1. Laboratoire des Matériaux Avancés - Lyon
High Reflectivity
Mirrors Technology
Laurent PINARD
Scientific Director
Laboratoire des Matériaux Avancés - Lyon
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

2. OVERVIEW LMA Presentation LMA in the VIRGO collaboration
Low loss coatings : Ion Beam Sputtering
Multidielectric Mirrors for cavities
Conclusion
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

3. LMA Presentation Laboratoire des Matériaux Avancés in Lyon
UPS from IN2P3/CNRS (Unité Propre de Service) since 2004 (before IPNL)
Group of #10 engineers, 2 PhD
Specialized in the study, the realization and the characterization of thin films
realized by various deposition processes (CVD, PVD).
Low loss coatings
on large components
Cavity mirrors (DESY)
Gyrolaser
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

4. LMA Presentation
150 m2 class 1 clean room : coating machine, metrology
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

5. LMA Presentation Ion Beam Sputtering Coaters : low loss coatings
Coating Capability :  100 mm
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

6. LMA Presentation Ion Beam Sputtering Coaters : low loss coatings
“VIRGO” Coater : 2.2*2.2*2.4 m3 – Unique in Europe
Coating capability 1m with a thickness uniformity #6.10-3
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

7. LMA Presentation
Optical Characterization : Absorption (Photothermal deflection)
Maps up to 400 mm
Sensitivity at 1064 nm
0,02 ppm surface
0,1 ppm bulk
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

8. LMA Presentation Optical Characterization : Scattering/Transmission
Maps up to 400 mm
SNR # 10-9
scattering level < 1ppm
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

9. LMA Presentation Optical Characterization : Microroughness/Defects
POSIPOL Workshop 2007
Laurent Pinard
Threshold : 0.3 µm
25 mai LAL

10. LMA Presentation Optical Characterization : Wavefront
Phase shift Interferometer (150 mm)
Stitching interferometry (400 mm) : Unique
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

11. LMA in the VIRGO collaboration
End Mirror 1
Mirror HR
R= %
Interferometric gravitational
wave detector (CNRS / INFN)
3 km
Finesse 50
Mirror
Input
Mirror 1
R=88 %
A.R.
Recycling
Mirror
R<5.10-4
Beam
Splitter
3 km BS
50 kW
20 W
1 kW
R=50 %
LASER YAG:Nd3+
20 W AR AR
Mirror
R<10-3 AR
Mirror HR
Mirror
R<5.10-4
R=92 %
R<5.10-4
R= %
R=88 %
Input
Mirror 2
End
Mirror 2
1 W
DETECTOR
détecteur
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

12. LMA in the VIRGO collaboration
UHV tube : 1.2 m, mbar
Suspended mirror
Mirror towers : 10 m
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

13. LMA in the VIRGO collaboration
Diameter = 350 mm,
Thickness = 96 mm, Weight = 20 kg
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

14. Low Loss Coatings : Ion Beam SputteringAr
Targets
Quartz
Neutralizor -
Sputtering
Source
Assist +
Sputtered
Particles
Substrate
Sample Holder
(Simple rotation)
SiO2/Ta
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

15. Constructive Interferences
Multidielectric Mirrors
Quarterwave layers : maximum interference effect
Constructive Interferences
d: l/2 l/2 3l/2 3l/2 5l/2 5l/2 no
nH > no
nB < nH
nH > nB
nS < nH
air
l/2
high index
l/4
low index
l/2
high index
low index
l/2
high index
Substrate
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

16. Multidielectric Mirrors
Alternate high (H-Ta2O5) and low (L-SiO2) index 0/4 dielectric layer : (HL)x HLL
Band width : #250 nm
R > 99.9% - limited by the optical losses (T, A, S) 0
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

17. Multidielectric Mirrors
Optical Absorption
Vacuum quality (clean)
oil free pumps, cryo pumps – no water vapor, no hydrocarbon
Targets purity (> %) - Expensive
Deposition conditions (ion energy)
high atomic % Ar : higher absorption level
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

18. 1 # 1 10 #130 Multidielectric Mirrors Scattering Scattering Sources
Incident
Beam
Specular
Reflection
Transmission
Scattering Sources
Surface
Volume
Roughness
Scratches
Holes
Particles
(Dust)
Clean Environment
Inclusions
Bubbles
Dust
Scattered Light
Roughness (Å)
Scattering (ppm) 1
# 1 10
#130
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

19. Multidielectric Mirrors
Scattering - Cleanliness
Necessary to coat and manipulate the mirrors in a clean room environment
Filter
99,X
Absolute Filter
99,999 %
Filtres
Air Propre
Clean Air + +
Flux
Laminar
flux
Laminaire
Fans
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

20. Laminar Flux Turbulent Flux Multidielectric Mirrors
Scattering - Cleanliness
Laminar Flux
Turbulent Flux
Dust
Particles carried away by the recycled flux
Low probability to contaminate the sample
High Probability
to contaminate the sample
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

21. Multidielectric Mirrors
Scattering - Cleanliness
Particles counting
Scattering Map at 633 nm
47 particles (< 0,3 µm)
Scattering 0.3 ppm
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

22. Multidielectric Mirrors
Scattering - Cleanliness
Particles counting
Scattering Map at 633 nm
3000 particles de 1 µm
Scattering 7 ppm
(multiplied by 23)
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

23. Multidielectric Mirrors
Scattering - Cleanliness
1E-07
1E-06
1E-05
1E-04
100
200
300
400
500
Number of Particles . cm-2
1 µm
0,5 µm
0,2 µm
0,1 µm
B.R.D.F (sr -1 )
Substrate Level
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

24. Multidielectric Mirrors
Scattering - Cleanliness
Bad Cleaning : > 106 defects on Ø 200 mm
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

25. Multidielectric Mirrors
Scattering - Cleanliness
Good Cleaning: 30 defects on Ø 100 mm
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL

26. Multidielectric Mirrors
Main Problem for mirror users : keep the low losses level
- manipulate in clean conditions (clean room)
- never touch the surface
- good vacuum in cavities (no turbulences)
Virgo Mirror
Scattering 4 ppm
After use
Scattering 25 ppm
POSIPOL Workshop 2007
Laurent Pinard
25 mai LAL