upconversion fiber laser ppts

7/27/2019 Upconversion Fiber Laser Ppts

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Compact blue/green solid state lasersfor the OEM marketplace

David PiehlerHarmonic Lightwaves, Santa Clara, California

Talk SS6.1IEEE/LEOS 1994 Annual MeetingBoston, 3 November


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Outline The air-cooled argon laser The OEM marketplace Summary of compact blue/green solid state laser technologies Commercial systems

- Frequency doubled diode pumped Nd:crystal lasers- Directly doubled diode laser

Emerging technologies- Frequency-doubled microchip lasers- Frequency doubling in quasi-phase-matching waveguides- Upconversion fiber lasers

Summary


3/83

The OEM market for air-cooled argon lasersMajor market segments ($40-50M in annual sales) biotechnology graphic arts semiconductor inspection confocal microscopyPotential markets for INEXPENSIVE compact blue/green lasers: optical storage displays pointing


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Biotechnology - DNA sequencing / gel electrophoresis Fluorescing dye molecules replace radioactive tags/photographic film One laser (- 20 mW argon) can excite several different dyes Fast, high volume sequencing High startup costs ($100K) relative to photographic film Laser wavelengths are matched to the dye chemistry Laser is the most expensive single component An INEXPENSIVE, compact laser could increase markets Drive to develop red dyes

-inexpensive red laser diodes-lower background (autofluorescence)-more compatible with solid state detectors


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Biotechnology - Flow cytometery Laser light scatters of individual white blood cells in a flowing jet Fluorescent dyes used for selective tagging of cells Analysis of scattrerd light (angle, polarization, fluorescence) from each

individual cell Machines are mainly used for research, cell sorting, moving into clinical

enviornments Scientific users want 488 nm light because there is a great body of literature

on the subject Single use machines have been developed - e.g. AIDS diagnosis Autofluorescence is a problem; using green lasers (532,543 nm ) offer 5 X

increase sensitivity Move to red dyes


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The OEM marketplace When laser is highest cost component in system, inconvenience of air-cooled

argon lasers will be tolerated (Flow cytometry (research), DNA sequencing) When systems are costly (graphic arts, semiconductor inspection), want the

highest performing laser. Everyone is sensitive to wavelength Everyone would like to use diode lasers directly - 18 months of development time before OEM brings product to market OEM users have different requirements than scientific users

- Repeatability- Beam quality, noise, pointing stability in adverse environments


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blue laserdiodes

bulk, rare-earthdoped crystallaser

SOLID STATE BLUE /GREEN LASERTECHNOLOGY

wavelength :j:::j!conversion

waveguidegeometry

waveguide laser on arare-earth dopedcrystal substrate

DPSSL+ laserdiode sources

intra-cavitySHG external cavityresonant SHG


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Commercial systems Most based on frequency doubled diode pumped Nd:YAG lasers. (532 nm)

l a s e r m O d e ~

laserdiode r d:YAG

mirrorHR@1064nmHT@808nm

KTP532nm

outputcouplerHR@1064nmHT@532nm


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"Green Problem" Sum frequency generation between adjacent longitudinal modes is chaotic Make laser single frequency to solve problem. Single frequency solutions:

- Twisted mode cavity

- Ring laser( C 0 rev'\t )

- External ring resonatorPumpDiode

KTP 532 nm

Nd:YAG ~ Rotator Plate


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Directly doubled diode laser

Isolator

860 nm

Resonant doubler

KNb03

SingleFrequencyDiode Laser

430 nm


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Emerging technologies Frequency-doubled microchip lasers Frequency doubling in quasi-phase-matching waveguides Upconversion fiber lasers


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CLEO 194-

An Ultra-compact, Laser-diode-array-pumped,Nd:YV04/KTP, Frequency-doubled,Comp,osite-material Microchip LaserN. MacKinnon, B. D. Sinclair and W. Sibbett,

University of St. Andrews, St. Andrews,Fjfe, KY16 9SS ,Scotland

S. N. Jenny and 1. T. Jenks,'",l. E. Optomech Ltd.,Newnham,Northants, NNII 6ET,England

D. Craven and D. Piehler,Uniphasc Corp.,San Jose,

Ca ., 9S] 34


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Composite Material Microchip Laser Structureand Longitudinal Excitation Scheme

0.5 mm thick Vanadate

Laser DiodeArray

Fluid Interface

2 mil l thick KTP

Green Output

Dielectric Mirrors


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High Power Composite-Material Device.Pump source provided by 2 W laser-diode-array. (200 x 1 m active area.)Exactly the same device and coupling optics as used previously.Brightness of pump source higher than that in previous lens-coupling.130 mW of C. W. green power for 650 mW of incident pump. (200/0 conversion.)

140Filled Squares: Green Power 120 Open Squares: Fundamental Power ...100 -r---.. -

S 80 - -. .-/ -; ) 060 0 0 00 0p... 0040 00 20 0 n - 0 o- ~ - - - r ' - r - i If ! I ti l i i ' I -r -r- I I I I I I i l l I I i io J00 200 300 400 :')00 600 700

Incident Pump Power (mW)


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/ Far-field Intensity Cross-section of High Power DeviceIn the far-field the intensity cross-section of the output was found to beapproximately Gaussian as may be seen below.

250 m W of incident pump power(20 mWof green power)

650m W of incident plll11p power(130 mWof green power) .


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Spectral Purity of Infra-red output at 50 i l lW of GreenOutput Power.Oscillation of two axial modes in the infra-red observed using Fabry-Perot.Intensity ratio of stronger mode to weaker mode approxilnately 10 to 1.Axial modes separated by 33 GHz (one device axial mode separation).


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Intensity Stability of 50 m W of Green Output PowerMeasured by R.F. spectrum analyser and fast photodiodeTwo infra-red axial modes should, via a sum-frequency interaction, producea periodic intensity modlliation. (The "green-problem").Apparatus capable of resolving intensity modulation 65 dB below C.W. green signal.Lack of significant intensity modulation attributable to dominance of one modeover the other and possibly relatively weak coupling between the axial modes.

~ - - - - - - ~ - - : = = - = F ~ - - --T-==P -- - f--oo:=JI l ~ J L r A13L 1.1,1. --1"---1- L -- --l- --- -1-.- - r __Ji sTop i FREQ ENCY I ! i : I I .. i i11.IHHI MHz !-- . - -T-- l - - - - r - - i t -' -j- - - t- - ' fI T i . ! Ii! t I--+-----1----:-- "- - -; ---- ..--- ,--1 '--1- - - I! ,. I I I --,i i , 1 i I : I I: ! I i I I 1 ' i 'I 1 I --I T - ~ - I : - - : --:---1I , I I I ; I I I Ii- ---1---1--+----10000-1 00-+ -- oo-;----i- - + -- - -1I ! . ! : I ! j i : I. ,-: - + - -+-- -f------;--oo-t--- --iI ., I I I . .I . I, I 'I; J- ---- -j----t--t-- -r--oo - - + - - - L -, - - '- - l k l ! : ~ ~ ~- -.1--. I --- --i . --1[ --- --- -- .. ~ 1 v 1 1 f l ~ t c L . L ~ I J--1--- ~ __J__J ____I. _ ! [ ! ' ~ ~ ~ r N l ~ST9R , 3 nz ST OP 1.000 MH 7

R.F. spectrum of 50 mWgreen output up to ) MHz.Resolution bandwidth is 10 kHz_Sensitivity is 10 dB per division.


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Advantages of microchip lasers No sub-micron positioning Mature materials Passive suppression of relaxation oscillations

Disadvantages of microchip lasers One flavor - green Nonstandard laser output - 10 mrad divergence (vs. 1.2 for HeNe) Divergence varies with power No modulation


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Future directions for frequency doubled microchip lasers Other materials Other transitions (wavelengths) (4F3/2 - 41 912 , e.g. the 946 nm transition in

Nd:YAG) Higher powers (>200 mW)


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Upconversion fiber lasersUpconversion is a way of pumping visible laser transitions with infrared light.

4F 7/ 220000970 nm

4Hl 1 / 2 0.45 ms (0.001 ms)45 3/ 2,,-... 15 000- 4F9/2 0.12 ms (0.0001 ms)IEu 41 9/ 2' - - '>- 100000::::

41, , /2 7 ms (0.007 ms)lJ..JZlJ..J 41 13/ 2 9 ms (12 ms)

nm 544 nmi

r5000 970 ~ l \ A O ' f i k lsd\cO\)o 41 ,512

Best geometry is an optical waveguide which confines light to a small crosssection for a long distance. Fluoride glass hosts are prefered to silica due to a relative abundance ofmetastable laser levels. Single mode fibers have been fabricated.


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Fiber laser device

pumplaser light~

mirror 1

doped fluoride fiber

highly transmisive at Apumphigh reflector at Aupconversion

upconversionlaser light~

~ unabsorbedpump light

mirror 2:output couplerfor Aupconversion


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Room-temperature visible upconversion fiber lasers inrare-earth-doped fluoride glass

Dopant ion

HolmiumIErbium:PraseodymiumThuliumNeodV1 V1 IVlYV\.

Laser wavelengths(nm)55054$ ::

490, 520, 540, .605 or 635480

3 ~ o ) 410

Pump wavelengths(nm)645,750,890800 ot 970840 + 1020 tg,o tN/Yla )

1120590


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UNIPHASE:BT 1993:CNET 1992:BT 1991:also LANL:

Previous work: Ti:sapphire laser pumpingreen Er fiber lasers

...----. BT 1993 ~ UNIPHASE-S 15 (971 ~ ) (971 nm) . . .'- i "CNET 1992 00) .&. . . . (971 nm) 0~ 10 .& . 0Q) .& . ...(/) ... 0o

c .&. * BT 1991Q) 5 .& . 0 (801 nm)Q) ... 0- .& . **J) ... 00100 200 300 400launched pump power (mW)...

2 I-lm core, 0.31 NA (Piehler, Craven and Kwong, Compact Blue/Green Lasers '94paper CFA2.)3 I-lm core, 0.20 NA (Brierley, et al., BT Tech . J . 11, 128 (1993))5.5 I-lm core 0.18 NA (Allain, et al., Electron. Lett. 28 111 (1992))3.4 I-lm core, 0.18 NA (Whitley, et al. , Electron Lett. 27 185 (1991))paper CMK3


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High NA fiber figures of meritGain for at given incident pump power in the "high pumping" regime

0.4-0 'Q) 0 . 3:;::;:+J"G 0.2Q)6

Q) O. 1\..l;:J0>"rl4-l

LPOl a t 545 nm

L - ~ ~ ~ 1 ~ - - - - 2 ~ = = ~ 3 - - - - ~ 4 - - - - ~ 5core diameter (microns)

II\

\


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System Issues -Active noise reduction1 0 ~ ~ ~ = = ~ = = - - - - - - - - - - - - - - - - r

00 0 0 0 0 0 0 0 0 0 0

00

0-20 0 0 0 0,. 0-30 -'--------------------______ - - - - - - -1N::c:oo......

N N N::c: ::c: ::r:...:.: ...:.: ...!.


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Electronic feedback loopr;:Er' - 3 6 . 0 dBn> AT TEtl 1'J dB

~ i ~ L ..... i'\. . .... ....... : . < . 1.. .. , '" " .: . . . . . . . . . . . . . . . .... . . . . . . . : . . . . .... : . . . . .. . . :. ' " . . . .. .... . . ... .... . "

i ~ ' 1 r\G ... .. ..... .. ....... ... .... . ... .N .JG . . i' ,' . .... .. .... ': .. ....... ...... t : ' ; ' ; ' ; .... :" ....... : .... .1: : / :1 , : : \ J ~ } , . J . I 'I't>! :l/ H S8 \.;,V: ~ I ~ , ~ ~ ; ; . ; ~ ~ ; , ; \ i \ / ! . J : I t - ' N i ~ ~ . ) r ~ 0, .. : .. . . ~ I , i l ; ; ; ' ...... .. .. :. .. .... . . . "'

C F (: I : : 1 'Y' : : \ V \ ~ , " .Ct:l R;; ... . .. . .. . .. ....... . : ... " . ' i ' r / ' , 1 , ~ j ( , ~ tl.:\{iL' .. ........ .. ::":.::.::.. :":::.:::" :.::: ..... :: ..... :: ...L ..:..:........:... ' . ~ ~ v : ~ ~ ~ ~ . : " : '

without loopCEHTER :30C:O.6 kH = SPHt-1 5 8 8 . 8 i-"H::#r;:ES 1. I Hz 'JE,W 1 k H;;: ~ : W P 1. S;",,,

p (. ;:- - l; rj t11 t-\ T T (, H '1 d 8 -",-:" '1 FL . "'1\' .... .... . ........ ........ : ... ..... : ........ : ........ : . ....... : ........ : ........I

~ ~ : ~ .. .. . ..... : .. ..... ............. .. , with loopml \"",' ... ........ .. II . . . .I J,...... ; . .... . ........ : .... ....... ........ .. .. .. . .. ...... :... .t} 13 . . . . . . . , .. . . . .. .1 S I")' ...... :. .. ............:. ... ... .. .. .. .. ........ ...... .i -


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Recent Data - diode pumping(in collaboration with Tim Carrig, Los Alamos National Laboratory)17.9 mW of green laser light from InGaAs-diode-pumped fiber laserlength = 2.5 m; output coupler: R = 4% (Fresnel reflection)

- . 20e-- 10oQ" Er:fluoride upconversion fiber laser: 971-nm pump

Galileo: 1.6 micron, 0.39 NA

.... ~ ~ b.. ~ ~ b.

A green laser power ,A A A A~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ transmitted pump power

o 50 100 150 200incident InGaAs laser power (mW)


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-* ADVANTEST Q8344A Optical Spectrum Analyzer -, 1994 - 8- 27 14:05 :48SPEC P k : 0 . 5 4 3 7 2 9 ~ m 386.559pW AVG: 14/641.0nW

0.5nWO.lnW/D

O.OnW ' - - - - - ' - ~ ~ ~ ~ i ~ J d _ _ _ _ _ _ ' _ _ l ~ .~ ~ . ~ ~ \ r - ' - 'O.5415)1mAVERAGE: 11

IBlfF 120.5440)1m

AVERAGE in progress14 18 116

O.50nm / DI132O . 5 4 6 5 ~ m[ AVERAGE 1164 I

ADVANTEST Q8344A Optical Spectrum Analyzer '* 1994- 8- 27 14:10:18SPEC P k : O . 9 7 3 0 4 54.0725pW AVG : 32/64

5 0 . 0 p l ~

25.0pW5 . 0pW / D

O.OpWL-__ ____ __ __ ~ __ __ ____ __ ____ __0.9660)1mSPAN: IO.OnmIIBmI ISTART9 7 1 0 ~ m 1.00nm / D 0.9760)1m

AVERAGE in progress I [SPAN(SPEC) 1ISTOP ILldSPAN 10.4 N l.05 10 . 8N 1.75 IFULL I


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Other recent data


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Advantages of upconversion fiber lasers Highly efficient process Insensitive to pump laser wavelength, linewidth, mode hops Circular diffraction limited output defined by single mode fiber Thermal - absorption of pump light distributedDisadvantages of upconversion fiber lasers Fragile fluoride fiber No modulation Linewidth - 1 nm Output polarization drift, noise Requires sub-micron manufacturing tolerances Imperfect coupling of diode to fiber


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Future direction for upconversion fiber lasers Materials development Co-doping UV New architectures (e.g. fiber laser-pumped fiber lasers) Emerging pump diode technology (1120 nm, 640 nm diode lasers) Bragg grating mirrors


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Frequency doubling in quasi-phase-matching waveguides Waveguide geometry insures high intensity over a long interaction length

Periodically poling the ferroelectric domains in the waveguide modulates thenonlinearity.

P2CJ) I+X(2) I -x(2)

(0)o

II31c 41c Sic 61c


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Engineering the phase-matching By proper selection of the period of domain reversals, one can engineer the

phase matching wavelength. The poling period can be defined to double any wavelength within the

transparancy range of the substrate. QPM overcomes restrictions set by birefringent phase-matching

,,'",',,'", ',,'

periodic domain reversals

", ',,',,'",'

", '",'

.~ - ~ - - - - - - - . - - - - - . - .

substrate may be KTP, LiNb03, LiTa03


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QPM waveguide system Pump acceptance bandwidth is < 0.2 nm QPM wavelength varies with waveguide temperature Stable single frequency diode required

QPM waveguide. -H-______ frequencydoubled~ - 4 _ _ output


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Frequency locking laser diode with optical feedback Use periodic domain inversions as a Bragg mirror: adjust temperature such

that AS ragg = phase-matching 867. 2 r - - . . . . , . . - r - - . . . . , . . ~ r - - . . . . , . . . ~ r - - .. . 851 . 6E 867 0.s

.r::.Cl 866 8c> 866. 6'"a: 86 6. 4OJCl

- - ~ ..

E851 . 4 .s851.2 1< \ k.... L ~ L 1

r ' >8 51 . 0 '"

85 0. 8 c..o

Use diffraction grating (IBM) 86 6 . 2 i . - . . . ! ---- '" ' --- ' ---- ' i . ...--: -- - - '_ . . . I 85 0 . 65 10 15 20 25 3 0Temperature (OC)

R-O.l% WaveplateR-90% (1J2)~ : .......... I1:::1 IZjW'l! , J1 0

DichroicBeamsplitter

KTP Waveguide R- O.2% // 425 nm

Output.......... ~ ~ ~r-tO:, ~ ,.O0GaAlAs , :SQW-GRINSCH : / L--___Laser Diode Circulariz ingPrism Pair

(3x)

R- O.2%

FIG. 1. Experimental configuration of the extended-cavity laser using abulk diffraction grating for feedback.

35 4 0


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Best Results (TMoo ~ TMoo)

cbrein invasi01V\a\Ie9lide

p-ctile

P ( ~ / P ( v 0

LnarrelizejeffidffOJ

littium riobateYara:Ia, a aI

SmyE-field @ roon terrp

~ - f - - - - -~ ~ : : ~ . +- -7 ' - =:;::

,,/ /- /// / / ,-// / // ,/ '17 rrW/170 rrW

3nm680 o/d'NarQ

littium tartalate KTPMiZLJCd1i, a aI Eger, etal

Matsushita ~ N R Cp-d01 exc:ha1ge+heat Ba/Rb

a1nea1ed pdoo excha1ge II~ ~ _ ~~ - - - = - - = - = ~ : . : . - . : . - --=-==-. [22 iZl Izl23rrW/121 rrW 3rrW/52rrW

10nm 3.8nm1fi1OfcNVarQ 800 o/d'N arQ


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Advantages of QPM waveguides Access to arbitrary wavelengths Use of large nonlinear coefficeints (d 33) single pass, no resonator Polarized, diffraction limited output Single frequency outputDisadvantages of QPM waveguides Diode must be frequency stabilized, single frequency Power limited to 20 -30 mW Requires sub-micron manufacturing tolerances Coupling diode to waveguide (diode is TE, waveguide wants TM)


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Future direction for QPM waveguides Consistency in waveguide processing* E-field poling Increasing acceptance bandwidth at the expense of efficiency Modulation Stable manufacturable architecture* Infrared - DFG, OPOs etc

*Uniphase received $1.5M Department of Commere Advanced TechnologyAward (21 Oct 94)


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Summary of wavelengths

?

400 nm 450 nm 500 nm

Tm fiber laserPr fiber laserEr fiber laserHo fiber laserFrequency doubled Nd:crystal laser (-1060 nm)Frequency doubled Nd:crystal laser (-973 nm)Nd:YAG + KTP SFGBulk frequency doubling KNb03 + AIGaAsBulk frequency doubling KNb03 + InGaAs

QPM doubling (InGaAs)QPM doubling (AIGaAs)

550 nm


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Summary

For compact solid state blue/green lasers to impact the marketplace: Prices must fall A reliable blue laser must be developed Wavelengths must be compatible with chemistry Laser developers must beat synthetic chemists


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Acknowledgmentsupconversion fiber lasers Dawn Craven (Lambda-Physik), Tom Waska(consultant), Herman

Ferier( consultant)

frequency doubled microchip lasers Neil MacKinnon (University of St.Andrews, IE Optomech) , Dawn Craven(Lambda-Physik), Simon Jenny (IE Optomech), Ian Jenks(IE Optomech), BobJones (Uniphase)

QPM wave guides Eric Lim (Uniphase), Suzanne Lau (Uniphase)


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InGaAs-LASER-PUMPED GREENUPCONVERSION FIBER LASER

David Piehler and Dawn CravenApplied Photonics Division

Uniphase Corporation

presented at CLEO'94Anaheim, CaliforniaMonday, 9 May 1994paper CMK4

San Jose, California


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Motivation

Previous work > 11 mW operation of diode pumped green upconversion fiber laser Noise reduction

Warm-up effect Packaging


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Motivation for this workCompact source of blue/green light.

Upconversion fiber lasers: No phase-matching Efficient (with respect to coupled pump power) Wide wavelength acceptance bands Circular, diffraction limited outputTechnical challenge: PUMP SOURCE Ion lasers Ti:sapphire lasers Diode laser pumped Nd:YAG lasers (1120 nm) Diode lasers Other fiber lasers (paper CM K6)

Diode lasers are the best choice for near term realization of a compact device.


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Dopant ion

Holmium[ ~ : t : ~ I Q ) j j :::: :::::::::: ::::::

Laser wavelengths(nm)550545

Praseodymium 490, 520, 540, 605 or 635Thulium 480

Pump wavelengths(nm)645,750,890

: :: ?9.9 9?,Q840 + 1020

1120


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Energy levels of Er3+ in fluoride glass(including room-temperature lifetimes)544 nmESA j:,

- - - -6------:1,-;\, ) - I - ~ _ S _ O _1_n_m_p_u_m_p

971 nm pump I- - -+--....... 1

1l--+-.. -0-1-n-m-p-um-p"1'

l::- ... ~ ~ - ....-I---.......----544 nm, laser SO 1 nm pump971 nm pump

4F 5/2

4F 7/ 2;Hl1l25312

4F9/2

4/9/2

4/11/2

4/ 13/2

4/ 15/2

(0.45 ms)(0.12ms)

(7 ms)(9 ms)


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UNIPHASE:BT 1993:CNET 1992:BT 1991:also LANL:

Previous work: Ti:sapphire laser pumpingTi:sa reen Er fiber lasers20

*--.. BT 1993 ~ UNIPHASE-S 15 (971 nm) *971 1)&1)'- " ;-CNET 1992 00) 3: .& . * (971 nm) 0~ 10 .& . 0Q) .& . *n * 0Oc .& . * BT 1991Q) 5 .& . 0 (801 nm)Q) * 0'- .& . **>

**0

0 100 200 300 400launched pump power (mW)

2 Ilm core, 0.31 NA (Piehler, Craven and Kwong, Compact Blue/Green Lasers '94paper CFA2.)3 Ilm core, 0.20 NA (Brierley, et a/., BT Tech. J. 11, 128 (1993))5.5 J.1m core 0.18 NA (Allain, et a/., Electron. Lett. 28 111 (1992))3.4 Ilm core, 0.18 NA (Whitley, et a/., Electron Lett. 27 185 (1991))paper CMK3


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Previous work: diode pumping

An Ortel 40 mW fiber pigtailed EDFA pump module operating at 971 nmpumped a Er fiber laser with an R = 58% @ 544 nm output coupler: I threshold: "'21 mW (w.r.t.c.p.) slope efficiency: "'25% (w.r.t.c.p.) 2.5 mW of green light generated from "'31 mW of coupled pump light

(Piehler, Craven and Kwong, Compact Blue/Green Lasers '94 paper CFA2.)AlsoMassicott, et al., Electron. Lett. 29, 2119 (1993)

A 1.1 Ilm core, 0.4 NA (k = 600 nm) Er fibre laser generated 3 mW of greenlight from 40 mW of coupled 800 nm diode pump light.(R= 4%, threshold'" 15 mW, slope efficiency'" 12%)


49/83

Fiber

Pump

This work:1.5 mength:material:dopant: fluorozirconate glass (Le Verre Fluore)1000 ppm Er3+

core diameter:cutoff wavelength:numerical aperture:2.1 ~ m830 nm0.31

SDL-6321 InGaAs laser diodesingle spatial mode (1 ~ m x 3 ~ m emitter)971 nmdelivers 150 mW from 230 mW of applied current

laserdiode

quarter-wave plate erbium dopedfluoride fiber

highreflectormIrror

outputcouplermirror

544nm


50/83

Results

Laser diode pumped Er fiber laser:R=900/0/R=71 0/012

~ 1 0E::-8:::J0 .

........:::Jo 6Q)encoc 4Q)Q)0>2

75

100 125 150 175 200 225InGaAs laser diode current (mA)


51/83

Assuming (1) 35% coupling efficiency,(2) When coupled to fiber laser LD power increases by '" 10 %For an R = 71 % @ 544 nm output coupler

threshold: "'18 mW (w.r.t.c.p.) slope efficiency: "'25% (w.r.t.c.p.) 11.7 mW of green light generated from "'58 mW of coupled 971 nm pump

light. 2.7% wall-plug efficiency.


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Noise ReductionTransfer function for Er upconversion fiber laser as a function of pumpmodulation frequency

-" - IB ' 5 J 1US---OISER-r-ZH+H-H+HI Dale 01-07-94 Tesled by__30dB

IN - - - - PHASE - - - - PLOT OF 2/ 1

+ 20dB I - l - I + H H ~ I

+ 10dB I - l - l - I - I - ~ I I

- IOdO 1H-HIHItH

- 2 0dB I - + + + r ~ \ - \ \ \ ~ \ T \ m

- 30d8

- 40d B LLLLJ.. l l l lLULWi l l l l l

+ 180

+ 120

+60

O

-60

- 120

- 180


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Electronic feedback loop,rREF - 3 6 . 0 dBm ATTEN 18 dB

~ i : L .:: ...i'l -:_ :-- : - T - : T_ : - : - : I.. . .. . -, . " .. . . . . .. .. . .. . .. . : . .. .. ... : . .. .. .: ... . . . .. : .. .. . . . . . . . . .. ..... . .... .i 1I! G . . . . . . . . . ; .. . .. .. : .... . . . . . . .. . . . . : .. . . . . . G ./ . ... .. . . . ':' . . '. :" ':1 . \ ~ ~ , . ~ " . ~ . ':' ... .. : ...... . .... .. :. .. ....

!:1 S B \,;,\" " ' ; .. ~ , : ; . ~ ~ ~ ~ ; \ i ! \ ; \ \ \ / 1 . ~ I ~ ' \ \ l i ; t ) ~ \ ( ~ ~ , . , .. : ... t ~ I , ~ ; \ ~ ; ...:. ......: .. ..... .. ..... with 0 ut loopI) g......... : . . . . . . I ' . . . . . .. : . . . . . . ... :. . . . . . .. : .. .. Ii. ' \ " ~ ' I \ ; " ' , j ) i i ' ; , i ~ ' ~ ~ ' ~ ~ ' .. ' . .. .. 1

..... ... : .. ..... . .. .... ... : .. . .. .. . ....... . ... .. ... : ........ :. . " .... : . ... y \ ; .. 0 V ' f l " : 1: ; : : : : : I--- ----- .: .. - .. . . :.-- . . . . . . : .. .. . --.: .... -. .. :.----- .. . : .. .... . -.: .. - . . . . . . - ... . . .. : . . . . . . . .C E ~ I T E R :3 ' )0 .6 kH = SP;'tH S60 . 8 kH =1I';:E8 8W 1.0 ':H:;: 'J8W 1 kH z ~ ; W P 1 .S .;.;>.::

19153:32 Frs o J 1994P E , - :) c;. '" d AT T E f\ '1>1 d I=)-3 '1 FL'' ' ' ' ' 1\: .. .. .. :"--'-- --: .------ .. -- ....... ........ .. ---- ... .... ..... ;--. -- .. --; .. --.-- --


54/83

"Warm-up" effectdiode pumped Er fiber warm up

1-- 0.5~ E-.......-.... 0.2Q)

0.1a......5. 0.05.....:::l0c 0.02Q)~ 0.01

0 5 10 15 20 25 30minutes after turn-on

Highly dependent on pump power and fiber laser cavity loss Once warm, fiber stays warm for hours. "hand-waving" solution Problem eliminated by using a low-loss cavity design.


55/83

Packaging Entire fiber laser (pump diode, fiber, mirrors, collimator) put into 12x12x4 cm

package. Package generates 4 mW of green laser light. Package size will ultimately be determined by fiber bend radius 2.5 cm).


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Summary Over 11 mW of 544 nm laser light generated from a 150 mW 971 nm InGaAs

diode laser via an upconversion fiber laser. (2.7% wall-plug efficiency.) Amplitude noise reduced electronically by 10 dB (0.3% rms) Warm-up problem eliminated by use of low loss cavity. A 4 mW green upconversion fiber laser operated in a compact 575 cm3

package.


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GREEN LASER-DIODE-PUMPEDERBIUM FIBER LASER

David Piehler and Dawn CravenApplied Photonics Division

Uniphase CorporationSan Jose, CaliforniaNorman Kwongartel Corporation

Alhambra, California

presented at Compact Blue/Green LasersSalt Lake City, UtahFriday, 11 February 1994paper CFA2


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Dopant ion

Holmium

Laser wavelengths(nm)550

Pump wavelengths(nm)645,750,890

[ E r b 1 ~ ~ : : : : :: :::: :::: ::::: ::::::: ::::::::::::::: :::::$45: ::::::::::::::: ::: : : : : : : : : : : : : : : : - - 8 0 ( f : ~ 7 Q :::: IPraseodymium 490,520,540,605 or 635 840 + 1020Thulium 480 1120


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Energy leyels of Er3+ in fluoride glass(including room-temperature lifetimes)544 nmESA ~ --6__- - - -

- - -A-j ------;/--t------ - - ; ; ; ; ~ = ; p ; ; ) - - ; ; ; ; ; ; ; ~ ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; =- '::-j!J:971 nm pump- - + - - ~ - - - ~ - - - - - - - -

- - ~ ) ~ - - - - - . ~ - ____.-______

4F 5/2J 801 nm pump4F 712

" !Hl1l253/2801 nm pump 4F9/2

4/9/24/11/2

971 nm pump 544 nm, ~ I a s e r 801 nm pump4/15/2

(0.45 ms)(0.12 ms)(7 ms)(9 ms)


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Population dynamicsRate equation model of 100 mW of 970 nm incident on an Er fiber

with core of 2 Jlm

c 0.5o~ 0.4::Ja.o0.. 0.3coc.Q 0.2t5LL 0.1

5 10 15time after turn-on (ms)

The long lived 4113/2 level acts as an excitation sink


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Fiber

Pump

The erbium fiber laserlength:material:dopant:core diameter:cutoff wavelength:numerical aperture:Ti :sapphire laserorInGaAs laser diodeOrtel Corporation

2.2 mfluorozirconate glass (Le Verre Fluore)1000 ppm Er3+2 Jlm800 nm0.31

EDFA pump module in 14-pin butterfly packagepigtailed to Flexcore 1060 fiber


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Ti:sapph ,re laser pumping

outputcoyplermUTor

..Q) 16.014.012.0

:; ~ 10.00.3:'5 E 8. 0o _ 6. 0

oa.

0.0

Er fiber lasel- - -R=

23 %

20.0 40.0 60.0 80.0

using an external mirror cavity launched 970 nm power (mW)

Er fiber laser --0---- R = 90% with.. lasingQ)

60.00 ~ R = 23% witha. ...... lasing-03: 40.0Q) Ec.. - 20.0 .................... - .:8--0.- ----0--- R = 90% without0f/) _ ~ i r - ~ . lasing.c 0. 0S .

0. 0 20.0 40.0 60.0 , 80.0 --- . . --- R = 23% withoutlaunched 970 nm power (mW) lasing


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971 nm Ti:sapphire pumping resultsWith an R = 23% @ 544 nm output coupler:

Threshold: 31 mW (with respect to coupled power) Slope efficiency: 51 % (w.r.t.c.p.)l ~ 1_ mW of green laser light generated from 59 mW of coupled power -9 nm pump acceptance bandwidth (FWHM) centered at 971 nm (R=90% ;

25 mW launched)

this work:BT 1993:CNET 1992:BT 1991:

Ti:sa20...

...--.. BT 1993 ~ this work.s 15 (971 ~ ) (971 nm) ..."- ' ;CNET 1992 00) &. . . . (971 nm) 0~ 10 &. 0Q) .&.. ...CJ) ... 0u .& . BT 1991c ...Q) 5 &. ... 0 (801 nm)Q) 0"- .& . ...">

..."0

0 100 200 300 400launched pump power (mW)

2 )lm core, 0.31 NA3 )lm core, 0.20 NA (Brierley, et al., BT Tech. J. 11, 128 (1993))5.5 )lm core 0.18 NA (Allain, et al., Electron. Lett. 28 111 (1992))3.4)lm core, 0.18 NA (Whitley, et al., Electron Lett. 27 185 (1991))


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EDFAlaser diodepump module971 nm

Laser diode pumpingmode-matchinglenses

fiber pigtail

erbium dopedfluoride fiber

highreflectormUTor

. coupling efficiency is about 50%

544nm

r.:-.:. . . : ,, I11II i ~ p! ' 1 I I I!,! I ij,lI j'n! llH- ;t t 1 ~ Jl


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ti II I ' ~ l l . U . l . 9 l l ! . . L . L 8 o n m ! . . L l . . ! . . L L a s ~ 9 r" '---"!.I ..:..!..!.!.1!.!.!.!J..1 l..I.ll.1.! I I Il1jl tilll\l! iiI! Ifl1-'ill : tllii 11I1: -J l l l l l l l l l l l l l l l l l f l lTl l fnnnnrn P I " ""u" .. I ! !l1[t nIT

1.11 t t t t tHtHtt l t l t TEC : t r(+) .. , Ii ." 1 dillIliii il ~ o ~ 1 0 ~ f ; ~ ' : L D ( ~ L G , o ' " d . WiUu 6 : I "TI 11111! I \ 0 ,', L O ~ ' ~ ; " G ' O ' " d 11 IIttl mH 1+tlt t tHWHtt l "' 11 nlermlslor I'; 12 NC j Itt,i IiI 13 NC I ./ '1I 14 TE Cooler(.)+0 - It i! ! . . . I : - - - ' - - ' - - < ' : " : : ' ~ - ' - - - - - - l I II~ t 1 ~ 1 111111111111111 1-11111111111111111 111111111111111 1111111111111111111 11111111111111111111111111111111111111 . . II II.,. I 111111111111 1 1 - I - I 1 I 1 + 1 1 I 1 1 ~ l n H ~ I H " I l m " H H ~ I J U H U + I H l + J . i ~ I - H I l I U + l f l . l 1 I 1 J 1 1 1 1 I H 111"111111i \; TIl'""!~ inl!j I

. , I-II' - '\ I; , ii , ( ~ t I III" !I : I Ii!: : I2. 0 ;1; ii.! I:i! rl I I I. . .. 'r "

~ ! ' l l . l fiT II II' ,'. i, tT1 111 III I] f 11' i II,.II I,l "IIIJ 1,,'11'\l: :1' lji dl ' . . If Ililli ! 111 pi"''1::- ;m11 I I ; l ~ ! ! III fji Wi-. W I I r III til!1 tJlU. IW iii I I I . I f m ~ 1 , 1 [ ~ l i

40Ze o

,I, 0 ,40 ~ 12020 lb o

C U ~ f ! . 8 U T (fI1AJ C u ~ R E t - J - r ( r > 1 t 4 )TlST 9v


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Diode pumped results EDFA module cooled to "'10C to operate at "'971 nm. Approximately 500/0 of module light couples to fiber laser. Data are given in terms of applied current to the laser diode. Laser diode + fiber laser can form coupled laser cavities. LD monitor photodiode reads about 100/0 higher when coupled to fiber.

~ E 2.5---Ec 2~ ~to(tj 1.5L-a>

1a.......::J.8- 0.5::Jo

50

:IR = 58% II-

100 150laser diode current (rnA)


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Related resultsAssuming (1) 50% coupling efficiency,

(2) When coupled to fiber laser LD power increases by '" 10 %For an R = 58% @ 544 nm output coupler

threshold: "'21 mW (w.r.t.c.p.) slope efficiency: "'24% (w.r. t.c.p.) 2.5 mW of green light generated from "'31 mW of coupled 971 nm pump lightIn comparison:At BT Laboratories (Massicott, et al., Electron. Lett. 29, 2119 (1993)),a 1.1 J.lm core, 0.4 NA (Ac = 600 nm) Er fibre laser generated3 mW of green light from 40 mW of coupled 800 nm pump lightfrom an AIGaAs laser diode.


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"Warm-up" effectdiode pumped Er fiber warm up

1.--.. 0.5 .3:E--.. 0.2Q)

0.1a.+oJi1. 0.05S0c 0.02Q)~ 0.01

0 5 10 15 20 25 30minutes after turn-on

Highly dependent on pump power and fiber laser cavity loss Once warm, fiber stays warm for hours. "hand-waving" solution


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Summary Upconversion-pumped Er fiber lasers are capable of greater than 50% IR to

green efficiency. 2.5 mW of 544 nm light generated from a "40-mW" EDFA module. Results can be scaled to higher power: Doubling the diode pump power

should increase the green output to over 10 mW.


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LASER DIODE PUMPED VISIBLEUPCONVERSION FIBER LASER

presented at CLEOBaltimore, MarylandThursday, 7 May 1993paper CThC3

David Piehler and Dawn CravenUniphase CorporationSan Jose, California

Norman Kwong and Hal ZaremOrtel Corporation

Alhambra, California


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Upconversion Laser History1971 HolYb:BaY2Fa 554 nm 77K IR flashlamp Bell Labs1985 Er:YAI03 550 nm 77K two I R dye lasers IBM1990 Er:YLiF4 551 nm 90K diode laser (800 nm) IBM1990 Tm:fluoride fiber 480 nm 77K Kr+ laser (647 +677 nm) CNET455 nm1991 PrIYb:fluoride fiber 635 nm RT Ti:Sapphire (855 nm) CNET1990 Ho:fluoride fiber 550 nm RT Kr+ laser (647 nm) CNET1991 Pr:fluoride fiber 491 nm RT Ti :Sapphire Southampton/BT520 nm (835 nm + 1010 nm)605 nm635 nm1991 Er:fluoride fiber 544 nm RT Ti:Sapphire (801 nm) BT1992 Tm:BaYbYFa 647 nm RT 800 nm diode laser Amoco1992 Tm:fluoride fiber 480 nm RT Nd:YAG (1.12 J.lm) Amoco


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Q: Why Fiber Lasers?A: Geometry

Both pump and laser light are confined to small (''In(2 J.lm)2) area over a long('" 1 m) interaction length. Efficient laser action. Efficient upconversion processes.Best results for practical (room temperature, diode laser pump-able)upconversion lasers use fluoride glass fibers.


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Theupconversion process- ,Sequential absorption ()f two photons with or without energy transfer.

833 nm2F 5/2

985 nm 1016 nm 1016 nm

-Pr 3+

491

3 F 23H 53 H 4

f,3SH

sal G03, . I ......


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Absorption at "- J 1 ~ m(from Ohishi, et a/., Photon. Tech. Lett., 3, 990 (1991))--- . ---E, 1 EuN NI N. I0 0~ Yb3+ (2 F7/2 - 2F5/2) Pr 3+(3H 4-'G4) < r-X 4 x '---- ---- '. +V) ~ (V )....a / ' J- .>- >- D -Uo- LI..-0 3 . 0z z0 0

J-' --o 0.5 ' 0L.U L.U .( J ) 2 U)( J ) enen en0 00 : a: Iu ( . ) .z '

1:2:0 0"t - t -... '. D-o:: . a:0 O.en 0 eneo o eo


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FiberThe Pr/Yb fiber laser

length:material:dopants:core diameter:cutoff wavelength:numerical aperture:3PO lifetime:

1 mfluorozirconate glass (Le Verre Fluore)2000 wt. ppm Pr I 4000 wt. ppm Vb4 J.lm960 nm0.2139 J.ls

Laser diodes

AIGaAs833 nm SDL-5422 150 mW single spatial mode laser diodeT = 20C.InGaAsOrtel Corporation985 nm or 1016 nm, single spatial mode,threshold = 20 mA, slope efficiency = 0.61 mW/mA, T = 20C.


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986or1016nmlaser diode

833 nmlaser diode

highreflector outputcoupler

polarizingbeamsplitter single modefluoride fiber

laser outputat either635 or 521 nm


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Mirror Reflectivities635 nm operation high reflector output coupler

635 nm 99% 77%833 nm 10% 99%1.0Jl,m 12% 99%

521 nm operation high reflector output coupler521 nm 98% 98%603 nm 35% 35%635 nm 7% 7%833 nm 4% 4%1.0 Jlm 9% 9%


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ResultsRed output power vs. laser diode power---..~ 6EE 5cL()~ 4+ - 'ctSQ; 33:o0 .2+ - ':::Ja."5 1o

833 nm laser diode constant at 112 mW

I"I

~I

1016 nm "

I"II

I"I"

JA/

985 nm

o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~20 40 60 80 100 120 140incident InGaAs diode laser power (mW)


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Red output vs. 1016 nm vs. 833 nm

833 nm AIGaAs (mW)_ - - - - - - ~ ~ 100

6,0

4.0

635 nm (mW)2.0

20o 1016 nm InGaAs (mW)


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Green output power vs. laser diode power833 nm laser diode power constant at 138 mWo - - r - " " - ' - - ' - - r- - r - " " - - - " , , - , - -, - - ' - - ' - . . .. . . . . . - r - " " " -' - - . . . . . . -T ' "' " "1r- - r - - r " - - - ' -- ' - " "T""" " "T' " " " " " "" " " ' - - . . - - - r - -r - - ' - - ' - - , - - ,

.-~ 0.7E-..-E 0.6cN O5LO10 0.4

~Q);: 0.3oa."S 0.2a.~ 6 0.1

~1016 nm I

IiJ.II,.

II

f

,IIII

/~II '

985 nm

O ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~20 40 60 80 100 120 140incident InGaAs diode laser power (mW)


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Thresholds & Slope Efficiencies(with respect to incident power)

112 mW @ 833 nm14mW@833nm

112 mW @ 833 nm32 mW @ 833 nm

138 mW @ 833 nm55 mW @ 833 nm

138 mW @ 833 nm67 mW @ 833 nm

Red (635 nm) transition8 mW @ 1016 nm

80 mW @ 1016 nm16 mW @ 985 nm90 mW @ 985 nm

10. % (@ 1016 nm)9.3 % (@ 833 nm)5.1 % (@ 985 nm)5.0 % (@ 833 nm)

Green (521 nm) transition32 mW @ 1016 nm87 mW @ 1016 nm

80 mW @ 985 nm130 mW @ 985 nm

1.5 % (@ 1016 nm)0.4 % (@ 833 nm)

0.7 % (@ 985 nm)0.4 % (@ 833 nm)


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Excitation spectrac;; 10+ - 'C:J. (a) (b)0 8C\S""-'Ec 6 f': /"" ...""" .tl.'(\ J ~ "O '"J 4 h...,/,.~ ,..Q) fa~ Ia ~a.. 2 I+ - ' ,.:Ja.. ~+ - ' I:Ja goo 850 900 950 1000

Ti:Sapphire wavelength (nm)

(a) Ti:Sapphire power = 200 mW; 985 nm diode power = 80 mW(b) Ti:Sapphire power = 120 mW; 833 nm diode power = 120 mW


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ConclusionDiode pumped upconversion fiber lasers are feasible mW power levels room for optimization: concentration, geometry, mirror reflectivityBroad pump acceptance bandwidth no "holes" minimal wavelength requirements on laser diodes insensitive to laser diode mode hops

upconversion fiber laser ppts

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