I undertook my doctoral research under the guidance of Dr. Gregory Rieker in the Department of Mechanical Engineering at the University of Colorado Boulder. I was fortunate to join Dr. Rieker’s group as one of his two first graduate students and am his first graduated Ph.D. student. This timing allowed my to see all of the detail that needs to be considered when building a lab from scratch, which areas are important for fund allocation, and how to plan for long-term usability of lab space and equipment. My time in Dr. Rieker’s group was transformational and has made me excited at the prospect of one day running a research group of my own in private industry, a national laboratory, or potentially as a professor.
If you are interested in joining or finding out more about Dr. Rieker’s group, please visit: https://www.colorado.edu/riekerlab/
Research Topics and Experience:
My research with Dr. Rieker focused entirely on the study of absorption spectroscopy and its applications to real world, combustion systems. Absorption spectroscopy provides researchers with a noninclusive and reliable method for exploring high temperature systems, including combustion. However, accurate measurements require accurate knowledge of how molecules at high temperatures behave when probed with laser light. My research focused on understanding the high temperature behavior of water while building and deploying a highly accurate and precise mobile, dual frequency comb spectrometer capable of being deployed in industrial environments.
The long-term, overarching goal of my work was to advance the absorption spectroscopy community’s ability to make accurate and precise in such harsh environments. Measurements like this can allow real time control of combustion variables to optimize power production, better understand combustion chemical reactions, and/or minimize polluting species.
To these ends, my dissertation covered two distinct areas of absorption spectroscopy:
First, I spent a large amount of time, along with other group members, building and deploying the first mobile dual frequency comb spectrometer. A frequency comb laser is a mode locked laser that generates hundreds of thousand of precisely spaced and controlled optical frequencies spanning hundreds of nanometers in spectral coverage. Prior to our work, a frequency comb was a laser source that was confined to live in highly controlled and stable optics research laboratories. However, leveraging recent developments in frequency comb design by Nate Newbury’s group at NIST Boulder (https://www.nist.gov/pml/applied-physics-division/fiber-sources-and-applications), our group under Dr. Rieker was able to build a robust dual comb spectrometer capable of field measurements outside of an optics laboratory. We then set out with this instrument to measure the CO2 and water amounts and temperature through the exhaust stream of a running natural gas turbine in the CU Boulder power plant.
Second, I spent a signification portion of time studying high temperature spectroscopic parameters of water and how various lineshape functions predict and model measured spectra. These lineshapes are numerically fit to collected spectra to allow experimenters to extract useful parameters from the gas like temperature and mole fraction of the absorbing species.
Mentoring and Leadership Experience:
Owing to the rapid expansion of the lab group during my time, I was able to mentor numerous younger students: 2 Ph.D students, 4 undergraduates, and 2 high school teams’ senior projects. I was directly involved with scoping projects according to specified time frames, skill level, and interests while working to make the students feel welcome within the group. I was also able to be involved with hiring decisions regarding post doctoral researchers and incoming students. I was also fortunate to initiate and lead a team of younger students to design and construct a high temperature, high pressure spectroscopic cell that will result in a new experimental focus in the Rieker group. This mentoring aspect of my Ph.D. was perhaps the most satisfying experience during my time in graduate school. To be even a minor part in students not only beginning to understand the research in the group but to become proficient and independently creative is deeply satisfying and something I would like to pursue throughout my career.
Since I was one of the two first graduate students, I was intimately involved with purchasing of all major and minor instrumentation and equipment. I was responsible for setting up equipment cost bids, cost/benefit analysis, construction of experiments, interaction with external company representatives, and adhering to budgetary and time constraints. Prior to Dr. Rieker’s professorship, our lab was completely empty and within a year, we were collecting publishable data. Helping to build the lab from scratch has given me valuable insight into all that goes into a functional and productive laboratory.
Collaborative Experience:
I was extremely fortunate to have had the opportunities to work with a variety of exceptional scientists and engineers from various organizations.
-I began my Ph.D. work working closely with Nathan Newbury and Ian Coddington’s dual frequency comb work at NIST in Boulder. I started from zero knowledge of frequency combs and they patiently taught me how to use their dual-comb spectrometer and much of the underlying physical and electro-mechanical principals that were in play.
-I worked closely with Madison Kelley and Professor Jason Porter at Colorado School of Mines. As outlined previously, we worked closely with them to utilize our spectrometer in their gasifier. Madison and I spent more 24 hour data collection sessions in his lab than we would both like to count but the data turned out well and we are in the process of writing a paper outlining the data.
-Our group also formed a close relationship with Brian Drouin and Matt Cich at the Jet Propulsion Laboratory in Pasadena, California. We approached them for help analyzing our data to extract spectroscopic parameters since we did not have the correct computational programs in place. After a few emails and some discussion between groups, Professor Rieker, Jinyu Yang, and myself flew out to Pasadena for about a week to sit with Brian and Matt and learn their amazing software. In 3 days of data processing while using their software, we made more progress than Jinyu and I had made in the previous year and a half. This data processing is a large part of the reason Jinyu and I were able to publish out database parameter papers in the Journal of Quantitative Spectroscopy and Radiative Transfer.
Peer Reviewed Publications:
P.J. Schroeder, R.J. Wright, S. Coburn, B. Sodergren, K.C. Cossel, S. Droste, G.W. Truong, E. Baumann, F.R. Giorgetta, I. Coddington, N.R. Newbury, G.B. Rieker, “Dual Frequency Comb Laser Absorption Spectroscopy in a 16 MW Gas Turbine Exhaust”, Proceedings of Combustion Institute (Peer reviewed journal publication), 2016
P.J. Schroeder, D.J. Pfotenhauer, J. Yang, F.R. Giorgetta, W.C. Swann, I. Coddington, N.R. Newbury, G.B. Rieker, “High temperature comparison of the HITRAN2012 and HITEMP2010 water vapor absorption databases to frequency comb measurements”, Journal of Quantitative Spectroscopy and Radiative Transfer, HITRAN Special Edition, 2017
Paul J. Schroeder, Matthew J. Cich, Jinyu Yang, William C. Swann, Ian Coddington, Nathan R. Newbury, Brian J. Drouin, and Gregory B. Rieker Broadband, High-resolution investigation of advanced absorption line shapes at high temperature, Physical Review A 96, 022514
P.J. Schroeder, M. Cich, J. Yang, F.R. Giorgetta, W.C. Swann, I. Coddington, N.R. Newbury, B.J. Drouin, G.B. Rieker, “Speed-dependent Voigt Lineshape Parameter Database from Dual Frequency Comb Measurements at up to 1300K: Part I. Pure H2O, 6800-7200cm-1” Journal of Quantitative Spectroscopy and Radiative Transfer, 2018
P.J. Schroeder, M Kelley, J. Porter, G.B. Rieker, Temperature and water mole fraction measurements in an argon rich entrained coal gasifier using dual frequency comb spectroscopy. In preparation.
Yang, P.J. Schroeder, , M. Cich, W.C. Swann, I. Coddington, N.R. Newbury, B.J. Drouin, G.B. Rieker, “Speed-dependent Voigt Lineshape Parameter Database from Dual Frequency Comb Measurements at up to 1300K: Part II. Argon broadened H2O,6800-7200cm-1”, Journal of Quantitative Spectroscopy and Radiative Transfer, September 2018
Presented Conference Talks (3 of 7):
Schroeder, M. Cich, J. Yang, B. Drouin, G. Rieker, “Multispectral fitting validation of the speed dependent Voigt profile at up to 1300K in water vapor with a dual frequency comb spectrometer,” Paper WJ09, International Symposium on Molecular Spectroscopy, Urbana-Champaign, Illinois, June 19-23, 2017
P.J. Schroeder, D.J. Pfotenhauer, J. Yang, F.R. Giorgetta, W.C. Swann, I. Coddington, N.R. Newbury, G.B. Rieker, “High temperature comparison of the HITRAN2012 and HITEMP2010 water vapor absorption databases to frequency comb measurements”, Paper SW1L.6. Presented talk at Conference in Electro Optics (CLEO) on May 17, 2017.
P.J. Schroeder, R.J. Wright, S. Coburn, B.M. Sodergren, K.C. Cossel, S. Droste, G.W. Truong, E. Baumann, I. Coddington, N.R. Newbury, G.B. Rieker, “Dual frequency comb laser absorption in a 16 MW gas turbine exhaust,” The 36th International Symposium on Combustion, Seoul, South Korea, Aug.
Conference Publications:
Schroeder, J. Yang, F. Giorgetta, W. Swann, I. Coddington, N. Newbury, and G. Rieker, “Dual frequency comb spectroscopy of high temperature water vapor: absorption model development for combustion sensors,” Paper FW2E–5, Fourier Transform Spectroscopy, Leipzig, Germany, November 2016.
Schroeder, D. Pfotenhauer, J. Yang, F. Giorgetta, W. Swann, I. Coddington, N. Newbury, G. Rieker, “Comparison of dual frequency comb absorption spectra of air-broadened water vapor up to 1300K with HITRAN Online and HITEMP2010 models,” Paper SW1L.6, Conference on Lasers and Electro-Optics (CLEO) , San Jose, CA, May, 2017
Schroeder, M. Cich, J. Yang, B. Drouin, G. Rieker, “Multispectral fitting validation of the speed dependent Voigt profile at up to 1300K in water vapor with a dual frequency comb spectrometer,” Paper WJ09, International Symposium on Molecular Spectroscopy, Urbana-Champaign, Illinois, June 19-23, 2017
T.R.S. Hayden, P. Schroeder, and G. Rieker, “Large Amplitude Wavelength Modulation Spectroscopy for Sensitive Measurements of Broad Absorbers,” Paper SM1O.5, CLEO 2015, San Jose, CA, May 2015
(Invited) G. Rieker, P. Schroeder, S. Coburn, C. Alden, R. Wright, K. Cossel, G. Truong, E. Baumann, F. Giorgetta, W. Swann, I. Coddington, and N. Newbury “Combustion diagnostics and chemical sensing with frequency comb lasers,” Paper LW2G–1, Laser Applications to Chemical, Security and Environmental Analysis (LACSEA), Heidelberg, Germany, July 2016.
(Invited) G. Rieker, F. Giorgetta, W. Swann, P. Schroeder, J. Kofler, L. Sinclair, E. Baumann, G. Petron, C. Sweeney, P. Tans, I. Coddington, and N. Newbury, “Precision atmospheric trace gas monitoring with frequency comb lasers,” Frontiers in Optics/Laser Science, San Jose, CA, October 2015.
(Invited) I. Coddington, G. Truong, E. Waxman, K. Cossel, P. Schroeder, S. Coburn, R. Wright, F. Giorgetta, W. Swann, G. Rieker, and N. Newbury, “Dual-Comb spectroscopy for GHG quantification,” Paper EM3A–3, Optics and Photonics for Energy and the Environment (E2), Leipzig, Germany, November 2016.
Presented Posters:
P.J. Schroeder, G.B. Rieker, “Dual frequency comb spectroscopy of high temperature H2O absorption: Testing and improving spectral databases for use in coal gasification,” Gordon Research Conference-Laser Diagnostics in Combustion, August 2015, Waterville Valley, NH.
Schroeder, G. Rieker, “Spectroscopy of Water Vapor in a Coal Gasifier Using Dual Frequency Comb Spectroscopy,” Colorado Photonics Industry Association, October 2014. Won award for best poster (1 of 3).
Paul Schroeder's Professional Profile 