The sequence is like this: 1. Mach-Zehnder  2. green mode cleaner 3. OPO

For the purpose of offering a stable light for OPO, we decided to use the transmission of mode cleaner as a feedback signal. Then take this signal to Mach-Zehnder to control MZ's PZT.

We put a beam splitter to get this feedback signal. The transmission is used for feedback. The reflection is used for OPO. The ratio between them is 99.2:0.8 (reflection:7.7mW and transmission:67uW)

The signal we get from transmiaaion photo detector is around 20mV(read from oscilloscope).

The procedure I did:

Firstly, I use SR560 lock green mode cleaner.

Secondly, I make sure the loop for MZ is fine.(check signal is going to control board, move the offset to make error signal close to zero, turn on lock switch, turn on intergrator)

Thirdly, I moved the offset of MZ control, I could see the mode cleaner transmission changed with my adjust.

The noise spectrum is attached.

However, the duration of lock is not good. I tried only once. It is around 10minutes.