Advanced Optics Lab Development

Marty Baylor, Physics and Astronomy, Carleton College
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Summary

This activity contains two open-ended labs for an upper-level undergraduate optics course: an acousto-optics lab and a diffractive optics lab. Through these labs, students can explore how an acoustic wave can cause light to diffract and how a lens can be used to take the Fourier transform of an aperture.

Learning Goals

In a typical lab science, students are using the lab to explore topics they are currently learning about in class. The reason I am excited about Advanced Optics is that it is taught after students have had the Classical and Quantum Optics course. Therefore they have all the background for the lab before they take the lab course and the lab can focus on application and integration of the knowledge from the prior term's material. One goal of the course is to give students hands-on experience in designing, assembling, and aligning optical systems. After 10 weeks of working with opto-mechanical equipment, students should have a better understanding of the design criterion necessary for making precision measurements. An additional goal is to give students the flexibility to perform experiments of their own design based on their interests. Finally, I expect the students to develop good lab notebook skills.

Context for Use

These activities work best for junior or senior level physics majors who are ready for activities that are more open-ended and less prescribed. In the course evaluations, the students really enjoyed the opportunity to explore topics on their own with the availability to come to the faculty member for guidance. The labs are designed for students working in groups of two, where each student took turns writing in the lab notebook and working with the optical set-up. Although the activities worked with 3 students, the third student was generally not as engaged as the other two. These labs were part of a lab course taught in the term after the lecture course; however, these labs could also taught as part of a lab associated with an upper-level optics elective. The diffractive optics lab assumes the students are familiar with Fourier transforms.

The cost of the acousto-optic modulator and the driver were about $3000. The cost of one spatial filter, objective, and pinholes, and mounting supplies is about $1200. The selection of slits and apertures will be above and beyond this. You can be create about the objects to keep costs down. For example students can use a strand of their hair, the edge of a ruler, the mesh of a piece of sheer fabric or a geology sieve, a blood smear slide from the biology department, etc.

The photonics project, which is designed to be completed over a 10 week term, could be integrated into either a lab course or a lecture course. The project involves library research and contains a written and oral component.

Description and Teaching Materials

For the acousto-optics lab, the teaching materials are in the form of a lab handout (AOM Lab Handout (Acrobat (PDF) 55kB Jul12 12)) for the students as well as notes my personal lab notebook (Lab Notebook (Acrobat (PDF) 308kB Oct31 11)) for setting up the lab and several of the measurements performed. The students are given reading from the textbook to refresh their memory on the topic of the lab. Although the material was covered in the PHYS 344 which is a prerequisite for the lab, the reading is designed to refocus their attention on this material. Next students perform a series of problems (Pre-Lab Exercises (Acrobat (PDF) 28kB Oct31 11)) related to calculations they may need to do as part of their data analysis or calculations that allow them to set-up the lab with the appropriate considerations (e.g., appropriate angle of incidence for bragg matching a particular acoustic frequency). Next the students choose a particular aspect of the topic to study with the materials available. Some guidance is given to the students, however the students are also allowed some flexibility to choose experiments and measurements.

The diffractive optics lab is completed as part of the Fourier optics lab. The teaching materials are in the form of a lab handout (Diffraction Optics Lab Handout (Acrobat (PDF) 166kB Jul12 12)), a supplemental handout on the theory behind spatial filtering (Newport, Projects in Optics Workbook, product number 16291-01, pages 34-35), and pre-lab exercises (Diffraction Optics Pre-Lab Exercises (Acrobat (PDF) 24kB Jul12 12)). The spatial filter part of the the lab is set-up and mostly aligned for the students before the lab because the initial set-up can take hours for individuals who are not familiar with this technique. The student adjust the spatial filter to optimize it. A wide selection of slit and aperture patterns are provided for students to explore during this lab. The students try to determine/verify the size of the slits/apertures. Chose to take images of their patterns for their lab notebooks.

The Photonics Project provides an opportunity for students to explore some area of optics that they are interested in, research the topic, present it to their peers in multiple forms, and also present their topic to a non-physics peer audience. These are all activities that professional scientists must engage in as a regular part of their activities. There are 3 parts to this project: a paper and 30-minute presentation geared towards their peers in the class and a creative project designed to present their topic to a non-physics peer audience. A non-peer audience includes, but is not limited to: college students who are not science majors, college-educated educated adults who are not necessarily scientists, middle or elementary school students, high school physics students. Included with this activity is a description of the activity (Photonics Project Description (Microsoft Word 33kB Oct30 11)), a grading sheet for the paper (Paper Grade Sheet (Microsoft Word 2007 (.docx) 14kB Oct30 11)), a peer-evaluation form for the class presentation (Presentation Peer Evaluation Form (Microsoft Word 2007 (.docx) 13kB Oct30 11)), and a gradesheet for the evaluation of the class presentation (Presentation Grade Sheet (Microsoft Word 2007 (.docx) 12kB Oct30 11)), and instructor notes (Photonics Project Instructor Notes (Microsoft Word 29kB Oct30 11)).


Teaching Notes and Tips

The labs are designed to take 4 hours each. The photonics project progresses over 10 weeks.

Assessment

There are several ways that I assess whether students are meeting my learning goals. First the students complete a pre-lab graded exercise the helps them begin the think about the concepts related to the lab. These pre-lab exercises review course material and also prepare students to think about the engineering task required to complete the lab. During the lab itself, students create and assemble their set-ups and they complete a task that requires integration of knowledge. I check the students out of the lab and so I know if they complete the task and how well they have completed the task. I review and grade their lab notebook detailing the process they used to go through the lab exercise. Finally I will ask the students to asses how whether they felt they achieved the learning goals set forth at the beginning of the course.

References and Resources

Crystal Technology provides application notes for its 3000 series modulator that give very practical information for aligning an AOM and summarizing important parameters. http://www.crystaltechnology.com/docs/AO_Modulator3000_appnote.pdf

The science librarian put together resources for students doing research on their Photonics Project. The website has links to journals or other library resources related to optics.
http://gouldguides.carleton.edu/phys344