Southwest Sciences Inc

Phaseless Wavelength Modulation Spectroscopy

U. S. Patent 5,973,782, issued October 26, 1999

Wavelength modulation spectroscopy is a sensitive method for gas detection. A laser's wavelength is modulated at a frequency F, and the presence of an absorbing gas creates detector signals at harmonics of the modulation frequency 2F, 3F, 4F, etc. Traditionally, the amplitude of only one harmonic is detected. As a result, some information about the shape of the absorption feature can be lost. Line shape information is important for determining temperature and pressure of the gas or for exact quantitative analysis.

This invention relates a simple way to recover the information from a large number of harmonics simultaneously. The signal is demodulated using a pulse function that repeats at a nearby frequency F + df, using fairly simple and inexpensive electronics. The demodulated signal is related more directly to the true line shape of the absorbing gas.

Contact Information

Southwest Sciences, Inc.
1570 Pacheco St., Suite E-11, Santa Fe, NM 87505
tel. (505) 984-1322/ fax (505) 988-9230



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