This week I met my advisor and the other REU students, and I got an introduction into my project. It is our groupís beam time, so I mainly learned about what we do in lab and did a lot of reading. We have lectures from Dr. Weaver that can get quite interesting.
Ryanís design for our t-shirt
This week I worked with one of my grad students to set up a saturated absorption arrangement. We need these to lock our lasers to certain frequencies. I also started working on a shutter device that I will use to switch my laser on and off. We started an electronics class this week, covering just some basic stuff that we should know in the lab. We also had a shop class to become familiar with the shop tools.
I continued work on my shutter, and so far things are going pretty well. The circuit that I am building has a couple of components that we are having some trouble finding. The shutter design and circuit was adapted from Robert Scholtenís design, which can be found here.
My shutter circuit, mounted in the box
This week I completed my shutter, now I just want to check how fast it is. I also started looking into how I am going to do the optical set-up for my experiment. It will involve using an acousto-optical modulator (AOM), so I have to learn more about what that is and how to use it.
My completed shutter
I continued working with my set-up this week, but our group has beam time again so I canít block my laser beam. Instead, I am working on the connections for my AOM and adjusting the power into the AOM. The voltage controlled oscillator (VCO) that I was planning to use to control the AOM doesnít appear to be working properly. Iíve also had to have cable made for my connections, because we do not have a lot of SMA to BNC cables around. Instead of the VCO, we substituted an oscillator generator and used that to try to line up my AOM.
This is a mot. It is the brightest speck in the middle, and is bright due to fluorescence.
I encountered many problems with my AOM again this week. I went back and looked at the VCO that wasnít working properly and found another VCO in the lab. I compared how these two were working, and it appears that the first VCO is dysfunctional. Now I am working to use the second VCO. I also received an email from Dr. DePaola that mentioned a mixer as part of the VCO connections, and I was unaware that I needed one. It turns out that it is very helpful.
Once I had all of the equipment necessary to get the AOM working, I finally got it lined up and looking good. There were several problems with space on the table for alignment of my lenses, but I managed to re-work the set-up to make it fit. Now I am starting to set up the fiber optic cable that I need to transfer my beam to the MOT, but once again it is beamtime.
This is the mess that has my electronics for the AOMÖ
Beam time ended on Monday, but we were able to keep the beam until Tuesday morning. Then I began work on lining up my fiber. This turned out to be harder than we expected. I had to redo my set-up again to make sure everything would fit nicely. The fiber launcher that I am using is a bit tricky to line up, so I learned how it is adjusted as I went. But I did eventually get it. I also started to line up my beam through the MOT. Right now the camera that I am going to use for imaging is still being worked on for timing and other technical things. So I am using a different camera to check my alignment.
This week I rearranged my set-up to make it more accessible. I also was able to get a decent image of the beam through the trap, but not able to image the mot. The beam out of my fiber is spatially ugly, which is not what we expected. We think that the fiber may be dirty or damaged, but will fix this in the future. We have also discussed a couple of different timing mechanisms for imaging. Iíve also done work with my final report, since we are giving those early next week.
This is a picture of my probe beam that goes through the mot. It is a little difficult to see, but is the somewhat bright circle.