Highly Sensitive Trace-Gas Sensing Method Based on Laser Spectroscopic Sensing of Anomalous Molecular/Atomic Dispersion

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Princeton Docket # 10-2584-1


Researchers from Princeton University and the STFC Rutherford Appleton Laboratory (UK) have developed a novel method of high sensitivity molecular detection based on detection of refractive index changes around the absorption line.  This method employs heterodyne interferometric measurement with a frequency chirped laser source and offers high enhancement of the weak dispersion signal, which enables sensitive molecular quantification.  It has been shown experimentally that this method is almost immune to laser power variation (by several orders of magnitude), or intensity noise, which is particularly attractive feature for applications under strongly changing optical transmission conditions (e.g. long path remote sensing, turbulent environments, smoke stacks, etc.). 


                Laser absorption spectroscopy (LAS) based on tunable semiconductor lasers and/or non-linear frequency conversion sources have become a widely used technique for the analysis of gas-phase chemicals.  Applications cover a broad range of sectors including industry, atmospheric monitoring and medicine.  Most of the LAS techniques rely on probing the absorption signal characteristic to a gas sample and are fundamentally limited to the measurement of small signal changes (absorption) on the top of a large background (total light intensity arriving at the detector), which may limit the dynamic range of the acquisition system.  Therefore, direct absorption measurements are strongly affected by the fluctuations of laser power reaching the detector.



Trace-gas sensing, particularly suitable for applications under strongly changing optical transmission conditions



·         High immunity to laser power variation

·         Virtually background free

·         Stabile operation



G. Wysocki, D. Weidmann. Molecular dispersion spectroscopy for chemical sensing using chirped mid infrared quantum cascade laser. Optics Express 18, 25, 26123-26140 (2010).



Gerard Wysocki is an assistant professor of Electrical Engineering at Princeton University.  His current research interests focus on the development of novel laser-based spectroscopic systems for chemical sensing in various applications including environmental monitoring, bio-medical research, and industrial process control.  Among many distinguished awards most recently Professor Wysocki has been named finalist of the Blavatnik Awards for Young Scientists (2011), received NSF Early Career Award (2010), Masao Horiba Award (2010, Japan), and NASA Tech Brief Award for Scientific or Technical Innovation (2010).

Damien Weidmann is Laser Spectroscopy team leader in the Space Science and Technology Department of the Rutherford Appleton Laboratory in UK.  Dr. Weidmann¿s research interests cover the area of high-resolution tuneable laser spectroscopy for remote and in‐situ molecular sensing as well as the development of corresponding instruments and applications.


Intellectual Property status

Patent protection is pending.

Patent Information:
For Information, Contact:
John Ritter
Princeton University
Gerard Wysocki
Damien Weidmann
gas sensing
Opto-Electronics/ELE ENG