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

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 • Academia Sinica (NTU campus), Taipei 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) 1 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

LIGO-T1400316-v4 2 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Noise Spectrum GW150914 Dominant noise sources: Coating Brownian thermal noise Quantum noise – shot noise and radiation pressure noise Thermal noise for mirror: 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 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. • The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Current coating technologies for a-LIGO The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Current mirror coatings for a-LIGO -- material Snipview.com Currently for a-LIGO : - Fused silica substrate (34 cm in diameter 20 cm in thickness and 40 Kg ) - Ta 2 O 5 -TiO 2 mixed film for high index layer, and SiO 2 film for low index layer coatings 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 LMA à 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. The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

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

Cryogenic loss leak for IBS SiO 2 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) The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Cryogenic loss peak of Ta 2 O 5 and Ta 2 O 5 -TiO 2 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) 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 11 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

AlGaAs Crystalline Coatings Need to transfer the coatings to large area substrate. Currently 100-mm diameter GaAs on silica G. D. Cole, W. Zhang, M. J. Martin, J. Ye, and M. Aspelmeyer, Nature Photonics (2013) G. D. Cole LIGO-G1401152 (2015) 12 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Multi-materials coatings Conventional Ta 2 O 5 /SiO 2 QW stack has lower optical loss but higher mechanical loss than the amorphous silicon/SiO 2 QW stack 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 Jessica Steinlechner, Iain Matin, LIGO-P1500256 13 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) Room Temperature H. W. Pan, S. J. Wang, S. Chao et al, OPTICS EXPRESS, vol 22 , (2014). LIGO-G1501024 Cryogenic (LIGO-G1601703) TiO 2 (As-deposited) SiO 2 (As-deposited) SiO 2 (Anneal 600 o C 24hr) -3 Bending mode: 676.5 Hz 3.5x10 Bending mode: 666.4 Hz Bending mode: 676.7 Hz 1.2x10 -3 1890.6 Hz 1.4x10 -3 1860.3 Hz 1890.5 Hz Torsional mode: 1251.5 Hz Torsional mode: 1268.7 Hz Torsional mode: 1251.5 Hz -3 3796.2 Hz 3.0x10 3796.2 Hz 3840.1 Hz -3 1.2x10 -3 1.0x10 -3 2.5x10 1.0x10 -3 Coating loss Coating loss Coating loss -4 8.0x10 -3 2.0x10 8.0x10 -4 6.0x10 -4 -3 1.5x10 6.0x10 -4 4.0x10 -4 -3 1.0x10 4.0x10 -4 No cryogenic peaks !! 2.0x10 -4 -4 -4 2.0x10 5.0x10 0.0 0.0 0.0 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 Temperature(K) Temperature(K) Temperature(K) Currently, we are measuring the cryogenics loss of the 19-layer nano-layer 14 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 15 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). 16 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Fabrication of SiN film on Silicon by Plasma-enhanced CVD (PECVD) Plasma Ref : Donald L. Smith, et al.“ mechanism of SiN x H y Deposition from NH 3 -SiH 4 plasma”. J.Electrochem. Soc. 137 , 614-623(1990) SiN x Ref : J. N. Chiang, et al “ Mechanistic Considerations in the Plasma Deposition of silicon nitride film” J. Electrochem. Soc. 137 , 2222-2226.(1990) Adjusting the ratio of the gas flow rate, the Deposit on polished surface composition of the SiN film can be changed With fixed N 2 gas flow at 980 sccm, we used 5 recipes with different gas flow rate : Gas flow rate Composition thickness * Refractive index † Young’s Stress Uncoated Coated SiH 4 /NH 3 (sccm) (nm) @1550nm modulus (GPa) (MPa) cantilever cantilever frequency frequency 45/15 SiN 0.40 159.1 ± 2.7 2.300 ± 0.006 103.7 ± 5.6 120.2 ± 15.5 103.42 103.47 38/22 SiN 0.49 179.2 ± 1.4 2.138 ± 0.005 107.0 ± 10.8 143.8 ± 13.2 107.32 107.38 25/30 SiN 0.65 198.5 ± 0.8 1.930 ± 0.002 131.6 ± 4.8 256.7 ± 6.6 104.88 105.02 15/45 SiN 0.79 204.4 ± 1.5 1.816 ± 0.001 137.7 ± 9.7 382.2 ± 21.3 107.37 107.53 8/48 SiN 0.87 211.8 ± 0.1 1.783 ± 0.001 137.0 ± 9.2 412.7 ± 20.0 106.93 107.5 * Means QW thcknessof 1550nm † Extinction coefficient <10 -4 @1550nm for all 17 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei LIGO-Gxxxxxx LVC meeting, Stanford University, Aug. 25,2014

Plasma Enhanced Chemical Vapor Deposition (PECVD) for multi-layer dielectric mirror coating Process chamber1 ： SiNx Process chamber2 ： SiO 2 Silicon substrate side view 18 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Plasma Enhanced Chemical Vapor Deposition (PECVD) for multi-layer dielectric mirror coating Process chamber1 ： SiNx Process chamber2 ： SiO 2 Silicon substrate side view 19 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Optical and Mechanical Properties of SiNx film ( LIGO-G1400851) Refractive index @ 1064 ＆ 1550 nm Optical properties (measured by ellipsometer) Young’s modulus (measured by nano-indentation) Stress (measured by curvature meter) 150 140 Young's modulus(GPa) 130 120 110 100 90 80 X 0.30 0.45 0.60 0.75 0.90 SiN X ** Optical absorption of low-stress LPCVDsilicon nitridemembranefrom Norcada were: 213 ± 17 ppm @1550 nm (d eff = 2.2 um, α = 0.97 ± 0.1 cm -1 → 𝜆 = 1.2x10 -5 ) 1512 ± 27 ppm @1064 nm (d eff = 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 20 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei

Mechanical loss of single SiNx layer 21 The 3rd KAGRA International Workshop (KIW3) May 21-22, 2017, Academia Sinica(NTU campus), Taipei