Published: Nov. 29, 2021

Ryan Cole
Ryan Cole, Mechanical Engineering PhD candidate.

The Department of Mechanical Engineering has awarded PhD candidate Ryan Cole this year’s Outstanding Dissertation Award.

Cole, who will be graduating with his PhD in mechanical engineering in December 2021, has focused his research on laser-based sensors for high-pressure and high-temperature systems.

In just over five years, Cole has finished five first-author papers, three second-author papers, four third+ author papers, one patent application and 16 conference papers and presentations. The papers have earned more than 100 citations, an editor’s pick for one of his first author papers and a best student paper award for one of his conference papers.

His advisor, Professor Greg Rieker, said that Cole has been in constant service to the department. Cole served as the lead instructor of a thermodynamics course and has made a commitment to improving diversity, equity and inclusion in the department by joining the Anti-racist Pedagogy Learning Community under the CU Center for Teaching and Learning.

“In my eight years as a professor, and my years as a postdoc and graduate student before that, I have not seen an across-the-board stronger performing student,” Rieker said. “I have certainly not seen a stronger student with the down-to-earth, caring attitude that Ryan has. He will make a spectacular professor and a spectacular representative of the College of Engineering and Applied Science.”

Cole shared more about his engineering education, dissertation and goals for the future.

What led you to study engineering?

I grew up in Denver but completed my undergraduate degree in physics and mathematics at Colby College in Waterville, Maine. During my undergraduate work, I worked on a research project at NASA Goddard Space Flight Center focused on X-ray detectors for a planned satellite observatory. I also completed a senior thesis in ultra-cold plasma physics. After Colby, I spent a year in Hilo, Hawaii, where I worked as an astrophysical research intern at the Gemini Observatory. I enjoyed all these past experiences, but ultimately, I found myself growing increasingly interested in more application-focused research. This is what drew me to the University of Colorado and the Department of Mechanical Engineering. I now work with Professor Greg Rieker in the Precision Laser Diagnostics Lab, where I use dual frequency comb absorption spectroscopy to improve and enable laser-based sensors for high-pressure, high-temperature environments. 

What is the title of your dissertation? Can you give a summary of what you found?

high-temperature, high-pressure system
The instrument Cole built to study the benefits of dual-comb spectroscopy for sensing in high-pressure, high-temperature systems.

My thesis is titled "Methods and Applications for Dual Frequency Comb Absorption Spectroscopy in High-Pressure, High-Temperature Environments." High pressures and temperatures are ubiquitous in science and engineering. They can be found in the cylinder of your car engine, in the combustor of a rocket engine or in the atmospheres of exotic planets and exoplanets. As scientists and engineers, our ability to understand and improve these systems depends on our ability to make measurements in those environments. 

The overarching goal of my PhD research is to improve and enable laser-based sensors for high-pressure, high-temperature systems. I specifically use a technique called laser absorption spectroscopy, which refers to the absorption of laser light at frequencies resonant with molecular quantum state transitions. The shape and size of measured absorption transitions gives us a measure of the thermodynamics conditions of the sample gas – things like temperature, pressure, etc. In the Precision Laser Diagnostics Lab, we use a specific technique called dual frequency comb absorption spectroscopy, which enables broadband, high-resolution absorption spectroscopy across a multitude of stable and well-known optical frequencies. My specific dissertation research is focused on developing new techniques to leverage the benefits of dual-comb spectroscopy for sensing in high-pressure, high-temperature systems. I also use dual-comb spectroscopy to improve models for molecular absorption in high-pressure and high-temperature gases, which are needed in order to interpret the spectra recorded by our instruments. 

What have you enjoyed most about your research?

I enjoy the balance of physics and engineering. My research often uses elements of fundamental optics and spectroscopy that are usually associated with physics research. In my case, I get to study these topics while also being focused on the real-world applications of our research. 

What lessons have you learned from your advisor Professor Greg Rieker?

Greg has taught me so much over the last five years, it is almost difficult to come up with specific examples. There have been quite a few times when Greg has encouraged me to take on challenges that seemed insurmountable. Over time, I learned that Greg is almost always right about these things and in retrospect, my work to address these challenges has improved my research results and has helped me grow as a researcher. 

Ryan Cole
Cole enjoying the outdoors.

What accomplishment from your time at CU Boulder are you most proud of?

I had the opportunity to teach a thermodynamics course in spring 2021. Teaching this course was one of my biggest challenges during grad school, but ultimately it is one of the things I am most proud of. 

What is the impact you hope to have on the world one day?

I would like to look back at my career and know that I used my skills to make the world a better place. For me, this means I would like to work on projects to address and better understand climate change. I am particularly interested in developing new techniques to quantify emissions and their effect on the atmosphere. I would also like to continue teaching at the college level. In a perfect world, I will find an opportunity that lets me combine these two goals.