11/20~21 Participants: Chien-Ming, Shu-Rong, and Yuhang

Yesterday we measured the SHG output green beam size again by removing the Faraday isolator and placing the beam profiler. (See Fig.1)
The fitting results indicate that the waist is 28 um inside the SHG and 47 mm from the edge of SHG output port. (see Fig.2)
This result is in the case where the SHG cavity concave mirror is not considered.
Yuhang found that he used the incorrect wavelength in his fitting on 11/19.

Today we tried to recover the mode matching of the green mode cleaner (GRMC) by only adjusting the position of the lens L6 and the alignments of mirrors M5, M6, and M7 as showing in Fig.3.
After optimizing, the new position of L6 on the rail moves from 48mm to 41.5mm (Equal to moving 6.5mm towards the EOM)

Fig.4 shows the mode matching transmission spectrum of the MC when the incident beam is p-polarization.
And Fig.5 is s-polarization.

The transmission efficiency of the MC is 77.7% when using p-pol incident beam and 54% when using s-pol beam. This means that if we want to reach 100 mW GRMC output power when using s-pol incident beam, we will need SHG to provide 270 mW green output power.