Lab 5 Fringes - Cell Phone Photos

Here are 3 sets of fringes from the Lab 5 microscope slide experiment, one from each team's successful layout. An incident beam I reflects first off the front surface of the slide creating one reflected beam, and then off the back surface, creating another. These travel almost in the same direction, but not quite, due to the small tilt of surface S1 with respect to S2. This tilt is there because the slide surfaces are not perfectly parallel. The number of fringes and the size of the illumination spot on the slide measure the tilt angle, typically a few mrad.

Reflection geometry. Each reflection is about 4% as intense as incoming beam I. Not shown is the transmitted beam T that continues downward to the left.



The fringe orientation is due to the wedge orientation. In lab we rotated a slide to see that the "clock" angle of the fringes is tied to the slide, not to the rest of the optics.

We also tested what would happen if we overlapped the fringe pattern from one experiment bay on top of the beam from another experiment bay. Additional fringes or no additional fringes? At first sight we didn't see evidence for additional fringing - the pattern looked like the straight addition of the 2 fringe patterns rather than the interference of those 2 fringe patterns. Remember that the number of fringes is related to the angle between the two beams, with about 5 fringes per mrad. The two beams were incident at an angle of several hundred mrad, so there were of order a thousand of these new fringes across the pattern -- too many to resolve since there's more than one fringe per camera pixel. So we didn't see much new. If we had inserted some clever optics to overlay the two beams with a small, mrad sized, angle between them (like is done when you use 2 stacked slides), then what would we have seen at the detector/screen?

Lab 6 Prep Package Available

Lab 6 Prep Package
During Lab 6 I will review lab notebooks for feedback. Also, we will begin designing our precision tip-tilt stage for the precision interferometer experiments. Finally, there will be open lab.

Lab 5 Materials Available

PDFs for Lab 5 are available:
Lab 5 Plan of the Day
Lab 5 Microscope slide interference and metrology
Self-Assessment

This is the material that we will cover in the lab. It is different from the preparation package in the previous post. Do not confuse the lab materials with the preparation package!

On Wednesday the lab will include notebook review. Be sure you are all caught up with your notes and come ready to go over them with me for feedback on your notebook practices.

On Wednesday we will also begin designing precision stages for our Michelson interferometer experiment.

And, with luck, I will have sent some post drawings to the shop for fabrication. The luck being: there are good drawings to send on Monday, and the 1/2" stainless rod stock has arrived from McMaster-Carr.

Lab 5 Prep Package Available

This is the work to complete before class. I may post the lab notes prior. But they are not the preparation package. Preparation packages contain exercises for you to do and record in your lab notebook. Think of them as homework.

Lab 5 Prep Package ... in which you will explore the small angle approximation, analyze your diffraction pattern data, and generate a mechanical drawing.

Lab 4 - Fringes and Interference

Working at the table with Cornell Plates to generate diffraction and interference patterns. Several captured with cell phone cameras are below:

Double slit interference pattern

Airy disk from a round aperture made with a diaphragm

The camera is now working, this is its first fringe from #2 double slit on a Cornell Plate. Below is a slice through the intensity profile that could be used for numerical work:

Lab 4 Materials Available

Note: the Lab materials are what we do in the lab. The Prep Package, which was posted earlier, needs to be done before lab and recorded in your lab notebook.
Lab 4 Plan of the Day
Lab 4 Materials
Self-assessment
On self assessment please record if you want to attend and will commit to open lab on Friday afternoon. I will begin designing a precision mount with those interested. Or play on the table with the optics.

Lab 3 - Proud

Paul, Julian, Cy and Daniel just after finishing their Lab 3 layout of a beam conditioner that reduces the laser beam divergence to less than 0.5 mrad and expands the beam 10x. Nice job guys!