February Leading Expert:
James J. Coleman,
Intel Alumni Endowed Chair in Electrical and Computer Engineering
Graduate students Katelyn Tobin, Victor Elarde, and Varun
Verma with Professor Jim Coleman in the Semiconductor
Laser Laboratory.
Q: What is your area of expertise?
A: Semiconductor lasers—the optical component
in fiber optics telecommunications systems [and] CD and DVD players. Semiconductor
lasers are also used in industrial applications like high-precision
laser welding, things like that. There are lasers all around
us.
Q: Why did you become an electrical engineer?
A: I got a short-wave radio when I was 11 or 12 years
old, a second-hand short-wave radio. It was broken, actually
there were tubes burned out in it. Two things happened. One
is, I managed to get it fixed by finding the replacement tubes. And
the other was I turned it on and was just amazed that I could hear
the BBC in London and Radio Prague and Radio Moscow and things like
that. So the combination of that ability and this technical box
of stuff just captured my attention and has ever since.
Q: Tell us about your career.
A: I came to the University of Illinois and received
my bachelor’s, master’s, and PhD. Then I went to
Bell Laboratories in New Jersey and worked on lasers for telecommunications
systems. Then I went to Rockwell International in Southern California
and worked on lasers for defense systems as well as solar cells and
other kinds of photonic devices. And then I came back to Illinois
and have worked here for many years doing research and development
on semiconductor lasers.
Q: You’ve had a long affiliation with
Illinois. Why?
A: I’m originally from Chicago. I knew
a little bit about Illinois. Illinois offered me an excellent
engineering school, although I didn’t realize how good the engineering
school was at the time, for a price that a city boy could afford. It
was quality and value that brought me to Illinois originally. And I
suspect it still brings people here.
Q: Tell me about a research accomplishment
you’re proud of.
A: We’ve had a lot of wonderful students come
through the group and we’ve gotten a lot of stuff done. But
if you asked me to pick the one thing that had the most impact, we
made some critical contributions to a material structure called a “strained
layer,” it’s part of a laser, in the late 80s and early
90s that has turned out to be a critical component of lasers, especially
fiber optic laser systems. No one these days makes a long-distance
call or uses their cell phone and doesn’t have part of that signal
path include some work that originated here at Illinois.
Q: What role do students play in your research?
A: We have undergraduates who work in my lab all the
time, one or two of them every semester, doing a senior project or
an independent study. We don’t send them off and make them
do little baby projects. They are assigned a graduate mentor
and they do whatever we’re doing at the time. They can
contribute. They’re bright young engineers. In another
year or two they’re going to be graduate students. They’ve
got some good background and ability, all they lack is experience. We
show them more at the beginning, but by the end of the semester they’re
carrying out work and learning at the same time.
You can’t do anything at a university like this without the graduate students. It’s very rare that a faculty member can work on his own. There have been students involved in everything we’ve done. The typical graduate student…in their first year or two, are very bright but inexperienced and all of the intellectual ideas come from me. By the end, they’re about ready to go out into industry be independent researchers. We’re just coworkers and colleagues. They produce as many ideas as I do or more. There’s a transition as they go through the program.
Q: What do you enjoy most about teaching?
A: If you are a research professor, basically,
you spend half your time as a teacher and half your time as a researcher. And
of course researching is really teaching because you’re working
with students.
The material itself, once you’ve taught it once or twice you know it inside and out so you don’t really gain much from teaching the material. What really is great and enjoyable is that every semester there is a new group of kids that come in that don’t really know what you know and want to.
You get a group of 30 kids and you make life-long friends out of them, some of them turn out to be graduate students. That’s the part that’s fun and rewarding. So, I try to have a lot of dialogue in my classes and ask questions and entertain questions so they’re participating, it’s not just lectures.
Q: What are you focused on today?
A: One [shorter-term project] is based on narrow linewidth
lasers. The spectral purity of a laser depends on a lot of things. Consider,
for example, an FM radio. The reason that you can have adjacent
stations is that the energy they are transmitting falls in a narrow
enough band that they don’t overlap. The same thing applies
to the laser. The laser is electromagnetic radiation, just like
a radio wave. So making semiconductor lasers that are very narrow
allows you to use them for certain applications that are important,
one of which is spectroscopy. You can use them to sample whether
or not certain atoms are present or how many [are present]. You
can use that for applications in homeland security, to study the molecular
structure or molecular gas content in the upper atmosphere for environmental
or weather purposes, you can use it in laboratories, in manufacturing
environments, and so on. So there is a lot of interest in having
a tiny little laser like the ones that are in a CD player or laser
pointer, but that can be used to do this chemical analysis kind of
thing. So we’ve been working on that. We have some
unique structures that give us these very narrow line widths and allow
us to do some things that you can’t do with otherwise conventional
lasers.
[A longer-term project] is what’s called quantum dots…laser devices that have embedded in them small enough chunks of material that quantum mechanics plays a very strong role in how they behave and there is a lot of basic physics and materials science that goes into this. It’s difficult to make them which is part of the reason it’s a long term project. There is a driving need for electronic devices and optical devices that do things that are much smaller and so we’re in the middle of that. And what that leads to ultimately is very low power devices that are physically small, electrically fast, optically fast, and lead to greater density of devices and more integration and more computational power and more communications power and things like that. The whole world is always interested in faster, smaller, cheaper.
Please direct any media inquiries to Brad Petersen at (217) 244-6376 or bradp@illinois.edu.
Professor Coleman can be reached at (217)333-2555 or jcoleman@illinois.edu.