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Coating R&D at LMA: Q mechanical measurement of multilayer Ti:Ta 2 O 5 – SiO 2 coating

Coating R&D at LMA: Q mechanical measurement of multilayer Ti:Ta 2 O 5 – SiO 2 coating. Emeline Saracco , Raffaele Flaminio, Janyce Franc, Christophe Michel, Nazario Morgado, Laurent Pinard. Q mechanical measurement at LMA. 1. Q measurement of welded cantilever before coating

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Coating R&D at LMA: Q mechanical measurement of multilayer Ti:Ta 2 O 5 – SiO 2 coating

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  1. Coating R&D at LMA: Q mechanical measurement of multilayer Ti:Ta2O5 – SiO2 coating Emeline Saracco, Raffaele Flaminio, Janyce Franc, Christophe Michel, Nazario Morgado, Laurent Pinard Elba - GWADW - 25th May 2011

  2. Q mechanical measurement at LMA 1. Q measurement of welded cantilever before coating => The use of cantilevers welded to Silica block allows an improved Q measurement sensitivity Silica block 45 mm 5 mm Silica cantilever (110 µm thick) 2. Coating Deposition in Ion beam Sputtering (IBS) deposit chamber on the welded cantilevers - Low index material (L): SiO2 - High index material (H): Ti:Ta2O5 3. Q measurement of the cantilever after coating deposition and annealing Energy stored in the substrate => Calculation of coating and Ti:Ta2O5 loss angle Energy stored in the coating Elba - GWADW - 25th May 2011

  3. Problem: Q mechanical measurement of Ti:Ta2O5 in multilayer coatings SiO2/Ti:Ta2O5 18-layer on a SiO2 substrate Ti:Ta2O5 monolayer on a SiO2 substrate Last SiO2 layer ~ 220 nm Ta2O5 layer Ta2O5 monolayer ~ 75 nm X 8 SiO2 layer Thickness ~ 500 nm ~ 258 nm 1st Ta2O5 layer SiO2 substrate ~ 130 nm Thickness ~ 110 µm SiO2 substrate ~ 110 µm ΦTi:Ta2O5 = 2.3x10-4 +/- 0,6x10-4 Φcoating = 2,1x10-4+/- 0,2x10-4 = > ΦTi:Ta2O5 = 4.7x10-4 +/- 0,2x10-4 (hypothesis : ΦSiO2 = 5x10-5) May 2010 (J. Franc, GWADW Kyoto) “Mechanical losses of different multilayer coatings with no defects have been measured and confirm larger losses than expected” For a 26-layer coating 0.8167H (1.0736L 0.8828H)12 0.085L @ 1064nm : -> LMA mesurement : ΦTi:Ta2O5=4,2x10-4 +/- 0,2x10-4 -> TNI mesurement : ΦTi:Ta2O5=3,8x10-4 +/- 0,4x10-4 Same trend as TNI observation and calculation G-1000937 Elba - GWADW - 25th May 2011

  4. First hypothesis: the layer thickness of Ti:Ta2O5 Study of Mechanical losses as a function of Ti:Ta2O5 monolayer thickness: Dec. 2010 – Jan. 2011 Measurement Three thicknesses studied on six cantilevers for the 3 first modes : - 126 nm - 250 nm - 512 nm => No significant tendency of Ti:Ta2O5 thickness influence on mechanical losses for a monolayer Elba - GWADW - 25th May 2011

  5. Second hypothesis: interfaces in the multilayer Study of Mechanical losses as a function of interface number: Dec. 2010 – May 2011 Measurement Direct comparison: 18-layer coating (H0.675B)4 multilayer bilayer monolayer => For a same Ti:Ta2O5 layer thickness, mechanical losses are higher in multilayer coating than in monolayer Elba - GWADW - 25th May 2011

  6. Second hypothesis: interfaces in the multilayer Study of Mechanical losses as a function of interface number: 2006-2011 Measurement Direct comparison: => Tendency of augmentation of Ti:Ta2O5 mechanical losses with interface number Elba - GWADW - 25th May 2011

  7. Conclusion and future work • Conclusion: • - No effect of Ti:Ta2O5 layer thickness on mechanical losses for Ti:Ta2O5 monolayer • Possible influence of SiO2/Ti:Ta2O5 interfaces on multilayer coating mechanical losses • Perspectives: • - Physicochemical characterization of SiO2/Ti:Ta2O5 interfaces: • Transmission Electron Microscopy (TEM): Study of SiO2 /Ti:Ta2O5 interfaces at atomic structure level • Electron Energy Loss Spectroscopy (EELS): Chemical characterization of SiO2 /Ti:Ta2O5 multilayer coating and interface : interdiffusion? Elba - GWADW - 25th May 2011

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