Now we have two problems with green beam that we haven’t figure out why:
1.There is some high frequency oscillation when the alignment is better, efficiency reach around 40%(Output power of the laser is 500mW). Even if we reduce the power to only 50mW output from the laser, the oscillation still there. We try to change the temperature and increase the power, find out the oscillation disappear, but under this situation, the alignment is not very good, so we need to find out which is the reason that make the oscillation disappear.
2. When we change the PZT output with hand to get near the resonance from one side, the high frequency oscillation will increase first, but then it starts to reduce, when we reach the resonance, we are not at the maximum of the oscillation.
2.We find out there are two TEM00 mode, one is more powerful then the other.
Now we can lock the cavity with 500 gain, and it is stable.
We installed the simple version of the green path, without the EOM, AOM and MZ, just to send the green beam to the chamber to check the position, and for the infrared beam which should go together into the chamber with the green, we increase it to the right height( the height we will reach after we increase the table leg) and align it to let it go through the Faraday Isolator and reflected by a mirror, goes to the direction to the BS chamber.