NAOJ GW Elog Logbook 3.2
Yesterday I did beam characterization of infrared beam along west and south edge of bench. The first attached figure is along the south edge, which is also the beam directly goes to PR chamber. Actually we did a similar characterization before, see elog634. This time the result is similar with before.
The second attached figure is along the west edge, which is after the first lens on the rail. We will put a combination of lenses to make the beam meet the requirement of IR mode cleaner. According to the measurement result, we have the initial beam information. We also know the target beam information, which comes from calculation of IR MC configuration. Then I use these information did the simulation in JamMt by using mode matching assistant. I choose one I prefer showing as attached figure 3 and 4. I checked they are seating at place between lens and first steering mirror. This means it should be a reasonable solution. Also this solution doesn't use small focal length lens.
The detailed calculation is also attached in PDF file.
Today after I installed the first lens, I check the beam parameter. It is quite far from the simulation. Then I found the reason maybe I didn't use a correct distance before. (Also here I found 200mm lens disappears)
Then I measured the beam again and used the lens we have to design the telescope. However I cannot get any result.
So I decide to remove the first along the west edge. Then I peformed the measurement. Before do that I aligned the beams to make them flat and go through the center of the lens and mirror as well as possible. Then I measured the beam agian. The result is w0 = 850um, z0 = 3.05m(relative to the 0th hole of west edge of the bench).
Then I use the result and mode matching tool in Jammt(by using the lens we have, I just update the lens situation today). The target beam parameter is calculated last time. It is w0 = 390um, z0 = 0.8875(relative to the 0th hole of the west edge of the bench).
The simulation result is f = 250mm @ z = 0.484m, f = 75mm @ z = 0.795m. I also check this result with the optical layout we have. It doesn't overlap with the mirror we have in the optical layout.