Mirror Coatings for Next Generation Detector Prof. Shiuh Chao - - PowerPoint PPT Presentation

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Mirror Coatings for Next Generation Detector Prof. Shiuh Chao - - PowerPoint PPT Presentation

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Mirror Coatings for Next Generation Detector Prof. Shiuh Chao (Member of LSC) Institute of Photonics Technologies (IPT) National Tsing Hua University (NTHU) Hsinchu, Taiwan, R.O.C. The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Mirror Coatings for Next Generation Detector

  • Prof. Shiuh Chao (Member of LSC)

Institute of Photonics Technologies (IPT) National Tsing Hua University (NTHU) Hsinchu, Taiwan, R.O.C.

1 Contentsof this presentation havepartly been presented at Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physicsand LVC meeting, Mar.14,2017,Pasadena,Ca,USA (LIGO-G1700304)

The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017 • Academia Sinica (NTU campus), Taipei

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei 2

LIGO-T1400316-v4

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Noise Spectrum Dominant noise sources: Coating Brownian thermal noise Quantum noise – shot noise and radiation pressure noise

GW150914

Reducing thermal noise of the mirrorsis therefore to reduce its mechanical loss, to operate at cryogenic and go for larger beam (i.e. larger mirror) . Optically, the mirror needs to have excessively low absorption and low scattering loss to avoid effects such as thermal-lensing and phase disturbance Thermal noise for mirror:

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Challenges for coatings of future detectors

  • Lower mechanical loss (i.e. thermal

noise) -- @ room temp and cryogenic.

  • Lower optical loss – absorption and

scattering.

  • Large area uniform coating process.
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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Current coating technologies for a-LIGO

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Snipview.com

Currently for a-LIGO:

  • Fused silica substrate (34 cm in diameter 20 cm in thickness and 40 Kg )
  • Ta2O5-TiO2 mixed film for high index layer, and SiO2film for low index layer

coatings

Current mirror coatings for a-LIGO -- material

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Current mirror coatings – deposition method Ion Beam Sputter (IBS)

http://www.reoinc.com/

Production type IBS at LMAà Two aLIGO mirrors are coated simutaneously with planetary rotation and masking to ensure the thickness uniformity (all Zernike poly terms <0.5nm was achieved for a-LIGO)

But, need to scale-up to larger area coatings for future detectors.

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Mirror Substrate

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Cryogenic loss leak for IBS SiO2 films at different annealing temperatures.

  • R. Robie et al., “Brief update of crygoenic coating mechanical loss measurements at the University of

Glasgow”, LIGO document:LIGO-G1601854 (2016)

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Cryogenic loss peak of Ta2O5 and Ta2O5-TiO2 films

I W Martin et al., “Comparison of the temperature dependence of the mechanical dissipation in thin films of Ta2O5 and Ta2O5 doped with TiO2”, Class. Quantum Grav. 26 155012 (2009)

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Some potential improvement for future coatings

  • Crystalline coatings -- AlGaAs
  • Multi-material coatings – amorphous silicon
  • Nano-meter layers structure
  • Chemical Vapor Deposition (CVD) – Silicon nitride

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

AlGaAs Crystalline Coatings

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  • G. D. Cole, W. Zhang, M. J. Martin, J. Ye, and M. Aspelmeyer, Nature Photonics (2013)
  • G. D. Cole LIGO-G1401152 (2015)

Need to transfer the coatings to large area substrate. Currently 100-mm diameter GaAs on silica

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Multi-materials coatings

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Multi-materials QW stack : lower optical loss but higher mechanical loss materials in the front layers and higher optical loss but lower mechanical loss in the back layers Conventional Ta2O5/SiO2 QW stack has lower optical loss but higher mechanical loss than the amorphous silicon/SiO2 QW stack Jessica Steinlechner, Iain Matin, LIGO-P1500256

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

IBS nano-meter layers (collaboration between NTHU and U. Sannio (Prof. Innocenzo Pinto)

25 50 75 100 0.0 2.0x10

  • 4

4.0x10

  • 4

6.0x10

  • 4

8.0x10

  • 4

1.0x10

  • 3

1.2x10

  • 3

Bending mode: 676.5 Hz 1890.6 Hz Torsional mode: 1251.5 Hz 3796.2 Hz

Coating loss Temperature(K)

SiO2 (Anneal 600oC 24hr)

25 50 75 100

0.0 5.0x10

  • 4

1.0x10

  • 3

1.5x10

  • 3

2.0x10

  • 3

2.5x10

  • 3

3.0x10

  • 3

3.5x10

  • 3

Bending mode: 676.7 Hz 1890.5 Hz Torsional mode: 1251.5 Hz 3796.2 Hz

Coating loss Temperature(K)

SiO2 (As-deposited)

25 50 75 100 0.0 2.0x10

  • 4

4.0x10

  • 4

6.0x10

  • 4

8.0x10

  • 4

1.0x10

  • 3

1.2x10

  • 3

1.4x10

  • 3

Bending mode: 666.4 Hz 1860.3 Hz Torsional mode: 1268.7 Hz 3840.1 Hz

Coating loss Temperature(K)

TiO2 (As-deposited)

Room Temperature Cryogenic (LIGO-G1601703)

  • H. W. Pan, S. J. Wang, S. Chao et al, OPTICS EXPRESS, vol 22, (2014).

LIGO-G1501024

No cryogenic peaks !!

Currently, we are measuring the cryogenics loss of the 19-layer nano-layer

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

At NTHU, aside from IBS for nano-meter layers with U. Sannio, we also focus on : New deposition method – CVD and new material -- SiN

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Large area uniform coating on silicon wafer up to 18“ (450mm) by Chemical Vapor Deposition (CVD) is a common practice in Taiwan’s silicon-IC industry At National Tsing Hua University (NTHU), we are exploring mirror deposition for GW detector by using CVD method with low loss thin film materials (SiN).

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Ref : Donald L. Smith, et al.“ mechanism of SiNxHy Deposition from NH3-SiH4 plasma”. J.Electrochem. Soc. 137, 614-623(1990)

With fixed N2 gas flow at 980 sccm, we used 5 recipes with different gas flow rate :

Gas flow rate SiH4/NH3(sccm) Composition thickness * (nm) Refractive index† @1550nm Young’s modulus (GPa) Stress (MPa) Uncoated cantilever frequency Coated cantilever frequency 45/15 SiN0.40 159.1±2.7 2.300±0.006 103.7±5.6 120.2±15.5 103.42 103.47 38/22 SiN0.49 179.2±1.4 2.138±0.005 107.0±10.8 143.8±13.2 107.32 107.38 25/30 SiN0.65 198.5±0.8 1.930±0.002 131.6±4.8 256.7±6.6 104.88 105.02 15/45 SiN0.79 204.4±1.5 1.816±0.001 137.7±9.7 382.2±21.3 107.37 107.53 8/48 SiN0.87 211.8±0.1 1.783±0.001 137.0±9.2 412.7±20.0 106.93 107.5

Adjusting the ratio of the gas flow rate, the composition of the SiN film can be changed

Ref : J. N. Chiang, et al “Mechanistic Considerations in the Plasma Deposition of silicon nitride film” J. Electrochem.

  • Soc. 137, 2222-2226.(1990)

Fabrication of SiN film on Silicon by Plasma-enhanced CVD (PECVD)

17 Deposit on polished surface

SiNx

Plasma

LIGO-Gxxxxxx LVC meeting, Stanford University, Aug. 25,2014 * Means QW thcknessof 1550nm † Extinction coefficient <10-4@1550nm for all

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Process chamber1：SiNx Process chamber2： SiO2

Plasma Enhanced Chemical Vapor Deposition (PECVD) for multi-layer dielectric mirror coating Silicon substrate side view

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Process chamber1：SiNx Process chamber2： SiO2

Plasma Enhanced Chemical Vapor Deposition (PECVD) for multi-layer dielectric mirror coating Silicon substrate side view

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Optical properties (measured by ellipsometer) Young’s modulus (measured by nano-indentation) Refractive index @ 1064 ＆ 1550 nm Stress (measured by curvature meter)

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Optical and Mechanical Properties of SiNx film

( LIGO-G1400851) ** Optical absorption of low-stress LPCVDsilicon nitridemembranefrom Norcada were: 213±17 ppm @1550 nm (deff = 2.2 um, α = 0.97±0.1 cm-1 → 𝜆 = 1.2x10-5) 1512±27 ppm @1064 nm (deff = 2.2 um, α = 6.87±0.69 cm-1 → 𝜆 = 5.8x10-5)

**J. Steinlechner et al., “Optical absorption of silicon nitride membrane at 1064 nm and at 1550 nm”, LIGO-P1600343

0.30 0.45 0.60 0.75 0.90 80 90 100 110 120 130 140 150

SiNX

Young's modulus(GPa)

X

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Mechanical loss of single SiNx layer

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei 22

  • - Loss of the lowest mode correlated with the trend of stress, Young’s modulus and composition.
  • - Loss of high index SiN0.40 is lower than that of 14.5% Ti: Ta2O5 (2x10-4 @ ~2000Hz [1][2])
  • - Refractive index of SiN0.40 is higher than that of 14.5% Ti: Ta2O5 (n = 2.07@1064 nm, n=2.05 @1550nm)

[1] I. Martin, H. Armandula, C. Comtet, M. M Fejer et al, Class. Quantum Grav. 25, 055005 (2008) [2] I. W. Martin, E. Chalkley, R. Nawrodt, et al, Class. Quantum Grav. 26, 155012 (2009)

1000 2000 3000 4000 5000 6000 7000 10

  • 6

10-5 10

  • 4

10

  • 3

SiN0.40(n = 2.30@1064, n=2.28@1550) SiN0.65(n = 1.93@1064, n=1.92@1550) SiN0.87(n = 1.78@1064, n=1.78@1550)

Coating loss angle Frequency (Hz)

Room Temperature Loss Angle of SiNx Film with Different Compositions

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Torsional mode: Bending mode:

~1854 Hz

SiN0.87 SiN0.65 SiN0.40

Coating loss angle Temperature (K)

x10-4 23

  • - SiN0.40 and SiN0.65 have no cryogenic peak and low loss, but SiN0.87 shows a peak @ about 40K
  • - We are investigating annealing effect on loss angle and optical absorption of SiNx films.

Cryo peak No cryo peak and low loss

Cryogenic Loss Angle of SiNx Film with Different Compositions

~664 Hz

SiN0.87 SiN0.65 SiN0.40

Coating loss angle Temperature (K)

x10-4 ~1269 Hz

SiN0.87 SiN0.65 SiN0.40

Coating loss angle Temperature (K)

x10-4 ~3845 Hz

SiN0.87 SiN0.65 SiN0.40

Coating loss angle Temperature (K)

x10-4

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Mechanical loss of PECVD Quarter-wave SiN0.40/SiO2 Stacks

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Room Temperature Loss Angle of QW SiN0.40 /SiO2 Stack (LIGO-G1601702)

Coating loss angle Frequency (Hz)

From 1-pair sample From 2-pair sample From 3-pair sample From 4-pair sample

  • - The coating loss angles are in 10-5 range at 100 Hz.
  • - The coating loss does not increase with pair number, indicating that there is no

significant loss in SiN0.40/SiO2 interface.

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei [1] LIGO white paper LIGO-T15TBI-v1 July, 2016

Thermal Noise Estimation of SiN0.40/SiO2 QW HR at Room Temperature

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10 100 1000 10

  • 25

10

  • 24

10-

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aLIGO [1] A+ [1] SiN0.40/SiO2 on silicon (max.) SiN0.40/SiO2 on silicon (min.)

Strain (1/ 𝐼𝑨) Frequency (Hz)

– SiN0.40/SiO2 HR : 18 pairs of QW SiN0.40/SiO2 + one λ/2 SiO2 protective layer. (total thickness=8.57 um, transmittance =0.26 ppm) – Strain of SiN0.40/SiO2 QW HR is 3 ~ 4 times lower than that of the aLIGO specification and 1.5 ~ 2 times lower than the A+ specification.

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Cryogenic Loss Angle of QW SiN0.40 /SiO2 Stack

  • - The cryogenic loss is boosted by the cryogenic peak of SiO2.
  • - The experimental values are lower than the calculated values that were obtained from the

individual layers.

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20 40 60 80 100

5 10 ~1873 Hz

SiO2 SiN0.40

SiN0.40/SiO2 (experimental) SiN0.40/SiO2 (calculated)

Coating loss angle Temperature (K)

x10-4

Bending mode: Torsional mode:

20 40 60 80 100

5 10 ~3705 Hz

Coating loss angle Temperature (K)

x10-4

SiO2 SiN0.40

SiN0.40/SiO2 (experimental) SiN0.40/SiO2 (calculated)

20 40 60 80 100

5 10 ~671 Hz

Coating loss angle Temperature (K)

x10-4

SiO2

SiN0.40

SiN0.40/SiO2 (experimental) SiN0.40/SiO2 (calculated)

20 40 60 80 100

5 10

Coating loss angle Temperature (K)

x10-4 ~1221 Hz

SiO2 SiN0.40

SiN0.40/SiO2 (experimental) SiN0.40/SiO2 (calculated)

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

  • Challenges for coatings of the future detector

– low mechanical loss in room temp. – Low mechanical loss in cryogenics – Low optical absorption and scattering – Larger area uniform coatings

  • CVD deposition process for large area coatings is promising.
  • SiNx films deposited by CVD have low mechanical loss at room

temp and cryogenic. Optical absorption measurement by PCI is

  • ngoing.
  • Quarter-wave stacks of SiNx/SiO2 deposited by CVD have low

mechanical loss at room temp and cryogenic.

Conclusion

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The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Major In-house Facilities at NTHU

  • Ion Beam Sputter coater
  • Room temp. cantilever ring-down Q measurement
  • Cryogenice cantilever ring-down Q measurementFacilities
  • Photothermal common path interferometer (PCI) for ultra-low
  • ptical absorption measurement

Facilities at National Nano-Devices Lab (NDL) accessible to us

  • Full silicon IC process facilities
  • CVD coaters
  • Elcetron microscopes, TEM, SEM, XED
  • X-ray diffractometer
  • ESCA for compisition analysis
  • Nano-indentor for Young’s modulus measurement
  • Stress meter for thin film stress measurement
  • Ellipsometer
  • Welcome collaborations with people in KAGRA

and Virgo

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