Recent Advances of Trace Gas Sensors based on Infrared
Semiconductor Lasers: Opportunities and Challenges

Frank K. Tittel
J.S. Abercrombie Professor
ECE Department
Rice Quantum Institute
Rice University

This talk will focus on the development of compact, highly sensitive and selective trace gas sensors based on diode and quantum cascade lasers for the detection, monitoring and quantification of key trace gas species. These gas sensors address important analytical instrumentation needs in atmospheric chemistry, environmental monitoring, urban and rural emission measurements, chemical analysis and industrial process control as well as medical and biomedical applications. Novel pulsed and continuous wave (cw) quantum cascade distributed feedback (QC-DFB) lasers fabricated by band structure engineering and grown by molecular beam epitaxy offer an attractive new radiation source for mid-infrared laser absorption and photoacoustic spectroscopy in the 3 to 24 μm spectral range. The most technologically developed system to date is based on intersubband transitions in InGaAs/InAlAs heterostructures. More recently, interband cascade (IC) lasers operating in the 3.3 to 4.2 μm spectral region have been demonstrated and applied to the detection of CH₄ at ∼ 3.47 μm and H₂CO at ∼ 3.53 μm.

The architecture and performance of several compact real-time semiconductor based gas sensors will be described with special emphasis on biomedical applications. To date we have detected 12 gases (CH₄, N₂O, CO₂, CO, NO, H₂O, NH₃, C₂H₄, COS, SO₂ C₂H₅OH, and C₂HO) as well as some isotopic species at the ppm to the ppt level. Various spectroscopic detection enhancement techniques have been implemented. We recently introduced a novel technique based on quartz-enhanced photoacoustic spectroscopy (QEPAS) as an effective method to perform laser based PAS where the acoustic signal build up occurs in a ultra high-Q piezoelectric quartz crystal. Several current examples of trace gas sensors used in real world applications will be described.

For additional information, contact:

Frank K. Tittel at fkt@rice.edu

This work was done in collaboration with Anatoliy A. Kosterev, Yury A. Bakhirkin, Gerard Wysocki, M. McCurdy, T. Mosley, Chad Roller, Stephen So and Robert Curl.

Specific publications relevant to this talk can be found at: http://www.ece.rice.edu/lasersci

Affiliates Meeting Agenda