Mode matching method for absorption spectroscopy systems

An optical system, comprising:

• a resonant optical cavity having at least two cavity mirrors, one of which is a cavity coupling mirror, the resonant optical cavity having a plurality of optical resonance cavity modes;
• a radiation source that emits a beam of continuous wave radiation, wherein the radiation source is capable of being scanned whereby a mean optical frequency of the beam of continuous wave radiation is adjustable over a range of frequencies, and wherein the radiation source is responsive to optical feedback radiation emerging from the cavity and impinging on the radiation source;
• mode matching optics configured to couple the beam of continuous wave radiation to the cavity via the cavity coupling mirror, the mode matching optics including at least one component;
• and
• an adjustment mechanism coupled with the at least one component of the mode matching optics and/or the radiation source, the adjustment mechanism configured to adjust a relative position of the radiation source relative to the at least one component of the mode matching optics to control an amount of the optical feedback radiation emerging from the resonant optical cavity, wherein a mode fill ratio of optical feedback spectral modes is reduced relative to a maximum mode fill ratio, wherein for the maximum mode-fill ratio the beam of continuous wave radiation is coupled with a fundamental cavity spatial mode.

A gas analyzer, comprising:

• a resonant optical cavity having at least two cavity mirrors, one of which is a cavity coupling mirror, the resonant optical cavity having a plurality of optical resonance cavity modes, the resonant optical cavity configured to receive a gaseous medium including one or more analyte species;
• a radiation source that emits continuous wave radiation, wherein the radiation source is capable of being scanned whereby a mean optical frequency of the continuous wave radiation is adjustable over a range of frequencies, and wherein the radiation source is responsive to optical feedback radiation emerging from the cavity and impinging on the radiation source;
• mode matching optics configured to couple the continuous wave radiation to the resonant optical cavity via the cavity coupling mirror, the mode matching optics including at least one component;
• an adjustment mechanism coupled with the at least one component of the mode matching optics and/or the radiation source, the adjustment mechanism configured to adjust a relative position of the radiation source relative to the at least one component of the mode matching optics to control an amount of the optical feedback radiation emerging from the resonant optical cavity, wherein a mode fill ratio of the optical feedback spectral modes is reduced relative to a maximum mode fill ratio, wherein for the maximum mode-fill ratio the beam of continuous wave radiation is coupled with a fundamental cavity spatial mode;
• and
• a detector configured to measure an intensity of the intracavity optical power of radiation circulating in the resonant optical cavity and to generate a signal representing the intracavity optical power of radiation circulating in the resonant optical cavity.