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ABOUT THE LASER CULT

LASER CULT courses are very different than many other courses taught in engineering.  This course is a lot more like "real life" than other courses you may have taken and will prepare you better for what you will encounter in your career.  This course helps you build a portfolio of work you can talk about on job interviews that will help distinguish you from other candidates for the same position.  Also you are given much more freedom than in other courses.  Be warned that people who do not enjoy new situations and challenges may not like this course- it will require initiative and independent work!

Besides building projects, student teams are encouraged to collaborate rather than compete.  Here is one student sitting in front of one of the white boards in the LASER CULT combined  lab/classroom during  an informal study session for the final examination.  All student have 24 hour access to all the LASER CULT facilities.  This class is completely open-source:  all exams and past project reports are available on-line to help students study.

Below are descriptions of the two courses that teach photonics in the undergraduate electrical engineering program at OSU

The first course, basics of optics and photonics

The first course in the LASER CULT sequence is ECEN4823, "Engineering Optics".  This course covers two topics that are useful to all engineering students, how to form images and measure how "good" they are, and the basics of spectroscopy, or how to identify materials by their optical properties.  Creating an image is the first practical use of optics, and fall under the heading of geometrical optics, or treating light as geometrical lines.  Spectroscopy is one of the areas where electrical engineering intersects medicine, chemistry, biology, and forensics. 

In the first project student teams work on is to design, build, and measure a working zoom lens.  A zoom lens is an optical device that keeps an image in focus, but allows the user to change the size of the image (magnification).  To build a zoom lens students need to learn how to design multiple lens systems, how to model those systems using numerical tools, and how to measure the effects of aberrations, or degradations to the image formed.  The figures below show some of the designs and measurements from zoom lenses student teams have constructed:

The figure above is a schematic drawing of a simple five element zoom lens and its implementation on an optical table. This shows the analytic solution that demonstrates that the system is actually working as a zoom lens implemented in Matlab.

 

 
Here is a ray tracing model of the zoom lens implemented in "Optics Lab", a sophisticated modeling package for optics. The image to the left is one measured by a student zoom, while that to the right is a fals color image in Matlab that is used to measure modulation transfer function.

The second project involves building a device to detect fluorescence of small amounts of dye.  This device can be used either to detect contamination in water supplies, or to detect small traces of blood at a crime scene.  Important issues in this type of device--a fluorometer--is to be able to sensitively detect light of a certain wavelength, calibrate the detector to know how much of a substance is present, and be able to distinguish "false positives" from real signals.  Teams of students build these detectors, calibrate them, and are given samples or forensic evidence to test.

Schematic diagram of one team's fluorometer showing path of light signals and electrical signals. A high concentration sample of dye used to calibrate the fluorometer.

The second course, technology of lasers

The second course in the LASER CULT sequence is ECEN4813, "Optical Electronics".  This course teaches the fundamentals of lasers through two projects

In the first project teams of students design and build "optical tweezers".  Optical tweezers use the forces created by photons to trap and move small particles.  This is similar to a "tractor beam" on Star Trek, but on a microscopic scale- the forces generated are piconewtons.  In order to design optical tweezers it is necessary to understand how to focus laser beams down to very small spots.  To do this the class covers laser beam propagation, and how to engineer the properties of a laser beam using optics. 

This is a very difficult project, but no team has ever failed to trap at least some particles.  The figures below show some past results from this project...  You can watch a movie of working optical tweezers on the link below.  You'll see small particles dragged by a spot of light.  This movie recorded by a student team to demonstrate how they can drag the 3 micron spheres around.  Watch particles being moved...

The upper photos show how a particle is moved by a beam of light.  The lower two photos show how a team of students trapped blood cells and moved them to a square pattern.

This is one of the prototype optical tweezers constructed by student teams.  This photograph is taken directly from the teams project report.

Here is a team of students standing by the optical table on which they built their optical tweezers.  From left to right they are Jacob, Anna, Aziz, Beenu, and Chris.

The second project is to design a working frequency doubled diode pumped solid state laser.  This project is quite difficult and requires all the knowledge and skill that students gain in this course.  In this project a diode laser is used to optically excite a Nd:YVO4 laser crystal, which produces light at 1064 nm.  A laser cavity is used to trap this light, and produce a laser.  By inserting a KTP frequency doubling crystal in the laser cavity the light is converted to 532 nm- a brilliant green color.

About 60% of the teams get this project to work, the major factor in success is the ability to work together as a team rather than as a bunch of individuals.  Another factor for success is being able to model the behavior of the laser cavity.  This course places a lot of emphasis on using Matlab--a numerical simulation tool--to model systems of coupled differential equations.  The figure below show some of the results that student teams have achieved:

A schematic diagram of one of the DPSS lasers. Here is a linear cavity laser one of the teams built.

 
A closeup view of green light being produced by the DPSS Output shining on a business card The set of coupled differential equations used to model laser behavior numerically.

The Oklahoma State University Photonics Laboratory is supported through a 
National Science Foundation Course Curriculum and Laboratory Improvement Award.    
The information on this page may be distributed freely.