LASER FUNDAMENTALS
`
`SECOND EDITION
`
`WILLIAM T. SI LFVAST
`
`School ul Oplits I CRECIL
`Lhilmlsily of Centrd Florida
`
`CAMBRIDGE
`IINIVERSITY PRESS
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`(cid:36)(cid:54)(cid:48)(cid:47)(cid:3)(cid:20)(cid:19)(cid:19)(cid:26)
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`ASML 1007
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`

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`PUBLISHED BY THE Fl 5‘|"N']HZ.h'l'E OF THE. UNIVERSITY l}FCfl.kIBI]IIIE
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`ICIIIEEES2
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`

`
`Contents
`
`Pr:-_.IiIc£ Io Ike Second .E'£l'i£imr
`
`Prefirce to the First‘ Edition
`
`Jlcinowfetflgywcnts
`
`INTRODUCTION
`UVEILVIEW
`Intro-Iluclion
`Deliilion of llle IJEET
`
`Simplicily 0|’ 2 Laser
`Unique
`of :| Laser
`The Laser Spectrum and Hlawlerrgtlls
`A Brief I-Iislory ofllle Laser
`D1wt~I'I"Ie'tr of the Book
`
`SECTION 1- FLINDAIIEIITIL WAVE FIIDPERTTIE5 BF LIGHT
`
`Z WAVE NATURE OF LIGHT — THE INTERACTION CIF LIBGI-IT
`WITH MATERIALS
`1:w'EJt\rII:tII'
`
`2.1 Maxi-ncIl’s Eipntions
`2.2 II'Ia:I:I|-roll’; Wave Eqoalions
`Maxwell‘: ‘Wave Equations for a Vacuum
`Solution ofthc General Wave Equation — Equivalonoc of Light and
`E c lladjation
`Watrc Vcloccitjg — Phaac and Group Vclorflics
`Gcnacralizcri So-Iulion oftltcwatrc Equation
`Transverse Eloctroroagoctic Waves and Polarized ]..igltt
`Flow of Eloctrontagrtctic Ellcrgy
`Radiation [mm a Point Source (Electric Dipole Radiation]
`2.3- lntauclion of Eledroruagrvrlic Radiation {light} wih Matt-er
`Speod of Light in a Medium
`Maxwell‘: Equations in a Medium
`Application ol'Ma.I'.w£:il's Equations to Dielectric Materials —
`Lascr Gain Media
`
`Complex Index of Rofraclzion —
`Absorption and Dispersion
`
`Constants
`
`page xi:
`xxi
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`xxiii
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`EH3EHEBEEECTIGEflua-.a~au«.n.u..w.na-—-——-—
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`
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`
`
`VII
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`

`
`CONTENTS
`
`Estimating 1'-‘anziclae Densities oflflatetials for Use in the
`Dispersion Equations
`L-I Coherence
`
`Temporal Coherence
`Spatial Coherence
`IEFEIENCE
`IIIJIILEIIS
`
`SECTION 2. FIJHDIHEHTAL CHJAHTUH FIIDPEIITIES OF I.I.~'nHT
`
`I-I
`
`I'AR'Il£I.E NAII'l.ll1E OF LIGHT — DISCRETE ENERGY LEVELS
`\lIII"EI‘I".IE'W
`
`3.] Bohr Theory olthe Ilydrogen Alum
`Historical Development ofshe Concept of Discrete Energy Levels
`Enesgy Lelnels of the Hydrogen Atom
`Frequency and Wavelength of Emission lines
`Ionization Energireaand Energy levels o-flona
`Photons
`
`offittoulit Fnergy I.e'neIs
`3.! Quantum
`Wave Nature. ofPaniol:es
`
`Heisenberg lJncerta.int3r Principle
`Watre'I'lteoI]r
`Wave Functions
`Quantum States
`The Srlirfitlinger ‘Wave Equation
`Energy and Wave Function for d'!.I'.'G!lJIItl.l2I State of the
`Hydrogen Atom
`Excited States of H3-tkogen
`Allowed Quanturu Numbers for Hydrogen Atomwave Functions
`3.] Angular Monltnltll ti Alums
`Orbital Angular Momentum
`Spin Angulx Mornentum
`Total Angular Molum
`Jul Erterg: lmrels Ago-rialed with Due-Electron Atoms
`Fine Stnuzture of Spectra] Lines
`Pauli Exclusion Principle
`J5 Periodic Table ol‘ the Elements
`
`Quantum Conditions Associated with Multiple Electrons Attached
`H: Nuclei
`
`Shonhand Notation for Electronic Configurations offittorus Having
`More Than Clue Electron
`
`3.6 Fnergy Levels uI‘l'tItlli-Eleclmu Atoms
`Eneegy-l.eIreI Designation for Mulli-El‘.ectn1n States
`Ruseell—Sauru:Ie:s or LS Coupling — Notation forEnetg3r levels
`Energy Levels Associated with Two Electrons in Unlilletl Shells
`Rules for Obtaining 5, L. and J for L5 Coupling
`Degeneracjr and Statistical Weights
`Coupling
`Iaoelectronic Scaling
`
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`COHTEIT5
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`n.sn:amc.ss
`FROILEIIS
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`-I
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`IIADIATNE TIIAHSITIJNS AND EIIIISSIDN LINEWIDTH
`onrsiwlew
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`4.1 Dora} of F.:n:'lted Stalos
`R.adiaIi\reDeca3r ofE:rciteriStates o1'IsoIate:rIAtoms—
`Spontaneous Emiion
`Spontaneous Emission Decay Rate — Radiative Transition
`Probability
`Lifetime ofa Radiating Electron — The Electron as a Classical
`Radiating Hamtonic Oscillator
`Nonradiative Decay of the Excitai States — Colfisional Decay
`-1.2 Emimion Bmadering and Iinewidlll Due to Radiative Decay
`Classical Emission l..inenridxl1 of a Radiating, Eliectron
`Natural Emission Linewidllr as L’IerIauceri by Quantum Meclranics
`(lu'Iini.ntorn Ljnewirlthjl
`4.3- Additiomd Faiission-llroadening Processes
`Broadening Due to hlomadialiue (Collisional) Decay
`Broarlening Due to Dephasing Collisions
`Allnrphous Crystal Brumlening
`Doppler Broadening in Gases
`Voigt Lihape Pmlile
`Broadening in Gases Due to lsolope Shifts.
`Comparison of Various Types ofE|n.ission Broadening
`-I.-4 Quanltli Mechanical Destriplion of Ratlizrtirtgfitonts
`Electric Dipole Radiation
`Electric Dipole Mani: Element
`Eiectric Dipole Transition Probability
`Oscillator Snengdi
`Selection Rules for Electric Dipole Transitions l[I1:"lJll".lIlg Atoms
`will} a Single Electron in an Unlilierl Subshell
`Seliection Rules for Raiialiue Transitions Involving Atoms with
`More Than One Electron in an Unfillietl Subsltell
`
`Parity Selection Rule
`[neflicient Radiatisre Transition: — Electric Quadrupole and Other
`Higher-Order Transitions
`IEFEIENCEE
`I'R0lI.EMS
`
`5 ENERGY LEVELS AND IIAEIATWE PROPERTIES OF MDlECl.II.ES.
`LIEIUIDS. AND SOLIDS
`onrsiwlew
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`5.] Hlolrcular Energy Levels and Spot.-Ira
`Eatergjjr Levels of Molerailes
`Classification of Sirtple Molecules
`Rotational Energy Levels of Linear Molecules
`Rotational Energy Levels of fi'l2l'Il2l'BS.I'l1I.‘»—'['l:|]2Ir Molecules
`Selection Rules for Rotational Transitions
`
`BIS-
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`
`CCIITENTS
`
`Wliratzional Energy Levels
`Selection Rule for Vibuational Trmitions
`Rota.tiona|—‘VibIatinnal Tramitioos
`Probabilities oflitotational and Vibrational Transitions
`
`Electronic Enesgy levels o-flflolaeculea
`Electronic Transitions and: Associated Selection Roles of
`Molecufies
`Emission Liruewidtti oflillolecutsr Transitions
`
`'I11e Franck—Com:lon Principle
`Excciroer Eneagy I..El"EIS-
`5.2 liquid Enu'g3'l4nrtIsand'I'I1eir]IatIiaIion Properties
`Strurxure of Dye Molecules
`Energy Levels of Dye Mo-laecuies
`Excitation and Emission of Dye Molecules
`Detrimental Triplet States. ol'Dye Molecules
`5.1 Fnergy Imnels in 5oIds— Dielectric Lmer Materials
`Host M:-Iecrialzs
`
`Laser Species — Dopant Ions.
`hlanoua-I_.ine'uI.ridth Laser Materials
`Broaifln-and Tundnle Laser Matm'ials
`
`Broadening Meciianistn for Solid—State Lasers
`541 Fnergyr Leflzls in 5nIds— m Laser Materiak
`Enexgy Bands in Cq-staliline Srifids
`Energy Levels in Periodic StIucIJ.u:es
`Energy Levels of CDl'tI2ltIi.'.I:tI5, Insulators. and Semioondzoctors.
`Excitation and Decay ot'E:ciIed Energy Levels — Recombination
`Radiation
`
`Direct and Indirect Bandgap Semiconductors
`Election Distribution Function and Density of States in
`Semiconductors
`Intrinsic Senzlioonductor Maleriais
`
`Extriruic Semiconductor Materials —Doping
`p—n Juncliolu. — Reoolzltlsination Radiation Due to Electrical
`Excitation
`
`Quantum Wells
`Vaiation of Eandgap Energy and Radiation lifawelengdt with
`Alloy Composition
`Ileoomlziination Radiation Transition Probability and Linaewidtii
`IEFEIENC
`PICIBLEIE
`
`ll RADIATION AIIJ THERMAL EQUILIBRIUM — ABSCIIIFTIDH AND
`§I'H|lI.lIJE|'ED EIJIISSIJN
`UITEIHEW
`
`6.] Equililrrinli
`'I11erma| Equiliblium
`Thermal Equilibrium via. Conduction and Convection
`Thermal Equilibtiuro via. Radiation
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`I43
`I43
`I44
`I48
`I49
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`I50
`I51}
`Ifil
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`ODNTHITS
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`til Radiating Bodies
`Ste:I'an—BoItzn1ann law
`Wien‘s Law
`[rradianee and Radianee
`
`6.3 Cavity Iladiation
`Counting the Nuluhez offlavity Modes
`Ra.}rleigh—Jeans Fornurla
`Plano-Ts 1.aw for Cavity Radiation
`Relationship between Cavity Radiation and Elackbody
`Radiation
`
`Waveienglh Dependence of Blacibo-cl} Emission
`6.4 Absorption and Stimnlaled Emfion
`The Principle offleraiiod Ealanee
`Absorption and Stimulaaed Emission Coeflisccients
`EEFEIIJHICES
`PROBLEMS
`
`SECTION 3. LASER AMPLIFIERS
`
`'.l' CONDITIONS FOR PROEIJEING A LASER — POPULATION
`| GAIN... AND GAIN SATURATION
`CHTRVIEW
`
`'.-'.l Absorption and Cain
`Absorption and Gain on a Homogenaeously Broadened Radiative
`Transi1ion(Lorent:':ian Frequency Distribulion)
`(kin Coecfficierit and Stimulated Emission Cross Section For
`
`Hontogeneous Broadening
`Absorption and Gain on an Irshomogerieously Broaadenead Radiative
`Transition (Doppler Broadening with a Gaussian Distribution)
`Gain Coeffioient and Stimulated Emission Crow Section for
`
`Doppler Broadening
`Saris-tical Weights and line Gain Equation
`Relationship of Gain Coe:li'1cier1t and Stimulated Emission
`{loss Section to
`Coefliacient and Absorption
`Cross Section
`
`12 Population Inversion I Net:-mar} Condition for an Lmer]
`13 Salumtioll Intensity: {SuffirienI Condition for a Laserll
`'.-‘.4 Ilevlloplnent and Growth of a Laser Beam
`Growth oflilieam for a Gain Medium with Homogeneous
`Broadening
`Slime or Geometr_-,r offitmplifiring Meriium
`Growlh offieam for Doppler Broadening
`'.-‘.5 Exponential Cronvllr Ii'1i.'tor{C:in}
`'.r'.li Tlireshold Reqtlinerlents for a Laser
`Laser with No Minors
`Laser with flue Minor
`laser with Two Mirrors
`EEFEEECEE
`PROBLEMS
`
`2!]
`214
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`CEIITEHTS
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`LASER OSEILIJITICIN ABOVE '|'l-IIESHDLD
`lII'l'I'.E”I"lE'I'
`8.] Ituer Gin Saturtrtion
`
`Rate Equations oftlte Laser levels Thai lneluate Stimulated
`Emission
`
`Population Densities of Upper and Lower Laser Levels with
`Brzam Present
`
`Slnall-Signal Gain Coefficient
`Saturation oftlte Laser Gain above Threshold
`
`8.! Later BIt.".l‘.tI‘t Growth l'E"_|'l2IIl. the Saturation Irttemity
`Orange from Exponential Growth to Linear Growth
`Steady-State Laser Intensity
`IL! Oplimireation of laser Output Plu-mar
`Optimum Output Minor Transmission
`Optimum Laser Output Intensity
`Estimating Optimum l..aserOutput Power
`BA Fnergy Exchange between Upper Laser I..-enrol Population and
`Later Photons
`
`Decay Time o-fa laser Beam within an OptiealCa1.ritjr
`Basic Laser Cavity Rate Equations
`Sle.ad]'-State Solutions below Laser Threshold
`S1eaI:l3r—State Operation above Laser'['hresholt:l
`S5 Luer Oulpll FIIIt:t'u:iions
`Laser Spilcing
`Relaxation Oscillations
`
`8.6 Laser Amplifiers
`Basie Arnplilier Uses
`Pn:-pagatioo ofa High-Power, Short—Dura£ion Optical Pulse through
`an fitmpiifier
`Sanitation Enesgy Fluenoe
`Amplifying Long Laser Pulses
`Amplifying Short Laser Pulses.
`Cornparison oEEFfIcient Laser Atnplifiess Based upon Funtlalznentai
`Saturation limits
`
`lt'Iin'or fitrray and Resonator (Regenerative) Amplifiers
`IEFEIENC
`IIDBLEJE
`
`REQUIREMENTS FOR OBTAINING PCIPIJLATION INVERSIOHS
`UITEEVIEW
`
`9.] l|I're1's'|ons and Two-Itevel Systems
`9.2 llelaiine Decay Rates — Ilatliati-re verslm Collhional
`9.3 Steady-Slate llwersiolts in Three- and Four-I_.e1'eI Systems
`Tlueae-l_.evel Laser with The Interroerliate level as the Upper Laser
`level
`
`Three-l_.ew:l Laser with the Upper Laser I_.evel as the Highest Level
`Four-Level Laser
`
`‘LII Transient Population [n1rera'ons
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`255
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`23"}
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`COIHEIITS
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`9.5 Pmoesses Thal lrlliliit orDestro3' Inversions
`Radiation Trapping in Atonzts anad loos
`Electron Collisional Thezmalization of the Laser Levels in Atoms
`and long
`
`Comparison of Radiation Trapping and Election. Collisional Mixing
`in a. Gas Laser
`
`Absorption within the (En Medium
`|IEI'EE'ENII.5
`PIIDILEMS
`
`1D LASER Pl.I|5tI3ING REQUIREMENTS AND TECIIMIDUES
`CWEI‘.'I'IE'I|l'
`
`10.1 Excitation: or PtlIp'IIgTItresIJoId Ileqnirements
`10.2 Ftmtping Pathways
`Excitation by Direct Pumping
`Excitation by Indirect Pumping (Pump and Transfer]
`Specific Pump-an.d—Transfer Proeesses
`10.3 Speeifie Esoeilalittn Parameters Afioeialed with
`
`Optical P'ttntp|'_ng
`Pumping Geooteines
`Pumping Requirements.
`A Simplified Optics] Pumping Approximation
`Transverse Pumping
`End Pumping
`Diode Pumping of Soiitt—Stale Lasers
`Characterization eta Laserflain. Medium with Optical Pumping
`{Stope El'fiCiE!'IC‘f3
`ll}.-4 Speeifie I-Imeilalitt-I1 Parameters Assoeialed with
`Partirle Ptmtpiug
`Electron Collisional Pumping
`HE-al"_'||' Pmtiele Pumping
`A lk'|oreAe1:uraIe Description -ofEleetron Excitation Rate to a
`Specific Enesgy Level inaGas Discharge
`Elecit'ical Pumping offlemiconduetors
`|lEI'EI'ENIlI.5
`FRDILEMS
`
`SECTION II. LASER RESONATORS
`
`11 LASER CAVITY MODES
`D"-I'El‘|"IEI|"
`lI.1 Introduction
`
`lI.1 Longitudinal Laser Ca1'i3.' Modes
`Fal:tr)r—Pe1.'ot Resonator
`Fahry—Pet:ot Cavity Modes
`Lon.gitJtdina!. Laser Cavity Modes
`Longituttinai lttlodae Number
`Requirements for the t oi L.ong;itudina]
`Laser Modes
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`3!]
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`315
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`3l3rIJ
`3l3rI]
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`332
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`
`CIIITEHTS
`
`I13 TI'.=||IeIrcrae Laser Cari} Modes
`l-'-'resr|eI—Kin:hhofl' Diflraotion Integral Formula
`Developlizrent oclTtans1rerse Moder. in a Canrily with Plane-Parallel
`Mirrors
`
`Transverse Modes Usingflurirod Mirrors
`Transverse Mode Spatial Distributions
`Transverse. Mode Frequencies
`Gaussian-S|1ape¢!Transvezse Modes wiilijn and beyond the
`Laer Cavity
`ll.-I Properlies of laser Modes
`Mock-. Characteristics
`Effect of Hades on the Gain Medium Profile
`IEFEIENC
`PROBLEMS
`
`12 STABLE LASER IIESDHATDIIS JLHD Ghl.ISSlA.N BEAMS
`OVERVIEW
`Ill Stable Cu11'ed Mirror Cavities
`Curved lrlirror Cavities
`.-{BED Matrices
`
`Cavity Stability (}iIIer1'a
`I12 Proper-lies of [Iranian Beams
`Propagation of aflaussian Beam
`Cr..uis.sian Beam Ploperties ofTw'o-Minor 1.aserCavities
`Properties ofspeeilir: Two-M.inor Laser Cavities
`Mode Volume ofa I-lero1i1.e—Gaussian Mode
`
`of Real Laser Heals
`IL!
`IL! Propagafion offlaimial Ileana lJsingJl.H’CI.'l Matrices-
`Complex Ilearl Paramcll.-r
`Complex Beam PararoelJer'App|ierl to a Two-llnlirmr 1.aser'[.'avit.y
`IEFEIENC
`PIOIIEHS
`
`13 SPECIAL LASER CAHITIES AND CAVITY EFECTS
`OVERVIEW
`l3.l Umiable llesonaflors
`
`I32 Q-Slrilxlling
`General Description
`Theory
`Methocls o-fPIod.uc:ing Q—Swi§x:hing wilhin a Laser Cavity
`ILL! Gin-Switching
`I3.-1 Mod:-Inciting
`
`Thmrir
`Techniques for Pro-rlueing lilo-I:le—Lo-elcing
`I35 Pulse SI1orleoingTedII'ques
`Self-Pllase Morlulaaljon
`
`Pulse Shorlnerting or l..engshening Using Group Velocity Dispersion
`Pulse Compression [SlIrn'terI.ing] with Gratings or Prisrns
`l.]'lt:as..‘.|orl—Pulse Liseranrl Aroplifer System
`
`-ill
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`4-15
`423
`-132
`432
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`
`ODHIHITS
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`lJ.li Ring Lasers
`Monolithic Unidisecljonai Single-Mode Nd:‘I'A:G Ring Laser
`Two-Minor Ring Laser
`ll".-' Complex Beam Parameter Analysis Applied to Mtlti-Mirror
`Lmer Cawilies
`
`Three-Mirror Ring Laser Cavity
`Three- or Four—lulin'or Fou::uaet| Cavity
`I33 Cavities for Producing Spectral Narrowing of
`Laser Output
`Cavity with Additional Fabr3r—Pes:ot Ezalon for hIa:1'ow—]-'-'re1p1eoc:_v{
`Selection
`
`Tunahle Cavity
`Bmadband Tunable cw Ring Lasen;
`Tunable Cavity for Ultlanalm-w-Eequencjr Output
`Diso1'buu31:| Feed.l1ack{DFB} lasers
`Dislributeacl Bragg Reflection Lmers
`1.3.9 Laser Cavities Ileqoiliog Small-Diameter Gin Ilefiolls —
`Asligllalically Compensated Carin‘;-.-s
`13.10 Waveguide Cavities fior flas Imus
`REFERENCES
`rnoemus
`
`SECTION 5. SPECIFIC LASER S"I"':TI'EHS
`
`14 LASER SYSTEMS |N"H"DL"o"IHG LOW-DEHSFFY GAIN IIIEDIA
`DVEIVIEW
`I-4.1 Atomic Case Inaeas
`Introduction
`I-lelilI—Neon Laser
`
`General Description
`Laser Souclxlm
`Excita-fion Mechanism
`
`Applications
`Argon Ion Laser
`General Dessziplion
`Laser Smuzturc
`Excitation Mechanism
`
`Krjrpton [on Laser
`Applications
`I-leliII—Cadmi|ro1 laser
`
`General Description
`Laser Souctore
`Excitation Mechanism
`
`Applications
`Copper Vapor Lmer
`General Des-csiplion
`Lesser So1u:I:ore
`Excitation Mechanism
`
`Applications
`
`46-E
`4-6-9
`4'i'l]
`
`4'i|'l]
`
`4?!)
`4'13
`
`4'13
`
`4?!!-
`
`4'i'E
`451]
`4Erl]
`4!!
`434
`
`454
`435
`-456
`433
`
`49|
`49|
`49|
`491
`492.
`
`%
`493
`494
`
`49?
`49?
`497
`493
`499
`
`5011
`50]
`50]
`
`50]
`502
`504
`
`505
`505
`505
`50.7
`50.?
`
`‘.509
`
`
`
`
`
`
`
`

`
`CIHITENTS
`
`I-L2 Molecular -flax Lasers
`Introduction
`Carlmn Dimtide Lml.-r
`
`General Eleaicripliun
`Laser Structure
`Exciiatiun Mechanism
`
`Applications
`E‘.I:l.'I.I'IE1' Lasers
`
`General Descripliun
`laser Slmcmre
`
`General Elescripliun
`laser Structure and Eruccilaliun Mechanism
`
`Applicaliona
`Far-lltfrarnl Gas Lasers
`
`General Desncripliun
`Laser Slmculrc
`Exciiafiun Mechanism
`
`Jhpplicaiiciis
`Clunliral Lasers
`
`General Eleaicripliun
`Laser Snucsmrc
`Excitation Mechanism
`
`Applicalicns
`I4.3 I-Ray Plasnn I..‘.Isers
`Inlmihictiun
`
`Partying Energy Ilequiremcms
`Exciiafiun Mechanism
`
`Optical Cavities
`X—Ray Laser Tiansitiuns
`Application.-5
`I-1.11 Flwce-I-Electron liners
`Intmducziun
`laser Slrncture
`
`Applications
`REFERENCES
`
`15 LASER SYSTEMS IIIUDLVING HIGH-DENSITY GAIIII MEDIA
`0'|'ER1|']'EH'
`
`l5.l flrganic D3-e Lasers
`Immductiun
`Laser Stmcmre
`Exciiatinn Mechanism
`
`Applicaliona
`I52 Solid-State Lasers
`Inlrcnhictiun
`
`fill]
`SH]
`5] I
`5] I
`5] I
`515
`515
`516
`516
`5]?
`518
`521]
`52!]
`521]
`52I
`512
`522
`512
`523
`523
`514
`524
`52.4
`524
`524
`525
`525
`525
`525
`528
`532
`532
`532
`535
`535
`5315
`537
`53-7
`
`539
`53-9
`539
`539
`
`543
`
`545
`545
`
`
`
`
`
`
`
`

`
`55 l
`553
`554
`555
`555
`556
`556
`55?
`553‘
`55?
`55?
`553
`553
`559
`559
`
`CDIIIEITS
`
`Ruby Laser
`General Description
`Laser SI1!1.II1ll!E
`Excitalion lbloclumism
`
`Applicaiions
`Neoiiynium TAG and (11% liners
`Genera! Description
`laser Slnicture
`Excil:-nion Mecharlism
`
`.hppl'u;:aIio|15
`Neodg-nI'I1m:YLF Lasers
`General Description
`laser Sll1lI:£llrE
`Excitaiion Mocliariism
`
`hpplicalions
`Neod3.'nI'um:Yll.rim1 Vanadate I N|i:YV04]I Lasers
`General Description
`Laser Slnicture
`Excilalion Mecllanism
`
`Applicalions
`Yllcrb1'ml:YAC Lasers
`
`(cal Description
`laser SI1!1.Il1ll!E:
`Excitation Meclunism
`
`Applicalions
`Aluandrile Luer
`
`General Description
`laser Slnicture
`Exciuuion Mechanism
`
`Applicafions
`Ti.IiI'IIi.IlI'I Sapplire Laser
`General Description
`laser Stmciure
`Excilaiion Mnslunism
`
`hpplicalions
`Chronill IJSJLF and I.-iCA.F Insets
`
`General Description
`laser 5I!1lI.‘.[I.IlE
`Excilalion lIn'Iec|unisu1
`
`iitpplicalions
`Fiber Lasers
`
`General Description
`Laser Slmciure
`Excilalion h'Iec|I:.u1isu1
`
`Applicaliotls
`Color Cent-e1'I..He1's
`
`Genera! De.sI:ription
`Laser Slnicture
`
`
`
`
`
`
`
`

`
`CIIITEHTS
`
`Excitafiun Mechanism
`
`Applicaljorls
`I53 Semiconductor Diode Lasers
`lmmdsuctiun
`
`Fail: Bait: Types of laser h‘[a;teri:||s
`Laser Struczulrc
`
`F!EqlBDC'j|' Comm! of l..aser Output
`Quantum Cascade Lasers
`p—DcIp-ed Gennanium Lasers
`Excitation Mechan.isn:.
`
`Applicmiens
`IIEFEIENCES
`
`SECTIIEII 5. FREQUENCY HULTIPLIEATIDH OF LASER BEAMS
`1E FREQUENCY MLIl.T|Pl_|CA'|'lDlII OF LASERS AND DTHER
`HCIHLINEAR OPTICAL EFFECIS
`fll'Ell'I"]I'.'uI'
`
`lIS.l Wave Pmpafilion in an A.niaolroprir Crystal
`I62 Polarizalion Rcspurne nfhialerials In Light
`I63 Second-Order NnIi'nean' Optical Pnocc-mes
`Second Harrlmnic Genexatien
`
`Sam and Difference Frequency Generation
`Dpljcal Parametric Daccillaticn
`IISA Third-Order hlonlinear Optical Prncvmc-5
`Third Harmcnnic Generation
`
`[!'IlEllSil'_'||'—DEpEIIEi.EllI Refractive Index — Self-Focusing
`I65 Nonlinear flptical Materials
`lliti Phme Matching
`Description D-{Hume Matching
`Achieving Phase Matching
`Types of Phase Matching
`II‘3.'." Saturable Ahsnrpljcn
`I63 T1m1~Ph:nton Jlbetrrptinn
`ll5.5l Stimulated [human Scam.-ring
`lIS.lIl]' Ilanionic Generation in Case-5
`REFERENCES
`
`Appendix
`Index
`
`5?4
`STIIS
`STE:
`STE:
`5?‘)
`SEI
`59I
`5%
`594
`594
`596
`59'?
`
`62 I
`625
`
`
`
`
`
`
`
`

`
`1 I
`
`ntroduction
`
`-DUEEUIEW A laser is a vElE'l|'lt3B Ihat amplifies light
`:I]£l produces a highly directional. high-inremiry
`beam Ihatmofioftenliasavely pure frequeneyor
` . ltcomesinsiines ranging From approx-
`inlatelyonelsenlhlhediamelerofaliulnanhairto
`Ihesimeofat-erylargehuildi.ng.inpowersranging
`from I04‘ to lflm‘ ‘W, and in wavelengths ranging
`frornd1emicrowmretothesoft—X-rayspecualmgirlls
`with eonesponding freqoeltcies from EU" to ID" Hr..
`lsesershsvepulseenezgiesasltigltas ll]‘J and pulse
`d|uationsasshoI'l:m5 3-: ID''5 s. Theyeanly
`driillunlesintlrernosldurahleofmanarialsalidoan
`
`of exiaenee!
`
`welrldetaclnedletirioswithintlsellrlrnaneye. They ale
`3 key component ocfsmnenf our most modem com-
`lrlinitznion systemsatad a1elhe'"phonograph needle"
`clouroornpoctrtisc players. They perform lIeattreat-
`lnentofltigh-strenglll materials. sucha the pistons of
`ourantornobile engines. and provide a special surgi-
`callznife for many lygolfmedical p|1:I:.'edures_ They
`aclaslatgetdesignators for rnilitaiy weapons an|lpro-
`vide for like rapid check-out we Irate come to expect
`at the supermarket. What a rernariahleIangeol'clra:-
`aeleristics foradevice thatis in only its liflh decade
`
`INTRDDUCTIJN
`
`There is nothing magical about a laser. It can be thought ofasjnst another type
`ol light souroe. Itcertainly has many unique propeni that make it a special light
`source. but these propertiescan be understood without tnowledgeof sophisticated
`rnathemal‘.ica.I techniques orcomples ideas. It isthe objective oflhis text loesplain
`Eheoperationofrhelaserina simple, logical approach lliatbuilds fromone oom-
`cepl In the nentasthe chapters evolve. The oonoepts, M they are rlevelnped, will
`he applied to all classes of laser .I'DH£I'.lfll5, so that tlse reader will develop a sense
`ol l'he broad lield ol lasers while still acquiring the capability to study, design-., or
`simply understand a specific type of laser system in detail.
`
`DEFlNl1'lD!Il OF THE LASER
`
`The word laser is an acronym for Light Aniplifieiiion by Stimulated Emission of
`Rarliflion. The lmer makes use of prooesses that increase or amplify light signals
`aflerthose gnals have been generated by other means. These poo-rm include
`(I) stimulated ernissinn, a natunfl el‘fect that was deduced by consideratinns re-
`lating to lllemiodynamic equilibrium. and {2} OPT-lcal feedback {present in most
`
`
`
`
`
`
`
`

`
`lll'I'llC|Ill.I’l.'l'IDH
`
`Clplical resonator or cavity
`A
`
`Amplllyilg medlurn
`
`
`
`5. 1-1 Flllphlielsl
`sdmelnaticoftypical hit
`
`Fully re1|e-sting
`rriror
`
`Parllall-.;1rensm1ting
`rriror
`
`Imers) that is usually pnovided by nlirmrs. Thus, in ils simplest forni, a lmen:on—
`sists of a gain or amplifying medium {erheie stirnulated ernimion occurs], and a
`setofmirrors to feed Ihe Iighthack intolhe alnplitierforcontinued growthofthe
`developing beam, as seen in figtre I-L
`
`5IhI'l.lCI'I"f OF A LASEII
`
`Tlvesinlpliciryofalasercan heunderstoodbgr considering the light from acandle.
`Normally, a hunting candle radiates light in all directions, and therefore illumi-
`nates various objects equally if they are equidistant fmrn the caidle. A. lasertates
`light that would nnnrndly be emitted in all directions, such as from a candle, and
`concentrates that light inlso a single direction. Tllns, iflhe light radifling in all di-
`reofionshumacaruilewerenahedinhiasingleheanolflrediuwelerofthe
`pupil ofyour eye (approxinlalely 3 nun), and ifyml were
`adistanee of
`I In from the candle, then the ligllt inleruily would he |,[I]l.lII1 times a bright as
`the light Ihal you norrnally see radiating from the candle! That is essenliallgr the
`tuiderlying-coneeptofthe operil.i1::II1 -ofalaser. However, acaridle is not Ihe kind of
`medium that prodices amplification, and thus there are no canrle Imers. It takes
`relatively special coruzlitiorns within the [met medium for amplification to occur,
`but i1 islllat cqiahilityoflaking light that would nonlially radisle from assume in
`all l2ll.I'El:lZlClI'B — and ccncentriiing that ligllt into abean traveling in a single direc-
`1ion—Ihai is involved in rnitingalaser. These specid conditions, and Ihe media
`within which they are prmluced, will In described in some deiail in Ihis I:IJol£.
`
`UNIGE PIIOFEIITES OF A LASER
`
`'l'I'eehean1of|iglilger|eruedl:I}ratypical lasercarIha\rernan'_I,rpItJperties1iIata'e
`unique. When oompa1ingIaserpropertiestofl1oseofoiherIightsourees.itr:lJ
`be readily recognized that the values of various puamerers for laser light the:
`gjeailyexeeedoraremuchnmiereslticfivedianfllevaluesfinnumycomnnn
`Iighlsources. We never use lasers for street illumination, orforillulnination within
`our houses. We don't use them for searchlights or flashlights or as headlights in
`
`
`
`
`
`
`
`

`
`IN1'IIDI'.|IJCTIDN
`
`our ears. Lasers generally have a narrower fit.-qrreoegr distribrrtiul, or much higher
`iotenscity, or a much greaterdegree oloolI.imstion, or much shorter pulse duraion,
`lhanlhat atnildale [mm more common lylfloflight sources. Tlteaefure, we do use
`them in. oonrpact disc players, in superrnarket r:h.er:k—ou1 sr:m1r|.eIs,io surveying in-
`struments, and in mediuil appliealiorrss as a surgical Ianife or for welding detadterl
`retinas. We also use them in eomrruroieatiorzm systems and in Iarhr and military
`targeting appljeafiorrs, as well as many other areas. A laser is a specialized light
`source that should be used only when fr: uniquepmpenies are required.
`
`THE IJISER SPECTRUM All} WAVELENGTPES
`
`A portion oflhe e|er:trorrragrreti:r: radiation qreetrum is drawn in Figure I-2 for the
`region emrered by currently existing lasers. Such lasers span the wmrekurglh range
`from the lariofrxert pert ofdme spectrum {I = l,(III1 pro} to the sofl—X—ra}I region
`Ur. = 3 nm), thereby eoverirrg a range of wavnelengtlts ofalrocnt six orders ofrrrag-
`nitude. There are several types ol' units that are used to define laser wavelerrglhs.
`These range from llIlI:l‘lJlIIEl£:l'S|.'II'ITI.ll3l'lI.'IlS {pm} in the inlmmd to nanornetelsfnrn)
`and angstroms {rat} in the visible, ultras-'iolet{UV ), vacuum ultraviolet {VUVL ex-
`treme ullrmriolet {EUV or}CUV'], and sofl—X-ray [SXR] spectral regions.
`
`|‘£IH'ELEHG"I'H I.|llI'I'S
`
`I_r.rm = 1045 In:
`rs: to-“m;
`Inm= [D4 In.
`
`Consequently, I ntieroo {um} : Illlilfllangstrorrrs {ii} : l,{I.'II}naooroete:'s {run}.
`Forearample. green lightbas awarveleogrhoffi 3-: H14 l]'I: =l}.5 run = 5,[I]€IA. =
`SEN) run.
`
`.____
`
`.
`
`_
`HF
`
`I
` _._l___
`
`9”“
`*9 '3"
`Ar
`..
`..
`
`.,
`
`CD
`
`_
`
`__
`
`_.
`
`I
`I
`#21"
`H
`ratge ofva'ioLr5 beers
`
`_
`i
`.
`.. .
`.
`.
`.-
`_ FIR La.-nor:
`
`co,
`
`Far: Infrared
`
`supm tlikpm
`
`N:
`Ruby
`KrF
`Ha-Ne
`mama
`1-In I'.‘.u
`
`sun-I.Hqy
`..
`—
`Lasers
`
`Inlrurtd
`
`Ha Ha
`
`_C~g:s:1m D.r~a_
`nu:
`T|..B.Iz03
`EDP‘ Ill Ray:
`LJi‘rrr\-|cI|eL
`".I'iu|:I|u
`'_.. _-.__.__ j _.__
`1=,.:n1
`3I:HJnm1I:HJnm sunm mnm
`apm
`.. is
`he
`ENERGY {T} --..
`
`
`
`
`
`
`
`

`
`IHTIDBUCTIDH
`
`IIHIELEIIGTH IIEGIDHS
`
`Far infrared: II] to I,tII1 _um;
`mirldle infrared: I to 11) _um;
`near intrared: I}.''.-' to tom;
`visible: 0.4- to I17 run. or 4[I}to ?{I.‘I mo:
`ultraviolet: fl'.2uJI}.r-1 p.m, or2lIlto-1-Illrtm;
`vacuum ultraviolet: 9.] to 0.2 pm, or It'll to Ztllnrn;
`extreme ultraviolet: 10 to It'll] om;
`soft X-ra3rs: ] nm to approximately 211-30 nm {some overlap with EUV].
`
`A BEEF HISTORY OF THE LASER
`
`Cha:rlesTowrres took advantage ofdzre stimulated emission process toconstruct a
`microwave amplifier, refenedtoasamaser. This device pn::Iluce£lacoherenl beam
`of microwaves to be used for communications. The first Ioaser was proriucerl in
`ammonia vapor with the inversion between two energy levelslhat
`at
`a wavelength oi L25 cm. The wavelengths produced in me maserwere compara-
`ble to the dimerrsions -of the device, so exlnq:IJ-lalion to the optical regime — where
`wavelengths were live orders ofmagoitucle smaller— was not an obvionseirtension
`of thfl. work.
`
`In 1953, Townes an-d S-chawlow publisher! a paper concerning theiridem about
`e:rtending the rnaser concept to optical frequencies. They developed the concept
`ofan optical amplitier surronuorle-d by an optical rnirror resonant cavity to allow for
`glowfliottlrehealo. Towoesaodflclrawloweaeh reeeivedaflobel Prime forhis
`worl: in this field.
`
`In 1960, Theodore Maiman of Hughes Research Laboratories produced the
`first laser using aruby crystal as the arnplifreraodallasltlanipu the energy source.
`The helical flashlarnp sunoundert a rod-shaped rub}! cry-stal., and the optical cavity
`waslomiedhyulalingllreflattertalaidsofltnembgrrodwidnahighly reflecting
`material. Aninleaiseledbearnwasohservedtoeroergefromtheesid oflherod
`when the flashlarnp was tired!
`The t'|rs1gasla9erwudevelopedinl96|b}'A..lavan,W. Bennett. and D. Hm"-
`riott. ot Bell Laboratories, using a mixture of helium and neon gases. At the same
`labomtulies, L. F..lohnson and K. Nassau demonstrated the firsl neulymium laser,
`wllichhassirrcebecomeooeoftltemosueliahle Iasersavailable. Thiswas {allowed
`
`in [962 by the first semiconductor laser, demonstrated by R. Hall al the General
`Electric Research I_.:borato|'i. In 1963, C. K. N. Patel of Bell labo|a1oriesdis—
`covered the infrared carbon dioxide laser, which is one of the roost efiicient aid
`powerful lasers available today. Lmer that sa.Ioe year, E. Bell of Spectra Physics
`discovered the lirst ion laser, in l'DBI€l.l.I'}" vapor. In 1964 W. Bridges of Hughes Re-
`search Laboratori discovered the argon ion lmer, and in. I966 ‘W. Silfltflfl, G. ll.
`Fowles, and B. D. Hopkins produced the first blue helium—ca.dnLium metal vapor
`
`
`
`
`
`
`
`

`
`IHTIDDIJCTIDII
`
`laser. ]I|In'ingtltat.san1.eyear, P. P. Sorolzinand I. R..Lanltard ofthe IBM Research
`Laboratories developetlthe firm liquid laser ung anoigmticdyertissolved in am]-
`vent, theieb} leading to the category of broadly tunable lasers. Also at that time,
`W.‘Walleranrlco—worl:e:'s atTl3l.Greporled the litstcoppervaporlaser.
`The first vacuum ultraviolet laser was IB|2I3l'l£d to occur in molecular hydro-
`gen by R. Hodgson ofIBM and independently by IL Waynantet al. oflhe Naval
`Research Laboratories in I971). The lirst of the well—l:norwn rare-gas—ha]irie ear-
`ccinterlasets was observed inxenonfluorideb-}I'.l. J. Ewingandfl. Brauofthe
`Avco—EveIet1 Reseinvch lJ1lJEI'flIDl]r in I975. In that same year, the fits! quantum-
`well Iuer was made in agallium arsenirle semiconductor by I. van der Ziel and
`co—worlters at Bell Iaboratori. In I976, I. M. I. Made; and co-wvorliers H Stan-
`ford Univeasitgr dernonsnated the Iirst free—eler:troIt laserainplilieropelating in the
`inflated at the DD; laser wavelength. In |'Il'9, Walling and co—worlters 5: Allied
`Ch-ernicalcorpnration obtained lJ.I'Dflll}|' tunable laserotnputfrornasolid-statelaser
`material called adeitanrhite, and in I935 the lirst sofl—X—ra3r laser was successfully
`III-EI1IDI1SLfIl[£IliD£il]lglJI}Fl{Ill.l££lSE3lBI]ll]I1l
`D. ltllatthews andalslgenum—
`ber of co—worlt.ers at the lawrence Iivermore Laboratories. In IQEIS, P. Moulton
`discovered the titatitnn sapphire laser. ln l'99l, M. Hasse and co-workers rlievel—
`operl: the lilst blne—green diode laserin ZnSe. In 19943 F. Chpmso and co—worl:ers
`dewaloped tlte quantum cascade liner. In 1996, S. Nakamtuadeveloreii the lirst
`blue ttiotlie laser in GaN—baserl materials.
`
`In l96l, Fox and Li described the existence ofresonant tlansverse modes in
`a laser cavity. That same yea", Boyd and llhrrlon obtained solutions of the wave
`equation for confocal resonator modes. Unstable resonators were detnonstrated
`in 1969 by Krupke and Sony and were described tlteoretically by Siegtnan. Q-
`switching was lirst obtained by h'Ic.C."|ung and I-Iellwarth in 1962 altd described
`later by ‘Wagner and
`The first rnode-locking was obtained by l'IaIgnJ"-‘B,
`Fork. and Pollack in I964. Since then, minty special Ct!‘|."lE)' arrangements, feetfliaclt
`scltetnes, and otherdevices have been developed to improve thecontrol.openiioI1.
`and reliability of lasers.
`
`D"d‘EIlVIEW' OF '|1'lE BDCIK
`
`Isaac Newton described Iigltt as small bodies emitted from shining substances.
`This view was no doubt influenced by the fact that ligllt appears to propagate in a
`line. Efltrinian Huygens. on the other hutd. dmcrilied light as a wave mo-
`tion in which a small source sprearh out in all directions; most observed effects —
`including difliactinn, reflection, and refraction —ca1 he attribute::Ito-the expansion
`ofprimaryr waves and of secondary wavelets. The dual I'lflllI'E of light is still ausc-
`ful concept, wlteaeby the cltoice of particle or wave explanation depends upon the
`effect to be considered.
`
`Section One ofthis book deals with the fundamental wave properties of light,
`including hIl'.a:twe|]'s equations. the interaction of electromagneti