Collaborative Research Stories
"Controlling Laser Frequencies with Atomic Transitions"
Jon DesChane '12 of Wauwatosa, WI, Physics & Math Majors
Faculty Collaborator: Dr. Erik Brekke of the Physics Department, Atomic Physics & Optics Research Specialist
Diode lasers provide a cheap and easily accessible source of low power
laser light, but require external means to control the range of frequencies
that are emitted. Atomic vapors provide an excellent means to control these
frequencies by observing the absorption of the laser through an atomic sample.
Two techniques have been accomplished to eliminate Doppler broadening and
control the frequency of a home-built diode laser system. One method uses
the saturated absorption of single photon transition in Rubidium, and another
uses a two-photon transition. The control demonstrated will be essential
in pursuing future laser-atom interactions.
We are able to control the frequency of the laser in a
couple of ways. We are able to narrow
the broad range of frequencies by adjusting the grating feedback. After that, we can also move the entire
grating feedback closer or farther away from the laser in order to adjust the
actual frequency of the laser.
A common challenge in any atomic physics experiment is
Doppler broadening. This is when the
movement of particles in a cell causes the laser to be absorbed over a broad
range of frequencies. Since there are
many particles moving at different speeds in the cell, each particle may
identify the incoming laser frequency differently. This would allow a range of
frequencies to excite these atoms, depending on their speeds. It is our goal to
eliminate the effects of Doppler broadening so we can identify which specific
laser frequency excites the atoms at rest.
The arrival of Dr. Brekke in the Fall 2011 presented the
opportunity to research in his field of interest, which is atomic optics. Not only did I have little knowledge about
atomic physics to begin with, but I hardly even knew who Dr. Brekke was. However, Dr. Michael Olson assured me that it
would be an excellent opportunity to work with a professor and his research
Since then, I have gained an immense amount of knowledge
about the subject matter. By reading
articles and journal entries from previous researchers and by using instruments
that most people will never get to use in their lifetime, I was able to learn
in a very efficient manner. The objects
and tools I used on a daily basis were very specialized (and expensive), yet I
was given the opportunity to use these to maximize my learning experience.
Physics, in general, is a subject that truly has no borders
and working in this lab proved to be no different. As a physics major, you are showing people
that you are able to solve complicated problems, which is a good skill to have
in all areas of study. In the research
lab, the same situation presented itself; there were many times where I needed
to think through a certain problem, whether it was mathematical or technical. When I come across a complex predicament in
the future, I know I will have the confidence to work through them because
being a physics and math major along with doing research properly prepared me
for challenging situations.
The research I have done over the last year will serve as a
fundamental building block for future student researchers at SNC. The experiments I have set-up in the lab will
be used for others to create other experiments.
It is exciting to think that this lab will be an ongoing lab for many
years to come and that I was the first student to be given the opportunity to
participate in such an amazing learning experience.
After the two-photon spectroscopy experiment, future
students will continue to build onto the set-up in hopes of observing four-wave
mixing. A series of posters was
presented at multiple events to give general background information about the
research I participated in; however, there are no publications or performances
I have really enjoyed have Jon work in the lab with me. As this is my primary research, we have
worked alongside each other throughout the year, which has enabled Jon to learn
quickly and have direct interaction with me throughout. This line of research works very well with
student collaboration, as it can be divided into smaller projects, and it has
worked well as Jon has had particular optics to assemble, and been able to
investigate atom/light interactions with them.
In addition, I have been able to help him get a better understanding of
how to find information about research in relevant papers are journals.