Trace gas sensors are based on optothermal detection and use a modulated laser source and a quartz tuning fork amplifier to detect small amounts of gases for disease diagnosis via breath analysis and monitoring of atmospheric pollutants and greenhouse gases. We introduce the first mathematical model of a resonant optothermoacoustic sensor. The model is solved via the finite element method and couples heat transfer and thermoelastic deformation to determine the strength of the generated signal. Sue Minkoff is a professor of mathematical sciences and an affiliated professor in the Department of Geosciences at the University of Texas, Dallas. Her research interests include geoscience modeling and photonics. She received her Ph.D. degree in computational and applied mathematics from Rice University in 1995. From 1995 to 1997, she was an NSF industrial postdoc at the University of Texas at Austin and British Petroleum. From 1997 to 2000 she held a von Neumann fellowship in the Mathematics Department at Sandia National Laboratories in Albuquerque, NM. In 2000, she was promoted to senior member of the technical staff in the Geophysics Department at Sandia. From 2000 to 2012, she served on the faculty in the Department of Mathematics and Statistics at the University of Maryland, Baltimore County.