Some problems found today

The first problem is that I found out the upper part of the cavity(pointed by the arrow in the picture) can be moved, and if I twist a little bit in counterclockwise to maximum, I will get TEM00.

Then the EOM is very sensitive, even touch it can change the transmit power. There are some possibility, one is while touching, the alignment changed, the other one is there are some electric effect, but not quiet sure about this guess. Or it maybe caused by the polarization before the EOM.

So I will check the following things: the alignment of the EOM, the polarization between the laser and the EOM.

Checking the alignment of EOM is also because we lose too much power there, and also between the waveplate, I have already check the waveplate all have AR coating. At the very beginning of the experiment, I checked the transmission rate of the Faraday Isolator and EOM are both less than 90%.

There are also a small problem with the BS mirror, the beam is near the edge of the mirror which will lead to more scattering. So I will also adjust the position of it.