Patent ID: 8659759

Claim:
A system for detecting one or more analyte species present in a gaseous or liquid medium, the system comprising: a laser that emits continuous wave laser light; a resonant optical cavity containing said medium and having at least two cavity mirrors, one of which is a cavity coupling mirror; mode matching optics configured to couple the laser light to the cavity via the cavity coupling mirror; a first detector configured to measure an intensity of the laser light incident on the cavity coupling mirror and to generate a first signal representing the intensity of the laser light incident on the cavity coupling mirror; a second detector configured to measure an intensity of the laser light reflected by the cavity coupling mirror and to generate a second signal representing the intensity of the laser light reflected by the cavity coupling mirror; a third detector configured to measure an intensity of the intracavity optical power of light circulating in the cavity and to generate a third signal representing the intracavity optical power of light circulating in the cavity; and an intelligence module that processes the first, second and third signals and produces a normalized output signal that is a linear function of total cavity loss and that is not sensitive to laser-cavity coupling.