After the installation of mode cleaner, we measure the contrast again. This method is like this

We use the high voltage driver of MZ as an offset adder. By giving different offset to it, we can have almost all light transmit or almost no light transmit.

Then we record the highest peak hight while almost all light transmit. Record the highest peak hight while almost no light transmit(actually, this is the time when TEM00 almost vanishes).

We got result like attached picture 1.

However, I don't know if this is the right calculation method. (Maybe I should do like Marc did for FC scan, intergrate all the peaks in-between a FSR?)