Research Journal

End of REU Program

I did eventually manage to lock the laser, but only with limited success. In the last week of the REU program, I first managed to lock the HeNe laser using Matt Whitrock'system utilizing the Princeton Applied Optics Pre Amp, latter I achieved a stable lock using the Op-Amp circuit that I had designed. This circuit worked very well one night, but did not work the next day. I believe the difference was in the room temperature - as it was several degrees warmer on the second day. I managed to take enough data to give a decent presentation, but I wished I had had more data gathered for the presentation and paper and more time to work on this project once I had finally gained some momentum working on the stabilization system. Overall, I enjoyed the REU program. I met some wonderful people and learned alot in areas of physics that I hadn't had much, if any, exposure to. Thank you to John Noe, Marty Cohen, and Harold Metcalf for all their help and support during this internship. Also, thanks to Karen, Mike, Hamsa, Matt, Scott, and Victor for all the fun and learning that we shared this summer.

21 July 2006

I have made a good deal of progress this week on the laser mode locking. For a while, I was struggling to get the op amp circuit that I need to use working. This afternoon I decided to try a different op amp chip from the one I had been using and it worked! It turns out that the op amp chips I had been using were bad. But now that I have a working differential amplifier I should be able to achieve thermal feedback next week. I also spent time this week learning how to take data using a computer and Measurement Computing software. I took data plotting the intensity of the two modes versus time as the laser heats up. I took data for about two hours. I have no way of taking temperature measurements with the computer as well, so I took those measurements by hand, going over to check the temperature every few minutes. It was interesting to see the time for one cycle increase as the laser heated up.

14 July 2006

This week has pretty much been devoted to learning more about electronics. For my project, I am going to have to build a feedback circuit to control the amount of heating to the laser. While I have had a lot of the theory of electronics, my experience actually building circuits is somewhat limited, so this week I have spend a lot of time building circuits. One of my goals has been learning about and how to use operational amplifiers or op-amps. Next week I hope to get the feedback heating system for the laser working.

Another accomplishment this week has been making a working Mathematica simulation of Young's experiment. With some help from Dr. Noe, I wrote some Mathematica code to plot the intensity of light on a screen that shows the interference pattern from multiple slits. On my main page there is a link where you can download and run this simulation if you have a copy of Mathematica.

7 July 2006

I have finally decided on a project! Following Dr. Noe's suggestion, I am going to work on stabilizing an internal mirror HeNe laser that is here in the lab. As the laser heats up, the cavity length changes which affects what wavelengths are emitted rom this laser, they happen to be orthogonally polarized. To stabilize the laser, it will be heated to be slightly above its normal operating temperature. The beam will be split according to the polarization of the light, by comparing the intensities of the two beams and then using a feedback mechanism to control the amount of extra heat given to the laser cavity. I spent a while yesterday reading on the internet and in journal articles about ways in which this has been done in the past. I also looked at Matt Whitrock and Stephanie Lim's work, as they both previously worked in the Laser Teaching Center on this laser. I am looking forward to getting started on this project.

29 June 2006

On Monday four high school students joined us in the Laser Teaching Center. They will also be doing their own projects in the lab. This week, in order to help get everyone up to speed on some basic topics, Karen, Mike, and I are all giving presentations about different important topics. I gave my presentation on Tuesday about Complex Numbers. A link to a copy of my presentation can be found on my homepage. Yesterday, Karen talked about light as a ray and basic optics concepts such as converging and diverging lenses and mirrors. Overall, I think that both of our presentations went well. Mike will be giving his talk this afternoon. He will be talking about interference and diffraction of light--seeing as how he is an optics major we gave him the hardest topic.

I still have not settled on a project to work on but I am hoping that I can choose something very soon. Until then, I have spent a good bit of time learning about optics through reading books and playing around with the different laser and optics demonstrations in the lab. We have spent a good deal of time playing with corn syrup and polarized light. Because the corn syrup is optically active--that is it rotates optically polarized light--when we put linearly polarized light into the corn syrup and then look at the light coming out through another linerar polarizer, a variety of beautiful colors are seen. The color depends on the depth of the corn syrup. When asking about what causes these colors just now, Dr. Noe immediately thought that measuring this effect would be a good warm up project for somebody. I might take him up on that offer and possibly work with one of the high school students on this mini-project.

21 June 2006

We (Karen, Mike, and myself) have been working in the Laser Teaching Center for a week. So far, I do not yet have a project to work on, but I am learning alot. We have had several lectures from Harold Metcalf on laser cooling, explaining the concepts and physics involved in laser cooling. Yesterday, Reinhold Blumel, a physics professor at Wesleyan University came and gave a short talk about the infinite square well potential problem. His research involves using classical mechanics to describe quantum phenomena. He claims that classical mechanics can be shown to work. We have also toured two of the labs and seen some of the projects that the graduate students are working on. In the laser teaching center, we have worked on reviewing and understanding basic optics concepts, played around with fun optics demonstrations, and worked on learning linux and html. Next week, four high school students will be joining us in the laser teaching center, and we have begun preparing some presentations for them. I will be giving a talk on understanding complex numbers and their application to modeling waves.

Stephanie Golmon
June 2006
Laser Teaching Center