Dual-Modulation Faraday Rotation Spectroscopy

Web Published:



Princeton Docket # 12-2818-1



            Researchers at Princeton University have developed a new method for simultaneously monitoring multiple paramagnetic species with high sensitivity and selectivity. A new dual modulation/demodulation process is applied to perform Faraday rotation spectroscopy (DM-FRS). The system comprises of laser source (or multiple laser sources), a shared optical configuration, and a signal acquisition and processing unit. The carrier frequency at which demodulation is performed is high and allows for effective rejection of low frequency noise in the system (e.g. laser source noise), and for suppression of system drifts originating from parasitic electromagnetic interferences. Detection limits at or close-to fundamental quantum noise limits are achievable with the disclosed system and process without adding system complexity. The technology can be effectively commercialized as stand-alone single- or multi-species sensor systems or it could be easily incorporated into any existing FRS system with little or no modification.


The method enables measurement of several paramagnetic species using a single optical configuration and photo detector. This will largely reduce the cost to build multiple sensors to target individual gas species.  The minimum detection limit to the target trace-gas can be significantly improved as compared to conventional FRS techniques.  Finally, by applying the process/device to FRS sensing, an unwanted background electro-magnetic interference (EMI) originating from the modulated magnetic field in the system can be effectively suppressed. This significantly improves long term stability of the system and allows for high accuracy measurements.


It is anticipated that this new device can be used for any application where concentrations of multiple paramagnetic species (N02, N0,02) need to be measured, such as atmospheric or air quality monitoring, breath testing for inflammation biomarkers such as asthma, or for use in a feedback loop for diesel engines for N0x detection for emission controls. 





Gerard Wysocki is an Assistant Professor of Electrical Engineering at Princeton University.  His current research interests are primarily focused on the development of laser based spectroscopic systems for chemical sensing with strong emphasis on real-world applications in atmospheric chemistry and environmental monitoring, bio-medical research and industrial process control. 


Among many distinguished awards most recently Professor Wysocki has been named finalist of the Blavatnik Award for young scientists (2011), NSF Early Career Award (2010), Masao Horiba Award (2010, Japan), and NASA Tech Brief Award for Scientific or Technical Innovation (2010).



Intellectual Property Status:


Patent protection is pending.





Michael Tyerech

Princeton University Office of Technology Licensing

(609) 258-6762



Patent Information:
For Information, Contact:
Chris Wright
Licensing Associate
Princeton University
Yin Wang
Gerard Wysocki
Opto-Electronics/ELE ENG