichhassince becorneorreofthne rrrostreiiable lasers available. This was followed
`
`in 1962 by the first semiconductor laser, demonstrated by R. Hall at the General
`Electric Research Laboratories. In 1963, C. K. N. Patel of Bell Laboratories dis-
`covered the infrared carbon dioxide laser. which is one ofthe most efiicient and
`powerful tasers available today. Later that sa.rne year. E. Bell of Spectra Physics
`discovered the first ion laser. in mercury vapor. [:1 1964 W. Bridges of Hughes Re-
`search Laboratories discovered-Ii're argon ion laser. and in I966 W. Silfvast. G. R.
`Fowles. and E. D. Hopkins produced II1e first blue lrcliun1—cadn'riur'n rnetal vapor
`
`
`
`
`
`
`
`

`
`INIIDDLICTIDH
`
`laser. During that same year, P. P. Soroltin and I. R. Lanitard of the IBM Research
`Laboratories developed the first liquid Iaser using an organic dye dissolved in a sol-
`vent. thereby leading to the category of broadly [unable lasers. Also at that-time.
`W. Waiter and eo—worl»'.ers at TRG reported the first copper vapor laser.
`The first vacuum ultraviolet laser was reported to occur in molecular hydro-
`gen by R. I-[odgsoa of IBM and independently by R. Waynant et al. of the Naval
`Research Laboratories in 1970. The lirst of the welt-known rare-gas—ha|.ide es-
`cimer lasers was observed in xenon fluoride by I. J. Ewing and C. Brat: of the
`.rltvco—Evetett Research Laboratory in I935-. In tiiat same year, the first quantum-
`well laser was made in a gallium arsenide semiconductor by J. van det Ziel and
`co-worlters H. Bell Laboratories. in 19'i'6. .l. M. .l. Madey and co-workers at Stan-
`ford University derrtonsuated the first free-electron iascralnplifier ou_p-erating in the
`infrared at the C0; laser wavelength. In l9TI'9, wailing and co-workers at Allied
`ChernicalCoq:IJration obtained broadly tunable laser ourpotfroma so-lid-stale laser
`material called alexandrite. and in I935 the first so'ft—X—ray laser was successfully
`demonstrated in ahigbly io-nizedseleni uni plas1'na'byD_ Matthews and aIangenum-
`ber of oo-workers at the Lawrence Liverrnore Laboratories. In '19‘Bti, P‘. ]'vIo-ulton
`discovered the tzitanium sapphire laser. In l991, M. Hasse andco-worltcrs devel-
`oped the fi.rst b|ue—green diode laser in Znfle. [11 I994, F. Capasso and co—workers
`developed the quantum cascade laser. In 1996, S. Plaltamuta developed ‘d'K.'. first
`blue diode laser in GsN—based materials.
`In I961. Font and. Li described the existence of resonant transverse modes in
`
`a laser cavity. That same year. Boyd and Gordon obtained solutions of the wave
`equation for confocal resonator modes. Ll-nstable resonators were demonstrated
`in I969 by Krupke and Sooy and were described theoretically by Siegman_ @-
`switching was lirst obtained by l‘v1cC|1.tng and I-lellwarth in 1962 and described
`later by ‘Wagner artd l'_.engyel. The ‘first mode-lo