R&D (FilterCavity)
YuhangZhao - 15:10, Monday 09 March 2020 (2068)
Measurement of QPD shot noise with different beam size and different power(second measurement)

We measured again with 5mW green power, but this time we make the beam smaller to see if it will decrase or not.

The result is that shot noise will decrease if the power density is higher than 47mW/mm2.

There is a discrepancy between this measurement and the one measured last time(entry 2067). I think the reason is that, the beam size is highly related to position. And this time we removed QPD and we may put it back to a slightly different position. Then it leads to this discrepancy.

We need to use a more robust telescope if we want to have a more precise measurement.

Images attached to this report
2068_20200309071659_figure1.png