Lab 2 - 30 September 2009

First off, how cool is the sign on our lab door?


(not the fire extinguisher part)

Lab 2's materials are at these links:

Lab 2A - Optical Table Fundamentals and Component Placement
Physics 492 Self-Assessmment

For convenient downloading you'll need a free Google account. Google is not evil, just demanding.

The class was about the table and putting components on it. We started by getting used to working in gloves with our tools and building up some simple mount bases, then placing them at assigned locations. We finished with full builds of several beam splitters from parts still in their wrappers. A quick design conference between the two teams divided up the table and reached agreements on where beamsplitters will go to provide beam distribution to three separate experiment areas. Here is one of the beam launchers at its assigned location, performing its function. Can you see a piece of Doug?

What, you may ask, is the white and blue stuff? The white is some lens tissue that came with the beamsplitter in its box being used as a compliant load-bearing surface for the beamsplitter to sit on. The tissue in turn is taped down with some small cut pieces of blue painter's tape to keep it from moving as the glass is placed. We don't want metal to touch glass if we can avoid it. Without the paper, the glass would sit right on the anodized aluminum shelf, and very high stresses would be developed at the three (why three?) contact points, leading to microscopic damage. But the paper is compliant - it deforms somewhat - so the load through the glass to the shelf is distributed over some area. It is easy enough to protect the glass in this way (this time!) and a good habit to always be thinking about how the glass is being touched. The beamsplitter cube is held in place by a nylon-tipped set screw threaded through the upper shelf which compresses it against the tissue paper. This set screw must be only snug and not turned down tightly - again to avoid possible damage to the glass.

The layout design conference was an exercise in parallel coordinated work by the two teams. We don't have time (nor inclination necessarily) for everyone to do everything. We need to do some parallel processing. In this case each of the two teams sent 2 representatives to the whiteboard to agree on how to divide the table up and arrange how beams would be delivered to several experiment areas with the beamsplitters. The result:


Lab 3 prep package will be up shortly. Part of the prep will be to watch one of Feynmann's videos. The video itself is over an hour long, so be sure to schedule some time for this. The video is online and streams to your computer like YouTube. Also there will be a narrative with questions for you to work related to the video.

Next week we'll take a little time exploring the concepts in the video and relate them to what is happening on the tabletop.

Michelson Interferometer

After the scheduled class time was over, some of us went over to another lab to take a look at a Michelson interferometer. This is an iPhone photo taken looking upstream at the fringes formed by this interferometer. Everyone was able to safely put their eye at this location and see the fringes for themselves. Safe because the source was an incandescent light with a narrowband filter and a diffusor screen - never look upstream at a laser. We had a lively discussion on how it is that "which-way" ambiguity having to do with the 2 arms of the interferometer and small tilts in the end-of-arm mirrors give rise to these fringes. For example, the presence of 7 fringes means that the two mirrors are misaligned by 7/2 wavelengths from ideal - each half wave gives one fringe - or by (7/2)*500nm = 3.5 microns.

Lab 2 Prep Package Available

Lab 2 Prep Package

Instructions: do the work in the package, recording in your lab notebook. Be prepared to verbally report out at the beginning of class Sep 30.

Lab 1 -- 28 September 2009

PDF's for the first lab session are available:

Lab 1A - Introduction to Physics 492 
Lab 1B - Lab Safety & Fundamentals
Lab Self-Assessment

A simple demo is on the table reproducing Young's double slit experiment. First the laser beam is expanded and collimated through 2 simple lenses to form planar wavefronts / straight rays. The expanded and collimated beam then passes through a glass slide with a double slit inked on it. Then the beam propagates to the end of the table where it illuminates a simple screen to show the classic interference pattern.




Photos taken with an iPhone in low light - handheld and with its autofocus algorithm trying to sharpen edges so they are a little blurry.

Physics 492 Course Description

PHYSICS 492: Advanced Optics Laboratory

Instructor:  David Van Buren

 

Course goals:  (1) gain hands-on experience with optical components and their behaviors; (2) learn your way around an optical table and laser source; (3)  become familiar with optical experiment design considerations; (4)  construct end-to-end optical systems from source to detector; (5) introduce fiber optics concepts; (6) demonstrate elementary quantum optics principles; (7) attain proficiency using online and downloadable tools for technical work.

 

Topics will be chosen from:

Safety and care in the optical laboratory
Behavior of basic optical components
Optical materials and mounts
Detectors, cameras, and image data
Optical experiment design tools
Environmental considerations for optics experiments
Optical tolerancing and performance error budgets
 
Beam expander demonstration
Young’s double slit experiment
Applied diffraction
Fiber optic demonstration
Quantum optics table-top apparatrus
Interferometry and fringe detection
Fourier optics demonstration
Wavefront sensing basic experiment

Prerequisites:  Curiosity and a desire to work in a laboratory setting.  Familiarity with introductory university optics. 

 

Instructor:  Dr. David Van Buren (PhD 1983 UC Berkeley) is an Architect for optical systems at NASA’s Jet Propulsion Laboratory.  He has worked on astronomical telescopes from an amateur-class 6-inch backyard telescope to NASA’s upcoming flagship 6-meter James Webb Space Telescope.  He has also worked on a range of optical interferometers from handheld demonstrators made with household items to the spaceborne SIM Lite, which will be used in the search for extrasolar earth-like planets.