Opticslecture7

Opticslecture7 - 7’/ Wh'a‘fare. Lasers ? Lasers are...

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Unformatted text preview: 7’/ Wh'a‘fare. Lasers ? Lasers are gouava OQQ ‘fewpolallj aud §P3£IVQ(/j cera‘mi— Beére. [2SeF5 we owl; lac] {Mcoflereq'I‘ sum/6314+, @365, 1933.385! fléaurcsww'K/gfzctéa e41. (MAO/(€55 8% flower fre7uemc<es ‘flxpét as raAbwaues I 5119(4- Waues I microwaves , Fania?! (3-H, we are uses! +0 Clea/{Mg wI-l’hs'rn'cfly Co aercwi’ waves , V f (It/(43‘; l5 cofieremce Le’ths xgooka'll a p/atae wave, propaga—Huj alougz. EWPWBZ COAQ‘GV‘W Z L? 5%",90131f 4 we can predfc'f [3/4356 0913438 wT‘H” #AMQ t/ 25 fat“ exam/Me ll»; 6&5 wf/ we fiave +ewP9/2,£ Cerrence, Ifl V1013! "MW: Wat/e 1'5 1L€MAF, Waders/Ct (9Le(€vtce; ' % we can P/fidtrC-IL #48 phase 3.1L pi, 5 wire” / Paase 22‘le pi, fl [5 known, we ASH/e §pa7lzr944 \\ ‘ KN .3 Coherence, P/ane wavesare coéereut’ 5,3752 p55“ f0” arm) 9 arc' Mi? 5.91445. 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M l/‘Ouj ‘ 3 Populaflo" Wersum s‘fzvuula'f'ca‘ . ew§ssmm i % Lasers (He-Me I Yflé 'efi) Mafiers The“: Can be [HINDI/16» 0£BIEG7ZF0M$ 34%6 ambled 6+2+el pumped up +0 H” by an eX'I'efwa—é' scarce, {fem +L\e ground €+a+c wL‘erc: elealroots nerwfll ., , , J A {{ve, . 4V1 eléalrom relaxmg 40 nLS groumci Sfa‘ée. w”! em‘rt factfa‘hromlaccotdzug 1% [9/81/2155 Ia“) £= 7%; Jfi ea»on dad/ran.) give$ 0107f €MMjé/Hme 0% [0° “1317‘s and {fl were are. A/elemLmM} re‘exfnj I fie». :: 3 D wig-fa e o Eda A /V I 9 )4 laser, flera/arel proJuces radiaelfou 34 3314+ {vefiqeha'es/ Similar % 1413+ ofi RF and wfuoufade radfa‘h rs . > 0 v >5 $0 C [-1-] Ground state M Stimulated transition ‘—-—¢—={> Spontaneous transition He-Ne laser energy levels. “i? fL ~» g) _ (.50 51”"‘1; LLsz What is a Laser? Light Amplificaiton by Stimulated Emission of Radiation Classically speaking, a laser is a very high frequency oscillator of electromagnetic waves 9.9., for red light: . .14 fl 5‘ i=600nm, 9=clk=5x10 Hz,C—3x10 M/A Analog! with an electronic oscillator: ° gain _ ' feedback (positive) ut ' Feedback ' " o Coherent vs. Incoherent Light: _ «9 incandescent Bulb 3;! o Stimulated Emission rate at which photons are coherently added to the incident light as the electrons jump from levels 2 to 1 o Spontaneous Emission rate at which the atoms jump from levels 2 to 1 emitting incoherent photons ._ 9L2 dt 241 Q} 1 o — rate of absorption is proportional to N1 — rates of stimulated and spontaneous-emission are proportional to N2 — absorption and stimulated emission rates are o< L, o The rate of stimulated emission is proportional to the rate of arrival of the incident photons in an area A2 in thevicinity of the atom. 7% Fabry-Perot Laser: I R = mirrors reflectivity T = mirrors transmissivity 0 Consider a Fabry-Perot (F P) laser as shown above. The mirrors (cross—section A) are assumed lossless so that R+T = 1. Suppose the interior of the F P cavity is filled with 4-level atoms. We want to calculate [out for a given Iin, i.e., the gain of the FP amplifier. 0 Prescription: -— Sum the fields of the multiply reflected plane waves within the F P cavity. - Due to the gain, each partially reflected compo~ nent is multiplied by exp[(a + jflfll in propagation from 2 = 0 to z = Z. Recall that I,,(z) = 1.,(0)¢“<">‘. —- Both a and ,6 are functions of 1/. a(u) 2—- a(u)/ 2 and ,B(u) s2: 27rnV/c = 21rn//\ = nk. 7'7 7'8 —°{Z fprCaHJ ok (5 Megahvc. I[z)=I(o 9, fig- '2. 30:1” M a gain wetltruwx (diwml-ewififoa) I fifii. Z Opflcaé Resonators 097‘. oscil/mlar d ars psi-(Ive, Aim W“ , (age 3 J; '- Nflfef. , ’4; mi «0 r 2 Wk #16 need 91’ Lé$€FS 7'? Befixe fiasers/ 4o oHaIm (oiapreu'f- LIéF/T‘! we #0 flake a Siromg opflcafi ffgéfi sauna Qua) pass H" b r ' Q Y r r ’Hanamfi‘n a 7(IM\/’["}l‘lhy [3114on”: m an OWLQFrwiSE‘. opaque. SC€€€VI° ‘M‘Ie PMLME. W83 cm {pfgipf' a}. 7% 9r =<Zma-~’r,{,a.,r i V r LL36» QWWWM $8413")! Cogerewfi .ffgW, But 4’46. [MLem u l 4%; y? r '5‘ I was reauced via an QA/‘hPme/j fafmf r r ' ‘ . K I Kit/Q 3 ‘3 I was; a M :41: Ha+€wlpgi22ffg 1MC€>Lifif€wfi pair/if goat/ca} fa aié #We i, ) I4 9w} 5 37L game {9122356 (3‘90 CamI D) l! ‘1 155/ ” H " Boat/L M9 phage rdvlfoud»? gala/€964 [minis fian/‘C M game/D, In order 40 wake +L\e Pinho‘e £,’8&+3/50 7L€Vvlfl0/Q//g‘ (Ogevemfi) P395 'lmcowjug +L/oualn pftrél/MS u/l’nthl “3‘. \I reduce +145 {faciuauc CDM¥€M+. BWZ' 7%75 cat'l/ (27334, r‘eéuce +Luz lm‘femgf-E? 0&2 fifgw‘f, EVevn (u; Owe copped; 16+ 52 single, {ragga/nag jam/‘4 3 park/w: 9K 3 #l'lLf/'r!50 as 7‘0 ma/re a Pinhofe wave kwperaflj cohereme E‘L (DOM-poi be age-Zea; a/l P/3C%;CP£ Par/M993) [,e no CD player. ,4 L655? Outfit? mater hand ((5 a powerfufi source. of spavlz‘a/lzyMfiMPocg/g 50%,»va 6327’”, ...
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This note was uploaded on 04/17/2008 for the course EECS 202 taught by Professor Plonus during the Spring '08 term at Northwestern.

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Opticslecture7 - 7’/ Wh'a‘fare. Lasers ? Lasers are...

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