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. Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics 1 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Noise Spectrum GW150914 Dominant noisesources: Coating and suspension Brownian thermal noise Quantum noise– shot noise -- radiation pressure noise Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Snipview.com Currently for a-LIGO : Ta 2 O 5 -TiO 2 mixedfilmfor high index layer, SiO 2 film for low index layer, and Feud silicasubstrate (34 cmin diameter 20 cm in thickness and 40 Kg ) Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Ion Beam Sputter (IBS) for a-LIGO Mirror Coatings 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 detector. Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Thermal Noise Fluctuation-Dissipation Theorem says: Fluctuation of a system is proportional to its dissipation Example: Brownian motion, Johnson noise Sx ω ( ): power spectral density of mirror surface fluctuation ! χ : mechanical susceptibility (strain-stress ratio) ( ): mechanical loss angle φ ω T : temperature of the system (K) 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 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Mirror Substrate Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

[1] CE(pess) [2] ET-D-HF [3] ET-D-LF [1] [1] [1] [1] [3] aLIGO A+ Voyager CE KAGRA Arm Length [km] 4 4 4 40 40 3 10 10 Mirror Mass [kg] 40 80 160 320 320 30 200 211 Mirror materials Silica Silica Silicon Silica Silicon Sapphire fused silica silicon Mirror Temp [k] 295 295 123 295 123 20 290 10 Sus Fiber 60cm SiO 2 60cm SiO 2 60cm Si 1.2m SiO 2 1.2m Si Sapphire fused silica silicon Fiber Type Fiber Fiber Ribbon Fiber Ribbon Fiber Fiber Fiber Input Power [w] 125 125 300 150 220 75 500 3 Arm Power [kW] 710 1150 3000 1400 2000 810 3M 18k wavelength [nm] 1064 1064 1550 1064 1550 1064 1064 1550 NN suppresion 1 1 10 10 10 -- -- -- Beam size [cm] 5.5/6.2 5.5/6.2 6.7/7.5 12/12 14/14 -- 7.25 9 SQZ Factor [dB] 0 6 8 10 10 -- -- -- F. C. Length [m] none 16 4000 4000 4000 -- -- -- [1]LIGO LIGO document LIGO-T15TBI-v1 [2] KAGRA Study report on KAGRA interferometer observation band, 8th Sep. 2009 http://gwcenter.icrr.u-tokyo.ac.jp/en/researcher/parameter [3]ET The Einstein Telescope design study (FP7-Capacities, Grant Agreement 211743) P.243 http://www.et-gw.eu/ Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

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) Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

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) Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Some potential improvement for future coatings • Crystalline coatings -- AlGaAs • Multi-material coatings – amorphous silicon • Chemical Vapor Deposition (CVD) – Silicon nitride 10 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

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) 11 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

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 12 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Chemical Vapor Deposition (CVD) for multi-layer dielectric mirror coatings The CVD processes for these amorphous thin film materials are well established in IC industry : a-Si n= 3.56 (λ=1550 nm) absorption range < 700 nm SiO 2 n= 1.45 (λ=1550 nm) absorption range < 200 nm SiNx n= 1.77 ~ 2.28 (λ= 1550 nm) absorption range < 540 nm QW high and low index films deposited SiC n= 2.58 (λ=1064nm) [1] alternately in two absorption range < 380 nm reaction compartments (Eg=3.26 eV) [2] National Nano Device Lab (NDL) of Taiwan [1] Singh et al. 1971 - α-SiC; n(o) 0.488-1.064 µm LPCVD system [2] TAKU HAMAGUCHI ／ ROHM Semiconductor, Santa Clara, CA. 18” silicon wafer process in IC industry. Larger than LIGO mirrors. Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

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 14 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Candidate Silicon IC-Compatible CVD Thin Films for Optical Application a-Si SiC SiNx SiO 2 Refractive index 3.5 [1] 3.2-2.6 [11,12] 2.6-1.8 [16][30] 1.45 [19,20] @ 1550 nm Absorption range <700 nm [2] <380 nm [13] <510 nm [17] <200 nm [21] Young’s modulus 100 ~ 150 [3-5] 392 ~ 694 [14] 85~210 [16] 72~83 [20,22-25] (GPa) Stress # (MPa) -400 ~ -900 [6,7] -160 ~ -510 [15] +600 ~ 1200 [16] +60 ~ -257 [25] ~2x10 -6 high stress [18] 3.3x10 -4 e beam [8] ~3x10 -4 stress relief [18] 1.49x10 -4 5x10 -4 sputter [8] Loss angle at RT -- 4x10 -4 IBS [31] 7.5x10 -5 SiN 0.40 @107Hz 1x10 -4 IBS [26-28] 1.4x10 -5 SiN 0.87 @107Hz [30] 9x10 -5 IBS [10] Depends on N- Depends on H + - concentration Cryogenic loss concentration and -- ( Preliminary results will be 5x10 -4 @20K [29] peak heat treatment [8-10] presented in poster session by Mr. Kuo ) # - : compressive +: tensile 15 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics

Fabrication of SiN film on Silicon by 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 16 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics 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 17 Workshop on Gravitational Wave activities in Taiwan (GWTW) January 15, 2017 • Academia Sinica, Institute of Physics