Optical absorption spectroscopy based gas analyzer systems and methods

A gas analyzer system for measuring a concentration of a component in a gas mixture, the system comprising:

• a resonant optical cavity containing said gas mixture and having at least two cavity mirrors, one of which is a cavity coupling mirror;
• a continuous-wave external cavity laser emitting light optically coupled to the resonant optical cavity, wherein the external cavity laser comprises a semiconductor gain medium, an output coupler, a first tunable narrow band spectral filter capable of filtering a single longitudinal mode in the laser cavity across a bandwidth of the gain medium;
• mode matching optics configured to couple the laser light to the resonant optical cavity via the cavity coupling mirror;
• a first acoustic sensor positioned within said resonant optical cavity for measuring a photoacoustic signal caused by absorption of the laser light by said gas mixture and configured to produce a data signal;
• and a processor operable to conduct the photoacoustic spectroscopy analysis of the gas mixture based on the data signal, wherein the ratio of the round-trip optical cavity length of the external cavity laser to the round-trip optical cavity length of the resonant optical cavity or its inverse value is between N−0.2 and N+0.2, where N is a positive integer number.