After adding another 1/2 plate to have P wave into the cavity, I can lock the PMC cavity. It's been 30 minutes so far.
There is only one transmitted beam now (there were two when I used S wave.)
When I work or knock on the table, sometime the beam switches to another mode (might be it's side band.)
It's very close to the main TEM00 mode. I need to adjust the DC offset a little bit to get back.
The incoming power is 9 mW, and the Transmitted beam has ~ 6 mW.
RF Amp: 7V
Phase shift: 2.87 + 180
Gain: 27.91 dB
DC offset: -2.3 V
I tried to pre align the ref cavity. It's harder than I thought, can't see the beam that well. I'll have to check the manual for the laser controller, so that I can
scan the RefCav when I align the beam into the cavity.