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Method for calibration-free scanned-wavelength modulation spectroscopy for gas sensing

United States Patent

9,939,376
April 10, 2018
View the Complete Patent at the US Patent & Trademark Office
A method of calibration-free scanned-wavelength modulation spectroscopy (WMS) absorption sensing is provided by obtaining absorption lineshape measurements of a gas sample on a sensor using 1f-normalized WMS-2f where an injection current to an injection current-tunable diode laser (TDL) is modulated at a frequency f, where a wavelength modulation and an intensity modulation of the TDL are simultaneously generated, extracting using a numerical lock-in program and a low-pass filter appropriate band-width WMS-nf (n=1, 2, . . . ) signals, where the WMS-nf signals are harmonics of the f, determining a physical property of the gas sample according to ratios of the WMS-nf signals, determining the zero-absorption background using scanned-wavelength WMS, and determining non-absorption losses using at least two of the harmonics, where a need for a non-absorption baseline measurement is removed from measurements in environments where collision broadening has blended transition linewidths, where calibration free WMS measurements without knowledge of the transition linewidth is enabled.
Hanson; Ronald K. (Cupertino, CA), Jeffries; Jay B. (Palo Alto, CA), Sun; Kai (Stanford, CA), Sur; Ritobrata (Stanford, CA), Chao; Xing (Newark, CA)
The Board of Trustees of the Leland Stanford Junior University (Palo Alto, CA)
14/ 367,420
December 19, 2012
STATEMENT OF GOVERNMENT SPONSORED SUPPORT This invention was made with Government support under contract no. DE-FE0001180 awarded by the Department of Energy. The Government has certain rights in this invention.