Aritomi and Yuhang

After the simulation, we implemented the filter cavity reflection telescope. It was quite strange that I moved a lot to match this beam into AMC. Maybe this is because of the injection is not well mode matched, so the reflection is also not in good shape. But anyway, we put this telescope and tried a lot to improve the matching.

The preliminary result is as the attached figures.

In the first attached figure, we could see there is a mode mismatch peak with a height of 540mV.

In the second attached figure, we could see there is a TEM00 with a height of 6.6V.

In the third and fourth figure, you can find a peak just beside the mode-mismatch peak. It changes height because of the beam jittering in pitch direction. And it can have height up to 860mV.

In the fifth and sixth figure, you can see the TEM00 peak can also change from 5.5V to 7.5V.

Conclusion:

1. We have roughly mode mistach now for filter cavity into AMC as ~7.5%.

2. Beam jittering brings misalignment of up to ~12%.

3. The estimation is not precise because the total reflected IR power also fluctuates. From the experience of green reflection, we see much more stable green reflection after using smaller focal length lens. Maybe we are having this beam clipping issue also for this measurement in IR reflection. We should check this tomorrow.

Found on 5th September, the beam was clipped!