# Journal

## November 5, 2011

Yesterday I met with Dr. Noe at length, and discussed the starting point of my reserach at the LTC. Among the things we talked about was problem 10.5 problem from Hect's Optics, 2nd edition. This problem asks us to show that several lens arrangements are equivalent, and to also design one more equivalent arrangement. This problems requires a deep understanding of lenses and diffraction.

In addition to this, we discussed a better derivation of the cos^2(y) relation in Young's double slit experiment. The typical "meeting at infinity" (the screen being infinity) isn't satisfying. Dr. Noe introduced me to a new way of thinking about a lens which is a phase shifter. I am curious about the "adding wave" method of deriving the cos^2 relation, and also about continuing the Taylor approximation to high orders.

We observed an Airy disk by shining a green laser through a 250 micrometer aperture. To our surprise, we observed a linear obstruction pattern. Sure enough when we looked at the aperture through a magnifying glass, we found a hair! We switched to a smaller aperature and observed the desired Airy disk, a bright maxima surrounded by concentric rings of minima and maxima. Although the quality of the laser wasn't good, the center bright spot of the Airy disk was uniform. I learned this is the principle behind a spatial filter.

Lastly we discussed some previous students' work on diffraction. Something I should look at is a Mathematica script to show the diffraction pattern for a tiple slit experiment.

## September - October

In mid Septermber Dr. Noe showed me around the Laser Teaching Center, introducing me to the projects of current and past students. One was Carrie's AOM, another was David's diffraction experiment with optical vortices. He also showed me the project of students who spent time at the LTC during the summer, but will not be returning. One such experiment was Bolun's study of evanescent waves. We also talked about different ideas that I could pursure, including tuning the YAG laser, finish where Bolun left off on his study of evanescent waves or investigating some unexpected results of David's experiemnt.