NAOJ GW Elog Logbook 3.2
Logan, Michael
I showed Logan the use of the ATC clean room and the experiment setups we have there.
I showed and supervised the use of the Coherent Beam Master BM-3 UV beam profiler. Although I dropped and broke the included NG9 ND filter (0.5% transmission). The manual says to use below 5 mW and 200 W/mm^2 without the filter so it's fine in this case (3.8 mW).
We measured the beam profile from the s-polarized beam split off in the Taiwan/Korea experiment setups. I thought this beam was to be collimated at 2.3mm over some distance, but it doesn't maintain that size for long and turns out to have a waist of ~ 200 um radius about 30-40in from the PBS. So I also question a bit the Taiwan fiber SHG beam size, but we can look at that later. I tasked Logan with fitting the beam shape and redetermining the mode matching elements for the OPO.
We tried to calculate the beam profile but it seems that the beam divergence going in does not match the beam divergence going out.
i.e. approaching the beam waist, the beam shrinks ~ 100 um diameter per screw hole, but going past, it increases only ~ 50 um per screw hole.
We will look again for the source of this odd behaviour.