System and method of providing incoherent coupling of a laser into a high finesse optical cavity

A method of performing an absorption measurement of a medium sample, the method comprising:

• coupling a laser beam having a wavelength corresponding to an absorption region of interest into a ringdown cavity comprising a chamber, an input mirror at an input end of the chamber, an output mirror at an output end of the chamber, and an optical axis that extends through a center of the input mirror and a center of the output mirror, wherein a cavity geometry of the ringdown cavity increases a re-entrant condition of the ringdown cavity relative to a conventional cavity comprised of two spherical mirrors;
• injecting a medium sample into the chamber;
• and
• detecting an intensity of light of the wavelength corresponding to the absorption region of interest that extends through the output mirror,
• wherein the cavity geometry is defined in part by a first design of the input mirror and a second design of the output mirror, wherein the first design and the second design produce a total spot overlap area on the output mirror that is less than the total spot overlap area of a cavity geometry defined by a spherical input mirror and a spherical output mirror.

A method of performing an absorption measurement of a medium sample, the method comprising:

• coupling a laser beam having a wavelength corresponding to an absorption region of interest into a ringdown cavity comprising a chamber, an input mirror at an input end of the chamber, an output mirror at an output end of the chamber, and an optical axis that extends through a center of the input mirror and a center of the output mirror, wherein a cavity geometry of the ringdown cavity increases a re-entrant condition of the ringdown cavity relative to a conventional cavity comprised of two spherical mirrors;
• injecting a medium sample into the chamber;
• and
• detecting an intensity of light of the wavelength corresponding to the absorption region of interest that extends through the output mirror,
• wherein the cavity geometry is defined in part by a cavity length that results in a highest transverse mode density for the respective designs of each of the input mirror and the output mirror.