Participaint: Aritomi and Yuhang

This beam splitter will be used for homodyne. And the balance of these two power value is very important. So we decide to measure this value.

We bought two BSW41-1064, according to specfication. The overall performance is T=50+/-5% while R=50+/-5%. So R/T should be between 0.905 and 1.105.

This power ratio depends also on polarization. According to thorlab website, p-pol should be closer to 50:50. We measured the power ratio relationship with polarization for one mirror. The result is shown in the attached figure. It seems there is relationship between polarization and power ratio. But it is small dependence. We can also see this mirror is still within the error range of power ratio provided by thorlab. But it is not as Matteo suggested.

Then we changed it to the second mirror. Then the power ratio becomes R:T=607.5/615.4=0.987. This is much better.