Yesterday I did a very preliminary check of the AOM operation.  After locking the filter cavity I have changed the driving frequency of the AOM (which is normaly set at 110 MHZ) and I have looked at the correction sent from the servo to the laser piezo.

In the attached picture you can see in yellow the trasmission of the filter cavity and in blue the laser correction (from PZT mon).

I changed the AOM driving frequency in steps of 100 kHz each time. Most of the time this change causes a very short unlock of the cavity, as it can be seen from the picture. Nothing can be noticed in the correction signal.

Since the piezo calibration is 2 MHz/V and the channel PZTmon has an attenuation of 100, a change of 100 kHz should result in a change of 2 mV in the correction, which is likely not visible.  I tried to do bigger steps but the cavity loses easly the lock.

I observed that the correction is about a factor 3 bigger than that measured this summer. (See last picture of entry 475)