Second time testing of grating with infrared

After talking with Matteo, I found the last measurement was needed to be improved. Firstly, the rotation direction should make sure that the incident direction is against the arrow direction marked on the edge of grating. Secondly, to find a good place to do measurement with enough times. Thirdly, to check the polarization of infrared beam. Fourthly, we also need to know the diffraction angle.

So I did experiment today. Fortunately, I found a PBS without costing a lot of time. Although yuefan told me that the most consuming part of job in TAMA is finding something.

Then I improvised the testing set-up. I found most of the light is reflected by the PBS. However, I didn't know the ratio between s and p polarization should be around 1000, which I learnt from Matteo latter on. But this can explain why the energy doesn't conserve if I put half-wave plate in-between. You can refer to attached picture 1. I will take the picture of weak light and measure it next time. As Matteo suggested, the weak signal will have less fluctuation which is important for measurement.

The power evolution is shown as attached picture 2. The attached picture 3 is about the diffraction angle.

I will do the measurement of green soon and compare it with this one. Before that we will refine the alignment of some wave plates.