Noemi Petra, University of Maryland, Baltimore County


Computational Modeling of Quartz-Enhanced Photoacoustic and Optothermoacoustic Sensors

Abstract: The quartz-enhanced photoacoustic spectroscopy (QEPAS) and resonant optothermoacoustic detection (ROTADE) methods are new approaches to detect optical absorption in gases. These methods are based on the conversion of optical radiation to an acoustic pressure wave or heat, which is then detected by a quartz tuning fork resonator. Sensors based on these techniques are used to detect trace gases for environmental monitoring, homeland security and medical applications. Their advantage over existing sensor systems is in their increased sensitivity and very small size. Therefore, the design of these sensors is crucial and mathematical models are needed to better understand how the sensitivity of the sensor depends on the system parameters. We present the first model that corresponds to the most basic configuration of a QEPAS sensor. By deriving analytical solutions for the partial differential equations in the model, we obtain a formula for the resulting signal strength. Simulation results show that the optimal position of the laser beam is at about 1/5 of the way from the top of the tuning fork which agrees with the experimental data. We also discuss theoretical and computational details for the mathematical models corresponding to the ROTADE sensor as well as to a more complex setup of the QEPAS system.

Collaborators: John Zweck and Susan Minkoff (University of Maryland, Baltimore County, Advisors) , Anatoliy Kosterev (Rice University)