激光光谱学基础知识课件.pdf

-118 111111:111uuu111+Basic Knowledge forSpectroscopy:Absorption and Emission of Light21.1 Plancks Radiation Law and the Einstein Coefficient.71.1.1 Density of field modes in a cavity.81.1.2 Quantization of the field energy.101.1.3 Plancks law.121.1.4 Fluctuations in photon number.141.1.5Einsteins A and B coefficients.151.1.6 Characteristics of the three Einstein transitions.181.1.7 Optical excitation of two-level atoms.201.1.8 Theory of optical attenuation.241.1.9 Population inversion:optical amplification.281.1.10 Radiation pressure.321.2?f)pf.341.2.1mkf.351.2.2pM/.361.2.3.371.2.4 BXL.401.2.51.411.2.6.?.421.2.7 Light Shifts.441.2.81|?f.451.31.Width and Profiles of Spectral Lines.491.3.1O.501.3.2O(Power Broadening).571.3.3kZ.?.581.3.4-EO.611.3.5VOpd/.631.3.61Transit-Time Broading.681.3.7/.691.3.8!.711.3.9O.731.3.10.731.41Y1Discrete and Continuum Spectra.75111111Spectroscopic Instrumentation772.1Spectrographs and Monochromators.772.1.15UBasic Properties.782.1.2c1OPrism Spectrometer.871-112.1.311OGrating Spectrometer.882.2Z Interferometers.932.2.1VgBasic Concepts.942.2.2ZMichelsoninterfereometer.952.2.3Mach-Zehnder Interferometer.992.2.4NZTunable Interferometers.1182.31OZmComparison between spectrometers and interferometers.1192.3.11E+Spectral resolving power.1192.3.281+Light-Grathering Power.1212.4(Accurate Wavelength Measurements.1222.4.1 O(Precision and Accuracy of WavelengthMeasurements.1232.4.2Today.s Wavemeters.1242.51&Detection of Light.1262.61&.1262.711-1Laser as Spectroscopic Light Sources.1302.7.1-1?Fundamentals of Laser.1302.7.2KThreshold Condition.1312.7.3Rate Equations.1342.8-1?nLaser Resonators.1352.8.11?nOpen Optical Resonator.1362.8.2?nmSpatial Field Distributions in the Open Resonators 1382.8.3Stable and Unstable Resonators.1402.8.4Ring Resonators.1402.8.5?nFrequency Spectrum of Passive Resonators.1422.9Spectral Characteristics of Laser Emission.1422.9.1-?n-1Active Resonators and Laser Modes.1432.9.2O?Gain Saturation.1442.9.3m?Spatial Hole Burning.1462.9.4-1OMultimode Lasers and Gain Competition.1472.9.5VMode Pulling.1482.10-1?y.1502.10.1Line Selection:-1N-1.1502.10.2Suppression of Transverse Modes.1542.10.3Selection of Single Longitudinal.1542.10.4.1622.11-1Linewidth of Single-Mode Lasers.1652.12N-1.1672.12.1N4+-1Semiconductor-Diode Lasers.1682.12.2/-1Dye Laser.1722.12.3Of-1Excimer Lasers.1732-11111nnn-111VVV444111FFF111111Doppler-Limited Absorption andFluorescence Spectroscopy with Lasers1753.1Advantages of Lasers in Spectroscopy.1753.1.1 Classical absorption spectroscopy.1753.1.2 absorption spectroscopy with tunable lasers radiation sources.1763.2High-Sensitivity Methods of Absorption Spectroscopy.1773.2.1 Frequency Modulation.1783.2.2 Intracavity AbsorptionnS.1813.2.3nSP(cavity ringdown,CRD).1843.3Direct Determination of Absorbed Photons.1853.4Ionization Spectroscopy.1883.5Laser Magnetic Resonance and Stark Spectroscopy.1903.6Laser-Induced Fluorescence.191111ooo555-111111Nonlinear Laser Spectroscopy1944.155Linear Absorption and Nonlinear Absorption.1944.2!?Saturation of Inhomogenerous Line Profiles.1964.2.1 Bennet?AHole Burning.1964.2.2=0Lamb Dip.2034.2.3?1Saturation Spectroscopy.2034.3?1Polarization Spectroscopy.2134.41f1Multiphoton Spectroscopy.2174.4.1V1f.2184.4.2V1f1.220111111($)!VVV?-111111Optical Pumping and Double-ResonanceTechniques2235.11.2235.2V?-11.2295.2.11-V?.2295.2.211V?OODR(Optical-Optical Double Resonance).2315.2.3 SEP(Stimulated Emission Pumping)1.237111888VVVVVV-111111Doppler-free and sub-Doppler laser Spectroscopy2436.1VV1f.2436.2fV-u1:Sub-Doppler spectroscopy in molecular beam.2476.3VY1OODR-u1.2556.4?1.256111mmmEEE111ZZZ111(Time Resolved Spectroscopy and Coherent Spec-troscopy)2587.1Generation of Short Laser Pulses.2597.1.1 Time Profiles of Pulsed Lasers.2593-117.1.2 Q-m-1(Q-switched lasers).2627.1.3 Mode Locking of Lasers.2667.1.4(Kerr Lens Mode Locking).2697.1.5 optical pulsecompression:1:c:?:.2697.1.6C-1).2787.2Measurement of Ultrashort Pulses.2817.3Lifetime Measurement with Lasers.2867.4Pump-and-Probe Technique.2897.5Z1Coherent Spectroscopy.294111lll-111.111Laser Raman Spectroscopy2978.1.VgBasic Considerations.2978.25-1.1?EExperimental Techniques of Linear Laser Raman Spec-troscopy.2988.35-1.1Nonlinear Raman Spectroscopy.2998.4.1AApplications of Laser Raman Spectroscopy.302111-111111333zzzAAAApplications of Laser Spectroscopy in Chemistry3039.1-113zA:(&.3039.2-1pzA.3039.3-113AA.3049.4-13zAA.3059.5-1l.3069.6-13f!?f-EUD4LA.3099.7-113i$.310111-111eee%?fffOptical Cooling of Atoms by Laser31210.11|?f.31810.2p?f.32210.2.1?f-1.32210.2.2?fO=?z.32610.31Ve%.33010.3.1.e.34010.4?fI?n.34010.5-1?f.34110.5.15?fX1.34110.5.21.34210.6 summary.3441113471113484-1111:1u1+Basic Knowledge forSpectroscopy:Absorption and Emission ofLightLASER:Light Amplification by Stimulated Emission of Radiationg5gOd1960cgTownes/Basov/Prokhorov:1964cn,u-1Herzberg:1971cz,f1Schawlow/Bloembergen:1981cn,-11:1997n,-1e%?fZewail:2000z,-1zKetterle:2001cn,-1e%,BECC-12002c?1?ff(?A?k?ff(?5g1.1?ffnzf)?z:1?ffNXU?;r;g,-u;Vu?ffu9;-EL?fmU&E;Zeeman?AStark effects4;(?gp;mE1&E!-1:1.5:1u1rUd,15,:5(86),605.7nmk0.00047nm(?u400MHz);He-Ne-1632.8nm,-1108nm(?u9MHz).A:X?,=,?1,1?E.2.5:=15?5d.?,1u?,55-11:15&,1uk0.01rad(1rad=57.2960),-1u3 104lA:-1-1X,X,?Jp,-1?1l/&,?5AOr,Z6,|-1p5u5-1%,|-13,?Y|,c,/kA.3.Z5:3fGS1fZfG1fKZ1Z555n,5,Zm,5,Z.-18p55u,rZ1.mZ5(108A),ZApmZ5k-1:Z1A:=E?31y,Z1&E?nu5.X,1GpC,EE,E;3-1y?y.4.5:15.1U3mp8:3,rB?.-1p551U3mp85Ly,o,-1p5K1U3mp8,-1NB?.y(1012s),(1015s)C(1018s)?-1.,&NL,qL,)LCz.5.?:L13Srfn-15,?L?O(,=-1?S,L-1p5,5,Z5,5nn:|=1mWC-1?,?p100N-1?L?p1010A:-1p?kA.?-13?:NC)AZAp,U,JL77Lzz.-13S,mmSm?S5UU,1D-1n:.1.-11n:du1pA?41nU1&E?u4oCU1&E6-112.-1,Im94:?|;n-11n;knr-1lLz;N(5);(!)6663-1?fw(AFM):7-11&?7&?3LApE,5&NLf&?k3?u?GCu&?&?k3?f?d?u)Cz?UClk?-1Lc,KBL/,?l&?51#?u)ZZ&?Czd&L?fu?5LCzuu?u?7L!aU:N(X?Al2O3);N(X,/);N(XHeNeCO2);N(Xz;,GaAs);8-11.U:Y(104W);(1014W);n!4b?(100nm)1(1.222mm)5-1|?ffPfU?)gdf-1)pUf345?OCzc|$ufU=-1U(J51E1?-/rN?ff5p:?f-:-1,q?f-(-1)(atom laser),up!pZ5!$u?f,31Af1 1eVb0.380.4551f1 1eV7,0.4550.49210.4920.57710.5770.5971?1103 102cm10.5970.6221?1103 102cm10.6220.781?1103 102cm1C?0.81.31?1103 102cm1?1.33?1103 102cm1?38?1103 102cm19?814?=1U=?f=kU1905cEinstein1?Auf5b5)1926cf1fPlanck,Einsteinufuf,?f)k1917cEinstein?fpu?fu1n6u?(y3E2|fzE,B7LfL?;nN(1A59?fp(JPlanckfb3;n:b=|UOThe main concerns of the present chapter are the thermalexcitaion of electromagnetic radiation and the basic konds of interaction that occur between orlight and atomin transition10-11!99-u(1)?fmUu)pa.ynpXL1?fu-u9ALOduunA?u9XX,?u1?fNO1?fp)?A1.1.1Density of field modes in a cavity?vkn?un?nnm3km(Jbn/GA5/nL,p93n.|EPlancknL3T,9enSNTNO5(1)n|m|-u8LO;we consider the spatial dependence of the field in the cavity and derive an expression for thenumber of different modes of excitation of the field(2)|mA5OTz-uUwe consider the time dependence of the field and calculate the energy carried by each excita-tion mode at temperature T.13m|v2E(r,t)=1c22E(r,t)t2,(1.1):wave equation.E(r,t)=0,(1.2):Maxwell equationv.)keEx(rt)=Ex(t)cos(kxx)sin(kyy)sin(kzz)Ey(rt)=Ey(t)sin(kxx)cos(kyy)sin(kzz)Ez(rt)=Ez(t)sin(kxx)sin(kyy)cos(kzz),(1.3)pE(t)(wavevector)kkekx=x/L,ky=y/L,kz=z/L,x,y,z=0,1,2,.,(1.4,1.5)k?=k=kbeknK|E(rt)nvk|11-11NyE(rt)v.XEx(rt)3y=0,Lz=0,LecosUsin.v?U3n?:vMaxwell(1.2)(1.3)?:k.E=0,(1.6)=EkRzk,E(t)k?(transverse polarization)=1,2I.Ux,y,z,z|(x,y,z)nS|(?A|gd)?|-uL|5#Nkxnm:/L3k k+dk|8Lu3k k+dk1/8:8z:mN(/L)3,be?v(/L)3)K18(4k2dk)(/L)3 2,(1.7)|(k)nNk8the number of modesper unit volume of cavity having their wavevector in the specified range)d(1.7)(k)dk=k2dk/2,(1.8)(JnA5(angular frequency)X:=ck,(1.9)()d=2d/2c3.(1.10)|PkP=1,2R(V k2/2)dk R(V 2/2c3)d,(1.11)pVnNz?12-111.1.2Quantization of the field energy1OTz|;U(1.3)(1.1),|(1.9)2E(t)t2=2E(t),(1.12)?f$)E(t)=E(0)exp(it),(1.13)E(0)3;nk?;n3|UL:12Rcavity(?0E(r,t)2+10B(r,t)2)dV,(1.14)?0:the electric permittirity(0)of free space0:the electric magnetic permeability of free spacec=(?00)1/2,(1.15)E,B|(1.3),(1.13)E|E(vecr,t)=B(r,t)/t|UB?S|USUCzAenNIt is convenient to average the field energy over a cycle of oscillator since the energy variationthat occurs during a cycle is not usually susceptible to measurement-75The cycle-average theorem:A,BEmCzeit,KA,B(A)(B)=12|k?kXdd(1.14)?zoU12Rcavity?0|E(rt)|2dV,(1.19)y3PlankfzbK31900cb|zuUU(qh?Ufhq.Ufh1f.KhL?.q1|kUqh.3;n1.19|Uk?(1.13)E0k?|E(t)v(1.12)?fTef?nK?fUUEn=(n+1/2),n=0,1,.,(1.20)dd:13-1112Rcavity?0|E(rt)|2dV=(n+1/2),(1.21)w,fz(1.13)?E0ky3|;?n=|UAfz?n7L|f?n?NK;Cqv|fn|zfz?fX1.3L?fU?Ud(1.20)En=(n+1/2)A?f?u1n-?n=0?f?uLEkU1/23u|?f:U?2?|*(the factor that governs the observation)puU?UEn=(n+1/2)3:UNnUff(quanta)1f?3TO(?)f)(?)1f1.4LOSc|X?f$AU?5?fzk?14-111.1.3Plancks lawT,939d)oU3APn?f9-u1n-uLBoltzianfPn=exp(En/kBT)Pnexp(En/kBT),(1.22)kB,Z=Pnexp(En/kBT).ZX8zfPnPn=1(1.20)fUL:U-eU=exp(/kBT),(1.23)K9APn=Un/PnUn,(1.24)1:Pn=0Un=11U,(1.25)dkPn=(1 U)Un,(1.26)3T|p-u1fn:n=PnnPn=(1 U)PnnUn=U1U=(1 U)UUPnUn,(1.27)p(1.25),(1.26)|(1.23),1f:n=1exp(/kBT)1,(1.28)(JPlanck9-u15-111.53Te9-u1fn31?Uyez1u?u11.6uTUPlanck1.10(1.28)ON3+dm|83z,TUn+:U85TUWT()d:WT()d=nd=n3d/2c3=32c3dexp(/kBT)1,(1.29)uUWT()Planck3p$4Planck/:kBT ,WT()2kBT/2c3,(1.30)16-111900cRayleighRayleigh;4=PlanckukBT|5gTn|ko|UC:R0WT()d=(12V)Rcavity?0|ET(rt)|2dV,(1.34)1.1.4Fluctuations in photon number1fuLynS|z1fu)kAI3?L,5=kIOnmq3(GX?bqX8XnXnXUX?A3UGu1f?3nA|/7IXndqn|Xnznk,(81fA1fnd(1.26)Pn(1.27)1fO(J(1.28)d/wXnw3n1fmmmmAmw/Unergodic theorem of statistical mechanics according to which time averages are equivalent toaverages taken over a larger number of exactly similar systems,each maintained in a fixed state.Thefictitious collection of similar systems is called an ensemble;the system in the ensemble are distrib-uted among their various possible states in according with the appropriate probability distributionfor the system considered.APn5(nn?d(1.27)kU=n/(1+n),(1.35)(1.26):Pn=(nn/(1+n)1+n,(1.36)nrPnn5B/1.7fAPn|1f?1gwn=0okAPnnON?BoltzmanApU?f?(JPn3n=nvkA517-11Planck1fAPnk9the geometric distribution.1f8?dnx(n)2=Pn(n n)2Pn=n2(n)2,(1.39)n2(n)2=2(n)2,(1.40)n=p(n)2+n,(1.41)w3noun,unkn=n+12(n 1),(1.42)1fO?n3?ATn(J=n?n?1fzg=ImuAI5?SkEm(JEmuI?k1.1.5Einsteins A and B coefficientsy3?fpLnEinsteinn5n)NLX?f1-1118-11Einsteinn3?f1funnbbvpLf?n?3Einsteinnvkwfb?fU?vk7|Ufzn9?fpnS?ffpbN?f?Nunz?fkPU?E1E2=E2 E1,(1.43)1f?fu?f3mLUU?fU?Og1g2?fU?P?uE1,E2?fN1N2N1+N2=Nl?w?f9-u4nkNX?fmpIE,X4BLnT1r3n;.?3UL9WT()WE()L?oUW()=WT()+WE(),(1.44)WE()n?k9m5p6#PA5?EinsteinnboU3?fU?NCC7L1fuAXe?f32mkkAA21?fgu$U1uU1fA21(Spontaneous emission rate)y?u1?fevk?fU2UU?e3UW()K1 2LU1fyAbuW(),XB12B12W()(absorption rate)19-11L*n?3dW()OrU?eU?Aw,yOr7Lu)PB21W(),p-B21W()(stimulated emission rate)A21,B12,B21W()=?fU?kdfy3?nnU?Kb?fuNvN1,N2mCz1wN1,N2UCdN1/dt=dN2/dt=N2A21 N1B12W()+N2B21W(),(1.45)(1.45)H9Ak(Jn?fU?Kb?fNvOu5N1,N2mw/CzdN1/dt=0dN2/dt=N2A21 N1B12W()+N2B21W()Odn$L9L.,=m,d(1.45)N2A21 N1B12W()+N2B21W()=0,(1.46)9vk?n(1.46)U9?zWT()WT()=A21(N1/N2)B12B21,(1.47)U?N1,N239BoltzmannseXe:N1N2=g1exp(E1/kBT)g2exp(E2/kBT)=(g1g2)exp(/kBT),(1.48)d(1.47):WT()=A21g1g2exp(/kBT)B12B21,(1.49)WT()LdEinsteinXBoltzmannAu?fU?(JATPlanck(1.29)u9ULekT=?:g1g2B12=B21,(1.50)h32c3B21=A21,(1.51)nEinsteinXpXJ-uLEinsteinnPlancksU-Lg,/1unu(1.50),(1.51)EinsteinXmXk?5XuUWT()m59?Um5?1kA5X111?(1.50),(1.51)Eu1?ffNN=A(orientations are randomly distributed)NXNNp5=?ffpU5?BX?1A?1NpK,?N?ffU3(51A5?91fAPnPn=(1 g1N2g2N1)(g1N2g2N1)n.20-111.1.6Characteristics of the three Einstein transitionsku?nLA5.ALCq.k39nuL.Planck(1.29)(1.51):B21WT()=A21n,(1.52)=9-ugu3|1fu:B21WT()+A21=A21(n+1),(1.53)ul(1.28),(1.52):A21B21WT()=1n=exp(kBT)1,(1.54)n 1 for/kBT 0.7?nT=300K 50m,(1.55)=A6 1012Hz,?kBT1d?A kBT A21 kBT A21 B21WT(),(1.57)=guu9-99UWT()?1013Hz refer to optical electromagnetic radiation as ligh.3eW()wk?1?z1?(optical experiments)3C?1b?;.:3 1015s1,3 1019J?5591fA,L n1+n=g1N2g2N1,(1.58)Pn=(g1N2g2N1)n(1 g1N2g2N1),(1.60)5g?11X-uu)31Lk?z.oU(1.44)W()5g?1?zWE()LeIE?%L)d?-uu?.?U(saturation radiative energy density)Ws=3/2c3.v21-11WsB21=A21=?U-uuguuu1N-U3dWsd 1014dJm31rrI=cWLA?rIs=cWs=cA21/B21=3/2c231 3 1015s1Isd=3 106dWm2D16 1010s11rRdIs 1.8 105Wm2;.u1010Hz,Ad=21010s1.BW=A,K1r2 105Wm2.wrD1v)r1r-ugu-1c-1r1XU)v1r-uguuu1A?k?f1f/guu#dlm?1A1r|!1fnS1f?I(W.m3)E(V.m1)n/V(m3)1f/1061021014102cw laser10510410151020pulse laser101810810181018LrD1r?1r?1A?k1f?f2Lguu5-11rNL?uOdn3(n-u11OdXAB?fs?1.9LUu)nLA5Ad-?f-u)1-u1knu1k1A5-u1rOr()?5C-uA5y,guu)11?u?vUnguu1Du15guu1?22-11?1?fG$UpU?f(N1,N2)C?1L?fNduL1f?-u?fd-u1f8u1XJ3L?G1L?fNrUC?,?fLguuUkXe#uA21A21+B21W=11+(W/Ws),(1.64)guu1(J1PB1L?fNmL*ATrN+”o9-uUWT()3?A(1.57)gupu9-u9?pu1013Hz,?9UCqoU(1.44)W()5g?1?zWE()LeIE?%L)d?-u3e?31?f-k?9k$(=?f)91-?f31.8$U?9N1=N=?fv?(1.43)?1?f5yA-U?E2J5-udTX1wU?fU?vN1+N2=N,(1.61)U?/AO?U?(g1=g2=1)(1.50)BXC.dAXBXeI(1.45)z:dN1/dt=dN2/dt=N2A+(N2 N1)BW,(1.62)Wg,n)U3?WnC3!?X?nXJWXK(1.62)mk,UIO)k(1.62)N2A21 N1B12W()+N2B21W()=0,(1.46)N2A+(N2 N1)BW=0UN2Ws+(N2 N1)W=0|N2+N1=N?fN1=A+BWA+2BWN=Ws+WWs+2WNN2=BWA+2BWN=WWs+2WNdd?U?u?U5Cz?W Ws6C551?f?(saturation)?U.?1?A?23-11Steady-state atomic populations as functions of radiative energy densitynOd(W=)absorption:N1B=NA(Ws+)(Ws+2)Wsstimulated emission:N2B=NA2(Ws+2)Wsspontaneous emission:N2A=NAWs+2ewgu8?Uz?fwU-uC56X,U?N/2guuCA/2U24-11Mean rates of the three Einstein transitions in Units of the A coefficient as functions of theradiative energy density.y3?fm6(1.62)3(1.61)e):N1(t)=N1(0)NWs+Ws+2exp(A+2B)t)+NWs+Ws+2zXJt=0k?f?u?51mK?f?u-u8N2(t)=NWs+21 exp(A+2B)t?m(A+2BW)t 1,(1.73)-?fCN2=NBW/(A+2BW),(1.74)?1m?f$-Ud1=?f?G?fk;UN2=NBWA+2BW=NW(3/2c3)+2W,(1.75)l=U1?fp(J1fm#-um6eNumber of excited atoms as a function of the time tXJy34?51-u?f-uULguuL=y3t=014KkdN2/dt=N2A N2(t)=N2(0)exp(At)26-11zPC?fufu1rUm6XP*?F1u?OdAXR=1/AR?fflurescent or radiative lifetimeN2/Nw?f?u-A?f-um?,?A?f?#u1fEeUAuAmmu)?Xd(1.74)N2/NA?f-um1.1.8Theory of optical attenuationc!LbU.1PUrDl?.!u?fOdnPL.p,b?f-ukw,?1r1Dz.!e!b11,uc!7n.31PL*5ckV)eu*MaxwellIOPnn?fNw0dielectric mediumIIOBL0*n1rdPoyntingI(z,t)=0c2E(z,t)B(z,t),1.8.1n1w1r3P0attenuatingdielectric materialUeDlUC=expK()z,1.8.2K()=2()/c,1.8.3nK()3PX(attenuation coefficient).1X(extinction coefficient)()Le(refractive index)()()+i()2=()=0()+i00(),1.8.40(dielectric function)()NyA5,0,00OLJ.,e3,00,K1X(),du)1P.05zX(linear susceptibility)(),0()X()=1+(),1.8.5zX()01A5./dA.O.?1X.1.du03?|E)4zP?|r4zu|P=?0E(1.79)?=1+0du03XC(kc/)2=1+,(1.80)=0+i00,(1.81)kc/=+i=n,(1.82)27-11:refractive index,L:extinction coefficient,Ln:n=?=n0 i,n0:L:L()=Ne2|D12|23?0V0+i(0)2+2+|V|2/2,(2.122)2.122)2()=Ne2|D12|23?0V0+i0(0)2+02+(0/)|V|2/2,(2.138)zDE=E0ei(tk.z),3zLn0k=n=0?,kn=k0n,|k|=2/E=E0expi(t kn.z)E=E0expi(t 20(n0 i).z)E=E0expi(t 20n0.z+i20.z)E=E0exp(20.z)expik0(ct n0.z)EnJL=D,6u:vp=cn01+vgL:vg=ddk=cn(1+ndnd)=cn1+ndnd:3?Dn)DdkVg+z:?3()?)?|5d|XaA|+:|r?|(r)I|F|KF,=k=(r)?=|(r)|=k0n,k0nvp=1/|(r)|3!0nvpduvk1|ULn5m!3()30kD41&1&E1z1wX1U1()L0D3DLu)C:DdU”D”+vg=dd+UDL&DBohm5fn6:In general,the phase velocity has little physical significance;for example,the speed oftransmission of a signal through a dielectric is given by the group velocity,as is also the speed oftransport of energy.Un?y?1u,k?u11ucS?&3Dd+28-11d&oucu1e+L&01Lc01+L1?+2L&;Kramers-Kronig dispersio