Property variations of Laser components under vacuum conditions

M. Jupé, T. Groß, H. Mädebach, K. Starke, D. Ristau, Laser Zentrum Hannover e.V., Hannover, Germany

Thin Film TechnologyDepartment

CharacterizationDevelopment of test procedures, service for analysis devices

Process developmentOptimization of coating processes, online-process monitoring

CoatingsProduction of optical coatings following customer specifications

Process DevelopmentThermal ProcessesE-beam and boat evaporationConsulting and Implementation for industrial productionCoatings for deep-UV and vacuum-UV applications

Ion Assisted Deposition (IAD)Characterization and optimization of ion sourcesProcess monitoring and controlling Rapid manufacturing, MIR-spectral range

Ion Beam Sputtering (IBS)Low optical losses, dense layer systemHigh power edge filters, Rugate filtersPrecision IBS coating technology

CoatingsProduction of custom-requested coatings

Spectral range 130nm to 5µmSmall batch sizes, special requirements

optical performance, low lossesdamage threshold, stabilitycomplex spectral requirements

Special substrates and materialscomplex geometrieslaser and nonlinear crystals fiber and laser diode facetsspecial coating materials

Optics CharacterizationDamage threshold ISO 11254157 nm, 193 nm780 nm (ultra-short pulses), 1064 nmsingle and multiple-pulse testing

Absorptance ISO 11551355nm, 532 nm, 1064 nm, 10.6 µm

Total scattering ISO 13696157 nm, 193 nm, 633 nm, 1064 nm

Spectrophotometry ISO 15368120 – 240 nm, 190 – 3200 nm, 2.5 – 25 µm

Precise Reflectometry ISO 13697532nm, 1064 nm, 10.6 µm

Development of standard characterization procedures (DIN, CEN und ISO)

What changes?

400 500 600 700 800 900 10000,0

0,2

0,4

0,6

0,8

1,0

trans

mis

sion

Wavelength [nm]

Start p=2 mbar p=5 *10-4 mbar p=4 *10-7 mbar

Spectral behavior

9000,0

0,2

0,4

0,6

0,8

1,0

trans

mis

sion

Wavelength [nm]

Start p=2 mbar p=5 *10-4 mbar p=4 *10-7 mbar

Damage threshold(measurement according ISO11254)

•Spectral curves of a HR1064 coated in a conventional electron beam process [(HL)19H -Ta2O5/SiO2]. Thespectrum significantly shifts to shorter wavelengthunder vacuum conditions.

•Damage threshold decreases stronglyin vacuum!!!

1 10 100 10005

10

15

20

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30

35

40

45

50

AR808/1064 -Ta2O5/SiO2

BI0705/BI0605

ener

gy d

ensi

ty [J

/cm

²]number of pulses

measurement in air 50%-LIDT 0%-LIDT

measurement in vacuum 50%-LIDT 0%-LIDT

Changing of the spectral behavior

• Method: spectral photometrical measurement

in the coating plant (BBM).

• Method: spectral photometrical measurement of thermal shift in with a special heating set-up.

Comparison of the measurements

Content of water in layer

Where is the water located in the layer?

• Focus on the physical absorption(The chemical bounding of hydroxide molecules on the silica is also possible.)

Porous microstructureIncluding of water in the structureChanging of the refractive indexAbsorption in the infraredObviously, changes of the laser light resistance

Demanded of layers with a higher density of the micro-structure

1. IBS 2. IAD

Coating processes

Halogen Lamp

Ion Source

OpticalFibre

Process ControlTrigger

IBS- Coating plant•Low loss optics (laser gyro mirror)•Crystal coatings•High power (Rugate)•Shift free, water free•But: High stress

IAD- Coating plant•Water free optics for the MIR-application•Shift free•Optionally stress free•But: Contamination??? Test of different

Ion sources (APS, Lion, Denton CC105)

Results of shift measurements

1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0,01 0,1 1 10 100 1000

-0,025

-0,020

-0,015

-0,010

-0,005

0,000

BH0301

shift

pressure [mbar]

0 5000 10000 15000 20000 25000

-0,025

-0,020

-0,015

-0,010

-0,005

0,000

shift ∆λ/λ

time [s]

shift ∆λ/λ

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

10

100

1000

BH0301

pressure [mbar]

pressure [mbar]

1E-7 1E-6 1E-5 1E-4 1E-3 0,01 0,1 1 10 100 1000 10000-0,06

-0,05

-0,04

-0,03

-0,02

-0,01

0,00

Hysteresis of the AR-optics

∆λ/λ

pressure [mbar]

TiO2/SiO2 coated in the SyrusPro1100 AR1064 TiO2 ion assisted (APS) AR1064 TiO2 conventional

Vacuum shift of a HR1064 conventional

Vacuum shift of AR-coatings

SE2906_1

BC2406/BC2706

LC-115V106001

BE0301

SE2406b1

Sf0706_5

MB0105

MB2604_2

E060227

v060602

1 2 3 4 5 6 7 8 9 10 11 121E-6

1E-5

1E-4

1E-3

0,01

0,1

Vacuum shift overview

−∆λ/λ

Sample

electron beam ion assisted Ion beam sputter

•The samples have shown different behaviors during evacuation and venting.

•The vacuum shift of IBS-samples is negligible. For IAD –samples the vacuum shift depends on the Ion dose.

• Time of relaxation is in the range of 1 to 5 hours.• The relative accuracy of the measurement is 1E-3.

Thermal Shift Measurement

800 1000 1200 1400 1600 1800 2000 2200 2400 2600

0,78

0,80

0,82

0,84

0,86

0,88

0,90

0,92

0,94

0,96

Quarz with different content of OH

Tran

smis

sion

Wavelength[nm]

B C D E F G H I J K

20 30 40 50 60 70 80 90 100 110 120 130-2,5

-2,0

-1,5

-1,0

-0,5

0,0

höhereIonendosis

TiO2

ionengestützter Prozess,Ionenquelle CC-105

TiO2

konventioneller Prozess

∆λ/λ

[%]

T [°C]20 40 60 80 100 120 140 160

0,0000

0,0002

0,0004

0,0006

0,0008

0,0010

Thermal shift measurement of Sf0706

∆λ/λ

Temperature [°C]

B

•Thermal shift reveals the content of water. The results correspond withthe spectral measurements in the IR.

•Problem of thermal shift measurementis the annealing of the samples.

Damage of samples undervacuum conditions

1 10 100 10005

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45

50

AR808/1064 -Ta2O5/SiO2

BI0705/BI0605

ener

gy d

ensi

ty [J

/cm

²]

number of pulses

measurement in air 50%-LIDT 0%-LIDT

measurement in vacuum 50%-LIDT 0%-LIDT

AR- coating manufactured inan e- -beam process

In air the LIDT is stable at 20 J/cm2. In vacuum the LIDT decreases dramatically.

AR- coating manufactured in an IBS process

The damage threshold is relatively low, but environment conditions do not have an influence on the LIDT.

1 10 100 10000

10

20

30

40

50

60

70

80

90

100

AR355/532/1064 TiO2/SiO2

V060613_5 and 6

ener

gy d

ensi

ty [J

/cm

²]

number of pulses

Measurement in vacuum 50%-LIDT 0%-LIDT

Measurement in air 50%-LIDT 0%-LIDT

Damage Threshold in Air

1 10 100 10000

10

20

30

40

50

60

70

80

90

100

AR355/532/1064 Nb2O3/SiO2

V060519_0

ener

gy d

ensi

ty [J

/cm

²]

number of pulses

50%-LIDT Hinfinit 51.4 ±1.4H1on1 92.0 ±1.5

0%-LIDT Hinfinit 21.8 ±2.4H1on1 52.9 ±2.5

1 10 100 10000

10

20

30

40

50

60

IAD AR1064-Ta2O5/SiO2

Sf0106_3

ener

gy d

ensi

ty [J

/cm

²]

number of pulses

50%-LIDTHinfinit 37.0 ±1.7H1on1 60.5 ±1.8

0%-LIDTHinfinit 14.7 ±3.7H1on1 36.9 ±4.0

IBS-CoatingThe increasing LIDT can be achieved using alternative coating materials. Vacuum test are planned.

IAD:The damage threshold is in the range of e-

- beam coatings. Vacuum test are planned.

Summary

• Vacuum and thermal shift measurement have shown spectral shifts.

• Coatings of different processes were tested

• Coating properties change under vacuum conditions

1 10 100 10005

10

15

20

25

30

35

40

45

50

AR808/1064 -Ta2O5/SiO2

BI0705/BI0605

ener

gy d

ensi

ty [J

/cm

²]

number of pulses

measurement in air 50%-LIDT 0%-LIDT

measurement in vacuum 50%-LIDT 0%-LIDT

SE2906_1

BC2406/BC2706

LC-115V106001

BE0301

SE2406b1

Sf0706_5

MB0105

MB2604_2

E060227

v060602

1 2 3 4 5 6 7 8 9 10 11 121E-6

1E-5

1E-4

1E-3

0,01

0,1

Vacuum shift overview

−∆λ/λ

Sample

electron beam ion assisted Ion beam sputter

Acknowledgements

• The European Space Agency (ESA) supported the work under the contract number: 19176/05/NL/AR. Special Thanks to Denny Wernham and Yngve Lien for the valuable discussions.