MM_total = (MM_vert + MM_horiz) / 2.
The large astigmatic MM loss in the LO case is mainly due to the strong LO4 curvature (R=0.15m) with a 10 deg AOI. I looked again at whether LO1 could be increased from R=5m to the next higher stock value of 7.5m, as this would allow weaker curvatures on LO3 and LO4. However, no, that is not possible---it reduces the LO1-LO2 Gouy phase separation to only 18 deg.
There is, however, a good stock-curvature option if we want to reconsider actuating LO4 instead of LO2 (attachment 1). It achieves 99.2% MM with the OMCs, allowing positions to vary +/-1" from the current design. The LO1-LO4 Gouy phase separation is 72 deg.
| Optic |
ROC (m) |
Distance from PR2 AR (m) |
| LO1 |
10 |
0.378 |
| LO2 |
1000 |
2.984 |
| LO3 |
10 |
4.571 |
| LO4 |
7.5 |
4.926 |
Alternatively, we could look at reducing the AOI on LO3 and LO4 (keeping LO1-LO2 actuation). |