Converted 51nanoL to Class3R by injecting it directly into fiber-coupled splitter. Output power of each port is 0.17mW due to excess insertion loss from FC/PC coupler instead of FC/APC coupler. Expected output power from each port is 2.5mW at 520nm.
1118 - At ETMY, getting set up on go onto ALS/HWS table. ALS laser is OFF. Using T1900654 as guide for work. On table with fan on.
1123 – ETM HWS MEDM screens have reverted to old versions with no control of LED light source.
1132 – Adjusting the launch irises to be centered on the existing HWS beam
1136 – Lens 1 (closest to ETMY): PLCX-50.8-1030.2
Lens2: PLCX-25.4-1030.2
Lens3: PLCC-25.4-257.5
1137 – Distances between optics
LPMtoPBS: 305mm
PBStoM1: 65mm
M1AtoM1B: 113mm
M1BtoM1C: 25mm
M1CtoL1: 83mm
L1toL2: 610mm
L2toM2: 38mm
M2toM3: 67mm
M3toM4: 662mm
M4toM5: 68mm
M5toL3: 261mm
L3toM6: 323mm + 3mm BS
M6toHWS: 629mm
1149 – Summary
LPM to L1: target: 570, measured: 591
L1 to L2: target 610, actual 610
L2 to L3: target 1079, actual: 1096
L3 to HWS: target 903, actual 955
1153 – Removed existing LED source and existing unlabled lens (which looks to be about 120mm focal length)
1207 – Added and labeled new f=75mm collimating lens
1227 – Laser on table and 50/50 coupler installed. Final version should be off-table and in a box that converts it to 3R with a single mode fiber output coupler.
1251 – Laser going through optics. Gets elliptical if collimating lens is twisted.
1303 – Got return beam from ETM. Still need to collimate outgoing beam and image correctly.
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1519 – Back at ETMY. Going to measure beam profile and beam convergence.
Distance from source to lens L3
TOTAL = 863mm
Adjusting beam from source to converge at a point 91mm past the lens L3
Using beam scan
1544 – Cleaned up beam on BeamScan to be centered in aperture
Looks single mode
Measurement 1: translation stage = 2.62 units
W1 = 6.8mm, z1 = 327
W2 = 5.5mm, z2 = 505
Delta = 7”
Puts focus 395mm past L3
Measurement 2: TS = 3.00units
W1 = 6.79, z1 = 327
W2 = 4.45, z2 = 505
Puts focus -20mm past L3
Suggests going to 2.90 units
Measurement 3 = 2.88units
W2 = 4.82
W1 = 6.86
Puts focus 58mm past L3
USING this
1603 – now adjusting the aligment so it’s centered on the optics
Looks quite large going through the iris on the periscope
1618 – got return beam on HWS
Nominal solution for HWS imaging of test mass (based on measured distances between lenses this is an estimate of how much we need to move the HWS along the optical axis, DZ, to image the ETM onto the HWS)
DZ nominal for HWS = -176mm, approximately 7”
Still a lot of noise on return beam. Adding a 2" beam tube (snout) onto the HWS cut down on a lot of ambient light coupling into the HWS.
Did basic test of imaging by looking at shadow of AERM move as we pitched the ETM. Try to do proper imaging tomorrow.
Here are some photos of the installation.
Before any changes
After new source installed
New laser source coupling lots of power into the cladding of the 50/50 fiber splitter