Greg Rieker

Prof. Greg Rieker

Associate Professor
Department of Mechanical Engineering
ECME 226


  • 2009: PhD, Stanford University
  • 2004: MS, Stanford University
  • 2002: BS, University of Missouri - Rolla

Prof. Rieker has been at CU since fall 2013. His teaching interests are in design and thermosciences. Prior to the University of Colorado, Greg spent a year as an NRC research associate at the National Institute of Standards and Technology (NIST), exploring the use of frequency comb lasers for sensing in practical systems. Prior to NIST, Greg developed and studied a plasma-based particle accelerator for medical applications, first as a postdoc at Stanford and then through a company that he co-founded. During his PhD, he developed laser-based sensors for a variety of combustion applications, including internal combustion engines, scramjet engines, and oil refinery process flames.

Prof. Rieker has a particular interest in mentoring and developing students into multi-faceted engineers – that is, engineers who are not only excellent researchers, but leaders and entrepreneurs with an eye toward creating opportunity for themselves and others.

Senior Scientists

Sean Coburn

Sean Coburn

Sean Coburn earned his BS in Chemistry and BA in Biology at Newman University in 2007. He then went on to earn a PhD in Chemistry from the University of Colorado Boulder in 2014 under the advisement of Prof. Rainer Volkamer. During his graduate work, Sean’s research revolved around field measurements of atmospheric trace gases using absorption spectroscopy. Additionally, his projects contained a focus on instrument development. This included the building and deployment of a ground-based passive remote sensor for the detection of halogen oxides and oxygenated volatile organic compounds in the coastal marine boundary layer; and an active in-situ sensor for the measurements of volatile organic compounds over the remote tropical Pacific Ocean. In his spare time, Sean likes spending time with his family in the mountains or enjoying other outdoor activities.

Garrett Mathews

Garrett Mathews

Garrett Mathews earned his BS in Mechanical Engineering and minor in Physics from Gonzaga University in 2016.  He went to work with Professor Christopher Goldstein at Purdue University where he was awarded an NSF graduate research fellowship in 2017 and earned his PhD in 2021.  His graduate research primarily focused on developing laser-absorption spectroscopy diagnostics employing tunable diode lasers and quantum cascade lasers to measure temperature, pressure and species in rapidly evolving combustion systems. He utilized these diagnostics to perform measurements in explosive fireballs, rotating detonation rocket engines, and post-detonation fireballs at measurement rates up to 1MHz.  Garrett joing the Precision Laser Diagonstics Lab in the fall of 2021.  His work focused on developing high-precision, mid-infrared frequency comb diagnostics.  In his free time, Garrett enjoys snowboarding, mountain biking, and a rotating set of various hobbies.

Post Docs


Graeme Gillespie

Graeme Gillespie received his BS in Engineering Physics from Queen’s University (Canada) in 2017. He then went on to earn his PhD in Aerospace Engineering from the University of Maryland in 2023. At the University of Maryland, he conducted research in the field of experimental hypersonics under the supervision of Professor Stuart Laurence. Graeme’s work focused on the ability of molecular nonequilibrium processes to control turbulence-generated acoustic noise under high-speed conditions. This project involved the development of interferometry systems for high-frequency measurements of density fluctuations in hypersonic ground-test facilities. Graeme joined the Precision Laser Diagnostics Lab in the summer of 2023, where he works on the development and application of mid-infrared frequency comb systems. 


Justin Earley

Justin Earley received his B.S. in Chemistry from the University of Wisconsin – Madison. He pursued further studies at the University of Colorado Boulder, earning his Ph.D. in Physical Chemistry in collaboration with the National Renewable Energy Lab, focusing on developing solution-phase microwave spectroscopy to measure spatial charge dynamics of photoredox catalysts, under the mentorship of Professor Garry Rumbles and Professor Obadiah Reid. Currently, as a postdoc in the Precision Laser Diagnostics Lab, his work is concentrated on introducing electro-optically sampled dual-comb spectroscopy to the investigation of combustion byproducts. Deeply intrigued by the potential of dual-comb spectroscopy, especially its prospective role in quantum chemistry, Justin aspires to amalgamate this innovative spectroscopy method with the study of electronic states in future research endeavors. Outside the lab, his love for the outdoors is evident through his favorite pastime of camping, and he crafts a balanced life by indulging in hobbies such as gardening, crocheting, and woodworking.

PhD Students

Charlie Callahan

Charlie Callahan earned his B.S. in Mechanical engineering and minor in physics from CU Boulder. During his time there he worked at a diffraction grating manufacturing company and designed a laser based flame sensor for his B.S. Senior Design Project. This led him to be a co-inventor on a patent. Charlie learned that he liked Boulder and engineering so he decided to stay at CU to pursue his PhD in Mechanical Engineering. During his (minimal) free time, Charlie like to ride mountain bikes, ski and snowboard.

Carl Mathurin

Carl Mathurin earned his B.S. in Aerospace Engineering and Physics from the University of Texas at Austin (UT). While at UT he was a research assistant helping to research magnetic plasma confinement. After graduating, he went on to work as a research associate on the GRACE-FO mission at the Center for Space Research (CSR). Now at CU Boulder, he is pursuing a PhD in Mechanical Engineering and working in the Precision Laser Diagnostics Lab where he will be doing dual-frequency comb absorption spectroscopy on combustions systems. When not doing research, Carl enjoys playing a variety of sports including basketball, tennis, boxing, and Muay Thai.

Elijah Miller

Eli Miller earned his B.S. in Mechanical Engineering at the University of Washington in Seattle. After graduating, he worked as a mechanical engineer designing crash test equipment for the automotive safety industry. He is joining the Rieker lab in 2021 to persue his PhD and use dual frequency comb spectroscopy to measure and characterize permafrost methane emissions in Alaska. Outside of work, he loves skiing, climbing, biking, and cooking. 

Alyssa Lalko

Alyssa Lalko received her B.S.E. in Mechanical Engineering and a Specialization in Energy from Oakland University in Rochester, Michigan. While there, she spent a summer at NREL, worked briefly in the auto industry, and spent two years researching a gasoline-electric multirotor drone. Alyssa joined the Precision Laser Diagnostics Lab in Fall 2021 and received NSF support to pursue a PhD. Her research will be to develop a portable laser that monitors atmospheric toxics, which will contribute to understanding air quality at local and global scales. In her free time, Alyssa enjoys running, reading, playing piano, and gardening.

Augustine Frymire

Augustine earned his B.S. in Mechanical Engineering at the University of Missouri in Columbia, where he lived with his family after leaving Germany in 2001. 

He started his PhD at CU Boulder with the Precision Laser Diagnostics Lab in Fall 2021, and his research is focused on the development of compact and high-speed electro-optic dual frequency comb sensors for hypersonic velocimetry and other applications. 

Erick Gatica Candia

Erick Gatica from Chile got his major in Chemical Engineering and a Master's degree in Chemical Engineering at the University of Santiago of Chile. Erick was awarded a Fulbright scholarship to drive his Ph.D. studies at CU Boulder, and he expects he gains experience at NASA or in the aerospace sector while he conducts this program in the US. During his staying at the university in Chile, he started to teach theoretical and laboratory courses on topics regarding transport phenomena, mass transfer, process control, thermodynamics, and engineering mathematics for different departments. Moreover, Erick has participated in research on solar energy, energy storage systems, desalination, and fluid-particle contact technologies such as spouted beds. In addition, he was working for an energy and sustainability company in his country. He has always enjoyed learning, and he is a big fan of the space race and NASA; he is very excited to delve deeper into the topics of remote sensing and hydrogen technologies and to work with the research group in this Laboratory. During his free time, he enjoys watching documentaries, practicing sports like CrossFit or hiking, connecting with nature, and spending quality time with his loved ones.

Carly Rowe

Carly Rowe earned her B.S. in Mechanical Engineering from the University of Wisconsin—Milwaukee. During her undergraduate degree, Carly was awarded the NSF P.E.C.S. scholarship which she used to drive her studies and her professional development. Additionally, she was the President of a student organization called Students for the Exploration and Development of Space (SEDS) where she led two NASA-funded multidisciplinary projects working with the design, manufacture, and launch of solid rockets; and the study of cosmic particles in Earth's atmosphere. She also spent time working as a Calculus I and II tutor, a software engineer for a wastewater treatment company, and a software engineer for a start-up aiming to help domestic violence victims. Carly joined the Precision Laser Diagnostics Lab in Fall of 2023. During her free time, Carly likes to take her dog for walks, paint, read, and get outside. 


Nico Haris

Nico Harris earned his B.S. in physics at the College of Charleston in Charleston, South Carolina. While there, he spent 3 years performing material science research using femtosecond lasers to study the response of phonons in 2D materials. He is joining the Rieker group in the fall of 2023 to pursue his Phd and is currently planning on monitoring methane slip from flares. In his free time Nico enjoys baking, drawing, playing piano, and playing video games.


Mechanical Engineering Interns

Colton Huff

Colton Huff

Colton Huff is pursuing his Master's in Mechanical Engineering with an emphasis in design through an Accelerated Masters Program to complete in May 2025 after graduating with a B.S. in Mechanical Engineering from CU Boulder in 2024. He came to CU Boulder after being awarded the Boettcher Scholarship and over his undergrad has enjoyed exploring the relationship between a user and a product's design and got the opportunity to join the Precision Laser Diagnostics Laboratory in May of 2023 as an intern with a focus on redesigning different laboratory systems to be more mobile and durable to transition to in field measurements. Throughout his work in the Laboratory, he has consulted on an array of different projects and designs and looks forward to transitioning into a master's role in the lab in the 2024-2025 year. In his free time, he loves hiking and attending a wide variety of sporting events while also being a semi-professional soccer referee officiating games across the United States.


Gemma Gallaher

Gemma Gallaher is currently pursuing a B.S. in Mechanical Engineering with a minor in Computer Science at CU Boulder. She is interested in component testing and failure analysis, and all things code-related. After getting the opportunity to join the lab as an intern in May of 2023, Gemma enjoyed the research she was working on and remained to continue examining the transmission of light through materials at high temperatures. Alongside this, she is also working on redesigning an experimental system to expand measurements from the near- to mid-infrared region. In her free time, Gemma enjoys climbing, hiking, reading, and snowboarding.


Nazanin H

Nazanin Hoghooghi - NIST Research Scientist

Nazanin Hoghooghi received her PhD in Optics from the College of Optics and Photonics (CREOL) at the University of Central Florida. During her PhD in Prof. Peter Delfyett's group, she developed a high-speed linear intensity modulator based on an injection-locked semiconductor laser for analog optical networks. After her PhD, she joined Prof. Ming Wu's group at the University of California-Berkeley, where she developed a low noise millimeter wave source using photonic techniques. She received a Marie Curie fellowship from the European Commission in 2013 and joined the Quantum Sensors Technologies and Applications (QTEA) network. She conducted her research at TOPTICA Photonics in Munich, Germany. She developed two Hz-linewidth cavity stabilized laser systems with relative short term stability of 10^-15 at 1 sec, and an optical link with phase noise cancellation to deliver the light from the Hz-level reference lasers to a home-built difference frequency generation (DFG) frequency comb. This enabled the first in depth characterization of a DFG frequency comb. Nazanin moved to Boulder with her husband in summer 2015. She joined the Precision Laser Diagnostics group in January, where she is working on highly sensitive frequency comb systems for the detection of hazardous trace gases.

Caroline A

Caroline Alden - CIRES Research Scientist

Caroline Alden is a research scientist at CIRES. She is working with Greg Rieker at CU, and Colm Sweeney at the NOAA/ESRL Carbon Cycle Group to detect leaks of methane and other hydrocarbons during natural gas production and distribution, through inverse modeling of trace gases observed by open path frequency comb lasers. Prior to CIRES, Caroline was a postdoctoral fellow at Stanford University, working with Prof. Noah Diffenbaugh on connecting climate extremes in the Amazon Basin to variations in net biosphere exchange of CO2 with the atmosphere. Caroline earned a Ph.D. in Geology from the University of Colorado, Boulder in 2013, with Prof. Jim White and Dr. John B. Miller (NOAA/ERSL), for her work developing an inversion framework for 13C of atmospheric CO2, and exploring its potential as a tracer for regional drought stress in North America. She has also published work on global CO2 sink strength and on atmospheric 13CO2 as a potential indicator of global terrestrial carbon exchange, water stress, and partitioning C3/C4 plant productivity. Caroline’s love of exploring the outdoors led her to pursue arctic field geology at Colorado College, which led to an interest in climate change research and, eventually, the pursuit of techniques for interpreting the signals and signs left by nature and humans in atmospheric greenhouse gases.

Scott Egbert

Scott Egbert, PhD

Scott Egbert earned his PhD in Mechanical Engineering in Spring 2024.  He has received a post doc appointment to the Precision Laser Diagnostics Lab to work on the PICARD - SAURON  project. 

David Y

David Yun, PhD

 After completing a PhD in Mechanical Engineering in the Precision Laser Diagnostics Lab, where he set the sights of dual-frequency combs on hot methane, David joined the Boeing corporation. In his spare time, he loves playing on his humble piano keyboard and getting lost in grocery stores.

Ryan Cole

Ryan Cole, PhD

Ryan Cole Ryan began his Ph.D. work in the Precision Laser Diagnostics Lab in the Fall of 2016 and received his PhD in December 2021. His research focused on dual-frequency comb absorption spectroscopy of gasses at high temperatures and pressures. When not in the lab, he enjoys fly fishing, road biking, and hiking in the mountains around Boulder.

Alex Rybchuk

Alex Rybchuk, PhD

Alex Rybchuk earned his B.E. in Mechanical Engineering at Cooper Union in New York City, specializing in thermofluid sciences. As a PhD student in the Mechanical Engineering department, Alex researched computational fluid dynamics to model the transport and dispersion of trace gases in the lower atmosphere, with the ultimate goal of improving methane monitoring systems for natural gas infrastructure. Alex received his PhD in December 2021. 

Liz Strong

Elizabeth Strong, PhD

Elizabeth Strong earned her S.B. in engineering sciences from Harvard College. In 2019 Liz received an NSF award to support her graduate studies at CU Boulder.  Liz's her research is focused on optics May 2020 2nd author on a paper published in Optics Letters called ''Detection technique effect on rotational Doppler measurements.''  She recevied he PhD in December 2021.


Justice Calderon

Justice Calderon, MS

Justice Calderon earned his MS in Mechanical Engineering in 2021. Justice joined the Precision Laser Diagnostics Laboratory Fall of 2020 where he worked on studying calibration and stability characteristics of Dual-Comb Spectroscopy as well as optimum conditions for absorption spectroscopy measurements. In his free time, Justice enjoys playing music (guitar and flute), photography, snowboarding, exercise, and enjoying time with friends! Justice began working with Deloitte in June 2021.

Nathan Malarich

Nathan Malarich, PhD

Nate Malarich began his PhD work with Greg Rieker in 2015, after completing a B.S. in Engineering Science at Penn State. He has still only seen statues of mountain lions. Nate studies dual-comb absorption spectroscopy, in particular how to leverage the frequency comb for temperature nonuniformity sensing. In his spare time, he enjoys riding 20th-century biycles, playing ultimate, and playing jazz piano. Nate began working at NIST in Boulder in January 2021.


Amanda Makowiecki, PhD

Amanda Makowiecki received her PhD in Mechanical Engineering at the University of Colorado Boulder in December 2019. Her research utilizes wavelength modulation spectroscopy (WMS) to quantify combustion product concentrations and temperatures in thruster plumes.  Amanda began working at NOAA in Boulder in January 2020. 

Anthony Torres

Anthony Torres, MS

Anthony Torres graduated with his B.S./M.S. in Aerospace Engineering Sciences at the University of Colorado Boulder in December 2018. He worked on dual frequency spectroscopy for dynamic high pressure systems during his time at the Precision Laser Diagnostics Laboratory. He his currently an Aerospace Engineer in the Advanced Development Programs group at Blue Origin.

Torrey Hayden

Torrey Hayden, PhD

Torrey "OG Princess" Hayden earned her PhD in Mechanical Engineering from CU-Boulder in 2018 studying innovative techniques for measuring process reactions in industry applications using laser absorption spectroscopy. She is now a Spectroscopy Scientist Engineer at Zolo Technologies Inc. in Golden, CO.

Jason Christopher

Jason Christopher, PhD

Jason Christopher earned his PhD in Mechanical Engineering from CU-Boulder in 2018 studying Bayesian statistical techniques to combine laser diagnostics with fluid dynamic simulations. He is now a Professor, at the US Air Force Academy.

Paul Schroeder

Paul Schroeder, PhD

Paul Schroeder earned his PhD in Mechanical Engineering from CU-Boulder in 2017 studying laser diagnostics in harsh environments. Paul completed an NRC postdoc at NOAA in Boulder, CO and is now with General Atomics.

A teddy bear

Bennett Sodergren, MS

Bennett Sodergren earned his MS in Mechanical Engineering from CU-Boulder in 2016. He is now with Vescent Photonics, Golden, CO.

Alan Sanchez

Alan Sanchez, MS

Alan Sanchez received his MS in Aerospace Engineering Sciences at the University of Colorado Boulder in 2018. He completed his BS in the same program in May 2017. Alan is currently working at Tesla. 

Marta Ruiz Llata

Marta Ruiz-Llata, PhD - Visiting Scholar

Marta Ruiz-Llata is a Professor in the Department of Electronic Technology at the University Carlos III of Madrid (UC3M, Spain) since 2010, where she also received the degree of “Ingeniería Industrial” in 1998 and the PhD degree in Electrical, Electronics and Automation Engineering in 2005. She joined the Precision Laser Diagnostics group at CU in September 2019 for one year during her sabbatical leave from UC3M.

Her research projects have been involved with the development of optical sensors for industrial and environmental applications and the investigation of machine learning algorithms with application in instrumentation systems.  At CU her research focused on analysing measured spectral data of combustion and environmental processes acquired with optical frequency comb systems, with emphasis on the identification of large molecules characterized by complex and spread spectral signatures.