R&D (FilterCavity)
YuhangZhao - 10:52, Thursday 08 November 2018 (1079)
Beam measurement preparation for SHG telescope improvement

We decided to change the telescope for SHG. For three reasons:

1. the mode matching for SHG needs to be improved.

2. the beam is too small around one of the mirrors, which may bring probability of damaging mirror

3. the telescope changing will influence the bright alignment beam. So it's better to change it before having telescope for bright alignment beam

I did the measurement in the region shown in the attached figure(in the black block). The fit result is shown in attached figure. The waist is located around the end of EOM for SHG. With a size of 120um.

So if we want to increase power, we also need to investigate the damage threshold of this EOM for SHG. The 50mm lens is located in 30cm after the zero of this plot.

Since this characterization is before 50mm lens, I use Jammt to put this 50mm lens. And compared with the result we got yesterday, they agree with each other. The result is shown in attached figure 3.

Images attached to this report
1079_20181108024937_untitled.png 1079_20181108024943_figure1.png 1079_20181108055836_12.png
Comments related to this report
MarcEisenmann - 18:59, Thursday 08 November 2018 (1080)

As reported entry 769 while working on the green MZ and MC it was found out that the not quite gaussian shape of the beam might come from the SHG.

It might be useful to check if the new telescope can correct this.