bram.slagmolen@LIGO.ORG - posted 17:48, Tuesday 17 July 2012 - last comment - 19:47, Tuesday 17 July 2012(3471)
ISCTEY (ALS table at EY) optical power measurements
Keita and Bram
We measured the power inthe optical train on the ISCTEY (after the RF LSC Diode swap, see entry 3470).
Forward path: Laser -- FI1 --- 30 mW --- FI2 --- EOM --- 27 mW --- FI3 --- Mirrors + lenses --- 20 mW ---- retro mirror
Return path to RF LSC Diode: retro mirror --- FI3 --- 7 mW --- R=80% mirror --- 4 mW -- RF LSC Diode
Return path to WFS: FI3 -- 7 mW --- T=20% mirror --- 3 mW --- to both WFS.
- Laser = Innolight Prometheus laser
- FI1 = Isowave faraday Isolator (5mm aperture)
- FI2 = Isowave faraday isolator (5mm aperture)
- EOM = New Focus resonant phase modulator
- FI3 = Drever (OFR?) faraday isolator (aperture 5mm)
The DC output gives us 45 mV (48 mV with lens), resulting in 3 mW (3.2 mW) of power being 'converted'. About 0.3 mW is being reflected and dumped.
We added a half waveplate just before the R=80% beam splitter, as all mirrors are coated for vertical polarised light (it becomes apperant that there are tom any waveplates on the table!!)
With this, we get 6.3 mW on the RF LSC Diode and 1.07 mW into the main WFS path (this will get split by a 50-50 beam splitter, so ~0.5 mW per WFS).
This in turn gives 69 mV (edit: removed the 0.) on the DC output of the LSC diode, e.g. 0.69 / (10 * 5 * 0.3) = 4.6 mW.