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My Summer with MIRTHE

Photonics Spectra
Mar 2010
Alexandra M. Ritter, Student

I have never been particularly interested in the field of engineering. Physics? No thank you, I’ll stick to English and history. So when my father came to me with the opportunity to work in a lab in Princeton for the summer, I was feeling more than a little apprehensive. But curiosity (and a desire to work somewhere that paid above minimum wage) got the better of me, and I signed up to be Princeton University’s newest high school summer intern at MIRTHE, the National Science Foundation-sponsored Engineering Research Center on Mid-InfraRed Technologies for Health and the Environment.

MIRTHE, based at the university, leads the development of a new quantum cascade laser-based platform of trace gas sensor systems with improved high-performance and cost-effective sensing capabilities for environmental sensing, homeland security and medical diagnostics.

Students present their work at the MIRTHE Summer Workshop poster session at the City College of New York. Photos by Frank Wojciechowski, courtesy of MIRTHE.

It also provides educational programs such as summer research opportunities to high school students in an interdisciplinary, collaborative research environment, and this was the program in which I worked. Students were immersed in local research teams, conducting original and hands-on laboratory work. Our activities included conference calls with students at MIRTHE partner universities; short courses offering insights into a wide range of research fields; informal social gatherings providing opportunities to network and to learn; and field trips to industrial and government laboratories in the area. We even got to present our research projects and results at the off-site MIRTHE Summer Workshop, an annual weeklong event that concludes the summer program each year.

Our lab had the bulk of the people in the program. There was a good blend of high school students, soon-to-be college freshmen, undergraduates and graduate students. At first, the prospect of working with a bunch of older kids who were already majoring in engineering, a field about which I didn’t have the first clue, was daunting. But throughout my summer internship at Princeton, I never met an undergrad or grad student who would turn me down if I asked for help – especially Princeton University graduate students Ekua N. Bentil and Wen-Di Li, whose project I joined.

Professor Claire Gmachl and high school students, from left, Colin Montemarano and Joseph Schiavone, at the MIRTHE summer research internship.

For my project, titled “Optical Properties of Semiconductor-Based Sub-Wavelength Gratings for the Mid-Infrared Wavelength Range,” I worked to improve quantum cascade lasers; for these lasers to be useful, the usually multimode emitters must be made single mode and tunable, one approach being by external feedback from a dispersive optical element, such as a grating. I evaluated the efficacy of subwavelength gratings fabricated by imprint lithography, not unlike those used at shorter wavelengths. In particular, I evaluated the optical properties – reflection and transmission – of semiconductor-based subwavelength gratings. My preliminary results demonstrate the utility of such gratings in the mid-infrared.

One of the best things about MIRTHE was how easy it was to learn so much new information on my project with so many people willing to teach. Even though our adviser seemed like the busiest person at Princeton, she still found time to come to see all of us high school kids in the lab and to talk to us about our projects, our lab notebooks, our abstracts, our posters, and any and all questions with which we could possibly bombard her. If she was busy, we also could talk to our graduate students. They handled every e-mail we sent with ease at any time of day, which is how we all came to the conclusion that they probably don’t ever sleep.

The lab was the most interesting part of the experience. When I first walked in, it looked like a huge room with clutter on every available surface: equipment, samples, lab notebooks and whatever else people happened to leave strewn about. Eventually, the mess became ordered in my eyes, and by the end of the summer, my fellow interns and I could have told you where anything was in the lab. Encountering the equipment itself also was a fascinating new experience. The most advanced equipment I had used before that summer was a mass spectrometer, and now they wanted me to work with a Fourier transform infrared instrument?

It was hard at first to figure out all the tricks and sensitivities of the machine, but as with everything else, it took only some guided practice and a few mishaps to get a feel for what I was doing. Of course, the machinery and the samples we used never let us get too complacent: The old light-current-voltage (LIV) measurement setup would break, and everyone who used it needed time slots on the new LIV; a sample would snap in half in the process of transferring it to the sample holder; lenses were mysteriously scratched, and no one would own up to having done it. Every day there was a new problem to solve, whether planned or unplanned, and I managed to surpass even my own expectations by working out each one thrown my way. After a couple of weeks, we were running around looking for lost lenses, fighting over equipment time slots and forgetting where in the lab we had put a particular sample for safekeeping, just like everyone else in the lab.

Student Alexandra Ritter and her adviser, professor Claire Gmachl, work in the Princeton research lab.

I think the highlight of everyone’s MIRTHE experience was our trip to New York for the weeklong MIRTHE conference, where we converged with the five other universities hosting the MIRTHE program – the City College of New York, the University of Maryland Baltimore County, and Johns Hopkins, Rice and Texas A&M universities – and presented our research. We traveled with minimal chaperoning (no parents) and stayed in the dorms of St. John’s University in New York – which, for me and my high school comrades, was really our first time away from home on our own.

From the second our adviser told us that we had better make a ton of noise when they called for the kids from Princeton to make themselves known, we knew that it wasn’t going to be a completely boring scientific conference, and it sure wasn’t. We had to sit through numerous graduate talks that were each 15 minutes long, but some of the grad students managed to make their talks interesting and captured our attention even beyond the introduction. Some were humorous, some had interesting research projects that made you sit up and listen, and some were good talkers who could make just about anything sound interesting. Most of them had one or more of these qualities, and it was very impressive that they could captivate all the high school students in the back row, who didn’t have a clue what their research was all about.

We each also had to make a three-minute presentation on our own research. There were plenty of slipups, but for the most part, all of our practice and hard work allowed us to not embarrass ourselves too much. There was also the especially nerve-racking poster session. At first, I was especially anxious about being questioned by the other attendees because I wasn’t sure I would be able to answer the questions of professors and other science-minded people, but I found that, as the inquiries began, after such extensive and thorough researching of my topic, I could answer most questions with barely any thought.

My summer with MIRTHE ended up being a completely different experience from what I had expected. I gained a new interest in science that I had never found in school, I learned how real research is conducted, and I also made friends with whom I remain in contact. It was challenging at first, but it truly paid off in the end. For more information about MIRTHE, including the internship program, visit

Meet the author

Alexandra M. Ritter attends Cinnaminson (N.J.) High School; she was a summer internat MIRTHE, Princeton University, in 2009. In the fall of 2010, she will attend New York University.

A framework or latticework having an even arrangement of rods, or any other long narrow objects with interstices between them, used to disperse light or other radiation by interference between wave trains from the interstices. The ability of a grating to separate wavelengths (chromatic resolving power) is expressed as being equal to the number of lines in the grating.
quantum cascade laser
A Quantum Cascade Laser (QCL) is a type of semiconductor laser that emits light in the mid- to far-infrared portion of the electromagnetic spectrum. Quantum cascade lasers offer many benefits: They are tunable across the mid-infrared spectrum from 5.5 to 11.0 µm (900 cm-1 to 1800 cm-1); provide a rapid response time; and provide spectral brightness that is significantly brighter than even a synchrotron source. Quantum cascade lasers comprise alternating layers of semiconductor...
Return of radiation by a surface, without change in wavelength. The reflection may be specular, from a smooth surface; diffuse, from a rough surface or from within the specimen; or mixed, a combination of the two.  
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