1. Steve Penn, Gregg Harry (MIT)
Coating Loss Measurements on Thin Fused Silica Substrates LIGO-G Z
Steve Penn, Gregg Harry (MIT)
Sasha Ageev, Andri Gretarrson, Scott Kittleberger, Luis Lopez, Peter Saulson
Syracuse University

2. Syracuse University Experimental Relativity Group
Outline
Goals of Coating Loss Experiment
Plan for Coating Measurements on Thin Substrates
Thin Substrate Experimental Set-up & Sources of Loss
Modifications for Future Coatings Work
LSC • March 2002
Syracuse University Experimental Relativity Group

3. Review of Coating Program
Levin (1998) showed coatings could be a limiting source of loss.
Preliminary measurements at Glasgow and Syracuse indicated coating  2.5 x  Test Mass Q’s  107
Advanced LIGO requires coating  10-5 for Sapphire masses and 200 Mpc range.
Coating program initiated:
Thin Substrates with birefringent readout (Syracuse & MIT)
Thick Substrates with interferometric readout (Glasgow & Stanford)
LSC • March 2002
Syracuse University Experimental Relativity Group

4. Thin Substrate Measurements
Uncoated, Super-polished Disks (Mindrum & Wave Precision), Q = 6–20 million
Annealed, Uncoated, Superpolished Disks, Q 45 million
Coated Disk, 2-layers, (l/4 Ta2O5, l/4 SiO2) Q 9 million
Coated Disk, 30-layers, (l/4 Ta2O5, l/4 SiO2) Q 500,000
Coated Disk, 30-layers, (3l/8 Ta2O5, l/8 SiO2) Q 400,000
Coated Disk, 60-layers, (l/8 Ta2O5, l/8 SiO2) Q 500,000
LSC • March 2002
Syracuse University Experimental Relativity Group

6. Syracuse University Experimental Relativity Group
LSC • March 2002
Syracuse University Experimental Relativity Group

7. Syracuse University Experimental Relativity Group
LSC • March 2002
Syracuse University Experimental Relativity Group

8. Syracuse University Experimental Relativity Group
LSC • March 2002
Syracuse University Experimental Relativity Group

9. Benefits of the Thin Disk Method
Geometry enhances DQ due to coatings ( factor 40)
Suspension methods (welding, collet & bob) are low loss
Tiny ( 100 mm) welds do not disturb coatings (DT  0)
In-air feedback allows for mode identification
Birefringence Readout has high SNR & clean analysis
Excellent Agreement of Results between labs
LSC • March 2002
Syracuse University Experimental Relativity Group

10. Effect of the Isolation Bob
LSC • March 2002
Syracuse University Experimental Relativity Group

11. Annealed, Uncoated Disk
LSC • March 2002
Syracuse University Experimental Relativity Group

12. Syracuse University Experimental Relativity Group
LSC • March 2002
Syracuse University Experimental Relativity Group

13. Syracuse University Experimental Relativity Group
LSC • March 2002
Syracuse University Experimental Relativity Group

14. Syracuse University Experimental Relativity Group
LSC • March 2002
Syracuse University Experimental Relativity Group

15. Thin Disk Method for Sapphire?
Benefits of low cost, fast turn-around, and low noise measurements.
Problems with attachment
Bonding not preferable due to loss
Is welding sapphire possible? Even if possible, amorphous weld would likely have higher loss.
Develop a TAMA-like suspension using pins holding the sample edges
LSC • March 2002
Syracuse University Experimental Relativity Group

16. Syracuse University Experimental Relativity Group
F vs V/S — Part I
Flame drawn fibers only
LSC • March 2002
Syracuse University Experimental Relativity Group

17. Syracuse University Experimental Relativity Group
F vs V/S — Part II
Add non-fiber samples
LSC • March 2002
Syracuse University Experimental Relativity Group

18. Syracuse University Experimental Relativity Group
F vs V/S — Part IV
Add flame polished disk
LSC • March 2002
Syracuse University Experimental Relativity Group