precision spectroscopy diode lasers and optical frequency measur docx

United States Department of Commerce Technology Administration National Institute of Standards and Technology NIST Technical Note 1504 Precision Spectroscopy, Diode Lasers, and Optical

United States Department of Commerce Technology Administration

National Institute of Standards and Technology

NIST Technical Note 1504

Precision Spectroscopy, Diode Lasers, and

Optical Frequency Measurement Technology

Edited by

Optical Frequency Measurement Group Richard Fox

NIST Technical Note 1504

Precision Spectroscopy, Diode Lasers, and Optical

Frequency Measurement Technology

Selected publications of the Optical Frequency Measurement Group

of the Time and Frequency Division

U.S DEPARTMENT OF COMMERCE, Wiliam M Daley, S

‘TECHNOLOGY ADMINISTRATION, Gary R Bachula, Acting Under Searetary for Technology NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, Aaymand & Kammer, Diector

Precision Spectroscopy, Diode Lasers, and Optical Frequency Measurement Technology

‘Additional publications mentioned in Section VI are not included here, but are avaliable from the Time and Frequency Division Orica For more information, visit our website at ˆhfp/Awwaw bldroe goufimtefreg or phone: 303-497-8276, Fax: 303-467-8461

‘Other NIST Publications may be purchased from the U.S Goverment Printing Office {GPO} The GPO website is hp iiwiw.access.gpe.gov/ or phone: 202-512-1800 (Olcer publications may be purchased from the National Technical Infermation Service whose website is mtpwww nts gov! or phone: 703-487-4850,

Acknowledgments: A number of people have worked with our group during this time period and the results presented here are due in large part to ther aforts Special Fecognition goes to the mary important contibutions of F Bondu, J Kitching, N Mackie,

‘J Magyar, J Marquardt C Oates, M, Stephens, C'S, Weimer, JS Wells, A'S Zbrov,

‘and TP Zibrova’ We have also benefited greatly ftom colaborations with guost researchers from around the word, including A Dax, L DEvelyn, M.D Lukin, M Mlrtz,

DE Nikonov, KP Petrov, O Pister, U Simon, G Tio, DA Van Baak, V.V Vasile, and L Zink ‘Partcularly important to our research program have been our longterm Collaborations with V.L, Velichansty et al rom the Lebedev Institute, Moscos, Russia: F.K Titel and RLF, Cur et al, from Rice Univ M.O, Scully etal from Texas ABM Univ

M inguscio et al from Firenze, laly, D Welch et al fom SDL Company, and AR Ravishhankara et al from NOAA, We gratetuly acknowledge the continual guidance and help provided by J.C, Bergquist and J.L Mall) Our special thanks to Anna Dillon and Wendy Ortega for their diigance and organization in the tedious task of bringing all these papers together into @ echerent package We also acknowiedge the partial

‘support ofthis work fram the Air Fores Oifie of Scientific Research, ang NASA

‘Time and Frequency Division

National Insitute of Standards and Technology

325 Broadway, Boulder, CO 80903

December 1897

PARTI LASER SPECTROSCOPY

“Hyperfine Stricture of the Metastable "S; State of "0 Using an AlGaAs Diode

Laser 77 nm." GM Tino, L-Hollberg, A Sasso, and M Inguscio, Phys, Rev

“High-Resolution Diode-Laser Spoctroscopy of Calcium," AS Zibroy, RW Fox, R Ellingsen, ©.8 Weimer, Vi Velchansky, GM Tino, and L Holberg, AppL

“Sub-Doppler Frequency Measurements on OCS at 87 THz (34 ym) withthe CO

Overtone Laser." A Dax, J Wells L Helberg, AG Maki, and W Urban, J

“Sub-Doppler Frequency Measurements on OCS near 1689 and 1885 CM!

JS Wells, A Dax, L Hollberg, and A.G Mak J Mel Spactose

“Detection of Methane in Air Using Diode-Laser Pumped Diflerence-Frequency

Generation near 32 um," K.P Petov, S Waltman, U Simon, RF Cut, FK Tie,

EJ Dlugokencky, and L Hollberg, Appl Phys B 61, 553.558 (1895) [TN 198

“Precise Measurement of Methane in Air Using Diade-Pumped 3.4-ym Diferenee-

Frequency Generation in PPLN, KP Petrov, S, Waltman, EJ Digokencky,

M.Arbore, MM Fejer,FK Titel, and LW Hollerg, Appl Phys B G4

“Reactive Uptake of NO, on Pure Water and tonic Solutions," Y Rich,

RK Talukdar, and AR Ravishhankara, J Geophys Res 101, 21,023-21.031

“An AlkDiade-Laser Optical Frequency Reference Using Laser-Trapped Calcium

AW, Oates, Mi Stephens, and L Hollberg, Proc 1997 Int Frequency Control Symp

PARTIV OPTICAL SYNTHESIS AND EXTENDED WAVE LENGTH COVERAGE,

‘Precise Optical Frequency References and Difference Frequency Measurements

vith Diode Lasers." S Waltman, A Romanovsky, J Wells, RW Fox L, Hallberg,

MP Sassi, and H.G, Robinson, Prec SPIE Cont” on Frequency Stabilized Lasers and

Their Applications (ed ¥.C Chung) 1837, 388-361 (1992), TN215

“Proposed Sum-and-Ditference Method for Optical-Frequency Measurements in

the Near Infrared," DA Van Baak and L Hollberg, Opt Lett 19, 1588-1588 (1894)

TN221

“Estemnal-CavilyDifference-Frequency Source Near 3.2 um Based on Combining a

‘Tunable Diode Laser with a Diode-Pumped Né'YAG Laser In AgGaS2," U Simon,

S.Waltman, |, Loa, EK Titel, and L Helberg, J Opt Soe Am B42, 323-327

‘CONTENTS:

‘Frequency Stablization of Semiconductor Lasers by Resonant Optical Feedback,”

1B Dahmani,L, Hollerg, and R, Drulinger, Opt Lett 12, 876-878 (1987),

*Medulatable Narrow-Linewidth Semiconductor Lasers, L Hollberg and M, Ohtsu

‘Appl Phys Let, 52, 944-946 (1988)

“Using Diode Lasers for Atomic Physics," C.E: Wieman and L Holberg, Rev Sci

Instrum 62, 1-20 (1981)

“High-Sensitvty Spectroscopy with Diode Lasors,” R.W Fox, H.G Robinson,

AS Zibrov, N Mackie, J Marquardt, J Magyar, and LW Hollberg, Proc SPIE

‘Cont on Frequency Stabilized Lasers and Their Applications, 1837"

(ed ¥.C Chung) 360-365 (1992),

“The Diode Laser as a Spectroscopic Tool." RW Fox, C.S Weimer, L Hollera,

‘and G.C Turk, Spectrochim Acta Rev 15, 281-299 (1883)

“A CPW Phase-Locked Loop for Diode-Laser Stabilzation L D'Evelyn,

| Habra, and 28, Popov, Proc 104 IEEE MTT-S Microwave Symp,

San Diego, CA (1894)

“Amplitude Modulation on Frequency Locked Extended Cavity Diode Lasers,"

RW Fox, L D'Evelyn, H.G Robinsen, C.S Weimer, and L Holberg, Proc

‘SPIE Conference, 2378, 58-62 (1995)

“High-Accuracy Spectroscopy with Semiconductor Lasers: Application to Laser-

Frequency Stabilzation”L Hollberg, VL Velichansky, C.S Weimer, and

RW Fox in Chapter 3 of Frequency Gon of Semiconductor Lasers

(€d M Ohtsu, John Wiley and Sons) 73-03 (1996)

“Grating-Tuned Semiconductor MOPA Lasers for Precision Spectroscopy,”

JH Marquardt, F.C Cruz, M Stephens, C.W, Oates, LW Holberg, J C Bergquist,

DF Weleh, D Mohuys, and S, Sanders, Proc SPIE Conf 2834 34-40 (1996)

“Semiconductor Diode Lasers,” RW Fox, L Hollberg, and AS Zibroy, in

‘Atomic, Molecular, and Optical Physis: Elecromagnetc Radiation, (ed

FB Dunning and R.G, Hulet, Academic Press) 77-102 (1997) of 28C series

Experimental Methods inthe Physical Sciences

“CW Dye Lasers," L Holberg, Chapter 5 in Dye Laser Principles: With Applications

(6d FJ Duarte and Lioya W Hilman, Academic Press) 185-238 (1990),

TN4 INT

TN27 N33 N42 TN46 AINSI TN71

-TN 108

"Division by 3 of Optical Frequencies by Use of Ditference-Frequency Generation

in Noncsticaly Phase-Matched RDTIOAsO,,"O Pfister, M Martz, J S Wells,

1 Hoberg, and J.T, Murray, Opt Lett 21, 1987-1389 (1996),

‘Demonstration of a Phase-Lockable Microwave to Submilimater Wave Sweeper,”

$8 Malian LW olbor KA Melos, and ER Broun, Po, SPIE 242, 658

(18)

*A 1 GHz OplicalDelay-Line Oscilator Driven by @ Diode Laser,” J Kitching,

{ Maer, and Was, Proc: 1866 in EEE Fen Contol Symp 807614

(1989)

*Coninuoue.Wave Frequency Triglng and Quadruplng by Simultaneous Three-

‘Wave Mixings in Periodically Poled Crystals: Application toa Two-Step 1.19-

10.71-ym Frequency Bridge,” O Pfister, J.S Wells, L Hollberg,L Zink,

DA Van Baak, M.D Levenson, and W.R Bosenberg, Opt Lett 22, 1211-1213,

(1987),

PART V_ MULTIPHOTONINTERACTONS.AND OPTICAL COHERENCES

“Optical Probing of Cold Trapped Atoms," RW Fox, SL Giber, L Halberg,

JH Marquardt, and H.G Robinson, Opt Lett 18, 1456-1458 (1993)

“Experimental Demonstration of Laser Osciaton without Population Inversion

via Quantum Interference in Rb." AS Zibrov, M.D Lukin O-E, Nikonov, L Hollberg

MO, Senly VL_ Veichang an HG Robhsen,Phụs Ra Let 75, 1409802

(1995),

“Line Shapes of Cascade Two-Photon Transitions in a Cesium Magneto-Optic

‘Trap." LH Marquaret, H.G Robinson, and L Hallberg, J Opt, Soc Am 8

43, 1984-1398 (1996)

*Populaton- and Coherence Induced Gain and Self-Osclations in Akall Vapor,”

AS Zibrov, HG Robinson, VL Velichansky, V.V Vasiliev, L Hallberg,

E Arimondo, M.D Lukin, and M.O, Sculy, Proc Fith Symp on Frequency

Standards and Metrology (ed J.C Bergquist, World Scientific) 490-492 (1995),

“Experimental Demonstration of Enhanced Index of Refraction via Quantum

Coherence in Rb," AS, Zibrov, M.D Lukin, L Hallberg, DE Nikonov,

MO Scully, H.G Robinson, and V.L Velichansky, Phys Rev Lett

“78, 3938.3638 (1989)

"Specroscopy in Denso Ooherent Media: Line Narrowing and Interference Effects.”

MO Lukin, M Fleischhauer, AS Zibrov, H.G Robinson, V.L, Velchanssy,

L Holberg, and MO Scully, Phys Rev Lett 78, 2989-2962 (1887),

IN 229

„.TN292 -TN236

JIN 244

IN 247 TN280 -TN254 [TN 264 -TN287 N271

PART VI ADDITIONAL PUBLICATIONS (see preface for acitional information)

“Diode Lasers and Spectroscopic Applications," L Hollberg, R Fox, N Mackio, AS Zibroy, VL, Velichanshy, R Ellingsen, and H.G Robinson, Proc 10th In Conf on Laser Spectroscopy (TENICOLS) (eds M Ducioy, E Giacobino, and G Cary) 347-282 (1991),

‘Nonlinear Optics for Optical Frequency Synthesis and an Optical Divide by 3,” M Mrtz, 0 Piste, JH Marquardt, M Stephens, and J.S Wells, Proc Fifth Symp on Frequency Standards, 171-178 (1998) Diode Lasers and their Application to Spectroscopy,” L Holleran Applied Laser Spectroscopy (ed W Demizoder and M Inguscio, Plenum Press, New York) 117-125 (1890)

“Diode Lasers and Metrology,” R Fox, G Turk, N Mackie, T.Zitrova, M.P Sassi, J Marquardt

AS Zibroy, C Weimer, and L Hallberg, Solid State Lasers: New Developments and

‘Applications (ed M Ignuscio and R Wallenstein, Plenum Press, New York) 270-286 (1993)

“Diode Lasers for Frequency Standards and Precision Spectroscopy,” L Hallberg, J Aman, S Waliman, JH Marquardt, M Stephens, R.W Fox, DA Van Baak, C.S Weimer, H.G, Robinson,

AS Zibroy, N Mack, TP Zibrova, and L Penatil, Proc 1995 Int Frequency Control Symp 1185-190 (1995),

“Experimental Demonstration of Enhanced Index of Retraction via Quantum Coherence in Rb,”

AS Zibrov, MO Lukin L, Hollerg, O.E Nikonov, M.O Scully, HG Robinson, and VL Velchansky, Phys Rev Lett 76, 3995 (1996)

“Lasing without Inversion: The Road to New Short Wavelength Lasers.” M.D Lukin, M.O Scully,

GR Welch, E.S Fry LHollberg, G.G Padmabandu, H.G Robinson, and A.S, Zibrov, Laser Phys 6, 436-447 (1996),

*High-Conerence Diode Laser with Optical Feedback via a Microcavity with Whispering Gallery Modes," V-V Vasi'ev, VL Velichansk, ML Goredetski, VS, I'enenko, L Holberg, and A V Yarovitsk, Quant Electron 26, 657-658 (1896)

“Absorption Cross Sections and Self-Reaction Kinetics ofthe 10 Radical,” MH, Harwood, J.6 Burkholder, M, Hunter, RW Fox, and A.R Ravisharkara, J Phys Chem A 104, 353-363 (987)

Part |

Diode Laser Technology

_ +

ng d1 NnetEvamd hư DBIe b yereisie he cimrdghtsvmer

Frequency stabilization of semiconductor lasers by resonant

optical feedhack

B Dahman 1 Hollborg, and R, Druin

5 Senda sr, Clots ata!

"The high sensitivity fa well-nows phenomenon! of diode lasers to optical fodbac

‘hai uses alow level of opicl feedback to nero

‘semiconductor laser newldthe substantially ad seo

‘avtomatically to stabilize the ltrs oxiltion fre

‘quency With the appropiate opsieal geometry the

later optially self ocks uo ie resonance Fabry Pert reference emit The metod Flies ot e separate

having optical feedback our only at the eesonance st high-Q referee eaity- In this eabe the catty of

ferves tro lnetions Tt prosides the opti feed:

back, which narrows the laser's spectral width, and i

provides the center frequency stablztion tthe cat

“Arrowing nee for lasers with high spectral party

dna stimulated the development of s numberof sea

onductorlaser Trequency-stabilaston techniques

‘Methods hase been developed based onthe tech

iquesof optical feedback external eeviies noc

{on Tockng and eletvonieservo contra" Another

Inereating and related system for diode Ine rogues:

‘ystabilization ea hybria method tat uses electron

‘well as optical feedback tom afiberoptle eaity?

‘Because the special characterise of emaicondc-

tworlaserfroquoney noise, the only essteme that re

Able to achieve substantial Iinewidth reduction are thor that Incorporate some form of opie feedback

‘or uso ing servo bandwidths 230 ME vor fast electron servo'™™ (typically equi

“Ouriaterocngeynem contests withthe previous

atoms in that tho ase sees optical feedback only

‘when ts freuney matches the resonant frequency of

therelerencecavis We have lotedavaiety of opt

fal locking geometries; Fig 1 iagrasw particularly impleand effecive versio Asawa here when the

‘confocal veference cavity (ror teparation equal £0

‘mirror rai is operate of axis, shoold be vinwed

‘ba fourport device Teis important wo note thatthe {io porta on the input maar ade labeled Tan 1)

Irae different output chaactersice.-'The output bream of type is combination ofthe related potion

ofthe iopat bean with the tranenittes portion of the

‘ivy zesonan eld and henee have the desired chr Seleratie of a power maximum on resonance The seometey of Fig Lis one possible method of erranging {ohave he resonant optical fedbackoftype (maxi ‘um feedek on resonancs) while voiding the com Dlictions inherent in the directly reflected beats con {aimed im output L For a wide range of feodback

‘conditions this system tends to slfock stably, thus forcing se laerreqne to match that af the cavity

‘Our experiments have been carved out using com sera, tngle-mode, 850snm, GaAlA® livers with

‘out any special preparation of these devices ‘The foc running, unpertsbed lace izewidth were mea: sured to be approsimately 20-30 ME A variety of feference cavities wes used for tne optical ecking #5 Tem These had free spectral ranges vying om 250,

‘MHL to 15 GH and resonance width aging from 4 to7SMHz Avan addtional laser diagnostic wemen-

(©1867, Optio Society of Amarin

ig 2, The lover trace dplns the pone cemented

fen The uper teace, taken inulancusty, shows the

Ñgn«eeeetne seetemeelmt lược cam oma

tro tha SỐ mm xem reoamme Theft pation

He nó việc torcetareamlsndun lát sk fh

{hele resonance ne logor sean wi the tse

ree The indinel locking sense ~500 Mle core

{pond the tmamere ange tht toast nal ‘anit te opel oe

tor the resonance fluorescence from an aomie-esium,

sapar eel

‘With type I feck tthe laser frequency is far

from uatching reference cavity resonance thete et

optical feedback and te laser frequency ‘Sithchangesin the njection current However asthe sans usual

Taser freqoncyepproaches «envy resonance, seo

‘pant feedback occurs and the laser frequency leks ‘he castysetomance, evn i the Ise eaten coat

tue lo wean "The acl Irequency range over whieh

the diode laser locks is function of the feedback

power latlend thephase ofthe eedback ight elatve

đo hạt [the unpertirbed laser The opSeal looking

‘ofthe laser frequency to the rference cavity feeoe hance is observed directly with photodiode, which

‘monitor the power tranemifuedl Lhrogh the cặc hy

‘function ofthe hser cusent "hs signal ix dit

played a the lower trace in Fig 9, Here We ste a

famssval Fabry-Perot transmiion function, which

ban a fat top and a width approximately 10 ti

larger than the actual cavity neconanee Wl of

Mil ‘Ths shape ia manifestation ofthe fact that

‘he Ise feequeny snot scanning with th laser ex

ont uti lacking tothe frequency of peak tana

‘Som ofthe envity resonance The regency locking i

further demonstrated in the upper seace of Fig 2,

‘which shows a sieltancous record ofthe orescenee

From aces esl tthe laser scans over he 852

‘esl resonance Hine This trace shows that when the lve frequency far from the pea a the cavity

esonane (ehown isthe lower rel sconemoothly

hạ the cing erovance tthe nse current va

fel ‘The self locking which siailizes te laser fe

‘teene, is evidenced s the abrupt fattening in the

Scan of the orescence signal aswell asthe caity

{asenion function At the end uf the GOO-MEE

Jacking ange the Inset sbroply drone ot of lok ad

‘continien scan over the cesium resonance,

‘ofthe external feedback power, coupled int the ler Thode, to the power efleevd internally by the output feeot’ Locking ranges of afew hundred megahertz

‘were observed with feedback power ratios typically The range of 10-4 to 0" wid w large uncereainty the coupling eficiney of the feedback power into the Internode Tn order to determine unambiguoualy the spectral characteristics of the optically locked semiconductor lasers, we measured the eat note between two lse Independents locked to separate reference cavities, Direct observation of the beat-note apecten voice

‘any ofthe uncertainties and errors that plague ea urements of laser froquency stability and neath {iy delayed self heterodyne and eletonle resus

‘ror sil techniques Figure hows the heat no đâeketed with a fst photodiode and displayed on « Spectrum analyzer "The upper trace shows the beat tote sehen ane of the lasor is fre running withost Iodback while sheotherlasris optically eked ‘The sharply peaked trace ls ebtained when beth of the Timers are optiealytocked to their dependent refer

fe cavities end indicates the dramatie linewidth

‘Agetion tha i istanty achieved Inthe locked ease, the width of the displayed beat note i limited not by the acer linet bot rather by the f spectra an Ione eslution bandwidth of 00 kita” Higherte sition measurerenls hợy thất the ectualspeetmi

|i of the beat note can bo lees han 20 km 0),

‘Tae narowing of the semiconductor Hneedi by œ factor ofc 1000 (rom 29 ME to 20 Kea) i be

‘ined by purely optical means without any electronic contol

‘Sarpy peated ace hte beat ate when uth of th instar apa st rte soporte Fay ere et

‘Sea eaiten Inthe hed cue the pak wd ied

TN2

November 867

‘lode Later Boat oe 1 Mee

Vig Diode le bat note iplne wit ihe esi

‘on he shows ety nat wih ae menue un FF

Spectr snag The appenimaev 20H vành

‘ive cathe oro marietzon th otal pak which ae

‘separated by “10 JB and 13 KS), the spectei are?

‘herepeatablty athe neste

One advantage ofthe optealy sel ocked Lge ys

tes is Unt it shone some reduction n sensitivity to

ether sources of optical feedback In addition, thatthe excess Intensity nolse (=30 dD above the we find

fxpected phatodstetin shot nate) Unit ve meagere

fn the light rom the semiconductor laser is reduce

fy roughly 10 dl whan the laser i optiolly locked to theca

"For many applications iis important tobe able to

scan the laar requancy ab Well a to have a sable

long-term frequency lock Continuous, nareow

"nowt scare of the laser freuen canbe made by

symehronizing tho seep of the laser current with hat

fl the rlorene evity length (PZT-C, Bg 1) and the

Teedback phase (PZT-¢) With thie synehronization

‘We heve made continuous scans of more tan these were Tinited only hy the eange af our present 4 GH

Dag We note that itis necessary fo contol the

laser corront ‘only secuately enough that he free

‘ning lace frequency within the = S00 MEe opt

fakelf locking range To avo the inevitable def

find toenauze long-term locking sabi, tis usafl to

servo conta the appropriate feedback phase and laser

Crrent relative tothe relerence caste Lowexpend

‘eetronie feedback cnet are sufficient tn aco

plist

"The actual phyvies that determines the spectral

haractavsties of sumicondactor lasers is tape of

fctve reeareh end in reviewed 1p Ref 13 Initial

‘theoretical analy of the self locking process based

fo optical Teedack theory!" lees reason

‘agreement with experimental results a leat in terms

Sf linewicth reduction, locking range, and the pha ‘dependence

of the cavity ooking

‘The optical self-locking system described here has

several advantages relative to conventional ooking techniques tiv eatvely simple method thst pro=

ies ara improvement inthe news andl drcet

‘control ofthe semiconductor laser frequency When the eytem locked, the lasers linewidth le reduced

‘anaticaly rom 20 Mile to approximately 20 kn,

‘nd the lasers oselation frequeneyistablzed ‘avy esonance frequency Even narrower spectral tothe

‘wide could be expected with better-qulity refer-

‘ec estes "Long-term stabil of the reference anhy raonance can behite high!” We oberve that the laser's intonsity noise seduced, a sits consi

ly woother sources ofoptelfeediack-"Thesytera alk atractive ‘tion ofommmecil laser diodes or any extetaely because t doesnot require any modi fet Slevtronlcaervo ystems With the incroaing interest

In semiconductor lasers with high spectral pity and Precision optical easurements in general, his opti False locking method has the potential fe sumer:

‘ou applications Permanent address, Laboratoire Primalre dy

‘Tempaet BOLE Pats, France dee Frequances, 61 avenuede!Obsarvatcire,

in Digest of Tupieal Meeting on Semicondactor Lasers

Modulatable narrow-linewidth semiconductor lasers

\ Hotbers ana, Otsu”

Snort Baro fiona Bolder Clr 003

(Recrved 28 March 198; accepts for pubtion$ July 1988)

Wetind th using the technique of opal fosback locking to narrow semiconductor

linewidths, doesnot sacrifice the ality to modulate the se’ requney via the inet

caren The fequeney of inter stati to a separate Fabry-Perot eres cavity ing

‘resonant optical fedhack and canbe malted ficiently a Fequenies related by ration

Fraction tothe feespoceal range ofthe rfetene cavity, This syst can ronidean aay of

rnarow-tinewith fequensy sabe ase ines and shows prose for appieaton in

Frequency dvson melipiened coherent comminictons a wel hư frequency contrat

‘Opn eeback locking of semiconductor lasers pro-

ides powerfl mana forstabiiing the equecy aod nar

7owing the linewidth of die lasers”? This opis ech-

ige can reduce abr Hines by more ta a ete of

1000, tus achieving emits of ew blokes We om

sidererethe intersting and sel moda sharatens-

tis of these opicaly stabilized "onicondactor lasers

(OSS Digest modulation of theijeton cuenta thee

lasers can proideahigh FM moddaion mi ghi the

sry narrow neath and frequency stabilization prods

bythe opel esdeck Tock mains

The highspeed frequen) at ampitade modalton

apatites ofseriondtor ser re importa atten

these ees slave toother open sarees Unfortunate

ly the FM eapbliies ee sully sacefoed when the ler

newts are reduced by opal mears* With wos =

quency stabitzaon schemes there fn wade of beter the

Ande hse newt and its FM sedation capitis

Unslly# one-one corespondence ent between these

‘quanti that the ser nest i adused ya tor

P710 le EM senstvty oijecion cute (Wpically ~3

GHlz/mA) sso reduced by oughly thinsame eto of 10

In the case ofthe OSSL the modulation characters a=

die altered bythe optical ooking process bat we ek

{that the modlaion seastity is set naecsanly rede

‘when thefiewid saat, Inachy wend hat the mode

Inton characteristics ofthe OSS have a prditaie reso

ran egueaey depeence

‘Te concept bshind the otal feedback locking tec

sigue sto eb wesh resonant feedback from e nh Ø

(restive the Gol he dod serenity) optical resonstor

Figre lisa diagram of system which ives nance op

cl feedback when the ase eaten matches the cu

tewnanee amlles0vdy seroeedback of rexonance Here

4 eamepiter picks fx small amount of he Isr output

{4% and coupes io axisinto a contol opie neo:

aor Tis geometrical arrangement ensues Ut he ser

‘et pine opal feedback prvnely when the er fe

gency matches the eat resonance quency The optical

{Gok ustllyoperatsin thew fect hit nd spell

eauiresanopieal fedhork powerofbou 10- “ofthe ser

output power? At resonance the spectrally cleans Iter

ld which bas bul up in the rlerence cavity leaks back

‘rough the cavity spt mirror and retmas lo the le whereitineenses the lser gun at that frequen Thi fe {uenc-seletve gun enhancement foros the sero lack heavily resonance fequene The resis that he sem

‘conductor ase’ requency 8 stabilized t he cavity Fso- ance and 39 MH linewidth reduced of thay 10

Li Related wock las also ben poe ersemicondsctor Inter Frequency contol using optical edback from opi eaveguides' and Sher enti”

Were ned a variety f optical pomtries nd eer enceeaities al ranges (FSR) of he cefeence for these opial looking stems Thefiee sp eves were between 73 (GH and 250 Mie with eavaty resonance widths varying from 75 Miz 10 20 kt The commer ses were singe rode AIGAAS lasers operating near B80 um and were ao

‘odie any way Foe sppicationsreqing higher spec: teal pur an fo esha! pe noe shih feqeens, ittseal osend all of the ser power nto ad Hường he Iighetiiency reference avy The cavity then acts 363

tundpas ter and removes the exces laser phase noise at

‘ery high frequencies Thischeme uses the reference lý

sa speciral and spatial tera wells the requcney de

tinal forthe optical feedback lock wing the weak ref:

Modulation of the injection current of nonstate

semiconductor lasers esuls in both ampitude and frequen:

‘oy modulation ofthe ase output At lesen tein low

‘ulation index the temporal characterise of the set

lec dd căn be epeseta by

BU) = ALL + messy) sot + Boing + 89)

œ Hee Ais the dd snpltud, g/(2) te hư camier

fequeney, o/(2z) i the medulation frequency, abd m

and mptcxen the aanlitude soi eeguenty ulation

(dee, respectively The reuling fReowehcr-donain

*pecm san bệ deeded hy le sual um of AM pus FM

‘ebands (with Bese function smplitdes except that he

{elite phase ổ etacen AM and FM i frequency depen

dent When ode ater operating wellbore chresbol a

Small modulation of theinjecion trent res ns mod

ion ofthe laser eld at x prosominantly FM withthe

‘atioof ftom typically he range of 10t0 20 However,

‘when the medulition index large (>) the situation

«ante considerably more compiated

‘When the OSS is modulated at fw frequencies, typ

cally og <200 MHz, the trequency modelation sup

pres y the opt ack restive to hat ofan unsaid

use On the other hand, there are special modulation fre

quencies that strongly afc te equeney modulation hae

‘cteistis of the OSSL With certain ausulation conditions

Some ol of the modulation idebend an esate with

the elerence cavity (with o without he eatin, in which

‘methey return tothe ser and reiforce the optical ok I

prticalr optical idebands at frequencies that correspond

{o the FSR (or its harmonics) ofthe reference cavity are

Slmultancously resonant with he cavity and are fed bac

the ser wth the care In this Way spose wo modu

Inte the laser current wih a high odelation inden and

‘geseate man sideband without darting te frequency

Sablon and linewidth narrowing prove by the opt

‘a fb lock,

Figure 2 shows the resonances inthe optic! lsking

proces that on aterve function ofthe applied no

lation fegeoney The tallest, vey spac sharp en

ances inthis figure occur whe the mdulaton at Kenoen

‘es integral elated wo the eavlty SI of 245 MM Good

‘optical locking i observed a the modulation frequencies

‘corresponding o these resonances, Alb, the power tans

ined through the cavity is maximize teen the laser

‘ati and he đáchanh match cavity resonances

{Allo the envity transmission resonances shown in Fig

2 correspond fo meduldontequence tha are tated 0

UWereteene cavity FSR by eaten numbers, that i khen

the modulation reereyls

‘Thesqulleresonneesshownin Fig 2occor when the ratio

(a/b) 6 not an integer This ational rltonsip between

‘of (2) every bi sideband can resonate with every ah

‘vty mode For example, sodulaion a 367 M7 core: Spendstou/b = 3/2 and measthat when the carci ee

‘ant witha cory mde every oer sien wil sna Taneously resonant with etry thd cavity moe This Situation gives sable oc ockingwithroushiyhalof the alle power reaonant withthe cavity We hare observed these resonant enhancements he opal ck for many modulation frequency to FSR eats, incling those with

= -9andð— Ì 5 Iapdmeple some optical locking os urs foray modulation equeny hat seats to theca ity FI by a rational nurier (a/b) but i general 35 the

‘enoninatorgtsaeer, ess ad es ofthe sable op

‘al powers esonat sth the evity modes and ence the

“plelleckk leagfeciee Thewrengthsfapariet re ance depends nh nunbe sie f the ded tat areFesonant wilh cat tds and has depen tangy on The modelation inden andthe vale of

“The frequency domain poner spect of an optically locke ase thats nolatd at one ofthe resonances [or stent with Ea, C1] cơn of am aray of requency stab lac, narow fnew aser ines scars by the sodle tion frequency Figure 3 «hon dưng pc of 3 rvodulted OSSL taken wath an optical spectum analyzer (See Fig 1) The opie! spectrum analyer ta wed 0

‘splay the modulation sideband not capable of nes Ing the wey natow laser nei bean of he imo resolving power whan alge FSR (7.5GHz) rogue In

‘Seder to meanare the laser linewidth we tae Bterodyne tnethods to deter the teal note Between two OSSL's! We

fa that he locked ler int ales than IDK an

tôạlthebnexidtisunchangel khen the hượ mtolared

tftequecie!Ihatcorepond lo e lociiegtronsnccxtlai

teshown in Fig 2 Theis tobe compared wit inewidiis

‘hat are meaared tobe 20 ME when the lero fosked

orisstvonly modulated at afeeqdety thas nota oil

looking tenance frequency When madlated at sch non-

‘ooking frequencies the OSSL' newt degrade ogre

"x ys atl 8.81, Serb 868

sively rom 20 KH increased, 'A poo optical lock ocuts when the ner modulated sta resonance requency content with Eq (2) However, (hese esonances early narow in modulation Frequency and depend directly onthe Qof the cavity the maxon index ae the opi feck evel For example, with looking ely Q™ 10" (cucespding toa evity Sass of {and a FSR of 285 MH) and an opal Toeback power ratio of abou 10°, the modulation fegueney Fang for

ad opis locking is approximately 6 MỸ wide (ce {ered atthe modlton resanance frequency at 245 ME,

Se Fig 2) Ths range is for a modulation index 8 ad fnereaic, 8 we igh pc with soaller modulation i= des, Thin resonant character ofthe laser's FM modlaton response limits the modulation formas tat ean be em ployed withthe OSSL- Using the etigue of opis feedback locking wed

‘hacits posible to imnlensoamly havea narronciowth Semiconductor laser with ahighsenstity fequeey mos uation expat Frequency modulation indacd va the {and merow tnwsath) when the ai sĩ the moền ion Fequenc f0 cavity FSR Js a rational numer One ofthe

‘promising applications sto we the mnlated SSL top ‘ideanarty of requcncystabiized lca ola fe c8wencv-dnio.mulitcsef shGtaf canauricmion ực ems, There is also the poteaal for mesaae ofa iaotpion and dispersion sith high senavy tang the 'cshniguss of opi eterodyne spectresony as wel a8 pplctlons in peesion laser metturemens ad freuen)

ee

We woul ike to thank JL Hall R Draingr, Dahman, eed A Clon fr consiructivedecssions, ad JL-L- Halland the Joint nati for Labortoey Astrophys Jes foe making tis collaboration possible

020 Mitr asthe modaaton exis

TN-Using diode lasers for atomic physics

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‘We preset a roview ofthe we of de ters in atomic physics with n extensive ist of

references, Weedisus the evan characterises of dade lasers an explln bow to purse

and ne them, We a review the vars techniques that have Be edt onto ad

sorrow te spectral outpts of de ler Fal we present 2 amber of examples

‘lusting the use of hoặc aersÍn atte physics experiment,

LINTBODUCTION

[Much of eurent iomie physics research involes the

Intracion of atoms a Tht in some way Lar sources

hat car be tune to pacticult atomic rane an

staan tol th ose atomic physics aborateries Teh

tina this source as teen a tunable de laser Hove,

emiconductor dade lasers have been tex ipoving

Felis, power, and wavelength coverage, while sen

đđeeseng im eon snow pen to hse a diode set

frstem hat il pres more han 10 of table ht

vith Bani of 109 KH fee act oft than SIO,

Furthermore, the dade ater and power spy wl in

167 bo, ghi vn Me Power ch Matera

der the right coritions, wl be win afew Mise of te

Asied wavelength as soon ats tutta on After i

fue is thatthe apd very lable compared ta men

fer ler see sẽ tát lately sip f9 make

Senstive absorption or Muorescenve measurements, These

Tenures ke diode lasers increasingly attractive suerne

ties for avanety a see

In ths review we prevent someting of a ser guide

smd a atoms pysions who might want fo ser asi

God lsrsinthele wor Ia thisspat we presen sheadvan

tages of dod sess wll ss her negative ares thet

sroseveral rises) andthe est wapstodal with her

‘Wie begin in See IT by discussing relevant ase ase shar

ters Section I addres some ofthe mat ro!

‘sues nplved actual sting up ad wing ce ers

im stom physics enperiment, sch a purchasing he co

Fost Inserting i to fhe desired eqeey a how 10

tld destroying it Section IV dcsaes optical and ee

{too feathck to contol he ae opt requeney Ta the

Ds one ofthe main drabacks to using diode lasers a

‘omic pis was the dificult i obtaining eazeowband,

esl Unable output However the devlopments covers

{Sec IV haveimproned th taton conser, Seton

Vien discusesa seated et of appicatons of de ses

Inatonic phi, focusing primary on work tat hs been

ttde posible by these new wavelength contrlecbiqes

Tenth article ia reasonable length there aren

sarily many things we do aot discus For examp, We do

rot cover progress mae on proc pil diode les that work in arvlos wap, besuse these developmental tnsrsarenot avaiable tormat atone physics, Weresret fursves 1 iasers that are standard sommercal devin

‘Another stable omision she extensive work io nokolar fectrncny that as been done using ea salt diode tes

‘nthe mean friar pons ofthe petro

‘Campa! completed an exteuiv review on he use of ioe ers in atom pss in 98S, That Fev covered sich ofthe bane pyss nd craters of ode se

Sd the varags vss tat hal Boon mage of em AU thal fine most devies were simple fce-runinglsers witht Tendback and they had Been used pencpall fr opt) pumping and low relation spectroscopy a the present, evi athoug there wil necenarty Be some ovrap of that discussion, we will nphaszethe rece! developaens incling "sabia laser (ones wilh Ieieek lọc Hệ

‘ens consol, andre pes ofepplietons Theresa

tm excelent review ented “Caberenc in Senicondstor {ses by Oho and Tako? tha ducts aplintionsin a

4 BASIC LASER CHARACTERISTICS references and wil not be repeated here, However, we do

‘sho single outa fw Fetus hat ate celevant to much of theater discussion The construction of type seo

‘eto diode Ine show in Fg The devices ace ex twemel small nd yr ae copa of reasonable ew tpt powers wath high clastic To optical eficeny The laser Tan generate by sega current (the ie cur rent” through the active rep the dhe beeen the tnd pe cling layers: This produces electrons and tole vhichintumfeeambinen4emliphot Theee< mission wavelength determined by the fd pap othe Semiconductor mitral and vọy Mosdend eave 10 omic apsitions, Thespatal mz of thesis defined by Sow chal nthe seive pion al cones the ight

“Ths cominement of the ansverse lar mee ached citer trough the spt arton of ction arrest So

Sy ain guided) or by spatial varistions in he index of

oom

elastin due to changesia the materials sein the ser’

fontrution (index gai)

'A wide variety of laser signs have been used Mos of

the atomic physics done with ode lasers has bee carted

fut using iden guided GaAIAS lasers nthe near infrared

‘tion ofthe spectrun Uns otherwise noted, this pe

tl be asumed i the subsequent dncsson These lasers

‘apicaly produce single-mode (spatial and lonpdina)

tpt owes 5-15 mW mth jut th cleaved ace ofthe

‘emiconductor serving asthe lasers miror Output powers

‘p02 50 mW are commercially salable rom what ae

‘sei he same devices wit the adton os igh re

‘ating these special design atx desired wavelengths & Formidable prem,

“Tae output power ofaryplcl semiconductor diode set sya function of the section current apd temperate

‘Shown in Fig 2 Tis shows the abrupt one fase action

‘tthe threstold caren and the nereare the threshold wih temperature, Aiterstvely, for ve jechon comel, the ater’ output inteases rail s the temperate lomered Figoe3shows the ower and wavelength characterstie

‘fen diode aes that rently availabe rom commercial Sources, hee are divided nto ve iin band ax den 89 commercial spplicaions The two bands the rare at

1300 and 1500 nm, have been developed pis fo er opti jtems and ae ase on quartenay InGaAsP semi

‘aductors The esi the 750-890 nm reponse based

fn AIGaAs and have applistionsin conser and coor

‘Snlletronin sr wil ar sme fer opti pains The Ieltvely new rile dode ers near 870 mare based 08 {nGaAIP semiconductors and ave many projeed apres: tons in commercial opteecteonic systems Tn applying these rows ner to spectroscopy we Bed that te spe teal echaraceristis vary considerably These in the 750-870

fm eon have the best overall haactnstics,

‘A Beam spatial characteristics Became the light is emit rom a sel rectangular resion (onthe oder of jm by 0.3 the ouput of &

INS

ine inser has 2 lage sivergence (see Fig, 1) typical

‘utp beams wil aves dvergence angle (Fall ih 305

Intensi) of inthe czeeton perpendicular to the je

thn, ad 10" 9 tbe paral reco, Normally the beam =

‘lated ving lets with small euber, the cei

perting in a single anserse mode, the climate beam

‘ilbeeliptial, at canbe madeneyh cay mmet

Tắc using anamorphic tteme Tn hien tothe ifernt

Siergence angles the osput bean of most die loses i

‘sigma, Ts asigmanse ca aso be compensated when

essary.” A pis dade ser wavelontcalliated in

thistasionwllten havea ignifcant aountof erature

“Thies primey a function of he quality of the Se il

sting levand te amount tapertaresthe beam However,

with eave inexpensive lentes and spatial eng one

“3g walronts with good Gauaan profiles Thiccan

te done wth eatvey ile ssn power (10%), ou some

teste opal feedback rom the Stern clement canbe

a poblen, Iroc force 0 work with se tha eat

Ting ght ia a amber of teansverse modes + bạ sư

lure Ream is unanoiable le ne saeco nail

amplitude spectrum

For most appiaio, the anpltude and spectral cha

actertin of height are more ports shan the sts

fharactenstics When compared f0 other tooale ase

Sources, the amplitude nose on die ser 5 velavely

Sal, but cạn vay conaderbly depending on the at)

[sterandis operating conditions Figure ows the amp

‘ene spectrum a ypc single mode diode et ke

SH 3 fast etadio an an petra analyze The

‘aturalcalefor the measurement ofeser ample oes

‘the quantita sha-nlse eel ha siete ote

Figure for hls deed power The general sect ofthe

ample nose shows peaking atthe lowest Fourier fe-

‘quencies /2500 kia) Antennae frequencies (SOD

‘ove te relation oscilton to figher Freeney peel Tasersyters ave bee ull to bring te arpitde nose of diode srs down tạ ad even eo.” the shots level

tt this perfrmance cannot be expected foam standard

‘Most atone hss experimen are done with detec= tủanbamdeidlxeearela beloyor rlemnediteffeuet- range In thin ange he apt noise fora good qual

fy the ner can bet low reaivetothat of dye sr,

ah 1010208 sore the quantursiited shot nose Teel This enslats ito power etations fr a pea Aloe se of one pati 10" fora WOAH dtetion lan

‘veh The station ca be ouch worse with some Isr Particularly when the laser rons melumode ia only 8 fe odes he esling oie scaled rode competion soe tera factors suchas Mucuaonsin the mectioncuren the temperature snd the opi ebook can intese the smpinade nose substantially Each ofthese ance the

tt the ade inser and hence it ep power The supper of le ses ocasonally provide some

‘information about he aes iensity nose, Bettis info tation fully spied oa way tht fs most eel for pplication fo conser eleronte For example, the Spesitoations may give signal-to-noise eto (5) of 80 {AB Thistsameauteofthe ners ample noe kena 1Wkdte tanith center at KH This inormation sell but isu Tor many seentie ppt The pask ofthe noise atthe elation oscil fre {nd sxe he a problem fr some apctions The acon of Taser poner tat i contained inthe elsationosiiation

ps ares considerably frm ane type ser fo aethet {nd even varies fora piven Ite depending on ts operatiog enstions Far example, he power nthe reason sie bands can vary by as much as factor of 100 with varacons

tn optical each, Went good singe mode AIGaAs sơn operating nea 80m wil have easton sidebands

‘hat ate down fom the care By 4 fcr of = 10 To

“ota, ome ofthe visible srs (67 om) we have tested

‘Sho relsatin sideband that aze roughly 10% of the car tet Therelsation elation siebands ae no aay det fimental Avice in Se V A they can provide sti

‘pscal pamping

FM spectrum

“Theraretwonatral sales tothe osilaton spectrum

of ide laser Theft scale set bythe spacing of the

‘ity modes of he laser which son the onder of 160 GH (Cl035 nr) The serond sth new ofa single cavity Ine At the prevent time, ts ite routine oa "Sor tim si ke he nse nrare qin (73040 880 AIGAAS sere) although te sible (479m INGOAIP I

NS

Ser) and infared ses (1500 an S00 n, IaGaAsP le

Ser) ordinarily wil have thee power dstbuted in many

modes The datibuted festack {DFB) lets inthe he

are will on ina singe mode but ave ined tuning

ange, We might tention ew caveats sbout nomial

Single-mode ses Fut hey are ot absolute single me

in hat there ae small bot fendly observable amounts of

ower ia numerou ther modes tht cat occasionally Be a

Problem Sesond, se thie hs been ol asa ingle made

tt BI ofen not eu it singe mode forall injection

carens The aes wl ays he multimode fr very low

Injection current, bu even at mch higher cưng thế

se ofen ange of sree snd ferperture wher theses

‘contin to aperat in several made

Forth ematade of thi seton we will consider only

the linewidth of a single mode For some applatons, i

‘avis ars sor thal the Schawlow- Towne newt Sigican (ypicaly afew MHz)” The inewidts of com

‘monsinalemode die ers are age than he Schawow Townes value teense of factuations inthe carer the temperature and inthe complex suscep of he ser (iypcally lewis vary fom about 10 to 500 MER) Linewaths 201030 MH are pia fr low power index sues acers.Thespectrum of he reqaeney ne sar {ad coupled) 10 the spctram ofthe ample oie At xaipe of fequeny noise spectrum ofa diode ase is shown in Fig 5 Unfoctnarely, we ee that the fequeney iis arge an extends ey high equenie The MgA Frequency FM nove is problem fortwo reasons (1) is sical make electrons tat ae fs enoigh fo correct the Fequeny utuations and (2) even when he newt

is narrowed by some optieal or eactrone mens there sully esi! hgh frruercy phe note that conte rates some types of easement

.Tuning characteristics

A diode ase’ wavelengths determined pimaniy by

‘hen apo the semiconductor materi and then the ution enperatre ae current deny" Thebnd gap that determines he general rangeot thease’ wavelengths tnforstely not under the eotsol of he laser ust The

‘ange of wavelengths that are cexlyavalabe shown in Fig 5, but gen commercial laser wil only (and com

‘ltly) tune over a wavelength interval of about 20 am

“The the ser mst buy alae thats doped to operate wh inthe cong range of he wavelength of ners

“The lst Feequency tunes wi temperture because

‘othe optical pathlength f thecavity andthe wavelength

<ependenar Tươi these temperature dependencies are quite eee ofthe gun carve dependon temperate Ulor- Foretampie inthe AIGAAs device the opel length the

‘avy changes about +006 am/K wile the gain cure Shits about +025 nav Ths results ipa temperataze Tuning curve which iam ideal device is a tac wih slopingstes (ae Fig 6) The opeot each slept he toning ofthat cavity mode, wile he jmp between steps otespnds to hopping trom one lonptuainal mode the heat (20.5 a) due tothe shit ofthe gum curve The {pect gape” encousered inthe fer turing a jumps

‘Rom one Sep othe nxt are the biggest drawback o tng ioe lsers in atomic phys We wl discuss below some fempincal techniques tht have beea developed for dealing

‘eth ths behave alae ase, as well as techniques Torwsingenteral opti! edbacko reduce or limite he problem I prctieathough the overall uring fellows the Stazease patter described, oe 2 ase may frp several avy modes at once, apd hen perhaps jump back at 3

Sg higheremperatireasshown in Fig 6 Thechoie of

‘ich mae the laser wil hop fo neti often extemely Sense to opal feedback "oom enperare” commercial ide atersare typ

TRÍ

cally rated to operate im a range of = 30 K shout room

Temperature Thin provides tuningrangeofabout?! am for

[AiGaAs Ines The cevated temperature generally cause

‘otcenble degradation inthe ler’ istime, For xample

‘he data shets inate hat ype etme of about 1

isreduced bya factor of3 when the temperate increase

ty 10K Orker performance charactecntics may alo be de

rade at bgher temperatures The teperature ep

‘dence afte loser characteristics vrs uta fr di

ferent models and pes of lise: however, detled

‘nforadon i often provide bythe manelctrer Lasers

can actly becoolad far more than SOK (experience sows

{Gar atleast some ofthe comers ater an be opera

Sonn o fguis He terperatues) the lower temperazares

bring some adaonal complications suchas the nee topo

‘eo te ase en wae condensaionand mechanical te

dle to are temperatre changes For very ge trier

tore chengesone mast ue the Varah qtion to prec

‘he wavelength ater than the near approximation shen

shove

Ti addition to depending onthe temperate the er

savlegth slo depends on te injection caren, Changes

{the nection erent act Roth the dade temperate

and changethecarter dens whieh als changes thesndex

5í rữnchon, ad thec urn act the wavelength Foe

Sine seas longer đun abou ts the cere ning <a

simply be thou of ss way 0 change the temperate

apis because the carter density cotebtion to hei

eof elastin tuning i lativey small The cueent a

Fests the uncon temperature becuse of ful eauing ad

the ren tuning curve for wavelength vers carrer

looks mach the some ae that vests emperanir Only for

limes shores than ~I us is the temperature rise small

rough ha the cari dest eect sna overlie."

Theqwetoy te =~ 1GHz/ mA lor aquenceseow abo |

‘Mite then tops to = 300 MHT2/ma for fequentes

from 1193000 MB tes againto = ~1GH/mA she

frequen ofthe relation aeilation iypiclly 3 GH2}

tnd then drops of rapily above ths Frequency The crs:

er ehavior beeen the dierent regions af FM response

un cause cosierabe complication it ghspeed modula

‘on and equeney control ystems or dod lasers

‘One ofthe imprint advantages of ode ser er

cer optical wares that ther amplitude an rene)

{ab be ulated ery say and apy by changing the

Thiet curr Unfortunatly, when he ection curea

‘eradelte, one obi both AM and FM, and these are

‘ot independent The simplex exe pte ofthe mae

ton response of diode lasers tt the AN and FM are bok

present hat wah dierent sess Also modulation

in be competed bythe ft that the elaine phase

Ngueen the AMand the PM càng ta fồncuene mod

lation egbensy Toa good approximation, the AM and he

FMareliea wit the injection urea’ bute PM mol

tin nde ean be more than len tines the AM es TS

Ica that the amit change ean be ignore im many

ome physics applications Thos tbe ase an be scanned

ver spectroscope featces nor jiapedtackand ortho

specie equencies jst by applying the appropriate tedk- [apon othe injection earentAppteatons ovaroan me lon eapabiiies re diseased in Sc VB

Visible lasers

“The new visible dade ler! which operate nea 670 omareerctingtor spectroscopic and otherappestions Be auseof enews thee devices weave aon ki

fs experince wah hem, The primary problem wih hee Taner is thee broad apectal width Most ae gine father than inde-gide, nich yly sean that they

‘nthave very poor peta charactrstce We in ht the

hi len usalý sn mehirmede xà onNel regions of Single mode operation In addition even onthe repos of Sinslemode operation (and with very Tite data) the

“inch of tnstablzed devs ave 30 Mie or farce

‘They alo ave a onsverse ode structure hat save large and asymmaine divergence (7 and 0) Witt _Smperation ths proces aor beam witha linea shape rather than found spot The stractare soul be corse, Duct dice oon opis Sesigned pei for these lasers Frlly the outpt poe of vibe dod ser has avery step dependence on temperate and infection current nbicean ead one eas toa ah nen nosed

—

IL PRACTICAL GUIDE To USING DIODE LASERS Having discussed dhe hai behator of ide ater, we sil ow presen rome a he practi ses vole nse ting up and sing ee ses or atomic pss Athough

‘vedo nor discus srs wth edbesk in thi section wat

‘he scuson spies taal cae a wel,

A Purchasing diode tasers Prohably the singe bigest frsttion in using dade lasers in tome physi experiment bas nothing todo wih scientfeorteshicalhauea, Instead tthe cay i purchasing dade that have been dope to emi atthe de sired maselength (or lose enough to reach with emer ture rning) Because of ths ueorunate fc, i eens

‘orhatiletoprovidesome dsusson to preparethe poten

al wer for some ofthe problems that mete he han

‘Thee arke beau the stom pie market ean ery rasigifcant fraction ofthe tral soe leer mare, an

Ae laser production is overwhstmngly Japan, Thee for, ules you ae fortune enough to have some dee conlat you wl probably be deting witha deirbaoe ho

is unaiae wit your speci equrements and rahe tant rm te spe

With this wackpround we wil now explain what is ia solve in geting the laser you desi fn he mantis Process there wl arma be trget wavclngih shih he ompany sting to esos, ba there wil be some seal

in what actualy pcdued an they wil advertise thst therange over which ers are availble Ths the St ae isto get the company tserce the lasts and cet te de Siro wavelength, Some manufactures of lasers wld ths Andsome wll tot However, tse common fore oad

‘fsbator fora company that Soe slot tay

INA

Impossiblet ge wavelength seleted ler, orsiply ease

‘handle them Sometimes xtended phone stesons with

‘the ntionaleadguartets ado he đarBator he

this problem, Once you have found a dtibtor wing to

onde seletd ines for yu there ae il some adios

problems First ifyou want a song te welt oF

the tn ofthe dstsbution af wavelengths produce you

‘ould have a substantial delay Several years ago there were

‘many seecdotes bout 15-2 yse wats for deivery, Won

impressions han eer ears this as Mapper

soenly, and the quoted livery me tọpialy 2-3

fonts fave bea fay rlibl, However, there sl the

problem tha afer waiting several months fr lses, one

‘ay fecie ater that ave buen ected fora wavelength

thats ot the requested wavelength, Bae on our conse

ble giect and anecdotal experience concerning this ph

omenoa, the probem usally seems tobe withthe dt

{ors and thal lack of faint with handling wavelength

selected lasers

“There are two slteratves to ging through the time

sonsiming and fusirating purchasing proces just de

Serted Thesis to buy wafer doped 10 your species:

‘ows that will hen prose very large numberof sere

‘The second, and more common appeal 1 ada Se

ondary supplier of ne srs mio wil prove wavelength,

Selected lasers There area number of supplies no Boy

large aumbers of ners fom various manufitarers and

the cell them, olen wih optional packages inctuing

poser supplies and/or optics Feequetly such companies

‘wl wavelength Slt iss rom hei stack OF course his

‘usualy more expensive than ting them ciety rom

the mangeuver Eleegnisx dstribtor ae also often

veiling to set ase fom th stock

In conloding this dacuson we strongly recommend

that if youre stating an experiment with dieser, uy

several Iner at once Beste ofthe sic and lays

Jnpurchasing lasers combined wih be posits hat some

hen tay never reach the deed tention notes ay

iesbeeply ta igly avisabletokoepaumber of pares

fo hand Since the typical cost of AIGAAS Isr 6 $100~

$0, hs iva worthwhile investment However, wth the

pil high power and long wavelength aes that are more

‘eapemive may not be feet afford this oar

© Mounting of dlodes and related optical element

‘Once the sera rived, tent beset por we Two

‘maportant inl comideratons about mounting th lun,

reqaedes of application, are opel feedback and tem

fore cone One needs fo conde the best acangement 9

maiszeunwaated opi eedack an ides peo

ontlled optical feedback for fequeney contra This

‘sully determines he over psi lyout The dealisot

‘he mounting ate then determined hy consiseratons oFhow

tokcepehetenperatureol these asstableas pole This

{Sahu blow Normally the optimum dg in er

lof remperatur and mechanical sabi, a5 wi any Ise

system, sone that ss compa as pssbe and ressonaly

"id Howser, because doe lasers and associate opis

‘an te uch smaller and lige han other types ses

vane Th

‘he sale of he assembly is fen gute diferent

Tn Fig, 7we show simple une mount The sr sll come attacte toa ual ea snk Ti k neunte vi [od hema contact toxsnall metal platetowhicha heter Corthermosectris cooler and ening thermistor arc bons

‘of, This plate i then attach to asd biek thongh s

‘Sonnection thcl melaeicily igi, buts por thermal Sonductor The collimating lem is then meuated dvecty

‘fo this lock Avast way of types (ard prices of ens [reanabie Makingarather weeping genetliztion lar eos that wl be mounted farther away fom the ae Tend tocause les fedback, but tino iia toeep the feedback constant thta with asl ens cle othe ser

‘The transverelene potion i relatively animpatant: one sạn simply translate tothe coreet boddon by band and

‘en ighon down the mounting stew However, he oc

‘ng longitudinal adjsiment mark more etl 5018 Aesiabe wo ave some orto ne screw ajarinent on i

‘A specie warning fo the Bepinnig diode laser ser shout microscope sete for calimating lense Standard jeties may som lo be a denele choice esa they reso reacily avaible, bt they are usualy gute os oF Infared waslenths, an the optical feedback prose are len quite severe A supe, ow cost aerate is oe of

‘he many laste sphere eases mae pial ar diode Inver Anotherchoice when beam quality sot mportant

‘he we of nexpensive rasent index (GRIN) less

¢-Temperature and current contrat

` ofthe

ly gu performance & determined paras by the enpcrtue abit The mos aiet itor he epee tre dependence of the ser ouput frequency Howe we fave found that the Denes of good femperstre by extend beyond the dlode sll tere sany external ed tick the laser equeney salnay somewhat senstve tothe prions of te opi cements and these change with em Pratue Oncalmostunavoiablecxamplet backscattering

mM

from the colinating leas that eos back othe be Hisix

ot too large ad Gly constant im pase, ole lạ not

‘ron aotonble However, ifvrationsin the temperatureot

theapporatusstart causing the distance and hence the phase

ofthe feedback Hight ary, an cause que aelome

tv al the time, highly myteios variations inthe ater

‘erseleath or news Thos, poor femgeratire cil

Cam alles the lier performance ina variety of mays, Al-

‘hough it i acequte for some purpose to we ony a singe

sapeof temperature contolon the ser wehave found tat

Inthelongraniisuualy worththe smal extraefor 0d

{second stage of terperatare contol oa the hase OF the

‘mount or onthe box encosing the ser assem ‘A detaid discussion of temperature conlservoleops

tas bee even by Willan” and we wll et del on them

here The basic ie ee thermistor a one ep in

ahneed bre circuit, and any volage across hee

Amplified and used to dive a heater r cone, As dacs

ln Ref 17, one ust careftly consider the thermal time de

laysand the ne constants checletromistoactieve opi

‘mum performance However, we have found that i oi

ade fo reduce the thermal mas 26d the thera delays Sy

‘mounting the sensing there and thease in clse prox

lms to the Neate elaiely simple cicut wil aehieve

alts onthe ode f Tink, Ace ogra for sock

Simple contr shown in Fig § To achive this hở

ferformanes, the reference voltage ad te badge ressors

‘must ivelow zenperature coeicens.Inadaion because

‘her edition and ie current ts advisable to ewe

"ose the ster mount in some sort of metal contnne THis

tas the ad bones af keeing dus ou he sytem and isolating te er syste roms acoustic wiraone

“The le eporanlclementin setng va dodc hư

‘he eurentconrl sitet ti ie to cscommend x perry sf eit bec the egetents i arons

‘apeiments an Be so difeent, In very este one neds to Slam wit s low-oie current source and some proton

‘gana unwanted wenlents thal can destoy tặc ho Sạch {Setup ea range ram s balo anda prenoneter pas few diodes and capacitors, to ute elaborate cuits Often

‘he primary consieraon i celtnga Seu nis arent

‘modulation cpabies a Fg 9 weshow two sale or

is See ao Bradley and coworkers” Av dss in Sec I G.staimportanttomount the protectsedinde ght

‘onthe ser mou

.Tunlag te anatomic transition The main clin sing die ses in motto physics experiments the problem of ting them to tbe feiss wavelengih, sally that of ome aon arson

‘Wehne developed some empirical provedues or are Ings poblem To nda trasiion weet heer caren lhe value we would hike to operate, and then tone te tepernare ofthe ine to near the caret vale y obser= Ing he lnwr's wavclength om a spectrometer (A note of

‘wamiogif one flows the sual procedure of ending & olimate bar ino the spectrometer, which 0 doubt bas etal shits the backscattered igh rom the sts wl fen

‘Shun the Iaser waelegth to shift and make the mei

sent neaingles) Once the liser i net the core tm

perature, the corres hen rp emmped back and eth

‘ver lage ange, while the mount temperature adjusted

Dbysmal nerements The luorscenc or absorption fem an

_slomic abortion ellis used to determine mente desired

Transton wavelengths eached, Becauseof there may be no combination of eucen and (empcrstre the tuning Ps

that produces the dosed wavelength However, thc may

lk be several and one must choote which st desrable Winasimu see powers eed emperature soul Be chosen whet the ser onthe tanston a high cure

‘nthe ter han, fonlyasmllanoua’ of power eneeled itis beer to pik low current pot so that the diode he tne will be maximized (although the Heidt a ap tude rose will besomewbat larger We repeat our reins warning Never bay asingle ser and expat to dosn exper

mene with There alas significant probity that a

ven lise wil havea tua ap just atthe output wave

Feng of interest, We have foetal, sf no eater fs

tok ese this probe ares between abou 0% and

{efor dice baths oases operating nas #52 nm

‘Avice below, adioal opi cdback 1 tne

the leercanalme alwaysorcet goles the deed

‘avelengte but ofcourse ti reteina morecomplesed

evie and procedure

-Avolding unwanted optical feeeback

We hae mentioned several ines that theater perfor

ance is acted by opal feedback One of the unique

Feature of dode ser eltive to most ober lasers their

Andorkhingxemivry to ach fedtac Ts ca be oth

Nessiogand.a cares In Sex IV me wil asi the lesa

aspect re we wl consider the cuse

‘As scl ia several eerenen.” the sensvity of

hide insert optical eaback are froma comin of

{estore Fs, the pin cute is tery at sa fonction of

wavelet scond:thecaiy fines squitelow; and hid

‘he emily very shor, Aes ceva the veal gn ofthe

‘ystem bes on extenely weak dependenee on wavelength

Sed thee are eaves ew photnsnshecais, sth the

Insing ren: ery cal pertutbed Ih ado, when

Tigitsretorned loth ser acs palodetecoe peer

ingame carriers nthe nto aed Retin the ne net

fain, Dead quantitative dstasions ae gven in he reer

hee, buts pbubly more usefl here fo ge some Ee

‘rlrae fr laboratory work asiog rervoning laser with

toons cup fests We have already mentioned the

problem wih Sarening rom speceomete fre ean say tht ithe ler team collated and ie sis Th gener

‘orface which seatesstronaly suchas burned metal ora

Unt a al there wll ea sgiteant oct on he ser

‘avlength Creucncy shits on the order of 10 MH? or

‘pester at exilyebcrvble variations in the tse ampli

fea the dntance changes) but ste surface has ll

Siok appearance here il probaly be ile eet TE the

tam i going trough a focus larger faction ofthe sat

tora ight wll be fous bak into teaser hus nce,

Feedback sensi, We hive fod thal ava general le,

‘one sannct pt ansting eve gos! apis gis, tos

chou causing lage perturbation the Tse These

ules must be cosideted aly 38 vary ceie guides ince

tows tes of lasers How mich fedbick can he tolerated

fenerally depends on how the laser i being used aod the

Sali ofthe eback heaped pase of the

feedback are constant can often e ignored unless ane

‘cos io san the ac’ wavelength, Laser with an out

facet cated for reduced reÖeciere are mace sense 0

‘optical feedback the anced ses Or he othe ha,

Tasers se up to have strong opal eeback o contro the

‘wavelength are covresponingl ess senstive to sty eed-

Nó

‘Wher using serin an experiment where spl os

‘iooing ote optical ments des not adeeb, one

most use some form of opie slat The simplest and [east expensive solaris anattenaatorin theese, bt Bắc

‘feoureis seul only when one can afford towastemos of

‘he later power, An altemative fa cicular polarizer th oes pot waste ih, but only work ithe indent and fea beck it have the simepolarzation This sil Bưyivex: petite When the polarzatione the return lights iret roo the nclent ight which happen there ate ay bie fringe sementsin the beam # neces ose 2 Fa {as soltor” Unfortunate these ally sot overa ies

‘hangs he Behaton of the laser referred 039“ ‘Noell one must gain considerable experience wit ede Tasers before aging becomes elvan compared to cat stropic fibre: We wil dacss aging fst Although we Tin not done careful etatisicl ste ofpngbehaior we

‘a provide some abscrvations ated on ou experiences triton theenderof 1D eer ist while operation t igh Temperature s/o high currents can conta o ai

‘eon manufacturing processes tobethe dein factor: We hihad some srs hat we sed exes for

‘ocr thee ears beorethey showed any aging whilechers hanged rated manta ew wesks Usual al he ser Jina gen manafctoring run wl genie ashion

‘There area varity of was thatthe characteris will change with age One that hardly noticeable toease ác

‘sly slow fe that the tonin sep wll ae mơ This means tha one will occstonally havo ads the cr reatand/or emperataretoksep the scone tonieseso- ance Thisbecomensersifeventaly the sh ease one totes the ration enely, bt the epposte can aso ap pes namely alse whic formers could nate ane athe Fesonuace may sặc HH cum Aging dif rate củ be

‘he heralconguststy othe lear ote het snk

td changes inthe laser to nonradiative recombination There ate wo other snp ping ta aemore ne lec for the Tse 0 ei in more than one Tonga

‘mode, which often means tha higher aad highes eueen

‘asthe sed io ublansitglemodenuipa Thesesond hae Serie thatthe spectra wid of he single rodent

an gedualy increase om tinal 20-30 MHz pt ral hundted mezaher

scoveed many ways is canbe accomplished and west

‘hese ee inthe hopeit may save others rom epeating ou

caperiencer A major wealnes of doe ters Bala er)

bef transent, whieh cases fo0 mach current 0 Mow

rocuces to large aback vollage ross te junction, abe

fatal common SaylBitcan hepye sithingransiens

‘when tring the lser an oe of although one abou

‘ust putin peotctve cei de và ri Khen

the ine power supply ssitched onan off nents

Isshonerenary tbe concerned withthe potenti eects of

3stdennl daconnecti of the power suppl, ot intermt-

“ent connections in poster ables rth ac power ie Ot

Sources of wansient are discharges of sae elect an

igh veltage aes nthe parts ofthe ia These at wo are

Iininizes by good grouuding apd shesing grocer

‘Abo the rotation ode normally wed prevent xessve

tack voltage sould be a clove fo the Ise a posse If

there i even a aston ofa meter of moderately sede

cable bewees the ser an the protective die, high vl

{age spark nearby wil often detoy the ler, We should

out Oa that a er whic hs been lst wi olen

Continue emit ner igh, bu he wavelength, threshold,

sn tpt spectrum wil be ate dierent

“Althougheletreution sty fa the most common form

of ext for dode lasers, the ner tha are not moted in

‘roe canareaho qe delete andone muse sata)

‘ot to tone the lasers the tiny caren leads, while

‘ousting the se oF asocated opts

‘Considering al of te possible ure modes forthe di

felis wed that on te anerape,thelasr eed fe

‘replace approniatelycvery sn months This here r

‘hes nse dhng fr whatvereeason or becoming poe

SN to une othe appropriate wavelength Presumably the

‘replacement rate would be mah en he fasers er eft

le and not alas being tampered l cong ex

periments This average rate for moderately expensed

ser and failure uch more feguet with inexperienced

IV TECHNIQUES FOR CONTROLLING AND

NARROWING LASER OUTPUT SPECTRA

Several techies, both optical and ston, have

been devin to marrow the newt and onto he cnet

Frequeney of diaelasers Asmienoned ei, the acs of

opicelenback on semiconductor diodlasers areboth peo-

Found and complicates, bt they have een sted in de

tal tn parol, the ofecs of pica eedack on he

spectral properties of these lasers cabs fund ip Ret 20

However theesence ofthe opi feedback methods the

simple estat by ineresing the quality Tater (Q) ofthe

Ines rent, the neni wile reused Thimyje

implertenation ofthe occa eto for spect nattow-

Ông e eo ket back othe ase 2 sl featon f

utp power Thehasieletrnie method uss feedback 9

{hears injection eure to contol the laser Requerey

‘dh the simple opel and ipl eleetoae mets ave

severe Initatons in tenes af general applica ‘More eltoratefequeney conto systems ar usally

necessry lo đại wih the vay of dhe lasers hat 4

sommereslWysealbje, No ne method has een fond 12 furrow the newt and onto the regency of al pee

Df ioe lasers, Here we wil ey eiew Some a the mare

—¬

Ve hotld mehton tha thế are many eros that ne wit nd m the hetoeriseSetø memeronene ước The newts and frequency stably THe mow corimon

‘stake thatthe experimenters will esse the esha boise onaertosignal mide asco loop and se this iar

‘aon oinfera equeney abil Suck messrerets do

‘ot goarante tat the eror signal tally represents er frequen Mctuntions abs they ae ave whsstematic cogs Ploqe abd coworkers and Petschin and Eze Kae!" have made more rei netstrements ad pointed

ut some ofthe pase pals

‘A Simple teecback Some limited sucess in nartowing the lnewith of ade ser tas Been scieved by ủng dư ordedl le

“Among the opel lens tha hve een wie for fend Sack fe sample mirrors etal” pratngs™ he cac

‘it * and pase conju the resting tet mist be decibel a lasers with complex resnaiors

‘wherethe sider nes and theeleratopttelemens all Flay 2 ole imststing the net resonator stactre see By the semiconductor gain reliun By providing opal fd ack trom sal mseraro gas plate place costo oof the ser facets, sometimes ne can force's ulinode ser tocwilateonasingle mos, orinduce stele mode se 19

te sero the biden “gaps The iitations to this

‘aod ar that doesnot work with al ners and egies some sor of reuenoy referee to stabi te l=

‘ers egueney Als, ss wth any cole sonar, ican

be eile to achieve longterm sae perormance wil sch gương

“The method of the “external cavity se” ses sei: eatin (AR) coauings 8 the dade laser chip sed some

‘external optics fo provide the laser resonator Tie external

‘optics ma contain Frequency slecne elements such a6 tang” and/or ean vi the rating bing the least

‘rpenive and most common A varey of geotctriesare

lenge boas hey requis having te ser code facets AR sted, whi suai an expensive ad portal prose tlre Evasion oe ma) nea acceso both outp fees Ivhich cfm diel given she packaging of commer devices ta prieple, this eto shoul work whales fof dnde lasers although only a ied aumber of systems ave bean bul and they re not orercaly avilable,

"Anumier of variation om the ase ester xe hase brew demonstaet These aclude the use of prams ielnngent Riem and various omer clever optil seme (cf particular nee the paper by Helena eral") An exampleispunting AR coxtingson oe facet f thease hip tnd Dulin paeudoenteral sity ners a5 cae i

N16

a

‘te next section This fesniqu has ee 0 in contol

Ting the spect properties of 70- dade ser

© Paeudo-externai cavity

‘Various tabortoris have showa that fony one of the

facets ofa he anerss AR coated, the laser news

‘neraerowed ane welaton frequency sonal by pro ‘ing extemal frequency scectve optical feedback, Prt

atl any of th ah power (> SW) commer là

ter aleady have rebel peta contigs ome ont

facet ana high electors onthe Back Inet Gibb and

Swann and collaborators have demonstrated hat wit

‘modieation these commercial lsete with esting ca be

Spectral nsrrowed sed tune efectvly wth pratng ed

fick" An exumpe of sacha sstem i shown in Fi 11

This ethed ta combietion ofthe wo ted above tn tha

{ts ot realy an extra eit se, since the or vi

Ines without he extra febac, bu the stem ean operate

‘otha external fsdtack dominates that fom thelow re

tanee at, Thac dalcssha»e hndunehul Hnevidl ơn

‘Ge oedere 1D Keo en, a the einen sally

‘donated the mechani] and themansaiiesin te

Feng ofthe grating laser cavity, This newt can bee

sal hundred Soest lage fhe cay ep sno

{etrnialy stabilized Weand others have pn sh

Serstobequtewell ated fora sarety of eppisitons Their

‘aes aretha they ase standard commer lasts and ia

expense comspoent and he rai allows fang over

{ange larger than could be exis overed by temperate

‘ning, Alo he toning cn becontinvons over mos arger

Special anges, apd itis qu eas) to set a keep the ser

Trequency on prtiulr tome transitions Minor iil

ties the design are tat he rating ament smartly

sensitiv snỏtoachieetheneeesey degreof olimaion

30tBeluệt ạÖttheđsteaceletien te le athe coll

ating ca tay he ast to wth ew micrometers

its tn prt its adequte to hae Ibe lens pation od

insted with a fine-piteh see, with the postion to hat thebeam appears thesune dameler tothe cpeover a aa

“Therearetradoofs one can mak nthe dst een

betvsen renter fecdback, and hence mar frequency com

‘with = 70% eck to he laser As the ating rotated {he se wil tune coatinuoudy over a region of about SỐ {Gite spanning the pk of the semisondestr lar ety resonance, To obtain continuous toning, he grating

‘outed s that, ae i elates, the change in the cavity re fant frequency de to the change in the envy length

‘aches he angle tring ofthe erating." A smal (2c) zoe speaker disk placed betmsen the erating tM Serowand the block on witch the gating 8 ousted avenient and ineapesive way 40 olae the gating Smoothly Thee wil fen Be # pap the ting of 0-80 Git tine reaches the ext made ofthe sl semicon duetorcavity This pater epi ise sth se ued father omit gn pe, ih the ange of optimus on ing gradually desensng The maximum range the oer sravelength canbe pled from ts gin oak w about +10 mat wich oir the caning ange pr Soe mode Sout

1002 Wônh he Eedirek reduced 0 255% to preset

mp couping themaximum sangeet cootinuons toning about = 6GHe and thefarhot te equency cant polled hao nm Gaps inthe tuning ae esl led by adjust inthe lnercurtent or erperatreto sbi the fequen af

‘he lise diode modes Te opt power abit 10 mW

‘we hs onsput coupling

TNT

sdback trom hgh-2 epslcsvdies

Another opi eedack locking aster hat we have

sed quite succnlly# iagramos in Fg 12 Tn this sb tem we aie weak pect coupling ofthe se’ carp 03

igh optical resonator” The geomaty i uch hat te

laser sees opis feedback rs he Fabry-Perot cavity ely

hese ters reueney matches a ese i hs as

iy The rev shat he couple ase pl abt sper

has lome losses at cavity esonanceand hese’ freuen ©) atomatialy locks up tothe eat esoance Ents

Say the liters neni can be redooed to ee Kinhetz

dr the lasers center feguency fs stablized (the eM

‘ne of he hnitatons of thissystem Shae cequies some

‘additional iow elceonies to hep the le locke to the

Same ity efor long tires va lo kep túc ner vợ

"hroized withthe cvs or fon eats (grestr than about

GHz) Without the addtional electronics the laser wil

“48 locked tothe same canty mode or mesa ary Hot

lesthan 1oasmachas 30min, depending on the sabi of

the cavity and he vmpertare an current conta fo the

Inter By redcing the dstance betnoen esr andes ta

fo caterers aod mounting theca) sad usr ea pes

Ssurtigh tempeaturocoatilla enlosire we have Bok

eo extend this several hours wthnt elem com

{rol We apd others use this sytem with goo! results with

Uunmosited conmercl lasers operating im the diode ase

sntvlength bands a 78,850, and 1300 nm, With rater

limited expenene, we Fanebem đrappcim inthe rss

of is metho fr unaltered ganguied les operating at

‘50mm However, the meted appears to work wi he te

‘dew gided version Hat Rate some AR costing.” The

Imajoratvantaen of thsnstem of feqdency onto artht

‘he newiih very narrow ad the stay etermioed

by he extemal cavity which ean he made vey gid and

“asenve to chanesintmpertare and stmospiens pret

sre, Ass the nsec retains sre igh speed mulation cs

flies The davantazen ae the esti to sail Ser separation mentioned above, athe fact that ser tuning range (and pps) ssl etetallythesamees that of thebaie ustblizd ler

There ares numberof optical congraios tha sản prauce resonant opti edtack foxy a high Qesonator botinpractietheV configuration showain Fig 12 ery convenient one Thealigmentpeocedurestrsighfornars Sndafler alte pacticecam hedone a qoicky when one Secognies the proper signal shapes During the ligament

Sd aera tibet tsieep th ses aquney over Several orders the Fabry-Perot and to mono the power Irani through the cavity The eflets offend om the cavity tthe laser wll Be obvious in the ship sỹ te rant ings By seeping many cavity modes he ets ofthe edhack an be observed The stem egues

‘only small amount of teaser soutpt power = 198) or Tocking but for agament i air to sar with bigher powers (~ 10%) so tha iseay tose the beam Aer one rcomes amie withatgning theo eedack lock the Feedback pomer canbe rece This 10% of the utp i spi of and vent through an tena al les tats proximately modesmtchesthebeam Pero cavity AN easy way 10 determine thatthe mode tothe big Fabry rmahingcoret st nme that the rdm team rei

‘efom the Fibry-Perot cavity i about the sesize ashe team thts incdent onthe eat, Nex ok os

‘hat the input bea fe centred on the Fabry-Perot goi

‘mirc and tha the ees ben atssnal sgk it

to the epot bem The vergence ane canbe gute small hot snecesary thatthe earn Beam afew spt dame ters amas fom the inp bear by he tie rete tô hệ laser’ One shoud also cnr that thee act two cup beams tanned through the canton resonance (sei 13) By setting thearteuatr or ver ow powers ore sl See the sul Fabry-Perot peak structure ia the arsed High then asthe eedbck winced the ser wil bein 10 Toe othe eaiy resonance and the Fabry-Peot shape wll

‘ouden and become sguacsh, The sige wl ypils broaden ta few hundred megaherz corespoding tthe range ver which the cavity contecs te ses equn) Theteztback power can vencreed to eaance the cing range sro race further the laser’ tnewdth, Who the Feedback becomes too strong the system wll become uns we”

The phase of opal aedhack(astance fom the ser

to the eats) optimum when the power tanmited

‘hroagh hecaiystaximrs Onecan ee thelok tothe

‘piu condition by endulating the ath eng fen the rerio the caniy (witha PZT) and detecting the eset

‘ed power Ths sal then demas with a lock Smiter and fed back strmialy 10 canto the pono ofthe PZT Varations inthe opel fedback phase can bề

"niimizel hy ôodtee:Senlol hilty and by making the AUstance fom the ae tothe savy mall la kẹt ween operate these optically faked ystens witout active ee tie com

“Alsough commercial cae ate alten adequate itis ssefl lobe able to make simple inexpensive tanable Fate}

INA8

evo eves The splest method is opie ser uaity

‘irae co a cylindrical lovar or quate ube witha PZT

Ask under one ofthe minors so that the city a Be

fanned, It one of the mirors ean side toile tubular

‘out thecaiy ca Dealigned ate othe cool com

den by aligeing with 3 Ise Defoe thelist mito

odin place Forth bot stability its wel ta have

hermetically sealed cavity hese simple cavities tis a

be accomplished witha glue that does no unnecessary

ste the iors cục s3 Tracon 21930 hot, mendone'

this rotct does not representa reconynendation)- An th

{erative design ics ae thread onthe va pacer tose

{he vit othe proper leat For ont of our ode laser

Sspectescopy wen relerence cavities wth iss of aout

100 and ee pt ranges of 025-8 GH

Other optical feedback techniques

Ore moahic or serinonaihic extend cai

cách ith gos spectral alts ae bee report a

the eratre, bt hey are stall Taborairy tt dees

‘at aenotcommerially aaiableand uly 0 ora

‘Thee re indetions tha some of tee stems wll come

omamerilly sail nthe near fie bt 8 nH

‘here wil te broad spectra coverage anti soe

F Eectonic feedback

Theother competing method For laser eguen a

an x eerote feaack Tà siadghforvsnd lo te

tlectronic feedback ta lock the center fequncy ef diode

laser loca or Meme dưopton lines using standard

Inter sttlztion methods” On the ober hand asrowing

‘he ise’ inedth with ecto seron ea mich more

diel task The pater that he requeney ro sec

loam exend to sich feqenies tht most vy

‘ems are not abe to act Fst eu to correct the Lasers

Fhequene uctations A fe groupe" Rave been ssses

fal developing very fn (lew tx delay ime) elcome

servonystre that can Be tod fo narow the Unewih of

‘ode sere if the lasers tin nets ato bod

‘ota with Lines on the ede of 100 he eet

shel with hes lechisgueePletroni stems avs

‘vantage over most ofthe optical mets ha he do

fot degrade the modulation characteristics of the Ise

However disadvantage that they do ot extend the le

see tuning ange Unfortately, considerable expertise

"etroics rer odoin and Du the necessary se

Hybrid ystems

Hid desis ar of two base 9e the irs eae,

electronic ease ply hs to ame act that cone

loathe latrfreqeney by optical fede In he desis

Aesrted in Sos, VB IVC and IV D, for eal, this

‘vould etal moving the ead roe ce grating wing» Pi

‘Tocleti tance Typieally this done tachiete ong

{erm ffoqueney sai y lokine tắc cay free (shore thelaser oan atomic or molec ation

Promising sls havealso tc otained withered

typeof hybrid pte which ase electronic eaback in ad

‘ition 1 optical faba to reuse the lve’ new this hytié opcaeetronic tem the optical Feedback

‘Sas fo iil nacow the laser to the pois hat es sophntcated lect (than st rentone in Sex 1V F) fan father narow the lnewisth and stati the c's Feequeney With och systems it should be posible wo eleterequehy stables that ae lied nly by e's

‘Shit to provide an aque Frequency discriminator Os Ing ths spe oF servnystem, phase ek Between iu sets have boen detonate

Injection locking {Mis abo pombe to stabilize the Fequeny diode te ser y optical injection eeking “The quency of an iiued diode ce an be lacked lô š sieeinly nao,

‘maser Isr eslstor by coupling sal aout of power From the mart lise no the lve dose er Ts eh sigue may be uefa or some appatons (eg gferl0E higher power) but obviously doesnot meet many speto scopic neds because Ya pond mtr faker were thi thethdelasr mould not be ended Thenoableecepion is that inetion Tockieg allows ove 2 ase the high powers Svallabe fom arrays o wide hanna! lasers and tll ai sith foedback-stable ode”

|e Summary For sme spectroscopic apleations the spectral hat acteristics of commercial diode les ate good enough = they st, hat for many thes that ot te ese Abo,

‘owas aer cam he quite ful to tne in 3 on tells manncr Unfortunatly, nano the existing een

9 stbitzation methods (perhaps with the exception af he

*neral cant stem) are ahlefonatrow the newt and ental he feqveney of all ofthe types oF xentEendietor lass that are pote useful atomic ses We do

cự tan to discourage the poten! user f high esohon tse, becuse at ny wavelength eng clon

"v08 very well and provide unable ratew est srs from commercially avalable ids Such devies have the

‘vantages of ery narow lnewieand excelent atl

fd abil and they ate och simpler and mote sabe totunetoaparvcuarMequeae than ae unstbzed ise,

APPLICATIONS Having discussed how to build and wse die ses we

‘ell now discus some of the applcatiags a ato ps

1 Ofthenumerons possibility mefavechoveto dette

‘few novel appears that demonstte some ofthe new

‘apatites of diode loser that havent previously Bren a pst Many of dhe cxaipes ate related fou ov this lg rather hese are simply a number of epresentave simples ha are most amar tus

‘Optic! pumping mm Physics wataethcliisourecfarspdlpumyingandrcb:

MND

ing of polarized mes Many spplisations of this pc

terevioned by Camparo" Here'te wast to mention billy

Some inering new optical pumping applestins ing

HO

Diode lasers have Seen used extensively equetey

standands and stoi sk ass applientions they opi

Cally pure the stoma ileet aden detect he aos

that ave undergane the microwne rueney clock casi

‘ons Ferutousy he atom ued in some of ue et fee

‘quency standards (rabid and csi) have resonance

line wavelengths hat areal produced by semicondoctor

Taser The mork in hs area stared nearest te i

40 apd cootnues wih promising resus day" Sige

‘fant research and development eons 6 incorporate

foe lise ini rbidium, cesium, and other atomic

frequency standards are vader may arcand the word These

ffs ate driven by vast improverents a Signal-ooise

fat, lima accuracy, and the reative simply b>

tained by ang de sere igure 13s schematie a

‘gram ofa diode iser-pamped cesium atone clock The Scrsaze fist sed to prepte te stone beam by puting a

the ston ile the apeoprte hyperfine evel sig opel

puriping Then, se the ong have pad through the

Imrowave rein, ase exites the nitaly deplete evel

‘has the ierowave rnstionsare detected bythe nerease

inthe dowesteamfuorescence

than opical-pumping experiment of » diferent sn,

Sireater, Mobibrok, an Wcerdan” wad he igo

de laser to dive Nery successfully a eubdium “optical

piston." The opis! piston i anatomically selective it

"hat inden ys ight We a this under optic! pump

ing snare a Key lent nthe experiment was thề so

Scheme of wing the relastionoselatonsiebands of the

he ser to asst optical pumping of Rb atoms Te hs

parscalarcatethe GH: grodndstatebypedine spit of

Raabe the relaxation nlation eguency fhe 70

amlaser Thos asingleliser allow them excess

oth ypersne ground states, which greatly enhanced the

‘perton ofthe "ison.”

‘8 Applications using fast frequency modulation

‘Oneof the unique nape of semiconductor die srs isthoense wth which therapies nd frequency en be

‘lated Thesmointfmodulationcan beboth lege and

‘ery fst For common diode laser the modulation response fxends toa few sgahert, witha petal ses capa bef modulation rates of more than 10 GH This module thon sapbiity has applisations i spectrencopy aswel as bother feds At mentioned cater, modlaton ofthe ide lasers jcoiencudea poVuee beih AM and FM, Out a

‘any cates of tome raion the roquency modulation Isthe dominant fect and we wil focus attention onthe

‘The frequency modsation dominant simply cane te tonic linewidth corresponds to Sach sal faconal

‘change i equeney ‘We can picture the frequency modulation of thease titer n the time domain o the eanncy domain, de Peodngon the particular apleaon we et tanks the Frequency domain, modulation of the injection currents igh frequency produces a lser spectrum Si moRlaion sideband The application of modulation sdeands 10 al {peso esha proven ver ws speteacapy and

‘ther sppiations* The patna advantages thse ot fal bettodyee meta is hat they insrease the signa to-

‘oe fallo in detecting absorption and cspersionsigrals

‘Tho technics have been extended (0 ode lses 9y Bjorklond," Lent and other The dd ase ase orpizatedsomenat by he adinal AM that comp te the desited FM Lesh npatcular has sore out the

‘ects of having both AM aad FM modulation sua: ely

"We hive wssoptial heterodyne methods with eguen- modulated dod lasers to detect alkali stoms and optical cau neenssc vi hạ sensi Exieral equeney Indios have bon abo sed with InGaAsP lasers ode (eet NH,tsing FM spectroscopy." Ohi” and colar tows have aehivod excellent reils with opialypamped

Ry cloks by wing requeny-moclatd laser dios for

epunencbsrcpay sips Pradathypeae ced

TN20

‘optical pamping nd high seosvity detection Other apple

tts of fequency-odulaed diode sets inca sone

uricaton spre, lnath esstrements range Fr,

Sn se rar

Feequeny modulation is been ane wih the ead sal ede

Ins operating inthe nari Methods have been deel:

‘oped sung medslson at two frequencies (emo tne

relation) to detect mec species wth high sensi

Ty The tecaiguescaployed with thee ses ate ao

esta ppb tothe Ga ser Tie inrese te sregtho the modulation ofthe ine

{esto corre tis possible o spread out the i aes

Spectr oma Usettesdebands Theveidcba can

verspctal wins of rany slasher Pare 1 ss

a spstam and ner whose inton caren (97 mA

42) fe modulated a 367 MH with an amplitude a 4

This modulation proces eight srte sidebars sae

ty the modulation fequeney, tn ation fo the iia eran des not eerie brood the spectrally nao

Tose (=IOKHE newt), Potential applications of Os

igh modulation index ste inca aver equeney conto

faa lel estos fr clerentcommaniation sates, and arom ad molecular sis experiments where mi

ners eguocies are eged

‘Sore aplation of sods laser fequeny nodulation

are tet siewed in the tne domain, For example, rah

‘huping ojmpins oft outp feguonsy Has ba ed

‘cosfly in several expernents Watts aod Wieman™

‘changed 10GHlzand become stole towithin few ces

erin tine of 2s This a8 accomplsbed by sgl

changing te injection carte through the ser ting

AnpsmeLteb ore puke Wt this highspeed stoking

‘tees posible tooptialy pomp al the store Ss

‘eaminioaspeic magnetic subevel (FM) sing sng Ibs Normal his would imposible case cst has two ground state hyperfine levels tata separated By 32 Gite However, niacin ofthe tie took the atomic team tops through the er eam, telase quency a> Steed to excite both eels Robinson” bass ane Fregueey jump isc gue to polyize arabia cel with Snes This capt to apy sep the see fe hen 9 over large range a cold anne gue

Ii texeexpernent wat uned trie the number of lasers needed ov opie pupa, bot ioay Bd reat syn ties of aoa apes ease phenomena “Arecen appiation othe fequene tpi capa

ly ofa srs isthe stopping of atone beats Eetmer et {3 showed tty rune) eben eight om ade Taser it was posible fo slow and sty a be of soa atoms To achieve he nocesary feqieac sah a sophis

‘ital oudbandeleteoopic modulator was elope A

‘Sorrespontingoqueney chirp every easy toprouuce wih ode ser by merely adding a all stot ramp the injection current Wars and Winn asd this technique to Slop bem of cesium atom” with a suspesingly spe tndincagensveappaats Salomon etal” hivecsriod ot

A sina experiment go study the optimizsion te 0 ing They showed that by adding 11E-MHz sideband tothe lawn thy could eobance the mabe of stepped tos by Sa, Resor Shohy ofa have ved frequen chee ide ses to stp rubidium aioas These varias expe:

‘ren demonstrated tal, sont iowa atoms he

‘Feqveneymanilton capa of die srs ao wall sito probing somo veo Sthutions apily sough io avoid distortion

The rung TA velocity spread of dhe scaly stoppd som reported in Ref 61 935 fms By the 30 Nie tinewith ofthe dod: hse, Toimproveon this Seto, Fan and Wien sloppeatoms inal maser using Aciniystabliae er ofthe type dese eee 1V DI this eas the fequeney was camped hy changing otk the

bế curearan te eoghefthe Nahilzadoncylọ tướng -apeseeketictraeuhecr) Tắc geadoflhecaot spose Ssttecthan tat of the er bot wil adequate for ato Stopping Wiha saby-sabilized sopping Isr, the ma teva topped ators was ound to nove dramatically and

‘hei vel spread wax stay salle We kate

‘bine similar rests bs stopping atoms withthe ht fiom pratingcviy ser the pe deans nSee IVC High resolution spectroscopy

We mentioned relly the improvements that cavity looked lane have made fr stom soppine This only one ofa age number of experiments mide Fost by optical fees sblination The teebgoe pfotide a vo mãn row bart sours which valuable er igh lution Spevtssopy and other saperments bere

Tnexiaensimpoctant Aldoagh often neglect he Eng Ish iertuae get del of orefont work on dod oss Sabian and applets o high eston species

Dy has bon doe by elchorsh and coworkers” Other

‘amples high resolution ad high cstiy seston

ls band vig id See Tape wa ge

Py ae dsc in Rel 66-69 Figure IS lusteates the

apts of eaity stabi Isers for hgh resaaton

Spectroscopy Ths Fre shows a orescence specu of

‘the S-6P,, transtionnceiom obervedin single IRs

‘selloscope ace The spectra news Were ited et

ely By the M2 sural ew of the son, ad

had wo contain ro the ae new pure ao

ilasrates Pow the ape stably ofthe Ise lead to

‘ery good wnal-to-note ratios TH lượt ke se 0 make

revise memurements ofthe Stark shits snd the hyperine

ructure a he 6P, tate of cesium, These mesutemens

dan cern fons 20 KH

Goodexamples of applications that vse he uigue mod

ston eapubies of ode aes for preion spectoncopy

omy

Rion tesco teers Ấn

srethe work of Matin and co-workers The hae demo Stated 8e seelkel seseenpy of BACT si vec

Inthe work of Gilead Gallagher” pcudoeste

al eaviy taser with rating Fedback as ie to dy ve locity changing colon in vd, Using ssaorated 2 Soeplion testique sod this costinaosly mabe

‘arr lse they were ale o measure olson i

‘orton oe satrated absorption ine sbupes which were

‘sal fcton of he IME natural ncwnth esdhacksablied diode lasers are uniquely simple and inexpensive source of very narcowhand enable igh For this reason, they wil undoubtedly be ely ue oF igh solution spetroscopy the are

‘which we have not aresed in detail m thi article Often

‘hese appiations are just extensions (0 dled srs) of selbestablshe tchnues of spectroscopy On the ober

‘na thete are afew apications that ile the unique ables othe dine ners

‘Diode aes stabilized by optical fedhack have ben found tobe much ttter than unstable aes for Hạn rekon measurements of foorescence or absorption where the signal-to-noise ratio important fa ome cases teen

‘ck not nly rece ample noise o the er, but sho reer some previously unexpected nose on atomic pect sociated id the laser FM spectrum Inside ses Tor pecision petrscopy some workers have repo tha

‘he measured igalto-nleratior are nc lower tha c ested Forenampl, we observe large amounts of excess ose in dae ner ndueedfuoresseace a dee absorp thon measurements of the P= to FS resonance ie m Cesta (see Fig 16) Thì ngạc rau trợ te reaeetey Auctuaons in the diode ter and eliminated when the Ade lasers newieh seduced by sing the high- Qeavy Feedback lock Two supeising leatures ate served i his

‘acest nite tltive a what one would expec rom ample

‘equation analsisf the ser tue transition sit

‘Such too larger and Second, the nase can also Be ay" metre wth respect ser detuning from the esenance ropeay trating coherence and atom saturation Wit 3

oy inser source Zoller and co-workers have provided

“avetplanation of these observations

“Two sgnfeant instance in which te elimination of

th aie fs ban a major concern ate the new optically ppd ees clocks eng constructed at NIST an other

N22

aional standard abs and the precise measurement of

ply nonconervation cesium sing an optical pumped

team” Tn thee experiment the wef tack stabi

Insers has een een Beane ofthe reduced nae in he

tome Baoresence

E SelfJocking power buildup cavities

Another aplication of eaek fom high-Ocsveis

the saocking power-up cavity wich ean provide

Bi enanecmens i ser poset One obviots shoccom

ing of diode liners i the seal ouput power, but bday vital ane to vere thishimiation nse cape

nant where erste optical absorption The haste

fsuch sca the same assessed in Sec IV Dut the

pice areangaso that aargefeacton of thelaerpowet

‘Retold inte the locking ests hiram the nae:

‘ity power becoming mc higher than te cutpa power of

{he laser Buldop eaves ave been used wa le fo

Feedback sstem to erp tecaviy and inser frequencies the

sine With a dlode hư be nec for elstrone feedback

ame clined ecsuse the opal esdbck Ios the

‘e ne-way poser Butiyp Rabe ben obtained ih och

` "

Tông p9 S745

Tanne, Masterson, and Wieman™ asd a locking

wal caity ost how aston bused tang

‘wave ca climate mcs atom beam, Using this eh

‘ig hey were able to reduce the dvergonee of the bean

Tn another appliation, over | mW of nab ight at

-32amras produced by placing poasinm eshte crystal

Inside such sel ooking tilda enity to proce the sc

fone armani of the de fer fg” With te proper

Tasers andra it maybe possible owe this apposch 0

schive several milivacs of narrowband unable ight over

uch ofthe be region of he specu When hs tec

that are themsehesoptialy looked to baldup cuits

ay tene of mile wil baal, On the the and

Forappletias not reuiing luge mount of senda

‘mont ight, Ohsa™ kas show thats posible to do spe

Treengy ih the small amt of conden ht

that sete from ordinary dade ser

Trapping and cooling atoms using diode agers

Another ci which tube lasers have been

sed very suey sn coking and rapping neue

sto Such experimenter ogre several erent ser

{requencie with linewidths of es than | MM, sod thúc they are quite expensive to se up using de esas THC

fete pectin the wi of dye ler coe no tapped

Sow 8 we range of atoms phys experiments for

Whickies would therwise be welled The ae feat

nd gmtingsuiilaedl diode laser averonis this probe,

‘Sako and eorwortert™ have fcelly cooled oy ator

sing a thre denon sanding wave fed to the fe

side the eso resonance ine (x calls "ope mse

67) This as produced atone spl containing 3x10 omit temgeatueot 100K Ina ehtecexperient Found co-workers then oerved the ces oak” Ua tion between the two groue pertinent cold Single? Thelow tempertare alowed an neractin lie (of 20 mand hence a linewidth of ony $8 Hin ah tera tin vole of es than te

In eter eaperients Sako ea have suceeded in trapping store aing «Zac shi spontaneous ore tp

‘ret with de ser Using for Sbilias ses, sa Pes of upto #1 atoms were tapped, and rapping ies

‘greater than 10D mere elaine” A varity of trae tions tween Qe rap stoma wee sta In Bot he

‘piel olsun eapermeatsand thse rappsatom ype

‘ents atures the ioe ses lhe than tha cost have een important, There were smumberofabestdies where

‘ery low ampicade noe aad case OF raps regency changes were valuable

Trexpensive die laser are proving tbe valuable tools foe atone specrosopy Tey oer continaoaly tural Sources of cation wth linewidths under TOD KH a owes of mW or ore They cn cover auch ofthe ear Thế rgin of the spestum andre moving to the is

ee These devs can {tbh they ay not) beige od ight cable Ts low cost and ease of ase ake ul Iber experiments ite fale, and ere import

‘clases allom laboratories ith ied resource ttl be lnvolved ia state-oFtbeart™ lseratec phys expe tren These ince he ares cf aser ooting ad tang,

‘onliner opti sn high pression speseosopy ACKNOWLEDGMENTS

‘The authors acknowladge valle dcwstons with and coutrbutoas made by Caparo 3.L- Mal © Ti, V1 Welchansi, M-Obse, Robison Re Dralioger Holst, K Gil W Swann, C Tanaer B- Masterson, Seskoand R Wats Reader can obama copy fe ree rot nlading the es of the ies by comtating the ILA Publcatons Ofte € Wiesan i pleased toacknow

ge suppor this work rom the Mice of Naval Resa fun the National Science Foundation through he Univers:

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N26

High-Sensitivity Spectroscopy with Diode Lasers

RW Fox, H.G Robinson! A 8 ZibovN Mackie J Maruard

1 Magyar, LW, Halberg, Ngienl IneBbte of Standards and Tecnology

"25 Broadway, Boalt, CO 80305,

ABSTRACT Linewidh seduction ofan extend cas cede laser a 657 am was accomplished by negave

feetfock wan iacavity ADP crys High soto (170 Kz wide) sara absorption signals

‘wee record ofthe eleum itrombinton ine which i of interes fora frequency standard The

pect ofthe ed pe yp cei Hine ina magiem-opcal cel sp was sso investigated,

LINTRODUCHON

“Te advance of diode Inter to the vse offers opportunites i the area of frequency sandals and frequency sexology Dide lee sais to known stra features hav the potential to be low ca, igh rein fone

‘markers and length sandarde Tắc calcio intrcombinain ine at 657 om sone sich feature that has generated mich

‘An opal oquency reference may in general be realized by fist rtucng the shor term laser fequeney Hctntions

by locking to Fabry-Perot cavity, tan locking te cavity waa atomic or molecular Ine This approach allows excugh

‘grate in the short tenn (21s) forthe perfomance 1o be lined by sycemaiet sesrited vi eming te

‘spcual fea, such as ld shits or dime of fight breadening A caveat ois ith the Tock wo te optical cavity mast

‘relay inmune fren oer date Ofsls may occur fo Instance, when the injcdon cureat of adds system is

‘modulated produce sidhands fer ar hero lock Se fraction of the inherent aspbitademosaatin (am) dete lng with te desired signal leading to an intensity dependent de term atthe ouput of the phase sensitive detector

‘Sates to deal with his nla deodlating a andor samping the ser ntensity pir othe freee envy i det

tw subst any Dactsios out of te cavity tansmision or rel<cicn However there are bath fundamental its (Witt

‘gard wo Be power hat mis be expended ie the sapling chanel) and paccal nis uch asthe lnbomogely of te fam acros the team tha il indore dit at sme level Tas of Slrest wo at wih lw eid em te

‘modulo as posse

Employing & phase modustr exemal 1 the Ise cavity to apply sideband and wo reduce te Hequencyphase vctuaons ia neo da has et with mach success.” We have poidoned he pase edule inside the extended evi, ere it serves as a Requney module In compasson a exaral mofulsicr has much lower gla a a frequency anedacr Alhough exer molpe pas cenigurons have ben ust, te poe quali of the diode ser beam takes this approach oceasingly eifeuk A Gsadvanuge of placing te cry inthe laser cavity the coupling ofthe tpt

‘power tote fequeney motion (fn), albeit at moc lower eel han dict ijn creat modalaon However the Injen creat chanel snow aval o be part ofa hse loop rites con wih servo badwidh independent the fequeny convo oop Ifthe intensity col loop bandwith i code to cover the fm sidehand fequeey te

‘residual am oi siheqgen de lock dif wil be fare cree Similar mpreaches wring negative feedback oexteally pliced modulating crystal eliminate resale worked wel

2 LASER FREQUENCY NOISE AND LINEWIDTH REDUCTION The exended cavity lst consisted of an ani efleton coed ed ode ase rding e đi n, a 1 climaing Jens, 3 29 9m Jong Brewster-cut ADP riiultr crys and high diffraction efficiency hologapic grating” Ths ks seas ul on a near baseplat nd enclose nan aim box w russ acoustics The grag Nas mound on an inva

Comribaion f MISE, not subject eopyighe Pro SI Conference on Frequency Lasers tr Applications, 137 (tted by V.C- Chung pp 360-865 (1992)

1™N27

sory with a simple Hinge anda piezosatic gp

Cap alowingsboa 12‘Ghe í ting voi

tuệ lược Tế secre Yieteikcedren anima mmencipereieir bean ơn tt prkbg 1y

{Se ping and sored Oe Soe TAS yop Cenipratn ees te cat hens ang S

`

tạ 5W, 6ợening súc leng wavelet TT

‘The spect Hiewidh of the unlocked (and 210°

locked) laser may be examined by a heterodyne Biot Ismet wis 5a mae sae ar Se bed online ie baling wo

comlee ươm, the Inorlh nay sa te

Sud by Chewing the re» Eenetey nase

Scrum Ths poner inmate

TRO dtbatin and magne of eg

{Raney fstton tat gree be neviet

‘eae gctomconfemcrae inkgndot ol cv at 9 rimince by wn ygp 7

with a low bandwidth (1 Hz) side-lock ‘Frequency (Hz)

Convene” crcl it ‘rd fei fae Fit Theta! nated cry le egy ies To ne Sinema quency Tueuaiox' bewecn te ce Se acimner cy ape

iar an cvty os sry mere ý

Iensy cuts 1, ek abot 0 ls facts ease obliging Bene deny saab “he 1 sexed cviy bog een a measured egy mie rel of sroincel #00 He ei

of nc acon peae te entire teat esta esas of prlng eet Te egy

no ai was ken wih Se Meow mina cv r tưenieim, Tắc hư te Gy aot (Cb obo a te nsing ha ee te neseesmrt to loz cam ri bom 40 cake The ot tg one eel pare ct ney scion at x aes 90 Me At sae 2

50 kts nd 30 Me iicats an nretLrenin et novi tout 2 HỰ th i0) Âm), TH Asia den ye ow Feu nase

KH“ compfe mlaleey Hư of Ủe bec

linewidth This is a consquence of the fast

frequency nose level, H,, and the coresponing

fnteprted phase noise "For 8 white fm mise

specu, the phase eoiseinteraal” beyend à

sen arbirry Bequeney fh itegaled Em £

to infinity, & HỰC Now that sigificat

Eeaurbutions to the laser lnewidh appete ony

‘when de ineratel pase noise dens apprcaches

Trad ‘The meatired nase level dats he

{nigrtd phase Mactations above 10)1H egn

the omer of HYI-O2, Therfore we expect A

Sharp reduction ‘of the Hew whea the oie

below 100 KHz is reduced, ia conuast 10 th

Siuation of a solitary dine laser where the

feequeny noise inthe MHz range is import

Tuning A coaventonl rf batodyne set-up" Frequency (Hz)

[roved the err signal a shown in Bgure 2, Fig 3 Toe elocka md eka enor signa of te mize The aise era vie po el with an ioe esemen 4

fase (ADP) lop had approximately 808 of gan tel 100 He, which was he leaf with double-ple and single pole sections to unity gain feqpency of ~1 Nils Compasation was made fr de lock-caviy hss Shit and sch of he

‘syste high-vlage divers phase sis The handwith and consquenly the atime low-tequeny gain wer: ante by

‘heres uncompensated pase shi of he igh wage deer Higher eqeency Cacatons could be cameted by using

2 low-voage higher bandwidth feedhck path tothe other se of the ery,

saturation speewesopy exving 3 pW incident co

(he detest used forthe Teck channel This

insides power wae jist slfisent 10 allow

itensiy noise limited operation, The 1 Mz

{ani allowed enough low fequecy gin 10

Jan this lũng hole ñoœ om te Taser at

‘Hequeeies below 10 HP

“The ADP crysal tnser function was 078

[Mtv The crys was bonded on ote side 10

4 cermic mount and aenustaly daned le

Telee peeo-detiE ngơnaree in ủe 99 My 72 |

‘rage The modulation troqueacy was chosen © TỐ

‘be well hove the cavity Bandwidth fo produce a L L

Intensity Noise Level

salable syaesizer power, the cyst was

‘ven as a series Wogan LC cit athe Fi 4 Te std exe ery lar fgnecy nie estan The da Imotultion frequency Q's of aboot 10 ycked Ws one wh «30 KB nevi Cea ae

TN-29