anthony.sanchez@LIGO.ORG - posted 19:39, Monday 30 June 2025 - last comment - 16:58, Wednesday 02 July 2025(85447)
PCAL Lab TX module Maintenance complete
On Friday Jun 27th Francisco and I went to the the PCAL lab and did a PCAL TX module maintenance according to T1600436.
AOM alignment was touched up
Results:
| Laser SN05 | |
| Date | June-26-2025 |
| Laser Shutter Check | Fail |
| Max OFS Offset | 7.2V |
| 95% OFS Offset | 6.84V |
| Operating OFS Offset | 3.42V |
| Laser Output Power | 1.97W |
| Rejected Laser Power | 3.3mW |
| AOM Input Power | 1.92W |
| Max Diffracted Power | 1.23W |
| Un-Diffracted Power | 0.500W |
| AOM Diffraction Efficiency | 64% |
| AOM Rejected Power | 3.3mW |
| TxPD Power | 1.4mW |
| OFSPD Power | 1.73mW |
| Outer Beam Power | 294mW |
| Inner Beam Power | 292mW |
| Output Beam Power Ratio | 0.9932 |
| OFS Gain | 7.50V |
| OFS Phase Margin | 43.7 |
| ALOG |
Non-image files attached to this report
Comments related to this report
After the maintenance I tweeked the AOM to increase the diffraction efficiency. The nominally, the diffraction should be above 70% efficiency, which translates to 1.34 W from the *Maestro*. My procedure went as follows:
- Set the OFS offset to the recorded max: 7.2 V on V2 of the HP power supply on the upper right (when looking from the front)
- Once the offset is set, block the beam (be safe!)
- Placed the high-power head (HPH) before the AOM on the Tx module
- Zero-ed the readout and then unblock the beam.
- Readout: 1.92 W (consistent with maintenace done the day before).
- Placed HPH before the wedged beamsplitter
- Readout: 1.24 W (consistent with maintenace done the day before).
- So far, everything is consistent with the maintenance. We can now adjust the AOM.
- The AOM is placed on a New port stage, following the documentation for this component, the bottom screws will adjust the Y axis (height) and the top screws will adjust the X axis (angle of incidence).
- Adjusted Y1 and Y2 -- bottom left and bottom right screws, respectively. A counter-clockwise adjustment of each screw, to about one turn, increased the output to 1.28 W.
- Adjusted X1 and X2 -- top left and right screws -- to reach 1.30 W. Fine adjustments could not get a higher output.
- Returned offset to operating value of 3.42 V on power supply.
AOM alignment increased the efficiency to 67%, a gain of 3%.