Following Yuhang: Procedure to lock MC green (MCG) and MZ

1. Lock SHG
2. turn on high-voltage drivers of MZ and MCG
3. Check alignment of MCG using a ramp  (typical value 7.05Hz, 1Vpp) now we are using s-pol but anyway it should be the same procedure with p-pol
4. if the alignment is fine, set the gain of standford to gain = 1. Use a simple lowpass pole at 3Hz on the standford.
5. tune MCG PZT driver offset to go as close as possible to the TEM00 peak
6. close the loop of MCG (put MCG correction in input of MCG driver)
7. increase the gain of standford to 5
8. tune the MZ high voltage offset. You should see max and min. Now we are locking a little higher than mid-fringe in order to get enough tranmitted power by MCG (1V on oscilloscope which corresponds to 12.5mW)
9. On MZ servo check EP mon (Error Point monitor)  and put it to 0 changing its offset
10. NOTICE : WE NEED TO MAKE SURE THE GAIN IS HIGH ENOUGH (USUALLY 10) TO AVOID THE UNSTABILITY AT 600 HZ
11. On MZ servo turn on lock and integrator

To measure MZ openloop TF we injected noise in the servo input ''add'' and take TF between  EP mon and input. For a swept sine typical noise value is 50 mVpk

Notice: if you vibrate the bench too much, you will destory the lock of MZ.