LIGO Document E0900073-v3
- Note: LIGO-C1105183
TDM 12 has been issued to confirm LIGO acceptance of the Change Proposal for the Beam Splitter 2-design coating approach.
From the minutes of the meeting held 4 May 2011. "A four layer design is attractive since it is thicker and will require less counter coating in order to achieve the flatness specification. On the HR side a 1 degree AOI tolerance requires +/- 1% tolerance on the coatings for a 50+/- 0.5 % T/R performance, whereas a 0.3 degree AOI tolerance requires a coating tolerance of 2% resulting in a 50 +/- 0.3% T/R performance. The AOI spreadsheet transmitted during the meeting to CSIRO showed that two designs would be necessary for AOI of 45.76 and 44.97 degrees."
Four Beamsplitters are designated for use at the H1/L1 angle of incidence: 44.9707 to 44.9760 these are to be called "type 1"
Two Beamsplitters are designated for use at the H2 angle of incidence: 45.7606 to 45.7620 these are to be called "type 2"
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