Patent ID: 8379206

Claim:
A method for the identification and quantification of one or more analyte species present in a gaseous or liquid medium utilizing a laser that outputs a laser beam and a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror, the method comprising: coupling the laser beam to the cavity via the cavity coupling mirror using mode matching optics; applying a periodic dither or modulation waveform to the optical frequency of the laser beam or to the laser itself to thereby induce modulation of the intracavity optical power; detecting, at the frequency of the applied dither or modulation waveform or harmonics thereof, a signal representing a varying pressure of the medium within the cavity; obtaining an electronic waveform signal proportional to the intracavity optical power by detecting an intensity of light emerging from a cavity mirror; calculating a ratio of a magnitude of the varying pressure signal to a magnitude of the electronic waveform signal at the detection frequency; and simultaneously sampling the varying pressure signal and the electronic waveform signal for use in reducing noise in the varying pressure signal caused by noise in the optical signal of the incident laser beam.