R&D (FilterCavity)
YuhangZhao - 21:29, Wednesday 16 May 2018 (778)
The misalignment effect brought by AOM modulation

Participaint: Marc, Matteo

We used PSD(position sensitivite detector) to detect the beam dittering incured by AOM modulation.

The modulation information of AOM: 2MHz(pk-pk), 10Hz(50ms for a half period). This gives us AOM scanning velocity of 40MHz/s. (this is really a fast scan!)

We put PSD inbetween the telescope after AOM. Although this gives us diffcuilty, but this is the only proper place to put PSD. See attached picture 1 to know how can we propagate the dittering back through the lens.

The calibration we use the result of entry 276. It is 0.0071[m/V]. We use it to transfer the voltage change of PSD to the beam dittering in meter.(Then we got "x" in attached picture 1)

 

Conclusion: See attached picture 2. We have 10.7e-6[rad] angle change corresponding to frequency change of 2MHz.

Images attached to this report
778_20180516142813_474292500.jpg 778_20180516142827_aom.png
Comments related to this report
YuhangZhao - 22:54, Thursday 24 May 2018 (786)

The serial number of AOM is MT110-A1.5-VIS. I checked the manual today. The best input modulation voltage is 1V. There is also one information about the seperation angle's relationship with wavelength. However, the manual is so sketchy that I cannot understand clearly. 

Bad thing: The operating manual is only availabe for someone has account of that company!

YuhangZhao - 14:34, Monday 28 May 2018 (790)

I find there is a mistake in the calculation, see attached picture 1. I used a wrong unit for a number. After the correction, I plot the result again(see attached picture 2)

Now the error on AOM is 1.07mrad.