After align OPO with CC beam, I did the alignment with p-pol beam in this morning. As soon as I launch p-pol beam into OPO, I got the attached figure 1.

We know the p-pol power we sent to OPO is only 5.9mW. The OPO choose s-pol to resonant inside the crystal, so we cannot have green if use this p-pol. But I can see signal for infrared on the photodiode. I use this photodiode signal to align the p-pol beam. The steering mirrors I used are the two steering mirrors we put before combinging p-pol and cc. The alignemt result is attached with scan frequency of 60Hz and amplitude of 3Vpp, the signal is shown on the oscilloscope.

After align them, I measured the power I got for transmission, which is 2.5uW. This is very small so I can use camera directly to see it. I put the camera just in front of photodiode. While scanning the PZT with frequency of 50mHz and 3Vpp ramp signal, I can see the modes I have now. Most of them are pitch higher order modes.

This is the best I can do by moving that two steering mirrors. I still don't know why I cannot improve it anymore.