Single-Crystal YAG Fiber Optics for theSingle-Crystal YAG Fiber Optics for theTransmission of High Energy Laser RadiationTransmission of High Energy Laser Radiation

Single-Crystal YAG Fiber Optics for theSingle-Crystal YAG Fiber Optics for theTransmission of High Energy Laser RadiationTransmission of High Energy Laser Radiation

B. Laustsen and J. A. HarringtonB. Laustsen and J. A. Harrington

Department of Material Science & EngineeringDepartment of Material Science & Engineering

Rutgers UniversityRutgers University

Piscataway, NJPiscataway, NJ

Web site: irfibers.rutgers.eduWeb site: irfibers.rutgers.edu

B. Laustsen and J. A. HarringtonB. Laustsen and J. A. Harrington

Department of Material Science & EngineeringDepartment of Material Science & Engineering

Rutgers UniversityRutgers University

Piscataway, NJPiscataway, NJ

Web site: irfibers.rutgers.eduWeb site: irfibers.rutgers.edu

Single-Crystal (SC) Fiber OpticsSingle-Crystal (SC) Fiber OpticsSingle-Crystal (SC) Fiber OpticsSingle-Crystal (SC) Fiber Optics

Crystalline oxides: sapphire, spinel, YAG, .…Crystalline oxides: sapphire, spinel, YAG, .… Excellent physical propertiesExcellent physical properties

High temperature:High temperature: MMpp > 2,000 > 2,000 ooCC

Very hard and inertVery hard and inert

High laser damage thresholdHigh laser damage threshold

Transmission: Visible to about 5 µmTransmission: Visible to about 5 µm Applications:Applications:

High power laser deliveryHigh power laser delivery

Non-linear fibers: LiNbONon-linear fibers: LiNbO33

Active fibersActive fibers

Crystalline oxides: sapphire, spinel, YAG, .…Crystalline oxides: sapphire, spinel, YAG, .… Excellent physical propertiesExcellent physical properties

High temperature:High temperature: MMpp > 2,000 > 2,000 ooCC

Very hard and inertVery hard and inert

High laser damage thresholdHigh laser damage threshold

Transmission: Visible to about 5 µmTransmission: Visible to about 5 µm Applications:Applications:

High power laser deliveryHigh power laser delivery

Non-linear fibers: LiNbONon-linear fibers: LiNbO33

Active fibersActive fibers

SC Sapphire FiberSC Sapphire FiberSC Sapphire FiberSC Sapphire Fiber

SC Fiber MaterialsSC Fiber MaterialsSC Fiber MaterialsSC Fiber Materials

MaterialMaterial SymbolSymbol StructureStructure MMpp,, ooCC nn @ 3 µm @ 3 µm

SapphireSapphire AlAl22OO33RhombohedralRhombohedral 20402040 1.7091.709

YAGYAG YY33AlAl55OO1212Garnet – cubicGarnet – cubic 19401940 1.7881.788

GGGGGG GdGd33GaGa55OO1212Garnet – cubicGarnet – cubic 20982098 1.9151.915

SpinelSpinel MgAlMgAl22OO44Octohedral - cubicOctohedral - cubic 21352135 1.6671.667

SC Fiber OpticsSC Fiber OpticsSC Fiber OpticsSC Fiber Optics Relatively old technologyRelatively old technology

Haggerty, MIT 1972Haggerty, MIT 1972

Bell Labs, Stanford, Univ. South Florida, Rutgers, Shasta, +…Bell Labs, Stanford, Univ. South Florida, Rutgers, Shasta, +…

Fabrication methods:Fabrication methods:LLaser aser HHeated eated PPedestal edestal GGrowth (LHPG)rowth (LHPG)

EEdge-defined dge-defined ffilm fed ilm fed ggrowth (Saphikon, Inc.)rowth (Saphikon, Inc.)

Relatively old technologyRelatively old technologyHaggerty, MIT 1972Haggerty, MIT 1972

Bell Labs, Stanford, Univ. South Florida, Rutgers, Shasta, +…Bell Labs, Stanford, Univ. South Florida, Rutgers, Shasta, +…

Fabrication methods:Fabrication methods:LLaser aser HHeated eated PPedestal edestal GGrowth (LHPG)rowth (LHPG)

EEdge-defined dge-defined ffilm fed ilm fed ggrowth (Saphikon, Inc.)rowth (Saphikon, Inc.)

EFGEFGEFGEFGLHPGLHPGLHPGLHPG

CO2 laserCO2 laser

Challenges & AdvantagesChallenges & AdvantagesChallenges & AdvantagesChallenges & Advantages

Crystal pulling ≠ glass drawingCrystal pulling ≠ glass drawing Fiber diameter control difficultFiber diameter control difficult

300 300 m ± 1.5 m ± 1.5 m (0.5%) m (0.5%)

COCO22 laser power stability laser power stability10 W ± 0.05 W (0.5%) typical10 W ± 0.05 W (0.5%) typical

Cladding difficultCladding difficult

BUTBUT Small amount of source material requiredSmall amount of source material required

SC or PC rodsSC or PC rods

Ex: LuEx: Lu22OO33

Seed: SC fiber or Pt wireSeed: SC fiber or Pt wire

Crystal pulling ≠ glass drawingCrystal pulling ≠ glass drawing Fiber diameter control difficultFiber diameter control difficult

300 300 m ± 1.5 m ± 1.5 m (0.5%) m (0.5%)

COCO22 laser power stability laser power stability10 W ± 0.05 W (0.5%) typical10 W ± 0.05 W (0.5%) typical

Cladding difficultCladding difficult

BUTBUT Small amount of source material requiredSmall amount of source material required

SC or PC rodsSC or PC rods

Ex: LuEx: Lu22OO33

Seed: SC fiber or Pt wireSeed: SC fiber or Pt wire

IR Absorption Edge for Oxide CrystalsIR Absorption Edge for Oxide CrystalsIR Absorption Edge for Oxide CrystalsIR Absorption Edge for Oxide Crystals

Bulk Loss at Key WavelengthsBulk Loss at Key WavelengthsBulk Loss at Key WavelengthsBulk Loss at Key Wavelengths

CrystalCrystal 4 µm absorption4 µm absorptiondB/mdB/m

5 µm absorption5 µm absorptiondB/mdB/m

Sapphire – AlSapphire – Al22OO33 1818 410 410 WOW!WOW!

YAG – YYAG – Y33AlAl55OO1212 5.5*5.5* 268 268 WOW!WOW!

GGG - GdGGG - Gd33GaGa55OO1212

0.5*0.5* 4646

Yttria – YYttria – Y22OO33 0.15*0.15* 2.32.3

* * Extrapolated from IR absorption edgeExtrapolated from IR absorption edge* * Extrapolated from IR absorption edgeExtrapolated from IR absorption edge

LLaser aser HHeated eated PPedestal edestal GGrowthrowthLLaser aser HHeated eated PPedestal edestal GGrowthrowth

Laser power

Source dia.

Fiber dia.

Growth rate

Atmosphere

2 - 25 W

300 - 1000 m

100 - 500 m

1 - 4 mm/min

Air, O2, HeFiberFiber

Laser MicLaser Mic

SourceSource

CO2 LaserCO2 Laser

Rutgers LHPG SystemRutgers LHPG SystemRutgers LHPG SystemRutgers LHPG System

LHPG Fiber FabricationLHPG Fiber FabricationLHPG Fiber FabricationLHPG Fiber Fabrication

Focusing mirrorFocusing mirror

FiberFiber

Source rodSource rod

Turning mirrorTurning mirror

Laser micLaser mic

Sapphire Fiber OpticsSapphire Fiber OpticsSapphire Fiber OpticsSapphire Fiber Optics

Er:YAGEr:YAG

SC Sapphire FiberSC Sapphire FiberSC Sapphire FiberSC Sapphire Fiber

Lowest loss at 3 Lowest loss at 3 mm

Longest lengthLongest length

Fiber diameterFiber diameter

Slow growthSlow growth

Polymer coatingPolymer coating

Lowest loss at 3 Lowest loss at 3 mm

Longest lengthLongest length

Fiber diameterFiber diameter

Slow growthSlow growth

Polymer coatingPolymer coating

0.4 dB/m0.4 dB/m

5 m5 m

300 ± 1.5 300 ± 1.5 mm

1 m in 8 hrs1 m in 8 hrs

FEP TeflonFEP Teflon

0.4 dB/m0.4 dB/m

5 m5 m

300 ± 1.5 300 ± 1.5 mm

1 m in 8 hrs1 m in 8 hrs

FEP TeflonFEP Teflon

LHPG Growth – LabVIEW ControlLHPG Growth – LabVIEW ControlLHPG Growth – LabVIEW ControlLHPG Growth – LabVIEW Control

Diameter Variations in YAG FiberDiameter Variations in YAG FiberDiameter Variations in YAG FiberDiameter Variations in YAG Fiber

No diameter No diameter controlcontrol

No diameter No diameter controlcontrol

With diameter controlWith diameter control With diameter controlWith diameter control

CharacterizationCharacterizationCharacterizationCharacterization

Optical LossOptical Loss Optical LossOptical Loss

FTIRFTIR FTIRFTIR

Green Visible (535 nm)Green Visible (535 nm)

Red Visible (635 nm)Red Visible (635 nm)

Nd:YAG (1064 nm)Nd:YAG (1064 nm)

Er:YAG (2.94 μm)Er:YAG (2.94 μm)

Optical Measurement Set-upOptical Measurement Set-upOptical Measurement Set-upOptical Measurement Set-up

YAG Source RodYAG Source RodYAG Source RodYAG Source Rod

1 mm × 9 cm long1 mm × 9 cm long 1 mm × 9 cm long1 mm × 9 cm long

SC YAG FiberSC YAG FiberSC YAG FiberSC YAG Fiber

400 µm × 6 cm long400 µm × 6 cm long 400 µm × 6 cm long400 µm × 6 cm long

SC YAG FiberSC YAG FiberSC YAG FiberSC YAG Fiber

L = 65 cm, cutback methodL = 65 cm, cutback method Fiber non-annealedFiber non-annealed

L = 65 cm, cutback methodL = 65 cm, cutback method Fiber non-annealedFiber non-annealed

LaserLaser WavelengthWavelength Loss, dB/mLoss, dB/m

GreenGreen 535 nm535 nm 4.44.4

RedRed 635 nm635 nm 3.63.6

Nd:YAGNd:YAG 1064 nm1064 nm 1.91.9

Er:YAGEr:YAG 3.0 µm3.0 µm 1.11.1

SC YAG FiberSC YAG FiberSC YAG FiberSC YAG Fiber

L = 65 cm, cutback methodL = 65 cm, cutback method Fiber Fiber annealedannealed

L = 65 cm, cutback methodL = 65 cm, cutback method Fiber Fiber annealedannealed

LaserLaser WavelengthWavelength Loss, dB/mLoss, dB/m

GreenGreen 535 nm535 nm 1.71.7

RedRed 635 nm635 nm 1.81.8

Nd:YAGNd:YAG 1064 nm1064 nm 1.31.3

Er:YAGEr:YAG 3.0 µm3.0 µm 1.11.1

Effect of AnnealingEffect of AnnealingEffect of AnnealingEffect of Annealing

Summary and Future DirectionsSummary and Future DirectionsSummary and Future DirectionsSummary and Future Directions

SC oxide fibers - passiveSC oxide fibers - passivePotentially high laser damage thresholdPotentially high laser damage threshold

Transmission up to 5 µmTransmission up to 5 µm

Strong, robust, high temperature, inertStrong, robust, high temperature, inert

Active SC fibersActive SC fibersDoped oxide crystal source rodsDoped oxide crystal source rods

Fiber lasersFiber lasers

DifficultiesDifficultiesSo far, no proper cladSo far, no proper clad

Slow fiber growthSlow fiber growth

Cladding possibilities:Cladding possibilities: Post clad with glassPost clad with glass Core-clad preformCore-clad preform

SC oxide fibers - passiveSC oxide fibers - passivePotentially high laser damage thresholdPotentially high laser damage threshold

Transmission up to 5 µmTransmission up to 5 µm

Strong, robust, high temperature, inertStrong, robust, high temperature, inert

Active SC fibersActive SC fibersDoped oxide crystal source rodsDoped oxide crystal source rods

Fiber lasersFiber lasers

DifficultiesDifficultiesSo far, no proper cladSo far, no proper clad

Slow fiber growthSlow fiber growth

Cladding possibilities:Cladding possibilities: Post clad with glassPost clad with glass Core-clad preformCore-clad preform