LASER FUNDAMENTALS
`
`SECOND EDITION
`
`WILLIAM T. SI LFVAST
`
`School ul Oplits I CRECIL
`Lhilmlsily of Centrd Florida
`
`CAMBRIDGE
`IINIVERSITY PRESS
`
`(cid:36)(cid:54)(cid:48)(cid:47)(cid:3)(cid:20)(cid:20)(cid:19)(cid:28)
`
`ASML 1109
`
`1
`
`

`
`PUBLISHED BY THE Fl 5‘|"N']HZ.h'l'E OF THE. UNIVERSITY l}FCfl.kIBI]IIIE
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`ISBN l]—52l—333-15-0
`I. Lula ]_ 'I"|‘.h.
`
`TM6T5.S52 HI]!
`6II_"HS"6—&QI
`
`I5BNI]5lI 333-1-5|] hlllaml
`
`ICIIIEEES2
`
`2
`
`

`
`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
`
`xxiii
`
`
`
`EH3EHEBEEECTIGEflua-.a~au«.n.u..w.na-—-——-—
`
`
`
`
`
`VII
`
`3
`
`

`
`viii
`
`CONTENTS
`
`l_,_.L__,.__...can-‘.'4"§4‘~.."
`
`45
`45
`43
`45
`
`49
`
`54
`54
`54
`56
`56
`ST
`5?
`59
`
`Estimating; Particle Densities oflttlaterials for Use in the
`Dispersion Equations
`1.-I Coherence
`
`Temporal Coherence
`Spatial Coherenoe
`REFERENCES
`I'Ill'.'-IIILEMS
`
`SECTI-DH 2. FUND.ll|IlEHT.M. mlfiflflfll PRDPERTES BF LIGHT
`3 PARIICLE NATURE OF UGHT — D-ISCREIE ENERGY LEVELS
`D"t"ER'h"lIF."W
`
`3.1 Bohr Theory til’ the Hydrogelt Atom
`Historical Development of the Concept of Discrete Energy Levels
`Enexgy Levels of the Hydrogen Atom
`Frequency and Wat-'elengti't of Emission Lines
`Ionization Energies and Energy Levels oflons
`Photons
`
`3.2 Quantum Theory offittulnic F_ne-rgy Levels
`Wave Nature of Particles
`
`Heisenberg Uncertainty Principle
`Wat-‘e Theory
`Wat-'-e Functions
`«Quantum States
`']11e Seltrttdinger Wave Equation
`Energy and Wave Function for the Ground Statue of the
`Hydrogen Atom
`Excited States of Hydrogen
`Allowed Quantum Numbers for Hydrogen Atom Wave Functions
`3.! Angular lhlflfllflllfllll of Atoms
`Drbital Angular Momennlm
`Spin Angular Momentum
`Total Angular Momentum
`3.4 Energy Let-'eIs Associaled with One-Electron Atorns
`Fine Stnictlire offipectral Lines
`Pauli Exclusion Principle
`3.5 Periodic Table ofthe Ekmestts
`
`Quantum Conditions Associ ated with Multiple Electrons Attached
`to Nuclei
`
`Shonitartd Notation for Electronic Configurations of Atoms I-laying
`More Than Dnae Electron
`
`3.6 Energy Iieycls of ltlttlli-F.le<clJ'on Atoms
`Energy-Level Designation for M-ulti-Electron States
`Russell—Saunders or L5 Coupling — Notation for Energy Let-els
`Energy Levels Associated with Two Electrons in Unfilletl Shells
`Rules for Obtaining S. L. and J 1'orLS Coupling
`Degeneracy a.nd Statistical Weights
`j—_i Coupling
`Isoelectronit: Scaling
`
`4
`
`

`
`CDITIEHTS
`
`REFERENCES
`PROBLEMS
`
`4 RADIJITNE TRANSIT!-Cl|'«I5 MVIIJ EMISSION LINEWIDTH
`ovsiwrsw
`
`-L1 Decay oflilircited States
`Radiative Decay of Eseited States of isolated Atoms —
`Spontaneous Emission
`Spontaneous Emission Decay Rate — Radi ative Transition
`P'rolJa’oi|ity
`Lifeflrne of a Radiating Electron — The Electron as a Classical
`Radiating Harmonic Oscillator
`Nonraclialziwa Decay of die Excil-rxl States — Collisional Decay
`-1.1 Elnission Broadening and Linewidth Due to Iladiatit-‘e Decay
`Classical Emission Linewidlli of a Radiating Electron
`Natural Emission Linewidlli as Dedueed by Quantum htieclianics
`t!t'1ini.In1.in': Linewidthll
`-1.3 Additional F.missio|i-Ilroadening Processes
`Broadening Due to Nonradiati1.'e {Col1isiona1]I Decay
`Broadening Due to Dephasirig Collisions
`Amorphous Crystal Broadening
`Doppler Broadening in Gases
`lrioigt Lineshape Profile
`Broadening in Gases Due to Isotope Shifts
`Compaiison of Various Types of Emission Broadening
`-1.4 Quantum 1'lrte<:'Iianical Description of Rarliating Atoms
`Electric Dipole Radiation
`Electric Dipole Mani: Element
`Electric Dipole Transition Probability
`Oscillator Strength
`Selecli on Rules for Electric Dipole Transitions Involving Atoms
`with a Single Electron in an Urifilled Sulzl-shell
`Selecli on Rules for Radiative Transitions Irwoliring Atoms with
`More Than One Electron in an Unlilled Sub-sI1elI
`
`Paiity Selection Rule
`[nefficient Radiative Transitions — Electric Quadnipole and Other
`Higher-Order Transitions
`IitF.l?ERENIZ'ES
`raonmus
`
`5 ENERGY LEVELS AND RADIATNE PROPERTIES OF MOLECULES.
`Ll-lJ].I|DS.. AND SOLIDS
`rwsiwtsw
`
`5.1 Molecular Iiner'gy Iinels and Spectra
`Eitngy Levels of Molecules
`Classification of Simple Molecules
`Rorational Energy Levels oI'Linear Molecules
`Rotational Energy Levels of Symmetric-Top Molecules
`Selection Rules for Rotational Transitions
`
`86
`BIS
`
`89
`B9
`
`90
`
`91]
`
`9-'-I
`
`95
`'33
`101
`1131
`
`103
`105
`106
`10'?
`109
`109
`114
`115
`1 13
`121
`122
`123
`124
`134
`
`125
`
`129
`
`13!]
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`13 I
`13!
`13!
`
`135
`135
`
`135
`135
`133
`139
`141
`14-I
`
`5
`
`

`
`CONTENTS
`
`Vibrations] Energy Levels
`Selection Rule for '|n"d:rra1:ional Trarisitions
`Rotationa|—‘t"ibra1:ional Transitions
`Probabilities of Rotational and Vibrational Transitions
`
`Electronic Energy Levels of Molecules
`Electronic Transitions and Associated Selection Rules of
`Molecules
`Emission Lioewidlh of Molecular Transitions
`
`Tbe Frant:it—Condon Principle
`Excirner Energy levels
`5.2 Liquid Ens.-I'g'_I.' Levels and Their Radiation Pr'o=_pi_-rti-es
`Structure offlye Molecules
`Energy Levels of Dye Molecules
`Excitation and E.rnis.si on of D}-‘e Molecules
`Detlirneotal Triplet States of D}-‘e Molecules
`5.3 Fatergy ltevels in Solids — Dielectric Laser ltlalerials
`Host Matelisls
`
`Laser Species — Dopant Ions
`l'~larro'u.'-i_.inewidt1i Laser Materials
`Broadband Tunable Laser Materials
`
`Broadening Meclianism for Solid-State Lasers
`5.4 E.ni.-rgy In.-vials in Solids — Scmicoruductor Laser |.'t-iatcrials
`Energy Bands in Cl'}'SIai.l1l'II3 Solids
`Energy Levels in Periodic Structtires
`Energy Levels of Conductors. lnsulators. and Semiconductors
`Excitation and Decay of Excited Energy Levels — Recombination
`Radiation
`
`Direct and indirect Eaodgap Semiconductors
`Electron Distzlibutzion Function and Density of States in
`Semiconductors
`intrinsic Semiconductor Materials
`
`Estiinsic Seroicondtictor Materials — Doping
`p—n Junctions — Recombination Radiation Due to Electiical
`Excitation
`
`l-leterojtuiction Seniiconductor Materials
`Quantum Wells
`‘v’a.riation of Bandgnp Energy and Radiation Wavelength Willi
`Alloy Composition
`Recornbi nation Radiation Transition Probability and Linewidtli
`REFERENCES
`PROBLEMS
`
`it RA.'|J'|ATl'DN AND THERMAL EII}U|l.lBRlU|'h‘| — ABSDRFTHJH AND
`STIMULATED EMISSION
`OVERVIEW
`
`6.} Equililtriiun
`Thermal Equilibli urn
`Thermal Equilibli urn via Conduction and Convection
`Tl1ernia.l Equilibrium iia Radiation
`
`143
`143
`1-14
`143
`149
`
`150
`150
`15!
`152
`153
`153
`155
`1515
`15?
`153
`153
`159
`115!
`16-15
`163
`163
`163
`1".I'D
`1'i'2
`
`113
`174
`
`1T5
`1'II'9
`1'i'9
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`132
`134
`136
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`19!
`195
`195
`195
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`199
`199
`199
`199
`233
`EEK]
`
`6
`
`

`
`CONTENTS
`
`l.'i.1 Radiating Iludie-5
`SteFan—Boltsmann Law
`Wien‘s Low
`Lrradianace and Radiance
`
`IL’. Cavity Radiation
`Counli ng dte Number ofCavity Modes
`Ra}.r1eigh—Jeans Formula
`Planolt‘s Law for fax-'it}' Radiation
`Relationship between Cavity Radiation and Blaokbody
`Radiation
`
`Wavelength Dependenoe of Blackbody Emission
`ti.-4 Absorption and Stimulated Ennis-.sion
`The Ptinoiple offletailed Balanoe
`Misorplion and Stimulated Emission Coefficients
`REFERENCES
`PROBLEMS
`
`SECTION 3. LASER HLIFLIFIERS
`
`? CONDITIONS FOR PRODUCING A LASER — POPULATION
`|lW'ER5lOH5, GAIN. AND G-.AlN SATURATION
`O‘!-"ER\I'IE'lI'
`
`2.1 Alisorp-lion and Cain
`Mzlsorption and Gain on a Homogerueously Broadened Radiauve
`TransiIion{Lorent1ian Frequency Disuibulioni
`Gain Coefficient and Sti Irluiated Emission Cross Section for
`
`Homogeneous Broadening
`Absorption and Gain on an Inho mogcoieously Broadeoed Radiative
`Transition {Doppler Broadening with a Gaussian Distribuli on]
`Gain Coeffioieatt and Sli mulated Emission Cross Section for
`
`Doppler Broadening
`Statistical Weights and the Gain Equation
`Relationship of Gain Coelfltient and S15 mutated Emission
`Cross Section to Absorpli on Coeflicient and .-absorption
`Cross Section
`
`2.! Population Imrersion lihiccetj-' Condition for :1. I.:1s-H‘!
`13 Saturation Intensity ISIJt.'iicienl Condition for a Laser]
`2.4 Dcveloplncnt and Gmwtli of :1I.ast-rlleam
`Growth of Beam for a Gain Medium witli Homogeneous
`Broazleni ng
`Shape or Geometry of Amplifying Medium
`Growth of Beam for Doppler Broadening
`2.5 Escponential Growth Factor {Cain}
`2.6 Tlareshnld Requirements for :1 Laser
`Laser with No Mirrors
`Laser with One Mirror
`Lane: with Two Mirrors
`REFERENCES
`PROBLEMS
`
`21}!
`2-04
`2435
`21315
`2|TI‘
`208
`209
`2 l 0
`
`EH
`214
`215
`216
`21'?
`Ht
`221
`
`225
`225
`225
`
`225
`
`229
`
`23!]
`
`23 I
`232
`
`233
`234
`235
`238
`
`233
`24-]
`
`24'-1-'i‘
`243
`24-9
`253
`253
`
`7
`
`

`
`xii
`
`CONTENTS
`
`LASER OSElLLATlON ABOVE THRESHOLD
`UVEEHFW
`3.1 Laser Cain Strttrraticm
`
`Rate Equations of the Laser Levels That lI'l('ll]Cl.E Stimulated
`Errtis.si on
`
`Population Densities of Upper and Lower Laser Levels with
`Beam Present
`
`Small-Signal Gain Coeffioienl.
`Saturation of die Laser Gain above Threshold
`
`3.2 I.-user ll‘-earn Gmwflt beyontl the Saturation Ilbtertsity
`Change from Exponential Growth to Linear Growth
`Steady-S Late Laser lntensity
`3.3 Optimization oi'I.:t:ser Output Power
`Dptirnum Output Mirror Transrrtission
`Dptirnum Laser Output intensity
`Estimating Optimum Laser Output Power
`3.4 F_nerg_I|.- Exchange between Upper I.a2aer I.ei'el Population and
`Laser Photons
`
`Decay Time ofa Laser Beam within an Clptioal Cavity
`Basie Laser Cavity Rate Equations
`Steady-S tate Solutions below Laser Threshold
`Stead}.-'—3tar.e Elperalj on above Laser Threshold
`3.5 Laser Output Fluctuations
`Laser Spilcing
`Relaxation Oscillations
`
`3.6 Laser .-iniplifiels
`Basie Amplifier Uses
`Propagation of st High-Power. Shorl.-Dura1:ion Gptioal Pulse through
`an An'tpl.ifier
`Saturation Ertergy Fluenoe
`Attrtplifyi ng Long Laser Pulses
`Amplifying Short Laser Pulses
`Eomparison ofEffieient Laser Amplifiers Based upon Fundamental
`Saturation Lirnils
`
`It-‘lino!’ Array and Resonator {Regerierativei Amplifiers
`IIEFERENCFS
`Pltotnl-Litts
`
`REQUIREMENTS FOR OBTAINING POPULATION INVERSIONS
`DVEHWEW
`
`9.1 Ilnrersions and Tm:-Level Sgsteans
`9.2 Relative Decay Hales — llatliatit-‘e ‘I-'E‘I‘Sl.'l5 Cu-llisional
`9.3 Steady-Slate Inversions in Tlmee- and Fotlr-I.e1'el Systerus
`Three J_.ei'el Laser with the lntennediale Love! as the Upper Laser
`Level
`
`Three -Level l_.:-tser 1.I.'i1h The Upper Laser Level as the I-Iighesll_.eve1
`Four-Level Laser
`
`‘J.-I Transient Population Im'et'§'ons
`
`255
`255
`255
`
`255
`
`256
`251'
`25?
`253
`253
`2fil
`215i
`215i
`
`26-6
`215?
`233
`270
`272
`273-
`2T3
`226
`279
`2'1"?
`
`231]
`232
`234
`234
`
`233
`233
`
`2‘.l'C|
`290
`290
`292
`293
`
`295
`293
`3!]!
`334
`
`8
`
`

`
`CONTENTS
`
`xiii
`
`9.5 Pmcesscs That lrdliliit or Des‘tm_v Invccsions
`Radi:-iI3'on Trapping in Atorris and Ions
`Electron Collisional Thermalizafion oi the Laser Levels in Atoms
`and Ions
`
`Comparison of Radiation Trapping and Electron Eollisional Mixing
`ina-Gas Laser
`
`Abso:rpIi on within the Gain Medium
`HFIERENCES
`PROBLEMS
`
`113 LASER PUMPING liEOlJlREit|lENTS AND TECHNIQUES
`O’lt'E.|i‘.'l."IE'lI'l|'
`
`ll]-.1 Excitafinn or Ptnnping Threshold Requirements
`10.1 Pumping Palinvays
`Excitation
`Direct Pumping
`Excitation I:r_v Indirect Pumping {Pump and Transfer}
`Specific Pump—ancl-Transfer Processes
`I'|.l'.3 Specific Excitation Phrmncteis fiissdicialed with
`Optical Pumping
`Pumping Geometries
`Pumping Requirements
`A Simplified Optical Pumping Approximation
`Transverse Purnpi.ng
`End Pumping
`Diode Pumping of So1i:‘_T—Stale Lasers
`Charactelization ofa Laser Gain Medium with Optical Pumping
`{Slope Efiicie:nc}r]
`10.4 Specific Excitation Pararncteis ilisso-cialed with
`Particle Pumping
`Eiectron Collisional Pumping
`Heavy‘ Particle Pumping
`A More Accurate Description ofEl-ectron Excitation Rate to a
`Specific Energy Level in a Gas Discharge
`Electrical Pumping of Semiconductors
`REFERENCES
`PROBLEMS
`
`SECTlII_lhl cl. LASER EESONITDRS
`11
`LASER CJWITY MODES
`OVERVIEW
`H.l lntr-:rduc‘lion
`
`11.1 luangitudinal Laser ('_‘a1.'it_v ]'tIu-'.l-es
`FE|.lJF_'f—Pf.'.l'Dl Resonator
`FEtlJF)'—PE.'.l.'Dl |C‘aviI:}' Modes
`Longi tutiinal Laser Cavity Modes
`Longinidinal Mode Number
`Requirements for The Development of Longitudinal
`Laser Modes
`
`30'?‘
`
`31]
`
`315
`3lIS
`319
`319
`322
`322
`322
`324
`324
`32'?‘
`33!]
`
`339
`339
`342
`
`35C!
`
`352
`
`355
`355
`359
`
`359
`361
`363
`364
`
`33"]
`3?]
`3?]
`372
`322
`37'?
`38!]
`38!]
`
`382
`
`9
`
`

`
`xiv
`
`CONTENTS
`
`I 1.! Transverse Laser Cavity Modes
`FresneI—K.irel1IIoIT Diffraction Integral Formula
`Development of Transverse Modes in a Cavity with Plane-Parallel
`Minors
`
`Transverse Modes Using Curved Minors
`Transverse Mode Spatial ]}isIriI:ru Lions
`Transverse Mode Frequencies
`Gan ssian-Shaped Transverse Modes v.'id1En and beyond the
`Laser Cavity
`11.4 Properties of Laser Modes
`Mode Cha.rarleristi=:s
`Effect of Modes on die Gain Medium Profile
`EEIFRENCES
`PROBLEMS
`
`12 STh.E-LE LASER RESU~l'~h'4TDIlS M’-ID GAUSSIAN BEAMS
`D"l'EIl‘r'IEW
`11.} Stable '|I'ur1.'ed ivlireor Cavities
`Curved Minor Cavities
`AECD Matrices
`
`Cavity Stability Criteria
`11.2 Properlies of Gaussian Beams
`Propagation ofa Gaussian Beam
`Gaussian Beam Plnperties of Two-I’vI.irror Laser Cavities
`Properties of Specific Two-Iv[i:I'ror Laser Cavities
`II.-‘lode Volume ofa HeiTnite—Gaussian Mode
`
`I1..l Properties of Real Laser Beaxns
`ll.-I Propagation of Gaussian Beams l_.'si1tgA.BC'fl ]"|-Iatriees —
`Complex Besun Parameler
`Complex. Beam Parameter Applied to a Two-Mirror Laser Cavity
`EEFE IIENCES
`PROBLEMS
`
`13 SPECIAL LASER CAVITIES AND CHIIITY EFFECTS
`O'\"EIl'nI'lEH'
`I3-.1 Unstable Resonators
`
`I3-.2 Q-Swilching
`General Descriplion
`Theory
`Ivl-edtods of Producing Q-Switching within a Laser «Cavity
`I3-.3 Cain-Suitxhing
`1.5.4 Mode-Iiocking
`General Description
`Theory
`Techniques for Producing -.'vlode—Loelring
`I3-.5 Pulse Sliorl-ening Tee'II.niques
`Self-Pltase lvlodulalion
`
`Pulse Shortening or Lengthening Using Group Velocity Dispersion
`Pulse Compression Iflhortening} with Gratings or Prisms
`LIII:ra.5I:|ort—PuIse Laser a.nd Amplifer System
`
`334
`335
`
`336
`391]
`391
`392
`
`393-
`396
`396
`39'?
`399
`399
`402
`402
`432
`402
`
`4H]
`4] I
`4| 2
`4|?
`42l
`423
`
`425
`423
`432
`43 2
`434
`434
`434
`439
`439
`44|
`
`451]
`45 I
`45 I
`45 I
`4515
`462
`4153-
`
`467
`
`10
`
`10
`
`

`
`CONTENTS
`
`I3.IS Ring Lasers
`Mnneli fliic Lrnidircctional Single-Mode Nd:YAG Ring Laser
`Twca-Mintrr Ring Laser
`13.? CI:-Iuplex Beam Parameter An:iI_\'s'B atpplied to ['|rI1rJti~!'h'lirror
`Laser Cafilies
`
`Tl1rce—Mi:rrnr Ring Laser Cavity
`Three- or FI:|L:r—l'h11'rrnr FDCLFSEII Cavity
`I33 Cavities for Prmlucing Spectral .‘H':u'ru-wing of
`Laser Dulpul
`C.avil'_I,.r wilh Additional Fabr}-—Pcrnl Etalun for Narrnw—F'reqLtcnr:}r
`Sclcaetien
`
`Tunable Eaxity
`Bmadtrand Tunable cw Ring Lascm
`Tunable favily I'n:ur Ultranarrow-Frequcncyr Output
`Dislributecl Feedback QDFBJ Lasers
`Dislributead Bragg Reflection Lasers
`I33 Laser families Requiring Snr.Ll]~Diameter Gain Regions —
`Asl'igIn:1liL“aJ]y Compensated Cavities
`l3.]fl Waveguide Caeilies for Gas Lasen:
`REFERENCES
`PROBLEMS
`
`SECTIEDH 5. SPECIFIC LASER SVSTEMS
`
`14 LASER 5‘I"S'|'I-1M5 INVOLVING LD"||hu'—DEHS|T"I' GAIN MEDIA
`G‘h'fl'l-VIEW
`Ir-1.1 Atomic Gas Lasers
`Introduefinn
`I-Ielinm—Nee-11 I.u.9er
`
`General Description
`Laser Suucturc
`Excitatinn Mechanism
`
`Applications
`Argon Ion Laser
`General DI-Z!SL.‘.|'ipIiDl'1
`Laser Structlsrc
`Excitafinn Mechanism
`
`Krypton Ion Laser
`Applicafinns
`He]ium—'|I'adI:ni|II:I1 La.-saer
`
`General Descriplion
`Laser S1J1.1ctLLrc
`E'.!v'.CitE.12iL'fll Mechanism
`
`Applications
`Copper Vapor Laser
`General Descriplic-n
`Laser SI:n.1ctu.rc
`Excitafinn Mechanism
`
`Applicafions
`
`11
`
`468
`469
`4?!)
`
`4?!)
`
`41"!)
`4'F3
`
`-HE
`
`4?}?
`
`«HE
`48¢]
`48!]
`4EI
`484
`
`434
`435
`436
`433
`
`491
`49'
`49I
`49I
`492
`
`492
`4'33
`494
`
`49‘?
`4'}?
`4'31?
`493
`-499
`
`500
`SDI
`SDI
`
`_‘rEl'I
`5:02
`5104
`
`505
`5-CI-5
`505
`_‘r|TI‘
`5|}?
`
`509
`
`11
`
`

`
`CONTENTS
`
`I42 Mu-Ic1.'ul:u' Gas Lasers
`Introduction
`Carbon Dioxide I.a5-cl‘
`
`General Dcscnptien
`Laser Structure
`Excitalicrn Mechanism
`
`Applicalim:
`E:|uc1'Jn1.-rI.asers
`
`General Descfiptinn
`Laser Slructure
`Excitalicn Mechanism
`
`Applicalicms
`Nitrogen laser
`General Dcscnplien
`Laser SI3'ucrurs and Excilatien Mechanism
`
`Applicalicns
`Far-lllfrarul Gas Lasers
`
`General Desclipfien
`Laser SI.=n.I.cture
`Emcitalzi on Mechanism
`
`Applications
`Cllenlical Lasers
`
`General Dcscnptien
`Laser Structure
`Excitnti on Mechanism
`
`Applications
`I-1-.3 X-Ray Flaslna I.-use-.rs
`I.nI1'oclucu'cm
`
`Pumping ErLerg}' Requirements
`Escitnlj on Mechanism
`
`'Dpt.ica1'[‘:1siL1'cs
`X—Ray Laser Trsnsiiinns
`Applicalicns
`I-4.-1 F!1EE+EH(‘IIl'I!|I3 Lasers
`Introduction
`Lascr Slrucrurc
`
`Applicalicnns
`IE FERENCES
`
`15
`
`LASER SYSTEMS HEUDLWNG H1E-H-DEN5l'|"'|' GAIN MEDIA
`l}"r'EI\"I'EW
`
`l5.I Organic Dye [.3-svers
`Introduction
`Laser Slructure
`Excit:-H5041 Mechanism
`
`Applicatiorls
`I52 Sc-lid-St:11cI.ascrs
`lnlroductien
`
`12
`
`511]
`510
`51 I
`51 l
`5 I I
`5 I5
`515
`5115
`516
`5 I7
`513
`521]
`521]
`521]
`521
`522
`522
`522
`523
`523
`51-‘.-
`524
`524
`524
`524
`525
`525
`525
`525
`52.3
`532
`532
`532
`535
`535
`53-6
`53?
`53?
`
`539
`539
`539
`539
`540
`543
`544
`545
`545
`
`12
`
`

`
`CONTENTS
`
`lluhg: Laser
`General Description
`Laser Slructure
`Excilation Mechanism
`
`Applicafions
`Neodyniium Y.-ifi and Class Lasers
`General Description
`Laser Slructure
`Excilsarion hiechaaaism
`
`Applieafions
`Nend3'n1.ium:YLF Lasers
`General Description
`Laser 5I1'I1cL11.1'e
`Excilation !'u'ied1an.isrn
`
`Applications
`Neod_1mIium:‘!t'flrium \-'an:Ldate |i\id:"¢'VO_.J- lasers
`General Description
`Laser Structure
`Etcti Isation Ehiecilanism
`
`Applications
`YIM-rhiIInr.1'.iG Lasers
`
`General Description
`Laser Slructure
`Etci lation Mechanisan
`
`Applications
`Akxandrile L-‘J3!!!’
`
`General Description
`Laser Slructure
`Excilsarion Mechmlism
`
`A.ppiiea'Iiona
`Titanium Sapphire Laser
`General Description
`Laser 5I.n1ct:J.re
`E121" union Ehiechanism
`
`Applications
`Cllromilna IJS.-IF and IJCAF Lasers
`
`General Description
`Laser Structure
`Etci Isation Mecilanism
`
`Applications
`Fiber Lasers
`
`General Description
`Laser Slructure
`El'.C'i Lation ivlechanisan
`
`Applications
`Color CenterI..a3.e1's
`
`General Description
`Laser Slructure
`
`13
`
`54-?
`54-?
`
`54-9
`55!]
`55!]
`55I
`553
`554
`555
`555
`556
`556
`55".!‘
`55".!‘
`55?
`55".!‘
`553
`553
`559
`559
`55!]
`561]
`:16]
`5-62
`562
`563
`563
`564
`565
`565
`566
`56?
`568
`563
`568
`563
`569
`5?!)
`5?!)
`5??!
`SN
`5?]
`_‘r'i'2
`5?'3
`5'i'3
`_‘r?4
`
`13
`
`

`
`Jnriii
`
`CONTENTS
`
`E.xcitation Mechanism
`
`Applications
`I53 Semiconductor Diodt-I.:tsaers
`lnlroduction
`
`FoLI:r Basic Types of Laser Materials
`Laser Strucntre
`
`Frequency Control of Laser Output
`QL:a.ntLu'n Cascmle L.ascrs
`p—[.'Iopcd Germanium Lascrs
`Excitation Mechanism
`
`Applications
`REFERENCES
`
`SECTFDH 5. FREQUENCY MULTIPLIEATIOH OF LASER BEMIHS
`16 FREQUENCY MULTIPLICATIDN OF LASERS AND OTHER
`NONLINEAR OPTICAL EFFECTS
`0I'E|l\"IE'du'
`
`l6.I ‘Wave Pnipogalion in an Anisotropic '|I'r].'stal
`lIS.2 Polarization Response of 3'1aIcI."ia]s to Light
`l6..I Second-flrdcr Nonlineitr Optical Pmccsses
`Second Harmonic Generation
`
`Stun and Difference Frequency Generation
`Optical Pa.ta.1'netric Elscillation
`I6.-4 'I‘IIird-l'.}rder lioillinear Optical Processes
`Third Harmonic Generation
`
`lntcnsit}'-Depend:-.n1 Rcfracnwz lnclex — Self—Focusing
`I65 Nonlinear Optical -Vilalerials
`llS~.(i Phase Matching
`Description ofphosc Matching
`Achieving Phase Matching
`Types of Phase Matching
`II5.'T Satnrahle .-lbeorpttioat
`I63 Two-Photon .-'5tl:-so-rption
`16.9 Stimultttcd Raman Scafl-ering
`Iti.l.fl Harmonic Generation in Cases
`REFERENCES
`
`Appendix
`index
`
`SH
`ST!‘-IS
`5'.I‘v|5
`SM
`5??
`58!
`59]
`592
`594
`594
`596
`59’?
`
`SCI!
`60]
`60]
`603
`604
`
`605
`
`60''}
`Eli]
`fill]
`fill]
`6|?-
`6l5
`{SIS
`GIT
`EIB
`6|?
`El‘?
`
`621
`62.5
`
`14
`
`14
`
`

`
`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
`driillunlesinllrernosldurahleofmanarialsalidoan
`
`of exiaenee!
`
`welrldetaclnedletirioswithintlsellrlrnaneye. They ale
`3 key component ocfsmnenf our most modem cmn-
`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 Ihatis 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 lhve 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 oi
`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} 0‘Pl-lcal feedback {present in most
`
`15
`
`15
`
`

`
`IHIRODUCTFDH
`
`Optical I£I9tJI'IEI.I.Etr or cavity
`)-
`
`
`
`Partlally transmitting
`rnirur
`
`figure 1-‘I Simpiriiecl
`schern atic citypical laser
`
`Fullv retlecting
`mirror
`
`lasers} that is usually prcrvidaed by minors. Thus, in its simplest foam. a laser con-
`sists of a gain or amplifying median: {where stimulated emission occurs]. and a
`set of mirrors to feed the light back into the arnplilier for continued growth of the
`developing beam, as seen in Figure 1-].
`
`SIMPIJCITY OF A LASER
`
`The simplicity ofa laser can be understood by considering the light from acandl-e.
`Normally, a hunting candle radiates light in all directions, and therefore illumi-
`nates various objects equally if they are equidistant from the candle. A laser takes
`light that would normally be emitted in all directions, such as fmtn a candle, and
`ooncerttrates that light into a single direction. Thus. ifthe tight radiaung in all di-
`rections from acandle were concentrated into a single beam of t.i1e diameter of the
`pupil of your eye (approximately 3 mm}, and if you were standing :1 distance of
`I rn from the candle. then the light intensity would he 1,ill]C|,D|I| tinles as bright as
`the light that you normally see radiating from the candle! That is essentially the
`underlying concept ofthe operation of a laser. However, a-candle is not the kind of
`medium tliatproduces amplification, and thus there are no candle lasers.
`it takes
`relatively special conditions within the laser medium for amplification to occur.
`but it is that capability oftalring light that would normally radiate from a source in
`all ditectinrts — and concentrating that light into a beani traveling in a single direc-
`tion — that is involved in malting a laser. These special conditions, and the media
`witltin which they are lztoduced. will be described in some detail in this Imok.
`
`UNIQUE PROPERTIES OF A LASER
`
`The beam of light generated by a typical lasecrcan have many pcroperties 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 much more restrictive than the values for many common
`light sources. We never use lasers for street l]lt]ItttI'tfl2l2ltII't, or for illumination witlrin
`our houses. We don't use them for searchlights or flashlights or as headlights in
`
`16
`
`16
`
`

`
`INTRODUCTION
`
`our cars. Lasers generally have a narrower frvequertcy disllibutionf or much higher
`intensity, or a much greater degree of eoliirrtation. or much shorter pulse duration.
`than that available from more comlnon types ollight sources. T‘l'terIefere. we do use
`them in compact disc players, in supermarket el1eek—out searumexs. in sunregring i.n—
`stm meats. and in medical applications as a surgical knile or for welding £lEl3.C lied
`retinas. We also use them in communications systems and in radar and military
`targeting applications, as well as many other areas. .4 laser is a specialized light
`source that should be used aufjtr when its unique properties are requtireul.
`
`THE LASER SPECTRUM AND WAVELENGTH5
`
`A pardon ofthe electromagnetic radiation spectrum is shown in figure 1-2 for the
`region covered by eulrently existing lasers. Such lasels span the wavelength range
`from the farinfrared part of the speclzlum (.1. = I JIICI pm} to the soft—X—ray region
`0:. = 3 am). then:-:lJ-3' co-venng a range of wavelengths of almost six orders ofrnag-
`nitude. There are several types of units that are used to define laser wrwelengtlts.
`These range from micrometers orrnierons (am) in the infrared to nanometers [nm}
`and angsI.roms {zit} in the visible. ultraviolet [UV ‘Jr. vacuum ultraviolet {VUV ]. ex-
`treme ulrraviolet (ELTV or )[LF"u’ }, and SDfL—X—I'I1)f [SEE] spectral regions.
`
`'WA'tl"ELElllG'|'l-I I.|HI'|"5
`
`l.j'.LIJl = llI|'"5 m:.
`19.: lt]'”’ m:
`1um=1n-fin}.
`
`Consequently. I rrticnzun {urn} : lll.DlI} angstroms (.51.) : l.l}DU'nartometers {am}.
`For eatanlple. green light has a wavelength of 5 2-: ll]‘7 111 = [L5 ptm = 5.000 tit =
`SDI] nm.
`
`HF
`
`CD
`
`D'mIa____:§_eI39
`Ar
`-.n-
`--
`
`.-
`
`N:
`Hubr
`+<rI=
`Ha-are
`l\i:l:‘t'.¢I.G
`Ho-Eu
`
`I
`
`FIR:I.::.or:
`-....
`..
`p
`
`Salt-0-:-Flay
`‘Lasers
`-.
`.. ...-
`
`Figure 1-1 Wavelength
`range ofvaious lasers
`
`“'52
`
`“M9
`
`I
`
`E3‘?°‘.'i"°'."°'.
`.I1n’-
`Ti:_.B.Iz93
`Eu‘: Ill-Roy:
`Ullatnolel
`"tI'is<l:Iio
`lnlrared
`Fal Infrared
`j_'_j.jj..'__j_'_...__l._ _______j!.: _.__.
`Btlt-m
`ttipm
`Jpn‘:
`mm an-nnrn 'II:H:tnm aonrn mnm
`--n-
`j_ j
`
`ENERGY - ..
`
`17
`
`17
`
`

`
`IHTRODLICTEOH
`
`WAVELENGTH REGIONS
`
`Far infrared: 1D to LDDCI ,r.'.m_:
`middle infrared: l to ID urn;
`near infrared: 0.? to l.j'.tI'!‘r‘,
`visible: {14to I17 _r.rn1. or 401] to i"DC| am:
`ullravioleti 0.2 to [L4 ,t.t.t]'1. or EDD to dflfl nm;
`vacu urn uIt.rrrv'io!et'. 0.] to 0.2 rrm. or 100 to 200 rim:
`extreme ultraviolet:
`lfl to 100 nm;
`sofl X-rays:
`I nm to approrrimatelv 29-30 not {some overlap with ELFV}.
`
`A BRIEF HISTORY OF THE LASER
`
`Charles Townes took advantage of the sti mulated emission process to oorrstruct a
`rnicrowave amplifier, referred to as a ntoser. This device produced a ooherent beam
`of microwaves to be used for communications. The first rnasecr was produced in
`ammonia vapor with the inversion between two energy levels that produced gain at
`a wavelength of 1.25 cm. The wavelengths produced in the rnas-er were compara-
`ble to the dimensions of the device. so errtrapolaliorr to the optical regime — where
`wavelengths were five orders ofrnagnitude sn1aI1er— was not an obvious extension
`of that work.
`
`in 1953, Townes and Schawlow published a paper conceming thei.rideas about
`extending the rnaser concept to optical frequencies. They developed the concept
`of an optical arnplilier surrounded by an optical mirror resonant. cavity to allow for
`go-rvtlt ofrhe beam. Townes and Schawiow each received a Nobel Prize for his
`work in dtis field.
`
`In 1960. Theodore Maimarr of Hughes Research Laboratories produced the
`first laser using a ruby crystal as the amplifier and a fiashlarnp as the energy source.
`The helical flaslrlamp surrounded a rod-shaped rub}-' crystal, and the optical cavity
`was fontred by coating the flattened ends of the ruby rod with a highly refiecti ng
`material. Arr intense red beam was observed to emerge from the end ofthe rod
`when the flashlamp was fired!
`The frrst gas laser was developed in l9fil by A. Iavarr, ‘W. Bennett. and D. Har-
`riott of Bell Laboratories. using a mixture of helium and neon gases. At the same
`laboratories, L. F. Johnson and K. Nassau deniclnstrated the firsl neodymium laser,
`which lrassince lJ~ECDEn.EDI1E:Ct'ltl1B mostreiiable lasers available. This was followed
`
`in 19152 by the first semiconductor laser, demonstrated by R. Hall at The General
`Electric Research Laboratories. in 1963, C. K. N. Patel ofE-ell Laboratories dis-
`covered the infrared carbon dioxide laser. which is one ofthe most efficient and
`powerful lasers available today. Later that same 3.-'ear'_. E. Bell of Spectra Physics
`discovered the iirsit ion laser. in rnercurv vapor. In I964 W. Bridges of Hughes Re-
`search Laboratories discovered the argon ion laser. and iii [966 W. Silfvast. G. R.
`Fowles. and B. D. Hopkins produced the first blue hciiun1—cadrnium metal vapor
`
`18
`
`18
`
`

`
`IIIITIIODIJCTIOH
`
`laser. Dining that same year, P. P. S4.‘.|l'Dl.'_lI1 and .I. R. Lanltard of die IE-M Research
`Laboratories developed the first liquid laser using an organic dye. dissolved in a sol-
`vent. thereby leading to the category of broadly tunable lasers. Also at that time.
`W. Walter and co-workers at TRG reported the first copper vapor laser.
`The firsl vacuum ultraviolet laser was reported to occur in molecular hydro-
`gen by R. I-[odgson of IBM and independently by R. Waynant et al. of die Naval
`Research Laboratories in 1970. The first of the well-known tare-gas-—halide es-
`cinier lasers was observed in senon Fluoride by I. J. Ewing and C. Brain of the
`Avco—Everett Research Laboratory in I935-_ In that same year, the Iirstq1.tant|.tm—
`well laser was made in a gallium arsenide semiconductor by J. van der Ziel and
`co-workers at Bell Laboratories. in 1'9TI'IS. l. l‘vl..I.lv1adey and co-workers at Stan-
`fond University demonsuated the iirst free-electron laser amplifier operating in the
`infrared at the C0; laser wavelength. in l9TI'9, Walling and co-workers at Allied
`Chen1icalCorp-oration obtaincd broadly tunable laser outptttftonis solid-state. laser
`material called alexartdrite. and in I935 the first sofl—X-ray laser was successfully
`demonstrated in a highly io-nizedselczni um plasniaby D. Matthews and a largenum—
`ber of co-workers at the Lawrence I_.iverrno.re Laboratories. In 1936, P. Moulton
`discovered the titartium sapphire laser. In I991, M. Hasse and co-workers devel-
`oped the lirst bIue—gneen diode laser in Znfle. In I994, F. Capasso and co—vI.rorkers
`developed the quantum cascade laser. In 1995, S. Nakamura developed the first
`blue diode laser in GaN—based matetials.
`In I961. Fox 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. Unstable resonators were demonstrated
`in I969 by Krupke and Sooy and were described theoretically by Siegman. Q-
`switehing was Iirst obtained by lv'[eC|ung and I-lellwanh in 1962 and described
`later by Wa