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 Research Associates

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.

Research Scientists

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.

PhD Students

David Yun

David Yun earned his B.S. in Mechanical Engineering and B.M. in Piano Performance at the University of Maryland College Park (UMCP). During his time there he researched pressure and temperature optical fiber sensors, which led into engineering for a sensor startup after graduation. Afterwards, he came back to UMCP to research spatial performance in cochlear implant users. Now at CU Boulder, pursuing a PhD in Mechanical Engineering, he is excited to set the sights of dual-frequency combs on hot methane. In his spare time, he loves playing on his humble piano keyboard and getting lost in grocery stores.

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.

Scott Egbert

Scott received his bachelors and masters in mechanical engineering at Brigham Young University in Provo, Utah. He has spent two summers at Lockheed Martin aeronautics as an F-35 design engineer and another summer at Sandia in Livermore studying methane and hydrogen leaks using Raman scattering. His masters research focused on temperature measurements for gas turbine engines using infrared emission from the water vapor in the pressurized post-combustion gases. Scott started his PhD work with the Precision Laser Diagnostics Lab in the fall of 2019 and will focus on taking frequency comb laser measurements in scram jet engines. When he’s not in the lab, he loves hiking and generally being outside, especially in the mountains. He's excited to soak in as many of the 300 days of Boulder sunshine as he can. 

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 has lived his whole life. During his time there, he worked under engineers at the campus heat and power plant, and designed a polymer heat sink for his senior design project. In Fall of 2021, he will be starting his PhD at CU Boulder with the Precision Laser Diagnostics Lab. In his spare time, Augustine likes biking, fishing, and fixing his car.

Mechanical Engineering Interns

Abdul D

Abdul Dawlatzai

Abdul Dawlatzai is currently pursuing a BS in Mechanical Engineering at CU-Boulder. He is interested in mechanical design and studying heat transfer. Abdul previously worked at Sikuli Lab working on the Tactile Picture Books Project at CU-Boulder, sending over 50 tactile picture books to kids with vision impairment disabilities all over the world. He currently working on the WindCline project to study the spread of wildfires. In his free time, he enjoys playing soccer, fishing, and working on his car.


Timothy Breda

Tim Breda is currently pursuing a BS in Aerospace Engineering at CU-Boulder. Alongside his studies, he is a quality assurance assistant technician at CU-Boulder's Laboratory for Atmospheric & Space Physics. Tim is passionate about spaceflight systems & history, aerodynamics, powered flight, and heat transfer. He is currently working on the WindCline project which studies wildfire spread. In his free time, he enjoys many outdoor activities like hiking, skiing, camping, and gardening.


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.

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.

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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.